共查询到20条相似文献,搜索用时 15 毫秒
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Okey Nwogu 《Applied Ocean Research》1989,11(4):176-182
A procedure for estimating directional wave spectra from an array of wave probes based on the Maximum Entropy Method (MEM) is developed in the present paper. The MEM approach yields an angular spreading function at each frequency band consistent with the input cross-spectral density matrix. The method is evaluated using numerical simulations of directional sea states. The MEM is also used to analyze data obtained from the three-dimensional wave basin of the Hydraulics Laboratory, National Research Council of Canada. Finally, the MEM is compared with the Maximum Likelihood Method (MLM) and is shown to be a powerful tool for directional wave analysis. 相似文献
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浪向代表着海浪传播方向,它是海上交通安全以及海岸资源管理的重要海洋环境参数之一。本文针对X波段测波雷达对海杂波的连续成像,提出了一种基于光流法的海浪传播方向反演新方法。该方法利用X波段测波雷达接收的海面回波图像序列直接进行光流运动估计,将得到的每个像素点的运动矢量进行加权平均,最后得到实际的海浪传播方向。与传统基于频域的X波段测波雷达浪向反演方法相比,本文提出的方法直接从时域来进行回波信号处理,无需提前得到调制传递函数以及精确的海流,减少了由于海流估算的不准确以及调制传递函数选取的误差而给雷达浪向反演带来的影响。同时,该方法简单高效,占用资源少,将其应用至仿真雷达回波以及现场实测数据来进行浪向反演,反演得到的浪向与仿真设定浪向值以及浮标实时观测浪向结果都有很好的吻合度,变化趋势也完全一致,进而验证了该方法的有效性以及准确性。 相似文献
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船用X波段雷达被广泛应用于海洋表面波观测和研究。本文给出了一种新的从船用X波段雷达图像中确定主波传播方向的方法。X波段雷达图像中的海浪信号具有明显的尺度性和方向性。同时,curvelet变换作为一种同时具备尺度分辨率和方向分辨率的数学变换,能够对一幅雷达图像在不同尺度、不同方向和不同位置上进行分析。对一幅雷达图像进行curvelet分解并获得curvelet系数后,波浪信号主要集中在某些特定尺度和方向的curvelet系数中,从而我们可以获得带有 方向模糊的波传播方向。进而,通过计算几幅连续采集图像的互相关系数可以消除 方向模糊。同步观测的雷达图像和浮标数据证明了该方法的有效性。 相似文献
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Li Yucheng 《海洋学报(英文版)》1996,15(2):261-272
Thewavetransformationandbreakingphenomenainshallowwater¥LiYucheng(1.DalianUniversityofTechnology,Dalian116023,China)Abstract:... 相似文献
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When studying the harbor water tranquility, cases are often confronted as that the verification point is not located on the generation line or that the angle between the generation line and the isobath is so large that the differences of the wave climates along the generation line can not be ignored. For these cases, the incident boundary conditions are difficult to evaluate. In order to solve this problem, a combined wave model is developed in the present paper based on the Boussinesq equation and the wave action balance equation. Instead of the one-line wave generation method, a multi-line generation method is proposed for the combined model. Application of this method is given to a case that the harbor is designed with two entrances and the angle between the generation line and the isobath is large and the results are shown reasonable. We suggest that the wave generation method on multi-lines might also be introduced to the wave physical model as the replacement for the one-line generation method. 相似文献
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In most design applications such as alignment of the berthing structure and breakwater alignment, it becomes necessary to determine the direction of design wave. There are two different approaches to determine wave direction. One involves the use of first order Fourier coefficients (mean wave direction) while the other uses second order Fourier coefficients (principal wave direction). Both the average wave direction over the entire frequency range (0.03–0.58 Hz) and the direction corresponding to the peak frequency are used in practice. In the present study, comparison is made on wave directions estimated based on first and second order Fourier coefficients using data collected at four locations in the west and east coasts of India. Study shows that at all locations, the mean and principal wave directions for frequencies ranging from 0.07 to 0.25 Hz (±0.5 times peak frequency) co-vary with a correlation coefficient of 0.99 but at lower and higher frequencies, difference between the parameters is large. Average difference between the mean wave direction at peak frequency and the average over the frequency related to spectral energy more than 20% of maximum value is less, around 13°. Study shows that average difference in the sea and swell directions is around 39°. 相似文献
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航道对多方向波传播影响 总被引:2,自引:0,他引:2
应用Boussinesq方程对不同入射角、不同方向集中度的波浪与航道的相互作用进行模拟,得到了航道的折射影响规律以及不同入射角、不同方向集中度的波浪对航道作用的差别.结果对试验研究及工程实践有指导意义. 相似文献
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基于B—样条的边界元方法及其在波浪力计算中的应用 总被引:2,自引:2,他引:2
就波浪与结构物相互作用问题,应用B-样条函数对物体表面上的速度势进行了数值离散,物体表面的控制参数通过最小二乘原理确定,速度势控制参数通过Galerkin理论确定。本理论给 其导数在整个光滑物面上都是连续的。采用此种方法所计算的数值解十分准确,并且收敛得很快。 相似文献
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We show how to calculate the encountered wave period distribution for a ship traveling with constant speed on a Gaussian random sea with a directionally distributed frequency spectrum. 相似文献
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波浪非线性弥散关系及其应用 总被引:3,自引:0,他引:3
针对Hedges及Kirby等对Kirby和Dahymple的非线性弥散关系的修正关系,在小波陡时中等水深范围存在较大偏差的问题,给出了一个新的非线性弥散关系。比较可知,新的关系在小波陡时减小了中等水深范围内50%的误差,而在大波陡时能够保持其单调性,且形式上更为简练。将其应用于含弱非线性效应的缓坡方程进行数值验证,结果表明,采用新的非线性弥散关系得到的计算结果与实测结果更为吻合。 相似文献
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This paper proposes the retrieval method of ocean wave spectrum for airborne radar observations at small incidence angles, which is slightly modified from the method developed by Hauser. Firstly, it makes use of integration method to estimate total mean square slope instead of fitting method, which aims to reduce the affects of fluctuations superposed on normalized radar cross-section by integration. Secondly, for eliminating the noise spectrum contained in signal spectrum, the method considers the signal spectrum in certain look direction without any long wave components as the assumed noise spectrum, which would be subtracted from signal spectrum in any look direction for linear wave spectrum retrieval. Estimated ν from the integration method are lower than the one from fitting method and have a standard deviation of 0.004 between them approximately. The assumed noise spectrum energy almost has no big variations along with the wave number and is slightly lower to the high wave number part of signal spectrum in any look direction, which follows that the assumption makes sense. The retrieved directional spectra are compared with the buoy records in terms of peak wavelength, peak direction and the significant wave height. Comparisons show that the retrieved peak wavelength and significant wave height are slightly higher than the buoy records but don’t differs significantly (error less than 10%). For peak direction, the swell waves in first case basically propagate in the wind direction 6 hours ago and the wind-generated waves in second case also propagate in the wind direction, but the 180? ambiguity remains. Results show that the modified method can carry out the retrieval of directional wave spectrum. 相似文献
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三维随机海浪的数值模拟 总被引:1,自引:0,他引:1
本文首先分析了三维随机海浪的方向谱函数和三维随机海浪的数学模型,然后在MATLAB环境下设计了数值模拟程序,并模拟出三维随机海浪的方向谱和三维随机海浪的三维空间模型。 相似文献
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改进了方向波谱的分析方法及噪声谱经验公式,使本法随测波环境及仪器特性自动修正经验参值,更易于实际应用。基于Maximum heave/pitch quad-spectrum method,由时域及频率域上的浮标动力反应数值计算,推求反应增益因子及相位延迟项,并进一步将其导入方向波谱计算,使其能修正资料浮标对波浪之轴不对称动态反应所造成的相位延迟不一致及主波向误差。经数值仿真验证,该方法的确能消减因资料浮标对波浪之轴不对称动态反应所造成的相位延迟及对主波向估算所造成之影响。应用花莲现场观测资料验证改良之主波向估算方法,得出是否考虑波浪运动与浮标运动间之振幅响应因子及相位延迟因子,所得之主波向的差异介于0-12℃之间。 相似文献
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海洋波浪能平均功率的准确计算是波浪能开发和利用的基础。实践中,波浪能转换装置一般安装在有限水深区域。对于随机波,只有当详尽的波浪谱已知的时候,有限水深区的波能功率才能被准确计算出来。由于种种原因,实践中波浪的实测数据大多以散点图或有义波高和统计波周期的形式给出,而波浪谱信息有时则很难获得。基于这种情况,传统上人们利用无限水深条件下的相关公式来估算有限水深区域的波能功率,但这种做法会造成较大的误差。本研究显示,对于50 m水深的理论波谱JONSWAP谱来说该误差高达14.6%。为了提高波能功率计算的准确性,本文提出了一种基于能量频率的一阶和二阶近似算法,可以在未知波浪谱的情况下较为准确地计算不同水深时的波能功率。针对两种理论波浪谱的计算结果表明,本方法在计算有限带宽内的波能功率时计算误差低于2.8%。 相似文献
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通过数模波浪和物模实验,比较分析了估算多向不规则入射波与反射波相互叠加的锁相波浪场方向分布和反射系数方向分布的改进的贝叶斯估计法MBDM和扩展的最大似然法MMLM的性能。数模试验检验了不同波浪条件、不同波浪测量系统和结构物的不同反射特性等情况下的估算结果,同时还比较了两种分析方法的计算速度和稳定性,结果显示,对于波浪的方向分布估计,MBDM优于MMLM,对于反射系数的方向分布估计以及计算速度和稳定性,MMLM优于MBDM。 相似文献
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