EFFECTS OF THE LENGTH SCALE OF FREE-STREAM TURBULENCE AND CYLINDER SIZE ON LOCAL HEAT TRANSFER IN LAMINAR SEPARATED FLOWS |
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| Authors: | Shuichi Torii Wen-Jei Yang |
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| Institution: | 1. Department of Mechanical Engineering , Kagoshima University, Kagoshima , 890, Japan;2. Department of Mechanical Engineering and Applied Mechanics , University of Michigan , Ann Arbor, Michigan, 48109, U.S.A |
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| Abstract: | An experimental study has been conducted to investigate the combined influence of length scale of free-stream turbulence, A, and cylinder diameter, D, on heal transfer from slightly heated circular cylinders in cross flow. By using a hot-wire anemometer, spectrum analysis of its signal with a Fourier analyzer is employed to investigate the separated shear layer formed behind the circular cylinder. A resistance thermometer is used to measure the time-averaged temperature behind the cylinder and the power-spectral density of the temperature fluctuation in the thermal boundary layer. It is found that (I) the Nusselt number at the rear stagnation point varies with the relative scale A / D, at the same Reynolds number, (2) the laminar-to-turbulence transition region in the separated shear layer moves in the streamwise direction with the change in the length-scale ratio, and (3) a streamwise shift of the transition region in the separated shear layer causes a substantial increase in the power spectrum of the temperature fluctuation. A correlation equation with A/ Das a parameter is derived to predict the heat transfer rate at the rear stagnation point. |
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