Unsteady Plume and Blast Field Generated by a Rocket Launch.

Abstract

Abstract : The basic fluid dynamic properties of the unsteady plume and blast field generated by ignition and launch of a rocket have been defined for the inviscid flowfield, both in terms of numerical and asymptotic solutions, subject to the assumption of spherical symmetry. The key role of the energy deposition rate in determining the boundary conditions controlling the subject problem has been discussed, as well as the general behavior of the principal structural features of the flowfield, i.e., the blast wave, contact surface plume Mach disc. The effects of turbulent mixing in the steady exhaust stream of the rocket (prior to ground impingement) on the rate and duration energy disposition at the ground surface have been shown to be dominant for low acceleration rates, but negligible for very high acceleration rates; the net effect appears to desensitize the dependence of energy deposition on vehicle acceleration in the range of intermediate rates. Numercial examples are presented to illustrate the temperature, pressure and thermochemical characteristics of the unsteady flow region between the blast wave and Mach disc. The extreme temperature jump which persists across the contact surface has been emphasized as a possible cause of instability of this surface and a driving mechanism for production of turbulence (in the absence of a velocity jump across the contact surface). An unsteady turbulent mixing layer analysis has been formulated to describe conduction and diffusion across the contact surface.