Numerical and Experimental Investigation of Shock wave Propagation in the Open Atmosphere

Abstract

Shock wave propagation in the open atmosphere has been investigated both numerically and experimentally. Three-dimensional numerical code has been used to solve the Euler equations for the upstream and downstream parameters during propagation in the open Atmosphere. It is observed that due to decay of the shock strength, all parameters (velocity, pressure and density) are decreased with increasing the travel time of the wave in the open Atmosphere. It is found from the numerical images that the propagation of the shock front in the open Atmosphere is spherical in shape. An experiment has been conducted by a horizontal shock tube to generate subsonic wave as well as supersonic shock wave by rupturing different types of diaphragm. The material properties of diaphragm are the major factor to generate shock wave in a shock tube. It is observed that the material properties like toughness and brittleness are the best properties in the present case. In this experiment, transparent Raksin sheet and used X-ray film earlier are used where X-ray film gives the better performance as compare to Raksin for better rupture. For measuring the wave speed in the open Atmosphere, a time measuring technique has been developed to measure the wave travel time in open Atmosphere and it is simple in use and accurate in measurement as compare to other complicated technique like wave visualization by High Speed Video camera. During wave propagation, the wave speed decreases with increasing the travel time in open Atmosphere. So decreasing the speed indicates that the decay of the wave strength is normal phenomena during propagation in the open Atmosphere. In the present study, both experimental and numerical techniques are applied successfully to determine the decay of the wave strength.