Mode Test And Mechanism Research Of The Stepped Spillway Overflow

In order to deeply stUdy the characteristics of overflow and seek for themeasure to increase the energy dissipation of the stePped spillway at large edtdischarge, the method of model test and theory analyZe are used to study the stePPedspillway oveffiowThe tyPical velocity field of oveffiow is measured using the Laser DopplerAnemometer and the mechbosm of the energy dissipation is analyzed. The mainreason of the stepped spillway having greater energy dissipation is tha there is bighorizontal vortex in the inner angel of the steps and it makes momenbo exchangewith outer mainstream then accelerates the theulence in the Water. It shows that theaeration influence is not neglect after correcting between the theory value andpractice calculate value.In the paPer the initial Iocation and dimension of step are studied from whichwe get the conclusion tha the energy dissipation is highcr if the initial location is atthe curve section of l/2 height of the sPillway top and the dimension gaP of neighborsteP is bigger, The energy dissipation is higher. At the toe of thc StePPed spillWay ifexchange a series of steps fOr arc section, the highe enersy dissipation can be gotbu the pressure is higher in downstream icction.In order to increase the energy dissipation of stePped spillway at Iarge unitdischarge, the integhty dissipater of Aerated splitter pier and StePpe characteristics isstUdied. Because of verticaJ diffhaion now by aerated splitter and impachng stePpe3by drop flow, the air concentration and the energy dissipation efficiency are greatly increased; the potentiality of cavitations is decrease. In special at large unit discharge, this effect is more obvious.Making use of the energy dissipation function of the step, the measure which takes step as curve jet flow is proposed. Namely, setting a series of steppes in the slope channel and deflector plate and hanged-grid at the cure section, through the model test, the conclusion is very good.