Separation behaviour in front of a two-dimensional fence |
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| Institution: | 1. Key Laboratory of Meteorological Disaster of Ministry of Education (KLME), Joint International Research Laboratory of Climate and Environment Change (ILCEC), Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044, China;2. Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, NOAA/OAR/Earth System Research Laboratory/Global Systems Division, Boulder, CO, United States;3. Department of Mathematics and Statistics, University of Reading, Reading, UK;4. Division for Data Assimilation (FE12), Deutscher Wetterdienst, Offenbach, Germany;1. Department of Medical Parasitology, Wannan Medical College, Wuhu 241002, Anhui, China;2. School of Medicine, Anhui University of Science & Technology, Huainan 232001, Anhui, China |
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| Abstract: | The wall-bounded turbulent shear flow in front of a two-dimensional fence was investigated experimentally. In this prototype of a rapidly separating flow the assumptions for a first-order boundary-layer theory cease to apply. This is caused by the streamline curvature, the ensuing pressure gradient normal to the wall and the large vertical velocity component v in front of the fence. For the present experiment, where the ratio of the boundary layer thickness δ0 measured without the fence and the fence height h is 0.82, the time mean separation length upstream of the fence lf is 0.65h. However, instantaneous reverse flow events can be detected up to 4 mean separation lengths lf upstream of the fence. The maximum value of the reverse flow factor χw is 95% indicating a strong reverse flow region. The experiments were performed by LDA and a wall pulsed-wire skin-friction meter. They show the limits of first-order boundary-layer theory and provide the first comprehensive data set of mean and fluctuating velocities and of wall shear-stress for this type of separating flow. |
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