Attenuation of weak spherical shock waves in an accelerating flow

This study reports experimental investigations of a weak spherical shock wave propagating into an accelerating flow induced by a fan. Pressure measurements are conducted for shock waves propagating in both a static fluid and an accelerating flow, and comparisons reveal the influence of the accelerating flow on shock wave properties. The pressure jump of the shock wave is reduced after propagation in the accelerating flow, indicating attenuation of the shock wave. Greater attenuation is observed with increasing longitudinal velocity gradient in the shock propagation direction, corresponding to higher acceleration. When the velocity gradient becomes sufficiently large, the pressure jump is no longer identifiable, implying the disappearance of the shock wave. This attenuation is consistent with the one-dimensional model of a shock wave crossing a surface with an infinitely large velocity gradient, as the experimental conditions approach those of the model with increasing gradient. The attenuation does not affect the fluctuating behavior of the pressure jump. Additionally, the histogram of pressure jumps suggests that attenuation occurs for all shock waves propagating in the accelerating flow. The present experimental results support the shock wave attenuation predicted by the one-dimensional model, offering new insights into shock wave propagation in non-uniform flows.