Experimental investigation of flow unsteadiness over four types of spiked-blunt body at Mach 2.2

Abstract

Flow unsteadiness over four types of spiked-blunt body are investigated through wind tunnel experiments at a freestream Mach number of 2.2 at 0° and 4° angle of attack. The flow pulsation is visualized with high spatiotemporal resolution schlieren and then the shock-related unsteadiness is investigated through proper orthogonal decomposition (POD) method. Firstly, two special states in the suppressed pulsation mode are observed, namely the phase of withhold and the phase of smash. Flow over the standard aerodome spike will continuously transform between the two states, which can be distinguished from the distinct flow structures. Spectral analysis of unsteady pressure measurement detected the dominant frequencies of 2.2 kHz and 3.2 kHz for pointed spike and standard aerodome spike, respectively, and POD analysis further finds that the signal originates from the periodic motion of the aftershock. The large-amplitude flow pulsation (amplitude 0.23D) in typical pulsation mode is transformed into the high-frequency small-amplitude pulsation (amplitude 0.09D) in the suppressed mode. In addition, it is found that the variation of angle of attack makes little influence on the dominant frequency. And it is hard to find the main frequency of double/inverse aerodome spike, which indicates that the flow unsteadiness of different aerodome cases is not the same.