LARGE EDDY SIMULATIONS OF TURBULENT FLOWS WITH ADVERSE PRESSURE GRADIENTS

摘要

The work presents comparative results betweenwall friction and pressure coefficient predictionsfrom Large Eddy Simulation (LES) andReynolds-averaged Navier-Stokes (RANS) computationsin channel flows with an adverse pressuregradient created by a 2-D bump. Reynoldsnumbers range from Ret = 617 to 2000, basedon the friction velocity at the channel inlet. LESproduces very consistent results when comparedto DNS or other highly resolved LES. Twoequationand seven-equation RANS models arefound to correctly predict friction coefficients inzero and favorable pressure gradient regions, butthey fail in regions of adverse pressure gradients.The Reynolds stress transport model shows a betterperformance when compared to two-equationeddy-viscosity models, particularly in the higherReynolds number cases. However, none of theRANS models is able to capture the full physicsof turbulence related with adverse pressure gradients.Such limitations seem to be related to thefact that these models do not correctly describethe evolution of the turbulent kinetic energy closeto the walls in adverse pressure gradient regions.