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EXPERIMENT STUDY ON SEDIMENT INCIPIENCE IN backward-facing step flow

Journal of Hydrodynamics 2007年第2期19卷 173-179页

作者： LIU Chun-rong Huhe Aode TAO Long-bin Department of-Engineering Mechanics Hunan University Changsha 410082 China Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China School of Engineering Griffith University PMB50 GCMC Qld9726 Australia

flow over a backward-facing step was studied to investigate the effect of large-scale vortex structures on sediment incipience. The transient flow velocity field at the downstream of the backward-facing step was obtained using the technique of Particle Tracking Velocimetry （PTV）. The optical amplification technique was employed to measure the instantaneous flow velocities near the bed and the instantaneous bed shear stress was given. The experimental observations revealed a new insight into the oscillation of the large-scale structure and the three-dimensional characteristics of the flow. In particular, very high turbulence intensity, instantaneous horizontal velocity near the bed and the bed shear stress near the reattachment point were observed. The sediment incipient probability obtained from the sequent images of sediment particles near the bed indicates that the critical instantaneous shear stress of the sediment incipience is independent of flow conditions.

关键词： backward-facing step flow coherent structure,sediment incipience Particle Tracking Velocimetry (PTV)

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Electromagnetic control of the instability in the liquid metal flow over a backward-facing step

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Chinese Physics B 2022年第12期31卷 306-314页

作者： Ya-Dong Huang Jia-Wei Fu Long-Miao Chen Jiangsu University Zhenjiang 212013China Nanjing University of Science and Technology Nanjing 210094China

The tile-type electromagnetic actuator(TEA)and stripe-type electromagnetic actuator(SEA)are applied to the active control of the perturbation energy in the liquid metal flow over a backward-facing step(BFS).Three control strategies consisting of base flow control(BFC),linear model control(LMC)and combined model control(CMC)are considered to change the amplification rate of the perturbation *** is the combination of BFC and *** is utilized in BFC to produce the streamwise Lorentz force thus adjusting the amplification rate via modifying the flow structures,and the magnitude of the maximum amplification rate could reach to 6 *** is used in LMC to reduce the magnitude of the amplification rate via the wall-normalwise Lorentz force,and the magnitude could be decreased by 2 *** TEA and SEA are employed in CMC where the magnitude of the amplification rate could be diminished by 3 *** other words,the control strategy of CMC could capably alter the flow instability of the liquid metal flow.

关键词： electromagnetic actuator backward-facing step flow flow instability flow control

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Probability of Sediment Incipient Motion Under Complex flows

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China Ocean Engineering 2010年第1期24卷 93-104页

作者：刘春嵘邓丽颖呼和敖德 College of Mechanics and Aerospace Hunan University Institute of Mechanics Chinese Academy of Sciences

Presented in this paper is a mathematical model to calculate the probability of the sediment incipient motion, in which the effects of the fluctuating pressure and the seepage are considered. The instantaneous bed shear velocity and the pressure gradient on the bed downstream of the backward-facing step flow are obtained according to the PIV measurements. It is found that the instantaneous pressure gradient on the bed obeys normal distribution. The probability of the sediment incipient motion on the bed downstream of the backward-facing step flow is given by the mathematical model. The predicted results agree well with the experiment in the region downstream of the reattachment point while a large discrepancy between the theory and experiment is seen in the region near the reattachment point. The possible reasons for this discrepancy are discussed.

关键词： probability sediment incipience backward-facing step flow seepage pressure

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