Three-Dimensional Wavelet Multi-resolution Analysis of Flow Structures Behind a Vehicle External Mirror
The three-dimensional orthogonal wavelet multi-resolution technique was applied to analyze flow structures of various scales around an externally mounted vehicle mirror. Firstly, three-dimensional flow of the mirror wake was numerically analyzed by using
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Abstract The three-dimensional orthogonal wavelet multi-resolution technique was applied to analyze flow structures of various scales around an externally mounted vehicle mirror. Firstly, three-dimensional flow of the mirror wake was numerically analyzed by using the large eddy simulation (LES). Then, the instantaneous velocity and vorticity were decomposed into the large-, intermediate-, and relatively small-scale components by the wavelet multi-resolution technique. It was found that a three-dimensional large-scale vertical vortex dominates the mirror wake flow and makes a main contribution to vorticity. Some intermediate- and relatively small-scale vortices were extracted and were clearly identifiable. Keywords LES analysis
Vehicle mirror Vortex Wake Wavelet multi-resolution
1 Introduction The aerodynamic noise and vibration caused by the vehicle door mirror has been much studied (Watkins and Oswald 1999), largely by numerical simulation (Ono et al. 1999). It is evident that the aerodynamic noise and vibration are strongly associated with the flow structures, and the unsteady behavior of the vortex causes the wind noise. Recently, the aero-acoustic characteristics of a vehicle door mirror were also studied by numerical simulation as well as experimental measurement (Reichl et al. 2005). Rinoshika et al. (2007) experimentally investigated the flow structure around an externally mounted vehicle mirror by the smoke-wire A. Rinoshika (&) Y. Zheng Department of Mechanical Systems Engineering, Yamagata University, Yamagata, Japan e-mail: [email protected]
Y. Zhou et al. (eds.), Fluid-Structure-Sound Interactions and Control, Lecture Notes in Mechanical Engineering, DOI: 10.1007/978-3-642-40371-2_10, Springer-Verlag Berlin Heidelberg 2014
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visualization technique and high-speed PIV technique. It is found that the length scales of separation region are generally insensitive to Reynolds number, and the size of vortices and the vorticity concentration increase with Reynolds number. Rinoshika and Watanabe (2010) also applied one-dimensional wavelet multiresolution technique to decompose Reynolds stress measured by high-speed PIV into various scales and analyzed the multi-scale flow structures behind a vehicle external mirror. But little attention has been paid to the analysis of the complex three-dimensional turbulent structures of various scales in the mirror wake from either the numerical or measurement data. This work aims to apply the three-dimensional orthogonal wavelet multi-resolution technique to decompose the complex turbulent structures of the mirror wake into multi-scale structures based on the large eddy simulation and to provide both quantitative and qualitative information on the three-dimensional flow structures of various scales for designing the mirror with lower dynamic drag and noise.
2 Approach of Numerical Simulation In this study, the commercial CFD software Fluent 6.3 is used to simulate the three-dimensional (3D) unsteady flow-field arou
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