| Under the influence of sea levels rising by the global warming and storm surge disasters increasing, Chinese coastal areas will face a standard of protection embankment shortage. Simply heightening dikes will cause a series of disadvantage, such as a huge investment in construction and maintenance, bursts of r isks and losses to increase, coastal residents and other land users to increase the sense of insecurity, deterioration of coastal environment. Comcoast is a European project which develops and demonstrates innovative solutions for flood protection in coastal areas. Comcoast creates and applies new methodologies to evaluate flood zones from an economical and social point of view. A more gradual transition from sea to land creates benefits for a wider coastal community and environment whilst offering economically and socially sound options. The aim of ComCoast is to explore the spatial potentials defence strategies for current and future sites. The focus of comcoast is selecting cross-section of dike allowed overtopping。Traditionally, physical modeling approach is used to study overtopping of water waves over seawalls. Nowadays numericalwave tank(NWT) is a potential tool to study propagation,deformation and breaking of water waves with numerical experiments.Based on the N-S equation, the VOF method is used to track the free surface, the additive sources in the momentum equation are used to generate and absorb waves, the method of waves generating and absorbing i n the viscous fluid is presented. The numerica I wave flume which can both generate waves is obtained. The validity of waves generating is numerically confirmed.After review of the literature on the overtopping of dikes, regular wave overtopping over the crest of an impermeable coastal structure I ocated on a s I op i ng beach i s pred i cted numer i ca I I y by us i ng the numerical model developed previously for predicting wave run-up on such a structure located on the horizontal seabed. The computed average overtopping rates are shown to be in good agreement with available small-scale test data and the results calculated by the Holger Schuttrumpf (2002). Compared to the Holger Schuttrumpf theory equations, the present NWT can effectual ly solve the problems, which include the violent deformation, jet and breaking of the free surface.Although wave overtopping is explicitly considered in the design of dikes, only mean overtopping rates are included ae a desing parameter now. However, mean overtopping rates are neither appropriate for the description of the infiltration and erosion processes nor for the initiation of dike fanilures. The previously pibl ished results show that sometimes mean overtoppong rates are not always appropriate to describe the associated dike failures. Flow velocities and layer thickness of the water over the dike are required to assess the inflitration and erosion on the landward side of the dikes by overtopping water. Based on date of chapter 4, Compared to the Holger Schuttrumpf theory equations, the present NWT is capable of simulating the wave overtopping process after all, effectively simulating waves run-up, flow depth and velocity on the seadike slope, and effectively simulating flow depth and velocity on the crest dike and the landward dike. Distribution of overtopping flow depth, velocity is impacted by different structural type of the dike. The numerical wave flume is used to study the overtoppong precoss of different structural type of the dike. The overtopping flow is changed as the crest width, landword slope, friction of the dike are changed.1) when the crest width of dike is among 3m-6m, the overtopping layer thickness and velocity on the crest dike is increased with the increase of the crest width of dike.2) When the landward slope (1:m) i s 1:2-1:4, the overtopp i ng ve I oc i ty on the I andward slope of dike is increased with the increase of the value of m.3) The overtopp i ng velocity on the crest on the I andward slope of dike is reduced with the increase of bottom frittom.
|
PDF Full Text Request