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Fundamentals of overtopping from individual violent water wave impacts

个别猛烈水波冲击翻越的基本原理

基本信息

批准号：
EP/D080754/1
负责人：
Andrew Hogg
金额：
$ 18.5万
依托单位：
University of Bristol
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FD080754%2F1
关键词：
Fundamentals overtopping individual violent water

项目摘要

Water wave impact on coastal structures such as sea walls, dikes and breakwaters, can lead to water overtopping the structure. This can cause difficulties in the area the structure was built to protect, and possibly damage the structure. Most previous studies of overtopping have examined the total flow of water for a given sea state, and many fewer studies consider individual wave events. These latter have focussed on collecting data on the overtopping event rather than relating it directly to the behaviour of the incident wave, which is the focus of the proposed work. Many types of disturbance and damage are more closely related to individual overtopping events than to the total flow over a longer period. Our recent substantial experimental and numerical modelling work on wave impact on walls, shows the likely importance of relatively rare very violent impacts, and provides a basis for quantitative modelling of wave overtopping, of both violent and more ordinary waves. Greater understanding of these infrequent events will be valuable for both coastal engineering researchers and practitioners alike.The present investigation will again capitalise on the advantages of interactive physical and numerical model studies as a means of gaining new insights into complex wave phenomena. Thus, it is proposed to concentrate in detail on situations of particular scientific interest rather than engage in extensive parametric testing. We note, for example, that there has been little study of the transition between breaking and non-breaking waves on steep beaches / gently sloping structures and expect to find significant differences in swash and overtopping between collapsing and surging breakers on a steep slope. Effects of the structure's geometry, such as different slopes and crest width, will also be examined. The approaching waves will either come over a plane sloping bed or meet a mound at the base of the structure that can trigger plunging or spilling breakers. Experimental measurements of water height, flow rate and pressure will be made. The flow will be numerically modelled by modifying existing programs, one of which includes the compressibility that can be important when air is trapped or entrained by the water. Scaling of results from laboratory measurements to prototype scale can be improved by including such effects. We expect the flow over a structure to depend significantly on its surface roughness, and many protective structures are made of units which are very rough. The study will consider simple roughness elements; for example circular cylinders projecting from the surface. Flow around and over a single roughness element will be related to their overall effect. In the case of the most violent wave impacts we expect that the roughness may also diminish the maximum pressure, by its disturbing effect on the flow.Theoretical work will include analytical study as well as making use of existing numerical programs. Analytical study is a 'blue skies' element of this proposal in that it is rather challenging. It will build on models of swash, since there are very few previous results for overtopping. However, analytical results can be of great value in comprehending different flow regimes.Overall, results from all aspects of this study are to be used to develop improved models of overtopping events that are expected to be useful for designers of coastal structures such as breakwaters and seawalls.

水波对海岸结构物如海堤、堤防和防波堤的冲击会导致水漫过结构物。这可能会在该结构所保护的区域造成困难，并可能损坏该结构。以前关于过顶的大多数研究都考察了特定海况下的总水流，而考虑单个波浪事件的研究要少得多。后者侧重于收集超顶事件的数据，而不是将其直接与入射波的行为联系起来，这是拟议工作的重点。许多类型的扰动和破坏与个别过顶事件的关系比与长时间内的总流量的关系更密切。我们最近对波浪对墙壁的冲击进行了大量的实验和数值模拟工作，表明了相对罕见的非常强烈的冲击可能的重要性，并为波浪溢出的定量模拟提供了基础，包括猛烈的和更普通的波浪。更深入地了解这些罕见的事件对海岸工程研究人员和实践者都是有价值的。目前的研究将再次利用相互作用的物理和数值模型研究的优势，作为对复杂波动现象获得新见解的手段。因此，建议将注意力集中在具有特殊科学兴趣的情况上，而不是进行广泛的参数测试。例如，我们注意到，在陡峭的海滩/平缓的斜坡结构上，很少有关于破碎浪和非破碎浪之间过渡的研究，并期望在陡峭的斜坡上发现崩塌浪和汹涌浪之间的冲刷和过顶的显著差异。结构几何的影响，如不同的坡度和波峰宽度，也将被检查。接近的海浪要么会越过一个平面倾斜的河床，要么会遇到结构底部的一个土丘，这可能会引发巨浪的俯冲或溢出。将进行水高、流量和压力的实验测量。流动将通过修改现有程序进行数值模拟，其中之一包括当空气被水捕获或夹带时可能很重要的压缩性。将实验室测量的结果按比例调整到原型比例可以通过包括这些影响来改进。我们预计，流过结构的气流在很大程度上取决于其表面的粗糙度，而许多防护结构都是由非常粗糙的单元组成的。该研究将考虑简单的粗糙度元素；例如，从表面突出的圆柱体。流动的周围和超过一个单一的粗糙度元素将关系到他们的整体效果。在最猛烈的波浪冲击的情况下，我们预计粗糙度也可能通过其对流动的干扰作用降低最大压力。理论工作将包括分析研究以及利用现有的数值程序。分析研究是这个提议的“蓝天”元素，因为它相当具有挑战性。它将建立在冲刷模型的基础上，因为之前很少有关于overtopping的结果。然而，分析结果对于理解不同的流型有很大的价值。总的来说，这项研究的所有方面的结果都将用于开发改进的漫顶事件模型，这些模型预计将对防波堤和海堤等海岸结构的设计者有用。