Receptivity of the boundary layer on a Mach-4 elliptic cone to laser-generated localized freestream perturbations
Abstract
A repeatable, localized, laser-generated perturbation technique has been developed for application to supersonic and hypersonic boundary-layer receptivity experiments. The effect of the perturbation on the boundary layer on a five inch long, 4:1 elliptic cross-section cone has been examined in the Mach-4 Purdue Quiet-flow Ludwieg Tube at a freestream unit Reynolds number of 4.5 million per meter. The perturbation is formed using the focused beam from a frequency-doubled Nd:YAG laser and exists in the flowfield as a region of locally heated air called the thermal spot. The thermal spot convects downstream with the local velocity. Constant-temperature anemometer measurements have been used to characterize the perturbation, both the freestream and on the elliptic cone. Supplemental cold-wire constant-current anemometry measurements on the cone have allowed calculation of the mass-flux profiles in the elliptic-cone boundary layer. The mass-flux profiles are inflected on the cone minor axis; the boundary layer thickness is about 5 mm. The boundary-layer response to the thermal spot passage is largest and most complex near the boundary-layer edge. The mass-flux deviation introduced by the thermal spot passage is of the same magnitude as the local mean mass flux, both in the freestream and in the boundary layer.
Degree
Ph.D.
Advisors
Schneider, Purdue University.
Subject Area
Aerospace materials
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