The Study of Prediction Method on Propeller Broadband Noise
In this paper, a prediction method of hydrofoil broadband noise is developed based on large eddy simulation (LES) methods and Ffowcs Williams- Hawkings (FW-H) equations. The broadband noise of an airfoil is calculated and the comparison of computed and me
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Abstract In this paper, a prediction method of hydrofoil broadband noise is developed based on large eddy simulation (LES) methods and Ffowcs WilliamsHawkings (FW-H) equations. The broadband noise of an airfoil is calculated and the comparison of computed and measured sound pressure spectra shows good agreement over approximately a decade of frequency. The broadband noise of five different hydrofoils are calculated and presented in this paper. The relationship between the broadband noise of hydrofoils and the hydrofoil thickness and camber distributions are discussed. An optimized hydrofoil is presented in this paper for which the broadband noise is about 4 dB lower than NACA-66mod foil.
1 Introduction The propeller broadband noise spectrum is contributed by the sound radiation of the trailing edge flow of propeller blade and interaction between tip vortex and blade. Turbulence with various scales eddies in these flows is directly related to generation of the noise. So, how to obtain the detail structures of flow field around the propeller becomes one of the key points in propeller broadband noise prediction by numerical methods. Large eddy simulation (LES) method can get adequate flow details with relatively high accuracy, as well as satisfy the requirement of the sound source simulation calculation for noise prediction. Wang and Moin (2000) used numerical methods to simulate trailing edge flow, and then the trailing edge noise was predicted by the acoustic disturbance Y. Chen (&) D. Tang Z. Liu H. Sun China Ship Scientific Research Center, Wuxi, China e-mail: [email protected] Y. Chen D. Tang Z. Liu H. Sun National Key Laboratory on Ship Vibration & Noise, Wuxi, China
Y. Zhou et al. (eds.), Fluid-Structure-Sound Interactions and Control, Lecture Notes in Mechanical Engineering, DOI: 10.1007/978-3-642-40371-2_34, Springer-Verlag Berlin Heidelberg 2014
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equations. Moreauy used LES methods to calculate foil flow field, then solved the foil trailing edge noise by FW-H equations, and the comparison of computed and experimental results shows good agreement. In conclusion, the numerical prediction method of broadband noise using LES combined with acoustical methods have already been studied and validated in different fields. In order to predict the hydrofoil broadband noises, the turbulent flow around a two-dimensional hydrofoil is calculated as a time series by LES, and then the broadband noise is predicted using the FW-H equations. The broadband noises of five different two-dimensional hydrofoils are calculated, and the relationships between the broadband noise of hydrofoil and the hydrofoil thickness and camber distributions are discussed.
2 LES Numerical Calculation Method The basic assumptions of LES are that: (1) transport is largely governed by large— scale unsteady flow and these structures can be computationally resolved; (2) small—scale flow features can be under taken by using appropriate subgrid scale turbulence models. In LES, the motion is separated into small and l
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