The evolution of turbulent wall layer from free shear layer 13; 13;

The way that distinct structures are generated in the background of earlier qualitatively different structures is studied experimentally by examining the change from one type of turbulent flow to another. The development of the turbulent boundary layer on a flat plate is investigated for the condition in which it is located in the wake of another flat plate. Variations are reported for changes in the distance between plates, the momentum thickness of the up stream wake, and the pressure gradient on the wall layer. The zones of the wake where the layer evolves are important determinants of the resulting layer characteristics, and isolated but significant quantitative differences are identified between the experimental data and simple turbulence models. The results are of interest to studies of turbomachinery in which the wall layer of one blade row can be affected by the wake from the one which precedes it. (C.C.S.