Numerical method to compute acoustic scattering effect of a moving source.

Hao Song,Yalin Pan,Mingxu Yi,Jun Huang,Dawei Liu

doi:10.1186/s40064-016-3080-x

Abstract

In this paper, the aerodynamic characteristic of a ducted tail rotor in hover has been numerically studied using CFD method. An analytical time domain formulation based on Ffowcs Williams–Hawkings (FW–H) equation is derived for the prediction of the acoustic velocity field and used as Neumann boundary condition on a rigid scattering surface. In order to predict the aerodynamic noise, a hybrid method combing computational aeroacoustics with an acoustic thin-body boundary element method has been proposed. The aerodynamic results and the calculated sound pressure levels (SPLs) are compared with the known method for validation. Simulation results show that the duct can change the value of SPLs and the sound directivity. Compared with the isolate tail rotor, the SPLs of the ducted tail rotor are smaller at certain azimuth.

Highlights

In recent decades, noise pollution has become a major issue of concern and the noise generation mechanisms have been investigated widely
Based on the CFD method, aerodynamic characteristic of the TsAGI ducted tail rotor are discussed, and the results are compared with vortex theory and momentum source method for validation
It can be used as boundary condition for the thin-body boundary element method (BEM)

Summary

Introduction

Noise pollution has become a major issue of concern and the noise generation mechanisms have been investigated widely. Fans and others has great influence on the aeroacoustic research (Polacsek et al 1999; Greenwood and Schmitz 2014; Kingan 2014; Johnson 1980; Mao et al 2015) In these applications, the direct sound field and scattering effect are always considered to assess the acoustic impact of sound sources (Mouille 1970, 1986; Lowson 2015). Due to the effect of the duct, the slipstream pattern and aerodynamic characteristic of ducted tail rotor are different from the conventional open-type rotor It can reduce the risk of component damage and enhance the operational safety. The analysis of the aerodynamic noise of the ducted tail rotor is the main topic for this paper

Objectives

Conclusion