Vortex Characteristics over Delta Wing Subject to Transient Along-Core Blowing
Doppler anemometer (LDA), is around 1.2%. The blockage ratio of the half-wing model varies between 0.024 and 0.031 for different AOA. The momentum coefficient of blowing is defined as CM = (Vp/Uoo)2 (AP/AW), where Vp and U^ are the velocities issuing from the blowing slot and in the freestream and Ap and Aw are the areas of the blowing slot and the half-wing model, respectively. In this study, the momentum coefficient varied in the range of 0.025-0.181, and the reduced frequencies vary between 1.25 and 5.0, Figure la shows the direction and location where the blowing perturbation is applied. In Fig. Ib, the half-delta vfing model, with 75-deg sweep and 25-deg upward-beveled leading edge, is situated on a platform having an elliptic leading edge profile with a major/minor axes ratio of 5:1. The model is located within the region where the static pressure indicates only a negligible streamwise pressure gradient in presence of the platform. A circular disk is designed to rotate relative to the wing model to align the blowing direction with the vortex core above the wing surface. A hole is drilled through the thickness of the circular disk to align with the vortex core direction when viewed from the wing upper surface. Fluid issues from this blowing slot, 0.5 mm inner diameter, into and along the vortex core driven by a stepping motor pumping system. The AOA can be altered simply by screwing each hole to the wing model with the wing tip as a rotating center. Food-coloring dye, flowing naturally from another tiny slot very close to the wing apex, has been used as a tracer in the vortex core to identify the transient location of vortex breakdown during and after each blowing event. The vortex breakdown is qualitatively characterized by the