共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
挑流水舌对下游河道的冲刷关系到工程安全。根据动量方程推导了射流在下游水垫中的扩散规律,分析了下游水垫流速对射流扩散的影响,提出了动水垫下射流的临底流速计算方法。研究结果表明:动水流速增加了射流在水中的扩散距离,促进了射流扩散及射流流速衰减,降低了射流临底流速。将研究结果应用于白鹤滩岸边泄洪洞下游河道的冲坑深度预测。模型试验结果表明:在鼻坎水流参数相同的情况下,河道中水流为动水时的冲坑深度较静水时冲坑深度减小约10%,且位于河道下游侧的挑流水舌形成的冲坑深度小于上游侧挑流水舌形成的冲坑深度。与常规预测公式相比,该方法能准确预测不同位置挑流水舌的冲坑深度,研究结果可为泄洪设施下游河道消能防冲设计提供依据。 相似文献
3.
1 . INTRODUCTIONHigh speedliquidjetsareoftenseeninrainerosionsimulationofaircraftandmissiles ,JilbertandField[1] and jetcuttingofmaterials ,Kob ayashi[2 ] .Inthegenerationofjets ,itistechnicallyinterestingtoknowhowtooperatetheexperimen talfacilityattheoptimumconditiontoobtainthejetvelocitymostefficiently .ThisisdescribedbyShiandTakayama[3] ,ShiandItoh[4 ] ,ShiandIt oh[5] .Intheearlieststudyofa pulsedhigh speedliquidjet ,BowdenandBrunton[6 ] puttheliquidinanozzleandthenusedaslugimpact… 相似文献
4.
5.
TIAN Zhong XU Wei-lin WANG Wei LIU Shan-jun DONG Jian-wei 《水动力学研究与进展(B辑)》2005,17(4):478-482
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. 相似文献
6.
射流冲刷在众多疏浚工程中应用广泛并发挥了重要作用,对其开展深入研究很有必要。基于Eulerian二相流模型和k-ε湍流模型,以粒径为0.04~0.23 mm的沙床为研究对象,进行了二维垂向淹没射流冲刷沙床的数值模拟,研究了粒径和射流速度对沙床冲刷的影响。结果表明,在研究的粒径范围内,最大冲刷深度和悬浮泥沙体积与流速成正相关,与粒径成负相关,且流速的影响更大。 相似文献
7.
针对射流移动清淤时短时间内的冲刷效果问题,采用无网格光滑粒子动力学方法(SPH),对平面垂直淹没射流冲刷沙床的初始阶段进行了模拟计算。探讨了SPH中淹没环境和沙土材料的建立方法,研究了射流冲刷初始阶段动态冲坑深度的发展趋势,分析了射流速度对冲坑深度发展的影响。结果表明:采用SPH方法可以有效地模拟射流冲刷的过程;在初始阶段,冲坑深度随时间线性增加,而且随着射流速度的增加,坑深增加的速率加快。本文研究可为探讨疏浚射流破土效果提供数值方法参考。 相似文献
8.
Abstract Dam overtopping often results in the erosion of foundation and abutment materials. To quantify erosion potential, the jet impact velocity at the plunge pool interface must be estimated. Regións of the overtopping jet trajectory through free-fall are termed undeveloped (compact) and developed (individual particles). A physical model was constructed to simulate the developed region of a free-falling jet and to measure the impact velocity of developed jets. The equation derived for estimating the impact velocity of an undeveloped jet (Ervine and Falvey, 1987) was applied to the developed portion. The undeveloped jet estimation equation significantly overestimated the impact velocity of the developed jet. A drag expression was formulated and appended to the undeveloped equation resulting in a new equation, referred to as the Dimensional Equation Technique. The Dimensional Equation Technique was used to estimate developed jet impact velocities to within ± 4 percent. 相似文献
9.
ZHUWei MiaoGuo-ping YouYun-xiang DaiShi-qiang ZhouLian-di TaoMing-de LiuYing-zhong LuChuan-jing 《水动力学研究与进展(B辑)》2005,17(3):390-390
The Wave-making characteristics of a moving body in a two-layer fluid with free surface is investigated numerically and experimentally. The numerical analysis is based on the modified layered boundary integral equation system. The wave characteristics on the free surface and interface generated by a moving sphere and an ellipsoid is numerically simulated in both finite depth and infinite depth of lower layer model. The numerical results of the sphere are compared with the analytical results for a dipole with the same velocity in a two-layer fluid of finite depth. The dependence of the wave systems and structures on the characteristic quantities is discussed. Three kinds of measurement techniques are used in model experiments on the internal waves generated by a sphere advancing in a two-layer fluid. The effects of the varying velocity and stratification on the wavelength, wave amplitudes and the maximum half angles of internal waves are analyzed qualitatively. 相似文献
10.
三峡工程电源电站施工围堰防渗采取了振孔高喷防渗墙的形式。振孔高喷防渗墙是采用高压喷射注浆技术构筑的连续板墙状凝结体结构。振孔高压喷射注浆是一种钻喷一体化的高喷灌浆技术,以大功率的振动锤将带有特制喷嘴的高喷杆快速向下振孔,同时用高压设备使浆液、水及气成为高压流从喷嘴中喷射出来,冲击、破坏土体。当钻杆到达预定岩面后.以一定速度向上提升钻杆.使浆液与风化砂强制混合,待浆液凝固后,便形成了防渗墙。检测表明,三峡工程电源电站施工围堰高喷防渗墙施工质量优量.各项性能均满足设计要求. 相似文献
11.
Lin Jian-zhong Zhou Ze-xuanDepartment of Mechanics State Key Laboratory of Fluid Power Transmission Control Zhejiang University Hangzhou P. R. China) 《水动力学研究与进展(B辑)》1996,(2)
EFFECTOFSOLIDPARTICLESONSTABILITYFLOWINTHEBOUNDARYLAYERONAFLATPLATE¥LinJian-zhong;ZhouZe-xuanDepartmentofMechanics,StateKeyLa... 相似文献
12.
THE DYNAMIC EQUATION FOR A SPHERICAL BUBBLE IN UNIFORM SIZED SOLID PARTICLE-LIQUID HOMOGENEOUS SUSPENSION 总被引:1,自引:0,他引:1
Lin Yong-mingWuhan University of Hydraulic Electric Engineering Wuhan P. R. China. 《水动力学研究与进展(B辑)》1997,(4)
The momentum equation for solid-liquid two-phase flow proposed by Elghobashi and Abou-Arab is taken as the governing equations for the liquid phase,and the Lagrangian dynamic equation for a spherical particle moving in the liquid flow as the basic equation for the relative motion of the particle in the liquid phase in the paper.The dynamics equation for a bubble in solid-liquid twophase flow is proposed,as well as the simplified equations under two extreme conditions with the relationship between the bubble collapse characteristic time τ_C~* and particle response time τ_(rel)~* being τ_C~*>> τ_(rel)~* and τ_C~* <<τ_(rel)~*. 相似文献
13.
Lin Jian zhong Liu Zhong qiu Wang Ye long Department of Mechanics State Key Laboratory of Fluid Power Transmission Control Zhejiang University Hangzhou P.R.China 《水动力学研究与进展(B辑)》2000,12(2)
1. INTRODUCTIONTheliquidorgasflowofsolidfibersuspensionsconcernssomediffcultproblemsinthetheoreticalresearchofmultiphaseflowandNon-Newtonianflow.Sotheresearchofithasgreattheoreticalvalues.Atthesametime,theapplicationoftheflowwithfibersuspensionsisveryextensive.Inmaterialsscience,compositematerialsarebeingpaidmoreandmoreattentiontoshort-fibermaterialarethemostcommononeinvariouscompositematerials.Themoldingandmachiningofshort-fibermaterialhavemuchtodowiththedynamiccharacteristicsoftheflow… 相似文献
14.
YIN Zhao-qin LIN Jian-zhong 《水动力学研究与进展(B辑)》2007,19(5):533-541
The Large Eddy Simulation (LES) method has been used to solve the fluid momentum equations coupled with a convection-diffusion equation to study the formation of pollutant nanoparticles in a vehicular exhaust with impinging twin-jet. The functions of the space (S) between the two jets and the distance (H) from the exit of nozzle to the impingement plane are evaluated according to the distributions of pollutant nanoparticles. The results show that the nucleation produces a large number of nanoparticles, and gas-to-nanoparticle conversion mostly takes place in the interface region of the two jets, the circumambience of the jets, and region near the plane. The maximal particle size and maximal number concentration produced by both nucleation and coagulation appear around the region of free jet and the region near the plane, respectively. The significant differences for various spaces between the two jets are the number concentration and size distributions in the interface region of the two jets. For the case with larger space, more nanoparticles are produced by nucleation and coagulation. The more the distance from the exit of nozzle to the impingement plane, the lower is the number concentration and the fewer the particles distribute near the plane. Increasing the distance from nozzle to plane is beneficial to the reduction of nanoparticle formation. 相似文献
15.
The air flow induced by a water jet freely falling inside a vertical pipe with its top and bottom both open to the atmosphere was investigated experimentally and numerically. In the experiments, the radial air velocity distribution and the air pressure variation along the vertical pipe were measured. The air drag of the falling water jet was related to the jet surface disturbance and analyzed by introducing the equivalent friction factor. A predictive model was developed for the air flow inside a 3-m-high pipe based on the momentum equation and its results compared well with the experimental measurements. Numerical simulations were also conducted by approximating the free-falling water jet as a continuous moving solid with diameter and velocity varying in the direction of motion. The effects of pipe size on the air velocity profile and the induced air flow rate were examined. The simulation results showed that the streamwise air velocity profiles inside pipes of different sizes approached the same after a certain traveling distance. The maximum induced air flow rate was found at the pipe diameter of about 20 times of initial water jet diameter. 相似文献
16.
1. INTRODUCTIONAbrasive Water Jet (AWJ), has been developed the into a remarkable and extensively used cutting technology in last two decades. In recent years, the polymer PAM has generally been applied to jetting fluid to further increase the abrasive ve… 相似文献
17.
PDA MEASUREMENTS OF TWO-PHASE FLOW STRUCTURE AND PARTICLE DISPERSION FOR A PARTICLE-LADEN JET IN CROSSFLOW 总被引:1,自引:1,他引:0
The two-phase flow structure and particle dispersion for a dilute particle-laden jet in crossflow(JICF) were experimentally investigated by means of Phase Doppler Anemometry(PDA) measurement.The two-phase flow experiments were conducted for different flow conditions and solid particle parameters,including the ratio of the jet velocity to crossflow velocity,the particle size and mass loading.The experimental results indicate that the fine particles with the size of 70 micron and the mass loading of 0.05% hav... 相似文献
18.
基于SPH方法挑流水舌的数值模拟研究 总被引:1,自引:0,他引:1
以数值模拟挑流水舌的运动特性为目标,采用光滑粒子动力学方法,根据水气两相流的运动规律,建立掺气水舌的SPH数学模型,根据空气阻力的作用特性和自由表面判据,得到了空气阻力的计算关系式,提出了掺气水舌的SPH数值解法。针对桓仁水电站泄洪雾化,进行了掺气水舌的SPH数学模型实例研究,所得到的光滑粒子运动图像刻画了挑流水舌与空气的相互作用,模拟了挑流水舌的掺气过程,并得到了掺气水舌的厚度和速度随其曲线长度的变化关系。结果表明,桓仁水电站挑流水舌的外缘挑距模拟值为82.2 m,原型观测数据为80.2 m,计算误差为2.49%。掺气水舌的挑距模拟值与其原观值基本一致,证明了掺气水舌SPH数学模型模拟挑流水舌运动的有效性和可靠性。 相似文献
19.
A horizontally discharging jet laden with solid sediment particles is investigated experimentally. The submerged jet discharges water with an initially horizontal direction into stagnant water of the same density but the presence of sediment particles produces jet effluent having a combined density greater than that of the ambient water. A modified particle-imaging velocimetry (PIV) technique is applied to estimate the velocity fields of the solid particle phase and the jet fluid liquid phase. Phase separation is achieved optically between the scattered light signals from the particles and the laser-induced fluorescence signal from the jet fluid dozed with a fluorescent dye. It is found that initial sediment concentrations below 0.1% volume fraction do not cause significant changes to the global properties of the jet flow. In jets of higher initial sediment concentrations, settling of sand particles are observed to drag the jet to spread with a downward-bending mean trajectory. Intensive particle–flow interaction is also observed in jets of high sediment concentrations. 相似文献
20.
RESEARCH ON MOTION CHARACTERISTICS OF GAS-SOLID JET FLOW 总被引:1,自引:0,他引:1
Lin Jian-zhong 《水动力学研究与进展(B辑)》1999,(2)
l.INThoDUCT1ONTheresearchontwo-phasejetflowisbecomingahotspotofjetflowresearchinrecentyears.Therapiddevelopmentofcomputertechnologyhasmadeitpossibletosimulatetwo-phasejetflow,whichisofessentialimPortanceinvariousengineeringapplications.Forin-stanceitisausualproceduretospoutparticlesintoreactororcombustorinengineering.Theeffectofflowonparticlesdeterminestheparticledistributionandthepresenceofparticleshaveeffectonjetflowinturn.Therefore,theinvestigationontheparticledistributionandtheflowchar… 相似文献