Effect of Nozzle Geometry on Flowfield for High Subsonic Jets

Abstract

The present Paper aims to present a comparative study of the external and internal flow characteristics through an axisymmetric circular convergent nozzle, a nonserpentine convergent nozzle with an elliptic exit, and a shallow single serpentine convergent nozzle with an elliptic exit under the fully expanded condition at a nozzle pressure ratio of 1.6. The static wall pressure measurements reveal that, due to the axisymmetric shape, the conventional circular nozzle shows symmetric jet development. However, the flow through the serpentine nozzle follows its curvature, making the flow through it asymmetric. The upper and the lower walls have different flow expansion due to the secondary flow created by the wall curvature and transition. This asymmetric nature of the flow through the serpentine nozzle also vectors the external jet toward the lower wall. The saddle-shaped velocity profile is observed along the major axis plane of serpentine nozzle. The nozzles with elliptic exits show higher mass entrainment and faster velocity decay as compared to the conventional circular nozzle. The nonserpentine elliptic nozzle shows the maximum velocity decay with the fastest decay rate among the three nozzles considered. This nozzle also shows the maximum mass entrainment across its major as well as minor axes and thus reduces the length of the external jet more effectively.