Study On Hydraulic Performances Of Hydraulic Jump In Abrupt Plane Enlargements Channels

Hydraulic jump with abrupt lateral expansion is a common kind of hydraulic jump in the outflow under gate,which often occurs on gate-pump construction hub layout(intermediate sluice on both sides of the pumping station)in plain area or when parts of the multi-gates open.The flow suddenly spreads from a narrower width through the expansion,which forming a complex spatial flow.Abrupt lateral expansion in the downstream width of the channel will inevitably lead to a sudden turbulence shear layer between the re-circulation vortex and the main stream,and water flow is more complex due to the reflux extrudes the main stream to make the downstream unit-width flow Increase.The main study content of this paper is hydraulic jump in abrupt plane enlargements channels.Based on the investigation of hydraulic jumps formation mechanism through both experimental and analytical methods in abrupt enlargements channels,proposing new theoretical point of view and analyzing the flow characteristics and basic parameters of hydraulic jump in abrupt plane enlargements channels under various hydraulic conditions are studied.The paper explores the effects on the sequent depth,the hydraulic jump length and the energy loss due to the hydraulic jump by the upstream and downstream channel diffusion.Some conclusions are as below:(1)Then the sequent depths formula was acquired by plugging the average water depth into the equation for the sequent depths ratio.(2)The functional relationship between the factors influencing the hydraulic jump length in the diffusion channel is obtained by the dimension analysis,and the formula for calculating the hydraulic jump length in abrupt plane enlargements channels is fitted.(3)The energy loss rate calculation formula of the hydraulic jump in abrupt plane enlargements channels is put forward.The energy loss rate of the hydraulic jump in abrupt plane enlargements channels is increased by 5% ~ 10% compared with the prismatic channel by analyzing the existing data.(4)Simulating the flow pattern by FLOW-3D based on LU’s experimental model,which the conditions are combination of 4 width ratios(ε=1.2,1.5,2.0,3.0)and 3 gate opening heights(ε=0.02 m,0.03 m,0.05m).And then analyzing flow velocity and distribution patternin Downstream Channel.It is found that the re-circulation zone on the two sides of the main flow is generally not symmetrical,rather than there are many small re-circulation zones that are not in the symmetrical position by simulation when the width ratio is greater than or equal to 3(e ≥3.0).The asymmetric extrusion of the reflux vortex causes the mainstream to swing in the downstream diffusion zone.Larger the width ratio,the re-circulation zones is more asymmetric;the mainstream diffusion is more uneven;the swing is more intense.In this paper,the partial velocity values simulated by the width ratio ε= 1.2,1.5 and 2.0 were extracted and analyzed,and the flow velocity and flow regime of the downstream hydraulic jump were explored.