The Interaction Between Oblique Incident Waves And Caisson Structures With Perforaterd Wall

In the recent years, in order to reduce the total costs on project by diminishing the wave reflection and the wave force, many countries have conducted researches to study new type of caissons. The main emphases are focused on the perforated caissons because of two reasons: Firstly, the wave force acting on the front wall of a solid structure can be divided into two parts on two different walls with phase difference. The phase difference between the forces on the two walls is related to the distance between the two plates. To select the distance between the two plates suitably, the total wave force on the whole structure could be maintained at a lower level. Secondly, waves will dissipate when they transmit over a porous medium. Consequently, the reflection rate of waves from breakwaters can be reduced, and the wave run-up in front of the structure could be reduced, too.Based on three-dimensional experiment and the potential theory as well as eigen function expansion method, the interaction between oblique incident wave and caisson breakwater with traverse wall and the interaction of the oblique incident wave with partially-perforated caisson breakwater have been investigated. The experimental data have been compared with the theoretical results and a good result can be found. The effects of many parameters on wave reflection and wave force are discussed in details in the range of engineering practice.Theoretical solutions have been found to study the effect of double-layered perforated caisson on wave force and wave reflection based on the aforementioned two types of structures. Results obtained from numerical calculation show that in the range of engineering practice the wave force acting on double-layered perforated caisson breakwaters is less than that of single-layered perforated caisson breakwaters. Whether or not to adopt the double-layered caisson breakwater lies on the geometrical dimension of the caisson.Three-dimensional experiments have been undertaken in multi-function basin of the State Key Laboratory o f Coastal and Offshore Engineering, Dalian University of Technology. The sound consistency can be found between experimental data and the existing empirical equations. A new dimensionless parameter kθr Ik皉 (where kθr is the reflection coefficient by structures when incident angles is 9 ; kr?is the reflection coefficient by structures when incident angle is 0?) has been proposed to study the reflection coefficient of oblique incident wave with perforated caisson breakwater. By using the Ordinary Least Square Estimation, an empirical formula has been made to calculate kθr I k皉. The results of empirical and the experimental data show the sound consistency with each other. Based on linear wave theory, the paper illustrates that in the range of engineering practice, the wave force on unit length of perforated caissons has less impacts with incident angles. On the basis of the theoreticalresults, a new equation has been educed to calculate F,e I F1(ratio of the wave force on different length of structures to that on unit length of structures).