Laboratory test bed for sonic boom propagation

Abstract

Varying ethanol concentration with depth, Hobaek et al. [AIP Proc. 838, 2006)] simulated the atmospheric sound speed profile scaled in a water tank and mimicked sonic boom propagation. Some limitations of their groundbreaking design included complexity, fragility, size, safety, one-dimensionality, tonal bursts instead of impulsive shocks, and the inability to scale density, absorption, turbulence, or other nonlinearities. Recognizing the time and cost savings of scaled overflight experiments in a laboratory environment, this work is meant to address certain limitations and investigate the Mach cut-off phenomena. Our primary advances are to use gel layers instead of fluid mixtures and lithotripter shock pulses. We defocused and modified a Dornier Compact S lithotripter to vary source angle in a 500-liter polycarbonate tank, measured shocks with a fiber optic hydrophone, and developed fluid-like gels with negligible shear-wave generation and robustness against cavitation. The sound speed, attenuation, inhomogeneity, and nonlinearity are adjustable within each gel layer. The result is a more flexible, controllable, and durable atmospheric analogue. [Work supported by the FAA. The opinions, findings, conclusions, and recommendations expressed in this material are those of the authors and do not necessarily reflect the views of ASCENT FAA Center of Excellence sponsor organizations.]