Distribution of Acoustic Power Spectra for an Isolated Helicopter Fuselage

A.N Kusyumov,A.S Batrakov,G Barakos,L.I Garipova,S.A Mikhailov,P Dančová,M Veselý

doi:10.1051/epjconf/201611402062

Abstract

The broadband aerodynamic noise can be studied, assuming isotropic flow, turbulence and decay. Proudman’s approach allows practical calculations of noise based on CFD solutions of RANS or URANS equations at the stage of post processing and analysis of the solution. Another aspect is the broadband acoustic spectrum and the distribution of acoustic power over a range of frequencies. The acoustic energy spectrum distribution in isotropic turbulence is non monotonic and has a maximum at a certain value of Strouhal number. In the present work the value of acoustic power peak frequency is determined using a prescribed form of acoustic energy spectrum distribution presented in papers by S. Sarkar and M. Y. Hussaini and by G. M. Lilley. CFD modelling of the flow around isolated helicopter fuselage model was considered using the HMB CFD code and the RANS equations.

Highlights

For a conventional helicopter, there are two fundamental elements that contribute to the generation of near-field and far-field noise, the main rotor and the tail rotor [1]
In the present work the value of acoustic power peak frequency is determined using a prescribed form of acoustic energy spectrum distribution presented in papers by S
There are two fundamental elements that contribute to the generation of near-field and far-field noise, the main rotor and the tail rotor [1]

Summary

Introduction

There are two fundamental elements that contribute to the generation of near-field and far-field noise, the main rotor and the tail rotor [1]. The total acoustic power radiated from embedded finite regions of turbulence contained within an infinite volume of compressible fluid, is a function of the local time-averaged kinetic energy of the turbulence per unit volume, k, and the time averaged rate of dissipation of the kinetic energy per unit volume, H Another aspect, is the broadband acoustic spectrum and the distribution of acoustic power over a range of frequencies. A simple approach to estimate acoustic emission of flying vehicle for turbulent flows, assumes that the emitted noise does not have any distinct tones, and that the sound energy is continuously distributed over a broad range of frequencies. In this case the broadband noise power, can be estimated from RANS equations using the mean flow.

Total radiated acoustic power

Proudman’s constant

Turbulent reference frequency

Numerical simulation of flow around an isolated helicopter fuselage

Conclusions and future work