View source for Sig Turbulence / Flow over Periodic Hills

[[Sig Turbulence / Olivier Brugiere |Olivier Brugiere]], Universite Joseph Fourier, Grenoble, France

== Motivation ==

[[File:Hilloutlined.jpg|thumb|Figure 1 : Periodic hill]]
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. 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 [[http://cfd.mace.manchester.ac.uk/cgi-bin/cfddb/prpage.cgi?81&LES&database/cases/case81/Case_data&database/cases/case81&cas81_head.html&cas81_desc.html&cas81_meth.html&cas81_data.html&cas81_refs.html&cas81_rsol.html&1&1&1&1&1&unknown]]. 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 figure 1. 


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.

== Testcase description ==

=== Flow configuration ===

==== Geometrical Parameters ====

* Hill's heigh : <math>h = 28 mm</math>
* Streamwise distance : <math>L_{x} = 9,0 h</math>
* Normal wall heigh  : <math>L_{y} = 3,035 h</math>
* Spanwise distance  : <math>L_{y} = 4,5 h</math>

==== Boundary condition ====

* Streamwise condition : periodicity
* Spanwise condition : periodicity
* Normal to streamwise : two walls

=== Simulation details ===

[[File:Hill_mesh.jpg|thumb|Figure 2 : Hill mesh]]

We have make the geometry on Gambit Fig 2 and the mesh is composed by <math>Nx \times Ny \times Nz = 118 \times 33 \times96</math>.

The aim of my study is testing a posteriori near-wall low. To compare we are running three cases :

* With near-wall low
* With the Spalding Low [4]
* With the Mahart et al. low [5]

== Numerical results ==

Results of the simulations are available in the paper written by Duprat et al. [6]

== References ==

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

[2] Mellen, Frohlich and Rodi, 2000, Large Eddy Simulation of the flow over periodic hills, 16th IMACS World Congress , Lausanne. [http://cfd.mace.manchester.ac.uk/ercoftac/database/cases/case81/Case_ref/IfH_paper.ps]

[3] Temmerman and 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. [http://cfd.mace.manchester.ac.uk/ercoftac/database/cases/case81/Case_ref/TSFP2_09032001.ps]

[4] Spalding, 1961, A single formula for the law of the wall, Jl. Appl. Mech., vol 28, pp. 455-457

[5] Manhart, Peller and Brun, 2008, Near-wall scaling for turbulent boundary layers with adverse pressure gradient, Theor. Comput. Fluid Dyn., vol 22 , pp. 243-260.

[6] Duprat, Balarac, Métais, Congedo, and Brugière, O., 2011, A wall-layer model for large-eddy simulations of turbulent flows with/out pressure gradient. Physics of Fluids, 23, 015101.[http://pof.aip.org/resource/1/phfle6/v23/i1/p015101_s1]

Back to [[Sig Turbulence]]