Numerical Analysis of Transient Gas Jet and Wall Impinging Jet by Discrete Vortex Method

Generally speaking, it is very difficult to clarify the growth process of large-scale vortices in a transient gas jet. The vortices have a great effect on the mechanism of mixture formation between the jet itself and the surroundings. The objective of the study presented here is the clarification of this mechanism in both a free jet and a jet impinging on a flat wall by means of the flow visualization of 2D images obtain by a thin sheet of laser light in experiments and numerical analysis by the discrete vortex method. The mechanism of the vortex growth and the coherent structure of vortices entraining the surroundings are clarified in the case of a free jet. In the wall impinging jet, the structure inside the jet is divided into three regions, namely, free jet region, impingement region and wall-main jet region. The results of the numerical analysis agree qualitatively with the experimental data.