LDV-MEASUREMENTS OF SPATIALLY PERIODIC FLOWS OVER A DETACHED SOLID-RIB ARRAY

Measurements of mean velocities, turbulence intensities, and Reynolds stresses are presented for spatially periodic flows in a duct of width -to-height ratio 2 with a detached solid-rib array. The Reynolds numbe r based on the duct hydraulic diameter and cross-sectional bulk mean v elocity (U-b), the pitch to rib-height ratio, and the rib-height to du ct-height ratio were 2 x 10(4), 10, and 0.133, respectively. The rib-d etached-distance to rib-height ratio was varied from 0 to 3.25 (duct a xis) to study its effect on wake length and asymmetry, convective velo city and turbulent kinetic energy immediately behind the rib, maximum turbulent shear stress, and turbulence anisotropy. The results showed that the dominant fluid dynamic factors responsible for the reported p eak values of local Nusselt number around the detached rib could be id entified. Moreover, the turbulence structure parameter distribution an d anisotropy were analyzed to examine the basic assumptions embedded i n the turbulence models. Furthermore, the secondary-pow mean velocitie s were found to be one to two order of magnitude smaller than U-b.