Numerical study of flow through planar double divergent nozzles

Abstract

Double Divergent Nozzle is a type of altitude compensating nozzle having less weight and minimum modifications when compared to other altitude compensating nozzle concepts. Planar double divergent nozzle is similar to a dual bell nozzle but, it is having a rectangular cross section. The present study involves numerical analysis of a planar double divergent nozzle and its comparison with a single divergent nozzle using ANSYS Fluent Software. The flow is simulated over various Nozzle Pressure Ratios (NPRs) and corresponding wall static pressure and specific impulse are studied. A sneak transition can be observed when the flow changes from low altitude mode to high altitude mode. The transition occurs early for double divergent nozzle having low NPR and vice versa. The wall static pressure variation shows a strong dependence of inflection angle on pressure variation, separation location and recirculation regions inside the nozzle.