REYNOLDS-NUMBER EFFECT ON THE SKIN FRICTION IN SEPARATED FLOWS BEHIND A BACKWARD-FACING STEP

Results from the present study show that the skin-friction coefficient decreases as the Reynolds number, Reh, increases in the following manner, Cf,min=-0.19 Reh-1/2. The -1/2 power relationship deduced from the correlation Cf,min vs. Rehindicates laminar like behavior which is consistent with the findings of Adams et al. (1984). Clauser's method, which is frequently used for the determination of the wall shear stress, leads to erroneous results when applied to the velocity measurements obtained in the near field of reattaching flows (and many other wall-bounded nonequilibrium flows). Direct measurements of the Cfusing the LOI technique give higher values than those obtained by the classical techniques. The normalized mean velocity on the wall coordinates violates the universal law-of-the-wall in the near field of reattaching flows. © 1995 Springer-Verlag.