Effect of clustering on linear plug nozzle flow field for overexpanded internal jet

Abstract

Experiments were carried out to analyze the flow field development of a linear plug nozzle wherein the internal nozzle was operating in the overexpanded regime. Steady and unsteady pressure measurements were taken along with the schlieren and oil flow visualization techniques to describe the flow field. Over the range of pressure ratios considered, the overexpanded shock pattern from the internal nozzle has been explained with regard to differential end conditions on either side of the core jet. The unsteady characteristics of the pressure fluctuations have been discussed with respect to the foot of the overexpansion shock on the plug surface. The effect of internal nozzle clustering on the plug nozzle flow field has been studied for two different cluster nozzles. The cluster module jet wave interactions along the spanwise direction have been explained with respect to the limiting streamline pattern on the plug surface. In addition to these, the base flow characteristics for these overexpanded internal nozzle pressure ratios have been discussed for two different truncated plug lengths.