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1.
EXPERIMENTAL AND NUMERICAL INVESTIGATION OF FREE SURFACE VORTEX   总被引:1,自引:1,他引:0  
An experimental model was set up to investigate the formation and evolution of the free surface vortex. A Particle Image Velocimetry (PIV) was used to measure the free surface vortex flow field at different development stages. Flow visualization was used to locate the vortex position and find its structure. Empirical formulas about the critical submergence and the whole field structure were obtained. It is found that the tangential velocity distribution is similar to that of the Rankine vortex and the radial velocity changes little in the vortex functional scope. Vortex starts from the free surface and gradually intensifies to air entrainment vortex. The vortex core moves during the formation and evolution of the free surface vortex. Based on the experimental model, the vortex position and structure were predicted by numerical simulation combined with a vortex model and compared with that of the experiments, which shows satisfactory agreement.  相似文献   

2.
本文用VOF方法数值模拟了三维涡环与自由表面的粘性相互作用。重点考察了Froude数、Weber数、初始扰动及密度分层对涡环与自由表面相互作用的影响。结果表明:由于粘性的存在,使得涡环与自由表面的相互作用与无粘情形相比有许多不同。粘性的作用主要体现在涡量的耗散和新的二次涡环的产生;对自由表面变形而言,Froude数是主要的控制参数,Froude数越大,自由表面变形越显著,而Weber数的影响作用则  相似文献   

3.
该文采用DPIV粒子成像测速系统对绕2D超空化水翼(Tulin翼)的空化流场进行了测量,研究了初生空化阶段,附着型片状空化阶段,空化云以及超空化四个阶段典型流场的速度分布及涡量分布。实验结果表明:在空化发展的四个阶段,相对于主流区域,空化流区域速度明显偏小;在整个流动区域,有两个速度梯度较大的区域,一个是空化区和水体主流区的交界面,一个是翼形表面的边界层区域。在空化发展的四个阶段邻近翼型尾部处均会产生一个大小近似相等的正向涡和一个反向涡,并且正向涡总是处于反向涡的下方,形成一组正向对涡。  相似文献   

4.
1.  INTRODUCTIONVortex sheet exists widely in a variety of nature and engineering problems,which isusually shed from airplane wing,ship propeller,swim ming fish,and so on.To study thebehaviour of vortex sheetevolution is much helpful to understand the physical mechanism ofthose flows.Therefore,many vortex m ethods[1 - 5 ] ,even involving viscous effects,weredeveloped to simulate the vortex sheet motion.As was discussed in Part I,asuperconvergence scheme based on Multhopp′s discretizati…  相似文献   

5.
ANALYSIS OF HYDRODYNAMICS FOR TWO-DIMENSIONAL FLOW AROUND WAVING PLATES   总被引:3,自引:0,他引:3  
Hydrodynamic characteristics for two-dimensional flow around a waving plate are investigated. Under large Reynolds number approximation, the flow is assumed to be a combination of the outer potential flow and a thin vortex layer, which consists of a boundary layer and a shed free shear layer. A nonlinear mathematical formulation for describing the outer unsteady potential flow coupled with an unsteady boundary layer equation for the inner viscous flow adjacent to the waving plate is developed. A semi-analytical method with a nonlinear Kutta condition imposed at the trailing edge is used to solve the velocity field of the outer flow and the evolution of wake vortex induced by a large-amplitude waving plate. The unsteady boundary layer equation is solved by extending Pohlhausen’s method to its unsteady counterpart. The thrust and viscous drag coefficients, propulsive efficiency, and the pattern of wake vortex sheet are discussed.  相似文献   

6.
STUDYOFINTERACTIONBETWEENVORTICESANDAFREESURFACEPARTⅡ:INTERACTIONOFDOUBLEVISCOUS VORTEXDIPOLESWITHAFREESURFACE¥WuChui-jie;Tan...  相似文献   

7.
1. INTRODUCTIONThevortexsheetisaninviscidmodelofaparallelshearflowinwhichthethicknessofthetransitionregionbetweenthetwostreamsissmallcomparedwithatypicalstreamwiselengthscale.Someworkhasbeendonetoinvestigatethevortexsheetevolutionusuallybyusingtwoapproaches.Oneistousesimpleandhigh-orderaccuratenumericalmethodstosolvetheNavier-Stokesequations,andtheotheroneisbasedontheKelvin-Helmholtzinstabilitytheoryandstudiestheinstabilityandevolutionofaninfinitetwo-dimensionalstraightvortexsheetofcons…  相似文献   

8.
水工建筑物进水口自由表面漏斗旋涡消除措施的试验研究   总被引:2,自引:0,他引:2  
水工建筑物进水口形成的自由表面漏斗旋涡,对工程危害极大。本文对自由表面漏斗旋涡的消除措施进行了试验研究,给出30种消涡措施(包括一些布置形式)。  相似文献   

9.
对雷诺数Re=1350带自由表面的后向台阶起动流进行数值模拟,得到其自由表面、再附着长度以及台阶后分离涡涡心位置随时间变化的规律,并进一步讨论了自由表面的波动和台阶后大尺度涡结构的产生、发展及溃灭的过程对再附着长度的影响。  相似文献   

10.
利用荧光黄纳及片光在水槽中对具有不同收缩比的民机后体的复杂绕流进行流动显示,探讨了后体的分离尾涡特性及参数影响.实验发现后体收缩比改变时对应了两种典型的尾涡流态,即稳定流向尾涡和周期性尾涡,并进一步探讨了尾翼对后体尾涡的影响。  相似文献   

11.
用密度函数法对自由表面进行数值模拟   总被引:1,自引:1,他引:0  
本文从二维非定常N-S方程出发,提出了一种处理自由表面问题的数值方法。引入密度函数法(density-function method)追踪自由表面,在密度函数的传输方程中采用TVD格式达到了二阶精度。对均匀来流中的非定常不可压方柱绕流进行了数值模拟。数值结果成功地捕捉了自由表面波动以及漩涡的生成、分离的时间发展历程。同时验证了本方法的有效性。  相似文献   

12.
二维滑坡涌浪的SPH方法数值模拟   总被引:4,自引:3,他引:1  
块体滑坡往往引起自由水面的剧烈变化,研究块体滑坡激发的水面波动一直是水利与海岸工程界非常感兴趣的问题。该文使用SPH方法(光滑质点水动力学)对水下块体下滑引起的自由表面水动力学过程进行了二维数值模拟,并将数值计算结果与试验数据作了对比,计算结果给出了块体下滑过程中,水体表面出现的二次卷破现象,以及在块体上方出现两个方向相反的旋涡,显示了SPH方法对处理块体下滑引起的自由表面大变形问题具有十分优越的特性。通过数值试验,文中还讨论了滑块下滑速度对自由表面破碎和形成的旋涡个数的影响。  相似文献   

13.

This study employs a Lagrangian frame numerical method to investigate two-dimensional free-surface flow induced by a submerged moving cylinder. This method combines the advantages of vortex methods and boundary integral methods, and is capable of capturing the complex motion of free surface and vortices. A series of computations are performed to investigate the effects of Froude number, the depth of submergence and still water depth on the flow motion. Free surface deformation, wake vortex and hydrodynamic forces are studied.

  相似文献   

14.
孤立波翻越防波堤流动的湍流数值模拟   总被引:6,自引:3,他引:3  
应用湍流数学模型和流体体积法模拟孤立波翻越防波堤的流动和自由表面变化。数模成功地再现了波浪涌顶和喷射、射流入水、自由表面破碎和漩涡产生等复杂流动过程,并获得了孤立波翻越防波堤时的压力分布。  相似文献   

15.
Scroll vortex intakes are hydraulic structures commonly used in water supply, drainage and sewerage systems. Water flows into the intake via an eccentric approach channel and a vortex chamber imparts swirl to the flow, leading to a stable air core vortex along the dropshaft. Although much effort has been devoted to investigate the scroll vortex flow, yet the understanding on its hydraulic characteristics is still far from complete due to a lack of detailed velocity field measurements. This paper presents the first comprehensive measurement of the three-dimensional (3D) flow field of a scroll vortex intake using non-intrusive Laser Doppler Anemometry (LDA). A validated 3D Computational Fluid Dynamics (CFD) model with the Volume-Of-Fluid (VOF) method is developed for interpreting the measurement. It is found that the vortex flow in the scroll chamber resembles a free vortex and the circulation is approximately equal to that at the chamber inlet, with a thin bottom boundary layer. The vortex flow at the bellmouth outlet possesses a circulation constant smaller than that in the chamber, and its vertical velocity component is approximately constant across the flow thickness.  相似文献   

16.
旋流排螺装置借鉴旋流排沙的原理,通过装置内产生的螺旋流使水和钉螺分离。为了探明装置内水螺分离机理,必须研究其流场全面图景。采用雷诺应力模型(RSM),结合流体体积函数(VOF)方法对旋流排螺装置的水气两相流进行三维数值模拟研究,并分析研究二次流分布特性。计算的自由水面和三维流速分布均与试验结果吻合较好。计算结果表明:切向流速分布呈现强迫涡特征,流速随半径的减小而减小;隔板能够抑制边壁处向上运动的水流、减弱携钉螺溢出的二次环流,对钉螺的有效排除有着关键作用。研究成果可为控制涵闸渠道钉螺扩散,改进旋流排螺装置提供技术技撑。  相似文献   

17.
孤立波与不同淹没深度水平圆柱体的相互作用   总被引:3,自引:3,他引:0  
用基于时变雷诺方程和方程为基础的数学模型模拟了孤立波与近海不同淹没深度水平圆柱的相互作用过程,其中自由表面的跟踪采用了分段线性近似的VOF方法.结果表明:当圆柱靠近水底时,尤其是在圆柱与底部海床有较小缝隙时,圆柱底部附近的涡旋较强;而圆柱靠近水面时,水面附近的涡旋较强,圆柱越靠近水面,圆柱背浪面一侧的水面附近产生的涡对越多.  相似文献   

18.
1 . INTRODUCTIONAhorizontalback and forthmotionproducednearasandbedby progressivegravitywavespropagationinshallowwaterusuallygivesrisetonearlysymmetricalbed formscom monlyknownasripples .Oscillatingflowsoverperiodicripplesareofpracticalaswellassci entific…  相似文献   

19.
针对混凝土板桩在干粗砂地基中的静压贯入问题,为了明确贯入过程中的挤土效应及贯入阻力的发展规律,利用离散元数值模拟软件EDEM(Engineering Discrete Element Method)对干粗砂中混凝土板桩静压贯入过程进行了三维数值模拟。为此,提出了适用于类似试验的参数标定方法,分析了贯入过程中颗粒的运动特征。针对板桩结构的特点,对长边和短边方向的挤土效应进行了对比,并以短边为例,分析了不同高度处的挤土效应。最后,根据颗粒与桩结构的接触力,提取了桩端阻力和桩侧摩阻力的值,分析了两者在贯入过程中的变化规律。结果显示:在贯入过程中,颗粒的运动呈现"涡流状",并随贯入过程演化;板桩沿短边方向的表面隆起量约为沿长边方向的隆起量的2倍;随着长宽比的增加,板桩结构在短边方向和长边方向的隆起值相应增加,且短边方向的隆起值与长边方向的隆起值的比值与相应板桩的长宽比近似相等;随着贯入的进行,桩侧摩阻力所占的比重逐渐增加,在完全贯入后,侧摩阻力值约占桩端阻力的1/25;不同长宽比的板桩结构,其桩端阻力和桩侧摩阻力的单位值近似相等,并与准二维计算结果相近。  相似文献   

20.
庞虹 《水资源保护》2005,21(5):27-30
通过对闪发室海水淡化装置的三维数值模拟,获得其三维流速与压力分布、自由面与流线谱形态、漩涡强度与湍流黏度分布等,调整障碍板的位置和数量后,计算出海水中尤其是液面附近的湍流强度,并由此分析了阻流板对流动与闪发效率的影响。从水力特性上看,装置阻流板不利于提高闪发效率。  相似文献   

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