Numerical and experimental study on wave propagation in the open atmosphere

Abstract

In the present research works, wave propagation in the open atmosphere has been investigated both numerically and experimentally. Two-dimensional (2D) numerical code has been developed to solve the Euler equations for the upstream and downstream parameters during the shock wave propagation in the open atmosphere. It is observed that due to decay of the shock strength, all parameters (velocity, pressure and density) in the upstream of the shock wave are decreased as increasing the travel time of the wave in the open atmosphere. It is seen 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 shock wave with supersonic speed by rupturing different types of diaphragms. The properties of diaphragm are the major factors to generate shock wave in the shock tube. It is observed that the properties of diaphragm like toughness and brittleness are the best properties in the present case. In the present experiment, transparent Raksin sheet and used X-ray film are selected as the diaphragm where used X-ray film has the better rupturing quality as compare to Raksin sheet. For measuring the wave speed, a time measuring technique has been developed to measure the wave travel time in the 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 the wave propagation in the open atmosphere, the wave speed decreases and the decay of the wave strength is observed.