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1.
This paper presents a study on the motion response of a tension-leg platform (TLP) under first- and second-order wave forces, including the mean-drift force, difference and sum-frequency forces. The second-order wave force is calculated using the full-field quadratic transfer function (QTF). The coupled effect of the horizontal motions, such as surge, sway and yaw motions, and the set-down motion are taken into consideration by the nonlinear restoring matrix. The time-domain analysis with 50-yr random sea state is performed. A comparison of the results of different case studies is made to assess the influence of second-order wave force on the motions of the platform. The analysis shows that the second-order wave force has a major impact on motions of the TLP. The second-order difference-frequency wave force has an obvious influence on the low-frequency motions of surge and sway, and also will induce a large set-down motion which is an important part of heave motion. Besides, the second-order sum-frequency force will induce a set of high-frequency motions of roll and pitch. However, little influence of second-order wave force is found on the yaw motion. 相似文献
2.
Because of the intrinsic difficulty in determining distributions for wave periods, previous studies on wave period distribution
models have not taken nonlinearity into account and have not performed well in terms of describing and statistically analyzing
the probability density distribution of ocean waves. In this study, a statistical model of random waves is developed using
Stokes wave theory of water wave dynamics. In addition, a new nonlinear probability distribution function for the wave period
is presented with the parameters of spectral density width and nonlinear wave steepness, which is more reasonable as a physical
mechanism. The magnitude of wave steepness determines the intensity of the nonlinear effect, while the spectral width only
changes the energy distribution. The wave steepness is found to be an important parameter in terms of not only dynamics but
also statistics. The value of wave steepness reflects the degree that the wave period distribution skews from the Cauchy distribution,
and it also describes the variation in the distribution function, which resembles that of the wave surface elevation distribution
and wave height distribution. We found that the distribution curves skew leftward and upward as the wave steepness increases.
The wave period observations for the SZFII-1 buoy, made off the coast of Weihai (37°27.6′ N, 122°15.1′ E), China, are used
to verify the new distribution. The coefficient of the correlation between the new distribution and the buoy data at different
spectral widths (ν=0.3−0.5) is within the range of 0.968 6 to 0.991 7. In addition, the Longuet-Higgins (1975) and Sun (1988)
distributions and the new distribution presented in this work are compared. The validations and comparisons indicate that
the new nonlinear probability density distribution fits the buoy measurements better than the Longuet-Higgins and Sun distributions
do. We believe that adoption of the new wave period distribution would improve traditional statistical wave theory. 相似文献
3.
Linear wave theory and Longuet-Higgins and Steward's (1964) group-induced second-order longweve (GSLW) theory ware used in this study on the grouping effect on wave forces acting on a verticalbreakwater. The calculated variance of total wave pressure on the vertical breakwater was closer tothe measured value if the wave grouping effect was considered. 相似文献
4.
A new model is proposed to estimate the significant wave heights with ERS-1/2 scatterometer data. The results show that the relationship between wave parameters and radar backscattering cross section is similar to that between wind and the radar backscattering cross section. Therefore, the relationship between significant wave height and the radar backscattering cross section is established with a neural network algorithm, which is, if the average wave period is ≤7s, the root mean square of significant wave... 相似文献
5.
结合智能天线波束形成的特性,提出了将恒模算法运用到波束形成中的新方案.利用恒模算法来训练加权因子以获得理想的信号增益.仿真实验验证了该方案的合理性. 相似文献
6.
通过对粤东后江湾近岸带垂岸方向上4个测站,同步观测到的波浪数据进行频域统计分析,初步探讨分析了波浪近岸传播过程中波浪统计性质的变化规律。结果表明:碎波带内波的频谱多峰特征显著,峰频两侧均存在着显著能量峰值,峰频能量发生转移;波浪经过破碎后,约束长波能量被释放出来;波浪向岸过程中谱宽度(ε)变大,同时谱尖度(Qp)减小,显著波陡(Ss)增大,峰值周期(Tp)增大,平均周期(Tm02)减小。 相似文献
7.
通过研究分析传统的应用于CDMA系统的自适应波束形成带给系统的复杂度,采用先把接收信号与本地扩频码相乘解扩后再进行基于扩频码滤波的波束形成技术,并基于最大化信干噪比准则,提出一种计算复杂度小、在不同通信环境下性能良好的综合方案.仿真结果证实了算法的有效性. 相似文献
8.
李志强 《广东海洋大学学报》2012,(4):63-66
波浪经破碎、折射、绕射等过程后进入到碎波带,波面已经不再满足经典波浪理论的正态分布假设.利用R/S分析方法对碎波带波面的进行分析,揭示碎波带波面具有标度不变性特征,波面序列具有“记忆性”和持久性,其Hurst指数为0.76,这对建立和解释碎波带波面及波高概率分布有指示意义.进一步分析后指出Hurst指数H和谱尖度参量Qp 及波群参数Ka 呈显著的负相关,Hurst指数有可能作为反映碎波带状态的一个参数. 相似文献
9.
以CCMP（Cross—Calibrated,Multi—Platfoml）风场为驱动场,分别驱动目前国际先进的第3代海浪模式ww3（WAVEWATCH—III）、SWAN（Simulating WAves Nearshore）,对2010年9月发生在东中国海的台风“圆规”所致的台风浪进行数值模拟,就台风浪的特征进行分析,并对比分析两个海浪模式的模拟效果。结果表明：1）以CCMP风场分别驱动WW3、SWAN海浪模式,可以较好地模拟发生在东中国海的台风浪,风向与波向保持了大体一致,波高与风速的分布特征保持了很好的一致性;2）综合相关系数、偏差、均方根误差、平均绝对误差来看,两个模式模拟的有效波高（SWH—Significant Wdve Height）都具有较高精度,SWAN模拟的SWH略低于观测值,WW3模拟的SWH与观测值更为接近;3）台风浪可给琉球群岛海域带来5m左右的大浪,台风浪进入东海后,波高、风速都有一定程度的增加,当台风沿西北路径穿越朝鲜半岛时,受到半岛地形的巨大影响,风速和波高都明显降低。 相似文献
10.
A background error covariance model of significant wave height employing Monte Carlo simulation 总被引：1，自引：0，他引：1
The quality of background error statistics is one of the key components for successful assimilation of observations in a numerical model.The background error covariance(BEC) of ocean waves is generally estimated under an assumption that it is stationary over a period of time and uniform over a domain.However,error statistics are in fact functions of the physical processes governing the meteorological situation and vary with the wave condition.In this paper,we simulated the BEC of the significant wave height(SWH) employing Monte Carlo methods.An interesting result is that the BEC varies consistently with the mean wave direction(MWD).In the model domain,the BEC of the SWH decreases significantly when the MWD changes abruptly.A new BEC model of the SWH based on the correlation between the BEC and MWD was then developed.A case study of regional data assimilation was performed,where the SWH observations of buoy 22001 were used to assess the SWH hindcast.The results show that the new BEC model benefits wave prediction and allows reasonable approximations of anisotropy and inhomogeneous errors. 相似文献
11.
A new method using group-induced second-order long waves (GSLW) to describe wave groups is presented in this paper on the basis of the GSLW theory by Longuet- Higgins and Steward (1964) . In the method , the parabolic relationship between GSLW and the wave envelope is first deduced , and then the distribution function of GSLW amplitude is derived . Thus, the formulae in terms of the moments of GSLW and short wave spectra for the average time duration and the mean length of runs of wave heights exceeding a certain level can be derived . A new groupiness factor equivalent to half the mean wave number in wave groups is defined by taking into account the widths of spectra of GSLW and short waves . Compared with theoretical results of others , ours are closer to measured wave data . 相似文献
12.
Numerical simulation of 3-D wave crests 总被引：1，自引：0，他引：1
YU Dingyong * ZHANG Hanyuan College of Engineering Ocean University of China Qingdao P..R.China 《中国海洋大学学报(英文版)》2003,2(1):100-105
1 Introduction Anefficientwaytostudywaveforceonoffshorestructuresisthroughphysicalandnumericalwavesim ulation .Althoughmanysimulationsof 2 Dregularorirregularwaveshavesuccessfullybeencarriedoutinlaboratorythroughwindandwavegenerator ,itisstillratherdifficulttosimulate 3 Drandomwavesinlabo ratory .Therefore ,numericalsimulationiswidelyusedinsuchstudies (Baietal.,2 0 0 0 ;Zhuetal.,1999) .Tobuildlargeoffshorestructureslikemarineairports ,itisofinteresttostudytheeffectof 3 Dwaves .Goda(1994 … 相似文献
13.
This study was conducted on the spatial distribution characteristics of surface tidal currents in the southwestern Taiwan Strait based on the quasi-harmonic analysis of current data obtained by two high frequency surface wave radar (HFSWR) systems. The analysis shows that the tidal current pattern in the southwestern Taiwan Strait is primarily semi-diurnal and influenced significantly by shallow water constituents. The spatial distribution of tidal current ellipses of M2 is probably affected by the interaction between two different systems of tide wave, one from the northern mouth of Taiwan Strait and the other from the Bashi Channel. The directions of the major axes of M2 tidal current ellipses coincide roughly with the axis of the Taiwan Strait. The spatial distribution of the magnitudes of the probable maximum current velocity (PMCS) shows gradual increase of the velocity from northeast to southwest, which is in accordance with the spatial distribution of the measured maximum current velocity (MMCS). The directions of the residual currents are in accordance with the direction of the prevailing monsoon wind at the Taiwan Strait and the direction of the Taiwan warm current during summer. The bathymetry also shows a significant effect on the spatial distribution characteristics of tidal currents. 相似文献
14.
介绍了半波谐振贴片的理论,并利用HFSS分别对采用微带和同轴两种方式馈电的中心频率为12GHZ的平面贴片天线进行了仿真.仿真结果表明:当改变微带与同轴传输线馈电位置时,对于微带馈电方式,要实现单频点,取贴片的长边中点效果较好;如果偏离该中心点,将具有双频点特性.而采用同轴馈电时,所研究的几个馈电点位置中也是贴片长边中点相对较好,如偏离该中心点,频率将偏离中心频率. 相似文献
15.
REPRESENTATION OF STATISTICAL PROPERTIES OF WAVE GROUPS FOR SEA PROCESSES WITH DOUBLE-PEAKED SPECTRA
A method using group-induced second-order long waves(GSLW) to represent statistical properties of wave groups with double-peaked spectra is put forward in this paper on the basis of the GSLW theory. The GSLW is regarded as a weighted linear superimposition of the second-order long Wave induced by the low peak frequency section and that induced by the high peak frequency section. There is a parabolic relationship between the GSLW and the wave envelope. Then the probability density function and the distribution function of the GSLW amplitude are derived. Thus the formulas for the average time duration and the mean length of runs can be derived. Good agreement between theoretical results and measured values was achieved. as verified with the measured double-peaked spectra in different regions. 相似文献
16.
T/P,Jason��1�������ټ���Ч���ߵ���֤��Ƚ� 总被引：2，自引：0，他引：2
????T/P(TOPEX/POSEIDON)????????????????????????????????????T/P?????????????????????????????????????????????????????????У??????С????????????????????????????????????????????????????Ч??????T/P?????Ч???????0.3m??????T/P????????Jason??1?????????????????????????????????????????????????????????????????????????????????????????????????????á?T/P??Jason??1????????????????Ч?????????????????????????0.21 m??0.05 m?? 相似文献
17.
The paper introduces a new approach to estimating the T-year return-period wave height (TRPW), i.e. the wave height expected to occur in T-year, from two sets of observed extreme data and on the basis of the maximum entropy principle. The main points of the approach are as follows. 1) A maximum entropy probability density function (PDF) for the extreme wave height H is derived from a Euler equation subject to some necessary and rational constraints. 2) The parameters in the function are expressed in terms of the mth moment of H. 3) This PDF is convenient to theoretical and practical applications as it is simple and its four parameters are easy to be determined from observed extreme data. An example is given for estimating the TRPW in 50 and 100 years by the present approach and by some currently used methods using observed data at two hydrographic stations.The comparison of the estimated results shows that the present approach is quite similar to the Pearson-Ⅲ and Gumbel methods. 相似文献
18.
Significant wave height is an important criterion in designing coastal and offshore structures. Based on the orthogonality
principle, the linear mean square estimation method is applied to calculate significant wave height in this paper. Twenty-eight-year
time series of wave data collected from three ocean buoys near San Francisco along the California coast are analyzed. It is
proved theoretically that the computation error will be reduced by using as many measured data as possible for the calculation
of significant wave height. Measured significant wave height at one buoy location is compared with the calculated value based
on the data from two other adjacent buoys. The results indicate that the linear mean square estimation method can be well
applied to the calculation and prediction of significant wave height in coastal regions. 相似文献
19.
This paper presents a method developed for estimating wave height from synthetic aperture radar (SAR) imagery without prior assumption of noise distribution. It is based on two-dimenslonal ocean wave spectra retrieved from fully calibrated SAR images. Wen‘s spectrum was used as first-guess wave spectrum in the retrieval process. Comparison of the estimated wave height obtained by this method from two ERS-1 SAR subimages dated 23 July 1994 with in-situ measurements showed that the method works well. 相似文献
20.
楼菁 《中国海洋湖沼学报》1994,12(4):361-371
A numerical model based on the mild-slope equation of water wave propagation over complicated bathymetry,taking into account the combined effects of refraction,diffraction and dissipation due to wavebreaking is presented.Wave breaking is simulated by modifying the wave height probability density func-tion and the wave energy dissipation mechanism is parameterized according to that of the hydraulic jumpformulation.Solutions of the wave height,phase function,and the wave direction at every grid point areobtained by finite difference approximation of the governing equations,using Gauss-Seidel Iterative Method(GSIM)row by row.Its computational convenience allows it to be applied to large coast regions tostudy the wave transformation problem.Several case studies have been made and the results compare verywell with the experiment data and other model solutions.The capability and utility of the model forreal coast areas are illustrated by application to a shallow bay of northeast Australia. 相似文献