斜坡堤天然块石护脚的稳定性计算

试验研究表明 ,不规则波对斜坡堤护脚棱体稳定性的威胁大于波高对应于Hs 的规则波 ,斜坡堤护面形式对护脚块石的稳定也有影响。Gerding公式虽然准确地描述了棱体在波浪作用下的稳定性规律 ,但由于护面糙率、透水率等因素的影响在工程上应用仍需进一步修正。文章指出在中低水位 ,Gerding公式计算的护脚棱体稳定重量有可能偏小 ,并给出了不同类型护面下护脚棱体稳定计算的修正系数     

堆石防波堤不规则波浪反射系数试验研究

结合物理模型试验,分析斜坡坡度、波陡、相对水深、护面类型和破波参数等因素对堆石防波堤不规则波浪反射系数的影响规律。将常用的Van der Meer公式,Seelig公式,Postma公式和Davison公式计算值和实测值进行比较,并结合试验数据,基于有效波高和平均周期定义的Iribarren数,得出堆石防波堤不规则波浪反射系数经验公式。结果表明,该公式能较好地计算不规则波作用下块石和扭王块体护面堆石防波堤波浪反射系数。     

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。     

Numerical analysis of wave overtopping of rubble mound breakwaters

The paper describes the results of a two-dimensional (2-D) numerical modelling investigation of the functionality of rubble mound breakwaters with special attention focused on wave overtopping processes. The model, COBRAS-UC, is a new version of the COBRAS (Cornell Breaking Waves and Structures) based on the Volume Averaged Reynolds Average Navier–Stokes (VARANS) equations and uses a Volume of Fluid Technique (VOF) method to capture the free surface. The nature of the model equations and solving technique provides a means to simulate wave reflection, run-up, wave breaking on the slope, transmission through rubble mounds, overtopping and agitation at the protected side due to the combined effect of wave transmission and overtopping. Also, two-dimensional experimental studies are carried out to investigate the performance of the model. The computations of the free surface and pressure time series and spectra under regular and irregular waves, are compared with the experimental data reaching a very good agreement. The model is also used to reproduce instantaneous and average wave overtopping discharge. Comparisons with existing semi-empirical formulae and experimental data show a very good performance. The present model is expected to become in the near future an excellent tool for practical applications.     

Three-dimensional investigations of wave overtopping on rubble mound structures

To study the influence of wave obliquity and directional spreading on wave overtopping of rubble mound breakwaters a total of 736 three-dimensional model tests were carried out at Aalborg University. The results of these tests are presented and analysed in this paper yielding a new empirical reduction factor to describe the influence of wave obliquity and directional spreading on the average wave overtopping discharges. The study shows that perpendicularly incident, long-crested waves result in conservative values of the overtopping discharge for the tested cross-section.     

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。     

Theoretical and experimental study on wave damping inside a rubble mound breakwater

Wave decay in a rubble mound breakwater has been analysed theoretically for various types of damping functions (linear, quadratic and polynomial). The applicability of these damping functions for wave decay in the landward part of the breakwater core has been investigated in large scale model tests. The properties of the rock materials that have been used in the model tests have been determined to provide a rational basis for the damping coefficients. The analysis is based on detailed measurements of wave conditions and pressure distributions inside the breakwater. The theoretical approaches have been validated and where necessary extended by empirical means. The wave decay inside the breakwater can be reasonably approximated by the commonly applied linear damping model (resulting in exponential wave height attenuation). An extended polynomial approach provides a slightly better fit to the experimental results and reflects more clearly the governing physical processes inside the structure.     

Rock stability of rubble mound breakwaters with a berm

Breakwaters with a berm can significantly reduce overtopping and reduce the required rock size compared to straight slopes without a berm. Here, the stability of rock slopes with a horizontal berm has been studied by means of physical model tests to provide information on the required rock size. The tests and analysis are focussed on the slope above the berm as well as the slope below the berm. Also the stability of the rock at the berm is addressed. The influence of the slope angle (1:2 and 1:4), the width of the berm, the level of the berm, and the wave steepness has been investigated. Based on the test results prediction formulae have been derived to quantify the required rock size for rubble mound breakwaters with a berm. Especially for the slope above the berm, the rock size can be reduced significantly compared to straight slopes.     

明基床上开孔沉箱垂直力峰值对应的水平力分析

利用水槽二维物理模型对规则波及不规则波作用下明基床上开孔沉箱所受到的波浪力进行了较为系统的试验研究。分析了开孔沉箱总垂直力峰值时刻对应的总水平力与相对基床高度、消浪室相对宽度、波陡、相对水深以及开孔率等影响因素之间的关系,给出了明基床上开孔沉箱总水平力比值(总垂直力峰值时刻对应的总水平力/总水平力峰值)与各影响因素之间的计算关系式。研究成果可供实际工程参考应用。     

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。     

开孔率对明基床上开孔沉箱波浪反射系数影响的数值研究

开孔率是开孔沉箱波浪反射系数的重要影响因素,迄今为止关于开孔沉箱的物模试验研究成果(包括《防波堤设计与施工规范》)中,开孔率μ通常以线性关系反映在开孔沉箱波浪反射系数的计算关系式中,适用范围为0.2~0.4。但当μ0.2或μ0.4时,开孔率μ对波浪反射系数Kr的影响规律尚需进一步的研究探讨。现借助二维数值波浪水槽,在扩大了的开孔率取值范围内,模拟不规则波与可渗明基床上开孔沉箱的相互作用。结果表明:在0.2≤μ≤0.4的范围内,用线性关系描述开孔率μ对波浪反射系数Kr的影响是合适的;在μ0.4时,数模值和物模试验拟合的经验关系式的趋势是一致的;在μ0.2时,开孔沉箱反射系数K_r随开孔率μ的减小而增大,用物模试验拟合的经验关系式及《防波堤设计与施工规范》中计算公式的线性关系来描述开孔率μ对反射系数K_r的影响是不恰当的。研究成果对开孔沉箱消浪机理的深入认识和开孔沉箱结构的优化设计具有重要意义。     

A two-point method for estimating wave reflection over a sloping beach

This work presents a frequency-domain method for estimating incident and reflected waves when normally incident waves’ propagating over a sloping beach in a wave flume is considered. Linear wave shoaling is applied to determine changes of the wave amplitude and phase due to variations of the bathymetry. The wave reflection coefficient is estimated using wave heights measured at two fixed wave gauges with a distance. The present model demonstrates a high capacity of estimating reflection and shoaling coefficients from synthetic wave-amplitude data. Sensitivity tests for the present model due to measurement errors of wave amplitudes and distance of two probes can more accurately predict the reflection coefficients. The measurement error of wave amplitude affects more significantly than measurement error of distance of two probes on calculating reflection coefficient of waves over a sloping bed.     

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。     

空间节省型堰式沉箱波浪反射与结构优化试验研究

为了同时提升消浪效果和节省海岸空间,对低反射防波堤进行改进,提出了一种空间节省型堰式沉箱结构。通过物理模型试验研究了堰式沉箱在规则波作用下的消能机理,然后采用单因子分析法分析了相对淹没深度、波陡和相对波高对反射系数的影响,并且利用SPSS软件对无因次参数进行非线性回归分析得到了反射系数计算公式。结果表明,内堰消浪室可以形成良好的波能耗散机制,随着有效消浪室个数的增多,消浪效果逐渐增强,使得反射系数的最小值和最大值较非透空直立结构分别降低了60%～90%和10%～30%。基于以上研究成果,给出关于特征水位与内堰的相对位置关系的合理建议,并总结了堰式沉箱结构的优化设计要点,对实际工程应用具有一定的指导意义。     

Effect of perforations and rubble mound height on wave transformation characteristics of surface piercing semicircular breakwaters

The present study investigated how the perforations, water depth and rubble mound height on fully perforated semicircular breakwater (SBW) affects non-breaking wave transformations. SBW model with surface piercing condition for three different perforation ratios with 7 percentage, 11 percentage and 17 percentage were considered to study the variation of reflection, transmission, run-up characteristics and dimensionless horizontal and vertical forces as a function of relative water depth and the results are compared with an impermeable SBW and seaside perforated SBW models. From the results it is understood that, SBW with perforation ratio 17 percentage in the case of seaside perforated case shows reverse trend in hydrodynamic characteristics and for fully perforated SBW, it transmits large amount of wave energy on the seaside, which affects the tranquillity condition in the harbour. In addition, transmission characteristics of SBW models and conventional rubble mound breakwater model are compared to understand the effect of composite breakwater action and also the reflection characteristics of SBW models are compared with field data of Miyazaki Port after Sasajima et al. (1994). The results reveal that the SBW model with perforation ratio of 11 percentage in seaside and fully perforated type gives an optimum performance in terms of energy dissipation and transmission.     

中长周期波作用下的斜坡堤胸墙波浪力试验研究

在印度洋、大西洋沿岸,海岸工程设计波浪周期多在14 s以上,具有显著的中长周期波特征。通过以往工程项目的试验结果发现中长周期波下,规范计算的斜坡堤胸墙波浪力明显小于试验结果。因此,通过系列物理模型试验研究了中长周期波下的斜坡堤胸墙波浪力。分析斜坡坡度、肩台宽度和波浪条件对胸墙波浪力的影响。通过将试验结果与我国现有规范中的经验公式计算所得结果进行对比,发现规范更适用于胸墙底淹没的情况,而对于肩台出水情况,规范计算结果小于试验结果。由此提出了一种新的波浪力计算方法,计算准确度得到明显提高。     

Field measurements of wave overtopping at the rubble mound breakwater of Rome–Ostia yacht harbour

This paper describes a new station for full-scale measurement of wave overtopping at the Rome yacht harbour rubble mound breakwater in Ostia (Italy) and the results of the successful first measurement campaign carried out during the winter season 2003–2004. The equipment and the research activities were supported by the EU project CLASH, focusing on scale effects for wave overtopping at coastal structures. The site is characterized by a very small tidal range, a long shallow foreshore and depth-limited breaking waves which interact with a shallow sloping porous rock structure. Overtopping water is collected by a steel tank installed on the crown slab behind the parapet wall. The measurement of water level variation inside the tank by means of two pressure transducers allows the calculation of individual overtopping volumes. Incident waves, sea levels and wind are also measured. During seven independent storms, more than 400 individual overtopping events were recorded and about 86 h of valid data are available. This extensive dataset is presented, discussed and then used for comparison with two commonly used overtopping prediction formulae based on small-scale model tests showing their tendency to underestimate the prototype results. A strong correlation between the hourly mean overtopping discharge and corresponding maximum volume is also presented. The paper generally confirms the validity of the approach used in Troch et al. (2004) [Troch, P., Geeraets, J., Van de Walle, B., De Rouck, J., Van Damme, L., Allsop, W., Franco, L., 2004. Full-scale wave overtopping measurements on the Zeebrugge rubble mound breakwater. Coastal Engineering 51, 609–628] for field measurement of wave overtopping.     

Experimental study of reflection coefficient and wave forces acting on perforated caisson

The reflection coefficient and the total horizontal forces of regular waves acting on theperforated caisson are experimentally investigated. The empirical relationship between reflection coefficient and the ratio of the total horizontal forces acting on the perforated caisson to those on solid vertical walls with the relative chamber width, relative water depth and porosity of perforated wall, etc. are given. Moreover, the results of the ratio of the total horizontal forces are also compared with formulas given by Chinese Harbour Design Criteria and Takahashi, which may be useful for the practical engineering application.     

Impedance analysis of hydrodynamic behaviors for a perforated-wall caisson breakwater under regular wave orthogonal attack

An impedance analytical method (IAM) is developed to study the interaction between regular waves and a perforated-wall caisson breakwater that consists of a front perforated-wall and a chamber with a rigid impermeable back wall. The boundary conditions at the perforated-wall are established in terms of the flow resistances of the fluid passing through the holes. As a result, explicit algebraic expressions are obtained for reflection coefficients and wave loads. In the formulae, all of the parameters are known a priori. The predicted reflection coefficients and the wave forces are compared with the experimental data of other authors.