共查询到20条相似文献，搜索用时 500 毫秒
1.
海草所形成的植物消波体系能有效防止岸线的侵蚀。利用Sánchez-González等的实验数据分析了波浪非线性对海草消波特性的影响。研究结果表明，相对水深和波陡对海草床的波能衰减系数影响依赖于海草淹没度。相对波高一定时，拖曳力系数随相对水深的增大而增大。对给定的相对水深，拖曳力系数随波陡的增大而减小。波浪非线性对于规则波和非规则波海草消波特性的影响并不一致。用无量纲参数（邱卡数、雷诺数、厄塞尔数）表达拖曳力系数的效果取决于拖曳力系数与无量纲参数的关系中是否充分考虑波浪非线性对拖曳力系数的影响。 相似文献
2.
为研究顺应式海洋平台慢漂运动的影响因素,以截断圆柱和漂浮方箱为例进行了不规则波作用下的慢漂运动模型试验。测量了不同系泊刚度条件下的漂浮方箱以及相同系泊刚度条件下的截断圆柱和漂浮方箱在静水中自由衰减运动和在不规则波中的运动响应,并将运动响应分解成一阶波频运动响应和二阶低频运动响应,分析了系泊刚度和浮体形状对浮体运动的影响。通过物理模型试验发现了系泊刚度及浮体形状对顺应式系泊浮体一阶运动标准差和二阶低频运动平均漂移值和标准差的关系。结果表明由于顺应式浮体的固有周期远离波浪谱峰周期时,系泊刚度以及浮体形状对慢漂运动的一阶运动响应影响不大;二阶低频运动相对偏离平衡位置的平均值和标准差均随系泊刚度增大而减小,浮体形状同样对慢漂运动的二阶低频纵荡运动响应影响较大。试验结果为实际海洋工程的外形选择和系泊刚度选择提供数据支持。 相似文献
3.
为了有效地考虑浮体慢漂运动对钢悬链线立管疲劳损伤的影响,提出了波频和慢漂运动组合作用下钢悬链线立管疲劳损伤简化计算的位置组合叠加法。其核心是:基于浮体慢漂运动概率分布选取若干典型慢漂位置,进行波频运动作用下钢悬链线立管动力响应分析;根据钢悬链线立管运动位置变化特征,截取若干慢漂位置对应的波频应力时程叠加到慢漂应力时程上,得到波频和慢漂运动的组合应力时程;编写基于雨流计数法的MATLAB程序处理立管各节点应力,采用海水环境下Do E.E型S-N曲线和Palmgren-Miner累积损伤准则计算立管各节点疲劳损伤。应用位置组合叠加法对某海域500 m水深的立管进行了疲劳分析,并与全耦合法、权重组合叠加法以及波频和慢漂疲劳损伤简单相加法的结果进行了对比,结果表明该方法具有较高的精度和效率。此外,进行了区域设定系数、波浪高度、波浪周期和土壤表面剪切强度等参数对组合作用下立管疲劳损伤的敏感性分析。 相似文献
4.
使用风浪经验公式和风浪传入近岸的小振幅波动理论计算并分析了地转条件下波生横向彻体切应力随风速、风区、水深等因素的变化规律。结果表明，彻体切应力随风速、风区的增大而增大，直到波浪达到完全成长状态，但增长速度并不规则；为更加直观的显示彻体切应力的海流驱动作用，将其与定常Ekman漂流中的风生湍粘性力进行了有意义的比较，结果表明，在中、高纬度的通常海况下两者具有相同量级，因此，在有波浪场存在的条件下，由风、浪共生海流的总体强度将比理论Ekman漂流大，并且不会完全符合Ekman漂流理论的转向规律，在表层尤其明显。由此说明，在一定情况下在风生漂流研究中考虑由地转引起的波生横向彻体切应力是非常必要的。 相似文献
5.
6.
准确预报船舶在波浪中的运动和力可以为船舶性能评估提供参考。采用naoe-FOAM-SJTU求解器，数值模拟固定和放开垂荡、纵摇自由度的KCS船在不同波长的迎浪规则波中的运动。首先运用数值造波方法生成不同波浪周期的Stokes一阶深水规则波，与Stokes波的理论值对比确保造波的准确性；然后计算固定或放开垂荡和纵摇自由度的KCS船在0.65 ≤ λ/L（波长/船长）≤1.95的遭遇波中的运动和阻力，研究KCS船的波浪增阻中绕射和辐射成分，且采用傅里叶分析法研究了运动与阻力的线性和非线性成分分布。结果表明，波浪绕射增阻受波长的影响不大，当波长接近船长时，船舶的垂荡和纵摇幅值以及波浪增阻均达到峰值，这主要由船体剧烈运动引起的辐射增阻导致，应避免船舶在此工况下航行。 相似文献
7.
灾害性波浪是中国沿海地区最具破坏性的自然灾害之一。采用开源程序OpenFOAM中interFoam求解器，对低顶海堤（在风暴潮和海平面上升情况下所面临的不利工况）的孤立波越浪特性开展数值模拟研究。通过孤立波冲击海堤的基准算例，验证模型在模拟波浪爬升和越浪过程中大变形波面以及剧烈波浪力方面的精度。基于验证的数值模型，对孤立波在低顶海堤上的越浪特征以及防浪墙高度对越浪的影响开展参数化研究。结果表明堤顶超高减小导致更为剧烈的越浪。针对尚无低顶海堤孤立波越浪量经验公式的问题，提出新的适用于堤顶超高小或为0的孤立波越浪量经验公式。此外，研究发现增加防浪墙高度可有效减少越浪，但防浪墙所受的波浪力也增大。综合考虑防浪墙减少越浪以及自身所受波浪力，针对文中研究采用的海堤截面和波浪条件，建议无量纲防浪墙高度取为1.00。 相似文献
8.
箱式超大型浮体结构在规则波中的水弹性响应研究 总被引：3，自引：5，他引：3
利用三维线性水弹性理论研究了箱式超大型浮体结构在正弦规则波中的动力响应，用Bernoulli-Euler梁解析解计算结构在真空中的动力特性，用弹性体三维势流理论计算结构的水动力系数，浮体结构在单位波幅规则波中的刚体运动幅值与DNV／WADAM程序的计算结果进行了比较，并给出了垂向弯曲模态的位移，弯矩随波浪频率的变化规律，由于箱式浮体结构的低阶固有频率很低，相应的弹性振型的响应与刚体运动耦合，结构在波浪中没有发现明显的低阶弹性模态谐振。 相似文献
9.
本文通过波浪水槽试验研究了大糙率礁面影响下波浪沿礁的演化和爬高规律，测试了一系列规则波工况并对比了光滑礁面和粗糙礁面的情况。结果分析表明：二次谐波是礁坪上透射波的重要组成成分，粗糙礁面使主频波和二次谐波减小，对更高阶波的影响不显著；相对礁坪水深是描述礁坪上波浪透射的关键参数，礁面从光滑变为粗糙时海岸附近透射系数显著减小，能量衰减系数平均增大了8%，但礁前反射系数与礁面糙率之间无明显关系；礁后岸滩爬高随着透射波高的增大而增长，最后拟合了本文试验条件下珊瑚礁大糙率礁面预测规则波爬高的关系式。 相似文献
10.
为分析碟形越浪式波能发电装置初步设计方案的合理性和不足,应用三维势流理论和波浪的辐射-衍射理论,结合水动力分析软件AQWA,计算在规则波浪作用下装置浮体6个自由度上运动的响应幅值算子(RAOs),考虑不规则波浪、风、流载荷的共同作用,对装置在工作海况和恶劣海况下的运动响应进行数值模拟分析,得到其时间历程结果。结果表明:装置结构外形设计合理,装置在其锚链张力腿锚泊系统定位下,运动响应满足工作稳定性要求和安全性要求。 相似文献
11.
Experimental Investigation on Breakup of Ice Floe on Waves 总被引：2，自引：0，他引：2
WANG Yongxue 《中国海洋工程》2000,14(4):511-516
Experimental investigation of for floe breakup on waves by use of non-refrigerated breakablematerials has been carried out.The incident wave heights for breakup of ice floe with different lengths,andthe influence of rigidity on reflection and transmission coeffcients are discussed.The experimental resultsshow that the ratio of the ice floe length,L_i,to the wavelength,L,is one of the significant factor affectingthe minimum wave height to cause fracture of ice floe,and another key factor is the ratio of the ice floethickness,h_i and L_i. 相似文献
12.
Experimental studies were conducted on a trapezoidal pendulum wave energy converter in regular waves. To obtain the incident wave height, the analytical method (AM) was used to separate the incident and reflected waves propagating in a wave flume by analysing wave records measured at two locations. The response amplitude operator (RAO), primary conversion efficiency and the total conversion efficiency of the wave energy converter were studied; furthermore, the power take-off damping coefficients corresponding to the load resistances in the experiment were also obtained. The findings demonstrate that the natural period for a pendulum wave energy converter is relatively large. A lower load resistance gives rise to a larger damping coefficient. The model shows relatively higher wave energy conversion efficiency in the range of 1.0?1.2 s for the incident wave period. The maximum primary conversion efficiency achieved was 55.5%, and the maximum overall conversion efficiency was 39.4%. 相似文献
13.
The slow drift motion of a floating body in a two-dimensional wave field has been investigated using a time-domain, fully nonlinear numerical model with non-reflective open boundaries. Preliminary computations were conducted for incident bichromatic waves, in which wave theories with different orders were applied in generating the waves required. The results show that the use of low-order theories generates undesirable free waves, and that fourth-order terms contribute markedly to low-frequency input. The motion of a rectangular floating body in response to nonlinear bichromatic waves was computed. The numerical results for small-amplitude incident waves agree reasonably well with the second-order approximation for both the steady and difference-frequency (Δσ) components in the body's motion. For relatively large waves, however, the 2Δσ component becomes predominant compared with the Δσ component. The motion of the body in irregular waves with different wave parameters has also been presented in order to discuss the validity range of a second-order approximation. 相似文献
14.
This paper describes a simple method for determining the wavelength of small amplitude waves under laboratory conditions where reflected wave components are present both with and without a mean current flow superimposed. It assumes a locally horizontal bed but requires no a priori assumption concerning the form of the dispersion relation with a coexisting current. Synchronous measurements of the water surface recorded along any straight line are analysed to yield Fourier coefficients at each location. It is then shown that for all practical conditions excluding a perfect standing wave, the average rate of change of wave phase in the chosen direction can be related directly to the component of incident wave number in that direction, irrespective of reflection coefficient or relative current strength. The technique has been applied to regular and bichromatic waves in a flume with an absorbing wave generator, and can also be applied in 3-D wave basins where waves and currents intersect at arbitrary angles. In combined wave–current experiments, by assuming the linear dispersion relation, it is also possible to estimate the effective current velocity. 相似文献
15.
以三锚系浮标系统为研究对象，基于AQWA与OrcaFlex软件开展了三锚系大型浮标系统运动响应特性数值模拟研究。对直径10 m的浮标结构在波浪荷载下的水动力特性进行研究，校核了浮标的初稳性和大倾角稳性特征，计算分析了浮标的附加质量、辐射阻尼、运动响应幅值算子RAO等水动力参数，阐明了不同风、浪、流工况下三锚系浮标与辅助浮筒的运动响应特性，揭示了浮标三锚链导缆孔处锚泊张力随入射角度、波高和周期等的变化规律。研究结果表明：该浮标稳性和随波性能较好。与无浮筒三锚系浮标相比，带辅助浮筒的三锚系浮标系统的运动响应和锚泊张力减小，随着波高和周期增大，三锚系浮标系泊锚链的极端张力值逐渐增大，尤其是在极端海况下，迎浪向锚链极端张力急剧增大。 相似文献
16.
Ice loads on a ship hull affect the safety of the hull structure and the ship maneuvering performance in ice-covered regions. A discrete element method （DEM） is used to simulate the interaction between drifting ice floes and a moving ship. The pancake ice floes are modelled with three-dimensional （3-D） dilated disk elements considering the buoyancy, drag force and additional mass induced by the current. The ship hull is modelled with 3D disks with overlaps. Ice loads on the ship hull are determined through the contact detection between ice floe element and ship hull element and the contact force calculation. The influences of different ice conditions （current velocities and directions, ice thicknesses, concentrations and ice floe sizes） and ship speeds are also examined on the dynamic ice force. The simulated results are compared qualitatively well with the existing field data and other numerical results. This work can be helpful in the shil3 structure design and the navigation securitv in ice-covered fields. 相似文献
17.
Numerical models which account for the multiple response modes of floating wave energy converters (WECs) in operating conditions require experimental data for validation. Measurement and observation of complex hydrodynamic mechanisms are also required to inform the development of modelling tools suitable for the simulation of response to extreme waves. Experimental measurements are reported of the motion of an axisymmetric float to regular and near-focused waves. The mechanical system, incident wave conditions and response in a 2D vertical plane are detailed to facilitate comparison to numerical simulations. The system comprises a heaving float connected to a counterweight by an inextensible cable over two pulleys to provide a simplified representation of the slowly varying surge constraint of a mooring system. Translation of the float is measured using an optical encoder. Motion in heave, surge and pitch are also determined by a position identification method based on analysis of video footage. For low frequency regular waves, the float prescribes an elliptical trajectory and the variation of response amplitude with wave amplitude is linear. At higher frequencies, drift of up to one-third of the float radius is observed and the float oscillates along an arc. More complex motions are observed due to the three large amplitude waves of a near-focused wave group. During these waves the upper surfaces of the float are partly immersed and motion occurs in heave, surge and pitch. 相似文献
18.
A harmonic wave group single run seakeeping procedure is developed, validated and compared with regular wave and transient wave group procedures, using an unsteady Reynolds averaged Navier–Stokes solver, although all procedures can be also implemented using experiments or potential flow. Incoming waves are generated by linear superposition of potential solution for a number of component waves. The regular wave procedure requires multiple runs, whereas single run procedures obtain the response amplitude operators (RAO) for a range of frequencies at a fixed speed, assuming linear ship response. The transient wave group procedure provides continuous RAO curves, while the harmonic wave group procedure obtains discrete transfer functions without focusing. Results are presented for heave and pitch response amplitudes and phases for the DTMB model 5512 in head waves. Verification and validation studies are performed for the transient wave group procedure. Validation is achieved at the average interval of 9.54 (%D). Comparisons of the procedures show that the harmonic wave group procedure is the most efficient, saving 75.8% on the computational cost compared with the regular wave procedure. Error values from all procedures are similar at 4 (%D). Harmonic wave group results are validated for a wide range of the Froude numbers, with satisfactory results. 相似文献
19.
Large-scale experiments on beach profile evolution and surf and swash zone sediment transport induced by long waves,wave groups and random waves 总被引：1，自引：0，他引：1
T.E. Baldock J.A. Alsina I. Caceres D. Vicinanza P. Contestabile H. Power A. Sanchez-Arcilla 《Coastal Engineering》2011
New large-scale laboratory data are presented on the influence of long waves, bichromatic wave groups and random waves on sediment transport in the surf and swash zones. Physical model testing was performed in the large-scale CIEM wave flume at UPC, Barcelona, as part of the SUSCO (swash zone response under grouping storm conditions) experiment in the Hydralab III program (Vicinanza et al., 2010). Fourteen different wave conditions were used, encompassing monochromatic waves, bichromatic wave groups and random waves. The experiments were designed specifically to compare variations in beach profile evolution between monochromatic waves and unsteady waves with the same mean energy flux. Each test commenced with approximately the same initial profile. The monochromatic conditions were perturbed with free long waves, and then subsequently substituted with bichromatic wave groups with different bandwidth and with random waves with varying groupiness. Beach profile measurements were made at half-hourly and hourly intervals, from which net cross-shore transport rates were calculated for the different wave conditions. Pairs of experiments with slightly different bandwidth or wave grouping show very similar net cross-shore sediment transport patterns, giving high confidence to the data set. Consistent with recent small-scale experiments, the data clearly show that in comparison to monochromatic conditions the bichromatic wave groups reduce onshore transport during accretive conditions and increase offshore transport during erosive conditions. The random waves have a similar influence to the bichromatic wave groups, promoting offshore transport, in comparison to the monochromatic conditions. The data also indicate that the free long waves promote onshore transport, but the conclusions are more tentative as a result of a few errors in the test schedule and modifications to the setup which reduced testing time. The experiments suggest that the inclusion of long wave and wave group sediment transport is important for improved near-shore morphological modeling of cross-shore beach profile evolution, and they provide a very comprehensive and controlled series of tests for evaluating numerical models. It is suggested that the large change in the beach response between monochromatic conditions and wave group conditions is a result of the increased significant and maximum wave heights in the wave groups, as much as the presence of the forced and free long waves induced by the groupiness. The equilibrium state model concept can provide a heuristic explanation of the influence of the wave groups on the bulk beach profile response if their effective relative fall velocity is larger than that of monochromatic waves with the same incident energy flux. 相似文献