Numerical study of finite-amplitude source reconstruction

Abstract

Since its inception in the 1980s, near-field acoustic holography (NAH) has been widely used to determine structural source properties. More recently, it has also been used to determine aeroacoustic source behavior. Although several alternate forms of NAH have been developed, all are based on the (linear) Helmholtz equation and would presumably not function correctly for a finite-amplitude pressure wave propagating nonlinearly. However, when nonlinear effects or reconstruction distances are small, NAH may still be a useful tool for determining radiation characteristics of finite-amplitude sources such as jets and rockets. A two-dimensional numerical propagation scheme has been used to simulate simple noise propagation from an extended source to study the effect of nonlinearities on source reconstruction using NAH. Results from the study and their implication regarding the use of NAH for high-amplitude acoustic sources will be discussed.