Sig Turbulence / Flow over Periodic Hills

Olivier Brugiere, Universite Joseph Fourier, Grenoble, France

1 Motivation

The flow over bodies with massive separation constitutes an important area of applications for LES. In many geometrie we can find this kind of flow like the 2D backward-facing step, the asymmetric diffuser or the periodic hill.

• 2D backward-facing step : it's a quick test case because of it's a 2D model but the separation bubble is determined by the spet geometry.
• Asymmetric diffuser : we know experimental's data which was made by Buice and Eaton [[1]]. Unfortunatly, the Reynolds number of the fow was necessarily slow ($Re_{\tau} = 180$).
• Periodic Hills : we know experimental's data which was made by Almeida et al. [1] but in Mellen and al. [2] et Temmerman et al. [3] we can find that they have an influence of the side wall so the 1995 ERCOFTAC/IAHR workshop have cast a doubt on the true periodicity of the experimental configuration. But we have some data from LES with a good mesh like [[2]]

The probleme of this flow is the separtion bubble which is due to a adverse pressure gradient that's why this is a test case for many subgrid scale models (SGS) and for near-wall low.

2 Testcase description

2.1 Flow configuration

Flow over 2D periodic is in fact an experimental configuration with 9 hills. For the computational, we represent this configuration by a channel periodic with two half's hills like on the next figure :

Figure 1 : Periodic hills

3 References

[1] Almeida, Durao and Heitor , 1993, Experimental thermal and fluid science, Vol. 7, pp. 87-101.

[2] Mellen, Frohlich, Rodi , 2000, Large Eddy Simulation of the flow over periodic hills, 16th IMACS World Congress , Lausanne.

[3] Temmerman, Leschziner , 2001, Large Eddy Simulation of separated flow in a streamwise periodic channel construction, Int. Symp. on Turbulence and Shear Flow Phenomena, Stockholm, June 27-29.

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