中等长高比腔体内的局部行进波对流

本文通过二维流体力学基本方程的数值摸拟，讨论了具有较弱的Soret结合的中等长高比空腔中的Counter propagating wave，局部行进波及定常行进波的动力特性，探讨了局部行进波的Rayleigh数依赖性及稳定性。     

水平流作用下的混合流体行进波对流

利用高阶紧致有限差分格式,数值模拟研究了物性参数对具有Soret效应的混合流体的Poiseuille-Rayleigh-Bénard流动系统的影响。在正的小分离比下,附加一个微小的温度扰动作为扰动源,流动系统时空结构的发展在经历了初始状态、线性波指数型成长和非线性发展三个阶段之后,最终演变成为稳定的周期性行进波状态。还进一步探讨了水平流强度和Rayleigh数对流场结构的影响。     

THE EXTENDED JACOBIAN ELLIPTIC FUNCTION EXPANSION METHOD AND ITS APPLICATIONS IN WEAKLY NONLINEAR WAVE EQUATIONS

1. INTRODUCTION In the study of nonlinear fluid models, it is very important to find exact solutions and especially physical significant soliton solutions. In the past decades, variety of methods are developed to solve Nonlinear Partial Differential Equat…     

双局部行进波对流的时空结构

本文通过二维流体力学基本方程的数值模拟，探讨了均匀行进波状态时的阴影强度分布特性。两个Rayleigh数的局部行进波形成过程的计算比较说明局部行进波的稳定性依赖于Rayleigh数的大小。在稳定区间内局部行进波的宽度随Rayleigh数的增加而增加。最后对一个时间周期上行进波场进行平均后说明，场的平均值可以很好的表征双局部行进波特性。     

Wave runup simulations using Lagrangian blocks on Eulerian mesh

The runup of breaking and non-breaking solitary waves on a plane beach has been simulated using the shallow-water equations and a Lagrangian blocks on Eulerian mesh (LBEM) method. The results obtained for the entire range of wave steepness are compared with the experimental data, the nonlinear theory, and the finite-difference method. The LBEM simulation agrees with the nonlinear theory when the amplitude of the wave is small. On the whole, it produces a better result in agreement with the experimental data when friction is included in the simulation. The simulation also produced better result than the finite-difference simulation.     

拱坝随机地震行波效应分析

将随机振动的虚拟激励法与拱坝地基动力相互作用FE-BE-IBE时域模型结合,发展了一个可以考虑随机地震动行波效应的拱坝随机动力响应计算模型,并用Monte-Carlo法对模型进行了验证.不同行波波速的计算结果表明,行波效应可以影响拱坝的动力响应,幅度在10%~20%,较小的行波波速在坝体边界产生应力集中现象,表明行波效应对拱坝动力响应具有显著影响.     

NUMERICAL SIMULATIONS OF NONLINEAR WAVE TRANSFORMATION AROUND WAVE-PERMEABLE STRUCTURE

1.INTRODUCTION Thedevelopmentofbreakwaterdesignmeth odologyoftenrequireaconditionofpermittingfor protectionofecosystem,itisalsoanalternativeto massivegravitybreakwatersinreductionofwave transmissioninshallowwater.Thetheoreticalso lutionsofwavepermeablebreakwatersdiversified indifferentexpressionsoftheenergydamping term,duetolaminarandturbulentflowintheper meablestructures.Theporositysolution[1]isbased onatrialmethod,andanumberofauthorssolve theproblembydifferentnumericalapproach[27].Inpre…     

周期性加热Poiseuille-Rayleigh-Benard流动中局部行波的研究

该文通过二维流体力学基本方程组的数值模拟,研究了水平来流和周期性加热对腔体内流体的运动和动力学特性的影响。当相对瑞利数r(28)9时,随着水平来流雷诺数Re逐渐增加,腔体内的流体发生三种不同的运动,即局部对流运动、局部行波运动和水平流运动。对局部行波运动的周期pT进行研究,局部行波运动的稳定周期随水平来流雷诺数的增大而减小,随相对瑞利数的减小而减小;相对瑞利数越小,稳定周期随水平来流雷诺数变化的增长率越大。局部行波运动的区间(35)Re依赖水平来流雷诺数的强度,当水平来流雷诺数Re大于(35)Re的上限时流体为水平流运动,而当水平来流雷诺数Re小于(35)Re的下限时流体为局部对流运动;对于不同的相对瑞利数r,局部行波运动的区间(35)Re是不同的。随着水平来流雷诺数增大,发现腔体内上游行波区域对流圈的减少速度比下游行波区域更快。     

孤立波与潜水台阶相互作用的数值研究

本文用完整二维Navier-Stokes方程和VOF方法研究孤立波与潜水台阶障碍物相互作用问题.本文的计算结果与Seabra-Santos,Penouard and Temperville(1987)的实验结果有较好的一致性,与Germain(1984)基于势流浅水理论的结果较为接近,同时能更好模拟出前传演化波的衰减.只要给出初始孤立波波幅,静水深和潜水台阶障碍物的高度,利用本文方法就能模拟出演化波、分裂波和反射波的波形,并给出每一时刻的自由面形状、流场、涡量和压力的分布.     

浅水波与圆弧型贯底式防波堤的相互作用

该文基于椭圆余弦波绕射理论,应用特征函数展开法,推导了浅水波对圆弧型贯底式多孔介质防波堤绕射的波势解,并据此解析计算了作用于防波堤的水平波浪载荷与浅水波波面分布。计算结果表明:浅水波入射角与非线性影响参数、海况条件以及防波堤几何条件等因素的相对变化对波浪作用均存在一定的影响,结构透空可以明显减弱防波堤所受波浪作用。与微幅波理论对比可知:在一定浅水条件下采用椭圆余弦波一阶分量模型所计算的最大无量纲波浪力、力矩和波面分布值均明显高于微幅波理论的对应估值,反映了水波非线性因素的影响效应。     

Numerical analysis of seabed dynamic response in vicinity of mono-pile under wave-current loading

Pile foundations have been widely used in offshore engineering.In this study,a three-dimensional numerical model was used to investigate the seabed response around a mono-pile under wave-current loading.Reynolds-averaged Navier-Stokes equations were used to simulate the flow field,and Biot's consolidation equations were used for simulating the response of a porous seabed.The pore water pressure within soil and the effective stress along the depth of the seabed were simulated for various current velocities,with currents traveling either along or against the wave.Results indicate that the current has a significant effect on the effective stress and the pore water pressure distributions,which increases with the current velocity,and that the current traveling against the wave increases the liquefaction depth of the porous seabed.     

Characteristics of wave amplitude and currents in South China Sea induced by a virtual extreme tsunami

This paper investigates the potential extreme tsunami hazards of the worst case scenario of the magnitude M_w=9.30 in South China Sea(SCS)as the Manila Trench is becoming one of the most hazardous tsunami source regions.Using nonlinear shallow water equations model,the time series of surface elevation,arrival time,spatial distributions of maximum wave amplitude and velocity distribution are presented.The characteristics of wave and currents are analyzed.The numerical results indicate that most of the energy of tsunami wave distributes in central and north part of SCS.The offshore regions around SCS will be influenced significantly by the tsunami currents generated by an earthquake in the Manila subduction zone.The maximum wave amplitude near Guangdong Province,Hainan Island,and Taiwan Island exceeds 4 m and velocities at the majority of measured locations near coast exceeds 2 m/s.Nested grid with high resolution is used to study the impacts of the tsunami on Hainan Island,Taiwan Island,and Lingding Bay.The regions with high hazard risk due to strong currents are identified.Finally,a fast tsunami warning method in SCS is developed and discussed,which can provide tsunami warning information in 5 min.     

散体滑坡涌浪形成与传播的物理模拟试验研究

滑坡入水淹没率是影响滑坡涌浪生成和传播的重要因素。采用正交试验开展散体滑坡涌浪室内模拟试验研究,探讨了滑体规模、速度与水深条件对涌浪波形特征的影响。取得如下研究成果:①滑体完全入水激发涌浪,首浪具有较大波幅,波前平缓、波后较陡,且波形关于竖直和水平轴对称,呈“匍匐”态传播;未完全入水滑坡涌浪初始波峰明显,形态尖突,无明显波谷,波形关于竖直轴对称。②建立了基于单宽体积比R和弗劳德数Fr的波形分类方法,将涌浪分为类斯托克斯波、类椭圆余弦波(或类孤立波)和涌波3种波形,界定了基于R-Fr关系的波形边界方程。③构建了基于R参数的最大波幅预测模型,选取4个涌浪案例验证了模型的可靠性。研究结果对探究深水与浅水区滑坡涌浪的预测具有参考意义。     

Nonlinear dynamic characteristics of a multi-module floating airport with rigid-flexible connections

This paper studies the dynamics of a multi-module floating airport with flexible connectors using the network theory. A mathematical model for a chain-type topology structure is developed by using the wave theory, and the models of a single floating module and the connector and mooring system. The nonlinear dynamics of the floating airport and the connector force are studied. A remarkable phenomenon of amplitude death is observed, as a weak oscillation state of all floating modules, an important state for the system global dynamic stability. The parametric domain for the onset of amplitude death is identified, and the effects of the wave height and the number of the floating modules on the dynamic stability are discussed. An application of the network theory in the marine engineering is illustrated with the introduction of a new concept for global dynamic stability for the floating airport.     

底部加热的两板间水平流动进口段流动特性分析

采用二维流体力学基本方程组对普朗特数Pr=0.72的具有水平流动的底部加热两板之间的流动特性进行数值模拟。结果表明,对于给定相对瑞利数r,随着雷诺数Re的增加,底部加热的两板之间依次出现定常对流滚动,均匀行波对流滚动,具有水平流动进口段的局部行波对流滚动及水平流动。对于相对瑞利数r=3,在雷诺数9.0＜Re＜21.0范围内,系统是局部行波对流滚动,存在水平流动进口段。随着雷诺数增加,水平流动进口段长度增加。对于雷诺数Re=25.0,在相对瑞利数4＜r＜12范围内,两板之间是局部行波对流滚动,出现水平流动进口段。随着相对瑞利数增加,水平流动进口段长度减小。最后给出了进口段长度随雷诺数或相对瑞利数变化的经验式。     

开阔海域越洋海啸波高计算的一种简化方法

该文研究了开阔海域中越洋海啸波高的简化计算方法。基于选取具有一系列断裂带长宽比的震源参数,采用Okada弹性变形理论生成初始海底变形,运用基于有限体积法的非线性浅水方程数值模型,模拟地震激发海啸在4 000 m水深的平底地形上的传播过程。通过监测布置在相对震源中心不同距离及方位角上测点的波面时间序列,研究海啸波高在不同距离及方位角上的分布规律,给出不同断裂带长宽比下越洋海啸传播过程中首波幅值的分布关系式;进一步分析了断裂带长宽比对模型参数的影响,得出了归一化的越洋海啸波高计算经验公式,并与日本2011年海啸实际记录进行对比,验证了该近似方法的有效性。     

NUMERICAL STUDIES OF INTERNAL SOLITARY WAVE GENERATION AND EVOLUTION BY GRAVITY COLLAPSE

In this study, an analysis on the internal wave generation via the gravity collapse mechanism is carried out based on thetheoretical formulation and the numerical simulation. With the linear theoretical model, a rectangle shape wave is generated andpropagates back and forth in the domain, while a two-dimensional non-hydrostatic numerical model could reproduce all the observedphenomena in the laboratory experiments conducted by Chen et al. (2007), and the related process realistically. The model resultsfurther provide more quantitative information in the whole domain, thus allowing an in depth understanding of the correspondinginternal solitary wave generation and propagation. It is shown that the initial type of the internal wave is determined by the relativeheight between the perturbation and the environmental density interface, while the final wave type is related to the relative height ofthe upper and lower layers of the environmental fluid. The shape of the internal wave generated is consistent with that predicted bythe KdV and EKdV theories if its amplitude is small, as the amplitude becomes larger, the performance of the EKdV becomes betterafter the wave adjusts itself to the ambient stratification and reaches an equilibrium state between the nonlinear and dispersion effects.The evolution of the mechanical energy is also analyzed.     

NUMERICAL SIMULATIONS OF NONLINEAR WAVES OVERTOPPING AN OBSTRUCTION

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非一致地震动输入下高面板坝地震反应特性

为研究地震波非一致输入对三维高面板坝动力反应的影响,采用波场分离的思路将人工动力边界处的总波场分解为无局部场地效应影响的自由场和局部场地效应引起的散射场,借助黏弹性边界建立地震波在自由场作用下地震动非一致输入,实现考虑地基辐射阻尼和地震波行波效应的地震动输入。对我国西南地区某高面板坝进行非一致地震动反应分析,研究P波和SV波作用下坝体结构的动力反应规律。结果表明:当P波非一致输入时,随着入射角度的增加,竖向加速度和动位移极值逐渐减小,水平向加速度和动位移极值逐渐增大;SV波非一致输入时,地震动反应规律与P波入射时相反。入射角度对地震波的行波效应以及坝顶加速度反应谱幅值等都有较显著的影响。     

Numerical solutions for two nonlinear wave equations

The split-step pseudo-spectral method is a useful method for solving nonlinear wave equations. However, it is not widely used because of the limitation of the periodic boundary condition. In this paper, the method is modified at its second step by avoiding transforming the wave height function into a frequency domain function. Thus, the periodic boundary condition is not required, and the new method is easy to implement. In order to validate its performance, the proposed method was used to solve the nonlinear parabolic mild-slope equation and the spatial modified nonlinear Schr dinger (MNLS) equation, which were used to model the wave propagation under different bathymetric conditions. Good agreement between the numerical and experimental results shows that the present method is effective and efficient in solving nonlinear wave equations.