The Research On Energy Dissipation And Anti-scouring Problem About Stilling Basin And Apron Structure Of Low-head Hydro-junction

In recent years,many provinces located in the middle and lower reaches of the river start the construction of low water head water conservancy hub,which generally built in the river in the middle and lower reaches of hub has low water head,low froude number(Fr),the dissipation is relatively low and the downstream riverbed anti shock resistance,long running after impingement often face all kinds of energy dissipation problem.And impingement facilities as the main energy dissipation structure of stilling basin and the sea,but also often due to the energy dissipation impingement condition does not meet the design requirements,Lead to a hub hydraulic structures or discharge sluice downstream riverbed erosion damage.For example,if a stilling basin energy dissipation effect is not good,that can't form the submerged hydraulic jump,and itwill lead to the downstream flood and sea bed scour damage;If stilling basin had poor ability,the upstream sand is stranded in the stilling basin and auxiliary energy dissipation friction,long-term damage energy dissipation in the pool facilities;If the structure of the sea flexibility deficiency,water scour for a long time,often cause sea base through air,eventually leading to the sea flood structure damage and the problem of downstream river bed scour.So,for the low water head water conservancy hub stilling basin and the sea flood energy dissipation structure research of impingement is very important.Based on the cross section of hydraulic physical model,first of all,in the question of low head water conservancy hub stilling basin which can prevent blunt,analyze the effect of energy dissipation and the sand,which are influenced by the differential tail sill arrangement of stilling basin.Second in problem of the low head water conservancy hub sea structure about flood energy dissipation impingement,through the cross section of hydraulic model tests and mathematic model calculation and analysis,research and applicate Renault pads flexible sea diffuse impingement effect of energy dissipation structure,and comparing with traditional rigid sea diffuse structure.This thesis mainly research results are following:(1)Baffle pier arrangement velocity the largest part in the bottom of a pool,will increase the water and baffle pier collision friction effect,improve the local energy dissipation effect,shorten the length of hydraulic jump,so as to shorten the length of the stilling basin,save the engineering construction investment,but on the whole energy dissipation effect is slightly lower.At the same time,it will enhance the stilling basin,especially in the tail before the sill section velocity in both energy dissipation of the ascension of the stilling basin sediment effect.(2)Slow down the differential tail of sill slope,it is advantageous to the sand and gravel in stilling basin out of the pool,but the effect of energy dissipation is reduced;If end sill long enough,it can increase the tail sill and flow friction collision area,make the differential tail sill in both the effect of sand at the same time,enhance its energy dissipation effect.(3)Renault pads sea flood has good flexible,can adapt to uneven settlement,the river water to prevent the scour,and Renault pads sea filling stone for the inside of a metal net surface structure,its collision with flow friction effect area,the roughness was greater than the rigid structure.Therefore,Renault pads the sea flood has better energy dissipation effect than traditional rigid diffuse structure.Application of Renault pads sea diffuse,compared with the rigid sea impingement diffuse structure has better energy dissipation effect,can shorten the sea flood design length,thus can save a lot of quantities,the engineering cost and investment.(4)Laying sea diffuse structure rigidity,small hole is formed at the beginning of the downstream river bed scouring,develop a pit can divide into three parts.By offshore scour the structure of the diffuse form circumfluence area near the slope toe,backflow zone bed surface velocity is larger,appear the scour phenomenon,in the direction of slope toe scour,scouring pit will develop and expand to the sea base,causing sea diffuse basal supporting air phenomenon;While backflow region after scouring the mainstream at the top of the slope zone,same bed surface velocity is always large,it river is scoured by blunt pit mainstream and river mainstream in two directions at the same time,flow washout for the downstream development and spreading of the pit;While the recirculation region and the area between the mainstream area,descend form vortex flow,turbulence,mix phenomenon is obvious,the turbulence kinetic energy is largest near river bed surface,the sediment is also easy to start.