Numerical Simulation of Unsteady Low-Reynolds-Number Separated Flows over Airfoils

boundary-layeredge is still slightly freestreamdependent, the level of eddy viscosity and therefore also the skin-friction coefŽ cient are not. Furthermore, the velocity distribution is consistent with the law-of-the-wall solution. As a second test case, the RAE2822 airfoil is considered (in particular, case 9 of Ref. 11). Figure 2 compares the pressure and skinfriction distributions of the different models to the experimental results. For the two Wilcox variants the shock is located slightly aft compared to the Cebeci–Smith model and the new k– x variant. Similarly as for the  at plate, theTNT k– x variantgives lower levels of the skin friction than the two Wilcox variants, and in this case closer to the Cebeci–Smith model and to the experimental values. Most likely, the more aft shock position and the higher skin friction for the two Wilcox variants are a result of higher eddy-viscosity levels (as were seen for the  at plate). This again may be a consequence of the values of x at the boundary-layeredge being too low. For the TNT k– x variant the absence of freestream dependency is shown for the skin-friction coefŽ cient.