Christophe Friess

Aix-Marseille Université | AMU · Laboratoire de Mécanique, Modélisation & Procédés Propres M2P2 (UMR 6181)

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 for the generation of turbulent eddies. Several methods have been proposed which are able to reproduce realistic features for velocity fluctuations, exhibiting proper space- a...

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 fk which denotes the ratio of modeled to total kinetic energy. In RANS, fk=1 while in DNS it tends to zero. In the present study we propose an improved formulation for fk based o...

The partially averaged Navier–Stokes (PANS) model, proposed in Girimaji [Partially-averaged Navier-Stokes model for turbulence: a Reynolds-averaged Navier-Stokes to direct numerical simulation bridging method. ASME J Appl Mech. 2006;73(3):413–421], can be used to simulate turbulent flows either as a RANS, LES or DNS. The PANS model includes fk whic...

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. T...

The aim of the present work is to develop a seamless hybrid Reynolds-averaged Navier-Stokes (RANS) large-eddy simulation (LES) model based on transport equations for the subgrid stresses, using the elliptic-blending method to account for the nonlocal kinematic blocking effect of the wall. It is shown that the elliptic relaxation strategy of Durbin...

The partially averaged Navier-Stokes (PANS) model, proposed in Girimaji (2006), can be used to simulate turbulent flows either as a RANS, LES or DNS. The Partially Integrated Transport Model (PITM) is identical to PANS except that in PANS the diffusion coefficients in the k and ε are modified. Both models include f k which denotes the ratio of mode...

Detached Eddy Simulation is revisited, in the framework of temporal filtering. Indeed, its original version consists of sensitizing a turbulence model to the spatial grid step. This method is consistent with the RANS limit, for statistically homogeneous flows. But most of everyday applications are rather stationary. Therefore, it is worth attemptin...

The present paper concerns a numerical benchmark of various turbulence modelings, from RANS to LES, applied to Taylor-Couette-Poiseuille flows in a narrow gap cavity for six different combinations of rotational and axial Reynolds numbers. Two sets of refined Large-Eddy Simulation results, using the WALE and the Dynamic Smagorinsky subgrid scale mod...

christophe.friess@l3m.univ-mrs.fr

The present paper concerns a numerical benchmark of var-ious turbulence modelings, from RANS to LES, applied to Taylor-Couette-Poiseuille flows in a narrow gap cavity for six different combinations of rotational and axial Reynolds num-bers. Two sets of refined Large-Eddy Simulation results, us-ing the WALE [1] and the Dynamic Smagorinsky [2] subgri...

A criterion was established by Manceau et al. [1] enabling to analytically assess, for some simplified, close-to-equilibrium situations, the equivalence of hybrid RANS/LES methods. In the present paper, this criterion is tested upon the flow over a periodic hill at a bulk Reynolds number of 10595, which involves massive separation, thus strongly de...

Using temporal filtering in LES rather than spatial filtering provides a consistent formalism for a seamless hybridization of LES and RANS, thus leading to Hybrid Temporal LES (H-TLES). Such an hybrid model is presented, the so-called TPITM, which is the adaptation of the PITM (Partially Integrated Transport Model) to the temporal filtering framewo...

Abstract : In industrial situation, the computation of unsteady and three-dimensional cha- racteristics of complex flows, is often necessary. Large-eddy simulation demands prohibitive computational costs, peculiarly near walls. One of the objectives of hybrid methods, is to opti- mize the computational cost, by simulating certain areas of flows in...

Since large eddy simulation methods (LES) are too CPU-demanding for many complex industrial applications, a multitude of unsteady low-cost strategies have gained prominence over the last decade Fröhlich and von Terzi (2008); Sagaut et al (2006). Some of these models can be described as seamless hybrid RANS-LES models since the transition between RA...

The present article analytically shows that DES is equivalent to TPITM in that it provides the same partition of energy and, thus, very similar statistics of the resolved field if the coefficient C DES is made a function of the en-ergy ratio r. This result enables DES to be interpreted as a hybrid RANS/Temporal LES approach, i.e., as a model to clo...

A consistent formalism is developed for hybrid RANS-LES models in inhomogeneous, stationary flows, based on tempo-ral filtering. The issues of Galilean invariance of the filtering process, control of the amount of resolved energy, modelling of subfilter stresses and accounting for wall effects are addressed. The new model (TPITM) is validated in a...

An overview is given of the activities in the framework of the German-French Research Group on ”LES of Complex Flows” (DFG-CNRS FOR 507) with respect to the development of zonal and seamless hybrid LES/RANS computational methods based on a near-wall Eddy-Viscosity Model (EVM) and a near-wall Second-Moment Closure (SMC) respectively. The zonal schem...

In the frame of inhomogeneous turbulence, a consistent formalism to seamlessly bridge LES and RANS must be based on temporal filtering. Such an approach is presented, the temporal-PITM, based on a transport equations for the subfilter-scales. In order to obtain a balance resolved/modelled energy consistent with the cutoff frequency imposed by the l...