NUMERICAL SIMULATIONS OF NON-EQUILIBRIUM TURBULENT BOUNDARY LAYER FLOWING OVER A BUMP | ||
| ERJ. Engineering Research Journal | ||
| Article 4, Volume 32, Issue 2, April 2009, Pages 145-161 PDF (992.62 K) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/erjm.2009.69400 | ||
| Author | ||
| W. A. El-Askary | ||
| Mechanical Power Engineering Department, Faculty of Engineering, Menoufiya University. Shebin El-Kom, EGYPT | ||
| Abstract | ||
| Largeeddy simulation (LES) and Reynolds-averaged Navier-Stokes simulations (RANS) with different turbulence models (including the standard k - E , the standard k - 0, the shear stress transport k - 0 (SST- k - w model) and Spalart-Allmaras (S-A)-turbulence models) have been employed to compute the turbulent flow of a two-dimensional turbulent boundary Iayer over an unswept bump. The predictions of the simulations were compared to available experimental measurements in the literature. The comparisons of the LES and the SST- k - w model including the mean flow and turbulence stresses are in satisfied agreements with the available measurements. Though the flow experiences a strong adverse pressure gradient along the rear surface, the boundary layer is unique in that intennittent detachment occurring near the wall. The numerical results indicate that the boundary layer is not followed by mean-flow separation or incipient separation as that shown from the numerical results. The resolved turbulent shear stress is in a reasonable agreement with the experimental data, though the computational result of LES shows that its peak is over-predicted near the trailing edge of the bump, whiIe the other used turbulence models, except the standard k - & , under-predicts it. Analysis of the numerical results from LES confirms the experimental data, in which the existence of intemal layers over the bump surface upstream of the summit and along the downstream flat plate. It also demonstrates that the quasistep increase in skin fiiction is due to perturbations in pressure gradient. The surface curvature enhances the near-wall shear production of turbulent stresses and is responsible for the formation of the internal layers. The present investigation also explains the capability of the used RANS turbulence models to capture the driving mechanism for the surprisingly rapid return to equilibrium boundary layer over the trailing flat plate found in the measurements. | ||
| Keywords | ||
| Boundary layer; Bump flow; R4NS; LES | ||
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