Abstract:In order to investigate overflow characteristics and discuss hydraulic characteristics about the airfoil weir,particle image velocimetry(PIV) technology was employed to measure the flow field over the airfoil weir which the ratio of height(P) and length(C) is 0.30 in flume under different relative water heads of 1.05,1.25,1.37,1.48 and 1.54.The flow velocity vector,streamline and vorticity under five corresponding kinds of Reynolds number(Re) were gained.The experimental results indicated that overflow characteristics including velocity and vorticity distribution regulation are same under different relative water heads or velocities.Stream lines are parallel approximately,flow is calm,and eddy was not found in the overflow near the airfoil weir wall.The airfoil weir overflow is "close to body" flow.The biggest velocity on the weir coping is 0.36 m/s in the experiment,and the velocity of weir heel and toe are less than main flow velocity and it is 0.05 m/s.It colud lessen the water flow erodibility.The vorticity which is 19.12 m2/s is biggest on the weir coping.Water flow energy dissipation on the weir coping was quickened.Dangerous pressure is avoided near the weir heel and toe where the vorticity is zero.
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