Surface-Flow Visualization and Pressure-Sensitive Paint Measurements in the Large-Scale Low-Boom Inlet

Abstract

The local flowfield effects of vortex generators on a supersonic axisymmetric-relaxed external compression inlet have been investigated with surface-flow visualization and pressure-sensitive paint measurements. This inlet entails a mechanically simple design for providing a high-recovery/low-distortion flowfield and low sonic-boom signature. A set of vortex generators was incorporated into the design both upstream of the terminating normal shock and downstream inside the subsonic inlet diffuser for reducing separation zones near the shock/boundary-layer interaction and reducing radial distortion at the engine face, respectively. The inlet centerbody and downstream diffuser vortex-generator regions were imaged during wind-tunnel testing internally through the inlet cowl with a camera housing attached to the cowl. Surface-flow visualization revealed separated regions along the inlet centerbody for large mass-flow rates without vortex generators. Upstream vortex generators did reduce separation in the subsonic diffuser, and a unique perspective of the flowfield produced by the downstreamvortex generators was obtained. In addition, pressure distributions on the inlet centerbody, vortex generators, and struts were measured.