Numerical Wave Flume Study on Wave Motion Around Submerged Plates

1 .IntroductionApile supportedplatesubmergedatacertaindepthunderseasurfacewasdevelopedasanewtypeofunderwaterbreakwaterfortheprotectionofcoastlinesandharbors .Thisisbecauseitdoesnothinderthewaterexchangebetweentheopenseaandtheprotectedareanordoesithindertheviewovertheopensea .Besides,itislessdependentonthegeotechnicalconditionsoftheseabottomwherethestructureistobeinstalled ;however,itscostishigh ,particularlyinrelativelydeepwaters .Formanyapplicationsitispossibletoreducethewavemotionintheprotec…     

Numerical Model of Internal Solitary Wave Evolution on Impermeable Variable Seabed in A Stratified Two-Layer Fluid System

1.IntroductionIn mathematics and physics,a soliton is a self-reinforcing solitary wave caused by nonlinear ef-fectsinthe medium.Solitons are found in many physical phenomena(Chou and Shih,1996;Chouand Quyang,1999;Chouet al.,2003;Chenet al.,2004;Wang,2004;…     

Numerical Simulation of Tidal Current in a Bay

—Based on the multilevel model,numerical calculations of tidal current affected by the M_2 tidein the Tokyo Bay have been carried out.The results of calculation are compared with the data observed inthe Tokyo Bay and the result calculated by an approximate formula as the Tokyo Bay is regarded as a rec-tangular bay,and good agreement is found.It is proved that the mathematical model and the calculationmethod are correct and useable.     

岩体裂隙网络非线性渗流特性研究

基于人工交叉裂隙模型,通过室内透水试验,利用电荷耦合元件（CCD）照相机可视化技术,对流体在裂隙交叉点内的非线性流动特性进行研究。建立两种离散裂隙网络（DFN）模型,考虑两种边界条件,改变模型进口和出口之间的压力,直接求解Navier-Stokes（简称N-S）方程,对DFN的非线性渗流特性进行研究。结果表明,室内试验可以观测到与出口3相连的裂隙单元内发生了明显的非线性流动,且通过模型的流量Q和模型两端的压力P具有非线性关系。数值计算结果也表明,在水力梯度J较大时（比如J > 0.1）,通过DFN的Q和P具有非线性关系,而当J较小时（比如J < 10-4）,Q与P线性相关;根据文中的算例,建议利用局部立方定律求解DFN内每条裂隙的渗流特性的临界条件为J ≤10-4;裂隙表面粗糙会造成通过DFN渗流量的降低,但对相对流量误差的影响可忽略不计。     

An Efficient Hydrodynamic Model for Surface Waves

In the present study,a semi-implicit finite difference model for non-bydrostatic,free-surface flows is analyzed and discussed.The governing equations are the three-dimensional free-surface Reynolds-averaged Navier-Stokes equations defined on a general,irregular domain of arbitrary scale.At outflow,a combination of a sponge layer technique and a radiation boundary condition is applied to minimize wave reflection.The equations are solved with the fractional step method where the hydrostatic pressure component is determined first,while the non-hydrostatic component of the pressure is computed from the pressure Poisson equation in which the coefficient matrix is positive definite and symmetric.The advectiou and horizontal viscosity terms are discretized by use of a semi-Lagrangian approach.The resulting model is computationally efficient and unrestricted to the CFL condition.The developed model is verified against analytical solutions and experimental data,with excellent agreement.     

The application of a numerical model to coastal surface water waves

Based on the Navier-Stokes Equations (NSE), numerical simulation with fine grids is conducted to simulate the coastal surface wave changes, including wave generation, propagation, transformation and interactions between waves and structures. This numerical model has been tested for the generation of the desired incident waves, including both regular and random waves. Some numerical results of this model are compared with available experimental data. In order to apply this model to actual cases, boundary conditions are considered in detail for different shoreline types (beach or breakwater, slope or vertical wall, etc. ). Finally, the utility of the model to a real coastal area is shown by applying it to a fishing port located in Shidao, Rongcheng, Shandong Province, P.R. China.     

Simulation of Random Waves and Associated Laminar Bottom Shear Stresses

This work presents a new approach for simulating the random waves in viscous fluids and the associated bottom shear stresses. By generating the incident random waves in a numerical wave flume and solving the unsteady two-dimensional Navier-Stokes equations and the fully nonlinear free surface boundaiy conditions for the fluid flows in the flume, the viscous flows and laminar bottom shear stresses induced by random waves axe determined. The deterministic spectral amplitude method implemented by use of the fast Fourier transform algorithm was adopted to generate the incident random waves. The accuracy of the numerical scheme is confirmed by comparing the predicted wave spectrum with the target spectrum and by comparing the nanlerical transfer function between the shear stress and the surface elevation with the theoretical transfer function. The maximum bottom shear stress caused by random waves, computed by this wave model, is compared with that obtained by Myrhaug＇ s model （1995）. The transfer function method is also employed to determine the maximum shear stress, and is proved accurate.     

CHARACTER OF SIMPLIFIED NAVIER-STOKES EQUATIONS FOR NEAR THE LEADING EDGE PART OF TWO-DIMENSIONAL LAMINAR FLOW PAST A FLAT PLATE

Starting from the Simplified Navier-Stokes(SNS)equations presented at first by Godovachev-Kuzmin-Tsopov,and Gao Zhi,Davis,the authors analyze the character of the SNS equations for the laminarflow near the leading edge of a flat plate and far away from the plate by using the Weiner—Hopf meth-od and Fourier transform.It is proved that the solution of the SNS equations agree with the solution of the Navier-Stokes equations for flow near the leading edge of the plate and far away from the plate.How to match the solution of the SNS equations to the Blasius solution of the boundary layer equationsis also discussed.     

Three-Dimensional Numerical Model for Tsunami Propagation Passing Through An Obstacle

1 .Introduction In the present numerical analysis of a tsunami ,atwo-dimensional numerical model based on non-linear shallowwater theoryis mainly used (Aburaya and Imamura ,2002 ;Imamura ,1995 ; Goto andOgawa ,1992) .Thoughthis model representstsunami hei…     

Numerical simulation of irregular wave overtopping against a smooth sea dike

Based on the filtered Navier-Stokes equations and Smagorinsky turbulence model,a numerical wave flume is developed to investigate the overtopping process of irregular waves over smooth sea dikes.Simulations of fully nonlinear standing wave and regular wave’s run-up on a sea dike are carried out to validate the implementation of the numerical wave flume with wave generation and absorbing modules.To model stationary ergodic stochastic processes,several cases with different random seeds are computed for each specified irregular wave spectrum.It turns out that the statistical mean overtopping discharge shows good agreement with empirical formulas,other numerical results and experimental data.