Evaluation of Detached Eddy Simulations for predicting the flow over periodic hills

Abstract

The performance of an hybrid LES-RANS strategy, the Detached Eddy Simulation (DES), as a predictive tool for turbulent channel flow with massive separation is scrutinized. This is undertaken in a collaborative effort involving five different flow solvers used by five different groups to cover a broad range of numerical methods and implementations. This paper concentrates on DES results obtained with a computational mesh of approximately one million cells. The results are compared to those obtained by Large Eddy Simulations (LES) using the standard and the dynamic Smagorinsky models and an alternative hybrid LES-RANS -all computed on the same grid. Data of a highly resolved LES (roughly 13 million cells) are used for reference. Furthermore, the impact of resolution and, therefore, the location of the LES-RANS interface is studied.

Highly resolved experimental results of the separated flow in a channel with streamwise periodic constrictions

“…Due to computational limitations at the time of the study, the grid was relatively coarse. Finally, it was concluded that the subgrid model and the finer mesh influence the results to a larger extent, and therefore a spanwise domain of only z/h = 4.5 was used in later studies (Temmerman et al 2003;Fröhlich et al 2005;Šarić et al 2007;Hickel et al 2008;Manhart et al 2008;Breuer et al 2009;Diosady & Murman 2014;Chang et al 2015). However, as the size of the computational domain in the spanwise direction is smaller than two times the size of a packet of structures, the convergence of the average solution using spanwise averaging might be accelerated, but it is questionable if this approach leads to the physically true values considering that the flow is correlated in the spanwise direction.…”

“…These results compare well with the results of Rapp & Manhart (2011) according to figure 11. Since the separation and reattachment at a smooth geometry strongly depends on the choice of the subgrid model in LES and DES, the results of previous numerical studies are also included in the graph (Temmerman et al 2003;Fröhlich et al 2005;Šarić et al 2007;Hickel et al 2008;Breuer et al 2009). Often the numerical simulations predict an earlier flow separation according to figure 11.…”

“…This flow has been extensively studied using various numerical methods and subgrid models (Günther & von Rohr 2003;Šarić et al 2007;Hickel, Kempe & Adams 2008;Manhart, Peller & Brun 2008). Šarić et al (2007) have shown that the results depend strongly on the CFD approach applied for the numerical integration of the equations (unsteady Reynolds-averaged Navier-Stokes equations, detached eddy simulations (DES), large eddy simulations (LES), direct numerical simulations (DNS)) and Temmerman et al (2003) examined the strong sensitivity of the LES results on the turbulence models.…”

Investigation of the sensitivity of turbulent closures and coupling of hybrid RANS‐LES models for predicting flow fields with separation and reattachment

“…The periodic hills simulations have also been performed using shear stress transport (SST)-DDES [37], partially averaged Navier-Stokes [38], partially integrated transport modeling and segregated modeling [39], and flow simulation methodology [12] approaches. For example, the range of X s =H and X r =H values in the joint study in Reference [35] were 0:18 0:27 and 4:3 5:1, respectively. Most of these studies showed similar profiles of the mean velocity and the Reynolds stresses.…”

Segregated coupling of large-eddy simulations with downstream Reynolds-Averaged Navier–Stokes calculations

“…These configurations are frequently used as test beds for the development of hybrid LES/RANS methods, e.g. in [8][9][10][11][12]. For the present study, the channel flow serves as an accuracy test of the coupling, since for this fully developed and self-similar flow any changes of statistics in the streamwise directions can be attributed to the presence of the interface.…”