Similarity and asymptotic analysis for gun-firing aerodynamics

Abstract

An experimental observation of the flow following the discharge of firearms has been carried out by means of ultra-high-speed visualization. The theory of similarity has been applied in order to define the rules governing the tests on models, chiefly for gun firing-air intake interference problems. When the blast effect predominates, no geometric similarity is required between the simulation gun and the simulated one, so the model and the simulation gun can have different scales. It is shown that the main parameter characterizing the blast effect is the energy rate at the muzzle which can be considered as a point source of energy caused by a very hot gas. So, the muzzle wave tends asymptotically toward the blast wave of a non-instantaneous intense point explosion. Specific experiments confirm this assertion. All previous results allow a theoretical modelling of gun-firing aerodynamic phenomena which will be presented in a separate paper.