双浮箱-双水平板式浮式防波堤试验研究

该文提出了双浮箱-双水平板式新型浮式防波堤结构,并对其水动力特性进行了规则波物理模型试验研究。探讨了相对宽度、相对波高和锚链刚度等因素对防波堤消浪性能、运动响应和锚链受力的影响,并与双浮箱结构的试验结果进行了比较分析。研究结果表明:在双浮箱下面安装两层水平板能有效提高防波堤的消浪性能,显著减小防波堤的运动响应;双浮箱-双水平板结构的波浪透射系数较双浮箱结构最多可减小0.4左右;当相对宽度B/L?0.30时,透射系数可以控制在0.35以下。因此,新型防波提展现出良好的工程应用前景。     

新型浮式防波堤消浪效果试验研究

通过一系列物理模型试验,研究一种新型(凹菱形)浮式防波堤的透浪系数,并与现有的浮箱式、废旧轮胎式、浮筏式等浮式防波堤进行对比。这种新型浮式防波堤的一个显著特点是在底部增加了阻尼,增加了波浪的能量消耗,从而减小了防波堤的透浪系数改善了其消浪效果。分析影响浮式防波堤透浪系数的主要因素为防波堤的相对宽度和相对水深。通过波浪水槽内的系列试验,研究两者对新型浮式防波堤透浪系数的影响,并给出临界透浪系数(C t=0.5)与两者的关系。在实际工程的设计和应用阶段,各种参量是相互影响的,讨论了波浪透射系数与各参数之间的关系。该浮式防波堤的消浪效果良好,为浮式防波堤的推广应用提供参考。     

柔性浮式防波堤消浪特性研究

针对圆柱形柔性浮式防波堤的消浪效果展开断面试验研究,分析其在规则波和不规则波作用下的消浪特性。通过大量水槽试验给出了圆柱形柔性浮式防波堤透射系数、反射系数、衰减系数与锚固方式、试验水深、相对宽度的变化关系。研究结果表明:该结构形式的浮式防波堤对短周期波浪消浪效果明显,而对长周期波浪消浪效果不佳;锚固方式和水深对消浪效果的影响较小;相对宽度是影响消浪效果的主要因素。研究成果可为由该结构连接成的"V"形浮式防波堤的锚固方式和摆放角度的设计提供参考。     

浮式防波堤研究进展

浮式防波堤与其他传统防波堤相比,可适应水深较大、地基软弱、大潮差和引入水体交换等情况,在港口海岸工程、海洋工程以及海水养殖等诸多领域具有广阔应用前景。对国内外浮式防波堤的主要研究成果和进展进行了综述,从理论推导、经验公式和数值计算3个方面归纳和总结了浮式防波堤波浪透射系数的计算方法。介绍了浮式防波堤结构型式的研究进展,重点分析了浮箱式、浮筒式、浮筏式及其相应改进结构等不同型式浮式防波堤的消浪原理和消浪效果,分析比较了不同结构型式浮式防波堤的优缺点。最后介绍了浮式防波堤在国内外的工程应用,并分析了限制浮式防波堤应用的主要原因,指出了目前浮式防波堤研究方面的不足,以及推广应用浮式防波堤需要进一步研究的内容。     

新型透空格栅板式防波堤消浪性能试验

为提高透空式防波堤的消浪效果,提出了一种新型透空格栅板式防波堤结构。通过水槽试验,分析了该防波堤的消波性能,探讨了上下层平板相对间距以及格栅板间隙比等参数对防波堤透射系数和反射系数的影响。结果表明,该结构防波堤消波性能良好,且防波堤出水状态下的消浪效果要好于淹没状态;随着相对板间距的增大,防波堤透射系数变小;上下层各格栅板间隙比为0.1时,防波堤的消波效果最佳。     

水平斜插板透空式防波堤消波性能数值模拟

通过改进已有的防波堤模型，建立了一种新型水平斜板透空式防波堤模型。基于VOF方法建立了波浪与水平斜板防波堤相互作用的数值模型。经数值模拟研究了该新型水平斜板防波堤结构对波浪透射系数的影响，主要考虑了斜板角度、波陡、相对板间距、相对板宽和相对出水高度等因素对防波堤消波效果的影响。模拟结果显示:①水平斜插板透空式防波堤比水平板透空式防波堤的消波效果好。在斜插板作用下，随着斜板角度增大，透射系数逐渐增大，但增幅逐渐减小；②随着波陡增大，透射系数先减后增；③随着水平板间距增加，透射系数增大；④随着防波堤相对板宽的增大，透射系数逐渐减小；⑤随着防波堤出水高度增加，透射系数先减后增。结果表明，该新型结构防波堤的消波效果显著，可以很好地消减波浪，应用前景良好。     

废旧轮胎在闸下消能防冲中的应用

为实现增加糙率降低近底流速的目的,用废旧轮胎制作海漫表面的加糙体。通过室内水工模型试验,对加糙轮胎的数量、布置形式、相对糙度等影响因素进行比较研究,得到利用废旧轮胎进行海漫加糙的最佳方案。试验结果表明,用废旧轮胎加糙可使近底流速降低50%。经现场原型试验,利用废旧轮胎加糙,闸下冲坑深度平均减少75.7%,冲坑面积减少19.3%,减冲效果明显。应用表明,利用废旧轮胎加糙减冲是切实可行的。     

废旧轮胎加筋土性能试验研究

为了研究废旧轮胎加筋对土体强度以及边坡稳定性的影响,采用室内试验,首先进行固结排水剪切三轴试验,研究了废旧轮胎加筋素砂土的应力-应变关系和土体抗剪强度指标变化规律;其次进行路堤模型试验,对比分析了土工格室单一加筋、废旧轮胎-土工格室复合加筋2种加筋形式对路堤边坡稳定性的影响效果差异。结果表明:轮胎加筋明显提高了土体抗剪性能,并且轮胎加筋层数越多,试样抵抗变形能力越好,强度越大;废旧轮胎-土工格室复合加筋优于土工格室单一加筋效果,能显著减少路基边坡沉降、侧向位移和附加应力峰值,有效改善路堤边坡稳定性。最后讨论了轮胎加筋与土工格室加筋机理的异同。试验研究结果为废旧轮胎加筋土应用于岩土工程的边坡稳定处理提供了理论基础。     

薄膜型LNG液舱中浮式制荡板的数值模拟研究

薄膜型液舱广泛用于FLNG(浮式液化天然气储存装置)、FSRU(浮式储存和再气化装置)和LNGC等LNG储运装置,液舱晃荡是目前国际上的一个重要的研究热点。晃荡会产生沿舱壁的爬高和冲击,各国研究人员相继提出了各类制荡措施,以确保液舱安全。该文根据港口工程中浮式防波堤的原理,提出在液舱壁面附近安装浮式制荡板的新设想。首先,针对日本学者提出的在液舱中部放置浮式制荡板的方案,建立带有浮式制荡板的二维液舱晃荡数学模型,并与其试验结果进行对比,验证了该数学模型的有效性;然后,采用该数学模型,对文中提出的方案,进行数值模拟和分析,探讨新型浮式制荡装置对制荡效果的影响,为下一步的结构优化和实船应用奠定基础。     

新型透空组合板式防波堤结构型式及消浪特性分析

为提高透空式防波堤的消浪性能并减小结构受力,在前人研究基础上提出了一种新型透空组合板式防波堤,比较分析了该型式的防波堤(模型c)与另外两种型式的防波堤(模型a和模型b)的结构特点。通过物理模型试验,探讨了模型c在不同影响因素下的消浪特性,并对比分析了模型a与模型c的透射系数、反射系数和能量耗散系数在不同相对堤宽下的变化关系,比较了两种模型的消浪效果。分析得出,由于模型c兼具开孔水平板式防波堤和开孔挡板式防波堤的作用,模型c的波浪反射小于模型a,消浪效果优于模型a,且模型c这种结构能有效减小防波堤结构受力;当模型宽度和相对间隙比同时较大时消浪效果更好,防波堤出水后的消浪性能要优于淹没状态下的防波堤。     

EXPERIMENTAL STUDY ON A NEW KIND OF OPEN TYPE BREAKWATERS

A new kind of open type breakwaters was proposed based on the concept of wave energy conversion. The excellent feature of the structure is that it can absorb and utilize the wave energy to dissipate waves. The effects of some factors, such as the configuration insides, the geometrical parameters and the relative width (the ratio of the width to the wave length), on the performance of the breakwater were discussed based on a series of regular wave tests in the wave flume. The hydrodynamic characteristics of the new open type breakwater were analyzed in detail, and the structure was optimized to improve the performance of the breakwater to effectively dissipate the waves with long period. The variation of the coefficients of wave transmission and reflection along with attenuation with respect to relative width was examined. The results of the physical model tests indicate that the transmission coefficient significantly decreases by about twenty percent at the range of relative width from 0. 1 to 0.2, compared with the traditional open type breakwaters.     

斜向随机波对直立堤作用的试验研究

通过斜向随机波对直立堤作用的试验，研究了作用在直立堤上的单位堤长波浪力随波浪入射角的变化．讨论了波浪力沿堤长的纵向分布，以及单元堤长对波浪力纵向折减的影响．给出了波浪力纵向分布系数和折减系数与相对堤长的关系式．     

Time-domain hydrodynamic analysis of pontoon-plate floating breakwater

The hydrodynamic behaviors of a floating breakwater consisting of a rectangular pontoon and horizontal plates are studied theoretically. The fluid motion is idealized as two-dimensional linear potential flow. The motions of the floating breakwater are assumed to be two-dimensional in sway, heave, and roll. The solution to the fluid motion is derived by transforming the governing differential equation into the integral equation on the boundary in time domain with the Green’s function method. The motion equations of the floating breakwater are established and solved with the fourth-order Runge-Kutta method to obtain the displacement and velocity of the breakwater. The mooring forces are computed with the static method. The computational results of the wave transmission coefficient, the motion responses, and the mooring forces of the pontoon-plate floating breakwater are given. It is indicated that the relative width of the pontoon is an important factor influencing the wave transmission coefficient of the floating breakwater. The transmission coefficient decreases obviously as the relative width of the pontoon increases. The horizontal plates help to reduce the wave transmission over the floating breakwater. The motion responses and the mooring forces of the pontoon-plate floating breakwater are less than those of the pontoon floating breakwater. The mooring force at the offshore side is larger than that at the onshore side.     

NUMERICAL SIMULATIONS OF NONLINEAR WAVE TRANSFORMATION AROUND WAVE-PERMEABLE STRUCTURE

1.INTRODUCTION Thedevelopmentofbreakwaterdesignmeth odologyoftenrequireaconditionofpermittingfor protectionofecosystem,itisalsoanalternativeto massivegravitybreakwatersinreductionofwave transmissioninshallowwater.Thetheoreticalso lutionsofwavepermeablebreakwatersdiversified indifferentexpressionsoftheenergydamping term,duetolaminarandturbulentflowintheper meablestructures.Theporositysolution[1]isbased onatrialmethod,andanumberofauthorssolve theproblembydifferentnumericalapproach[27].Inpre…     

ANALYTICAL RESEARCH ON THE WAVE DIFFRACTION OF ARC-SHAPED FLOATING BREAKWATERS

1. INTRODUCTIONBreakwaters are generally constructed for thedissipation and reflection of incident wave energyin order to decrease the wave height to protect thecoast against the erosion and to decrease the forceacting on the coastal structures . Compared…     

Wave characteristics of Bragg reflections from a train of submerged bottom breakwaters

The wave characteristics of Bragg reflections for a train of surface water waves from a series of submerged bottom breakwaters were investigated numerically. A numerical model based on boundary discretization technique was developed to calculate the wave field. The computational results were validated by comparing with analytical solutions in the literature. The wave fields induced by two types of bottom breakwaters in the shapes of rectangular and trapezoidal with various formations of the breakwater trains were simulated to study the wave characteristics. Variables investigated included the number of the breakwaters in the train, the height and width of the breakwaters, and the side slope of the trapezoidal breakwaters. Certain notions with regard to the application of shoreline protections were addressed based on the results.