Jérémie Janin, Fabien Duval, Christophe Friess, Pierre Sagaut. A new linear forcing method for isotropic turbulence with controlled integral length scale. Physics of Fluids, 2021, 33 (4), pp.045127. ⟨10.1063/5.0045818⟩. ⟨hal-03326165⟩ Plus de détails...
Turbulence is a common feature to all flows that surround us. Despite its ubiquity, particularly in industrial flows, it is very difficult to provide a mathematical framework to the generation of turbulent eddies. Several techniques have been proposed which are able to reproduce the main features of turbulent flows, such as realistic pressure and velocity fluctuations, exhibiting proper space- and time-correlations. These techniques are usually first evaluated upon sustained homogeneous isotropic turbulence by introducing body forces to the Navier-Stokes equations. Among these techniques, Lundgren suggested a successful forcing, applied in physical space. The latter approach unfortunately lacks predicting the integral length scale of turbulence. The present study provides a forcing method based on a reconstruction approach which consists in building fluctuations with a turbulent synthetic velocity field based on a prescribed energy spectrum model. The proposed approach is assessed by performing large-eddy simulations of a sustained homogeneous isotropic turbulence in a triply periodic box of size L = 2pi. Properties of the new forcing technique are discussed, drawing on both spatial and time correlations and also on the shape of energy spectrum together with the level of resolved turbulent kinetic energy. A special attention is put on the control of resolved turbulent energy. In this framework, an efficient selective forcing technique is derived, making use of spectral space features. The results show that the proposed approach allows to drive efficiently the resolved kinetic energy towards its target value while preserving the integral length scale independent of the domain size. It is observed that the resulting longitudinal length scale is overestimated by 13%, while the two-time correlations are recovered when using stochastic frequencies.
Jérémie Janin, Fabien Duval, Christophe Friess, Pierre Sagaut. A new linear forcing method for isotropic turbulence with controlled integral length scale. Physics of Fluids, 2021, 33 (4), pp.045127. ⟨10.1063/5.0045818⟩. ⟨hal-03326165⟩
Christophe Friess, Lars Davidson. A formulation of PANS capable of mimicking IDDES. International Journal of Heat and Fluid Flow, 2020, 86, pp.108666. ⟨10.1016/j.ijheatfluidflow.2020.108666⟩. ⟨hal-02944327⟩ Plus de détails...
Christophe Friess, Lars Davidson. A formulation of PANS capable of mimicking IDDES. International Journal of Heat and Fluid Flow, 2020, 86, pp.108666. ⟨10.1016/j.ijheatfluidflow.2020.108666⟩. ⟨hal-02944327⟩
Journal: International Journal of Heat and Fluid Flow
Christophe Friess, Lars Davidson. A formulation of PANS capable of mimicking IDDES. International Journal of Heat and Fluid Flow, 2020, 86, pp.108666. ⟨10.1016/j.ijheatfluidflow.2020.108666⟩. ⟨hal-03232146⟩ Plus de détails...
The partially averaged Navier-Stokes (PANS) model, proposed in Girimaji (2006), allows to simulate turbulent flows either in RANS, LES or DNS mode. The PANS model includes f k which denotes the ratio of modeled to total kinetic energy. In RANS, f k = 1 while in DNS it tends to zero. In the present study we propose an improved formulation for f k based on the H-equivalence introduced by Friess et al. (2015). In this formulation the expression of f k is derived to mimic Improved Delayed Detached Eddy Simulation (IDDES). This new formulation behaves in a very similar way as IDDES, even though the two formulations use different mechanisms to separate modeled and resolved scales. They show very similar performance in separated flows as well as in attached boundary layers. In particular, the novel formulation is able to (i) treat attached boundary layers as properly as IDDES, and (ii) "detect" laminar initial/boundary conditions, in which case it enforces RANS mode. Furthermore, it is found that the new formulation is numerically more stable than IDDES.
Christophe Friess, Lars Davidson. A formulation of PANS capable of mimicking IDDES. International Journal of Heat and Fluid Flow, 2020, 86, pp.108666. ⟨10.1016/j.ijheatfluidflow.2020.108666⟩. ⟨hal-03232146⟩
Journal: International Journal of Heat and Fluid Flow
Lars Davidson, Christophe Friess. A new formulation of f k for the PANS model. Journal of Turbulence, 2019, 20 (5), pp.322-336. ⟨10.1080/14685248.2019.1641605⟩. ⟨hal-02354566⟩ Plus de détails...
Lars Davidson, Christophe Friess. A new formulation of f k for the PANS model. Journal of Turbulence, 2019, 20 (5), pp.322-336. ⟨10.1080/14685248.2019.1641605⟩. ⟨hal-02354566⟩
Christophe Friess, Remi Manceau, T.B. Gatski. Toward an equivalence criterion for Hybrid RANS/LES methods. Computers and Fluids, 2015, 122, pp.233-246. ⟨10.1016/j.compfluid.2015.08.010⟩. ⟨hal-01246130⟩ Plus de détails...
A criterion is established to assess the equivalence between hybrid RANS/LES methods, called H-equivalence, based on the modeled energy of the unresolved scales, which leads to similar low-order statistics of the resolved motion. Different equilibrium conditions are considered, and perturbation analyses about the equilibrium states are performed. The procedure is applied to demonstrate the equivalence between two particular hybrid methods, and leads to relationships between hybrid method parameters that control the partitioning of energy between the resolved and unresolved scales of motion. This equivalence is validated by numerical results obtained for the cases of plane and periodically constricted channel flows. This concept of H-equivalence makes it possible to view different hybrid methods as models for the same system of equations: as a consequence, detached-eddy simulation (DES), which is shown to be H-equivalent to the temporal partially integrated transport model (T-PITM) in inhomogeneous, stationary situations, can be interpreted as a model for the subfilter stress involved in the temporally filtered Navier–Stokes equations.
Christophe Friess, Remi Manceau, T.B. Gatski. Toward an equivalence criterion for Hybrid RANS/LES methods. Computers and Fluids, 2015, 122, pp.233-246. ⟨10.1016/j.compfluid.2015.08.010⟩. ⟨hal-01246130⟩
