Weak spherical shock-wave transitions of N-waves in air with vibrational excitation
Abstract
The effects of vibrational excitation on the shock-wave transitions of weak spherical N-waves are investigated for overpressures below 100 Pa. The spherical N-waves are generated by using sparks and exploding wires as sources in a still-air dome of 40-m diam. The pressure profiles of the N-waves are observed by using high-frequency microphones located at several positions (10-30 m) from the source. It is found that the measured rise times of the N-waves for overpressures of 5-30 Pa and half-duration of 50-120 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 real-gas effects on the rise times of weak spherical N-waves, the compressible Navier-Stokes equations are solved numerically, including vibrational-relaxation relations for oxygen, using a pressurized air-sphere explosion as a model. By employing the random-choice method with an operator-splitting technique, the effects of artificial viscosity appearing in finite-difference 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;
- Navier-Stokes Equation;
- Nitrogen;
- Oxygen;
- Sparks;
- Fluid Mechanics and Heat Transfer