Effects of pressure-gradient on turbulent counter-gradient transport

By using Reynolds Stress Closure Model (RSM) and k-e Model, the turbulent field of wing flow is numericallysimulated. In most practical situations, flows with changing pressuregradient are familiar, these pressure gradients may induce strongmodifications of turbulent structure, accordingly, affect the diffusion andtransportation process of turbulence. The effects of pressure gradient oncounter-gradient transport phenomena are studied. The computational resultsshow that RSM model can describe the CGT phenomena while k-e model cannot. Negative turbulent energy production appears in the result ofRSM, but it behaves differently with CGT: it gradually shrinks until theposition of the wing central part is reached, where it vanishes; while theCGT region exists all along. This fact shows that CGT phenomena is moregeneral than negative turbulent energy production. The pressure gradienttakes an important effect on the region of negative turbulent energyproduction and counter-gradient transport. In the CGT region, the relationbetween turbulent Reynolds stress and mean velocity gradient is nonlinear.