An experimental study of the effects of turbulence on the rise time of shock waves propagation in the atmosphere

Abstract

As a shock wave propagates through the atmosphere various effects change the waveform. Nonlinear steepening tends to shorten the rise time of the leading and trailing edges of the shock. Frequency dependent dissipation and scattering from atmospheric turbules tend to lengthen the rise time. Simultaneous measurements of turbulence (i.e., wind velocity and temperature fluctuations) and shock waveforms resulting from supersonic projectiles were obtained and analyzed. The shock wave measurements required dielectric capacitive microphones specifically designed for this application. The simultaneous measurement of turbulence parameters and shock waveforms are the first reported and allow for the comparison between measured rise times and those computed assuming turbulence is the dominant mechanism affecting the rise time. The measured rise times are also compared to those computed considering only relaxation effects (ignoring turbulence). The rise times computed from those two different mechanisms are similar in magnitude; both agree reasonably well with measurements. [Work supported by ARO.]