Revision as of 12:42, 4 June 2012

Flow over curved backward-facing step

Semi-confined flows

Underlying Flow Regime 3-31

Evaluation

Comparison of LES results with experiments

Comparisons of the simulation results with the experimental measurements of Zhang and Zhong \cite{zhang2010experimental} are shown in Figs. \ref{fig:wallValidation}-\ref{fig:reynoldsStressValidation}. Only results obtained with the fine mesh (ie. corresponding to the data provided), are shown here. Comparisons with the coarse mesh results are given in Lardeau and Leschziner \cite{lardeau2011interaction}. General agreement of the profiles is very good, both for mean flow velocity (Fig. \ref{fig:velocityValidation}) and for the three components of the Reynolds stress tensor (Fig. \ref{fig:reynoldsStressValidation}). The major discrepancies are found on the wall-measurements: the skin-friction coefficient ${C_{f}}$ is slightly overestimated close to the separation, with a large peak of ${C_{f}}$ not present in the experimental results. The experimental skin friction data should be taken with care, as they were computed from the measured velocity field (bound to greater error in the near-wall region) rather than from direct measurements at the wall.

Comparison of RANS results with LES results and experiments

Results obtained with the four RANS models are shown in Figs. \ref{fig:RANS_CfCp}-\ref{fig:Tke_KOmega}. Only four quantities (wall shear stress, pressure coefficient, streamwise velocity and turbulent kinetic energy) are shown, but other parameters can of course be compared, such as dissipation or Reynolds-stress if using second-moment closure.

Contributed by: Sylvain Lardeau — CD-adapco