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THEORETICAL AND EXPERIMENTAL STUDIES OF HYDRAULIC CHARACTERISTICS OF DISCHARGE TUNNEL WITH VORTEX DROP

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Journal of Hydrodynamics 2010年第4期22卷 582-589页

作者： CHEN Hua-yong XU Wei-lin DENG Jun NIU Zhi-pan LIU Shan-jun WANG Wei state key laboratory of hydraulics and Mountain River Engineering Sichuan University Chengdu 610065 China

The velocities at given points in the volute chamber,the contracted section and the vertical dropshaft of a discharge tunnel with vortex drop were measured by a small specially designed L-shaped tube,as Laser Doppler Velocimetry（LDV） or Particle Image Velocimetry（PIV） would not work there due to the special structure of the discharge tunnel with vortex *** empirical formulas were proposed to predict the velocities and the angles of the velocities made with the vertical direction θ.The theoretical analysis results were in good agreement with experimental ***,the method proposed in this paper can be used to analyze related characteristics of discharge tunnels with vortex ***,different model scales were considered to predict the cavitation characteristics on the wall of a dropshaft in practical engineering.

关键词： discharge tunnel with vortex drop dropshaft velocity wall pressure cavitation

Characteristics of air flow driven by the free surface of the open channel

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Journal of Hydrodynamics 2022年第1期34卷 69-75页

作者： Jing Gong Jun Deng Wang-ru Wei Wei-wei Li state key laboratory of hydraulics and Mountain River Engineering Sichuan UniversityChengdu610065China

Spillway tunnels are a key structure in large-scale water conservancies. The high-head water inlet makes the water surface-velocity extremely high, and the air is driven by the free surface of the water to move downstream. This paper studies the air velocity distribution above the water surface through the model tests, under the assumption that the airflow is a turbulent boundary layer with a rough interface, and the influence of the water depth and the water velocity on the air velocity distribution is analyzed. It is shown that the air velocity is in an exponential distribution. As the measured position moves upward, the air velocity gradually decreases, and the gradient decreases. When the water depth increases, the air velocity increases but with the same distribution form. With the increase of the water surface-velocity, the air velocity at the same measuring point increases, the variation range near the water surface is large, the air boundary layer height increases slightly, and the index coefficient of the air velocity distribution function decreases. Through numerical fitting, the calculation formula of the air boundary layer thickness at different water surface velocities is obtained, along with the numerical value of the index coefficient.

关键词： Open channel air velocity distribution air boundary layer height index coefficient

Numerical Simulation of the Vortex-Induced Vibration of A Curved Flexible Riser in Shear Flow

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China Ocean Engineering 2018年第3期32卷 301-311页

作者： ZHU Hong-jun LIN Peng-zhi state key laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum University state key laboratory of hydraulics and Mountain River Engineering Sichuan University

A series of fully three-dimensional(3 D) numerical simulations of flow past a free-to-oscillate curved flexible riser in shear flow were conducted at Reynolds number of 185–1015. The numerical results obtained by the two-way fluid–structure interaction(FSI) simulations are in good agreement with the experimental results reported in the earlier study. It is further found that the frequency transition is out of phase not only in the inline(IL) and crossflow(CF) directions but also along the span direction. The mode competition leads to the non-zero nodes of the rootmean-square(RMS) amplitude and the relatively chaotic trajectories. The fluid–structure interaction is to some extent reflected by the transverse velocity of the ambient fluid, which reaches the maximum value when the riser reaches the equilibrium position. Moreover, the local maximum transverse velocities occur at the peak CF amplitudes, and the values are relatively large when the vibration is in the resonance regions. The 3 D vortex columns are shed nearly parallel to the axis of the curved flexible riser. As the local Reynolds number increases from 0 at the bottom of the riser to the maximum value at the top, the wake undergoes a transition from a two-dimensional structure to a 3 D one. More irregular small-scale vortices appeared at the wake region of the riser, undergoing large amplitude responses.

关键词： vortex-induced vibration flexible riser shear flow fluid–structure interaction computational fluid dynamics

NUMERICAL SIMULATION OF PROPAGATION AND BREAKING PROCESSES OF A FOCUSED WAVES GROUP

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Journal of Hydrodynamics 2012年第3期24卷 399-409页

作者： HUANG Zong-liu LIN Peng-zhi state key laboratory of hydraulics and Mountain River Engineering Sichuan University Chengdu 610065China

A two-dimensional numerical wave flume is developed to study the focused waves group propagation and the consequent breaking processes. The numerical model is based on the Reynolds-Averaged Navier-Stokes （PANS） equations, with the standard k - c turbulence model to simulate the turbulence effects. To track the complicated and broken free-surface, the Volume Of Fluid （VOF） method is employed. The numerical model combines the ＂Partial Cell Treatment （PCT）＂ method with the ＂Locally Relative Stationary （LRS）＂ concept to treat the moving wave paddle so that various waves can be generated directly in a fixed Cartesian grid system. The theoretical results of the linear and nonlinear waves are used to validate the numerical wave flume firstly, and then a plunging breaking wave created by a focused waves group is simulated. The numerical results are compared to the experimental data and other simulation results, with very good agreements. The turbulence intensity, the flow field and the energy dissipation in the breaking processes are analyzed based on the numerical results. It is shown that the present numerical model is efficient and accurate for studying the waves group generation, the waves packet propagation, and the wave breaking processes.

关键词： focused waves group plunging breaking Volume Of Fluid (VOF) k - ε turbulence model irregular wave maker

DESIGN OF GROUNDWATER LEVEL MONITORING NETWORK WITH ORDINARY KRIGING

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Journal of Hydrodynamics 2008年第3期20卷 339-346页

作者： YANG Feng-guang CAO Shu-you LIU Xing-nian YANG Ke-jun state key laboratory of hydraulics and Mountain River Engineering Sichuan University Chengdu 610065China

The primary network of groundwater level observation wells aims at realizing a regional groundwater management policy. It may give a regional picture of groundwater level with emphasis on the natural situation. Observation data from the primary network can be used to estimate the actual state of groundwater system. Since the cost of the installation and maintenance of a groundwater monitoring network is extremely high, the assessment of effectiveness of the network becomes very necessary. Groundwater level monitoring networks are the examples of discontinuous sampling on variables presenting spatial continuity and highly skewed frequency distributions. Anywhere in the aquifer, ordinary kriging provides estimates of the variable sampled and a standard error of the estimate. In this article, the average Kriging standard deviation was used as a criterion for the determination of network density,and the GIS-based approach was analysized. A case study of groundwater level network simulation in the Chaiwopu Basin, Xinjiang Uygur Autonomous Region, China, was presented. In the case study, the initial phreatic water observation wells were 18, a comparison of the three variogram parameters of the three defferent variogram models shows that the Gaussian model is the best. Finally, a network with 55 wells was constructed.

关键词： ordinary Kriging variogram sill nugget effect range groundwater monitoring network

Effects of vegetation patch density on flow velocity characteristics in an open channel

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Journal of Hydrodynamics 2019年第5期31卷 1052-1059页

作者： Wen-qi Li Dan Wang Jun-li Jiao Ke-jun Yang state key laboratory of hydraulics and Mountain River Engineering Sichuan UniversityChengdu 610065China

The aquatic plants are often found in natural rivers,and they affect the channel flow structure *** study the effects of the vegetation density a(the frontal area per volume)on the flow velocity characteristics,rigid bamboo circular cylinders are chosen as the model emergent *** the experiments,the density of the vegetation takes various values while all other flow parameters are kept constant.A 3-D acoustic Doppler velocimeter(ADV)is used to measure the local flow velocities for different vegetation *** results show that the existence of the vegetation patch leads to an increase of the depth-averaged velocity on the right and left sides behind the vegetation patch,and it increases monotonically with the vegetation *** different vegetation densities,the lateral distribution of the stream-wise velocity behind the vegetation patch follows approximately an S-shaped profile when a≤60 m-1,and a logarithmic profile if a>60 *** vertical distribution of the stream-wise velocity along the channel varies with the vegetation density and also follows an S-shaped distribution in a certain range,with the locations and the ranges being affected by the vegetation density.

关键词： Vegetation density stream-wise velocity depth-averaged velocity lateral distribution longitudinal distribution open channel

EXPERIMENTAL STUDY ON A NEW TYPE OF AERATOR IN SPILLWAY WITH LOW FROUDE NUMBER AND MILD SLOPE FLOW

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Journal of Hydrodynamics 2009年第3期21卷 415-422页

作者： SU Pei-lan LIAO Hua-sheng QIU Yue LI Chen-juan state key laboratory of hydraulics and Mountain River Engineering Sichuan University Chengdu 610065 China

Experimental study on aeration characteristics of various aeration devices was conducted in the spillway tunnel of the Pubugou hydropower project, Sichuan Province, China. It is shown by comparison that the new type of aeration device, namely, the aerator with a trapezoidal-shaped slot and a steep-slope section（ATSS）, can avoid water accumulation in the cavity of the aeration device in the project, thus can effectively solve the backwater problems arising from this project and be used for a wide range of different water levels, without any drain facilities. Above the water level of 840 m, the water contained in the cavity can be eliminated completely, which means that the recommended new type of aerator can meet the aeration demands in the spillway of the project with low Froude number and may be of practical significance and of interest to other projects with similar types of aeration devices.

关键词： aeration device a trapezoidal-shaped slot and a steep-slope section(ATSS) air entrainment cavitation

Collapse of cavitation bubbles near air bubbles

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Journal of Hydrodynamics 2020年第5期32卷 929-941页

作者： Jing Luo Wei-lin Xu Rui Li state key laboratory of hydraulics and Mountain River Engineering Sichuan UniversityChengdu 610065China

The cavitation erosion is one of the common damage modes in water *** study of the interaction among cavitation bubbles,air bubbles and the wall is of great significance for understanding the mechanism of the air entrainment to alleviate the cavitation and to enhance the cavitation erosion mitigation effect of *** using the high-speed camera,the regular patterns of the collapse of cavitation bubbles in the vicinity of the wall and the air bubbles are studied in this *** is shown that in the vicinity of air bubbles,the cavitation bubbles may only collapse towards or from air bubbles,while under the dual impacts of air bubbles and the wall,the direction of collapse of the cavitation bubbles depends on the combined vector of the impact forces of the air bubbles and the *** the air bubbles are very close to the cavitation bubbles,the air bubbles will be penetrated and stretched by the cavitation bubbles,when the distance between them is short enough,the cavitation bubbles and the air bubbles will connect to form gas-type cavitation bubbles,and the collapse strength will be significantly decreased,when there are two air bubbles near the cavitation bubbles,they may even be penetrated successively by the cavitation *** it can be concluded that during the air entrainment to alleviate the cavitation,the number of air bubbles is more important than the total air concentration.

关键词： Cavitation bubble air bubble high-speed photography air entrainment to alleviate cavitation

STUDY ON THE ANGLE OF REPOSE OF NONUNIFORM SEDIMENT

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Journal of Hydrodynamics 2009年第5期21卷 685-691页

作者： YANG Feng-guang LIU Xing-nian YANG Ke-jun CAO Shu-you state key laboratory of hydraulics and Mountain River Engineering Sichuan University Chengdu 610065China

A conception of exposure degree is used in this article to account for the hiding and exposure mechanism of nonuniform sediment transport. The force arms of particles on the bed slope are assumed to be a function of the exposure degree, which is stochastically related to the size and gradation of bed materials. Based on this conception, the formula for the angle of repose of nonuniform sediment is developed. The angle of repose of nonuniform sediment is experimentally investigated in rotation drum at the rolling motion of sediment particles. The nonuniform sediment is gotten from the mixture of two kinds of uniform sediment with different weight ratios and two experimental plans that one for changing the weight ratio of two kinds of uniform sediment from 1：9 to 9：1 and the other changing the uniform sediment size and weight ratio are used. The effect of the rotation speed and the filling degree on the angle of repose is investigated, too. Finally, the formula has been tested against a wide range of laboratory data, the prediction by the newly proposed formulas is very good.

关键词： the angle of repose nonuniform sediment rotation drum exposure degree