An examination of a 3D corner-step experiment

This paper presents results of LDV measurements in a complex three-dimensional (3D) turbulent flow. The experimental configuration studied, shown in Fig 1, provides a complex 1 parameter (step height) three-dimensional flow with two-dimensional (2D) relaxation limits in the spanwise direction (that is, 2D channel flow and 2D backstep). Note that this flow is more complex than the simple 2D back-step described by Eaton and Johnston, 1981, AIAA Journal, vol. 19, pp 1093-1100. However, when spanwise limits are taken out from either side of the centerline the flow relaxes to two well studied 2D flows. On the block side, the spanwise limit results in a 2D turbulent channel flow. On the step side, the spanwise limit results in the 2D back-step flow. In the center region of the facility, however the flow is strongly 3D. The data presented here, was taken with a three component laser Velocimetry system, thus all three velocity components can be measured simultaneously. The results presented here clearly indicate that this flow provides a complex 3D flow for turbulence model calibration with the added attraction of the 2D spanwise limits. In the region within two step-heights either side in span of the streamwise step edge, secondary flows are observed. In addition, a spanwise evolving streamwise reattachment length is seen. The prediction of the secondary motions along with the spanwise evolving streamwise reattachment length found here will provide a challenging test for any turbulence model.