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flow choking characteristics of slit-type energy dissipaters

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Journal of Hydrodynamics 2015年第1期27卷 159-162页

作者：吴建华万彬马飞李同春 National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety College of Water Conservancy and Hydropower Engineering Hohai University

In this paper, the behavior of the flow choking, including the critical and developing states, was experimentally investiga- ted by means of five slit-type outlets, characterized by the outlet width, the contraction angle and the opening of the working gate. The results showed that the approach flow Froude number of the critical choking decreases if the outlet width increases, or the con- traction angle decreases, or the opening increases. There is the hysteresis when the flow choking develops, i.e., the Froude numbers of the appearance and disappearance of the flow choking at the increasing discharge regime are all larger than those at the decreasing discharge regime. For various widths of the outlets, the differences between the critical Froude numbers at small opening are much larger than thoset at large opening. The change range from appearance to disappearance of the flow choking at small opening is smaller than that at large opening.

关键词： flow choking slit-type energy dissipater partial opening Froude number

Hydraulics of crest spillway with large unit discharge and low Froude number

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Journal of Hydrodynamics 2015年第2期27卷 242-247页

作者：吴建华李程纯子马飞李同春吴伟伟 National Engineering Research Center of Water Resources Efficient Utilization and Engineering Safety College of Water Conservancy and Hydropower EngineeringHohai University Hydraulic Structures design division Hydrochina Huadong Engineering Corporation

With respect to the crest spillway with large unit discharge and low Froude number, the hydraulics of the slit-type energy dissipater at the outlet should be noticed due to the complicated flow regimes. In the present paper, some issues about hydraulic characteristics were experimentally investigated by means of five slit-type outlets and four tetrahedrons, including the flow choking, impact to river banks and jet trajectory. The main findings are as follows. The critical Froude number for the flow choking decreases with increasing outlet width of the slit-type energy dissipater. If the flow Froude number is expressed by the parameters just before this energy dissipater, the tetrahedron placed inside the side wall of the outlet could efficiently avoid the flow impact to the river bank of same side, and compared with the jet trajectory of the slit-type energy dissipater, the outlet with tetrahedron has different trajectory trend, i.e., the distance of the jet trajectory decreases with the increase of the water head due to special form of the outlet tetrahedron.

关键词： large unit discharge low Froude number flow choking impact to river bank jet trajectory

Analysis of choked two-phase flows of gas and particle in a C-D nozzle

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Theoretical & Applied Mechanics Letters 2017年第6期7卷 331-338页

作者： Guang Zhang Heuy Dong Kim Ying Zi Jin Department of Mechanical Engineering Andong National University College of Mechanical Engineering & Automation Zhejiang Sci-Tech University

Particle-gas two-phase flows show significantly different behaviors compared to single gas flow through a convergent-divergent nozzle. Non-equilibrium effects, thermal and velocity lag results to the inefficiency of nozzle performance. In the present studies, theoretical analysis and numerical simulations were carried out to investigate particle-gas flows in a C-D nozzle. Homogeneous equilibrium model that no lag in velocity and temperature occurs between particles and gas phase was used to derive mass flow rate and sound speed of multiphase flows. Two-phase flows are regarded as isentropic flows that isentropic relations can be used for homogeneous equilibrium model. Discrete phase model （DPM） where interaction with continuous phase and discrete random walk model were considered was used to calculate particle- gas flows. Particle mass loadings were varied to investigate their effects on choking phenomena of particle-gas flows. Mass flow rate and sound speed of mixture flows were theoretically calculated by homogeneous equilibrium model and compared with numerical results. Shock wave structure and particle number density were also obtained to be different at different particle mass loading and operating pressure conditions.

关键词： Multiphase flows Particle number density Shock wave Sound speed of mixture flow choking