ISSN:
1432-2153
Keywords:
Blast wave
;
N-wave
;
Dispersed wave
;
Random choice method
;
Vibrational relaxation
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
,
Technology
Notes:
Abstract Effects of viscosity and vibrational nonequilibrium on the profile of a weak, spherical N-wave in air are experimentally and numerically studied. Weak blast waves were generated, in a quiescent air dome, by spark discharges and exploding wires and observed by high frequency response microphones over 40 meters. Some similarity relationships were obtained from the blast wave experiments. For observed N-waves having less than 100 Pa peak overpressure, the peak overpressure Δp f and the duration of the positive phaset d+ are found to vary with the radial distance from the sourcer as Δp f ∝r −1.38 andt d + ∝r 0.19, whilst the rise time of the blast wave Δt f linearly increases with distance. Similar trends were also found for the negative phase of the blast wave. Numerical simulations were carried out to compare with the blast wave data. The Navier-Stokes equations for spherical symmetric flows were solved by coupling with a relaxation equation for vibrational excitation of oxygen using the random choice method (RCM) adapted to supercomputing with an operator splitting technique. The resultant N-wave profiles are in good agreement with the experimental results. The numerical results clearly indicate that the wave-easing process due to the dispersive effect of vibrational relaxation plays a dominant role in determining the rise time of the N-wave.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01414906
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