共查询到20条相似文献，搜索用时 109 毫秒
1.
海岸带边坡防浪林消浪理论与实验研究 总被引：5，自引：0，他引：5
在海岸边坡上种植防浪林是一种新的护岸形式,应用理论分析和模型实验对其进行了初步研究.建立波浪在斜坡上传播的控制方程及边界条件,应用摄动理论求解非线性解,得到了一阶精确解和二阶近似解.在模型实验中,确定几何比尺为 1∶10,选取桧柏树枝作为防浪林模型,根据量纲分析,确定的主要影响因素是海岸边坡坡度、波高、波周期、水深与防浪林树宽.实验结果表明,防浪林宽度与岸坡坡度对消浪效果影响较大. 相似文献
2.
互花米草及其对海岸的防护作用 总被引：28，自引：0，他引：28
本文论述了互花米草在滩涂中种植的时间、种植的方法及其生长的适应性。文中着重讨论互花米草在海岸工程中防浪和消浪能力。与工程护岸比较，互花米草护岸是最经济、合理和有效的。通过本文的讨论为今后利用互花米草进行海岸防护提供依据 相似文献
3.
为合理确定防浪建筑物的越浪量,基于含非静水压力梯度项的非线性浅水方程建立了近岸波浪越浪数值模型。通过采用域内造波、消波并结合波前静压假定的破碎模型,模拟了规则波和不规则波在斜坡上的波浪传播变形,并在此基础上进行了越浪量数值计算。数值计算结果与物理模型实验结果表明,非静压模型可合理地描述波浪破碎点位置、破碎后的波高、增减水以及斜坡上的堤后越浪量。数值模型具有较高的计算精度和计算效率,可为实际工程防浪建筑物越浪以及堤顶高程的设计提供一种新的数值研究手段。 相似文献
4.
5.
近岸植物带能有效削弱波浪作用,植物带消浪影响因素分析对布置护岸工程、维护岸线稳定有重要意义。在模型实验基础上,探究相对波高、模型相对宽度、模型相对高度和体积分数对透射系数的影响。设置波浪水槽试验,研究孤立波在不同水深、入射波高及植物排布方式等组合条件下对植物消浪效果的影响。采用遗传编程法得出各复杂度下的透射系数计算公式,并分析各参数在方程中的表现情况,发现遗传编程能定性给出参数的敏感度。相比于非线性回归拟合结果,遗传编程方法得到的函数关系更加精确。采用人工神经网络方法进一步分析与验证各影响因素对植物消浪效果的影响程度,结果表明人工神经网络得出的结果与遗传编程方法相近,体积分数对消浪效果起主导作用。 相似文献
6.
分层斜坡越浪式波能发电装置作为一种重要的波能转换型式,在开发利用波浪能的同时,可与防波堤或护岸工程相结合,将海岸工程的被动消能变为主动吸能,提高综合效益。在实际工程应用中,分层斜坡越浪式发电装置引浪面在波浪荷载作用下的安全性成为首要问题,由于其引浪面与防波堤或护岸的护面对水体磨阻影响不同,因此水体对结构的作用力不同,已有的斜坡式防波堤所受波浪荷载的研究无法用于指导分层斜坡越浪式发电装置引浪面的结构强度设计。通过水工物理模型试验,对分层越浪装置引浪面在不同波况条件下的结构受力进行研究分析,获得越浪装置引浪面上点压力及波浪力的分布规律,为装置的结构设计提供理论指导及设计支持。 相似文献
7.
在多个实际工程的模型试验及专题研究的基础上,本文对斜坡式防浪堤上一种墙顶设有挑浪嘴、墙底设有前齿的“L”形胸墙的若干问题进行了小结。文中,对越浪量估算和堤顶标高的合理确定、挑浪嘴和墙底前齿的机理及其效应、作用于墙上的波压力、胸墙断面的优化设计方法等作了全面的阐述。 相似文献
8.
轻型连续沉井在护岸工程中的应用 总被引：1，自引：0，他引：1
结合青岛浮山湾北海船厂西护岸工程，对轻型连续沉井在护岸工程中的应用作了系统介绍。连续沉井在该工程的软基上作为干插条石斜坡堤的堤脚支撑并兼有护底防冲刷以及消浪功能，具有施工方便，造价经济，美观实用等优点，有一定的推广使用价值．对该类轻型沉井的设计和施工作了较为详细的阐述，便于工程应用。 相似文献
9.
在实际的海堤等工程中常用堤前抛石消浪减少爬高或越浪量,但结果有时适得其反。本文通过直立堤堤前抛石对越浪量影响试验,明确提出堤前抛石消浪的适用范围和估算越浪量的经验关系式,并提出平台上抛石消浪的新设想。 相似文献
10.
11.
12.
Verification tests of linear wave propagation models for cases of waves propagating through a refractive focus typically overpredict peak amplitudes in the vicinity of the focus. Using a parabolic equation model for the combined refraction-diffraction of weakly-nonlinear waves [valid for Ursell number Ur < O(1)], we show that, in a particular experiment, much of the discrepancy between laboratory measurements and linear wave model predictions can be accounted for by including the effect of nonlinearity, which is important in the region of the focus. 相似文献
13.
In 1995, Suh and Park developed a numerical model that computes the reflection of regular waves from a fully perforated-wall caisson breakwater. This paper describes how to apply this model to a partially perforated-wall caisson and irregular waves. To examine the performance of the model, existing experimental data are used for regular waves, while a laboratory experiment is conducted in this study for irregular waves. The numerical model based on a linear wave theory tends to over-predict the reflection coefficient of regular waves as the wave nonlinearity increases, but such an over-prediction is not observed in the case of irregular waves. For both regular and irregular waves, the numerical model slightly over- and under-predicts the reflection coefficients at larger and smaller values, respectively, because the model neglects the evanescent waves near the breakwater. 相似文献
14.
Water waves propagating over a layer of soft mud or submerged aquatic vegetation can drastically attenuate over distances comparable to several wave lengths. The attenuation in the case of mud has been found previously to be reasonably described by an exponential decay. Waves reflect from beaches and any structures that they impact. The reflected waves affect wave heights measured in the field or laboratory wave basins.Decomposition of small amplitude waves into incident and reflected waves is a linear problem. However, the presence of the exponential damping introduces nonlinearity to the decomposition problem and requires an iterative process for solving the problem. Despite considerable experimental research on attenuation of waves over mud, none of the existing methods for decomposition of incident and reflected waves have accounted for this case.Here, the Newton Algorithm was used to account for the effect of wave decay over mud by quasi-linearizing the nonlinear equations. Also, a second method using a new error function and a commercial nonlinear solver was proposed in both time and frequency domain. The performance of both methods has been verified using artificial as well as laboratory data. 相似文献
15.
Macrofauna along the Sudanese Red Sea coast: potential effect of mangrove clearance on community and trophic structure 
下载免费PDF全文
下载免费PDF全文 Mangroves along the Sudanese Red Sea coast are under constant anthropogenic pressure. To better understand the influence of mangrove clearance on the intertidal benthic community, we investigated the composition, biodiversity and standing stock of the macrofauna communities at high‐, mid‐ and low‐water levels in three contrasting habitats: a bare sand flat, a cleared mangrove and an intact mangrove. In addition, a community‐wide metric approach based on taxon‐specific carbon and nitrogen isotope values was used to compare the trophic structure between the three habitats. The habitats differed significantly in terms of macrofaunal standing stock, community composition and trophic structure. The high‐ and mid‐water levels of the intact mangroves showed a distinct macrofaunal community characterized by elevated densities and biomass, largely governed by higher decapod and gastropod abundances. Diversity was similar for cleared and intact mangroves, but much lower for the bare sand flat. Community‐wide metrics indicated highest trophic diversity and community niche breadth in the intact mangroves. Differences between the cleared and intact mangroves can be partly attributed to differences in sediment characteristics resulting from mangrove clearance. These results suggest a significant impact of mangrove clearance on the macrofaunal community and trophic structure. This study calls for further investigations and management actions to protect and restore these habitats, and ensure the survival of this ecologically valuable coastal ecosystem. 相似文献
16.
Shallow soft-bottom habitats including mangroves and mudflats provide important nursery functions for juvenile fishes, but little information exists concerning the relative nursery value of these habitats for juvenile fishes. We compared the potential of a mangrove and a mudflat in a semi-enclosed bay in Hong Kong to serve as fish nurseries by measuring species composition, dietary composition, gut fullness and diet breadth of juvenile fishes. Fish abundance was higher in mangrove than mudflat, but species richness was almost similar between the two habitats. After excluding Ambassis gymnocephalus, which was found mainly in the mangrove, difference in fish abundance between the two habitats was small. The gut fullness and diet breath of most species did not differ between mangrove and mudflat, suggesting that the two habitats were very similar in terms of providing feeding opportunity for juvenile fishes. While the importance of mangrove as nursery of fishes has been repeatedly emphasized, our data suggest that other soft-bottom habitats, such as mudflats, are also important and need to be protected. 相似文献
17.
Implementation and evaluation of alternative wave breaking formulas in a coastal spectral wave model 总被引：2，自引：0，他引：2
This paper describes methods and results of research for incorporating four different parameterized wave breaking and dissipation formulas in a coastal wave prediction model. Two formulations assume the breaking energy dissipation to be limited by the Rayleigh distribution, whereas the other two represent the breaking wave energy by a bore model. These four formulations have been implemented in WABED, a directional spectral wave model based on the wave action balance equation with diffraction, reflection, and wave–current interaction capabilities. Four parameterized wave breaking formulations are evaluated in the present study using two high-quality laboratory data sets. The first data set is from a wave transformation experiment at an idealized inlet entrance, representing four incident irregular waves in a slack tide and two steady-state ebb current conditions. The second data set is from a laboratory study of wave propagation over a complex bathymetry with strong wave-induced currents. Numerical simulation results show that with a proper breaking formulation the wave model can reproduce laboratory data for waves propagating over idealized or complicated bathymetries with ambient currents. The extended Goda wave breaking formulation with a truncated Rayleigh distribution, and the Battjes and Janssen formulation with a bore model produced the best agreement between model and data. 相似文献
18.
盐度对镭同位素在海南红树林沉积物解吸行为的影响 总被引：1，自引：0，他引：1
天然放射性镭同位素在沉积物上的解吸行为是影响其在陆-海交换过程中的关键所在。采用沉积物室内解吸实验和现场采集间隙水测量224Ra含量两种方法,对水体盐度梯度控制镭在海南八门湾红树林沉积物的解吸行为进行了讨论。结果表明:沉积物上可交换态224Ra的最大量为0.44dpm/g,解吸比为35%。利用间隙水的224Ra含量确定镭的分配比Kd与水体盐度S呈反比例函数:Kd=8.4×102/S,与室内解吸实验的结果相比更能代表镭在沉积物上的真实解吸行为。在深度25—40cm内,湿地沉积物的224Ra处于与其母体228Th的平衡状态,但223Ra很可能处于相对其母体227Th亏损状态。 相似文献
19.
In this paper, a multi-channel structure was developed to attenuate waves with various wave periods. By ignoring energy losses and the factor of channel width, a simple and straightforward method was used to tackle this problem. The theoretical solution showed that a single reflected channel structure could attenuate waves of a certain wave period, while a multi-channel structure could attenuate waves with various wave periods. If an interval of 0.05<relative water depth<0.15 is concerned, a structure consisting of four reflected channels could provide a transmission coefficient of less than 0.2. Experimental tests were conducted to verify the theoretical solutions. Both theoretical solution and experimental data indicated that waves with various wave periods would be effectively attenuated after passing through the multi-channel structure. Although some factors are neglected in treating this problem, the method is applicable. An allowed transmission coefficient can be provided by a multi-channel structure only if the computed peak value is not larger than that value. 相似文献
20.
内波场中水平桩柱波阻的实验研究 总被引：3，自引：0，他引：3
分析水平阻力与内波波要素的关系,采用实验室实验的方法,研究了水平桩柱与内波的相互作用,焦点是研究内波波要素与波阻之间的关系。实验中的密度分层采用典型跃层型剖面,而内波是由自行研制的造波机生成。实验结果表明,当内波的频率不变时,水平桩柱所受到的阻力随着内波的振幅增加而增加,它的量值与分层有关。对于强跃层的密度分布,当桩柱处在跃层中时,受到的水平波阻较小,而在跃层之外则受到较大的水平波阻。 相似文献