An Investigation of Cavity Resonance and its Relationship to Store Force and Moment Loading

A store which is released from an internal bay is subjected to a highly unsteady flowfield which influences the release characteristics for the store. Pressure transducer information is often used to estimate store loading, although no direct correlation between the observed frequencies from the pressure transducers and the store loading has been developed. The relationship between the acoustic modes present in the cavity and the force and moment loading on a store released from a bay are investigated through a CFD study using the OVERFLOW 2.1 solver. The acoustic modes of the cavity are calculated from the pressure fluctuation histories along the cavity ceiling and walls. Empty cavity solutions are compared to the frequencies predicted by the Rossiter equation and to experimental data from the WICS database. Additionally, the cavity pressure fluctuation spectra are compared to the force and moment loading spectra for a store located in the cavity in both the carriage position and the shear layer. It is determined that the presence of a store in the cavity does not alter the fundamental acoustic modes in the cavity. Also, the store force and moment loadings are observed to correlate with the cavity pressure fluctuations. The original document contains color images.