Research On Hydrodynamic Characteristics Of Stilling Basin With Abrupt Drops Or Expansions

With the increasing development of water conservancy projects and the enhancement of people's consciousness of environmental-protecting awareness,the stilling basin with abrupt drops or expansions,which is based on the traditional bottom-flow dissipation to develop,has a wide application prospects in the field of hydropower industry,since it has many unique merits such as high efficiency of energy dissipation,less degree of flood discharge atomization,small water level fluctuation of downstream and its success in reducing the hydrodynamic characteristics of the stilling basin in a certain extent.In this paper,based on the model tests and numerical simulation,the hydrodynamic characteristics of the stilling basin with abrupt drops and expansions have been studied.The main results are as follows:(1)The flow pattern and underflow velocity of the stilling basin with abrupt drops or expansions has been deep investigated through the model tests and numerical simulations.Both the abrupt drops and expansions can reduce the maximum velocity of stilling basin,when the downstream water level and upstream water level is same,the dimensionless valuen of Vmax/(g0.5h0.5)is directly proportional to the ration of the depth of falling-sill and the height of dam(?/H).(2)This paper involves the detail about the distribution of time-average pressure in the stilling basin with abrupt drops or expansions.The distribution of time-average pressure in the stilling basin with abrupt drops had an obvious impact area,what is similar with the distribution of time-average pressure in the plunge pool.When stilling basin without sudden enlargement,the distributive of time-average pressure in transverse almost had no differences.When stilling basin with sudden enlargement,the time-average pressure in the region of expansion are obviously less than the central areas of stilling basin in the jump region.(3)This paper also contains the distribution law of fluctuating pressure in the stilling basin with abrupt drops and expansions.It successfully concluded two formulas respectively concerning the maximum fluctuating pressure coefficient(?max),?/H,and k of the stilling basin with abrupt drops,and ?max,expansion ration(?)and k of the stilling basin with abrupt expansions.The analyzation shows the spatial integral scales of different value of a/H,the probability characteristics,the fluctuating pressure characteristics of the spectrum of the stilling basin with abrupt drops,as well as the transverse distributive regularity of hydrodynamic pressure in stilling basin with abrupt expansions.(4)The results,based on the model tests,have shown the distribution law of uplift force on slab in the stilling basin with abrupt drops and expansions and also concluded two formulas respectively concerning the maximum uplift force coefficient(?max),?/H and k of stilling basin with abrupt drops,and ?max,? and k of stilling basin with abrupt expansions.It also analyzed the transverse distributive regularity of uplift force in stilling basin with abrupt expansions.The relative experiential formulas has been summarized according to analyzation of the relations among the maximum uplift per unit area(F),the fluctuating uplift per unit area(?F)and the fluctuating pressure(?P).