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1.
MPS方法数值模拟液舱晃荡问题 总被引：1，自引：0，他引：1
基于无网格粒子法MPS方法(moving particle semi-implicit method)研究了液舱晃荡问题。针对二维矩形液舱晃荡问题进行了数值验证,结果表明MPS方法能够很好地计算晃荡产生的拍击压力。同时将MPS方法应用到带隔板的液舱晃荡问题计算中,分析了二维和三维带隔板液舱晃荡问题。计算结果表明:隔板的存在很大程度地限制了流体的水平运动,隔板附近出现了自由面的翻卷、破碎和融合现象,MPS方法能够很好地模拟这些流动现象。计算得到的波高与实验测得的波高吻合较好,表明MPS方法模拟带隔板的晃荡问题具有一定的可靠性。 相似文献
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Unsteady nonlinear wave motions on the free surface in shallow water and over slopes of various geometries are numerically simulated using a finite difference method in rectangular grid system. Two-dimensional Navier–Stokes equations and the continuity equation are used for the computations. Irregular leg lengths and stars are employed near the boundaries of body and free surface to satisfy the boundary conditions. Also, the free surface which consists of markers or segments is determined every time step with the satisfaction of kinematic and dynamic free surface conditions. Moreover, marker-density method is also adopted to allow plunging jets impinging on the free surface. Either linear or Stokes wave theory is employed for the generation of waves on the inflow boundary. For the simulation of wave breaking phenomena, the computations are carried out with various wave periods and sea bottom slopes in surf zone. The results are compared with other existing computational and experimental results. Agreement between the experimental data and the computation results is good. 相似文献
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When a vessel is damaged, seawater floods into the damaged compartments and subsequently influences the motion of the vessel. Furthermore, the vessel’s behaviour affects the floodwater motion. In this paper, a Navier-Stokes (NS) solver with a free surface capturing technique, i.e., the volume of fluid (VOF) method, was developed to numerically simulate water flooding into a damaged vessel. To verify the developed solver, a 2-D and a 3-D dam break problems were tested. The numerical results coincide well with the experimental results and with the published numerical results. Additionally, it was used to solve the problems of linear and non-linear liquid sloshing in a hexahedral tank. The numerical results are satisfactory in comparison with the experimental results and analytical solutions. Finally, the phenomenon of water flooding into a damaged compartment of a Ro-Ro ferry was simulated numerically. The computed results are in good agreement with the experimental data. 相似文献
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《中国海洋工程》2020,(3)
Fluids and structures impact is one of the common phenomena in nature, and it widely exists in engineering practice,including ship hydrodynamic slamming, wave impact on offshore platforms, plunging wave on coastal structures,emergency landing of aircrafts at sea as well as impact of ultra-cold droplets and ice lumps under aviation conditions.In this paper, a two dimensional (2-D) solver for Navier-Stokes equations is developed and applied in the numerical simulation of the impact on a rigid plate by a liquid square. The computational domain is discretized by Finite Volume Method (FVM). The Volume of Fluid (VOF) technique is used to track the free surface and the PiecewiseLinear Interface Construction (PLIC) is used for reconstruction. The Continuum Surface Force (CSF) model is used to account for the surface tension. The convective term and the diffusive term are upwind and centrally differenced respectively. The Inner Doubly Iterative Efficient Algorithm for Linked Equations (IDEAL) is used to decouple the pressure and velocity. Based on the proposed techniques, collapse of water column is simulated and convergence study is performed for the validation of the numerical solver. Then the impact of a free falling liquid body is simulated, and the effect of volume and initial height of the liquid body is analyzed. In addition, the impact on a plate with a liquid layer is also simulated to study the effect of falling height on a liquid floor. 相似文献
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A high-order Rankine panel method based on Non-Uniform Rational B-Spline (NURBS) is developed for solving the three-dimensional radiation and diffraction problems with forward speed. A NURBS surface is used to precisely represent the body geometry. Velocity potential on the body surface is described by B-spline after the source density distribution on the boundary surface is determined. A collocation approach is applied to numerical computation and the integral equations are evaluated by applying Gauss–Legendre quadrature. The mj-terms are evaluated by a desingularized method which utilizes NURBS technique. In order to verify the method proposed, it is firstly applied to the unbounded flow problem of a sphere and spheroids. The numerical results are found to be in good agreement with analytical solutions. Then the method is used to solve the radiation and diffraction problems of a sphere and the diffraction problem of a spheroid moving with a forward speed beneath the free surface in frequency domain. The numerical results are satisfactory in comparison with the published analytical results and experimental results. 相似文献
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Sloshing, or liquid free surface oscillation, in containers has many important applications in a variety of engineering fields. The modal method can be used to solve linear sloshing problems and is the most efficient reduced order method that has been used during the previous decade. In the present article, the modal method is used to solve a nonlinear sloshing problem. The method is based on a potential flow solution that implements a two-phase analysis on sloshing in a rectangular container. According to this method, the solution to the mass conservation equation, with a nonpenetration condition at the tank walls, results in velocity potential expansion; this is similar to the mode shapes used in modal method. The kinematic and dynamic boundary conditions create a set of two-space-dimensional differential equations with respect to time. The numerical solution of this set of differential equations, in the time domain, predicts the time response of interfacial oscillations. Modal method solutions for the time response of container sloshing due to lateral harmonic oscillations show a good agreement with experimental and numerical results reported in the literature. 相似文献
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A numerical simulation algorithm based on the finite volume discretisation is presented for analyzing ship motions. The algorithm employs a fractional step method to deal with the coupling between the pressure and velocity fields. The free surface capturing is fulfilled by using a volume of fluid method in which the interface between the liquid (water) and gas (air) phases are computed by solving a scalar transport equation for the volume fraction of the liquid phase. The computed velocity field is employed to evaluate the acting forces and moments on the vessel. Using the strategy of boundary-fitted body-attached mesh and calculating all six degrees-of-freedom of motion in each time step, time history of ship motions including displacements, velocities and accelerations are evaluated.To verify the proposed algorithm, a series of verification tests are conducted. First, a two-dimensional asymmetrical wedge slamming is simulated as a simple type of a common case for high-speed vessels. Then, the steady-state forward motion of a high-speed planing catamaran is investigated. Results of both test cases show good agreement with experimental data. It is concluded that the proposed algorithm can be a promising strategy for both performance prediction and design of high-speed vessels. 相似文献
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稳恒水波的Fourier近似解研究 总被引：1，自引：0，他引：1
A computational method for steady water waves is presented on the basis of potential theory in the physical plane with spatial variables as independent quantities. The finite Fourier series are applied to approximating the free surface and potential function. A set of nonlinear algebraic equations for the Fourier coefficients are derived from the free surface kinetic and dynamic boundary conditions. These algebraic equations are numerically solved through Newton＇s iterative method, and the iterative stability is further improved by a relaxation technology. The integral properties of steady water waves are numerically analyzed, showing that （1） the set-up and the set-down are both non-monotonic quantities with the wave steepness, and （2） the Fourier spectrum of the free surface is broader than that of the potential function. The latter further leads us to explore a modification for the present method by approximating the free surface and potential function through different Fourier series, with the truncation of the former higher than that of the latter. Numerical tests show that this modification is effective, and can notably reduce the errors of the free surface boundary conditions. 相似文献
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This paper describes the simulation of the flow of a viscous incompressible Newtonian liquid with a free surface. The Navier–Stokes equations are formulated using a streamline upwind Petrov–Galerkin scheme, and solved on a Q-tree-based finite element mesh that adapts to the moving free surface of the liquid. Special attention is given to fitting the mesh correctly to the free surface and solid wall boundaries. Fully non-linear free surface boundary conditions are implemented. Test cases include sloshing free surface motions in a rectangular tank and progressive waves over submerged cylinders. 相似文献
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The method of multiple scales is used to deduce equations for three nonlinear approximations of the capillary-gravitational
disturbances of the free surface of a layer of a homogeneous liquid of constant depth. In these equations, the space-time
variations of the wave profile in the expression for the velocity potential on the liquid surface are taken into account.
On this basis, we construct asymptotic expansions up to the quantities of the third order of smallness for the velocity potential
and elevations of the liquid surface induced by running periodic waves of finite amplitude. Furthermore, we analyze the dependences
of the amplitude-phase characteristics of wave disturbances on the surface tension, depth of the liquid, and the length and
steepness of waves of the first harmonic.
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Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 25–34, September–October, 2005. 相似文献
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本文从特征值问题出发 ,结合结构系统的有限单元模型并引入单元损伤因子 ,导出了求解单元损伤因子的方程 ,从而可以确定结构的损伤位置和损伤程度。利用简支梁进行了数值模拟 ,建立了简支梁的有限单元模型 ,用不同单元弹性模量的降低来模拟各种不同的损伤工况 ,并对每种工况进行了损伤位置和损伤程度识别 ,数值模拟结果同实际情况吻合很好。 相似文献
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Oceanology - An approximate method of direct modeling of three-dimensional surface waves based on the complete equations of the potential motion of a liquid with a free surface in a curved... 相似文献
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A nonlinear liquid sloshing inside a partially filled rectangular tank has been investigated. The fluid is assumed to be homogeneous, isotropic, viscous, Newtonian and exhibit only limited compressibility. The tank is forced to move harmonically along a vertical curve with rolling motion to simulate the actual tank excitation. The volume of fluid technique is used to track the free surface. The model solves the complete Navier–Stokes equations in primitive variables by use of the finite difference approximations. At each time step, a donor–acceptor method is used to transport the volume of fluid function and hence the locations of the free surface. In order to assess the accuracy of the method used, computations are verified through convergence tests and compared with the theoretical solutions and experimental results. 相似文献
15.
Benchmark computations of wave run-up on single cylinder and four cylinders by naoe-FOAM-SJTU solver
The benchmark simulations of wave run-up on a fixed single truncated circular cylinder and four circular cylinders are presented in this paper. Our in-house CFD solver naoe-FOAM-SJTU is adopted which is an unsteady two-phase CFD code based on the open source package OpenFOAM. The Navier-Stokes equations are employed as the governing equations, and the volume of fluid (VOF) method is applied for capturing the free surface. Monochromatic incident waves with the specified wave period and wave height are simulated and wave run-up heights around the cylinder are computed and recorded with numerical virtual wave probes. The relationship between the wave run-up heights and the incident wave parameters are analyzed. The numerical results indicate that the presented naoe-FOAM-SJTU solver can provide accurate predictions for the wave run-up on one fixed cylinder and four cylinders, which has been proved by the comparison of simulated results with experimental data. 相似文献
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This paper is concerned with the interaction of bubbles, a submerged or floating structure, and free surface waves. A three-dimensional fully nonlinear model has been developed based on the coupling of the boundary integral method (BIM) for bubble dynamics and free surface waves and the finite element method for structure deformation. The present method is well validated by comparing the numerical results with the experimental data. Three structure characteristics, including fixed, rigidly moving and flexible, are investigated separately to determine their influence on bubble dynamics. For a free-floating structure, the free surface causes not only a larger reduction in peak pressure for a rigid structure compared with a fixed body but also the modification of the bubble period and structural response. The interaction between a bubble and a flexible structure, in the absence of a free surface, is simulated. Both the rigid motion and the deformation at the local structure appear in the simulation. The effect of the structural thickness on the reduction in peak pressure is also considered. 相似文献
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In this study, we develop a numerical method for a 3D linear hydroelastic analysis of floating structures with liquid tanks subjected to surface regular water waves and compare the numerical results with experimental tests. Considering direct couplings among structural motion, sloshing, and water waves, a mathematical formulation and a numerical method extended from a recent work [1] are developed. The finite element method is employed for the floating structure and internal fluid in tanks, and the boundary element method is used for the external fluid. The resulting formulation completely incorporates all the interaction terms including hydrostatic stiffness and the irregular frequency effect is removed by introducing the extended boundary integral equations. Through various numerical tests, we verify the proposed numerical method. We also performed 3D hydroelastic experimental tests of a floating production unit (FPU) model in an ocean basin. The measured dynamic motions are compared with the numerical results obtained using the proposed method. 相似文献
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Coastal disposal of waste water can be idealized as the problem of a jet under random waves. Understanding of this phenomenon is important for engineering design and environmental impact assessment. The present study aims to simulate such phenomenon by using a 3D numerical model based on the solution of the spatially filtered and σ-transformed Navier–Stokes equations with dynamic sub-grid scale model of turbulence. The numerical solution procedures are split into three steps: advection, diffusion and pressure propagation, and a Lagrange–Euler method is used to track the free surface. Cases of vertical jet in stagnant water, pure random waves and vertical jet in random waves are simulated with the same grid system for comparative study. Different methods of generating jet inflow turbulence have been tested and the method of jet azimuthal modes is found to be the optimum. The numerical results reproduce the distinct characteristics of jet in waves, including faster decay of centerline velocity, wider lateral spreading and the occurrence of wave tractive mechanism. 相似文献
20.
Three-dimensional liquid sloshing in a tank with baffles 总被引：1，自引：0，他引：1
Dongming Liu 《Ocean Engineering》2009,36(2):202-52
A numerical model has been developed to study three-dimensional (3D) liquid sloshing in a tank with baffles. The numerical model solves the spatially averaged Navier-Stokes equations, which are constructed on a non-inertial reference frame having six degree-of-freedom (DOF) of motions. The large-eddy-simulation (LES) approach is employed to model turbulence by using the Smagorinsky sub-grid scale (SGS) closure model. The two-step projection method is employed in the numerical solutions, aided by the Bi-CGSTAB technique to solve the pressure Poisson equation for the filtered pressure field. The second-order accurate volume-of-fluid (VOF) method is used to track the distorted and broken free surface. The baffles in the tank are modeled by the concept of virtual boundary force (VBF) method. The numerical model is first validated against the available analytical solution and experimental data for two-dimensional (2D) liquid sloshing in a tank without baffles. The 2D liquid sloshing in tanks with baffles is then investigated. The numerical results are compared with other results from available literatures. Good agreement is obtained. Finally, the model is used to study 3D liquid sloshing in a tank with vertical baffles. The effect of the baffle is investigated and discussed. 相似文献