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1.
In the present study we investigate the 3-D hydrodynamic slamming problem on a vertical cylinder due to the impact of a steep wave that is moving with a steady velocity.The linear theory of the velocity potential is employed by assuming inviscid,incompressible fluid and irrotational flow.As the problem is set in 3-D space,the employment of the Wagner condition is essential.The set of equations we pose,is presented as a mixed boundary value problem for Laplace’s equation in 3-D.Apart from the mixedtype of boundary conditions,the problem is complicated by considering that the region of wetted surface of the cylinder is a set whose boundary depends on the vertical coordinate on the cylinder up to the free-surface.We make some simple assumptions at the start but otherwise we proceed analytically.We find closed-form relations for the hydrodynamic variables,namely the time dependent potential,the pressure impulse,the shape of the wave front(from the contact point to beyond the cylinder) and the slamming force.  相似文献   

2.
The explicitly analytical solution is derived for the dispersion relation of the flexural–gravity waves in a two-layer fluid with a uniform current. The upper fluid is covered by a thin plate with the presence of the elastic, compressive and inertial forces. The density of each of the two immiscible layers is constant. The fluids of finite depth are assumed to be inviscid and incompressible and the motion be irrotational. A linear system is established within the framework of potential theory. A new representation for the dispersion relation of flexural–gravity waves in a two-layer fluid is derived. The critical value for the compressive force is analytically determined. The dispersion relation for the capillary–gravity with an inertial surface in a two-layer fluid can be obtained in parallel. Some known dispersion relations can be recovered from the present solution.  相似文献   

3.
A numerical study is carried out to study the effects of the temperature dependent viscosity on the flow and heat transfer of a nanofluid over a flat surface in the presence of viscous dissipation. The governing nonlinear partial differential equations are transformed into nonlinear ordinary differential equations, and are solved numerically by the Keller-box method. The numerical results indicate that the effect of nanoparticle volume fraction is to increase the heat transfer and hence enhance the thermal boundary layer thickness. This is true even in the presence of variable viscosity and the viscous dissipation. Furthermore, the results obtained for heat transfer characteristics with nanoparticles reveal many interesting behaviors that warrant further study on the effects of the "nano-solid-particles".  相似文献   

4.
The motion of a single spherical bubble due to buoyancy in the ideal fluid with waves is studied in this article. Assuming that the bubble has no effect on the wave field, equations of a bubble motion are attained. The equations are solved. It is found that the nonlinear effect increases with the increase of the bubble radius. Since the difference between the frequencies of gravity waves and the eigenfrequency of bubbles is great for small bubbles, their oscillations can not be coupled. During the rising of a bubble, the oscillation of the bubble decays very fast, so it can be ignored. The rising time and the motion orbit are given. When the wave is high and the bubble is small, the spiral orbit may appear.  相似文献   

5.
To better understand the complex process of wave transformation and associated hydrodynamics over various fringing reef profiles, numerical experiments were conducted with a one-dimensional (1D) Boussinesq wave model. The model is based on higher-order Boussinesq equations and a higher-accuracy finite difference method. The dominant energy dissipation in the surf zone, wave breaking, and bottom friction were considered by use of the eddy viscosity concept and quadratic bottom friction law, respectively. Numerical simulation was conducted for a wide range of wave conditions and reef profiles. Good overall agreement between the computed results and the measurements shows that this model is capable of describing wave processes in the fringing reef environment. Numerical experiments were also conducted to track the source of underestimation of setup for highly nonlinear waves. Linear properties (including dispersion and shoaling) are found to contribute little to the underestimation; the low accuracy in nonlinearity and the ad hoc method for treating wave breaking may be the reason for the problem.  相似文献   

6.
Under the condition of low gravity the characteristics of liquid forced sloshing in a turning spherical tank with a spacer were investigated. The static shape of the liquid surface was analyzed. By expanding the characteristic functions, the frequencies and velocity potential of liquid free-sloshing were derived. The governing equations and boundary conditions for the forced sloshing of liquid under the tank turning were established. The transverse force of liquid acting on the tank and the moment of force to the centre of the tank which is caused by the force of liquid acting on the spacer were given. Numerical results were compared with the ones of the spherical tank without a spacer. The results show that when a spacer is inserted in the tank, the sloshing frequency of liquid and the transverse force of liquid acting on the tank will decrease, but the moment of force to the centre of the tank which is caused by the force of liquid acting on the spacer will occur.  相似文献   

7.
A SPLIT-CHARACTERISTIC FINITE ELEMENT MODEL FOR 1-D UNSTEADY FLOWS   总被引:3,自引:3,他引:0  
An efficient and accurate solution algorithm was proposed for 1-D unsteady flow problems widely existing in hydraulic engineering. Based on the split-characteristic finite element method, the numerical model with the Saint-Venant equations of 1-D unsteady flows was established. The assembled finite element equations were solved with the tri-diagonal matrix algorithm. In the semi-implicit and explicit scheme, the critical time step of the method was dependent on the space step and flow velocity, not on the wave celerity. The method was used to eliminate the restriction due to the wave celerity for the computational analysis of unsteady open-channel flows. The model was verified by the experimental data and theoretical solution and also applied to the simulation of the flow in practical river networks. It shows that the numerical method has high efficiency and accuracy and can be used to simulate 1-D steady flows, and unsteady flows with shock waves or flood waves. Compared with other numerical methods, the algorithm of this method is simpler with higher accuracy, less dissipation, higher computation efficiency and less computer storage.  相似文献   

8.
This paper is aimed at a systematic discussion on the basic equations for two-phasetransient flow and the theory of pressure waves and interfacial waves.The characters of the ba-sic equations have been analyzed.The formulas for wave speed of pressure and interfacial waveshave been derived.It has been proved that various mathematical models can be unified by theproposed integrating model and various wave speed formulas can be unified by the derived uni-versal formula.The basic equations for the separated flow model are ill-conditioned because ofthe unreasonable neglect of the pressure differences between the phases and the interfaces.Driftflux model can improve the accuracy if some additional equations are provided.However theymust be carefully chosen.The basic equations for homogeneous flow model are well-conditionedand they can be used in two-phase transient flow,especially in the cases of no velocity slips be-tween the phases.  相似文献   

9.
NUMERICAL STUDY OF SOLITARY WAVE FISSION OVER AN UNDERWATER STEP   总被引:1,自引:0,他引:1  
Solitary wave fission over an underwater step is numerically investigated. The numerical model is based on the enhanced Boussinesq equations, which appropriately represent both the nonlinearity and dispersivity of surface water waves. The finite difference method defined on the staggered grid in space with an implicit scheme for time stepping is employed for the numerical solution of the governing equations. It is demonstrated that Boussinesq type equations, though they are vertically integrated, can describe the details of the solitary wave fission process with very good accuracy. Numerical results of the reflected and transmitting wave heights, the number of solitons emitted from the transmitting wave and their amplitudes all agree very well with the analytical solution derived from KdV equation by virtue of a linear long wave approximation in the vicinity of the underwater step.  相似文献   

10.
A two-dimensional numerical model based on the Navier-Stokes equations and computational Lagrangian-Eulerian advection remap-volume of fluid (CLEAR-VOF) method was developed to simulate wave and flow problems. The Navier-Stokes equations were discretized with a three-step finite element method that has a third-order accuracy. In the CLEAR-VOF method, the VOF function F was calculated in the Lagrangian manner and allowed the complicated free surface to be accurately captured. The propagation of regular waves and solitary waves over a flat bottom, and shoaling and breaking of solitary waves on two different slopes were simulated with this model, and the numerical results agreed with experimental data and theoretical solutions. A benchmark test of dam-collapse flow was also simulated with an unstructured mesh, and the capability of the present model for wave and flow simulations with unstructured meshes, was verified. The results show that the model is effective for numerical simulation of wave and flow problems with both structured and unstructured meshes.  相似文献   

11.
BRIEFINTRODUCTIONOFTHEPAPER : Inthefirstpartofthisthesis ,thefundamentalsolutionsforthesingularStokesandOseenflowsinanun boundedfluidarederivedinauniversalformwhichinvolvestheHamiltonian ,Hessian ,andLaplacianoperators ,andelementaryfunctions .Inthesecondpart,theinteractionofunsteadylow Reynolds numberflowswithafreesurfaceisinvestigatedanalytically .Thedisturbedflows ,generatedbysubmergedbodiesmovingverticallydownwardsawayfromthesurfaceofthefluid ,aregovernedbytheunsteadyStokeseq…  相似文献   

12.
1 . INTRODUCTIONThewavemotionduetoamovingdisturbancehasbeenoflong standinginterest .Butthecorre spondingwakestructuredidnotreceivemuchat tentionuntilthesyntheticapertureradarcollectedanumberofimagesofV likewakepatternsgener atedbyships (Milgram 1988;Brownetal.1989) .Thewakestructuresarethoughttobeclassifiedin tothreecategories :theKelvinwavewakes ,thetrubulentwakesandtheinternalwavewakes(Griffin 1988;Lydenetal.1988;GuandPhillips1994 ) .TheKelvinwakesarethefar fieldwavepatternsgenerate…  相似文献   

13.
Generation of the transient flexural- and capillary-gravity waves by impulsive disturbances in a two-layer fluid is investigated analytically. The upper fluid is covered by a thin elastic plate or by an inertial surface with the capillary effect. The density of each of the two immiscible layers is constant. The fluids are assumed to be inviscid and incompressible and the motion be irrotational. A point force on the surface and simple mass sources in the upper and lower fluid layers are considered. A linear system is established within the framework of potential theory. The integral solutions for the surface and interfacial waves are obtained by means of the Laplace-Fourier transform. A new representation for the dispersion relation of flexural- and capillary-gravity waves in a two-layer fluid is derived. The asymptotic representations of the wave motions are derived for large time with a fixed distance-to-time ratio with the Stokes and Scorer methods of stationary phase. It is shown that there are two different modes, namely the surface and interfacial wave modes. The wave systems observed depend on the relation between the observer's moving speed and the intrinsic minimal and maximal group velocities.  相似文献   

14.
1.INTRODUCTION ThelinearCauchy Poissonproblems,which areconcernedwiththegenerationandpropagation offree surfacewavesduetoaninitialelevationor apointpressureactingonthefreesurfaceofanin compressibleinviscidfluid,havebeeninvestigated bymanyresearchersinviewofitstheoreticalinterestandpracticalimportance[15].Thetransient developmentoftwo dimensionalgravitywavesdue toanoscillatingsurfacepressurewasconsideredby Miles[6]whoproposedawell posedinitialvalue problemtocorrectStoker'sformulation[2].A…  相似文献   

15.
The transient gravity waves due to an impulsive source in a two-layer fluid system are investigated analytically.The fluid is assumed to be inviscid and incompressible.The density of each of the two layers is constant.Five different boundary conditions are considered.The depth of each of the two layers is infinite or finite.The upper fluid of finite depth is covered by a rigid lid or a free surface.Based on the assumption of small-amplitude waves,a linear system is established.The integral solutions for the free-surface and interfacial waves are obtained by means of the Fourier-Laplace transform.The corresponding asymptotic representations are derived for large time with a fixed distance-to-time ratio by the Stokes and Scorer methods of stationary phase.The analytical solutions show that there are two different modes,namely the free-surface and interfacial wave modes.The wave profiles observed depend on the relation between the distance-to-time ratio and the maximal group velocities and on the limiting values of the second derivatives of the frequencies as well.  相似文献   

16.
本文讨论了具表面张力作用下不可压缩无粘流体流过地形障碍物的共振流动。采用摄动方法,本文导出了一个新的方程,具负色散的fkdv方程,数值结果表明该情形可激发出下游下凹孤立波串,这个结果有待进一步的实验验证。  相似文献   

17.

The generation and interaction of surface and interfacial gravity waves due to an submerged source moving in a two-layer fluid are investigated analytically for two-dimensional cases. The fluid is assumed to be inviscid and incompressible. The density of each of the two layers is constant. Two different boundary conditions are considered for the upper surface. The upper fluid of finite depth is bounded above by a rigid lid or a free surface. Based on the assumption of small-amplitude waves, a linear system is established. The integral solutions for the free-surface and interfacial elevations are obtained by means of the Fourier transform. Then the corresponding asymptotic representations are derived for far-field waves by the residue theorem. The critical Froude numbers for the existence of far-field waves are derived for the two-layer system bounded above by a rigid lid or a free surface. The effect of different upper boundary conditions on the wave generation are discussed.

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18.
This paper aims to provide a better understanding of the interaction between solitary waves and vertical circular cylinders. This is achieved via process based numerical modelling using the parallel particle-in-cell based incompressible flow solver PICIN. The numerical model solves the Navier-Stokes equations for free-surface flows and incorporates a Cartesian cut cell method for fluid-structure interaction. Solitary waves are generated using a piston-type wave paddle. The PICIN model is first validated using a test case that involves solitary wave scattering by a single vertical cylinder. Comparisons between the present results and experimental data show good agreement for the free surface elevations around the cylinder and the horizontal wave force on the cylinder. The model is then employed to investigate solitary wave interaction with a group of eleven vertical cylinders. The wave run-up and wave forces on the cylinders are discussed.  相似文献   

19.
本文研究了在波流联合作用下的任意三维物体的波浪绕射问题,建立了求解物体上的波浪绕射力的时域解理论模型。本文证明了对于任意三维物体,如果在自由面条件简化时,假设定常兴波势为有限量阶,则在波浪绕射力公式中,不存在含有绕射势的水线积分项。从数学上证明了水线积分项反映了自由面条件中定常兴波势和不定常势之间的耦合效应。在此基础上,本文提出了在波流联合作用情况下,作用在物体上的绕射力与辅助辐射势之间的关系式,从而不须求解绕射势便可得到绕射力。  相似文献   

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