Effects of multiple subcavities with floor subcavity in supersonic cavity flow

Abstract

Experimental and computational analysis has been carried out by many researchers on supersonic cavity flow, but detailed analysis based on Rossiter's model still requires some insight. In the current study an open rectangular cavity with a length to depth ratio of 2 (L/D = 2) and Mach number at the inlet as 1.71, was considered as a baseline configuration for experimental analysis. Statistical techniques such as power spectral density (PSD), correlation, and overall sound pressure level (OASPL) were carried out on the unsteady pressure data, to analyze the aero-acoustic flow physics. High-speed schlieren images were processed to obtain spatially coherent modes by proper orthogonal decomposition (POD). The analysis was extended for different dimensions of subcavities on the aft, floor, and front wall. This detailed analysis of these configurations with different dimensions and combinations revealed the various flow features and mode frequencies in supersonic cavity. As the front wall subcavity act as a passive control device, reducing the overall sound pressure level inside the cavity whereas, the aft wall subcavity acts as a passive resonator with distinct harmonic fluid-resonant modes, a similar phenomenon was observed for floor subcavity at different locations. A novel method was employed to analyze Rossiter's model and its applicability in estimating experimental modes was verified, as it accurately predicted the dominant frequencies with a maximum of 2.74% uncertainty among all the configurations.

Keywords

• Supersonic cavity flow
• Fast Fourier transform
• High speed schlieren
• Proper orthogonal decomposition
• Rossiter's feedback mechanism