共查询到20条相似文献，搜索用时 125 毫秒
1.
解四阶拟线性波动方程的一类二阶差分格式 总被引：2，自引：1，他引：2
建立了解一类四阶拟线性耗散、色散波动方程初边值问题的Crank-Nicolson差分方法，并结合外推的技巧，给出了1个线性化方法；证明了差分解的存在唯一性；用能量估计的方法证明了此格式的二阶收敛性和无条件稳定性；给出了一些数值结果。 相似文献
2.
刘新国 《中国海洋大学学报(自然科学版)》1996,(2)
本文系统地研究具二次约束最小二乘问题的敏度分析。首先给出长期方程唯一正根的上界和下界；然后证明割线法用于计算拉格朗日乘子时全局收敛；最后给出解的扰动界。 相似文献
3.
建立具有色散性的水平二维非线性波浪方程,方程的非线性近似到了三阶。方程以波面升高和自由表面速度势表达的微分-积分型数学方程,给出方程的数值求解方法和算例,对方程积分项的处理给出了计算方法。计算结果与Boussinesq方程模型和缓坡方程模型的对应计算结果进行了对比。 相似文献
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本文给出三角形单元集中质量有限元解浅水波方程的方法以及该方法在IBM-PC微机上的应用实例并取得较好结果。 相似文献
6.
给出了一些海区实测浮力频率剖面的数学模型.利用超几何函数对内波垂直模式方程进行了解析求解,得到内波模式方程的解析解和频散方程.利用得到的解析解给出了一种理想条件下内波前三阶简正模式的结构. 相似文献
7.
平稳时间序列分析在海温预报中的应用 总被引：2，自引：0，他引：2
本文根据老虎滩站１９６３－１９９４年逐年５月份海洋表层水温距平值，采用平稳时间序列分析的方法，建立的回归预报方程，从而给出时间序列未来时刻的预报值。 相似文献
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王宁 《中国海洋大学学报(自然科学版)》1996,(1)
讨论AKNS完全可积分系的一种2＋1维一般化。给出对应的Kdv方程及SineGordan方程的一种2＋1维一般化，导出其Hamilton形式。证明了经变量变换后，这类2＋1维完全可积分系可化为1＋1维已知可积分系。 相似文献
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指出ｖｏｎ Ｂｅｒｔａｌａｎｆｆｙ生长公式的局限性在于公式导出时所用假设“鱼的体重增加量同体重的２／３次方成比例，减少量同体重成比例”的根据不充分；其不足之处在于解方程时将变量ｌ误为鱼的体长。本文作了更为一般的假设，即鱼的体重增加量同体重的ｐ次方成比例；减少量同体重的ｑ次方成比例。进而通过严格的数学推导，得出鱼的更为一般的生长方程ｗ＝ｗ∞［１－ｅ＾－ｋ（ｔ－ｔ０）］＾ｒ，使ｖｏｎ Ｂｅｒｔａｌａｎ 相似文献
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The third order triple-frequency wave load on fixed axisymmetric bodies by monochromatic waves is considered within the frame of potential theory. Waves are assumed to be weak non-linearity and a perturbation method is used to expand velocity potentials and wave loadings into series according to a wave steepness of kA. Integral equation method is used to compute velocity potentials up to second order in wave steepness. The third order triple-frequency wave loads are computed by an indirect method and an efficient method is applied to form the third order forcing term on the free surface quickly. The method can be used to compute third order triple-frequency surge force, heave force and pitch moment on any revolution bodies with vertical axes. The comparison with Malenica and Molin's results is made on surge force on a uniform cylinder, and comparison with experimental results is made on third order surge force, heave force and pitch moment on a truncated cylinder. More numerical computations are carried out for third order forces and moments on a uniform cylinder, truncated cylinders and a hemisphere. 相似文献
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应用非线性谱分析理论，对三阶Stokes型随机波浪载荷谱进行了分析，将波面方程及海水质点的水平速度用一阶波面的非线性组表示，导出了随机波浪谱的表达式。为了便于求解随机波浪的载荷谱，将阻力项展开为幂级数式，并应用非线性谱分析理论，确定了幂级数的系数，进而将波浪载荷表示为一阶波面及其导数的非线性组合，最后得出波浪载荷谱密度的表达式，并应用数值分析方法，得出单位桩柱波浪力及总波浪力谱密度。 相似文献
14.
Higher order Boussinesq equations 总被引：2，自引：0，他引：2
Z. L. Zou 《Ocean Engineering》1999,26(8):239
A new form of Boussinesq-type equations accurate to the third order are derived in this paper to improve the linear dispersion and nonlinearity characteristics in deeper water. Fourth spatial derivatives in the third order terms of the equations are transformed into second derivatives and present no difficulty in numerical computations. With the increase in accuracy of the equations, the nonlinear and dispersion characteristics of the equations are of one order of magnitude higher accuracy than those of the classical Boussinesq equations. The equations can serve as a fully nonlinear model for shallow water waves. The shoaling property of the equations is also of high accuracy through shallow water to deep water by introducing an extra source term into the second order continuity equation. An approach to increase the accuracy of the nonlinear characteristics of the new equations is introduced. The expression for the vertical distribution of the horizontal velocities is a fourth order polynomial. 相似文献
15.
This paper presents a potential based boundary element method for solving a nonlinear free surface flow problem for a ship moving with a uniform speed in finite depth of water. The free surface boundary condition is linearized by the systematic method of perturbation in terms of a small parameter up to third order. The surfaces are discretized into flat quadrilateral elements and the influence coefficients are calculated by Morino's analytical formula. Dawson's upstream finite difference operator is used in order to satisfy the radiation condition. The second order solution gives better result than the first or third order solution. So the present method with the second order solution can be adopted as a powerful tool for the hydrodynamic analysis of the thin ship in finite depth of water. 相似文献
16.
北麂列岛岩相潮间带底栖生物群落的组成特征 总被引：15，自引：0，他引：15
本文报导了1997.7-1998.4期间北麂列岛岩相潮间带底栖生物群落的组成特征.研究结果表明:总平均生物量和栖息密度分别为5091.80g·m-2和4269个·m-2; 生物量和栖息密度的水平分布为关帝山＞大筲箕屿＞海利＞壳菜岙,垂直分布为中潮区＞低潮区＞高潮区,生物量和栖息密度的季节变化分别为冬季＞春季＞秋季＞夏季和冬季＞秋季＞春季＞夏季.数量的水平分布主要受海岸开敞度及浪击度的影响、垂直分布主要受潮区及浪击度的影响、季节变化主要受温度和动植物繁殖的影响. 相似文献
17.
Filipa Simes Brito Ferreira Oliveira 《Ocean Engineering》2004,31(11-12):1567-1576
The performance of open boundaries in a finite differences scheme of the elliptic mild-slope equation is assessed. The wave propagation results show that lowest order parabolic radiation boundary conditions, unlike sponge layers combined with first order radiation boundary conditions, are an efficient alternative to first order radiation boundary conditions in order to improve the accuracy of the numerical solution of the problem. 相似文献
18.
Two methods are presented for analysis of second order waves in a wave tank. The first method is by placing three wave probes in a line parallel to the line of propagation of long-crested irregular waves. By correlation analysis the spectra of set-down, parasitic waves and reflected waves of the second order are separated. The second method is to apply the square-law operation as proposed by Bendat and Piersol, to the spectral analysis of this particular non-linear system. The results of the two methods seem to agree reasonably well. A practical application of the present analysis is to analyse low frequency responses of a moored structure in a wave tank, where it is recognized that simulation of second order waves and the structure's responses are often accompanied by parasitic second order waves and reflected waves in the tank. These adulterations may be regarded as noises, and the proper information regarding non-linear second order responses extracted from the raw output. 相似文献
19.
Features observed in horizontal wavenumber spectra from low-frequency acoustic measurements taken off the New Jersey Shelf are analyzed through forward modeling using PE models. Environmental models which produce very good agreement with relative intensity data may only match wavenumbers of lower order modes. A prominent feature in contours of modal amplitude versus horizontal wavenumber and depth is the presence of double images of some higher order modes. Two possible causes of this phenomenon are examined. Range dependence in the environment can produce multiple modal images, but the magnitudes of variations required are much larger than those expected at the experiment site. The more likely cause of the double modes is shown to be a duct deep (two acoustic wavelengths) within the sediment. It produces modes with wavenumbers that are close together and with shapes that are very similar in the water column. Comparisons of model predictions with 50-Hz experimental wavenumbers and mode shapes show good agreement, except for amplitudes of some higher order modes. Predictions at 75 Hz typically require more detailed information about the sediment structure in order to accurately match all the features of higher order modes in the data 相似文献
20.
任意水深变化Boussinesq型方程非线性波数值计算 总被引：6，自引：2，他引：4
首先从一个含有耗散项的高阶非线性和频散性波浪理论模型出发,建立了适用于任意底坡变化,相对水深h／Lo≤1的非线性波数学模型。应用全隐式交错网格和二阶精度中心差分法。得到离散方程组。进一步对其一阶导数项进行修正,达到与方程高阶项同量阶精度。精度检验表明本文计算结果与理论解和物理模型结果符合良好。 相似文献