Detailed Near Surface Flow about Yawed, Stranded Cables

摘要

This report describes the results of the second phase of an experimentalinvestigation of the flow about stranded cables or wire ropes. The purpose of the study was to consider, in some detail, the flow field near the cable and to provide additional experimental information related to the mechanisms associated with the generation of fluid forces on the cables. The development of a steady lift or side force on a stranded cable, yawed with respect to a flow, is a unique characteristic of a cable when compared to a circular cylinder. Experiments were conducted to measure the surface pressure distributions and near wake characteristics for a variety of stranded cable geometries and a circular cylinder. Rigid cable models and cylinders were tested in a low-speed wind tunnel. The models were yawed to four different yaw angles and tested within the Reynolds number range of 5,000 and 50,000. Surface pressure distributions on the yawed cables indicated that the lift force is the result of asymmetric boundary layer separation. Unsteady surface pressures on stationary cables were shown to correlate with earlier hot-wire measurements. Detailed flow visualization illustrated the complexity of the flow about the stranded cables. The influence of test support conditions were examined in order to provide a better understanding of end-effects in testing these long, slender models.