共查询到18条相似文献，搜索用时 109 毫秒
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与海床不可渗透的情况相比,波浪在可渗透海床上传播时会发生波能衰减。本文将基于可渗透海床上一维修正型缓坡方程,建立方程求解的有限差分模型。将通过与不可渗透海床上矩形Bragg防波堤对波浪反射系数解析解的对比,验证有限差分模型的正确性和适用性。将进一步研究海床可渗透情况下,海床的渗透性参数、坝体的相对宽度、数量、浸没度对波浪反射系数的影响及其与海床不可渗透情况下的差异。本文研究发现,Bragg共振发生时的反射系数随坝体数量的增多而增大,随海床渗透性参数和坝体浸没度的增大而减小,并且存在一个坝体相对宽度值会使Bragg共振反射达到最大。相较于海床不可渗透的情况,发生Bragg共振反射的波浪频率几乎相同,但反射系数减小,而且零反射（或全透射）现象不再存在。 相似文献
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基于线性势流理论,利用高阶边界元法研究了规则波在三维局部渗透海床上的传播。根据Darcy渗透定律推导出渗透海床的控制方程,利用渗透海床顶部和海底处法向速度和压强连续条件得到渗透海床顶部满足的边界条件。根据绕射理论,利用满足自由水面条件的格林函数建立了求解渗透海床绕射势的边界积分方程,采用高阶边界元方法求解边界积分方程进而得到自由水面的绕射势和波浪在局部渗透海床上传播过程中幅值的变化情况。通过与已发表的波浪对圆柱形暗礁的时域全绕射结果对比,证明了本文建立的频域方法计算波幅的正确性和有效性。利用这一模型研究了三维矩形渗透海床区域上波浪的传播特性,并分析了入射波波长、海床渗透特性系数等参数对波浪传播的影响。 相似文献
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《中国海洋大学学报(自然科学版)》2021,(Z1)
基于海床土体变形、渗流和溶质运移的耦合数值计算模型,考虑波浪沿沙丘状海底地形传播的浅水效应,本文分析了沙丘状海床内部孔隙水渗流特征和海水中溶质进入沉积物的运移特征,并通过与平底海床计算结果的对比,分析了沙丘状海底地形对溶质迁移的影响特征。结果分析表明,相对于平底海床,沙丘状海床一定深度内孔隙水渗流呈现明显的二维特征,进一步加速了溶质在沉积物中的迁移速率;对于沙丘状海底,对流和水动力弥散均有效促进了溶质向沉积物中的迁移,其中,对流作用相对稳定,而水动力弥散作用随着波浪作用时间的增加而不断减弱。参数分析表明,沙丘地形对溶质运移过程的影响程度基本不受波高的影响,但其随着波浪周期、水深和坡角的增大而增大,随着剪切模量和渗透系数的增大而减小,其中坡角的影响最为显著。 相似文献
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波浪在可渗海床上传播时的衰减 总被引：4，自引：0，他引：4
在以往的波浪理论研究中,通常假定海床是不可渗的。但在浅水区,海床的可渗性对波浪的传播有一定影响,它能引起波高的衰减,同时波浪也能够引起海床的变形、滑动、甚至液化。当海床的弹性小,渗透性大时,波浪与可渗海床的这种相互作用更为明显。本文通过对波浪场控制方程－拉普拉斯方程和弹性海床的控制方程－比奥方程联合解析求解,给出了海床土体响应、孔隙水压变化规律,以及波高在传播过程中的衰减。 相似文献
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海洋资源开发引起海底软黏土的结构性破坏,导致土体强度弱化,在百年一遇的极端波浪作用时极易发生斜坡海床的局部失稳甚至大范围海底滑坡,给海洋工程建设和正常运营带来严重影响。目前,主要采用极限平衡法评价这类海底斜坡,但该法只能给出近似解。基于极限分析上限方法,推导了极端波浪诱发的波压力对斜坡海床的做功功率,建立了外力功与内能耗散率平衡方程;利用最优化方法,结合数值积分和强度折减技术,求解了不同时刻的斜坡海床稳定性系数,并针对扰动后的斜坡海床开展了有限元解的对比验证。在此基础上,深入探讨了不同波浪参数(波长、波高和水深)和坡长小于一个波长等极端条件下的海底斜坡稳定性。 相似文献
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珊瑚礁坪波浪的衰减特性分析 总被引：1，自引：0，他引：1
珊瑚礁海底与一般的礁石或泥沙海底结构相差很大，波浪衰减特性也相差较大。根据实测海浪资料，讨论波浪在礁坪上传播的衰减特性和波浪能量的转移。分析结果表明，在相对水深为0．0613—0．0867之间，波浪传播单位距离(100m)的波高衰减系数为22．09％—46．56％，平均值为31．35％；波能衰减系数为33．74％—53．23％，平均值为43．61％。波浪在礁坪上传播过程中，高频损失的能量多于低频，谱能量向低频转移。应用统计方法得到波高、波能衰减系数与相对水深D/L关系的拟合方程。 相似文献
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波浪作用下海床的有效应力分析 总被引：4，自引：0，他引：4
波浪作用下海床的稳定性分析是海洋工程地质评价的重要内容。海床的稳定性可通过计算分析其随时间变化的有效应力场来评估。本文建议了一个周期荷载作用下土体的本构模型 ,并用于计算波浪作用下海床的应力与变形。采用Biot固结理论和有限单元法 ,分析了海床的动态应力场与孔隙水压力场。波浪作用下两种渗透系数时有效应力的动态变化过程结果对比 ,反映了渗透消散作用对海床有效应力变化的影响 相似文献
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In this study, a new analytical solution for the wave-induced seabed response in a multi-layered poro-elastic seabed is developed. The seabed is treated as a multi-layered porous medium and characterized by Biot’s theory. The displacements of the solid skeleton and the pore pressure are expressed in terms of two scalar potentials and one vector. Then, the Biot’s dynamic equation can be solved using Fourier transformation and reducing to Helmholtz equations. To obtain the general solutions for the multi-layered poro-elastic seabed in the frequency-wave-number domain, the transmission and reflection matrices (TRM) method is used to form the equivalent stiffness. Using the boundary conditions and continuous conditions, the frequency-wave-number domain solutions are obtained. Finally, the time-space domain solutions for the multi-layered poro-elastic seabed are obtained by means of the inverse Fourier transformation with respect to the horizontal coordinate. Based on the new solution, a parametric study is carried out to examine the effects of soil characteristics (number of layers, permeability and shear modulus) and wave characteristics (water depth and wave steepness) on seabed responses. The results indicate that the seabed response is affected significantly by permeability, shear modulus and relative water depth. 相似文献
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基于非静压单相流模型NHWAVE建立了高精度二维数值波浪水槽,采用日本2011年实测真实海啸波型系统研究了海啸波在岛礁上传播变形的规律,并且分析了波高、礁坪淹没水深和礁前斜坡坡度等因素对孤立波和真实海啸传播变形的影响。结果表明,相比孤立波,类海啸波的波长明显大于孤立波波长,在测点处引起的水面变化持续时间更长,同等波高情况下真实海啸波型比孤立波能够携带更多的能量,与岛礁的相互作用也更为复杂,在礁坪上形成的淹没水深约为孤立波的两倍。礁前斜坡坡度和礁坪淹没水深均对类海啸波的反射和透射系数有显著影响。随着礁前斜坡坡度的增加,反射系数和透射系数均逐渐增加。随着礁坪淹没水深的增加,反射系数逐渐减小,而透射系数逐渐增大。但是,反射系数和透射系数均随着入射波高的增加而逐渐减小。 相似文献
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The numerical study of wave-induced pore water pressure response in highly permeable seabed 总被引：2，自引：1，他引：1
The coupling numerical model of wave interaction with porous medium is used to study waveinduced pore water pressure in high permeability seabed.In the model,the wave field solver is based on the two dimensional Reynolds-averaged Navier-Stokes(RANS) equations with a k-ε closure,and Forchheimer equations are adopted for flow within the porous media.By introducing a Velocity-Pressure Correction equation for the wave flow and porous flow,a highly efficient coupling between the two flows is implemented.The numerical tests are conducted to study the effects of seabed thickness,porosity,particle size and intrinsic permeability coefficient on regular wave and solitary wave-induced pore water pressure response.The results indicate that,as compared with regular wave-induced,solitary wave-induced pore water pressure has larger values and stronger action on seabed with different parameters.The results also clearly show the flow characteristics of pore water flow within seabed and water wave flow on seabed.The maximum pore water flow velocities within seabed under solitary wave action are higher than those under regular wave action. 相似文献
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By applying the linear water wave theory and the eigenfunction expansion method, the wave reflection by a vertical wall with a horizontal submerged porous plate is investigated in this paper. The numerical results, concerning the effects of the dimensionless plate length, the relative water depth, and the porous effect parameter of the plate on the wave loads on the plate and the wave height near the wall as well as the reflection coefficient, are discussed. It is found that the submerged plate increases the complexity of the phenomenon related to the wave reflection and refraction in the close region of the wall, and leads to the occurrence of the phenomenon of wave trapping. The results indicate that there may exist a process of focusing wave energy near the wall for small dimensionless porous effect parameters, whereas the increase of the dimensionless porous effect parameter decreases gradually the wave height until setdown occurs. The behavior of a larger plate with proper porosity is similar to that of a wave absorber which can significantly suppress not only the wave height above the plate but also the reflection waves. The ability of the porous plate to reduce the wave height on the wall surface is, in general, directly proportional to the dimensionless plate length and may be strongest for a proper value of the dimensionless porous effect parameter. It is also demonstrated that the wave loads on a porous plate are smaller than those on an impermeable plate. 相似文献
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《Coastal Engineering》2004,51(3):223-236
A computational model is developed to investigate the wave damping characteristics of a periodic array of porous bars. The transmission and reflection coefficients as well as the wave energy dissipation are evaluated relating to the physical properties and geometric factors of bars. It is shown that the porosity, number, width and height of bars all play important roles in the wave damping characteristics, compared to other factors such as the intrinsic permeability. It is observed that like impermeable bars, permeable bars display Bragg phenomenon. However, Bragg reflection produced by permeable bars is smaller than that by impermeable bars. Permeable bars reflect smaller waves, transmit smaller waves and dissipate more wave energy. It is indicated that if the porosity increases, both the reflection and transmission coefficients decrease and more wave energy is dissipated. Further, it is found that the porosity controls the magnitude, but not the oscillation frequency of the reflection coefficient, which depends only on the number of bars. 相似文献
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为使防波堤同时具有良好的掩护效果和水体交换能力,提出了两种带有透浪通道的新型直立式防波堤。基于Fluent求解器建立了三维数值波浪水槽,通过与试验结果对比,验证了该数值水槽求解波浪与透空堤作用具有较高的精度。对两种防波堤在规则波作用下的透浪特性进行了研究,结果表明:透射系数K_t与透空率呈正线性相关,且可通过调整透浪通道间距,使相同透空率下K_t降低20%～30%。对同一结构,K_t随相对波长的增大而显著增大,但受相对波高的影响较小。在透空率大于0.16后,异型沉箱防波堤的消浪性能明显优于错位沉箱。基于数值计算结果,给出了以上两种透空堤波浪透射系数的经验公式。 相似文献
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鉴于双弧板式透空堤的消浪性能仍不理想，提出了一种潜堤—双弧板组合结构，并基于OpenFOAM软件建立了波浪与该结构相互作用的数值模型，采用试验结果对所建数值模型进行验证。在此基础上，讨论了该新型结构的消浪特性、波压力分布特征以及所受波浪力的影响因素。结果表明，透射系数随相对板宽的增大而减小，反射系数则相反。透射与反射系数随相对潜深的变化较为显著。当结构位于静水位上方（即相对潜深为-0.05）时，透射系数最小而反射系数最大；当结构位于静水位下方（即相对潜深为0.05）时，透射系数最大而反射系数最小。该组合结构两块弧板上下表面的正负压力变化关于横轴近似对称，不同测点处的压力值差异显著。水平波浪力与垂直波浪力的变化趋势大致相似，但垂直波浪力远大于水平波浪力。研究结果可为其工程应用提供理论指导与技术支撑。 相似文献
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This paper presents numerical solutions for the wave reflection from submerged porous structures in front of the impermeable vertical breakwater. A new time-dependent mild-slope equation involves the parameters of the porous medium including the porosity, the friction factor and the inertia coefficient, etc. is derived for solving the boundary value problem. A comprehensive comparison between the present model and the existing analytical solution for the case of simple rectangular geometries of the submerged structure is performed first. Then, more complicated cases such as the inclined and trapezoidal submerged porous structures in front of the vertical breakwater with sloping bottom are considered. This study also examines the effects of the permeable properties and the geometric configurations of the porous structure to the wave reflection. It is found that the submerged porous structure with trapezoidal shape has more efficiency to reduce the wave reflection than that of triangular shape. The numerical results show that the minimum wave reflection is occurred when the breakwater is located at the intermediate water depth. 相似文献