- DIRECTEUR du laboratoire M2P2
- Coordinateur du projet H2020 FALCON (Fluid-structure in aeronautics)
- Editeur associé du journal "Computers and Fluids"
Activités
Interaction fluide-structure
Contrôle d'écoulements
Lattice-Boltzmann
Immersed Boundary
Publications scientifiques au M2P2
2024
Q. Mao, Umberto d'Ortona, J. Favier. Hydrodynamic coupling of a cilia–mucus system in Herschel–Bulkley flows. Journal of Fluid Mechanics, 2024, 994, pp.A8. ⟨10.1017/jfm.2024.600⟩. ⟨hal-04735292⟩ Plus de détails...
The yield stress and shear thinning properties of mucus are identified as critical for ciliary coordination and mucus transport in human airways. We use here numerical simulations to explore the hydrodynamic coupling of cilia and mucus with these two properties using the Herschel–Bulkley model, in a lattice Boltzmann solver for the fluid flow. Three mucus flow regimes, i.e. a poorly organized regime, a swirly regime, and a fully unidirectional regime, are observed and analysed by parametric studies. We systematically investigate the effects of ciliary density, interaction length, Bingham number and flow index on the mucus flow regime formation. The underlying mechanism of the regime formation is analysed in detail by examining the variation of two physical quantities (polarization and integral length) and the evolution of the flow velocity, viscosity and shear-rate fields. Mucus viscosity is found to be the dominant parameter influencing the regime formation when enhancing the yield stress and shear thinning properties. The present model is able to reproduce the solid body rotation observed in experiments (Loiseau et al. , Nat. Phys. , vol. 16, 2020, pp. 1158–1164). A more precise prediction can be achieved by incorporating non-Newtonian properties into the modelling of mucus as proposed by Gsell et al. ( Sci. Rep. , vol. 10, 2020, 8405).
Q. Mao, Umberto d'Ortona, J. Favier. Hydrodynamic coupling of a cilia–mucus system in Herschel–Bulkley flows. Journal of Fluid Mechanics, 2024, 994, pp.A8. ⟨10.1017/jfm.2024.600⟩. ⟨hal-04735292⟩
Isabelle Cheylan, Tom Fringand, Jérôme Jacob, Julien Favier. Analysis of the immersed boundary method for turbulent fluid-structure interaction with Lattice Boltzmann method. Journal of Computational Physics, 2023, 492, pp.112418. ⟨10.1016/j.jcp.2023.112418⟩. ⟨hal-04543923⟩ Plus de détails...
Chenglei Wang, Simon Gsell, Umberto d'Ortona, Julien Favier. Generalized-Newtonian fluid transport by an instability-driven filament. Journal of Fluid Mechanics, 2023, 965, pp.A6. ⟨10.1017/jfm.2023.381⟩. ⟨hal-04544010⟩ Plus de détails...
Cilia are micro-scale hair-like organelles. They can exhibit self-sustained oscillations which play crucial roles in flow transport or locomotion. Recent studies have shown that these oscillations can spontaneously emerge from dynamic instability triggered by internal stresses via a Hopf bifurcation. However, the flow transport induced by an instability-driven cilium still remains unclear, especially when the fluid is non-Newtonian. This study aims at bridging these gaps. Specifically, the cilium is modelled as an elastic filament, and its internal actuation is represented by a constant follower force imposed at its tip. Three generalized Newtonian behaviours are considered, i.e. the shear-thinning, Newtonian and shear-thickening behaviours. Effects of four key factors, including the filament zero-stress shape, Reynolds number ( $Re$ ), follower-force magnitude and fluid rheology, on the filament dynamics, fluid dynamics and flow transport are explored through direct numerical simulation at $Re$ of 0.04 to 5 and through a scaling analysis at $Re \approx 0$ . The results reveal that even though it is expected that inertia vanishes at $Re \ll 1$ , inertial forces do alter the filament dynamics and deteriorate the flow transport at $Re\ge 0.04$ . Regardless of $Re$ , the flow transport can be improved when the flow is shear thinning or when the follower force increases. Furthermore, a linear stability analysis is performed, and the variation of the filament beating frequency, which is closely correlated with the filament dynamics and flow transport, can be predicted.
Chenglei Wang, Simon Gsell, Umberto d'Ortona, Julien Favier. Generalized-Newtonian fluid transport by an instability-driven filament. Journal of Fluid Mechanics, 2023, 965, pp.A6. ⟨10.1017/jfm.2023.381⟩. ⟨hal-04544010⟩
Olivier Mesdjian, Chenglei Wang, Simon Gsell, Umberto D’ortona, Julien Favier, et al.. Longitudinal to Transverse Metachronal Wave Transitions in an In Vitro Model of Ciliated Bronchial Epithelium. Physical Review Letters, 2022, 129 (3), pp.038101. ⟨10.1103/PhysRevLett.129.038101⟩. ⟨hal-03741505⟩ Plus de détails...
Olivier Mesdjian, Chenglei Wang, Simon Gsell, Umberto D’ortona, Julien Favier, et al.. Longitudinal to Transverse Metachronal Wave Transitions in an In Vitro Model of Ciliated Bronchial Epithelium. Physical Review Letters, 2022, 129 (3), pp.038101. ⟨10.1103/PhysRevLett.129.038101⟩. ⟨hal-03741505⟩
Antoine Galko, Simon Gsell, Umberto d'Ortona, Laurent Morin, Julien Favier. Pulsated Herschel-Bulkley flows in two-dimensional channels: A model for mucus clearance devices. Physical Review Fluids, 2022, 7 (5), pp.053301. ⟨10.1103/PhysRevFluids.7.053301⟩. ⟨hal-03863329⟩ Plus de détails...
Isabelle Cheylan, Julien Favier, Pierre Sagaut. Immersed boundary conditions for moving objects in turbulent flows with the lattice-Boltzmann method. Physics of Fluids, 2021, 33 (9), pp.095101. ⟨10.1063/5.0062575⟩. ⟨hal-03514710⟩ Plus de détails...
An immersed boundary method is coupled to a turbulent wall model and Large Eddy Simulation, within the Lattice-Boltzmann framework. The method is able to handle arbitrarily moving objects immersed in a high Reynolds number flow and to accurately capture the shear layer and near wall effects. We perform a thorough numerical study which validates the numerical method on a set of test-cases of increasing complexity, in order to demonstrate the application of this method to industrial conditions. The robustness and accuracy of the method are assessed first in a static laminar configuration, then in a mobile laminar case, and finally in a static and oscillating turbulent simulation. In all cases, the proposed method shows good results compared to the available data in the literature.
Isabelle Cheylan, Julien Favier, Pierre Sagaut. Immersed boundary conditions for moving objects in turbulent flows with the lattice-Boltzmann method. Physics of Fluids, 2021, 33 (9), pp.095101. ⟨10.1063/5.0062575⟩. ⟨hal-03514710⟩
Isabelle Cheylan, Julien Favier, Pierre Sagaut. Immersed boundary conditions for moving objects in turbulent flows with the lattice-Boltzmann method. Physics of Fluids, 2021, 33 (9), pp.095101. ⟨10.1063/5.0062575⟩. ⟨hal-03597108⟩ Plus de détails...
An immersed boundary method is coupled to a turbulent wall model and Large Eddy Simulation, within the Lattice-Boltzmann framework. The method is able to handle arbitrarily moving objects immersed in a high Reynolds number flow and to accurately capture the shear layer and near wall effects. We perform a thorough numerical study which validates the numerical method on a set of test-cases of increasing complexity, in order to demonstrate the application of this method to industrial conditions. The robustness and accuracy of the method are assessed first in a static laminar configuration, then in a mobile laminar case, and finally in a static and oscillating turbulent simulation. In all cases, the proposed method shows good results compared to the available data in the literature.
Isabelle Cheylan, Julien Favier, Pierre Sagaut. Immersed boundary conditions for moving objects in turbulent flows with the lattice-Boltzmann method. Physics of Fluids, 2021, 33 (9), pp.095101. ⟨10.1063/5.0062575⟩. ⟨hal-03597108⟩
H. Yoo, M. Bahlali, Julien Favier, Pierre Sagaut. A hybrid recursive regularized lattice Boltzmann model with overset grids for rotating geometries. Physics of Fluids, 2021, 33 (5), pp.057113. ⟨10.1063/5.0045524⟩. ⟨hal-03326134⟩ Plus de détails...
Simulating rotating geometries in fluid flows for industrial applications remains a challenging task for general fluid solvers and in particular for the lattice Boltzmann method (LBM) due to inherent stability and accuracy problems. This work proposes an original method based on the widely used overset grids (or Chimera grids) while being integrated with a recent and optimized LBM collision operator, the hybrid recursive regularized model (HRR). The overset grids are used to actualize the rotating geometries where both the rotating and fixed meshes exist simultaneously. In the rotating mesh, the fictitious forces generated from its non-inertial rotating reference frame are taken into account by using a second order discrete forcing term. The fixed and rotating grids communicate with each other through the interpolation of the macroscopic variables. Meanwhile, the HRR collision model is selected to enhance the stability and accuracy properties of the LBM simulations by filtering out redundant higher order non-equilibrium tensors. The robustness of the overset HRR algorithm is assessed on different configurations, undergoing mid-to-high Reynolds number flows, and the method successfully demonstrates its robustness while exhibiting the second order accuracy.
H. Yoo, M. Bahlali, Julien Favier, Pierre Sagaut. A hybrid recursive regularized lattice Boltzmann model with overset grids for rotating geometries. Physics of Fluids, 2021, 33 (5), pp.057113. ⟨10.1063/5.0045524⟩. ⟨hal-03326134⟩
M. Bahlali, H. Yoo, Julien Favier, Pierre Sagaut. A lattice Boltzmann direct coupling overset approach for the moving boundary problem. Physics of Fluids, 2021, 33 (5), pp.053607. ⟨10.1063/5.0044994⟩. ⟨hal-03326151⟩ Plus de détails...
We propose a new direct coupling scheme based on the overset technique to tackle moving boundary problems within the lattice Boltzmann framework. The scheme is based on the interpolation of distribution functions rather than moments, that is, macroscopic variables, and includes an additional hypothesis ensuring mass and momentum conservation at the interface nodes between fixed and moving grids. The method is assessed considering four test cases and considering both the vortical and the acoustic fields. It is shown that the direct coupling method results are in very good agreement with reference results on a configuration without any moving subdomain. Moreover, it is demonstrated that the direct coupling method provides an improvement of the accuracy of the lattice Boltzmann overset algorithm for aeroacoustics. In particular, a convected vortex test case is studied and reveals that the direct coupling approach leads to a better ability to conserve the vortex structure over time, as well as a reduction in spurious acoustic distorsions at the fixed/moving interface.
M. Bahlali, H. Yoo, Julien Favier, Pierre Sagaut. A lattice Boltzmann direct coupling overset approach for the moving boundary problem. Physics of Fluids, 2021, 33 (5), pp.053607. ⟨10.1063/5.0044994⟩. ⟨hal-03326151⟩
H. Yoo, M. Bahlali, Julien Favier, Pierre Sagaut. A hybrid recursive regularized lattice Boltzmann model with overset grids for rotating geometries. Physics of Fluids, 2021, 33 (5), pp.057113. ⟨10.1063/5.0045524⟩. ⟨hal-03597721⟩ Plus de détails...
Simulating rotating geometries in fluid flows for industrial applications remains a challenging task for general fluid solvers and in particular for the lattice Boltzmann method (LBM) due to inherent stability and accuracy problems. This work proposes an original method based on the widely used overset grids (or Chimera grids) while being integrated with a recent and optimized LBM collision operator, the hybrid recursive regularized model (HRR). The overset grids are used to actualize the rotating geometries where both the rotating and fixed meshes exist simultaneously. In the rotating mesh, the fictitious forces generated from its non-inertial rotating reference frame are taken into account by using a second order discrete forcing term. The fixed and rotating grids communicate with each other through the interpolation of the macroscopic variables. Meanwhile, the HRR collision model is selected to enhance the stability and accuracy properties of the LBM simulations by filtering out redundant higher order non-equilibrium tensors. The robustness of the overset HRR algorithm is assessed on different configurations, undergoing mid-to-high Reynolds number flows, and the method successfully demonstrates its robustness while exhibiting the second order accuracy.
H. Yoo, M. Bahlali, Julien Favier, Pierre Sagaut. A hybrid recursive regularized lattice Boltzmann model with overset grids for rotating geometries. Physics of Fluids, 2021, 33 (5), pp.057113. ⟨10.1063/5.0045524⟩. ⟨hal-03597721⟩
The boundary slip error resulting from the interpolation/spreading non-reciprocity of the direct-forcing immersedboundary method is analyzed based on a simple and generic theoretical framework. In explicit implementations, the slip error scales with the Courant number, as predicted by the analysis and confirmed by lattice-Boltzmann simulation results. Using an analytical approximation of the non-reciprocity error, the immersed-boundary force can be corrected in order to prevent boundary slip and flow penetration. This a priori correction leads to a major improvement of the no-slip condition while avoiding any additional computational time or implementation effort.
Simon Gsell, Julien Favier. Direct-forcing immersed-boundary method: a simple correction preventing boundary slip error. Journal of Computational Physics, 2021, 435, pp.110265. ⟨10.1016/j.jcp.2021.110265⟩. ⟨hal-03425864⟩
Simon Gsell, Umberto d'Ortona, Julien Favier. Lattice-Boltzmann simulation of creeping generalized Newtonian flows: theory and guidelines. Journal of Computational Physics, 2021, 429, pp.109943. ⟨10.1016/j.jcp.2020.109943⟩. ⟨hal-03166492⟩ Plus de détails...
The accuracy of the lattice-Boltzmann (LB) method is related to the relaxation time controlling the flow viscosity. In particular, it is often recommended to avoid large fluid viscosities in order to satisfy the low-Knudsen-number assumption that is essential to recover hydrodynamic behavior at the macroscopic scale, which may in principle limit the possibility of simulating creeping flows and non-Newtonian flows involving important viscosity variations. Here it is shown, based on the continuous Boltzmann equations, that a two-relaxation-time (TRT) model can however recover the steady Navier-Stokes equations without any restriction on the fluid viscosity, provided that the Knudsen number is redefined as a function of both relaxation times. This effective Knudsen number is closely related to the previously-described parameter controlling numerical errors of the TRT model, providing a consistent theory at both the discrete and continuous levels. To simulate incompressible flows, the viscous incompressibility condition M a 2 /Re 1 also needs to be satisfied, where M a and Re are the Mach and Reynolds numbers. This concept is extended by defining a local incompressibility factor, allowing one to locally control the accuracy of the simulation for flows involving varying viscosities. These theoretical arguments are illustrated based on numerical simulations of the two-dimensional flow past a square cylinder. In the case of a Newtonian flow, the viscosity independence is confirmed for relaxation times up to 10 4 , and the ratio M a 2 /Re = 0.1 is small enough to ensure reliable incompressible simulations. The Herschel-Bulkley model is employed to introduce shear-dependent viscosities in the flow. The proposed numerical strategy allows to achieve major viscosity variations, avoiding the implementation of artificial viscosity cutoff in high-viscosity regions. Highly non-linear flows are simulated over ranges of the Bingham number Bn ∈ [1, 1000] and flow index n ∈ [0.2, 1.8], and successfully compared to prior numerical works based on Navier-Stokes solvers. This work provides a general framework to simulate complex creeping flows, as encountered in many biological and industrial systems, using the lattice-Boltzmann method.
Simon Gsell, Umberto d'Ortona, Julien Favier. Lattice-Boltzmann simulation of creeping generalized Newtonian flows: theory and guidelines. Journal of Computational Physics, 2021, 429, pp.109943. ⟨10.1016/j.jcp.2020.109943⟩. ⟨hal-03166492⟩
Etienne Loiseau, Simon Gsell, Aude Nommick, Charline Jomard, Delphine Gras, et al.. Active mucus–cilia hydrodynamic coupling drives self-organization of human bronchial epithelium. Nature Physics, 2020, ⟨10.1038/s41567-020-0980-z⟩. ⟨hal-02914172⟩ Plus de détails...
The respiratory tract is protected by mucus, a complex fluid transported along the epithelial surface by the coordinated beating of millions of microscopic cilia, hence the name of mucociliary clearance. Its impairment is associated with all severe chronic respiratory diseases. Yet, the relationship between ciliary density and the spatial scale of mucus transport, as well as the mechanisms that drive ciliary-beat orientations are much debated. Here, we show on polarized human bronchial epithelia that mucus swirls and circular orientational order of the underlying ciliary beats emerge and grow during ciliogenesis, until a macroscopic mucus transport is achieved for physiological ciliary densities. By establishing that the macroscopic ciliary-beat order is lost and recovered by removing and adding mucus, respectively, we demonstrate that cilia–mucus hydrodynamic interactions govern the collective dynamics of ciliary-beat directions. We propose a two-dimensional model that predicts a phase diagram of mucus transport in accordance with the experiments. This paves the way to a predictive in silico modelling of bronchial mucus transport in health and disease.
Etienne Loiseau, Simon Gsell, Aude Nommick, Charline Jomard, Delphine Gras, et al.. Active mucus–cilia hydrodynamic coupling drives self-organization of human bronchial epithelium. Nature Physics, 2020, ⟨10.1038/s41567-020-0980-z⟩. ⟨hal-02914172⟩
Simon Gsell, Etienne Loiseau, Umberto D’ortona, Annie Viallat, Julien Favier. Hydrodynamic model of directional ciliary-beat organization in human airways. Scientific Reports, 2020, 10 (8405), ⟨10.1038/s41598-020-64695-w⟩. ⟨hal-02614711⟩ Plus de détails...
In the lung, the airway surface is protected by mucus, whose transport and evacuation is ensured through active ciliary beating. the mechanisms governing the long-range directional organization of ciliary beats, required for effective mucus transport, are much debated. Here, we experimentally show on human bronchial epithelium reconstituted in-vitro that the dynamics of ciliary-beat orientation is closely connected to hydrodynamic effects. To examine the fundamental mechanisms of this self-organization process, we build a two-dimensional model in which the hydrodynamic coupling between cilia is provided by a streamwise-alignment rule governing the local orientation of the ciliary forcing. The model reproduces the emergence of the mucus swirls observed in the experiments. The predicted swirl sizes, which scale with the ciliary density and mucus viscosity, are in agreement with in-vitro measurements. A transition from the swirly regime to a long-range unidirectional mucus flow allowing effective clearance occurs at high ciliary density and high mucus viscosity. In the latter case, the mucus flow tends to spontaneously align with the bronchus axis due to hydrodynamic effects.
Simon Gsell, Etienne Loiseau, Umberto D’ortona, Annie Viallat, Julien Favier. Hydrodynamic model of directional ciliary-beat organization in human airways. Scientific Reports, 2020, 10 (8405), ⟨10.1038/s41598-020-64695-w⟩. ⟨hal-02614711⟩
The lattice Boltzmann method often involves small numerical time steps due to the acoustic scaling (i.e., scaling between time step and grid size) inherent to the method. In this work, a second-order dual-time-stepping lattice Boltzmann method is proposed in order to avoid any time-step restriction. The implementation of the dual time stepping is based on an external source in the lattice Boltzmann equation, related to the time derivatives of the macroscopic flow quantities. Each time step is treated as a pseudosteady problem. The convergence rate of the steady lattice Boltzmann solver is improved by implementing a multigrid method. The developed solver is based on a two-relaxation time model coupled to an immersed-boundary method. The reliability of the method is demonstrated for steady and unsteady laminar flows past a circular cylinder, either fixed or towed in the computational domain. In the steady-flow case, the multigrid method drastically increases the convergence rate of the lattice Boltzmann method. The dual-time-stepping method is able to accurately reproduce the unsteady flows. The physical time step can be freely adjusted; its effect on the simulation cost is linear, while its impact on the accuracy follows a second-order trend. Two major advantages arise from this feature. (i) Simulation speed-up can be achieved by increasing the time step while conserving a reasonable accuracy. A speed-up of 4 is achieved for the unsteady flow past a fixed cylinder, and higher speed-ups are expected for configurations involving slower flow variations. Significant additional speed-up can also be achieved by accelerating transients. (ii) The choice of the time step allows us to alter the range of simulated timescales. In particular, increasing the time step results in the filtering of undesired pressure waves induced by sharp geometries or rapid temporal variations, without altering the main flow dynamics. These features may be critical to improve the efficiency and range of applicability of the lattice Boltzmann method.
Simon Gsell, Umberto d'Ortona, Julien Favier. Multigrid dual-time-stepping lattice Boltzmann method. Physical Review E , 2020, 101 (2), ⟨10.1103/PhysRevE.101.023309⟩. ⟨hal-02573156⟩
The coordinated beating of epithelial cilia in human lungs is a fascinating problem from the hydrodynamics perspective. The phase lag between neighboring cilia is able to generate collective cilia motions, known as metachronal waves. Different kinds of waves can occur, antiplectic or symplectic, depending on the direction of the wave with respect to the flow direction. It is shown here, using a coupled lattice Boltzmann-immersed boundary solver, that the key mechanism responsible for their transport efficiency is a blowing-suction effect that displaces the interface between the periciliary liquid and the mucus phase. The contribution of this mechanism on the average flow generated by the cilia is compared to the contribution of the lubrication effect. The results reveal that the interface displacement is the main mechanism responsible for the better efficiency of antiplectic metachronal waves over symplectic ones to transport bronchial mucus. The conclusions drawn here can be extended to any two-layer fluid configuration having different viscosities, and put into motion by cilia-shaped or comb-plate structures, having a back-and-forth motion with phase lags.
Sylvain Chateau, Julien Favier, Sébastien Poncet, Umberto d'Ortona. Why antiplectic metachronal cilia waves are optimal to transport bronchial mucus. Physical Review E , 2019, 100 (4), pp.042405. ⟨10.1103/PhysRevE.100.042405⟩. ⟨hal-02468006⟩
Simon Gsell, Umberto d'Ortona, Julien Favier. Explicit and viscosity-independent immersed-boundary scheme for the lattice Boltzmann method. Physical Review E , 2019, 100 (3), ⟨10.1103/PhysRevE.100.033306⟩. ⟨hal-02339475⟩ Plus de détails...
Viscosity independence of lattice-Boltzmann methods is a crucial issue to ensure the physical relevancy of the predicted macroscopic flows over large ranges of physical parameters. The immersed-boundary (IB) method, a powerful tool that allows one to immerse arbitrary-shaped, moving, and deformable bodies in the flow, suffers from a boundary-slip error that increases as a function of the fluid viscosity, substantially limiting its range of application. In addition, low fluid viscosities may result in spurious oscillations of the macroscopic quantities in the vicinity of the immersed boundary. In this work, it is shown mathematically that the standard IB method is indeed not able to reproduce the scaling properties of the macroscopic solution, leading to a viscosity-related error on the computed IB force. The analysis allows us to propose a simple correction of the IB scheme that is local, straightforward and does not involve additional computational time. The derived method is implemented in a two-relaxation-time D2Q9 lattice-Boltzmann solver, applied to several physical configurations, namely, the Poiseuille flow, the flow around a cylinder towed in still fluid, and the flow around a cylinder oscillating in still fluid, and compared to a noncorrected immersed-boundary method. The proposed correction leads to a major improvement of the viscosity independence of the solver over a wide range of relaxation times (from 0.5001 to 50), including the correction of the boundary-slip error and the suppression of the spurious oscillations. This improvement may considerably extend the range of application of the IB lattice-Boltzmann method, in particular providing a robust tool for the numerical analysis of physical problems involving fluids of varying viscosity interacting with solid geometries.
Simon Gsell, Umberto d'Ortona, Julien Favier. Explicit and viscosity-independent immersed-boundary scheme for the lattice Boltzmann method. Physical Review E , 2019, 100 (3), ⟨10.1103/PhysRevE.100.033306⟩. ⟨hal-02339475⟩
Zhe Li, Julien Favier. Fluid-Structure Interaction Using Lattice Boltzmann Method Coupled With Finite Element Method. Analysis and Applications of Lattice Boltzmann Simulations, 2018. ⟨hal-02887325⟩ Plus de détails...
Zhe Li, Julien Favier. Fluid-Structure Interaction Using Lattice Boltzmann Method Coupled With Finite Element Method. Analysis and Applications of Lattice Boltzmann Simulations, 2018. ⟨hal-02887325⟩
Sylvain Chateau, Umberto d'Ortona, Sébastien Poncet, Julien Favier. Transport and Mixing Induced by Beating Cilia in Human Airways. Frontiers in Physiology, 2018, 9, pp.161. ⟨10.3389/fphys.2018.00161⟩. ⟨hal-01875672⟩ Plus de détails...
The fluid transport and mixing induced by beating cilia, present in the bronchial airways, are studied using a coupled lattice Boltzmann-Immersed Boundary solver. This solver allows the simulation of both single and multi-component fluid flows around moving solid boundaries. The cilia aremodeled by a set of Lagrangian points, and Immersed Boundary forces are computed onto these points in order to ensure the no-slip velocity conditions between the cilia and the fluids. The cilia are immersed in a two-layer environment: the periciliary layer (PCL) and the mucus above it. The motion of the cilia is prescribed, as well as the phase lag between two cilia in order to obtain a typical collective motion of cilia, known as metachronal waves. The results obtained from a parametric study show that antiplectic metachronal waves are the most efficient regarding the fluid transport. A specific value of phase lag, which generates the larger mucus transport, is identified. The mixing is studied using several populations of tracers initially seeded into the pericilary liquid, in the mucus just above the PCL-mucus interface, and in the mucus far away from the interface. We observe that each zone exhibits different chaotic mixing properties. The larger mixing is obtained in the PCL layer where only a few beating cycles of the cilia are required to obtain a full mixing, while above the interface, the mixing is weaker and takes more time. Almost no mixing is observed within the mucus, and almost all the tracers do not penetrate the PCL layer. Lyapunov exponents are also computed for specific locations to assess how the mixing is performed locally. Two time scales are introduced to allow a comparison between mixing induced by fluid advection and by molecular diffusion. These results are relevant in the context of respiratory flows to investigate the transport of drugs for patients suffering from chronic respiratory diseases.
Sylvain Chateau, Umberto d'Ortona, Sébastien Poncet, Julien Favier. Transport and Mixing Induced by Beating Cilia in Human Airways. Frontiers in Physiology, 2018, 9, pp.161. ⟨10.3389/fphys.2018.00161⟩. ⟨hal-01875672⟩
Olivier Lafforgue, Isabelle Seyssiecq, Sébastien Poncet, Julien Favier. Rheological properties of synthetic mucus for airway clearance. Journal of Biomedical Materials Research Part A, 2018, 106 (2), pp.386 - 396. ⟨10.1002/jbm.a.36251⟩. ⟨hal-01678912⟩ Plus de détails...
In this work, a complete rheological characterization of bronchial mucus simulants based on the composition proposed by Zahm et al. [1] is presented. Dynamic Small Amplitude Oscillatory Shear (SAOS) experiments, Steady State (SS) flow measurements and three Intervals Thixotropy Tests (3ITT), are carried out to investigate the global rheological complexities of simulants (viscoelasticity, viscoplasticity, shear-thinning and thixotropy) as a function of scleroglucan concentrations (0.5 to 2wt%) and under temperatures of 20 and 37 °C. SAOS measurements show that the limit of the linear viscoelastic range as well as the elasticity both increase with increasing sclerogucan concentrations. Depending on the sollicitation frequency, the 0.5wt% gel response is either liquid-like or solid-like, whereas more concentrated gels show a solid-like response over the whole frequency range. The temperature dependence of gels response is negligible in the 20-37°C range. The Herschel-Bulkley (HB) model is chosen to fit the SS flow curve of simulants. The evolution of HB parameters versus polymer concentration show that both shear-thinning and viscoplasticity increase with increasing concentrations. 3ITTs allow calculation of recovery thixotropic times after shearings at 100s-1 or 1.6s-1. Empiric correlations are proposed to quantify the effect of polymer concentration on rheological parameters of mucus simulants.
Olivier Lafforgue, Isabelle Seyssiecq, Sébastien Poncet, Julien Favier. Rheological properties of synthetic mucus for airway clearance. Journal of Biomedical Materials Research Part A, 2018, 106 (2), pp.386 - 396. ⟨10.1002/jbm.a.36251⟩. ⟨hal-01678912⟩
Journal: Journal of Biomedical Materials Research Part A
H. Riahi, Marcello Meldi, Julien Favier, Eric Serre, Eric Goncalves da Silva. A pressure-corrected Immersed Boundary Method for the numerical simulation of compressible flows. Journal of Computational Physics, 2018, 374, pp.361-383. ⟨10.1016/j.jcp.2018.07.033⟩. ⟨hal-01859760⟩ Plus de détails...
The development of an improved new IBM method is proposed in the present article. This method roots in efficient proposals developed for the simulation of incompressible flows, and it is expanded for compressible configurations. The main feature of this model is the integration of a pressure-based correction of the IBM forcing which is analytically derived from the set of dynamic equations. The resulting IBM method has been integrated in various flow solvers available in the CFD platform OpenFOAM. A rigorous validation has been performed considering different test cases of increasing complexity. The results have been compared with a large number of references available in the literature of experimental and numerical nature. This analysis highlights numerous favorable characteristics of the IBM method, such as precision, flexibility and computational cost efficiency.
H. Riahi, Marcello Meldi, Julien Favier, Eric Serre, Eric Goncalves da Silva. A pressure-corrected Immersed Boundary Method for the numerical simulation of compressible flows. Journal of Computational Physics, 2018, 374, pp.361-383. ⟨10.1016/j.jcp.2018.07.033⟩. ⟨hal-01859760⟩
A novel implicit immersed boundary method of high accuracy and efficiency is presented for the simulation of incompressible viscous flow over complex stationary or moving solid boundaries. A boundary force is often introduced in many immersed boundary methods to mimic the presence of solid boundary, such that the overall simulation can be performed on a simple Cartesian grid. The current method inherits this idea and considers the boundary force as a Lagrange multiplier to enforce the no-slip constraint at the solid boundary, instead of applying constitutional relations for rigid bodies. Hence excessive constraint on the time step is circumvented, and the time step only depends on the discretization of fluid Navier-Stokes equations, like the CFL condition in present work. To determine the boundary force, an additional moving force equation is derived. The dimension of this derived system is proportional to the number of Lagrangian points describing the solid boundaries, which makes the method very suitable for moving boundary problems since the time for matrix update and system solving is not significant. The force coefficient matrix is made symmetric and positive definite so that the conjugate gradient method can solve the system quickly. The proposed immersed boundary method is incorporated into the fluid solver with a second-order accurate projection method as a plug-in. The overall scheme is handled under an efficient fractional step framework, namely, prediction, forcing, and projection. Various simulations are performed to validate current method, and the results compare well with previous experimental and numerical studies.
Shang-Gui Cai, Abdellatif Ouahsine, Julien Favier, Yannick Hoarau. Moving immersed boundary method. International Journal for Numerical Methods in Fluids, 2017, 85 (5), pp.288 - 323. ⟨10.1002/fld.4382⟩. ⟨hal-01592822⟩
Journal: International Journal for Numerical Methods in Fluids
Olivier Lafforgue, N. Bouguerra, Sebastien Poncet, Isabelle Seyssiecq, Julien Favier, et al.. Thermo-physical properties of synthetic mucus for the study of airway clearance. Journal of Biomedical Materials Research Part A, 2017, 105 (11), pp.3025-3033 ⟨10.1002/jbm.a.36161⟩. ⟨hal-01596484⟩ Plus de détails...
In this article, dynamic viscosity, surface tension, density, heat capacity and thermal conductivity, of a bronchial mucus simulant proposed by Zahm et al., Eur Respir J 1991; 4: 311–315 were experiementally determined. This simulant is mainly composed of a galactomannan gum and a scleroglucan. It was shown that thermophysical properties of synthetic mucus are dependant of scleroglucan concentrations. More importantly and for some scleroglucan concentrations, the syntetic mucus, exhibits, somehow, comparable thermophysical properties to real bronchial mucus. An insight on the microstructure of this simulant is proposed and the different properties enounced previously have been measured for various scleroglucan concentrations and over a certain range of operating temperatures. This synthetic mucus is found to mimic well the rheological behavior and the surface tension of real mucus for different pathologies. Density and thermal properties have been measured for the first time.
Olivier Lafforgue, N. Bouguerra, Sebastien Poncet, Isabelle Seyssiecq, Julien Favier, et al.. Thermo-physical properties of synthetic mucus for the study of airway clearance. Journal of Biomedical Materials Research Part A, 2017, 105 (11), pp.3025-3033 ⟨10.1002/jbm.a.36161⟩. ⟨hal-01596484⟩
Journal: Journal of Biomedical Materials Research Part A
Sylvain Chateau, Julien Favier, Umberto D’ortona, Sebastien Poncet. Transport efficiency of metachronal waves in 3D cilium arrays immersed in a two-phase flow. Journal of Fluid Mechanics, 2017, 824, pp.931 - 961. ⟨10.1017/jfm.2017.352⟩. ⟨hal-01592834⟩ Plus de détails...
This work reports the formation and characterization of antipleptic and symplectic metachronal waves in 3D cilium arrays immersed in a two-fluid environment, with a viscosity ratio of 20. A coupled lattice Boltzmann-immersed-boundary solver is used. The periciliary layer is confined between the epithelial surface and the mucus. Its thickness is chosen such that the tips of the cilia can penetrate the mucus. A purely hydrodynamical feedback of the fluid is taken into account and a coupling parameter alpha is introduced, which allows tuning of both the direction of the wave propagation and the strength of the fluid feedback. A comparative study of both antipleptic and symplectic waves, mapping a cilium interspacing ranging from 1.67 up to 5 cilium lengths, is performed by imposing metachrony. Antipleptic waves are found to systematically outperform symplectic waves. They are shown to be more efficient for transporting and mixing the fluids, while spending less energy than symplectic, random or synchronized motions.
Sylvain Chateau, Julien Favier, Umberto D’ortona, Sebastien Poncet. Transport efficiency of metachronal waves in 3D cilium arrays immersed in a two-phase flow. Journal of Fluid Mechanics, 2017, 824, pp.931 - 961. ⟨10.1017/jfm.2017.352⟩. ⟨hal-01592834⟩
Eddy Constant, Julien Favier, Marcello Meldi, Philippe Meliga, Eric Serre. An immersed boundary method in OpenFOAM : Verification and validation. Computers and Fluids, 2017, 157, pp.55 - 72. ⟨10.1016/j.compfluid.2017.08.001⟩. ⟨hal-01591562⟩ Plus de détails...
The present work proposes a modified Pressure-Implicit Split-Operator (PISO) solver integrating the recent Immersed Boundary Method (IBM) proposed by Pinelli et al. [1] in order to perform reliable simulations of incompressible flows around bluff bodies using the open source toolbox OpenFOAM version 2.2 (ESI-OpenCFD [2]). The (IBM) allows for a precise representation of fixed and moving solid obstacles embedded in the physical domain, using uniform or stretched Cartesian meshes. Owing to this feature, the maximum level of accuracy and scalability of the numerical solvers can be systematically achieved. An iterative scheme based on sub-iterations between (IBM) and pressure correction has been implemented in the native (PISO) solver of OpenFOAM. This allows one to use fast optimized Poisson solvers while satisfying simultaneously the divergence-free flow state and the no-slip condition at the body surface. To compute the divergence of the momentum equation (in the PISO loop) and the interpolation of the fluxes, we propose an hybrid calculation with an analytical resolution (using the kernel function equation) of the quantities involving the force term (singular quantities). A careful and original verification study has been carried out which allows to estimate three different errors related to the discretization and to the (IBM). Various 2D and 3D well-documented test cases of academic flows around fixed or moving cylinders have been simulated and carefully validated against existing data from the literature in a large range of Reynolds numbers, Re = 30 − 3900 and in the frame of DNS and DDES OpenFOAM native models.
Eddy Constant, Julien Favier, Marcello Meldi, Philippe Meliga, Eric Serre. An immersed boundary method in OpenFOAM : Verification and validation. Computers and Fluids, 2017, 157, pp.55 - 72. ⟨10.1016/j.compfluid.2017.08.001⟩. ⟨hal-01591562⟩
Julien Favier, Cuicui Li, Laura Kamps, Alistair Revell, Joseph O’connor, et al.. The PELskin project—part I: fluid–structure interaction for a row of flexible flaps: a reference study in oscillating channel flow. Meccanica, 2017, 52 (8), pp.1767 - 1780. ⟨10.1007/s11012-016-0521-0⟩. ⟨hal-01592866⟩ Plus de détails...
Previous studies of flexible flaps attached to the aft part of a cylinder have demonstrated a favourable effect on the drag and lift force fluctuation. This observation is thought to be linked to the excitation of travelling waves along the flaps and as a consequence of that, periodic shedding of the von Karman vortices is altered in phase. A more general case of such interaction is studied herein for a limited row of flaps in an oscillating flow; representative of the cylinder case since the transversal flow in the wake-region shows oscillating character. This reference case is chosen to qualify recently developed numerical methods for the simulation of fluid-structure interaction in the context of the EU funded 'PELskin' project. The simulation of the two-way coupled dynamics of the flexible elements is achieved via a structure model for the flap motion, which was implemented and coupled to two different fluid solvers via the immersed boundary method. The results show the waving behaviour observed at the tips of the flexible elements in interaction with the fluid flow and the formation of vortices in the gaps between the flaps. In addition, formation of vortices upstream of the leading and downstream of the trailing flap is seen, which interact with the formation of the shear-layer on top of the row. This leads to a phase shift in the wave-type motion along the row that resembles the observation in the cylinder case.
Julien Favier, Cuicui Li, Laura Kamps, Alistair Revell, Joseph O’connor, et al.. The PELskin project—part I: fluid–structure interaction for a row of flexible flaps: a reference study in oscillating channel flow. Meccanica, 2017, 52 (8), pp.1767 - 1780. ⟨10.1007/s11012-016-0521-0⟩. ⟨hal-01592866⟩
Alistair Revell, Joseph O’connor, Abhishek Sarkar, Cuicui Li, Julien Favier, et al.. The PELskin project: part II—investigating the physical coupling between flexible filaments in an oscillating flow. Meccanica, 2017, 52 (8), pp.1781 - 1795. ⟨10.1007/s11012-016-0525-9⟩. ⟨hal-01592870⟩ Plus de détails...
The fluid-structure interaction mechanisms of a coating composed of flexible flaps immersed in a periodically oscillating channel flow is here studied by means of numerical simulation, employing the Euler-Bernoulli equations to account for the flexibility of the structures. A set of passively actuated flaps have previously been demonstrated to deliver favourable aerodynamic impact when attached to a bluff body undergoing periodic vortex shedding. As such, the present configuration is identified to provide a useful test-bed to better understand this mechanism, thought to be linked to experimentally observed travelling waves. Having previously validated and elucidated the flow mechanism in Paper 1 of this series, we hereby undertake a more detailed analysis of spectra obtained for different natural frequency of structures and different configurations, in order to better characterize the mechanisms involved in the organized motion of the structures. Herein, this wave-like behaviour, observed at the tips of flexible structures via interaction with the fluid flow, is characterized by examining the time history of the filaments motion and the corresponding effects on the fluid flow, in terms of dynamics and frequency of the fluid velocity. Results indicate that the wave motion behaviour is associated with the formation of vortices in the gaps between the flaps, which itself are a function of the structural resistance to the cross flow. In addition, formation of vortices upstream of the leading and downstream of the trailing flap is seen, which interact with the formation of the shear-layer on top of the row. This leads to a phase shift in the wave-type motion along the row that resembles the observation in the cylinder case.
Alistair Revell, Joseph O’connor, Abhishek Sarkar, Cuicui Li, Julien Favier, et al.. The PELskin project: part II—investigating the physical coupling between flexible filaments in an oscillating flow. Meccanica, 2017, 52 (8), pp.1781 - 1795. ⟨10.1007/s11012-016-0525-9⟩. ⟨hal-01592870⟩
A novel immersed boundary method is introduced for simulating the fluid-structure interaction problem. Unlike the body-conforming mesh method which imposes the no-slip boundary conditions directly on the immersed interface, the immersed boundary method adopts a boundary force for the presence of the immersed solid. Therefore, the fluid is simply simulated on a fixed Cartesian mesh irrespective the movement of the immersed solid, which circumvents the mesh quality issue that frequently happens in the body-conforming mesh method. To enforce the correct boundary condition, we derive an additional moving force equation. This additional equation is integrated into a second order accurate fractional step method and solved with the conjugate gradient method. The proposed method is validated with several one-way fluid-structure interaction examples.
Shang-Gui Cai, Abdellatif Ouahsine, Julien Favier, Yannick Hoarau. Implicit immersed boundary method for fluid-structure interaction. La Houille Blanche - Revue internationale de l'eau, 2017, 1/2017 (1), pp.33 - 36. ⟨10.1051/lhb/2017005⟩. ⟨hal-01592851⟩
Journal: La Houille Blanche - Revue internationale de l'eau
Zhe Li, Julien Favier. A non-staggered coupling of finite element and lattice Boltzmann methods via an immersed boundary scheme for fluid-structure interaction. Computers and Fluids, 2017, 143, pp.90 - 102. ⟨10.1016/j.compfluid.2016.11.008⟩. ⟨hal-01403915⟩ Plus de détails...
The paper presents a numerical framework for the coupling of finite element and lattice Boltzmann methods for transient problems involving fluid-structure interaction. The solid structure is discretized with the finite element method and integrated in time with the explicit Newmark scheme. The lattice Boltzmann method is used for the simulation of single-component weakly-compressible fluid flows. The two numerical methods are coupled via a direct-forcing immersed boundary method in a non-staggered way. Without subiteration within each time-step, the proposed method can ensure the synchronization of the time integrations, and thus the strong coupling of both subdomains by resolving a linear system of coupling equations at each time-step. Hence the energy transfer at the fluid-solid interface is correct, i.e. neither energy dissipation nor energy injection will occur at the interface, which can retain the numerical stability. A well-known fluid-structure interaction test case is adopted to validate the proposed coupling method. It is shown that the stability of the used numerical schemes can be preserved and a good agreement is found with the reference results.
Zhe Li, Julien Favier. A non-staggered coupling of finite element and lattice Boltzmann methods via an immersed boundary scheme for fluid-structure interaction. Computers and Fluids, 2017, 143, pp.90 - 102. ⟨10.1016/j.compfluid.2016.11.008⟩. ⟨hal-01403915⟩
Marianna Pepona, Julien Favier. A coupled Immersed Boundary – Lattice Boltzmann method for incompressible flows through moving porous media A coupled Immersed Boundary -Lattice Boltzmann method for incompressible flows through moving porous media. Journal of Computational Physics, 2016, 321, pp.1170-1184. ⟨10.1016/j.jcp.2016.06.026⟩. ⟨hal-01336315⟩ Plus de détails...
In this work, we propose a numerical framework to simulate fluid flows in interaction with moving porous media of complex geometry. It is based on the Lattice Boltzmann method including porous effects via a Brinkman-Forchheimer-Darcy force model coupled to the Immersed Boundary method to handle complex ge-ometries and moving structures. The coupling algorithm is described in detail and it is validated on well-established literature test cases for both stationary and moving porous configurations. The proposed method is easy to implement and efficient in terms of CPU cost and memory management compared to alternative methods which can be used to deal with moving immersed porous media, e.g. re-meshing at each time step or use of a moving/chimera mesh. An overall good agreement was obtained with reference results, opening the way to the numerical simulation of moving porous media for flow control applications.
Marianna Pepona, Julien Favier. A coupled Immersed Boundary – Lattice Boltzmann method for incompressible flows through moving porous media A coupled Immersed Boundary -Lattice Boltzmann method for incompressible flows through moving porous media. Journal of Computational Physics, 2016, 321, pp.1170-1184. ⟨10.1016/j.jcp.2016.06.026⟩. ⟨hal-01336315⟩
The problem of flapping filaments in an uniform incoming flow is tackled using a Lattice Boltzmann—Immersed Boundary method. The fluid momentum equations are solved on a Cartesian uniform lattice while the beating filaments are tracked through a series of markers, whose dynamics are functions of the forces exerted by the fluid, the filament flexural rigidity and the tension. The instantaneous wall conditions on the filament are imposed via a system of singular body forces, consistently discretised on the lattice of the Boltzmann equation. We first consider the case of a single beating filament, and then the case of multiple beating filaments in a side-by-side configuration, focussing on the modal behaviour of the whole dynamical systems.
Julien Favier, Alistair Revell, Alfredo Pinelli. Fluid Structure Interaction of Multiple Flapping Filaments Using Lattice Boltzmann and Immersed Boundary Methods. Advances in Fluid-Structure Interaction, 133, Springer, pp.167-178, 2016, Notes on Numerical Fluid Mechanics and Multidisciplinary Design 978-3-319-27384-6. ⟨10.1007/978-3-319-27386-0_10⟩. ⟨hal-01705549⟩
Shang-Gui Cai, Abdellatif Ouahsine, Julien Favier, Yannick Hoarau. Improved Implicit Immersed Boundary Method via Operator Splitting. Ibrahimbegovic, A. Computational Methods for Solids and Fluids : Multiscale Analysis, Probability Aspects and Model Reduction, 41, Springer, pp.49-66, 2016, Computational Methods in Applied Sciences, 978-3-319-27996-1. ⟨10.1007/978-3-319-27996-1_3⟩. ⟨hal-01462069⟩ Plus de détails...
We present an implicit immersed boundary method via operator splitting technique for simulating fluid flow over moving solid with complex shape. An additional moving force equation is derived in order to impose the interface velocity condition exactly on the immersed surface. The moving force matrix is formulated to be symmetric and positive definite, thus its calculation is computational inexpensive by using the conjugate gradient method. Moreover, the proposed immersed boundary method is incorporated into the rotational incremental projection method as a plug-in. No numerical boundary layers will be generated towards the velocity and pressure during the calculation. The method is validated through various benchmark tests.
Shang-Gui Cai, Abdellatif Ouahsine, Julien Favier, Yannick Hoarau. Improved Implicit Immersed Boundary Method via Operator Splitting. Ibrahimbegovic, A. Computational Methods for Solids and Fluids : Multiscale Analysis, Probability Aspects and Model Reduction, 41, Springer, pp.49-66, 2016, Computational Methods in Applied Sciences, 978-3-319-27996-1. ⟨10.1007/978-3-319-27996-1_3⟩. ⟨hal-01462069⟩
Cai S-G., Ouahsine A., Julien Favier, Hoarau Y.. Improved Implicit Immersed Boundary Method via Operator Splitting, Computational Methods for Solids and Fluids. Multiscale Analysis, Probability Aspects and Model Reduction, Computational Methods in Applied Sciences, Springer, pp.49--66, 2016. ⟨hal-01313518⟩ Plus de détails...
Cai S-G., Ouahsine A., Julien Favier, Hoarau Y.. Improved Implicit Immersed Boundary Method via Operator Splitting, Computational Methods for Solids and Fluids. Multiscale Analysis, Probability Aspects and Model Reduction, Computational Methods in Applied Sciences, Springer, pp.49--66, 2016. ⟨hal-01313518⟩
Zhe Li, Julien Favier, Umberto D 'Ortona, Sébastien Poncet. An immersed boundary-lattice Boltzmann method for single- and multi-component fluid flows. Journal of Computational Physics, 2016, 304, pp.424-440. ⟨10.1016/j.jcp.2015.10.026⟩. ⟨hal-01225681⟩ Plus de détails...
The paper presents a numerical method to simulate single-and multi-component fluid flows around moving/deformable solid boundaries, based on the coupling of Immersed Boundary (IB) and Lattice Boltzmann (LB) methods. The fluid domain is simulated with LB method using the single relaxation time BGK model, in which an interparticle potential model is applied for multi-component fluid flows. The IB-related force is directly calculated with the interpolated definition of the fluid macroscopic velocity on the Lagrangian points that define the immersed solid boundary. The present IB-LB method can better ensure the no-slip solid boundary condition, thanks to an improved spreading operator. The proposed method is validated through several 2D/3D single-and multi-component fluid test cases with a particular emphasis on wetting conditions on solid wall. Finally, a 3D two-fluid application case is given to show the feasibility of modeling the fluid transport via a cluster of beating cilia.
Zhe Li, Julien Favier, Umberto D 'Ortona, Sébastien Poncet. An immersed boundary-lattice Boltzmann method for single- and multi-component fluid flows. Journal of Computational Physics, 2016, 304, pp.424-440. ⟨10.1016/j.jcp.2015.10.026⟩. ⟨hal-01225681⟩
Pedro Valero-Lara, Francisco D. Igual, Manuel Prieto-Matías, Alfredo Pinelli, Julien Favier. Accelerating fluid–solid simulations (Lattice-Boltzmann & Immersed-Boundary) on heterogeneous architectures. Journal of computational science, 2015, 10, pp.249-261. ⟨10.1016/j.jocs.2015.07.002⟩. ⟨hal-01225734⟩ Plus de détails...
We propose a numerical approach based on the Lattice-Boltzmann (LBM) and Immersed Boundary (IB) methods to tackle the problem of the interaction of solids with an incompressible fluid flow, and its implementation on heterogeneous platforms based on data-parallel accelerators such as NVIDIA GPUs and the Intel Xeon Phi. We explain in detail the parallelization of these methods and describe a number of optimizations, mainly focusing on improving memory management and reducing the cost of host-accelerator communication. As previous research has consistently shown, pure LBM simulations are able to achieve good performance results on heterogeneous systems thanks to the high parallel efficiency of this method. Unfortunately, when coupling LBM and IB methods, the overheads of IB degrade the overall performance. As an alternative, we have explored different hybrid implementations that effectively hide such overheads and allow us to exploit both the multi-core and the hardware accelerator in a cooperative way, with excellent performance results.
Pedro Valero-Lara, Francisco D. Igual, Manuel Prieto-Matías, Alfredo Pinelli, Julien Favier. Accelerating fluid–solid simulations (Lattice-Boltzmann & Immersed-Boundary) on heterogeneous architectures. Journal of computational science, 2015, 10, pp.249-261. ⟨10.1016/j.jocs.2015.07.002⟩. ⟨hal-01225734⟩
Julien Favier, Alistair Revell, Alfredo Pinelli. Numerical study of flapping filaments in a uniform fluid flow. Journal of Fluids and Structures, 2015, 53, pp.26-35. ⟨10.1016/j.jfluidstructs.2014.11.010⟩. ⟨hal-01118360⟩ Plus de détails...
The coupled dynamics of multiple flexible filaments (also called monodimen-sional flags) flapping in a uniform fluid flow is studied numerically for the cases of a side-by-side arrangement, and an in-line configuration. The modal behaviour and hydrodynamical properties of the sets of filaments are studied using a Lattice Boltzmann-Immersed Boundary method. The fluid momentum equations are solved on a Cartesian uniform lattice while the beating filaments are tracked through a series of markers, whose dynamics are functions of the forces exerted by the fluid, the filaments flexural rigidity and the tension. The instantaneous wall conditions on the filaments are imposed via a system of singular body forces, consistently discretised on the lattice of the Boltzmann equation. The results exhibits several flapping modes for two and three filaments placed side-by-side and are compared with experimental and theoretical studies. The hydrodynamical drafting, observed so far only experimentally on configurations of in-line flexible bodies, is also revisited numerically in this work, and the associated physical mechanism is identified. In certain geometrical and structural configuration, it is found that the upstream body experiences a reduced drag compared to the downstream body, which is the contrary of what is encountered on rigid bodies (cars, bicycles).
Julien Favier, Alistair Revell, Alfredo Pinelli. Numerical study of flapping filaments in a uniform fluid flow. Journal of Fluids and Structures, 2015, 53, pp.26-35. ⟨10.1016/j.jfluidstructs.2014.11.010⟩. ⟨hal-01118360⟩
S-G Cai, A Ouahsine, H Smaoui, Julien Favier, Yannis Hoarau. An efficient implicit direct forcing immersed boundary method for incompressible flows. Journal of Physics: Conference Series, 2015, 574 (012165), pp.5. ⟨10.1088/1742-6596/574/1/012165⟩. ⟨hal-01225703⟩ Plus de détails...
A novel efficient implicit direct forcing immersed boundary method for incompressible flows with complex boundaries is presented. In the previous work [1], the calculation is performed on the Cartesian grid regardless of the immersed object, with a fictitious force evaluated on the Lagrangian points to mimic the presence of the physical boundaries. However the explicit direct forcing method [1] fails to accurately impose the non-slip boundary condition on the immersed interface. In the present work, the calculation is based on the implicit treatment of the artificial force while in an effective way of system iteration. The accuracy is also improved by solving the Navier-Stokes equation with the rotational incremental pressure- correction projection method of Guermond and Shen [2]. Numerical simulations performed with the proposed method are in good agreement with those in the literature.
S-G Cai, A Ouahsine, H Smaoui, Julien Favier, Yannis Hoarau. An efficient implicit direct forcing immersed boundary method for incompressible flows. Journal of Physics: Conference Series, 2015, 574 (012165), pp.5. ⟨10.1088/1742-6596/574/1/012165⟩. ⟨hal-01225703⟩
Francisco Toja-Silva, Julien Favier, Alfredo Pinelli. Radial Basis Function (RBF)-based Interpolation and Spreading for the Immersed Boundary Method. Computers and Fluids, 2014, 105, pp.66-75. ⟨10.1016/j.compfluid.2014.09.026⟩. ⟨hal-01069809⟩ Plus de détails...
Immersed boundary methods are efficient tools of growing interest as they allow to use generic CFD codes to deal with complex, moving and deformable geometries, for a reasonable computational cost compared to classical body- conformal or unstructured mesh approaches. In this work, we propose a new immersed boundary method based on a radial basis functions frame- work for the spreading-interpolation procedure. The radial basis function approach allows for dealing with a cloud of scattered nodes around the im- mersed boundary, thus enabling the application of the devised algorithm to any underlying mesh system. The proposed method can also keep into ac- count both Dirichlet and Neumann type conditions. To demonstrate the capabilities of our novel approach, the imposition of Dirichlet boundary con- ditions on a 2D cylinder geometry in a Navier-Stokes CFD solver, and the imposition of Neumann boundary conditions on an adiabatic wall in an un- steady heat conduction problem are considered. One of the most significant advantage of the proposed method lies in its simplicity given by the algo- rithmic possibility of carrying out the interpolation and spreading steps all together, in a single step.
Francisco Toja-Silva, Julien Favier, Alfredo Pinelli. Radial Basis Function (RBF)-based Interpolation and Spreading for the Immersed Boundary Method. Computers and Fluids, 2014, 105, pp.66-75. ⟨10.1016/j.compfluid.2014.09.026⟩. ⟨hal-01069809⟩
Alex Skillen, Alistair Revell, Alfredo Pinelli, Ugo Piomelli, Julien Favier. Flow over a Wing with Leading-Edge Undulations. AIAA Journal, 2014, 53 (2), pp.464-472. ⟨10.2514/1.J053142⟩. ⟨hal-01069899⟩ Plus de détails...
The stall-delaying properties of the humpback whale flipper have been observed and quantified in recent years, through both experimental and numerical studies. In the present work we report numerical simulations of an infinite span wing with an idealised representation of this geometry, at a Reynolds number of 1.2 × 105 . Us- ing Large Eddy Simulation, we first establish an adequate spatial resolution before also examining the spanwise extent of the domain. We then proceed to analyse these results to provide an explanation of the conditions that drive the lift observed be- yond the conventional stall angle. The undulating leading-edge geometry gives rise to a span-wise pressure gradient that drives a secondary flow towards the regions of minimum chord. In turn, this leads to the entrainment of higher-momentum fluid into the region behind the maximum chord, which energises the boundary layer and delays stall. Aside from demonstrating a significant post-stall lift, the undulations also have the added benefit of substantially reducing lift fluctuations.
Alex Skillen, Alistair Revell, Alfredo Pinelli, Ugo Piomelli, Julien Favier. Flow over a Wing with Leading-Edge Undulations. AIAA Journal, 2014, 53 (2), pp.464-472. ⟨10.2514/1.J053142⟩. ⟨hal-01069899⟩
Julien Favier, Alistair Revell, Alfredo Pinelli. A Lattice Boltzmann - Immersed Boundary method to simulate the fluid interaction with moving and slender flexible objects. Journal of Computational Physics, 2014, 261, pp.145-161. ⟨10.1016/j.jcp.2013.12.052⟩. ⟨hal-00822044⟩ Plus de détails...
A numerical approach based on the Lattice Boltzmann and Immersed Boundary methods is pro- posed to tackle the problem of the interaction of moving and/or deformable slender solids with an incompressible fluid flow. The method makes use of a Cartesian uniform lattice that encom- passes both the fluid and the solid domains. The deforming/moving elements are tracked through a series of Lagrangian markers that are embedded in the computational domain. Differently from classical projection methods applied to advance in time the incompressible Navier-Stokes equa- tions, the baseline Lattice Boltzmann fluid solver is free from pressure corrector step, which is known to affect the accuracy of the boundary conditions. Also, in contrast to other immersed boundary methods proposed in the literature, the proposed algorithm does not require the in- troduction of any empirical parameter. In the case of rigid bodies, the position of the markers delimiting the surface of an object is updated by tracking both the position of the center of mass of the object and its rotation using Newton's Laws and the conservation of angular momentum. The dynamics of a flexible slender structure is determined as a function of the forces exerted by the fluid, its flexural rigidity and the tension necessary to enforce the filament inextensibility. For both rigid and deformable bodies, the instantaneous no-slip and impermeability conditions on the solid boundary are imposed via external and localized body forces which are consistently introduced into the Lattice Boltzmann equation. The validation test-cases for rigid bodies in- clude the case of an impulsively started plate and the sedimentation of particles under gravity in a fluid initially at rest. For the case of deformable slender structures we consider the beating of both a single filament and a pair filaments induced by the interaction with an incoming uniformly streaming flow.
Julien Favier, Alistair Revell, Alfredo Pinelli. A Lattice Boltzmann - Immersed Boundary method to simulate the fluid interaction with moving and slender flexible objects. Journal of Computational Physics, 2014, 261, pp.145-161. ⟨10.1016/j.jcp.2013.12.052⟩. ⟨hal-00822044⟩
Julien Favier, Alfredo Pinelli, Ugo Piomelli. Control of the separated flow around an airfoil using a wavy leading edge inspired by humpback whale flippers. Comptes Rendus Mécanique, 2012, 340 (1-2), pp.107-114. ⟨10.1016/j.crme.2011.11.004⟩. ⟨hal-00941404⟩ Plus de détails...
The influence of spanwise geometrical undulations of the leading edge of an infinite wing is investigated numerically at low Reynolds number, in the context of passive separation control and focusing on the physical mechanisms involved. Inspired by the tubercles of the humpback whale flippers, the wavy leading edge is modeled using a spanwise sinusoidal function whose amplitude and wavelength constitute the parameters of control. A direct numerical simulation is performed on a NACA0020 wing profile in a deep stall configuration (α=20°α=20°), with and without the presence of the leading edge waviness. The complex solid boundaries obtained by varying the sinusoidal shape of the leading edge are modeled using an immersed boundary method (IBM) recently developed by the authors [Pinelli et al., J. Comput. Phys. 229 (2010) 9073-9091]. A particular set of wave parameters is found to change drastically the topology of the separated zone, which becomes dominated by streamwise vortices generated from the sides of the leading edge bumps. A physical analysis is carried out to explain the mechanism leading to the generation of these coherent vortical structures. The role they play in the control of boundary layer separation is also investigated, in the context of the modifications of the hydrodynamic performances which have been put forward in the literature in the last decade.
Julien Favier, Alfredo Pinelli, Ugo Piomelli. Control of the separated flow around an airfoil using a wavy leading edge inspired by humpback whale flippers. Comptes Rendus Mécanique, 2012, 340 (1-2), pp.107-114. ⟨10.1016/j.crme.2011.11.004⟩. ⟨hal-00941404⟩
Alfredo Pinelli, I. Z. Naqavi, Ugo Piomelli, Julien Favier. Immersed-boundary methods for general finite-difference and finite-volume Navier-Stokes solvers. Journal of Computational Physics, 2010, 229 (24), pp.9073-9091. ⟨10.1016/j.jcp.2010.08.021⟩. ⟨hal-00951516⟩ Plus de détails...
We present an immersed-boundary algorithm for incompressible flows with complex boundaries, suitable for Cartesian or curvilinear grid system. The key stages of any immersed-boundary technique are the interpolation of a velocity field given on a mesh onto a general boundary (a line in 2D, a surface in 3D), and the spreading of a force field from the immersed boundary to the neighboring mesh points, to enforce the desired boundary conditions on the immersed-boundary points. We propose a technique that uses the Reproducing Kernel Particle Method [W.K. Liu, S. Jun, Y.F. Zhang, Reproducing kernel particle methods, Int. J. Numer. Methods Fluids 20(8) (1995) 1081-1106] for the interpolation and spreading. Unlike other methods presented in the literature, the one proposed here has the property that the integrals of the force field and of its moment on the grid are conserved, independent of the grid topology (uniform or non-uniform, Cartesian or curvilinear). The technique is easy to implement, and is able to maintain the order of the original underlying spatial discretization. Applications to two- and three-dimensional flows in Cartesian and non-Cartesian grid system, with uniform and non-uniform meshes are presented.
Alfredo Pinelli, I. Z. Naqavi, Ugo Piomelli, Julien Favier. Immersed-boundary methods for general finite-difference and finite-volume Navier-Stokes solvers. Journal of Computational Physics, 2010, 229 (24), pp.9073-9091. ⟨10.1016/j.jcp.2010.08.021⟩. ⟨hal-00951516⟩
Jérôme Hoepffner, Alessandro Bottaro, Julien Favier. Mechanisms of non-modal energy amplification in channel flow between compliant walls. Journal of Fluid Mechanics, 2010, 642, pp.489-507. ⟨10.1017/S0022112009991935⟩. ⟨hal-01073478⟩ Plus de détails...
The mechanisms leading to large transient growth of disturbances for the flow in a channel with compliant walls are investigated. The walls are modeled as thin spring-backed plates, and the flow dynamics is modeled using the Navier-Stokes equations linearised round the Poiseuille profile. Analysis for streamwise-invariant perturbations show that this fluid- structure system can sustain oscillatory energy evolution of large amplitude, in the form of spanwise standing waves. Such waves are related to the travelling waves which a free wall can support, modified to account for an 'added mass' effect. Simple scaling arguments are found to provide results in excellent agreement with computations of optimal disturbances, for low to moderate values of the stiffness parameter characterising the compliant surface.
Jérôme Hoepffner, Alessandro Bottaro, Julien Favier. Mechanisms of non-modal energy amplification in channel flow between compliant walls. Journal of Fluid Mechanics, 2010, 642, pp.489-507. ⟨10.1017/S0022112009991935⟩. ⟨hal-01073478⟩
Alessandro Bottaro, Julien Favier, Joel Guerrero, Divya Venkataraman, Hakan Wedin. Sulla scia di Icaro. Sapere, Edizioni Dedalo, pp.66-77, 2009, 9788822093981. ⟨hal-01073987⟩ Plus de détails...
La progettazione di velivoli dal minimo attrito tiene impegnati i ricercatori del DICAT di Genova che lavorano al progetto europeo FLUBIO. La realizzazione del "perfetto automa volante" trae ispirazione dalla natura e in particolare dal volo dell'airone, un ottimo modello per velivoli con ali ricoperte da piume che battono al vento
Alessandro Bottaro, Julien Favier, Joel Guerrero, Divya Venkataraman, Hakan Wedin. Sulla scia di Icaro. Sapere, Edizioni Dedalo, pp.66-77, 2009, 9788822093981. ⟨hal-01073987⟩
Laurent Cordier, Badr Abou El Majd, Julien Favier. Calibration of POD reduced-order models using Tikhonov regularization. International Journal for Numerical Methods in Fluids, 2009, 63 (2), pp.269-296. ⟨10.1002/fld.2074⟩. ⟨hal-01073978⟩ Plus de détails...
In this paper we compare various methods of calibration that can be used in practice to improve the accuracy of reduced-order models based on Proper Orthogonal Decomposition. The bench mark configuration retained corresponds to a case of relatively simple dynamics: a two-dimensional flow around a cylinder for a Reynolds number of 200. We generalize to the first and second-order the method of calibration based on Tikhonov regularization recently used in [1]. Finally, we show that for this flow configuration this procedure is the most effective in terms of reduction of errors.
Laurent Cordier, Badr Abou El Majd, Julien Favier. Calibration of POD reduced-order models using Tikhonov regularization. International Journal for Numerical Methods in Fluids, 2009, 63 (2), pp.269-296. ⟨10.1002/fld.2074⟩. ⟨hal-01073978⟩
Journal: International Journal for Numerical Methods in Fluids
Julien Favier, Antoine Dauptain, Davide Basso, Alessandro Bottaro. Passive separation control using a self-adaptive hairy coating. Journal of Fluid Mechanics, 2009, 627, pp.451 - 483. ⟨hal-01073967⟩ Plus de détails...
A model of hairy medium is developed using a homogenized approach, and the fluid flow around a circular cylinder partially coated with hair is analyzed by means of nu- merical simulations. The capability of this coating to adapt to the surrounding flow is investigated, and its benefits are discussed in the context of separation control. This fluid-structure interaction problem is solved with a partitioned approach, based on the direct resolution of the Navier-Stokes equations together with a non-linear set of equa- tions describing the dynamics of the coating. A volume force, arising from the presence of a cluster of hair, provides the link between the fluid and the structure problems. For the structure part, a subset of reference elements approximates the whole layer. The dy- namics of these elements is governed by a set of equations based on the inertia, elasticity, interaction and losses effects of articulated rods. The configuration chosen is that of the two-dimensional flow past a circular cylinder at Re = 200, a simple and well documented test case. Aerodynamics performances quantified by the Strouhal number, the drag and the maximum lift in the laminar unsteady regime are modified by the presence of the coating. A set of parameters corresponding to a realistic coating (length of elements, porosity, rigidity) is found, yielding an average drag reduction of 15% and a decrease of lift fluctuations by about 40%, associated to a stabilization of the wake.
Julien Favier, Antoine Dauptain, Davide Basso, Alessandro Bottaro. Passive separation control using a self-adaptive hairy coating. Journal of Fluid Mechanics, 2009, 627, pp.451 - 483. ⟨hal-01073967⟩
Antoine Dauptain, Julien Favier, Alessandro Bottaro. Hydrodynamics of ciliary propulsion. Journal of Fluids and Structures, 2008, 24 (8), pp.1156-1165. ⟨10.1016/j.jfluidstructs.2008.06.007⟩. ⟨hal-01073968⟩ Plus de détails...
A numerical approach is developed to study the effect on a fluid of the regular oscillations of an array of flexible cilia which hinge around points on a wall. The specific application studied concerns the ctenophore Pleurobrachia pileus, a small marine invertebrate of quasi-spherical shape and diameter of the order of the centimeter which swims in water thanks to the rhythmic beating of eight rows of hair-like cilia aligned along its body. Only one row of cilia is studied here, in a three-dimensional setting. The technique presented is general enough to allow its application to a variety of fluid-structure interaction problems. The physical mechanisms of the propulsion are highlighted, by analysing the results of three-dimensional simulations. A parametric study involving natural and non-natural parameters leads to a better understanding of the propulsive characteristics of ctenophores; results show that the specific power expended increases with the increase of the beating frequency of the row of cilia, in agreement with experiments.
Antoine Dauptain, Julien Favier, Alessandro Bottaro. Hydrodynamics of ciliary propulsion. Journal of Fluids and Structures, 2008, 24 (8), pp.1156-1165. ⟨10.1016/j.jfluidstructs.2008.06.007⟩. ⟨hal-01073968⟩
Julien Favier, Laurent Cordier, Azeddine Kourta. Sur l’optimisation d’actionneurs pour le contrôle d’écoulements. Mechanics & Industry, 2007, 8, pp.259-265. ⟨10.1051/meca:2007047⟩. ⟨hal-01073972⟩ Plus de détails...
L'objectif de ce travail est de construire par POD (@ Proper Orthogonal Decomposition A) des mod'eles d'ordre r ́eduit permettant de reproduire de mani'ere fiable la dynamique spatio-temporelle d'un ́ecoulement d ́ecoll ́e. L'int ́erˆet croissant pour ces mod'eles r ́eduits de dynamique s'explique par leur utilisation potentielle dans la r ́esolution de probl'emes d'optimisation sous contraintes de grande taille, rencontr ́es en controˆle d' ́ecoulements. La d ́emarche g ́en ́erale consiste 'a remplacer le mod'ele d ́etaill ́e de l' ́ecoulement (les ́equations de Navier-Stokes), par un mod'ele approch ́e, plus rapide 'a r ́esoudre et contenant les caract ́eristiques essentielles de la dynamique. La POD, optimale au sens de la reconstruction ́energ ́etique, permet d'approximer la dynamique de l' ́ecoulement dans un sous-espace g ́en ́er ́e par un petit nombre de modes. Diff ́erentes m ́ethodes de calibration sont ici d ́evelopp ́ees afin d'am ́eliorer la pr ́ediction du mod'ele de dimension r ́eduite, et ainsi rendre cette approche utilisable dans le cadre d'une probl ́ematique de contrˆole d' ́ecoulements. Essentiellement, ces m ́ethodes consistent 'a ajouter aux ́equations du mod'ele des termes suppl ́ementaires calcul ́es comme solutions d'un probl'eme de minimisation sous contraintes.
Julien Favier, Laurent Cordier, Azeddine Kourta. Sur l’optimisation d’actionneurs pour le contrôle d’écoulements. Mechanics & Industry, 2007, 8, pp.259-265. ⟨10.1051/meca:2007047⟩. ⟨hal-01073972⟩
Julien Favier, Azeddine Kourta. Étude du contrôle du décollement sur un profil d'aile par mesures PIV et analyse POD. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2006, 334, pp.272-278. ⟨10.1016/j.crme.2006.02.005⟩. ⟨hal-01073970⟩ Plus de détails...
The purpose of this study is the active control of flow separation on an ONERA D airfoil, using continuous blowing microjets. Particle Image Velocimetry (PIV) is used to measure velocity fields at midspan around the airfoil in both controlled and uncontrolled cases. Post-processing based on Proper Orthogonal Decomposition (POD) is developed to exhibit the main energetic features of the flow. Therefore, the detailed study of the POD modes for separated and stalled cases leads to a better understanding of the control mechanisms. Moreover, the POD basis computed for uncontrolled and controlled cases, opens the way to optimisation of control strategies.
Julien Favier, Azeddine Kourta. Étude du contrôle du décollement sur un profil d'aile par mesures PIV et analyse POD. Comptes rendus de l’Académie des sciences. Série IIb, Mécanique, 2006, 334, pp.272-278. ⟨10.1016/j.crme.2006.02.005⟩. ⟨hal-01073970⟩
Journal: Comptes rendus de l’Académie des sciences. Série IIb, Mécanique
Sébastien Bourgois, Jean Tensi, Emmanuel Sommier, Julien Favier. Experimental Investigations on Fluidic Control Over an Airfoil. Journal of Flow Visualization and Image Processing, 2006, 13 (3), pp.265-286. ⟨10.1615/JFlowVisImageProc.v13.i3.40⟩. ⟨hal-01073973⟩ Plus de détails...
This study presents the development of two fluidic actuators − namely, microjets and tangential blowing actuator (TBA), designed for flow separation control. The developed actuators are compact enough to fit inside an ONERA D profiled wing with a chord of 0.35 m. Test bench experiments showed that the microjets (resp. TBA) were able to produce exit velocities up to 330 m/s (resp. 60 m/s). These actuators were placed in the model and were tested in wind tunnels for various blowing rates. The investigations included the use of force balance measurements, on-surface flow visualization with pigmented oil, off-surface flow visualizations with smoke, surface pressure distribution measurements, and Particle Image Velocimetry (PIV). Most of the tests were performed at free-stream velocities between 20 m/s (for PIV) and 40 m/s, corresponding to Reynolds numbers in the range 0.47 × 10^6−0.93 × 10^6 . The angle of attack varied from −2 to 20 degrees. Experiments were conducted using the naturally occurring laminar boundary layer as well as for a turbulent boundary layer. In such a case, rough strips were used in the vicinity of the leading edge. The present tests show the efficiency of these devices to delay separation and improve aerodynamic performances of the wing: for example, a maximum of 30% gain in CL has been reached using the microjets. Both actuators tend to increase the lift coefficient CL after stall and areas of separated flow have been eliminated by applying control, as suggested by flow visualizations and PIV velocity fields.
Sébastien Bourgois, Jean Tensi, Emmanuel Sommier, Julien Favier. Experimental Investigations on Fluidic Control Over an Airfoil. Journal of Flow Visualization and Image Processing, 2006, 13 (3), pp.265-286. ⟨10.1615/JFlowVisImageProc.v13.i3.40⟩. ⟨hal-01073973⟩
Journal: Journal of Flow Visualization and Image Processing
