Randomchoice solutions for weak spherical shockwave transitions of nwaves in air with vibrational excitation
Abstract
In order to clarify the effects of vibrational excitation on shock wave transitions of weak, spherical Nwaves, which were generated by using sparks and exploding wires as sources, the compressible NavierStokes equations weresolvedd numerically, including a one mode vibrational relaxation equation. A small pressurized air sphere explosion was used to simulate the Nwaves generated from the actual sources. By employing the random choice method (RCM) with an operatorsplitting 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 randmness in the variation of the shock thickness remains. It is shown that a computer simulation is possible by using a proper coice 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 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 Nwave are important factors controlling its rise time.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 July 1983
 Bibcode:
 1983STIN...8410502H
 Keywords:

 Molecular Excitation;
 Plane Waves;
 Sonic Booms;
 Spherical Waves;
 Supersonic Transports;
 Finite Difference Theory;
 Molecular Relaxation;
 Shock Layers;
 Fluid Mechanics and Heat Transfer