Investigation of 3D Shock Control Bumps for Transonic Buffet Alleviation

Abstract

View Video Presentation: https://doi-org.tudelft.idm.oclc.org/10.2514/6.2021-2558.vid This experimental study investigates the use of shock control bumps (SCBs) for controlling transonic buffet. Three-dimensional SCBs have been applied on the suction side of an OAT15A supercritical airfoil with the experiments conducted in the transonic-supersonic wind tunnel of TU Delft for fully developed buffet conditions (Ma=0.7, α=3.5° and Re=2.6·10^6). The effectiveness of the SCBs for different spanwise spacings (ranging from 20%c to 30%c) was verified using two optical techniques: schlieren visualization and particle image velocimetry (PIV). Both techniques showed the possibility of controlling buffet using such devices, resulting in a reduction of the unsteadiness present in the flow, both in terms of shock oscillation and pulsation of the separated area. A dedicated PIV investigation in a spanwise-chordwise measurement plane was then conducted in order to understand the effect of the spatial distribution of the bumps, focusing on the interaction of the shockwave structures along the span. The configuration with a spacing of ΔxSCB=25%c demonstrated to be the most efficient in reducing the transonic buffet oscillations.