The Research Of Air Hole's Ventilation Volume And Air-water Ratio's Rule In An Internal Energy Dissipation Spillway Tunnel With Level Swirl Flow

Air hole is the ventilation installation which is at the beginning of an internal energy dissipation spillway tunnel with level swirl flow.It is the ventilation of flow inside swirl tunnel,which can ensure the formation of stable cavity swirling flow.And air hole also adds air for the flow with high speed to avoid cavitation.The size of air hole limits the ventilation volume and the air-water ratio inside swirl tunnel.It also influence the flow condition and the reduction of cavitation.However,there is no definite design process for air hole of swirl hole so far.So researching ventilation volume of air hole and the air-water ratio is pretty significant for the design of the size of air hole and swirl tunnel's stable operation.This paper is by performing the model test of vortex compound spillway tunnel with internal energy dissipation combined with the model test of Natural Science Foundation of China-"Research on the Vortex Blocking and Vortex Diffusion within the Strong Shear Two-phase Flow Hydraulic Characteristics",and it is also based on the test effects of the model test-"the hydraulic characteristics of the internal energy dissipation spillway tunnel with level swirl flow".The method of combining dimensional analysis and theoretical analysis is adopted to deeply research the ventilation volume and the air-water ratio of swirl tunnel under the conditions of different water levels both upstream and downstream,different generators,different air holes and different swirling blocking area.As a result,the research shows as follows:(1)When the entrance is stably submerged,there are three flow conditions that are free,sucking and submerged swirl flows.And flow conditions is influeced by air hole's ventilation volume,(H-h)/h and Frq,especially air hole's ventilation is the key factor.(2)With sucking and free swirl flow,fr? shows linear increase as Frq increases.With free swirl flow,the changing ratio is small.When adding blocking,the changing ratio gets smaller as the area of blocking hole decreases.(3)Under different flow conditions inside swirl tunnel,the mechanism of air hole is different.With sucking swirl flow,ventilation is decided by the pressure difference of air hole's entrance and exit,which appears suction mechanism.With free swirl flow,ventilation is decided by cavity swirl flow's air volume,which appears carrying mechanism.(4)With sucking swirl flow,H?/H shows near exponential increase as Frq and(1-pq/pgH)increase,and it also shows near linear increase as(Ar0/A0)2 increases.With free swirl flow,H?/H shows near linear increase as Frqand(1-pq/pgH)increase,but it is not related to(Ar0/A0)2.(5)With sucking swirl flow,?t/Q shows near exponential increase as Frq and(1-pq/pgH)increase,and it also shows near linear increase as Ar0/A0 increases.With free swirl flow,?t/Q shows near linear increase as Frq and(1-pq/pgH)increase,but it is not related to Ar0/A0.when adding blocking,as the area of blocking hole decreases,the changing ratio of ?t/Q following Frqand(1-pq/pgH)gets bigger(6)To present the design procedures of air hole's type and to give specific examples.