Experimental investigation of the impact of cross-wire fitted CD nozzle on supersonic flow field

This experimental study aims to address the application of the supersonic CD nozzle with a passive control to optimize aircraft performance and reduce engine noise emission. Supersonic jet decay analysis is a crucial technique for studying the behavior of jets as they interact with their surrounding air. The jet flow leaving the nozzle mixes with the ambient air by introducing passive control strategies for controlling jet noise and enhance the mixing. This modification of nozzle exit geometry aims to minimize the jet potential core length resulting in reduced noise level for developing quieter supersonic engines. This study examines the centerline axial jet decay and radial jet spreading of a jet flow from a CD nozzle with a cross-wire (controlled jet) compared to the baseline (uncontrolled jet). The nozzle was operated at various nozzle pressure ratios (NPR), resulting in near-optimal, over-expanded, and under-expanded conditions for design Mach numbers of 1.5 and 1.75. The shock cell structure was captured using the Schlieren imaging to envisage jet decay characteristics. The CD nozzle with a cross-wire demonstrates superior performance compared to the baseline, as it enhances jet mixing characteristics and reduces the length of the supersonic jet core by approximately 7% to 43%. The cross-wire as a passive control method is more effective at higher NPRs for Mach 1.5 and lower NPRs for Mach 1.75. The study investigated the effectiveness of cross-wires in reducing the supersonic jet core length at the nozzle exit, while maintaining a blockage ratio of no more than 1.8%.