Forced Oscillations in a Bounded Basin of Variable Depth

We study forced long-wave oscillations of a liquid in a ring-shaped basin of variable depth within the framework of the linear theory of long waves with regard for the influence of the Coriolis force. The oscillations are induced by disturbances of atmospheric pressure periodic as functions of time. The parameters of the basin (bottom topography and linear sizes) are chosen to approximate the Antarctic region located between 60 and 70°S. The wave velocities and the structure of the modes of elevations of the free surface are determined by using numerical methods. We also establish the dependences of the characteristics of the wave process on the period of surface pressure.     

Third-Order Stokes Wave Solutions of the Free Surface Capillary-Gravity Wave and the Interfacial Internal Wave

Based on the Stokes wave theory, the capillary-gravity wave and the interfacial internal wave in two-layer constant depth''s fluid system are investigated. The fluids are assumed to be incompressible, inviscid and irrotational. The third-order Stokes wave solutions are given by using a perturbation method. The results indicate that the third-order solutions depend on the surface tension, the density and the depth of each layer. As expected, the first-order solutions are the linear theoretical results (the small amplitude wave theoretical results). The second-order and the third-order solutions describe the nonlinear modification and the nonlinear interactions. The nonlinear impact appears not only in the n (n≥2) times'' high frequency components, but also in the low frequency components. It is also noted that the wave velocity depends on the wave number, depth, wave amplitude and surface tension.     

基于Beta波面分布的非线性海浪波高分布

基于非线性Beta波面分布,采用经验变换,导出1种仅用随机波面偏度λ3和尖度λ4 2个参数表示的非线性海浪波高概率统计分布--波高类Beta分布.此分布发展了线性窄谱假定下的Rayleigh分布.就所用实验室资料验证而言,本文推导的波高类Beta分布要优于几种工程上常用的波高分布.     

Extension of the Frequency-Domain pFFT Method for Wave Structure Interaction in Finite Depth

To analyze wave interaction with a large scale body in the frequency domain, a precorrected Fast Fourier Transform (pFFT) method has been proposed for infinite depth problems with the deep water Green function, as it can form a matrix with Toeplitz and Hankel properties. In this paper, a method is proposed to decompose the finite depth Green function into two terms, which can form matrices with the Toeplitz and a Hankel properties respectively. Then, a pFFT method for finite depth problems is developed. Based on the pFFT method, a numerical code pFFT-HOBEM is developed with the discretization of high order elements. The model is validated, and examinations on the computing efficiency and memory requirement of the new method have also been carried out. It shows that the new method has the same advantages as that for infinite depth.     

Effect of the Geometric Characteristics of a Basin on the Space Structure of Forced Oscillations

By the method of mathematical simulation, we study the effect of changes in the width and depth of a ring-shaped basin with parabolic profile of the bottom on the space structure of waves generated by variations of atmospheric pressure periodic as a function of time. Our investigation is carried out under the assumptions of the linear theory of long waves with regard for the action of the Coriolis force. The structures of the profiles of liquid surface are compared for the cases of free and forced waves. We also establish the dependences of the period of atmospheric disturbances on the geometry of the basin for which the number of nodal points of the free-surface profile in the case of forced oscillations coincides with the number of nodal points of the profile of liquid surface in the case of free oscillations.     

城市化进程对近地层大气风温结构的影响

利用北京325 m气象塔不同阶段(第一阶段:1991-1995年;第二阶段:2004-2008年)风温梯度观测,北京地区气候站长期观测(1971-2008年,20站)和城市社会经济发展指标(1978-2008年),从城市化进程不同阶段对比的角度,分析研究北京近地层大气风温结构变化特征.结果表明,北京城市化进程已经导致该地区近地层大气特征发生明显变化.主要表现为:地面和近地层温度增加,热岛强度增强;地面风速和近地层低层风速明显减小;近地层低层(63 m以下)风向变得更为紊乱;近地层温度垂直递减率增加;近地层大气风温结构特征的变化表明:2004-2008年325m气象塔,在63 m以下基本反映的是城市冠层流场特征,即气象塔周边地区城市冠层厚度约为63 m.     

Wave Disturbances of Atmospheric Pressure and Wind Speed in the Troposphere Associated with the Solar Terminator

Izvestiya, Atmospheric and Oceanic Physics - The main characteristics (coherences, phase velocities, propagation directions, characteristic periods, and amplitudes) of wave disturbances in the...     

城市化进程对近地层大气风温结构的影响

利用北京325 m气象塔不同阶段(第一阶段:1991—1995年;第二阶段:2004—2008年)风温梯度观测,北京地区气候站长期观测(1971—2008年,20站)和城市社会经济发展指标(1978—2008年),从城市化进程不同阶段对比的角度,分析研究北京近地层大气风温结构变化特征。结果表明,北京城市化进程已经导致该地区近地层大气特征发生明显变化。主要表现为:地面和近地层温度增加,热岛强度增强;地面风速和近地层低层风速明显减小;近地层低层(63 m以下)风向变得更为紊乱;近地层温度垂直递减率增加;近地层大气风温结构特征的变化表明:2004—2008年325 m气象塔,在63 m以下基本反映的是城市冠层流场特征,即气象塔周边地区城市冠层厚度约为63 m。     

Calculating Method and Verification of Wave Pressure Distribution on the Breast Wall of Mound Breakwater

In this paper, the calculating charts and formulae about wave pressure on the breast wall are derived with seven parameters on the basis of physical model study. The verification shows that the charts agree with the example, and are adopted in the Specifications of Fishery Harbours Breakwater by the Ministry of Agricultures.     

非线性效应对风浪波面极大值和极小值分布的影响

通过分析实验室风浪观测结果研究非线性效应对波面极大值和极小值分布的影响。波面极大值和极小值累积概率的差异表明 ,与线性理论相比 ,波面极小值在平均波面以下的位置偏高。对实验结果的进一步分析表明 ,非线性效应使波面极大值在平均波面以上总概率高于线性理论结果 ,而概率密度峰值处波面极大值高度略低于线性理论结果。波面极小值在平均波面以上各位置出现的概率均高于线性理论结果 ,在平均波面以下的较低位置 ,波面极小值出现概率明显低于线性理论结果。     

Wave Pressure Distribution over the Breast Wall of Mound Breakwater of Small Ports

In this paper, the mechanism of the interaction between the breast wall of mound breakwater and waves is expounded, then some new views and the law of variation of horizontal and vertical wave pressure over the breast wall are put forward. The results of this study have been adopted in the Specifications of Fishery Harbour Breakwater by the Ministry of Agricultures.     

Statistical Distribution of Surface Slope in A 3-D Ocean Wave Field

—A joint probability density function(PDF)for surface slopes in two arbitrary directions is de-rived on the basis of Longuet-Higgins's linear model for three-dimensional(3-D)random wave field.andthe correlation moments of surface slopes.as parameters in the PDF.are expressed in terms of directionalspectrum of ocean waves.So long as the directional spectrum model is given.these parameters are deter-mined.Since the directional spectrum models proposed so far are mostly parameterized by the wind speedand fetch.this allows for substituting these parameters with the wind speed and fetch.As an example.thewind speed and fetch are taken to be 14 m s and 200 km.and the Hasselmann and Donelan directionalspectra are.respectively.used to compute these parameters.Some novel results are obtained,One of the in-teresting results is that the variances of surface slope in downwind and cross-wind directions determined bythe Donelan directional spectra are close to those measured by Cox and Munk(1954).Some discussionsare m     

Experimental Study of Wave Pressure on a Breakwater Pier

Test studies on the wave pressure on a breakwater pier show that the influence of transmissivewave pressure on the outside wall of the breakwater pier is considerable,when the width of the pier is notvery large.The variations of transmissive wave pressure on the breakwater pier with different widths arecompared and the relationship is obtained between relative transmitting distance b/L and wave pressurereduction factor K,which may be used in the design of similar breakwater piers.     

变结构滑行艇斜浪航行耐波性数值分析

为改善传统滑行艇在波浪环境中耐波性问题,提出了一种兼具快速性与耐波性的变结构滑行艇,通过收放两侧片体实现滑单体形态与三体形态之间自由转换。为分析片体在斜浪航行中的减摇效果,采用数值方法对滑行艇2种形态在斜浪航行中的耐波性进行对比分析,结果表明：片体能够起到减横横摇作用,且其减横摇效果在单体形态的共振区域内最明显,在βw=60°时,片体最多能减少70.45%的横摇幅值。     

The Statistical Distribution of the Horizontal Velocities of Water Particles at Wave Surface Maxima

On the basis of the linear model of random sea waves presented by Longuet-Higgins,the statis-tical distribution of the horizontal velocities of water particles at wave surface maxima is derivedtheoretically.The derived distribution is similar to that of wave surface maxima,and a new spectral widthε_u,which is defined as(1-(m_3~2/m_2m_4))~(1/2),is introduced in the distribution.When ε_u tends to zero,the distribu-tion is reduced to Rayleigh distribution and it is reduced to the normal distribution when ε_u tends to unity.For a narrow spectrum,it is proved that ε is equal to 1/2ε,where ε is(1-(m_2~2/m_0m_4))~(1/2)and is the commonlyused spectral width..     

波面极大值处水质点水平加速度的统计分布

基于 L onguet- Higgins线性海浪模型 ,在二维情况下导出海浪波面极大值处水质点水平加速度分布律 ,其分布遵从正态分布。在分布中引入新的谱宽度参量 [(m2 m4 - m23 ) / m2 m4 ]12 。以Neumann谱为模式计算波面极大值处质点加速度分布。     

波面极大值处水质点水平速度的统计分布

基于Ｌｏｎｇｕｅｔ－Ｈｉｇｇｉｎｓ提出的线性随机海浪模型,导出了波面极大值处水质点水平速度的统计分布。分布的形式类似于波面极大值的统计分布,其中引入了一个新的谱宽度参量εｕ为１－ｍ２３ｍ２ｍ４１２。当εｕ趋于零时,导出的分布函数为瑞利分布;当εｕ趋于１时,则为正态分布。在窄谱情形下εｕ趋于１２ε,其中ε为１－ｍ２２ｍ０ｍ４１２,为常用的谱宽度参量     

Studying Specific Features of the Propagation of Atmospheric Waves Generated by Tropospheric Sources and Variations in the Surface Pressure

Izvestiya, Atmospheric and Oceanic Physics - The generation and propagation of waves from model tropospheric meteorologic heat sources are theoretically studied. The processes of gas...     

The Effect of the Solar Eclipse of March 29, 2006 on Atmospheric Pressure Fluctuations and Surface Temperature Profiles

Izvestiya, Atmospheric and Oceanic Physics - The data of measurements of atmospheric pressure fluctuations together with measurements of air temperature profiles in the surface layer of the...