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Wind and Structures
  Volume 12, Number 5, August 2009 , pages 441-455

Spanwise coherent structure of wind turbulence and induced pressure on rectangular cylinders
Thai-Hoa Le, Masaru Matsumoto and Hiromichi Shirato

    Studying the spatial distribution in coherent fields such as turbulence and turbulence-induced force is important to model and evaluate turbulence-induced forces and response of structures in the turbulent flows. Turbulence field-based coherence function is commonly used for the spatial distribution characteristic of the turbulence-induced forces in the frequency domain so far. This paper will focus to study spectral coherent structure of the turbulence and induced forces in not only the frequency domain using conventional Fourier transform-based coherence, but also temporo-spectral coherence one in the time-frequency plane thanks to wavelet transform-based coherence for better understanding of the turbulence and force coherences and their spatial distributions. Effects of spanwise separations, bluff body flow, flow conditions and Karman vortex on coherent structures of the turbulence and induced pressure, comparison between turbulence and pressure coherences as well as intermittency of the coherent structure in the time-frequency plane will be investigated here. Some new findings are that not only the force coherence is higher than the turbulence coherence, the coherences of turbulence and forces depend on the spanwise separation as previous studies, but also the coherent structures of turbulence and forces relate to the ongoing turbulence flow and bluff body flow, moreover, intermittency in the time domain and low spectral band is considered as the nature of the coherent structure. Simultaneous measurements of the surface pressure and turbulence have been carried out on some typical rectangular cylinders with slenderness ratios B/D=1 (without and with splitter plate) and B/D=5 under the artificial turbulent flows in the wind tunnel.
Key Words
    coherent structure; spanwise coherence; wind turbulence; surface pressure; continuous wavelet transform; wavelet coherence; time-frequency analysis.
Thai-Hoa Le; Department of Engineering Mechanics and Automation, Vietnam National University, Hanoi 144 Xuan Thuy, Cau Giay, Hanoi, Vietnam
Masaru Matsumoto and Hiromichi Shirato; Department of Civil and Earth Resources Engineering, Kyoto University, Kyoto-Daigaku-Katsura Campus, Nishikyo-ku, Kyoto 611-8540, Japan

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