Improved empirical prediction method for impinging acoustic sources distributed around interactive structures

Abstract

An improved empirical prediction method has been developed to predict the noise generated by impinging acoustic sources of flight vehicles. A representative empirical prediction method is the second distributed source method (DSM-II) in the report NASA SP-8072. However, since DSM-II is based on specific experimental data, it has limitations of not being able to perfectly reflect some acoustic phenomena such as impingement, reflection, and diffraction effects induced by interactive structures. In this study, we introduce some additional experimental data and a simple theory to the conventional method, and propose an improved empirical method that could reflect the above acoustic phenomena also. First, we describe the improved method that includes the impingement effect and validate the results for the Korean Sounding Rocket-III (KSR-III) in terms of overall sound pressure level (OASPL) and sound spectrum. Next, we expand this method to the case of a high speed vehicle surrounded by a canister that generates additional acoustic phenomena such as reflection and diffraction effects. We inspect the canister effects on the vehicle as the height increases, from the view point of OASPL and spectrum. Finally, the results are discussed.