Investigation Of Lateral Diffusion Upon The Energy Dissipation Mechanism Among The Stilling Basin

The flood releasing structure is not only related to the project investment budget or safety operation,but also linked to the safety of life and property on the downstream region of both sides.Thus,it occupies a particularly prominent position in water conservancy projects.With the swift development of water conservancy and continuous improvement in environmental awareness in China,the current flooding releasing structure are required to dissipate the carrying energy among discharging flow within as short distance as possible,so that it can smoothly transit to the downstream natural riverbed and avoid serious erosion upon downstream riverbed.Most academics have prososed a variety of auxiliary energy dissipators to improve the energy dissipation among the discharging flow,but the unique attributes of respective flood releasing structures are often ignored to increase mutual impingement among discharging flow.Based on common engineering cases,this paper fully makes uses of structural attributes of flood releasing structures to force inflows to greatly diffuse in the upstream region of stilling basin.Thus,a vertical vortex and local reflux would form on bith sides of stilling basin.Compared to the classical hydraulic jump,such unique three dimensional hydraulic jump would not only cover the regular horizontal vortex and upper aeration,but also contain the unique vertical vortex and local reflux.Those compound movement would greatly increase energy dissipation and velocity attenuation among the discharging flow.Then,the secondary hydraulic jump and uneven lateral diffusion among the outgoing flow are total eliminated.Combined with above theroies,this paper then successively investigates the influence of lateral diffusion among discharing inflow from partial flaring gate piers,shared stilling basin and parallel hydraulic jump.Utilizing the lateral velocity gradients between discharging inflow from the flaring gate pier chamber and flat gate pier chamber,the partial flaring gate pier scheme is designed to force discharging inflow to laterally diffuse in the upstream region of stilling basin,and then form vertical vortex on both sides.Energy dissipation and air aeration in the stilling basin are greatly increased.Compared to the traditional flat gate pier scheme,the average and maximum velocities among the outgoing flow from the partial flarging gate pier scheme are respectively decreased by 32%,25%,and the bad hydraulic phenomenon of secondary hydraulic jump outside the stilling basin is totally eliminated.The shared stilling basin between the surface and bottom outlets is proposed to remove the longitudinal splitter pier in the downstream stilling basin and then results in the discharging inflow from both outlets to share the downstream flow section.Due to abruptly enlarged flow section in the condition of surface outlet or bottom outlet running alone,the discharging inflow is forced to laterally diffuse to cover the whole stilling basin and then form vertical vortex or local reflux.Correspondingly,owing to velocity gradients between adjacent inflow in the condition of surface outlet and bottom outlet running jointly,the pressurized jet from bottom outlet would greatly diffuse to squeeze the free overflow from surface outlet.Energy dissipation and mutual shear fraction are greatly increased in the shared stilling basin.Compared to the conventional separated stilling basin,the highly turbulent kinetic energy region is greatly broadened to cover the whole stilling basin with energy dissipation moved upstream.Thus,the average and maximum velocity among the outgoing flow respectively decrease by 30%,25%.Moreover,velocity gradients between the left and right outgoing flow almost decrease to zero with the phenomenon of lateral diffusion or deflected flow totally eliminated.The parallel hydraulic jump between adjacent chambers means that discharging inflow is forced to laterally diffuse to form wedged hydraulic jump above the downstream riverbed in the running condition of respectively different gate openings.The forward flow velocity zone,relatively static zone and the subsurface reverse flow zone would form in the downstream region.Results show that the forward velocity zone would laterally broaden to squeeze the subsurface reverse flow zone with the increasement of relative gate opening differences between adjacent chambers.But the vertical contraction coefficient and local head loss coefficient among the discharing flow below the vertical gate would maintain stable and would not change with the gate openings.Compared to the traditional classical and expanding hydraulic jump,the sequent depth after the parallel jump is much lower that of the classical jump,but higher than that of the expanding jump.With the increasement of relative gate opening differences,such sequent depth is prone to decrease to that of the expanding jump.An experienced equation is then proposed to calculate the sequent depth after parallel hydraulic jump with reliable accuracies.In general,combined with above invesitgations from partial flaring gate pier,shared stilling basin and parallel hydraulic jump,it can be found that the lateral diffusion among the discharging inflow would greatly increase the energy dissipation and mutual impingement among the running flow.Moreover,the corresponding flow pattern among the outgoing flow is obviously improved with secondary hydraulic jump eliminated.