Plotnikov–Toland板模型中水弹性孤立波的迎撞

通过奇异摄动方法研究了在薄冰层覆盖的不可压缩理想流体表面上传播的两个水弹性孤立波之间的迎面碰撞.借助特殊的Cosserat超弹性壳理论以及Kirchhoff–Love板理论,冰层由Plotnikov–Toland板模型描述.流体运动采用浅水假设和Boussinesq近似.应用Poincar′e–Lighthill–Kuo方法进行坐标变形,进而渐近求解控制方程及边界条件,给出了三阶解的显式表达.可以观察到碰撞后的孤立波不会改变它们的形状和振幅.波浪轮廓在碰撞之前是对称的,而在碰撞之后变成不对称的并且在波传播方向上向后倾斜.弹性板和流体表面张力减小了波幅.图示比较了本文与已有结果可知线性板模型可作为本文的一个特例.

气垫载荷在带裂缝冰面运动的水弹性响应

气垫船在冰面上运动会激起冰面产生水弹性波。在特定条件下,此水弹性波使得冰层内部的应力达到最大值,甚至超过冰层的极限承载应力而发生破坏。为此,该文研究了冰面裂缝对于气垫载荷引起的冰面水弹性响应的影响。基于弹性薄板假设和势流理论,建立了气垫载荷在带裂缝冰面上运动的理论数学模型。在模型求解上,采用边界元法对流体域进行求解,冰面边界条件通过有限差分法和引入虚构点满足。随后,分析了气垫载荷在不同速度运动下的冰面水弹性响应,研究了气垫载荷以不同速度运动时引起的冰面变形和应力分布,针对裂缝与气垫载荷的相对位置对气垫载荷破冰能力的影响进行了数值模拟,分析了气垫载荷引起的冰面水弹性响应变化规律。通过与气垫载荷在无限大冰面上运动的结果进行对比,结果表明,裂缝离载荷中心大于4倍载荷宽度时,载荷附近的冰面响应受裂缝的影响较小;裂缝离载荷中心的距离为1倍载荷宽度时,裂缝处会发生应力放大现象,且裂缝处的最大应力会超过气垫载荷正下方冰板的最大应力。

移动载荷作用下浮冰的非线性动力学响应

本文考虑非线性、惯性和阻尼的影响,研究了任意深度二维理想流体顶部浮冰的振动.对相关的拟微分算子进行展开并将非线性项保留至三阶后,完全非线性问题被简化为仅与自由面上的变量相关的三阶截断模型.为了验证简化模型的准确性,重点关注了自由孤立波解.在不考虑阻尼的情况下,采用多重尺度方法推导了三阶非线性薛定谔方程(NLS),利用该方程预测了任意水深下原始欧拉方程中自由波包型孤立波解的存在性及三阶截断模型的准确性.相比于Dinvay等所提出的二阶模型,三阶截断模型的优势在于其对应的三阶NLS具有准确的非线性项系数,能够在最小相速度附近更好地模拟冰层的动力学响应.进一步地对自由孤立波解进行数值计算,数值结果表明三阶截断模型在分岔曲线和孤立波波形上均与完全欧拉方程吻合良好,准确性高于二阶截断模型.基于三阶截断模型,探究了匀速局域化载荷作用下的浮冰非线性动力学响应并将时间依赖解与实验测量数据进行比较,数值计算结果与实验记录吻合良好.

Influence of water saturation on propagation of elastic waves in transversely isotropic nearly saturated soil

Biot' s two-phase theory for fluid-saturated porous media was applied in a study carried out to investigate the influence of water saturation on propagation of elastic wave in transversely isotropic nearly saturated soil. The characteristic equations for wave propagation were derived and solved analytically. The results showed that there are four waves: the first and second quasi-longitudinal waves (QP1 and QP2), the quasitransverse wave (QSV) and the anti-plane transverse wave (SH) . Numerical results are given to illustrate theinfluence of saturation on the velocity, dispersion and attenuation of the four body waves. Some typical numerical results are discussed and plotted. The results can be meaningful for soil dynamics and earthquake engineering.

Scattering of Surface Water Waves Involving Semi-infinite Floating Elastic Plates on Water of Finite Depth

Two problems of scattering of surface water waves involving a semi-infinite elastic plate and a pair of semi-infinite elastic plates,separated by a gap of finite width,floating horizontally on water of finite depth,are investigated in the present work for a two-dimensional time-harmonic case.Within the frame of linear water wave theory,the solutions of the two boundary value problems under consideration have been represented in the forms of eigenfunction expansions.Approximate values of the reflection and transmission coefficients are obtained by solving an over-determined system of linear algebraic equations in each problem.In both the problems,the method of least squares as well as the singular value decomposition have been employed and tables of numerical values of the reflection and transmission coefficients are presented for specific choices of the parameters for modelling the elastic plates.Our main aim is to check the energy balance relation in each problem which plays a very important role in the present approach of solutions of mixed boundary value problems involving Laplace equations.The main advantage of the present approach of solutions is that the results for the values of reflection and transmission coefficients obtained by using both the methods are found to satisfy the energy-balance relations associated with the respective scattering problems under consideration.The absolute values of the reflection and transmission coefficients are presented graphically against different values of the wave numbers.

Probability Analysis of the Wave-Slamming Pressure Values of the Horizontal Deck with Elastic Support

This paper presents the probability distribution of the slamming pressure from an experimental study of regular wave slamming on an elastically supported horizontal deck. The time series of the slamming pressure during the wave impact were first obtained through statistical analyses on experimental data. The exceeding probability distribution of the maximum slamming pressure peak and distribution parameters were analyzed, and the results show that the exceeding probability distribution of the maximum slamming pressure peak accords with the three-parameter Weibull distribution. Furthermore, the range and relationships of the distribution parameters were studied. The sum of the location parameter D and the scale parameter L was approximately equal to 1.0, and the exceeding probability was more than 36.79% when the random peak was equal to the sample average during the wave impact. The variation of the distribution parameters and slamming pressure under different model conditions were comprehensively presented, and the parameter values of the Weibull distribution of wave-slamming pressure peaks were different due to different test models. The parameter values were found to decrease due to the increased stiffness of the elastic support. The damage criterion of the structure model caused by the wave impact was initially discussed, and the structure model was destroyed when the average slamming time was greater than a certain value during the duration of the wave impact. The conclusions of the experimental study were then described.

Analytic approximation to nonlinear hydroelastic waves traveling in a thin elastic plate floating on a fluid

An analytic approximation method known as the homotopy analysis method(HAM)is applied to study the nonlinear hydroelastic progressive waves traveling in an infinite elastic plate such as an ice sheet or a very large floating structure(VLFS)on the surface of deep water.A convergent analytical series solution for the plate deflection is derived by choosing the optimal convergencecontrol parameter.Based on the analytical solution the efects of diferent parameters are considered.We find that the plate deflection becomes lower with an increasing Young’s modulus of the plate.The displacement tends to be flattened at the crest and be sharpened at the trough as the thickness of the plate increases,and the larger density of the plate also causes analogous results.Furthermore,it is shown that the hydroelastic response of the plate is greatly afected by the high-amplitude incident wave.The results obtained can help enrich our understanding of the nonlinear hydroelastic response of an ice sheet or a VLFS on the water surface.