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-   -   Problems with validation of LES for turbulent annular flow (https://www.cfd-online.com/Forums/openfoam-verification-validation/178623-problems-validation-les-turbulent-annular-flow.html)

fgarita October 12, 2016 06:37

Problems with validation of LES for turbulent annular flow
 
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Hi everybody,

I am dealing with a LES of incompressible turbulent flow in annular pipe. My first goal is to reproduce, by means of OpenFOAM, the flow field obtained by Chung et al. (2002). The structured mesh I am using consists of (72,64,96) cells in the radial, azimuthal and axial directions, respectively, and my domain size is (r_in=1; r_out=2; L=15).
I am using pimpleFoam as solver (attached you find a .txt version of fvSchemes and fvSolution) The turbulence model I am using is the dynamicSmagorinsky model, that gives very good results in the LES for channel flow.

In my case, after making enough statistics, I observe that the two C_f coefficients (i.e. the dimensionless wall shear stresses, averaged both in time and space) for the inner and outer walls are still too small compared to the ones obtained by Chung et al. (2002) - they are about 60-70% of the ones obtained by Chung.
Also, if I plot the average velocity profile I observe a quite remarkable difference between Chung's profile and my profile.

Thus, I reckon that the problem may be due to numerics, since I observe a more diffusive profile. Is anybody able to help me understand the reason why this is so?

Thank you very much!
Francesco


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