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1.
Numerical Wave Channel with Absorbing Wave-Maker 总被引：2，自引：0，他引：2
Wang Yongxue
Professor State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian 《中国海洋工程》1995,(2)
The numerical wave channel has been developed based on the volume of fluid method (VOF) in conjunction with the Navier-Stokes equations. The absorbing wave-maker boundary on the left side of the channel is presented by prescribing velocity reference to linear wave-maker theory. The principle of which is that the numerical wave-maker is designed to move in a way that generates the required incident wave and cancels out any reflected wave that reach it at the same time. On the right side of the channel, the open boundary is set to permit incident waves to be transmitted freely. The parametric studies have been carried out at a range of ratios of water depth to wave length d/ L from 0.124 to 0.219, with wave height in the front of paddle/water depth ratio (H0 / d) from 0.1 to 0.3. Wave height, wave pressure distribution along the channel and velocity field are obtained for both open boundary condition and reflective boundary condition at the other end of the channel. For a reflective case, it is shown that 相似文献
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A mathematical model has been developed to analyze the influence of extreme water waves over multiconnected regions in Visakhapatnam Port, India by considering an average water depth in each multiconnected regions. In addition, partial reflection of incident waves on coastal boundary is also considered. The domain of interest is divided mainly into two regions, i.e., open sea region and harbor region namely as Region-I and Region-II, respectively. Further, Region-II is divided into multiple connected regions. The 2-D boundary element method (BEM) including the Chebyshev point discretization is utilized to solve the Helmholtz equation in each region separately to determine the wave amplification. The numerical convergence is performed to obtain the optimum numerical accuracy and the validation of the current numerical approach is also conducted by comparing the simulation results with existing studies. The four key spots based on the moored ship locations in Visakhapatnam Port are identified to perform the numerical simulation. The wave amplification at these locations is estimated for monochromatic incident waves, considering approximate water depth and different reflection coefficients on the wall of port under the resonance conditions. In addition, wave field analysis inside the Visakhapatnam Port is also conducted to understand resonance conditions. The current numerical model provides an efficient tool to analyze the amplification on any realistic ports or harbors.
相似文献4.
If the upstream boundary conditions are prescribed based on the incident wave only, the time-dependent numerical models cannot effectively simulate the wave field when the physical or spurious reflected waves become significant. This paper describes carefully an approach to specifying the incident wave boundary conditions combined with a set sponge layer to absorb the reflected waves towards the incident boundary. Incorporated into a time-dependent numerical model, whose governing equations are the Boussinesq-type ones, the effectiveness of the approach is studied in detail. The general boundary conditions, describing the down-wave boundary conditions are also generalized to the case of random waves. The numerical model is in detail examined. The test cases include both the normal one-dimensional incident regular or random waves and the two-dimensional oblique incident regular waves. The calculated results show that the present approach is effective on damping the reflected waves towards the incident wave boundary. 相似文献
5.
SUN Dapeng LI Yucheng TENG Bin
Associate Professor the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian
Professor the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian 《中国海洋工程》1999,(2)
For higher accuracy in simulating the transformation of three dimensional waves,in consid-eration of the advantages of constant panels and linear elements,a combined boundary elements is appliedin this research.The method can be used to remove the transverse vibration due to the accumulation ofcomputational errors.A combined boundary condition of sponge layer and Sommerfeld radiation condi-tion is used to remove the reflected waves from the computing domain.By following the water particle onthe water surface,the third order Stokes wave transform is simulated by the numerical wave flume tech-nique.The computed results are in good agreement with theoretical ones. 相似文献
6.
The problem of wave propagation in a fully nonlinear numerical wave tank is studied using desingularized boundary integral equation method coupled with mixed Eulerian–Lagrangian formulation. The present method is employed to solve the potential flow boundary value problem at each time step. The fourth-order predictor–corrector Adams–Bashforth–Moulton scheme is used for the time-stepping integration of the free surface boundary conditions. A damping layer near the end-wall of wave tank is added to absorb the outgoing waves with as little wave reflection back into the wave tank as possible. The saw-tooth instability is overcome via a five-point Chebyshev smoothing scheme. The model is applied to several wave propagations including solitary, irregular and random incident waves. 相似文献
7.
《Coastal Engineering》2004,51(1):17-34
Approximate equations for the elliptic mild slope equation are derived based on Padé approximation and used as absorbing boundaries. The new boundary equations can absorb the incident waves for high range of wave incidence angle. In addition, the new boundary equations can be used iteratively to refine the solution by eliminating reflections from the boundaries. An iterative conjugate gradient scheme has been used to solve the elliptic water wave equation and the new boundary equations. The model developed can accommodate for wave diffraction, refraction and reflections from structures with wide range of wave angles at the boundaries. The new model has been tested for several cases. The model compares very well with other models. 相似文献
8.
WANG Yongxue ZANG Jun QIU Dahong Professor the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian P. R. China
Lecturer the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian P. R. China
Professor Academician of Chinese Academy of Sciences the State Key Laboratory of Coastal Offshore Engineering Dalian University of Technology Dalian P. R. China 《中国海洋工程》1999,(4)
The volume of fluid(VOF)method is used to set up a wave flume with an absorbing wavemaker of cnoidal waves.Based on the transfer function between wave surface and paddle velocity obtained bythe shallow water wave theory,the velocity boundary condition of an absorbing wave maker is introduced toabsorb reflected waves that reach the numerical wave maker.For H/d ranging from 0.1 to 0.59 and T(g/d)~(1/2)from 7.9 to 18.3,the parametric studies have been carried out and compared with experiments. 相似文献
9.
为了研究斜向入射波浪,基于三维不可压缩两相流模型,开发了一套圆形数值波浪水池数值模型。在圆形波浪水池中,通过源项造波法成功生成了任意入射方向的波浪,并且利用人工摩擦项模拟阻尼区以数值耗散反射波浪。模型基于嵌入式多块网格体系,采用FVM法(finite volume method)离散Navier-Stokes方程,VOF法(volume of fluid)追踪自由水面。试验结果表明,斜向入射波浪的模拟结果与理论值基本一致,圆形波浪水池在模拟斜向入射波浪时,有效区域的面积较传统波浪水池显著增大,而且有效区域受波浪入射角度的影响也较小。同时,通过叠加多列斜向入射波浪,模拟出了多向交叉波列,并通过与理论结果对比,发现其具有较高的精度。 相似文献
10.
The interaction of obliquely incident surface gravity waves with a vertical flexible permeable submerged membrane wave barrier is investigated in the context of three-dimensional linear water wave theory. From the general formulation of the submerged membrane barrier, the performance of bottom-standing, surface-piercing and fully extended membrane wave barriers are analyzed for various values of wave and structural parameters. The analytic solution of the physical problem is obtained using eigenfunction expansion method and a coupled boundary element-finite difference method has been used to get the numerical solution. In the boundary element method, since the boundary condition on the membrane barrier is not known a priori, the membrane response and velocity potentials are solved simultaneously using appropriate discretization with the help of finite difference scheme. The convergence of the analytic and numerical solution techniques is discussed. The study reveals that for suitable combination of wave and structural parameters, approximately (45–50)% incident wave energy can be dissipated irrespective of membrane barrier configurations. Further, in certain situations, nearly full wave reflection and zero transmission occur for all barrier configurations. The study will be useful in the design of flexible permeable membrane to act as an effective wave barrier for creation of tranquility zone in the marine environment. 相似文献
11.
The objective of the present work is to discuss the implementation of an active wave generating–absorbing boundary condition for a numerical model based on the Volume Of Fluid (VOF) method for tracking free surfaces. First an overview of the development of VOF type models with special emphasis in the field of coastal engineering is given. A new type of numerical boundary condition for combined wave generation and absorption in the numerical model VOFbreak2 is presented. The numerical boundary condition is based on an active wave absorption system that was first developed in the context of physical wave flume experiments, using a wave paddle. The method applies to regular and irregular waves. Velocities are measured at one location inside the computational domain. The reflected wave train is separated from the incident wave field in front of a structure by means of digital filtering and subsequent superposition of the measured velocity signals. The incident wave signal is corrected, so that the reflected wave is effectively absorbed at the boundary. The digital filters are derived theoretically and their practical design is discussed. The practical use of this numerical boundary condition is compared to the use of the absorption system in a physical wave flume. The effectiveness of the active wave generating–absorbing boundary condition finally is proved using analytical tests and numerical simulations with VOFbreak2. 相似文献
12.
A three-dimensional modeling of multidirectional random-wave diffraction by a group of rectangular submarine pits is presented in this paper. The fluid domain is divided into N interior regions representing the pit area and an overall exterior region separated by the imaginary pit boundaries. In the interior region, the analytical expressions of the Fourier series expansion for velocity potentials in the pit regions have been derived with the unknown coefficients determined from a series of Green's function based boundary integral equations. The boundary integral approach has also been applied to obtain the velocity potential and free-surface elevation in the exterior region. The Pierson–Moskowitz (P–M) frequency spectrum was selected for the random wave simulation using the superposition of solutions of a finite number of decomposed wave components. Numerical results for the cases of regular waves and random waves are presented to examine the influences of the pit geometry and incident wave condition on the overall wave field. The general diffraction pattern of alternate bands of increase and decrease of relative wave height in front of the pit system can be observed. It is found that, in the shadow region, the relative wave height is reduced. As the number of pit increases, the effectiveness of reducing the relative wave height behind the multiple-pit system increases. However, the relative wave height within the pit area and in front of the leading pit shows increasing trend. It is noticed that under the random-wave condition, the level of increase and decrease of the relative wave height due to the existence of submarine pits is less pronounced than that observed from results in regular-wave condition. 相似文献
13.
港口中系泊船在波浪作用下运动问题的本质是浅水波浪与浮体的相互作用。与深水情况不同,浅水问题应当考虑水底、水域边界的影响及浅水波浪自身的特性,单一模型很难实现该模拟过程。为此,建立了Boussinesq方程计算入射波和Laplace方程计算散射波的全时域组合计算模型。有限元法求解的Boussinesq方程能使入射波充分考虑到水底、水域边界的影响和浅水波浪的特性;散射波被线性化,采用边界元法求解,并以浮体运动时的物面条件为入射波和散射波求解的匹配条件。该方法为完全的时域方法,计算网格不随时间变动,计算过程较为方便。通过与实验及其他数值方法的结果进行比较,验证了本模型对非线性波面、浮体的运动都有比较理想的计算结果,显示了本模型对非线性问题具有较好的计算能力。 相似文献
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An analytical solution using homotopy analysis method is developed to describe the nonlinear progressive waves in water of finite depth. The velocity potential of the wave is expressed by Fourier series and the nonlinear free surface boundary conditions are satisfied by continuous mapping. Unlike the perturbation method, the present approach is not dependent on small parameters. Thus solutions are possible for steep waves. Furthermore, a significant improvement of the convergence rate and region is achieved by applying Homotopy-Padé Approximants. The calculated wave characteristics of the present solution agree well with previous numerical and experimental results. 相似文献
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Real waves are multidirectional waves.In the present study,the calculation method for the wave maker driving signals for generating multidirectional wave groups in physical wave basin is proposed.Its validity is first confirmed by a numerical model for which the incident boundary condition is determined by use of the proposed method.Then,the physical simulation of multidirectional wave groups is performed in laboratory wave basin.The experimental results show that multidirectional waves with expected wave groupiness,which includes not only its group height but also its group length,can be satisfactorily generated at the specified position in the physical wave basin. 相似文献
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1.IntroductionGreat efforts have been devoted to the protection of coastal areas over many years by erectingdikes,seawalls,groin systems,and detached breakwaters.The sea walls,jetties,detached breakwa-ters,etc.are traditionally adopted as absorbingfacilit… 相似文献
18.
四叉树网格下的椭圆型缓坡方程数值模型研究 总被引：1，自引：1，他引：0
波浪是近岸海域关键的水动力因素之一。考虑到近岸地形复杂、波浪演化显著的特点,建立了四叉树网格体系下的椭圆型缓坡方程数值模型,采用有限体积法对模型进行数值离散,应用GPBiCG(m, n)算法求解离散后的控制方程。模型中根据波浪波长布局计算网格,生成多层次四叉树网格,对复杂计算域有较好的适应性,并且在离散和方程求解中无需引入形函数、不产生复杂的交叉项,节约了存储空间和计算时间。将模型成功应用于物理模型实验及Acapulco海湾的波浪场数值模拟,结果表明该模型能够准确、高效地模拟近岸波浪场,可为近岸波浪场的模拟提供一定的理论和技术支持。 相似文献
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A time-domain higher-order boundary element scheme was utilized to simulate the linear and nonlinear irregular waves and diffractions due to a structure. Upon the second-order irregular waves with four Airy wave components being fed through the inflow boundary, the fully nonlinear boundary problem was solved in a time-marching scheme. The open boundary was modeled by combining an absorbing beach and the stretching technique. The proposed numerical scheme was verified by simulating the linear regular and irregular waves. The scheme was further applied to compute the linear and nonlinear irregular wave diffraction forces acting on a vertical truncated circular cylinder. The nonlinear results were also verified by checking the accuracy of the nonlinear simulation. 相似文献
20.
With growing computational power, the first-order wave-maker theory has become well established and is widely used for numerical wave flumes. However, existing numerical models based on the first-order wave-maker theory lose accuracy as nonlinear effects become prominent. Because spurious harmonic waves and primary waves have different propagation velocities, waves simulated by using the first-order wave-maker theory have an unstable wave profile. In this paper, a numerical wave flume with a piston-type wave-maker based on the second-order wave-maker theory has been established. Dynamic mesh technique was developed. The boundary treatment for irregular wave simulation was specially dealt with. Comparisons of the free-surface elevations using the first-order and second-order wave-maker theory prove that second-order wave-maker theory can generate stable wave profiles in both the spatial and time domains. Harmonic analysis and spectral analysis were used to prove the superiority of the second-order wave-maker theory from other two aspects. To simulate irregular waves, the numerical flume was improved to solve the problem of the water depth variation due to low-frequency motion of the wave board. In summary, the new numerical flume using the second-order wave-maker theory can guarantee the accuracy of waves by adding an extra motion of the wave board. The boundary treatment method can provide a reference for the improvement of nonlinear numerical flume. 相似文献