Accession Number : ADA135903

Title :   Random Choice Solutions for Weak Spherical Shock-Wave Transitions of N-Waves in Air with Vibrational Excitation.

Descriptive Note : Interim technical rept.,


Personal Author(s) : Honma,H ; Glass,I I

PDF Url : ADA135903

Report Date : Jul 1983

Pagination or Media Count : 114

Abstract : In order to clarify the effects of vibrational excitation on shock-wave transitions of weak, spherical N-waves, which were generated by using sparks and exploding wires as sources, the compressible Navier-Stokes equations were solved numerically, including a one-mode vibrational-relaxation equation. A small pressurized air-sphere explosion was used to simulate the N-waves generated from the actual sources. By employing the random-choice method (RCM) with an operator-splitting technique, the effects of artificial viscosity appearing in finite-difference schemes were eliminated and accurate profiles of the shock transitions were obtained. However, a slight randomness in the variation of the shock thickness remains. It is shown that a computer simulation is possible by using a proper choice of initial parameters to obtain the variations of the N-wave overpressure and half-duration with distance from the source. The calculated rise times are also shown to simulate both spark and exploding-wire data. It was found that, in addition to the vibrational-relaxation time of oxygen, both the duration and the attenuation rate of a spherical N-wave are important factors controlling its rise time. The effects of the duration and the attenuation rate of a spherical N-wave on its rise time, which are designated as the N-wave effect and the nonstationary effect, respectively, are discussed in more detail pertaining to Lighthill's analytical solutions and the RCM solutions for nonstationary plane waves and spherical N-waves. (Author)

Descriptors :   *Shock waves, *Sonic boom, Transitions, Wave equations, Atmospheric disturbances, Vibration, Excitation, Exploding wires, Overpressure

Subject Categories : Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE