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1.
A Corrected Incompressible SPH (CISPH) method is proposed for accurate tracking of water surface in breaking waves. Corrective terms are derived based on a variational approach to ensure the angular momentum preservation of Incompressible SPH (ISPH) formulations. The proposed CISPH method is applied to solve the Navier–Stokes equation for simulating the breaking and post-breaking of solitary waves on a plane slope. The enhanced precision (compared to the ISPH method) of the CISPH method is confirmed through both qualitative and quantitative comparisons with experimental data. The introduction of corrective terms significantly improves the capability and the accuracy of the ISPH method in the simulation of wave breaking and post-breaking. 相似文献
2.
The paper presents an Incompressible Smoothed Particle Hydrodynamics (ISPH) method to simulate wave interactions with a porous medium. The SPH method is a mesh free particle modeling approach that is capable of tracking the large deformation of free surfaces in an easy and accurate manner. The ISPH method employs a strict incompressible hydrodynamic formulation to solve the fluid pressure and the numerical solution is obtained by using a two-step semi-implicit scheme. The ISPH flow model solves the unsteady 2D Navier–Stokes (NS) equations for the flows outside the porous media and the NS type model equations for the flows inside the porous media. The presence of porous media is considered by including additional friction forces into the equations. The developed ISPH model is first validated by the solitary and regular waves damping over a porous bed and the solitary wave interacting with a submerged porous breakwater. The convergence of the method and the sensitivity of relevant model parameters are discussed. Then the model is applied to the breaking wave interacting with a breakwater covered with a layer of porous materials. The computational results demonstrate that the ISPH flow model could provide a promising simulation tool in coastal hydrodynamic applications. 相似文献
3.
A new criterion is proposed for a more efficient assessment of free-surface particles in a particle-based simulation. Enhanced wave impact simulations are carried out by improved Incompressible SPH (ISPH) methods. The first improvement is the same as that in the Corrected ISPH (CISPH; [Khayyer A, Gotoh, H, Shao SD. Corrected incompressible SPH method for accurate water-surface tracking in breaking waves, Coast Eng 2008; 55 (3): 236–250]) method and is proposed for the improvement of momentum conservation. The second improvement is achieved by deriving and employing a higher order source term based on a more accurate differentiation to obtain a less fluctuating and more accurate pressure field. The enhanced performance of improved ISPH methods is demonstrated through the simulation of several fluid impact simulations in comparison with the experimental data and simulation results by other numerical methods. 相似文献
4.
Smoothed Particle Hydrodynamics method (SPH) has a good adaptability for simulating of free surface flow problems. However, there are some shortcomings of SPH which are still in open discussion. This paper presents a corrected solid boundary handling method for weakly compressible SPH. This improved method is very helpful for numerical stability and pressure distribution. Compared with other solid boundary handling methods, this corrected method is simpler for virtual ghost particle interpolation and the ghost particle evaluation relationship is clearer. Several numerical tests are given, like dam breaking, solitary wave impact and sloshing tank waves. The results show that the corrected solid boundary processing method can recover the spurious oscillations of pressure distribution when simulating the problems with complex geometry boundary. 相似文献
5.
This paper presents a numerical model for simulating wave interaction with porous structures. Incompressible smoothed particle hydrodynamics in porous media (ISPHP) method is introduced in this study as a mesh free particle approach that is capable of efficiently tracking the large deformation of free surfaces in a Lagrangian coordinate system. The developed model solves two porous and pure fluid flows simultaneously by means of one equation that is equivalent to the unsteady 2D Navier–Stokes (NS) equations for the flows outside the porous media and the extended Forchheimer equation for the flows inside the porous media. Interface boundary between pure fluid and porous media is effectively modeled by the SPH integration technique. A two-step semi-implicit scheme is also used to solve the fluid pressure satisfying the fluid incompressibility criterion.The developed ISPHP model is then validated via different experimental and numerical data. Fluid flow pattern through porous dam with different porosities is studied and regular wave attenuation over porous seabed is investigated. As a practical case, wave running up and overtopping on a caisson breakwater protected by a porous armor layer are modeled. The results show good agreements between numerical and laboratory data in terms of free surface displacement, overtopping rate and pressure distribution. Based on this study, ISPHP model is an efficient method for simulating the coastal applications with porous structures. 相似文献
6.
In this work, sloshing flows were successfully simulated by using a coupled numerical scheme between smoothed particle hydrodynamics (SPH) and smoothed point interpolation method (S-PIM) (SPH-SPIM coupled method). SPH is a Lagrangian particle method to solve flow fields while S-PIM is developed to deal with the structure dynamics. A coupling scheme is proposed, the key of which is that the fluid and solid fields are not necessary to be discretized by the same resolution. The stability, accuracy, convergence and conservation of the SPH-SPIM coupled method were validated by the case of hydrostatic water column on an elastic plate. Then, a wave impact problem was simulated to verify that the present SPH method worked well for sloshing flows. Finally, two sloshing problems with an elastic baffle were simulated, which validated the accuracy and stability of the method in predicting the fluid-structure interaction (FSI) features during the process of sloshing. It has been found that both the shape of the free surface and the large deformation of the elastic baffle can be well captured by the present method, which shows the potential of the present method to be a good candidate for simulating sloshing problems. 相似文献
7.
Modified Moving Particle method in Porous media (MMPP) is introduced in this study for simulating a flow interaction with porous structures. By making use of the sub-particle scale (SPS) turbulence model, a unified set of equations are introduced for the entire computational domain and a proper boundary treatment is suggested at the interfaces between fluid and the porous media. Similar to the Incompressible Smoothed Particle Hydrodynamic (ISPH) method, a robust two-step semi-implicit scheme is utilized to satisfy the incompressibility criterion. By means of the introduced model, different flow regimes through multi-layered porous structures with arbitrary shapes can be simulated and there is no need to implement calibration factors.The developed MMPP model is then validated via simulating the experiments of Liu et al. (1999) i.e. linear and turbulent flows through porous dams and the experiments of Sakakiyama and Liu (2001) i.e. wave overtopping on a caisson breakwater protected by multi layered porous materials. Good agreements between numerical and laboratory data present the ability of the introduced model in simulating various flow regimes through multi-layered porous structures. It is concluded that the turbulent flow is an important issue particularly at the interface between the free fluid and porous media and consequently, the accuracy of the previous Lagrangian models that were based on neglecting the turbulence effect can be improved significantly by means of the present model. In addition, to satisfy the continuity criteria in the SPH models, it is necessary to modify density of particles in accordance with their porosity. 相似文献
8.
Liquid sloshing in storage tank is a fundamental problem of great engineering importance. Sloshing motion can be laminar or turbulent. However, the necessity for inclusion of turbulence in CFD simulation of sloshing flows has not yet been established. In this paper, three roll–induced sloshing cases are studied to assess the merits and shortcomings of the laminar model and three most–commonly used turbulence models (RANS k–ε, LES and Very LES). To overcome the deficiencies in the RANS and LES, the new Very LES (VLES) model, which combines the RANS k–ε and LES, is developed in this paper. The free surface profiles are reconstructed by a coupled Level–Set and Volume–of–Fluid (CLSVOF) method. To the authors’ knowledge, the comprehensive and systematical assessment of the effect of turbulence on sloshing simulation has not been reported in the literature. The numerical results are evaluated using experimental measurements from Delorme and Souto−Iglesias. The present study indicates that the inclusion of an appropriate turbulence model has a profound influence on the simulations of violent and non–violent sloshing flows. The VLES and LES models can provide accurate predictions of free surface profiles and impact pressures, whereas the laminar flow assumption and the RANS model cannot adequately capture the energy dissipation in the sloshing simulation and lead to the inaccurate flow predictions. 相似文献
9.
Numerical simulation of sloshing with large deforming free surface by MPS-LES method 总被引：1，自引：1，他引：0
Moving particle semi-implicit (MPS) method is a fully Lagrangian particle method which can easily solve problems with violent free surface. Although it has demonstrated its advantage in ocean engineering applications, it still has some defects to be improved. In this paper, MPS method is extended to the large eddy simulation (LES) by coupling with a sub-particle-scale (SPS) turbulence model. The SPS turbulence model turns into the Reynolds stress terms in the filtered momentum equation, and the Smagorinsky model is introduced to describe the Reynolds stress terms. Although MPS method has the advantage in the simulation of the free surface flow, a lot of non-free surface particles are treated as free surface particles in the original MPS model. In this paper, we use a new free surface tracing method and the key point is "neighbor particle". In this new method, the zone around each particle is divided into eight parts, and the particle will be treated as a free surface particle as long as there are no "neighbor particles" in any two parts of the zone. As the number density parameter judging method has a high efficiency for the free surface particles tracing, we combine it with the neighbor detected method. First, we select out the particles which may be mistreated with high probabilities by using the number density parameter judging method. And then we deal with these particles with the neighbor detected method. By doing this, the new mixed free surface tracing method can reduce the mistreatment problem efficiently. The serious pressure fluctuation is an obvious defect in MPS method, and therefore an area-time average technique is used in this paper to remove the pressure fluctuation with a quite good result. With these improvements, the modified MPS-LES method is applied to simulate liquid sloshing problems with large deforming free surface. Results show that the modified MPS-LES method can simulate the large deforming free surface easily. It can not only capture the large impact pressure accurately on rolling tank wall but also can generate all physical phenomena successfully. The good agreement between numerical and experimental results proves that the modified MPS-LES method is a good CFD methodology in free surface flow simulations. 相似文献
10.
The interaction between solid structures and free-surface flows is investigated in this study. A Smoothed Particle Hydrodynamics (SPH) model is used in the investigation and is verified against analytical solutions and experimental observations. The main aim is to examine the effectiveness of a tsunami-resistant house design by predicting the wave loads on it. To achieve this, the solitary wave generation and run-up are studied first. The solitary wave is generated by allowing a heavily weighted block to penetrate into a tank of water at one end, and the near-shore seabed is modelled by an inclined section with a constant slope. Then, the SPH model is applied to simulate the three-dimensional flows around different types of houses under the action of a solitary wave. It has been found that the tsunami-resistant house design reduces the impact force by a factor of three. 相似文献
11.
《Coastal Engineering》2006,53(9):723-735
The paper presents an incompressible Smoothed Particle Hydrodynamics (SPH) model to investigate the wave overtopping of coastal structures. The SPH method is a grid-less Lagrangian approach which is capable of tracking the large deformations of the free surface with good accuracy. The incompressible algorithm of the model is implemented by enforcing the constant particle density in the pressure projection. The SPH model is employed to reproduce a transient wave overtopping over a fixed horizontal deck and the regular/irregular waves overtopping of a sloping seawall. The computations are validated against the experimental and numerical data and a good agreement is observed. The SPH modelling is shown to provide a promising tool to predict the overtopping characteristics of different waves. The present model is expected to be of practical purpose if further improvement in the spatial resolution and CPU time can be adequately made. 相似文献
12.
Floating structures are commonly seen in coastal and offshore engineering. They are often subjected to extreme waves and, therefore, their nonlinear dynamic behaviors are of great concern. In this paper, an in-house CFD code is developed to investigate the accurate prediction of nonlinear dynamic behaviors of a two-dimensional (2-D) box-shaped floating structure in focused waves. Computations are performed by an enhanced Constrained Interpolation Profile (CIP)-based Cartesian grid model, in which a more accurate VOF (Volume of Fluid) method, the THINC/SW scheme (THINC: tangent of hyperbola for interface capturing; SW: Slope Weighting), is used for interface capturing. A focusing wave theory is used for the focused wave generation. The wave component of constant steepness is chosen. Comparisons between predictions and physical measurements show good agreement including body motions and free surface profiles. Although the overall agreement is good, some discrepancies are observed for impact pressure on the superstructure due to water on deck. The effect of grid resolution on the results is checked. With a fine grid, no obvious improvement is seen in the global body motions and impact pressures due to water on deck. It is concluded that highly nonlinear phenomena, such as distorted free surface, large-amplitude body motions, and violent impact flow, have been predicted successfully. 相似文献
13.
针对近岸海域极端海况的防灾减灾问题,准确模拟追踪海啸波传播过程,再现液面局部射流、崩破波等波面湍动现象。建立SPH数值水槽,边界条件基于固壁粒子法,减少海堤坡角改变对计算域精度的影响,讨论粒子间距设置对模拟精度的影响。模拟7种不同海堤坡角下波浪的爬高与衰减情况,讨论了海堤坡角变化对消波系数的影响。当粒子间距设置为0.002 m时,模型能准确地捕捉海啸波的强非线性现象。随着海堤坡角增大,海啸波峰值爬升率增大,波浪越堤后因崩破波的产生,波能衰减进一步加剧。当坡角较小时,消波系数随坡角的增大提升明显,而后趋于缓慢增长。 相似文献
14.
A shared-memory parallelization is implemented to the recently developed Consistent Particle. Method (CPM) for violent wave impact problems. The advantages of this relatively new particle method lie in four key aspects: (1) accurate computation of Laplacian and gradient operators based on Taylor series expansion, alleviating spurious pressure fluctuation and being able to model two-phase flows characterized by large density difference, (2) a thermodynamics-based compressible solver for modelling compressible air that eliminates the need of determining artificial sound speed, (3) seamless coupling of the compressible air solver and incompressible water solver, and (4) parallelization of the numerical model based on Open Multi-Processing (OpenMP) and a parallel direct sparse solver (Pardiso) to significantly improve computational efficiency. Strong and weak scaling analyses of the parallelized CPM are conducted, showing an efficiency speedup of 100 times or more depending on the size of simulated problem. To demonstrate the accuracy of the developed numerical model, three numerical examples are studied including the benchmark study of wave impact on seawall, and our experimental studies of violent water sloshing under rotational excitations and sloshing impact with entrapped air pocket. CPM is shown to accurately capture highly deformed breaking waves and violent wave impact pressure including pressure oscillation induced by air cushion effect. 相似文献
15.
Liquid sloshing is a common phenomenon in the liquid tanks transportation. Liquid waves lead to fluctuating forces on the tank wall. Uncontrolled fluctuations lead to large forces and momentums. Baffles can control these fluctuations. A numerical method, which has been widely used to model this phenomenon, is Smoothed Particle Hydrodynamics(SPH). The Lagrangian nature of this method makes it suitable for simulating free surface flows. In the present study, an accurate Incompressible Smoothed Particle Hydrodynamics(ISPH) method is developed and improved using the kernel gradient correction tensors, particle shifting algorithms, k–ε turbulence model, and free surface particle detectors. Comparisons with the experimental data approve the ability of the present algorithm for simulating shallow water sloshing. The main aim of this study is to investigate the effects of the vertical baffle on the damping of liquid sloshing. Results show that baffles number has a major role in sloshing fluctuation damping. 相似文献
16.
A smoothed particle hydrodynamic (SPH) model is developed to simulate wave interaction with porous structures. The mean flow outside the porous structures is obtained by solving Reynolds Averaged Navier–Stokes (RANS) equations and the turbulence field is calculated by a large eddy simulation (LES) model. The porous flow is described by the spatially averaged Navier–Stokes type equations with the resistance effect of the porous media being represented by an empirical frictional source term. The interface boundaries between the porous flow and the outside flow are modeled by means of specifying a transition zone along the interface. The model is validated against other available numerical results and experimental data for wave damping over porous seabed with different levels of permeability. The validated model is then employed to investigate wave breaking over a submerged porous breakwater and good agreements between the SPH model results and the experimental data are obtained in terms of free surface displacement. In addition the predicted velocity, vorticity and pressure fields near the porous breakwater and in the breaking wave zone are also analyzed. 相似文献
17.
由于在前壁上设置了尺寸较小的孔,开孔沉箱受流体黏性力作用显著,依照弗劳德数相似准则设计模型存在比尺效应。为揭示比尺效应,建立了模拟波浪与开孔沉箱相互作用的光滑粒子流体动力学(SPH)模型。其中流体运动由连续性方程和Navier-Stokes方程控制,固壁边界由改进的动力边界粒子施加。模型收敛性通过分析不同粒子分辨率下的波浪反射系数得到,模型精度通过比较计算与理论波浪反射系数证明。使用经过验证的SPH模型,计算并比较了不同几何比尺和开孔率下开孔沉箱附近的涡量场、箱体外侧的波面时程曲线和波浪反射系数。结果表明,随着模型几何比尺的减小,开孔沉箱受到偏大的流体黏性力,致使更多波能在湍流运动中耗散,进而减小了波浪反射系数并降低了箱体外侧的波面高度。 相似文献
18.
When ordinary Smoothed Particle Hydrodynamics (SPH) method is used to simulate wave propagation in a wave tank, it is usually observed that the wave height decays and the wave length elongates along the direction of wave propagation. Accompanied with this phenomenon, the pressure under water decays either and shows a big oscillation simultaneously. The reason is the natural potential tensile instability of modeling water motion with ordinary SPH which is caused by particle negative stress in the computation. To deal with the problems, a new sextic kernel function is proposed to reduce this instability. An appropriate smooth length is given and its computation criterion is also suggested. At the same time, a new kind dynamic boundary condition is introduced. Based on these improvements, the new SPH method named stability improved SPH (SISPH) can simulate the wave propagation well. Both the water surface and pressure can be well expressed and the oscillation of pressure is nearly eliminated. Compared with other improved methods, SISPH can truly reveal the physical reality without bringing some new problems in a simple way. 相似文献
19.
The high-speed impact between a body and water is an important practical problem, whether due to wave impact on a structural deck or wall, or due to a moving body such as a ship or aircraft hitting water. The very high pressures exerted are difficult to predict and the role of air may be significant. In this paper, numerical simulations are undertaken to investigate the impact of a rigid horizontal plate onto a wave crest and, in the limit, onto a flat water surface. A two-phase incompressible–compressible smoothed particle hydrodynamics (SPH) method for water and air, respectively, is applied where the water phase imposes kinematics on the air phase at the air–water interface and the air phase imposes pressures on the water at the interface. Results are compared with experimental measurements undertaken using a drop rig positioned over a wave flume so that a horizontal plate impacts the water surface in free flight. Numerical predictions of impact pressure are quite accurate; air is shown to have a significant cushioning effect for impact on to flat water and this reduces for waves as the ratio of wave height to wavelength increases. 相似文献
20.
Ditching often takes place for a ground-effect wing (WIG) ship. During the ditching, the extreme load developed by water impacts may cause damages to structures, posing a great threat to the safety of crew and passengers. In the paper, a weakly compressible smoothed particle hydrodynamics (SPH) model combined with enhanced numerical techniques has been adopted to tackle the ditching problems. In order to handle the motion of a rigid body in the three-dimensional ditching problems, the six degrees-of-freedom (6-DOF) equations of motion are incorporated into the SPH scheme. The accuracy of the SPH model is validated through two benchmarks, respectively, the two-dimensional wedge water entry and the three-dimensional stone-skipping. The former is aimed to validate the prediction of pressures during the free surface impact while the latter is a good case for testing the coupling motions of the rigid body. Furthermore, the ditching of the real scale WIG ship under different conditions is simulated with the established SPH model, through which some useful conclusions are drawn. 相似文献