
Accession Number : ADA135903
Title : Random Choice Solutions for Weak Spherical ShockWave Transitions of NWaves in Air with Vibrational Excitation.
Descriptive Note : Interim technical rept.,
Corporate Author : TORONTO UNIV DOWNSVIEW (ONTARIO) INST FOR AEROSPACE STUDIES
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 shockwave transitions of weak, spherical Nwaves, which were generated by using sparks and exploding wires as sources, the compressible NavierStokes equations were solved numerically, including a onemode vibrationalrelaxation equation. A small pressurized airsphere explosion was used to simulate the Nwaves generated from the actual sources. By employing the randomchoice method (RCM) with an operatorsplitting technique, the effects of artificial viscosity appearing in finitedifference 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 Nwave overpressure and halfduration with distance from the source. The calculated rise times are also shown to simulate both spark and explodingwire data. It was found that, in addition to the vibrationalrelaxation time of oxygen, both the duration and the attenuation rate of a spherical Nwave are important factors controlling its rise time. The effects of the duration and the attenuation rate of a spherical Nwave on its rise time, which are designated as the Nwave 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 Nwaves. (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