共查询到18条相似文献，搜索用时 203 毫秒
1.
开发建立了近岸波生流运动三维数值计算模式。模式中,引入了三维时均剩余动量、破波表面水滚、波浪水平与垂向紊动作为主要驱动力,同时考虑了波流共同作用的底部剪切力。推导了可综合反映底坡、能量传递率和密度影响的水滚能量传输方程;将Larson-Kraus的二维波浪水平紊动系数表达式拓展至三维。采用大量实测数据和文献资料测试验证了所建模式,表明所建模式可有效模拟波浪增减水、底部离岸流、沿岸流、裂流、堤后环流等不同维度的波生流现象。此外,研究也表明破波水滚效应可解释波生流峰值向岸推移的物理现象,从而在模拟中不能忽略;破波带内沿岸流速垂向较为均匀的现象与波浪附加垂向紊动有关。 相似文献
2.
提出一种基于完全非线性Boussinesq方程的改进波浪破碎模型,用于模拟近岸浅水波浪破碎.模型借助水滚的概念,提出一种确定k方程紊动模式中紊动源项的计算公式,通过解k方程计算Boussinesq方程中的涡黏系数,实现对破碎波的模拟.岸边界采用窄缝法,使得模型可用于波浪爬坡的计算.用实验室实测波高和增减水资料对模型进行了验证,得到了一致的结果.紊动源、紊动动能以及紊动耗散率的计算结果表明:①在破波点处紊动源项值最大,随着波浪向岸边传播,逐渐减小;②破波点处,水平方向的对流和扩散在紊动能量输移中发挥重要作用;③岸边附近紊动源与紊动耗散接近平衡. 相似文献
3.
波浪增水抬升了岸礁礁坪的平均水位,对岸礁后方陆域安全有重要影响。通过水槽试验,研究了不规则波况下岸礁礁坪的增水。试验组次为3种礁坪水深、4种有效波高和4种谱峰周期的组合。试验结果表明:①岸礁地形上的波浪要素需至少统计200个波才能达到稳定;②不规则波列在岸礁上破碎过程比规则波列复杂,同一波列中波高较大的波以卷破形式在礁前斜坡上破碎,波高较小的波以崩破形式在礁坪上破碎或者不破碎;③礁坪上最大增水值随入射波周期的增大而增大、随礁坪水深的增大而减小,并与入射波波高呈正比。结合试验数据,发现基于规则波试验得出的Gourlay礁坪增水公式,在使用有效波高和谱峰周期作为代表波要素时,公式能良好地预测不规则波在岸礁礁坪上的最大增水值。 相似文献
4.
为了更好地研究近岸海域波生沿岸流,建立了基于高阶Boussinesq水波方程的波生沿岸流时域数值模型。控制方程在中等水深范围内具有较好的色散性和变浅作用性能,同时具有二阶完全非线性特征,适合描述近岸区域波浪强非线性运动。通过采用松弛造波方法实现了非线性波浪的无反射入射,采用周期性侧边界条件模拟开敞边界。通过数值试验,讨论了模型中主要参数对数值结果的影响。利用率定后的参数模拟了均匀坡度海岸上产生的沿岸流,通过和实验数据的对比验证了模型的准确性和适用性。利用模型数值模拟了不同波浪入射条件(包括周期、波高和波浪入射角度)对波生沿岸流的影响。 相似文献
5.
波浪破碎是海岸工程所关注的关键水动力学问题之一,而波浪破碎的数值模拟技术的研究方兴未艾。高效的浅水方程基于静压假定,而通过引入动压项建立的完全非静压模型,可成功应用于色散水波的模拟。自由表面的捕捉采用的垂向坐标变换技术,较之VOF（Volume of Fluid）模型,计算效率较高。但垂向坐标变换不能模拟大曲率自由表面变形,即波浪破碎过程。对于破碎波的模拟,一种高效的模式分裂法应用至非静压模型,即在波浪破碎局部水域将模型分裂为静压模型和非静压模型,破碎波波峰附近退化至静压模型,并持续至波浪破碎结束再恢复为动压模型。通过典型算例,验证了模式分裂法的适用性及对于波浪破碎过程的模拟精度,鉴于模式分裂法对于波浪破碎过程的模拟未引入新的概化模型,计算效率较高,可应用于大尺度的海岸带波浪的变形、破碎及越浪的数值模拟。 相似文献
6.
针对带礁缘的复坡珊瑚礁地形,开展4组礁坪水位条件下、不同入射波高和波周期相组合的系列组次规则波试验,分析波高和增水的沿礁变化过程,研究深水波高、波周期和环境水位对破碎波高、破碎位置、礁坪增水和传递波高的影响规律,拟合给出试验地形下的参数化公式。研究表明:破碎波高和破碎位置随深水波高和波周期的增大而增大,受礁坪水位的影响相对较小;礁坪增水和传递波高受礁坪水位的影响较大,增水随水位的抬升而减小,传递波高随水位的抬升而增大;破碎波高和深水波高的比值与深水波陡相关;传递波高和深水波高的比值与礁坪水深深水波高比相关;量纲一破碎位置（破碎点至礁边的水平距离与礁边处浅水波长的比值）及量纲一礁坪增水（礁坪增水和深水波高的比值）均可通过礁边水深与深水波高比建立参数化公式。 相似文献
7.
基于波作用量守恒方程建立了波流共存场中多向随机波浪传播变形数学模型,模型中考虑了波浪绕射的影响和水流引起的波浪弥散多普勒效应,应用包含水流和地形影响的激破波模式计算波浪破碎的能量耗散,采用一阶上迎风有限差分格式离散控制方程。分别计算了有无近岸流情况下单向和多向随机波浪的波高分布,考虑水流影响的数值计算结果与物理模型实验数据吻合良好,比较分析表明,所建立的数学模型能够复演由于离岸流引起的波高增大,可用于波流共存场多向随机波浪传播变形的模拟和预报。 相似文献
8.
钙质砂抗剪强度特性的环剪试验 总被引：2，自引：0，他引：2
珊瑚礁沉积的钙质砂与石英砂的物理力学性质有较大差别。对取自南海岛礁的钙质砂进行了单次往返环剪试验以分析钙质砂的抗剪强度特性,试验中考虑了相对密实度和竖向应力对结果的影响,并与相同级配和试验条件下的石英砂进行对比分析。结果表明：钙质砂正向剪切时应力-位移曲线为软化型,具有明显的残余强度特性,而反向剪切时则表现为硬化型,正向和反向剪切强度基本一致;石英砂正向剪切和反向剪切均表现为软化型。钙质砂正向剪切和反向剪切残余强度与峰值强度的比值在0.75～0.93之间;石英砂正向剪切和反向剪切残余强度与对应峰值强度的比值在0.89～0.96之间。相同级配和试验条件下,钙质砂残余强度均大于石英砂,且强度比值基本保持在1.05～1.3之间。在100、200 kPa竖向荷载作用下,钙质砂0.5～2.0 mm的颗粒发生了破碎,破碎率分别为4%和6%。 相似文献
9.
建立了波浪、底部离岸流、泥沙运动和沙滩剖面演变耦合数学模型,模拟了实验室中波浪作用下沙坝剖面的形成过程,讨论了各个物理参数对剖面上的水动力和地形变化的影响。通过参数率定,较好地复演了不规则波作用下沙滩地形由均匀斜坡向沙坝剖面的演变,波高、底部离岸流、输沙率和剖面演变的计算结果与实测数据吻合良好。采用数值实验和误差分析方法,讨论了破碎波水滚倾角、泥沙扩散系数和床面休止角等物理参数对计算结果的影响。研究表明,所建立的模型能较好地描述波浪作用下沙坝剖面形成过程中的重要物理机制。 相似文献
10.
河流、波浪和潮汐混合作用过程是当前沉积学的热点问题。通过梳理三角洲与其他一些海（湖）陆过渡沉积体系中关于河流—波浪、河流—潮汐、波浪—潮汐和河流—波浪—潮汐相互作用的相关研究,归纳总结了目前几种沉积过程的相互作用以及相应的沉积特征。河流和波浪的相互作用一般发生在河口附近,两者的相对强度以及波浪入射方向共同控制三角洲的形态和沉积物分布。长期的河流和波浪共同作用能够形成非对称性三角洲以及浪控复合斜坡型三角洲。河流和潮汐的相互作用通常发生在强潮汐或中潮汐区域的三角洲或河口湾的河流—海洋过渡带;随着相对海平面升降、沉积物供给变化和气候变化等因素的影响,潮汐和河流相互作用的三角洲和河口湾沉积体系经常反复叠加发育。潮汐和波浪的相互作用主要体现在潮汐不仅直接控制沉积物的沉积过程,而且间接性地移动波浪带进而影响相应的沉积相带。尽管目前河流、波浪、潮汐混合作用过程已经有一定程度的研究,但无论是短期小尺度的相互作用过程,还是长期受宏观因素（包括沉积物供给、海平面升降、构造沉降等）影响下的相互作用与演化过程,均有待进一步研究。 相似文献
11.
磨刀门已由"径流型"向"径流-波浪型"河口转变,波浪已是该河口主要动力之一,但波浪对河口洪季水流及泄洪的影响缺少研究。在2-D潮流数学模型中添加随潮位实时变化的波浪辐射应力,建立波浪潮流耦合数学模型;波浪求解采用缓坡方程,背景水深由潮流模型实时提供,可通过比较考虑和未考虑波浪影响的河口流场来分析波浪对泄洪的影响。在年均常浪作用下,磨刀门河口洪季涨落潮阶段均有明显的波生环流结构。由于波浪作用方向向陆,波生流减弱了浅滩区的向海余流,增大了浅滩向陆余流;受浅滩向海余流减弱影响,河口动力自调整后形成归槽水流,促使深槽内向海余流增大。波浪有顶托河口泄洪之势,可改变滩槽泄洪分配比例;年均常浪的波高较小,其对潮流及泄洪的影响区域限制在浅水区,故对泄洪的负面影响有限。 相似文献
12.
The tsunami of 2004 in the Indian Ocean transported thousands of meters-long boulders shoreward at Pakarang Cape, Thailand. We investigated size, position and long axis orientation of 467 boulders at the cape. Most of boulders found at the cape are well rounded, ellipsoid in shape, without sharp broken edges. They were fragments of reef rocks and their sizes were estimated to be < 14m3 (22.7t). The distribution pattern and orientation of long axis of boulders reflect the inundation pattern and behavior of the tsunami waves. It was found that there is no clear evidence indicating monotonous fine/coarse shoreward trends of these boulders along each transect line. On the other hand, the large boulders were deposited repeatedly along the three arcuate lines at the intertidal zone with a spacing of approximately 136m interval. This distribution pattern may suggest that long-lasting oscillatory flows might have repositioned the boulders and separated the big ones from small. No boulders were found on land, indicating that the hydraulic force of the tsunami wave rapidly dissipated on reaching the land due to the higher bottom friction and the presence of a steep slope. We further conducted numerical calculation of tsunami inundation at Pakarang Cape. According to the calculation, the sea receded and the major part of the tidal bench (area with boulders at present) was exposed above the sea surface before the arrival of the first tsunami wave. The first tsunami wave arrived at the cape from west to east at approximately 130min after the tsunami generation, and then inundated inlands. Our calculation shows that tsunami wave was focused around the offshore by a small cove at the reef edge and spread afterwards in a fan-like shape on the tidal bench. The critical wave velocities necessary to move the largest and average-size boulders by sliding can be estimated to be approximately 3.2 and 2.0m/s, respectively. The numerical result indicates that the maximum current velocity of the first tsunami wave was estimated to be from 8 to 15m/s between the reef edge and approximately 500m further offshore. This range is large enough for moving even the largest boulder shoreward. These suggest that the tsunami waves that were directed eastward, struck the reef rocks and coral colonies, originally located on the shallow sea bottom near the reef edge, and detached and transported the boulders shoreward. 相似文献
13.
从以物理模型实验及理论解析为代表的植物消波研究手段与宏观和微观尺度下植物消波分析方法两个方面总结了国内外的研究现状和最新研究进展。对物理模型实验中的植物因子、水动力因子、植物模型制作和实验布置等要素以及理论解析模型进行归纳,分别阐述了以波高衰减和波能耗散为主要分析对象的植物消波分析方法,指出现有物理模型实验中植物几何比尺与波要素比尺难以统一和理论解析研究局限于二维情况等问题。综合考虑季节更替、植物摆动、波浪破碎、波浪随机性及非线性、潮流等因素是今后植物消波研究的重点突破方向。 相似文献
14.
Lyle M. Varnell 《Estuaries and Coasts》2014,37(2):508-523
A long-term (1948–2010) shoreward energy history of upper tidal shorelines in lower Chesapeake Bay was developed using a simple calculation of kinetic energy from corresponding wind and tide data. These data were primarily used to determine the likelihood of shoreline energy increases coincident with local sea level rise. Total annual shoreward energy ranged from 620 kJ/m of shoreline in 1950 to 17,785 kJ/m of shoreline in 2009. No clear linear trends are apparent, but mean annual energy shows an increase from 2,732 kJ/m before 1982 to 6,414 kJ/m since then. This increase in mean energy was accompanied by more numerous spikes of comparatively higher annual energy. Shoreward energy delivered to lower Chesapeake Bay’s upper tidal shorelines was enabled by an increasing amount of time per year that tidal height exceeds mean high water, accompanied by increasing heights of tidal anomalies. An index termed the Hydrologic Burden was developed that incorporates the combination of time and tidal height that demonstrates this increasing trend. Although opportunities for greater shoreward energy increased as the Hydrologic Burden increased, and even though there is evidence that greater energy was delivered to the shorelines during the latter time series, energy per hour delivery was shown not to have increased, and may have decreased, due to a steady reduction in average wind speed in lower Chesapeake Bay since the mid-1980s. Energy delivery in lower Chesapeake Bay was primarily from the northeast, and energy delivery over the time series is shown to organize symmetrically around a point between the northeast and north–northeast directions. This is evidence of a self-organizational phenomenon that transcends changes in local wind and tide dynamics. 相似文献
15.
A Field Study of How Wind Waves and Currents May Contribute to the Deterioration of Saltmarsh Fringe
Deltaic landscapes, such as the Mississippi River Delta, are sites of extensive conversion of wetlands to open water, where increased fetch may contribute to erosion of marsh edges, increasing wetland loss. A field experiment conducted during a storm passage tested this process through the observations of wave orbital and current velocities in the fringe zone of a deteriorating saltmarsh in Terrebonne Bay, Louisiana. Incident waves seaward of the marsh edge and wave orbital and current velocities immediate landward of the marsh edge were measured. Through a dimensional analysis, it shows that the current and orbital velocities in the marsh fringe were controlled by the incident waves, inundation depth, submergence ratio, and vegetation density. Similarly, it is shown that the longshore currents in the inundated saltmarsh fringe depended on the local wave-induced momentum flux, vegetation submergence, and vegetation density in the fringe zone. The cross-shore current showed the presence of a return flow in the lower region of the velocity profile. A high correlation between the current direction and the local flow-wave energy ratio as well as the vegetation submergence and density is found, indicating the important role of surface waves in the fringe flow landward of an inundated wetland under storm conditions. The field observations shed light on the potential ecological consequences of increased wave activities in coastal saltmarsh wetlands owing to subsidence, sea level rise, limited sediment supply, increases in wind fetch, and storm intensity. 相似文献
16.
Linking pattern to process in reef sediment dynamics at Lady Musgrave Island,southern Great Barrier Reef 总被引：1，自引：0，他引：1 
下载免费PDF全文
下载免费PDF全文 Sarah M. Hamylton Rafael C. Carvalho Stephanie Duce Chris M. Roelfsema Ana Vila‐Concejo 《Sedimentology》2016,63(6):1634-1650
Linking surficial sediment patterns in reef environments to the processes that underlie their depositional dynamics enables predictions to be made of how environmental changes will influence reef‐associated sedimentary landforms, such as islands and beaches. Geomorphic linkages between sediment deposition patterns and the biophysical processes that drive them are often poorly resolved, particularly at broad landscape scales where tangible statements can be made about structural changes to landforms. The present study applies geospatial techniques to link patterns in reef sediment dynamics at Lady Musgrave Island to the underlying processes driving them. In situ calcification is characterized by developing a high resolution map of the surficial calcium carbonate producing communities inhabiting the reef platform, and associated sediments across the reef flat are analysed for grain size, kurtosis, sorting and threshold bed shear stress to explore transport pathways across the reef flat and lagoon. Wave energy is modelled across the entire reef platform as a potential driver of sediment dynamics, and morphometric linkages are empirically defined between wave energy and grain size. Findings indicate that carbonate sediments are primarily sourced from calcifying communities colonizing the outer periphery of the reef platform and that sediment grain size can be reliably linked to wave energy by virtue of a linear model. 相似文献
17.
为研究斯托克斯漂移对近岸污染物输移的影响,首先建立波导流和考虑斯托克斯漂移的对流扩散数值模型,通过数模结果与实验结果的比较,研究平直斜坡地形下规则波入射时斯托克斯漂移对污染物输移的影响,波导流模型中波浪场基于波能守恒方程来模拟,波导流场基于Longuet-Higgins提出的辐射应力来模拟,污染物对流扩散模型考虑了斯托克斯漂移的影响。其次,利用一个算例来验证对流扩散模型,结果表明数值模型计算结果与解析解吻合良好。最后,利用该模型模拟了两个实验工况下污染物的输移,数值模拟结果与实验结果吻合良好,表明斯托克斯漂移对近岸污染物向岸线方向的输移有比较明显的影响。 相似文献
18.
Threshold studies of gravel size particles under the co-linear combined action of waves and currents
Gravel size sediment beds are tested under the combined influence of simulated wave action and co-linear currents in a laboratory flume. Critical current speed, at threshold, increases with increasing size. Superimposed wave energy causes a small reduction in the unidirectional current energy. For low values of wave-induced near bed current velocities, the resistance to erosion increases when the wave period decreases from 10 to 6 s. Finally, combined critical shear stresses are found to be lower than those predicted using the Shields curve, as modified for oscillatory flow. Grain protrusion is suggested as a mechanism to explain this divergence. 相似文献