Computing Aerodynamically Generated Noise

Abstract

In contrast to computational aerodynamics, which has advanced to a fairly mature state, computational aeroacoustics (CAA) has only recently emerged as a separate area of study. Following a discussion of the classical field of aeroacoustics as introduced by Lighthill, the paper provides an overview and analysis of the problems associated with utilizing standard computational aerodynamics procedures for acoustic computations. Numerical aspects of computing sound-wave propagation are considered, including assessments of several schemes for spatial and temporal differencing. Issues of particular concern in computing aerodynamically generated noise, such as implementing surface and radiation boundary conditions and algorithms for predicting nonlinear steepening and shocks, are discussed. In addition, the paper briefly reviews alternatives to the conventional finite-difference schemes, such as boundary-element and spectral methods and the uncommon lattice-gas method. MODERN AEROACOUSTICS Sir James Lighthill (1993b) has stated that the aeronautical community has recently entered into the second Golden Age of Aeroacoustics. The first of these eras, as defined by Lighthill, focused on the problems of jet noise and jet engine noise, and lasted from the late 1940s until the mid 1970s. By that time, high-bypass-ratio turbine engines had become the standard for all new transport aircraft, and the initially excessive noise produced by turbojets had been

Aero-acoustic computations of wind turbines

“…Some recent reviews on CAA can be found by Wells et al [47], Wang et al [49] and Colonius et al [41,48].…”

Adaptive Mesh Refinement for Computational Aeroacoustics

“…(2) regridding the computational domain according to a selected regridding criterion; All AMR operations have been discussed before except a new one, the AMR ghost construction operation, appearing in step (4). Its details are introduced in the next paragraph.…”

“…With a reduction target of perceived noise level of 50% by 2020 [2], computational aeroacoustics (CAA) is being used with increasing frequency in studying the physics of aerodynamically generated noise. Various attempts have been made to apply CAA methods to airframe/engine noise study both in the EU countries and in the US [3,4]. The general objectives of CAA focus on the prediction of aerodynamic sound sources and the propagation of the generated sound.…”

A New Flexible Global Positioning System (GPS) Constellation Sustainment Strategy

“…Recent reviews of computational aeroacoustics have been given by Tam [2] and Wells and Renaut [3] who discuss various numerical schemes currently popular in CAA. These include among others the dispersionrelation-preserving (DRP) scheme of Tam and Webb [4], the method for minimization of group velocity errors (MGV) due to Holberg [5], the family of high-order compact differencing schemes of Lele [6] and Essentially Non-Oscillatory (ENO) schemes [7].…”