Numerical Investigation Of The Influence Of Opening Rate On Reflection Coefficient Of Perforated Caisson With Rubble Foundation

In recent years,due to the fact that the physical vertical wall breakwater structure is susceptible to “total reflection” in front of the embankment,the wave causes greater impact on the structure and causes damage.More and more low-reflection breakwaters have been obtained in port engineering construction.Since it was proposed,the structure of perforated caisson breakwaters has been widely used in practical engineering construction such as piers and revetments because of its remarkable wave-removing effect and low construction cost,and it is also a topic that many scientific researchers pay attention to.So far,the results of physical model tests on perforated caisson have been relatively comprehensive,and there have been relatively few research results on numerical model tests,and on the results of physical model test of perforated caisson(including Code of Design and Construction of Breakwaters).The opening rate ? is usually reflected in a linear relationship in the calculation formula of the wave reflection coefficient Kr of the perforated caisson,and the applicable range is 0.2 to 0.4.However,when ?<0.2 or ?>0.4,the influence of opening rate ? on wave reflection coefficient Kr still needs further research and discussion.This paper closely follows the actual engineering requirements,simulates the interaction process between the regular wave,irregular wave and the perforated caisson on the rubble foundation,and studies the influence of the opening rate ? on the wave reflection coefficient Kr of the perforated caisson on the rubble foundation.Based on the volume average-Reynolds-averaged Navier-Stokes equations,the CLEAR-VOF method is used to track the free surface,the volume-averaged k-? equation is used to deal with the turbulence effect,and the three-step finite element method is used to solve the equation discretely.In the numerical wave tank,the effect of the opening rate on the wave reflection coefficient was studied within the range of the enlarged opening rate.The calculated values of the numerical model agree well with those of other scholars.In the range of 0.2???0.4,the empirical relationship fitted by the physical model test and the calculation formula of the wave reflection coefficient in Code of Design and Construction of Breakwaters.It is appropriate to describe the influence of the opening rate ? on the reflection coefficient Kr by a linear relationship.When ?>0.4,the trend of the empirical relationship fitted to the numerical simulation value and the physical model test is consistent.When ?<0.2,the reflection coefficient Kr of the perforated caisson increases with the decrease of the opening rate ?,the empirical relationship fitted by the physical model test and the linearity of the wave reflection coefficient calculation formula in Code of Design and Construction of Breakwaters.The relationship between the opening rate ? and the reflection coefficient Kr is not appropriate.The research results are of great significance to the deep understanding of the mechanism of the wave-breaking of perforated caisson and the optimal design of the caissons.