二阶Boussinesq方程的孤立波解     

林建国  邱大洪 《海洋与湖沼》2001,32(3):334-339

基于同量阶迭代法，在保留同阶面的前提下，对林建国等（1998a)得到的二阶Boussinesq类方程进行了求解，得到了与其量阶相对应的取立波解，并春与Euler方程的二阶孤立波解进行了比较，结果显示，本文解比传统Boussinesq方程的孤立波解有明显的改善，扩大了孤立的适用范围。  相似文献   

Probability distribution of surface slope for nonlinear random sea waves and calculation of whitecap coverage     

Song Jinbao  Wu Kejian  Xu Delun  Sun Fu 《海洋学报(英文版)》1997,16(2):141-148

Based on the nonlinear model of two-dimensional random sea waves, a statistical distribution of wave surface slope exact to the third order is derived by using the expansion of the characteristic function and direct calculations of each order moment. Based on the distribution of wave surface slope derived in this paper, a whitecap coverage is proposed by using the limit surface slope as a criterion of wave breaking. The whitecap coverage expressed by the model depends on three parameters which can be determined in principle by the linear wave spectrum and three kinds of wave-wave interaction.  相似文献   

Analysis of single and tandem cylinder data using an orthogonal Volterra model approach     

I.A. Sibetheros  J.M. Niedzwecki   《Ocean Engineering》2005,32(2):881-156

The development of a definitive predictive model that accurately accounts for the nonlinear hydrodynamics and structural response behavior observed in arrays of closely spaced risers on deep water structures will require a more detailed understanding of this fluid–structure interaction. Through the analysis and interpretation of data from model basin tests on single and paired tandem cylinder configurations this study is directed at uncovering the nature of some aspects of this nonlinear response behavior using an orthogonal third-order Volterra technique that can delineate between linear, quadratic and cubic nonlinear frequency dependent behavior. As part of the analysis procedure the data was organized in input–output pairs that would provide logical groupings of the measured quantities. The data pairs presented in this study include wave excitation and inline cylinder displacement, wave excitation and transverse cylinder displacement, wave excitation and inline reaction force, and, upstream cylinder and downstream cylinder response. This information is presented in terms of spectral and coherence plots. The single cylinder data is presented as a means to contrast the behavior of the tandem cylinders. Both configurations were analyzed at two different pretensions adding another dimension to this investigation. It is shown that although a primary variable such as displacement may be more easily measured, pretension and force measurements provide an important key to our understanding of this difficult problem.  相似文献   

Extreme two-dimensional water waves: an assessment of potential design solutions     

S. F. Smith  C. Swan   《Ocean Engineering》2002,29(4):387-416

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A nonlinear wave profile correction of the diffraction of a wave by a long breakwater: Fixed point approach     

T.S. Jang  S.H. Kwon  Takeshi Kinoshita  B.J. Kim 《Ocean Engineering》2007,34(3-4):500-509

The authors of the present paper have suggested an iterative scheme to calculate the nonlinear wave profiles [Jang and Kwon, 2005. Application of nonlinear iteration scheme to the nonlinear water wave problem: Stokes wave. Ocean Engineering 32, 1862–1872]. The scheme was shown to be good for estimating nonlinear wave profiles. In the study, the iterative scheme is applied to the wave-diffraction problem by a long breakwater to calculate a diffracted wave by the breakwater. The iterative solution of diffraction was compared with the linear solution of Sommerfeld, 1896. [Mathematische Theoried der Diffraction. Mathematical Annals 47, 317–374]. For a small wave slope, the two solutions were in good agreement. However, the scheme enabled us to observe the nonlinear behaviors of a beating phenomenon and of wave profile such as Stokes’ wave for a relatively large wave slope: as the wave slope becomes larger, we can examine the nonlinear wave characteristics of the actual shapes of waves, i.e., the crests are steeper and the troughs are flatter.  相似文献   

浮游生态系统非线性动力学研究     

冯剑丰  李会民  王洪礼 《海洋技术学报》2007,26(3):67-69

建立了新的藻类-浮游动物生态非线性动力学模型,该模型考虑了藻类与浮游动物之间的增长关系。研究了模型平衡点的稳定性,以及Hop f分岔现象。通过对选取的分岔参数进行分析,揭示了该系统的动力学特性。  相似文献   

Nonlinear path-following control of an AUV   总被引：3，自引：0，他引：3  

Lionel Lapierre  Didik Soetanto 《Ocean Engineering》2007,34(11-12):1734-1744

A new type of control law is developed to steer an autonomous underwater vehicle (AUV) along a desired path. The methodology adopted for path-following deals explicitly with vehicle dynamics. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path-following control strategies described in the literature. Controller design builds on Lyapunov theory and backstepping techniques. The resulting nonlinear feedback control law yields convergence of the path-following error trajectory to zero. Simulation results illustrate the performance of the control system proposed.  相似文献   

上海沿岸天文潮与风暴潮非线性相互作用的数值研究   总被引：10，自引：0，他引：10  

端义宏  秦曾灏 《海洋与湖沼》1997,28(1):80-87

运用二维非线性风暴潮，天文潮和联合水位模型８次不同路径的热带气旋引起的上海地区天文潮与风暴潮的非线性相互作用进行了数值研究，讨论了天文潮气与风暴潮非线性相互作用引起的增水特征，分析了控制方程中各非线性项对天文潮与风暴晨线性相互作用引起水位变化的贡献，研究表明，考虑天文潮与风暴的非线性相互作用后，使风暴潮和水位的数值模拟结果得到了改善，非线性底摩擦在控制天文潮和风暴潮非线性相互作用中起重要的作用。而  相似文献   

Nonlinear progressive waves in water of finite depth — an analytic approximation     

Longbin Tao  Hao Song  Subrata Chakrabarti 《Coastal Engineering》2007

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   

State-dependent Riccati equation-based robust dive plane control of AUV with control constraints   总被引：1，自引：0，他引：1  

Mugdha S. Naik  Sahjendra N. Singh   《Ocean Engineering》2007,34(11-12):1711-1723

The paper treats the question of suboptimal dive plane control of autonomous underwater vehicles (AUVs) using the state-dependent Riccati equation (SDRE) technique. The SDRE method provides an effective mean of designing nonlinear control systems for minimum as well as nonminimum phase AUV models. It is assumed that the hydrodynamic parameters of the nonlinear vehicle model are imprecisely known, and in order to obtain a practical design, a hard constraint on control fin deflection is imposed. The problem of depth control is treated as a robust nonlinear output (depth) regulation problem with constant disturbance and reference exogenous signals. As such an internal model of first-order fed by the tracking error is constructed. A quadratic performance index is chosen for optimization and the algebraic Riccati equation is solved to obtain a suboptimal control law for the model with unconstrained input. For the design of model with fin angle constraints, a slack variable is introduced to transform the constrained control input problem into an unconstrained problem, and a suboptimal control law is designed for the augmented system using a modified performance index. Using the center manifold theorem, it is shown that in the closed-loop system, the system trajectories are regulated to a manifold (called output zeroing manifold) on which the depth tracking error is zero and the equilibrium state is asymptotically stable. Simulation results are presented which show that effective depth control is accomplished in spite of the uncertainties in the system parameters and control fin deflection constraints.  相似文献