Stereoscopic PIV on a delta wing in supersonic flow

Abstract

Ever since the 1950s delta wings are being used as an efficient planform for supersonic flight. Over time extensive research on the aerodynamics of this type of wings has been performed using many different measurement techniques. Due to technical difficulties, measurements on delta wings in a supersonic flow are still scarce and often limited to qualitative data only. The addition of PIV as a diagnostic tool in aerodynamics opened doors for new measurements. Nowadays PIV is a well-established non-intrusive measurement method that is being applied in large scale subsonic industrial facilities on a regular basis and in research facilities in all flow regimes. Stereoscopic PIV measurements on delta wings are done previously in sub- and transonic flow, and one 2C-PIV experiment has been done on a delta wing in supersonic flow at moderate angle of attack. The motivation of the current investigation is to perform stereo-PIV measurements around a sharp-edged delta wing in a supersonic flow at high angle of attack using the latest advances in PIV. Furthermore an extension is made to a similar setup in the industrial facility of DNW-SST on the EUROSUP model. The flow around a delta wing is succesfully described at different Mach numbers and for several angles of attack. A spanwise scan using individual measurement planes in streamwise orientation has been made, which are combined to construct a mean flow field in the complete volume. The response of the tracer particles is measured by an oblique shock test, from which the slip velocity with respect to the flow and the drift from the flow path, due to their inertia, is determined. Schlieren, shadowgraphy and oil flow visualisation are applied to give additional information on the flow. Several flow features have been measured by PIV. As expected a vortex is present on the leeward surface of the wing. Due to the large deflection of the flow on the windward surface, a detached shock is present before the leading edge extending to the expansion side of the wing. Attached to the vortex an inboard shock wave has been measured. Furthermore the flow field appeared to be conical, i.e. the flow variables are constant on rays emerging from the apex. A similar stereo-PIV setup has been succesfully applied in the industrial supersonic facility SST at DNW using a high-repetition acquisition system including a model sliding mechanism to increase data production. However, due to the large size of the seeding particles in this campaign, the data generated in this tunnel remains questionable, and a thorough investigation on the seeding production is necessary to acquire reliable PIV data in this facility.