Comparative Results From a CFD Challenge Over a 2D Three-Element High-Lift Airfoil

bly with experiment for most of the codes. 5. There was a large variability in most of the velocity profile predictions. Computational results predict a stronger slat wake than measured suggesting a missing component in turbulence modeling, perhaps curvature effects. Symbols c = cruise or stowed airfoil chord C D = drag coefficient C f = skin-friction coefficient, where C f = t wall /q C L = lift coefficient C p = pressure coefficient M = freestream Mach number n = distance normal to airfoil surface q = freestream dynamic pressure 2 Re = Reynolds number based on cruise chord c x = coordinates along the chord direction a = angle of attack D = differential value t wall = wall shear stress Subscripts max = maximum valu

Comparative Results From a CFD Challenge Over a 2D ThreeElement High-Lift Airfoil

major part of the workshop centered on a blind test of various computational fluid dynamics (CFD) methods in which the flow about a two-dimensional (2D) three-element airfoil was computed without prior knowledge of the experimental data. Comparisons were made between computation and experiment for (a) lift, drag, and moment, (b) lift and drag increments due to Reynolds number and flap gap changes, (c) pressure and skinfriction distributions, and (d) mean velocity profiles. The results of this 'blind ' test revealed: 1. There was good agreement between several codes and the experimental results. In general, the Reynolds Averaged Navier-Stokes (RANS) methods showed less variability among codes than did potential/Euler solvers coupled with boundary-layer solution techniques. However, some of the coupled methods still provided excellent predictions. 2. Drag prediction using coupled methods agreed more closely with experiment than the RANS methods. Lift was more accurately predicted than drag for both methods. 3. The CFD methods did well in predicting lift and drag changes due to changes in Reynolds number, however, they did not perform as well when predicting lift and dra