Quantification of swash flows using video-based particle image velocimetry |
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| Institution: | 1. CIRI, University of Bologna, via Terracini 28, 40136 Bologna, Italy;2. DICAM, University of Bologna, viale Risorgimento 2, 40134 Bologna, Italy;1. Ocean College, Zhejiang University, Hangzhou 310058, PR China;2. The State Key Laboratory of Fluid Power Transmission and Control, Zhejiang University, Hangzhou 310027, PR China;3. Department of Mechanical Engineering, National University of Singapore, 117575 Singapore, Singapore;4. Deepwater Technological Centre, Det Norske Veritas Pte Ltd., 118224 Singapore, Singapore;5. Nanyang Environment and Water Research Institute and School of Civil and Environmental Engineering, Nanyang Technological University, 639798 Singapore, Singapore;6. Maritime Research Centre, School of Civil and Environmental Engineering, Nanyang Technological University, 639798 Singapore, Singapore;1. Institute of Fluid Mechanics and Aerodynamics, Technische Universität Darmstadt, Darmstadt, Germany;2. Department of Mechanical and Materials Engineering, Queen?s University, Kingston, Canada |
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| Abstract: | Understanding of fluid flows and sediment transport in the foreshore has been severely hampered by the difficulty of obtaining swash flow velocity measurements in this dynamic and extremely shallow region. We present a digital imaging method, known as particle image velocimetry (PIV), to quantify the horizontal flow structure of swash. This technique exploits similar patterns of image intensity in multiple images sampled sequentially to identify spatial offsets corresponding with maximum correlations between image subregions. These offsets are used in conjunction with the sampling interval to derive velocity vectors describing the horizontal flow structure. Pre-processing methods to geo-rectify oblique imagery to a planar surface and post-processing methods of correcting spurious vectors are described. The PIV method overcomes many of the limitations of in situ sampling of swash flows and is shown consistent with results from a previously tested remote sensing technique for measuring swash edge velocities. In general, this technique provides a unique capability for spatially extensive and well-resolved quantification of swash flows. |
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