Simulation of Back Pressure Effect on Behaviour of Convergent Divergent Nozzle

Abstract

In this research a simulation of steady flow of a gas through a convergent divergent nozzle which has a varying cross sectional area will be considered. The nature of the flow can be explained by considering how the flow and its characteristics in the nozzle changes as nthe back pressure Pb is decreased.The characteristics of gas flow i.e.(Mach number, static pressure, density, velocity magnitude and static temperature) distributions for the convergent divergent nozzle are implemented by using the ANSYS Fluent 12.1 software to solve the quasi-one dimensional nozzle flow.The reductions in the back pressure cannot affect conditions upstream of the throat. The nozzle is, therefore, choked. The shock wave increases the pressure, density and temperature and reduces the velocity and Mach number to a subsonic value, and as back pressure is further reduced to a certain value, the extent of the supersonic flow region increases, the shock wave moving further down the divergent portion of the nozzle towards the exit plane.