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RISS 인기검색어
- 검색키워드
- 저자 : Vasconcelos Neto, Jose Goes (검색결과 1 건)
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Dynamic approach to the description of flow regime transition in stormwater systems
Vasconcelos Neto, Jose Goes University of Michigan 2005 해외박사(DDOD)
소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.
Stormwater drainage systems are designed to operate in a free surface flow regime, however, transition into a pressurized flow regime may occur during intense rain events as the inflow exceeds the transport capacity of the system in free surface flow mode. The air phase within the sewers may then become pressurized, significantly altering the dynamics of the flow. Flow regime transitions have been linked to the occurrence of serious operational problems in stormwater systems, such as geysering and structural damage of sewers. While such flow conditions have been investigated previously, the current knowledge on this problem is still limited and fragmented, particularly regarding the role of the air phase in the filling process. The investigation presented in this thesis included experiments performed in reduced scale models representing stormwater storage tunnels, sewers and ventilation towers of stormwater systems. Numerical investigation was also performed to cre ate models to simulate flow regime transition caused by rapid filling of stormwater systems. The results of these investigations indicate that: (1) the magnitude of the surges caused by inflow bores in storage tunnels increase with the pressure head behind the pipe-filling bore front; (2) different new flow features caused by the air phase pressurization have been detected, which depend mainly on the ventilation degree provided in the system; (3) numerical models for the flow regime transition problem can be successfully modified to incorporate some the of newly identified air/water interactions in the predictions; (4) a new model concept for the flow regime transition was proposed, which overcomes the inability of Preissmann slot-based models to simulate sub-atmospheric, full pipe flows; (5) the numerical oscillations that contaminate the numerical predications of pipe-filling bores from shock-capturing models can be attenuated with judicious introduction of numerical diffusion; (6) new mechanisms for air pocket entrapment in stormwater storage tunnels undergoing rapid filling have been identified, and air pocket entrapment may relatively common; (7) the geysering caused by the release of large air pocket through water-filled ventilation towers can be minimized by appropriate selection of the ventilation tower diameter; (8) air phase pressurization caused by flow regime transition is also an important issue when the sewers are initially in steady flow conditions.
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