Experimental Research On Extreme Wave Run-up In Cylindrical Structure

Cylindrical structure is a common structure type in Marine buildings.Wave along the cylinder will produce wave-run-up,which poses a certain threat to the superstructure.Especially with the continuous emergence of structures in deep water,the run-up generated by extreme waves in deep water has strong non-linear characteristics.How to accurately calculate the run-up,design the structure height reasonably,and reduce the impact of wave run-up is one of the issues concerned in the structural design.In this study,the effects of regular wave,irregular wave and focused wave on the cylindrical structure were simulated by physical model test method in the laboratory,and the wave run-up around the cylindrical structure was measured.The influence of wave steepness,structure scale and other parameters on the wave run-up was analyzed,and the empirical calculation formula of the run-up was given.The results show that:(1)The variation of wave run-up around the cylindrical surface under the action of regular wave,irregular wave and focused wave has the same rule,that is,the run-up at the front point of cylinder measured by experiment is the largest,and the wave run-up first decreases with the increase of angle,then becomes the minimum value at around 135°,and then increases with the increase of angle,which is consistent with the variation trend of theoretical formula results,but the theoretical results will underestimate the run-up at the front point of cylinder.(2)Different wave parameters(wave steepness,cylinder size and BFI)have influence on the measured run-up around the cylinder.For the wave direction of cylinder ?= 0 °,the wave run-up of the cylinder increases with the increase of wave steepness and cylinder size under different waves,and the probability of large wave run-up decreases with the increase of BFI under irregular waves.(3)Whether it is a large cylinder or a small cylinder,the run-up of the focused wave acting on the front surface of the cylinder is larger than that of the regular wave,and the maximum can reach 2.05,which indicates that the effect of the focused wave on the cylinder is more obvious.(4)Based on Stokes second-order wave theory and diffraction theory,the velocity and height of water quality point at the wave crest are calculated,and then the relationship between the empirical coefficient m and the relative scale ka of cylinder when regular wave,focused wave and irregular wave act on different cylinders can be well obtained by using the velocity head formula,so as to estimate the wave run-up.Compared with the measured results,the fitting effect is better.The results of this paper provide an important reference for the wave run-up of cylindrical structure,help to understand the wave surge height of actual deep-sea structures,and also provide support for the construction of offshore platform structures.