MEASUREMENTS IN A PRESSURE-DRIVEN 3-DIMENSIONAL TURBULENT BOUNDARY-LAYER DURING DEVELOPMENT AND DECAY

Measurements of the turbulence structure in the outer layer of a three -dimensional turbulent boundary layer were made in an open-circuit low -speed blower tunnel. The three-dimensional turbulent boundary layer o n the floor of the tunnel was generated by a cross-stream pressure gra dient using a 30-deg bend in the horizontal plane. Downstream of the b end, the three-dimensional turbulent boundary layer gradually relaxed toward a two-dimensional turbulent boundary layer as the crossflow dec ayed slowly after the cross-stream pressure gradient was removed. Mean velocities were measured with a three-hole pressure probe, and turbul ence quantities, which included the Reynolds-stress tensor and the tri ple products, were measured with a cross-wire hot-wire anemometer. The experiment provides new data that isolate the effects of crossflow fr om the effects of an adverse streamwise pressure gradient that may hav e clouded the interpretations of previous three-dimensional turbulent boundary-layer experiments. Another advance over previous work is that enough turbulence quantities were measured for all terms in the Reyno lds-stress transport equations to be evaluated, allowing term-by-term tests of stress-transport turbulence models.