Calculations of the velocity profiles in the vicinity of a sphere at intermediate Reynolds numbers; consequences for the micro-anemometer calibration unit |
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Authors: | M J F P Pluijm A M van den Kieboom and C H Massen |
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Institution: | (1) Faculty of Physics, University of Technology, P.O. Box 513, Eindhoven, The Netherlands |
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Abstract: | The axi-symmetrical steady viscous flow past a sphere in a uniform flow in a cylinder of finite length is calculated with the finite element method and a penalty function approach. Our numerical results for the drag coefficient, the standing eddy length and the angle of flow separation as a function of Reynolds number agree well with literature. The velocity profiles in the vicinity of the sphere show that for distances larger than 3 × radius of the sphere and angles much larger than the angle of flow separation the influence of the sphere is less than 5%. The velocity at the position of our micro-anemometer is equal to the velocity generated by the calibration unit within 5%. From the numerical calculations the conclusion can be drawn that spherical micro-anemometers with diameters up to 20% of the diameter of the calibration unit can be calibrated. |
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