消浪室宽度对可渗明基床开孔沉箱消浪性能影响研究

开孔沉箱是将传统沉箱的前壁开孔,使沉箱前的入射波浪与反射波浪非同相位叠加,达到消能目的。消浪室是开孔沉箱的重要特征结构,其宽度对开孔沉箱的消浪性能具有重要影响。针对可渗明基床开孔沉箱,赋予消浪室宽度以较大的变化范围,开展专项物模试验,研究探讨了在规则波与不规则波作用下,相对消浪室宽度对可渗明基床开孔沉箱前波高反射系数的影响规律,发现反射系数随相对消浪室宽度的增加呈减小—增大—减小的振荡特性,这一发现有别于前人的研究成果,对工程中开孔沉箱消浪室结构的优化设计具有借鉴意义。同时,对试验工况进行数值模拟和解析计算,以物模试验值为标准,评价两种方法在研究相对消浪室宽度对开孔沉箱波高反射系数影响时的规律把握能力及计算精度,对工程中应用这两种方法给出相关建议。     

开孔沉箱结构消浪效果和水动力特征试验探究——以日照港岚山港区码头为例

由于开孔前墙和消浪室具有强扰动作用,所以开孔沉箱结构具有很好的消浪效果。本文通过日照港岚山港区码头开孔沉箱结构的物理模型试验,研究了沉箱不同开孔位置的消浪效果和水动力特征,分析了不同方案的反射系数和越浪量。结果表明：水位对反射系数的影响较大,开孔位置较高的方案,其消浪性能较好,且越浪量较小。选择反射系数和越浪量均较小的设计方案进行了水动力试验,结果表明：水平力最大时对应的浮托力约为最大浮托力的60%;浮托力最大时对应的水平力约为最大水平力的75%;波浪对开孔沉箱的作用主要集中于外壁迎浪侧,内部结构受到的波浪力很小;第二消浪室波浪力小于第一消浪室。     

双消浪室局部开孔沉箱防波堤反射特性的理论与试验研究

双消浪室局部开孔沉箱防波堤具有低反射、结构受力小、适宜较大水深和工程造价低等优点。为明确双消浪室局部开孔沉箱水动力特性的主要影响因素,采用理论分析和物理模型试验相结合的方法,对规则波和不规则波作用下双消浪室局部开孔沉箱防波堤的反射特性进行研究。基于势流理论,建立规则波和不规则波对局部开孔沉箱防波堤作用的三维解析解,采用二次压力损失边界条件考虑沉箱开孔墙对波浪运动的影响,利用周期性边界条件考虑防波堤结构沿长度方向的周期性变化。开展相应规则波和不规则波物理模型试验,验证理论模型的合理性。通过算例分析,研究不同波浪要素和结构参数对防波堤反射特性的影响。研究表明:双消浪室局部开孔沉箱相对消浪室宽度取值为0.08~0.20,沉箱前墙开孔率大于后墙开孔率时,防波堤在较大波浪频率范围内消波效果显著;当前后墙的开孔率相等时,防波堤反射系数的最小值随着开孔率增大而减小。     

多消浪室开孔沉箱消浪特性的数值模拟研究

本文基于雷诺平均的Navier-Stokes方程和k-ε模型求解湍流流动,采用流体体积法(Volume of Fluid,VOF)追踪自由表面运动,建立无反射波浪数值水槽,对多消浪室开孔沉箱的消浪特性进行数值模拟研究。将单消浪室和多消浪室开孔沉箱反射系数和结构前波面分布的数值分析结果与物理模型试验结果进行对比验证,两者符合良好。利用数值算例,研究多消浪室开孔沉箱的反射特性以及开孔结构附近的速度场和湍流强度分布。分析结果表明:波浪与开孔沉箱相互作用时,涡旋和湍动主要分布在开孔墙和消浪室内部自由表面附近;与单消浪室开孔沉箱相比,多消浪室开孔沉箱可以更有效的耗散波浪能量,降低结构的反射系数。本文分析结果可为开孔沉箱结构的工程设计提供参考依据。     

单层开缝板沉箱防波堤水动力学特性研究

用阻抗分析方法,对有一块开缝板和一个消浪室组成的开缝板沉箱防波堤的波浪反射系数进行系统的研究。在对开缝板消波机理分析基础上,导出一个所有参数都可计算的、完全封闭的波浪反射系数理论公式。该式物理概念明确、结构简单,与已知学者的试验成果对比,理论与试验吻合良好。     

明基床开孔沉箱不规则波反射系数试验研究

通过二维波浪水槽物模试验,在考虑消浪室相对宽度、相对水深、相对波高、开孔率对反射系数的影响基础上,针对明基床开孔沉箱的工程应用,引入相对基床高度新的影响因素,通过控制单一变量原则分析各因素和反射率的关系,采用多元回归给出明基床开孔沉箱不规则波浪反射系数的计算公式,对明基床开孔沉箱的消浪机理进行了有益的探索,研究成果为工程设计及应用提供了一种简捷可靠的计算方法。     

多消浪室局部开孔沉箱防波堤反射特性的迭代解析研究

基于势流理论,对多消浪室局部开孔沉箱防波堤的反射特性进行解析研究。研究中采用开孔墙处的二次压力损失边界条件,可以直接考虑波高对于开孔墙处能量损失的影响。利用匹配特征函数展开法和迭代方法得到当前问题的解析解。收敛性验证表明,迭代计算和级数解均具有良好的收敛性。该解析解的计算结果与分区边界元的数值计算结果一致,并且与已有的试验结果符合良好。通过算例分析,研究开孔沉箱防波堤反射系数的主要影响因素。结果表明：与单消浪室开孔沉箱防波堤相比,多消浪室开孔沉箱防波堤可以在更宽的波浪频率范围内保持低反射;增大开孔墙的开孔率,有利于降低多消浪室开孔沉箱防波堤的反射系数;当开孔墙的开孔率沿着入射波方向依次递减时,多消浪室开孔沉箱防波堤的反射系数较小。本文所建立的解析模型简单可靠,可用于工程初步设计中分析开孔沉箱防波堤的水动力性能。     

箱型浮式消浪设施水动力特性研究

为研究敷设消浪材料不同构造浮箱的消浪性能,通过物模试验得到规则波作用下不同周期、不同波高、不同锚泊方式及不同结构形式下浮箱的透射系数(C_t)、反射系数(C_r)及波能衰减系数(C_s)。研究结果表明:随着相对堤宽(B/L)的增大,不同构造浮箱的透射系数均逐渐减小,反射系数逐渐增大,波能衰减系数逐渐增大;敷设消浪材料的浮堤相比于单浮箱透射系数减小了0.10左右,而采用方箱-垂直板式构造的浮堤消浪性能相对于单浮箱透射系数减小了0.10～0.15,且敷设消浪材料的浮堤结构在研究的2种波高下,相对堤宽达到0.30时,透射系数可减小到0.25;当浮堤采用张紧式锚泊时,其消浪性能相对于悬链式锚泊浮堤减小了0.10左右,通过对比不同构造浮箱的消浪性能,可为实际工程设计提供参考。     

明基床上开孔沉箱稳定性试验研究

通过水槽内规则波以及不规则波作用下明基床上开孔沉箱的稳定性试验,分析研究了三种基床高度上开孔沉箱的稳定性与相对基床高度、消浪室相对宽度、相对水深、波陡以及开孔率等因素间的相关关系,并利用最小二乘法给出开孔沉箱最小自重与其影响因素间的拟合公式,同时将计算值与试验值进行比较,二者吻合较好,试验结果可供工程设计参考应用。     

明基床上开孔沉箱总力矩试验研究

通过二维水槽内规则波以及不规则波作用下开孔沉箱的受力试验研究,分析研究了明基床上开孔沉箱所受的总力矩与相对基床高度、消浪室相对宽度、相对水深、波陡以及开孔率等影响因素间的相关关系,并利用最小二乘法给出总力矩比值(开孔沉箱/实体沉箱)与其影响因素间的拟合公式,同时将计算值与试验值对比,二者吻合较好,所得经验关系式可供工程设计参考。     

新型直立式透空堤消浪性能数值研究

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。     

Interaction Between Waves and A Comb-Type Breakwater

The characteristics of wave transmission, reflection and energy dissipation of comb-type caisson breakwaters are studied through laboratory physical model tests. Regular and irregular waves, with a wide range of wave heights and periods and a constant water depth, are considered. Different dimensions of each portion of the comb-type caisson breakwater are tested. Empirical formulae for calculating the reduction coefficient k, which is the ratio of horizontal wave force on unit length of the comb-type breakwater to that on unit length of the vertical wall breakwater, and for calculating the reflection coefficient of waves k, are obtained from the measurements. The comb-type caisson breakwater has been found to be very efficient in dissipating incident wave energy and in reducing wave reflection, and has already been used for the construction of an island breakwater in the Dayao Bay of Dalian Port, Liaoning Province, China. Compared with the cost of a common caisson breakwater, about 24. 5% of the investm     

基于SPH方法的开孔沉箱比尺效应研究

由于在前壁上设置了尺寸较小的孔,开孔沉箱受流体黏性力作用显著,依照弗劳德数相似准则设计模型存在比尺效应。为揭示比尺效应,建立了模拟波浪与开孔沉箱相互作用的光滑粒子流体动力学(SPH)模型。其中流体运动由连续性方程和Navier-Stokes方程控制,固壁边界由改进的动力边界粒子施加。模型收敛性通过分析不同粒子分辨率下的波浪反射系数得到,模型精度通过比较计算与理论波浪反射系数证明。使用经过验证的SPH模型,计算并比较了不同几何比尺和开孔率下开孔沉箱附近的涡量场、箱体外侧的波面时程曲线和波浪反射系数。结果表明,随着模型几何比尺的减小,开孔沉箱受到偏大的流体黏性力,致使更多波能在湍流运动中耗散,进而减小了波浪反射系数并降低了箱体外侧的波面高度。     

Dynamic pressures and forces exerted on impermeable and seaside perforated semicircular breakwaters due to regular waves

The semicircular breakwater (SBW) is a composite breakwater consisting of a semicircular caisson resting on a rubble mound. The SBW function as a barrier dissipates the incident wave energy and creates tranquillity on its leeside. The dynamic pressures due to regular waves exerted on seaside perforated SBWs with 7 and 11% of exposed surface area with perforations were measured. The measured pressures are compared with those exerted on impermeable SBWs. In addition, the forces exerted on the caisson alone are measured. The reflection coefficient, measured total forces on the caisson of the models, and the pressures are presented as functions of relative water depth. The effect of the water depth and the percentage of perforations on the above stated variables are examined, details of which are reported in this paper.     

Simplified analytical solutions for wave interaction with absorbing-type caisson breakwaters

Simplified analytical solutions are presented to model the interaction of linear waves with absorbing-type caisson breakwaters, which possess one, or two, perforated or slotted front faces which result in one, or two, interior fluid regions (chambers). The perforated/slotted surfaces are idealized as thin porous plates. Energy dissipation in the interior fluid region(s) inside the breakwater is modelled through a damping function. Under the assumption of potential flow and linear wave theory a boundary-value problem may then be formulated to describe wave interaction with the idealized structure. A solution to this simplified problem may be obtained by an eigenfunction expansion technique and an explicit analytical expression may be obtained for the reflected wave height. Using the experimental work of previous authors, damping coefficients are determined for both single and double chamber absorbing-type caisson breakwaters. Based on the damping for a single perforated-wall breakwater, a methodology is proposed to enable the estimation of the damping coefficients for a breakwater with two chambers. The theoretical predictions of the reflection coefficients for the two-chamber structures using the present model are compared with those obtained from laboratory experiments by other authors. It is found that the inclusion of the damping in the interior fluid region gives rise to improved agreement between theory and experiment.     

Wave Attenuation Performance and the Influencing Factors of A Lower Arc-Plate Breakwater

Comprehensive experimental and numerical studies have been undertaken to investigate wave energy dissipation performance and main influencing factors of a lower arc-plate breakwater. The numerical model, which considers nonlinear interactions between waves and the arc-plate breakwater, has been constructed by using the velocity wave- generating method, the volume of fluid (VOF) method and the finite volume method. The results show that the relative width, relative height and relative submergence of the breakwater are three main influencing factors and have significant influence on wave energy dissipation of the lower arc-plate open breakwater. The transmission coefficient is found to decrease with the increasing relative width, and the minimum transmission coefficient is 0.15 when the relative width is 0.45. The reflection coefficient is found to vary slightly with the relative width, and the maximum reflection coefficient is 0.53 when the relative width is 0.45. The transmission and reflection coefficients are shown to increase with the relative wave height for approximately 85% of the experimental tests when the relative width is 0.19 0.45. The transmission coefficients at relative submergences of 0.04, 0.02 and 0 are clearly shown to be greater than those at relative submergences of 0.02 and 0.04, while the reflection coefficient exhibits the opposite relationship. After the wave interacts with the lower arc-plate breakwater, the wave energy is mainly converted into transmission, reflection and dissipation energies. The wave attenuation performance is clearly weakened for waves with greater heights and longer periods.     

珊瑚岸礁破碎带附近波浪演化实验研究

通过波浪水槽实验对珊瑚岸礁破碎带附近波浪演变规律开展研究,实验采用了概化的岸礁模型,测试了4种礁坪水深、4种礁前斜坡坡度和一系列入射波高的组合工况。对破碎带宽度和破碎带附近波浪的入射、反射、透射以及能量耗散进行了测量分析,透射波的计算考虑了礁坪上高次谐波的影响。结果表明:礁坪水深和入射深水波高的比值(即礁坪相对水深)是影响岸礁破碎带附近波浪演化的关键参数,而礁前斜坡坡度的影响在本文测量的范围内可以忽略不计。破碎带宽度与礁坪上浅水波波长为同一数量级,并与礁坪相对水深成反比;透射系数随礁坪相对水深的增大呈线性增长,而反射系数的变化却无类似规律;岸礁能够削弱超过50%入射波能,礁坪相对水深越小,波浪破碎造成的能量耗散越大。