Weak spherical shockwave transitions of Nwaves in air with vibrational excitation
Abstract
The effects of vibrational excitation on the shockwave transitions of weak spherical Nwaves are investigated for overpressures below 100 Pa. The spherical Nwaves are generated by using sparks and exploding wires as sources in a stillair dome of 40m diam. The pressure profiles of the Nwaves are observed by using highfrequency microphones located at several positions (1030 m) from the source. It is found that the measured rise times of the Nwaves for overpressures of 530 Pa and halfduration of 50120 microsec are much shorter than the rise times estimated from the theory of plane, fully dispersed waves with vibrational excitation of oxygen. To clarify the realgas effects on the rise times of weak spherical Nwaves, the compressible NavierStokes equations are solved numerically, including vibrationalrelaxation relations for oxygen, using a pressurized airsphere explosion as a model. By employing the randomchoice method with an operatorsplitting technique, the effects of artificial viscosity appearing in finitedifference schemes are eliminated and accurate profiles of shock transitions are obtained.
 Publication:

Shock Tubes and Waves
 Pub Date:
 1982
 Bibcode:
 1982stw..proc..342H
 Keywords:

 Molecular Excitation;
 Overpressure;
 Shock Fronts;
 Shock Wave Interaction;
 Sonic Booms;
 Spherical Waves;
 Computerized Simulation;
 Exploding Wires;
 Flow Equations;
 Flow Measurement;
 NavierStokes Equation;
 Nitrogen;
 Oxygen;
 Sparks;
 Fluid Mechanics and Heat Transfer