Five Hole Probe Exploration of the Transonic Vortical Flow Above a Delta Wing

摘要

The leeward side flow of a 65 deg swept delta wing operating at moderate anglesof attack in the transonic speed range has been investigated by means of a fast response five hole probe. Experiments were performed at free stream Mach numbers of 0.6 and 0.8, with angles of attack of 10 deg and 15 deg. Cross-flow planes containing the vortex were measured at 50%, 70%, 140% and 150% of the root chord. The development of total pressure, the static pressure, the flow-wise vorticity and the azimuthal vorticity above and behind the wing are discussed and compared with previous investigations. Above the wing, the measured conical Mach number and density distributions are also presented in order to validate previous and future surface reflective visualization and related optical measurement methods. The current measurements in combination with previous experimental investigations reveal that a shock occur above the wing underneath the vortex at an angle of attack of 15 deg and a Mach number of M = 0.8 at about 65% of the the local semi-span. Further aft, the vortex changes from a jet-like to a wake-like velocity distribution, indicating a change of the flow leading up to vortex breakdown. There are also indications that turbulence or instabilities in the flow play important roles in the development of the time-averaged total pressure close to the vortex core. Some suggestions concerning the interpretation of results from five hole probe surveys in transonic flow are finally presented, together with some proposals for improvements of the azimuthal vorticity calculations.