波浪入射角度对不规则波波浪爬高的影响

1 . I ntro d uc t io n
Wave run-up resulting from the storm water level and related sea waves is the most important criterion for the design of sea dikes. Wave run-up is the phenomena in which an incoming wave crest runs up along the slope up to a level that may be higher than the original wave crest. The vertical distance between still water level SWL and the highest point reached by the wave tongue is called the run-up ”R ”. To estimate the wave run-up ， the reduction coefficient method is used in the paper. Moreover for the reduction coefficient method Van der Meer and De Waal [WL, 1993-2] and Chen Guoping (1989) put forward their own formulas. Many investigations were performed on wave run-up in the past, resulting in simple empirical formulas. Extensive investigations on normal wave run-up were performed in the past, but only a few investigations on oblique wave run-up are available. Therefore, the research concerning about the influence of angle of wave attack on wave run – up is necessary.
1
http://www.paper.edu.cn
The tests employ JONSWAP spectrum
= the dimensionless constant = the raising factor of spectrum peak, taking 3.3
0.07 p 0.09 p .
wk.baidu.comFig 1: Plan view of the model set up
2
http://www.paper.edu.cn
4 . T e s t P a r a m e te r:
For Wave -run-up Water depth: h Slope: m =40cm, 50cm =0, 1.5, 3.0 =6cm, 8cm Ts =1.0s, 1.5s, 2.0s Angle: â (Long -crested wave) = 0 °,10°,20°,30°,40°,50°,60°,70°,80° Significant Wave height: Hs Mean wave period
5 . T e s t P ro g r a m m e
All model tests were performed with a smooth slope m=0,m=1.5 and m=3 of the dike in constant water depth of 0.5 m. The wave height was Hs = 0.08 m ， Hs=0.06m while using different wave period Ts =1.0s,1.5s,2.0s.The angle of wave attack â is from 0° to 80 ° in steps of 10°.
g S 5
2
exp 1 . 25
p

4

p 2 exp 2 2 p 2



p
= the frequency of spectrum peak
3 . M o d e l S e t- U p A nd I n s tr um e nta tio n
The model tests on oblique wave run-up were performed in the wave basin of Jiang ning campus of Hoahi University. The wave basin has a length of 35 m and a width of 18 m. It is equipped with a 48-segment multidirectional wave machine which is installed at the longer side , each segment is 0.4 m wide and is independently controlled so that both long-crested and short-crested waves can be produced. 5 m length of simple slope m=0 , m=1.5 and m=3 of model has been placed 20 m apart from the wave machine. Wave height and run-up are measured with the use of the capacitance type wave run-up gauges and, and 3 capacitive run-up gauges were placed in the centre section of the model. The wave run-up data are collected by a multifunctional acquisition system manufactured by China Institute of Water Resources and Hydropower Research. More than 250 groups of experiment have been carried out. Each group of experiments has been made two times to reduce error. Wave absorbers are installed opposite the wave machine and partly along the longer sides to minimize reflections within the basin. An overview of the model set-up is given in Figure 1;
http://www.paper.edu.cn
Inf luence of wave angle on irregular wave run- up
Ji Wenwen, Yan Shichang, Chen Guoping (College of Traffic Engineering, Hohai University, Nanjing 210098, China) kkl@iscooler.com
Abstract
In the paper results of basic investigations on irregular wave run-up with special regard to oblique wave approach is analyzed. To investigate the influence of angle of wave attack on irregular wave run-up, physical model experiments has been performed in the wave basin of Jiangning campus of Hohai University. More than 250 groups of experiment have been carried out. Each group of experiments has been made two times to reduce error. The influence factor r â has been set out against the angle of wave attack, â . Key words: irregular wave, wave run – up, angle of wave attack, influence factor
2 . D e s ig n A p p r o a c h
There are various influences on wave run-up and overtopping such as the influences of a stepped slope and / or a berm, a shallow foreshore, the roughness, double – peaked spectra, relative crest height, wave steepness, relative local water depth, wave period, obliquely incoming waves, both short -crested and long- crested and so on. Due to the large number of relevant parameters and the very complex water motion at the structure, a theoretical approach to the wave run -up problems is not practical. Therefore, it is decided to perform physical model tests in order to verify the influence of angle of wave attack. But in this paper, special attention will be paid to the influence of angle of wave attack on irregular wave run-up. And also the influence of wind affect is neglected. So the main factors influence on irregular wave run up is described as a function of ; R=f (Hs, Tp, B, g, m, â …… ..)
6 . T e s t R e s ults a n d A na ly s is o f t he I nflue nc e o f the a ng le o f w a v e a tt a c k o n w a v e run- up
Fig:2 Definition of angle of wave attack The angle of wave attack possibly affected b y the foreshore through refraction, is of importance. The angle of incidence of wave attack â is defined as the angle between the direction of propagation of the waves and the perpendicular to the long axis of the dike, see figure1.Perpendicular wave attack is thus shown by â = 0º. The angle of wave attack is the angle after any change of direction of the waves on the foreshore due to refraction. From fig (3) to (9), based on the results of the experiment data, the relationship between the influence factor of wave attack on wave run up r â and the angle of wave attack â is described as following. Long-crested waves cause between 0 º < |! â | < 30º almost the same wave run-up as perpendicular wave attack. The reduction factor is almost equal to 1 .So during these 0 º < |! â | < 30º range, the effect of wave angle on wave run up is a little. And when the increased of angle â with step of 10 º up to 80º, it can be seen obviously the decreasing of influence factor for wave attack. When â >30 ◦ the value of reduction factor reduced until to â =60 ◦. At â =60º, the influence factor falls quite quickly. At â >60 º, the influence of angle attack on wave run up is not large.