Characterization of Disturbance Resonance in Postshock of Blunt Body in Hypersonic Flow

A pitot probe is commonly used for the disturbance quantification of a hypersonic freestream, but the pitot results cannot reflect the actual disturbance amplitudes due to the turbulence/shock-wave interactions as well as the disturbance resonances. In this work, we characterize the disturbance resonance in the postshock zone of a blunt body using both experimental and theoretical approaches. A one-dimensional interference model with four traveling sound waves is proposed to simulate the resonance phenomenon due to the reflection between the detached shock and the wall of the pitot probe. Subsequently, the total pressure fluctuation on the surface and the density fluctuation in the space along the centerline are investigated using a pressure sensor and a noninvasive focused laser differential interferometer. Both the experimental results and theoretical analysis show the resonance mechanism on the surface is dominated by the interference between the initial diverging sound wave and the shock-reflected sound wave. In contrast, the stationary wave formed by the initial diverging sound wave and the body-reflected wave plays a leading role in the space. Finally, an equation is proposed to approximate the destructive resonant frequency in the space.