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Phenomenon of the sediment deposition in a hydraulic jump region of open channels

Journal of Mountain Science 2022年第7期19卷 1874-1885页

作者： xu wei-lin WANG Guo-guang FU Shi-hao wei Wang-ru State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan UniversityChengdu610065China

The hydraulic jump is a typical sudden change for mountain river areas.The effects of local hydraulic jumps on the particle transport capacity decrease and local flow resistance increase cannot be ignored as the sediment deposition disaster can amplify the flash flood disaster.The present research investigates the influences of a hydraulic jump on the individual particle movement and sediment deposition in a laboratory flume.The overall processes of a single particle movement are captured by a high-speed camera.The distribution of sediment deposition along the hydraulic jump is obtained statistically.The results show that both the particle size and the ratio of the upstream and downstream Froude numbers affect the particle motion process.A single particle coming from upstream gradually decelerates and finally stops at the hydraulic jump section because of hydraulic jump resistance.The particle acceleration first increases and then decreases during the time-domain process,and the attenuation trends are fast with the increase of ratio of upstream and downstream of Froude numbers.The increase of the maximum acceleration with sediment flows follows a linear trend approximately,which indicates that the kinetic features of the single sand particle are determined by the coupling effects of the hydraulic jump resistance and the sand dynamic properties.With the increase of sediment rate and sand particle size,the resistance effect of hydraulic jump on sediment deposition rate along the flow direction gets strong and the sediment deposition area is mainly located upstream of the hydraulic jump region.The present study shows that the possible sediment supply upstream must be obtained for identifying the disaster risk combined with the local hydraulic jump conditions.Further researches about the detailed critical condition deduced from the relationship between the water flow and sediment deposition are required to confirm and extrapolate present results to other applications.

关键词： Ratio of upstream and downstream Froude

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Analysis on link Between the Macroscopic and Microscopic Air–Water Properties in Self-Aerated Flows

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China Ocean Engineering 2018年第5期32卷 614-623页

作者： wei Wang-ru xu wei-lin DENG Jun TIAN Zhong ZHANG Fa-xing State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University

Self-aeration in high-speed free surface flows occurs commonly and is of interest to ocean engineering, hydraulic engineering, and environmental engineering. For two-phase air–water flows, macroscopic air–water flow properties develop gradually, accompanied by the change of microscopic air–water structures. In this article, representational experimental studies on macroscopic and microscopic characteristics of self-aerated open-channel flows are summarized and compared. The isolated effect of the flow Reynolds number and air quantity on the differences in air count rate and chord size are analyzed and discussed. The results show that the characterized flow depth y, affected by the turbulence transfer, is a specific criterion to distinguish the interior air–water structure development. Two distinct linear trends of self-aeration are found, depending on the y/yvariation with a breaking point at Cmean =0.50. The air count rate and size scale in self-aerated flows are affected by the air quantity of self-aerated flows, even with identical flow Reynolds numbers. Thus, a specific parameter is proposed to assess the air–water structures and a series of self-similarity relationships in self-aeration properties are obtained. The link between macroscopic and microscopic air–water properties results in significant scale effect on air–water structures in self-aerated flows.

关键词： self-aeration two-phase flows air concentration air bubble open channel

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NUMERICAL CALCULATION OF TURBULENT FLOW WITH FREE SURFACE

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Journal of Hydrodynamics 1991年第1期3卷 82-89页

作者： xu, wei-lin Yang, Yong-quan Wu, Chi-gong Chengdu Univ of Science and Technology Chengdu China

The problem of free surface is one of main difficulties in the numerical calculation of turbulent flow. This paper presents the concept of 'elastic-lid' for the first time, which is used to calculate the steady turbulent flow domains with complex free surfaces. This method can be combined with the existing steady turbulence models. Compared with MAC and other unsteady methods, it is simpler and can give us the parameters related to turbulent flow. The method is supported by the techniques of 'block-off' and 'elastic-grid', which can be selected for different problems. Finally, three examples are given to show the application of the 'elastic-lid' method. The calculated results are in good agreement with the measured.

关键词： Computers Applications Fluid Mechanics Hydraulic Jump Hydrodynamics Mathematical Models Mathematical Techniques Differential Equations

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Experimental study on pressure and aeration characteristics in stepped chute flows

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Science China(Technological Sciences) 2015年第4期58卷 720-726页

作者： xu wei lin LUO Shu Jing ZHENG Qiu Wen LUO Jing State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University

The free flow on the step surfaces has received much attention for its representative body type,flow structure,water-air two phase flow,cavitation,and many complex issues.The experiments about the time-averaged pressure and aeration concentration distribution on the step surface show that the vertical plane of steps will inevitably experience negative pressure,which must rely on adequate aeration concentration to avoid cavitation damage.However,the self-aerated flow at the head section has a relatively low aeration concentration,and the concentration of the entire steps decreases with the increasing of weir head,the minimum appears in the vicinity of the corner,and the location is close to the minimum pressure.Thus,it is necessary to set aerator in the upstream end of the step surfaces to avoid cavitation damage.

关键词：平均压力通风特性实验阶梯流量浓度分布气蚀破坏曝气装置

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AERATION EFFECT OF SUBMERGED JET ON HYDRAULIC CHARACTERISTICS

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Journal of Hydrodynamics 2002年第3期14卷 35-39页

作者： Liu, Shan-Jun xu, wei-lin Wang, wei Qu, Jing-xue Hydraulics Lab. of High Speed Flows Sichuan Univ. Chengdu 610065 China

A water-air two-phase turbulence mathematical model was proposed, The mass-weighted average was adopted for velocity, air mass fraction and turbulent parameters. The algebraic stress equation was used to calculate the Reynolds stress. The pulsating flux of air mass fraction was simulated by employing the concept of the eddy viscosity. The numerical simulation of aerated flow in plunge pool shows that, for the same depth, aeration may decrease the time-averaged pressure on pool floor and increase slightly the turbulent intensity. The computed concentration and pressure distributions coincide with the experimental data.

关键词： Computer simulation Mathematical models Pressure distribution Turbulent flow Two phase flow

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NUMERICAL SIMULATION OF TURBULENT FLOW THROUGH THROAT-TYPE ENERGY-DISSIPATORS

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Journal of Hydrodynamics 2002年第3期14卷 135-138页

作者： Dong, Jian-wei xu, wei-lin Deng, Jun Liu, Shan-Jun Wang, wei Qu, Jing-xue Hydraulics Lab. of High Speed Flows Sichuan Univ. Chengdu 610065 China

The flow through the throat-type energy-dissipators is calculated by using an axis-symmetrical K-Ε turbulence model. The velocity field, the pressure field and the distributions of turbulent energy and its dissipation rate are acquired. The energy dissipation through the throat-type energy-dissipators can be seen in detail. The calculated pressure distribution is compared with the measured and is in good agreement. The results are useful to understand deeply the flow characteristics of the throat-type energy-dissipators.

关键词： Computer simulation Flow of fluids Pressure distribution Turbulent flow Velocity

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NUMERICAL SIMULATION OF 3-D FLOW FIELD IN ARCIFORM PLUNGE POOL

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Journal of Hydrodynamics 2002年第3期14卷 106-110页

作者： xu, wei-lin Liu, Shan-Jun Wang, wei Qu, Jing-xue Diao, Ming-Jun Hydraulics Lab. of High Speed Flows Sichuan Univ. Chengdu 610065 China

The 3-D complex turbulent flow fields in a plunge pool with arciform bottom are simulated by using the k-Ε model in body-fitted coordinates. The calculated results reveal the flow characteristics in the arciform plunge pool under the different flood discharge conditions, which can not be easily obtained in the physical model test because the measurement of the complex velocity is very difficult. The calculated flow fields are helpful to understand the hydraulic characteristics of plunge pool deeply. The calculated and the measured pressure distributions on the pool bottom are compared and in good agreement.

关键词： Computer simulation Flood control Flow of fluids Pressure distribution Three dimensional

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EXPERIMENTAL INVESTIGATION OF THE FAILURE OF CASCADE LANDSLIDE DAMS

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Journal of Hydrodynamics 2012年第3期24卷 430-441页

作者： NIU Zhi-pan xu wei-lin LI Nai-wen xuE Yang CHEN Hua-yong State key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Chengdu 610065China Key Laboratory-of Mountain Hazards and Land Surface Processes and Institute of Mountain Hazards andEnvironment Chinese Academy of Sciences Chengdu 610041 China

This paper presents results of model tests for the landslide dam failure of a single dam and cascade dams in a sloping channel. The dams were designed to be regular trapezoid with fine sand. A new measuring method named the labeled line locating method was used to digitalize the captured instantaneous pictures. Under two different inflow discharges, the morphological evolution and the flow patterns during one dam failure and the failure of cascade dams were investigated. The results indicate that when the inflow discharge is large, the deformation pattern of the downstream dam is similar to that of the upstream dam, and both dams are characterized with the overtopping scour throughout the dam failure process. When the inflow discharge is small, the upstream dam is scoured mainly through a sluice slot formed by the longitudinal incision, and the downstream dam is characterized with the overtopping scour. The data set presented in this paper can be used for the validation of numerical models and provide a reference for the flood risk management of cascade landslide dams.

关键词： labeled lines locating method inflow discharge cascade landslide dam failure overtopping sloping flume

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SCALE EFFECT OF I MPINGING PRESSURE CAUSED BY SUBMERGED JET

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Journal of Hydrodynamics 2005年第4期17卷 478-482页

作者： TIAN Zhong xu wei-lin WANG wei LIU Shan-jun DONG Jian-wei State Key Hydraulics Laboratory of High Speed Flows Sichuan University Chengdu 610065 China Military Oil Supply Engineering Department Logistical Engineering University Chongqing 400016China

The characteristics of the impinging pressure at the jet equipment where the maximum jet velocity can reach 50m/s were studied. By comparing the impinging pressure with the one measured at the low velocity conditions, two conclusions of the scale effect are drawn： firstly, the velocity attenuation degree is smaller than that of low velocity jet, and secondly, the relative impinging width is narrower than that of low-velocity jet. The reasons of the scale effect of the impinging pressure were elucidated through numerical simulation.

关键词： scale effect impinging pressure high-velocity jet numerical simulation

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EXPERIMENTAL INVESTIGATION ON SOUND SPEED PROPAGATING THROUGH HIGH SPEED AERATED FLOW IN OPEN CHANNEL

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Journal of Hydrodynamics 2002年第3期14卷 97-101页

作者： Liao, Hua-Sheng xu, wei-lin Yang, Yong-Quan Wu, Chi-Gong Hydraulics of High Speed Flows Sichuan Univ. Chengdu 610065 China

An experiment concerning the sound propagation in aerated open channel flow was designed and conducted in a variable slope chute. The acquisition of sound data was done by the hydro-phones installed into the bottom wall of the chute. The data were analyzed and processed by the tape recorder and a 3562A analyzer. The primary experimental results indicate that the sound speed in aerated flow is varied with the air concentration and highly lower than each of the sound speed in pure water or air. As released by the derived theoretical formula, the minimum sound of 24 m/s in aerated flow happened when the air concentration achieved to 50%. This result shows that the compressibility of high speed aerated flow should be considered when the air concentration is near to 50%. A criterion of compressibility of high speed aerated flow was also given in this paper.

关键词： Air Compressibility Open channel flow Tape recorders Two phase flow Water

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