Wave Interaction With Combined Cylinders Structure With Perforated Outer Wall

In recent years, in order to reduce the total cost of project by decreasing the wave reflection and the wave forces, many countries have conducted researches on studies of new type of caissons. The structure of combined cylinders with a solid interior column surrounded by a coaxial exterior column with perforated wall at a section in azimuthal direction has been considered for the sake of good effect on reduction of wave force and wave run-up around the outside of the structure.The interaction of water wave with single combined cylinders with perforated outer wall, array of combined cylinders with perforated outer columns and solid interior columns and array of combined cylinders with perforated partially on the top section of outer wall have been investigated theoretically. A semi-analytic linear solution has been acquired based on an eigenfunction expansion of velocity potential and a linear model between the pressure difference between two sides of perforated wall and the fluid velocity inside it. Numerical experiments have been carried out to examine the influences on the wave forces and wave run-up around the outside of the structure of combined cylinders with perforated wall by the porous coefficient, the relative wave number, the ratio between the radii of the interior and the exterior columns, the ratio between the water depth inside and outside the columns, the distance between cylinders and the incident wave angle. The comparisons between numerical experiment results and the physical experimental results have also been carried out to verify the correctness of the theory.Physical experiments have been undertaken in the wave-current flume of the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. The empirical relationships between the relative wave forces and the reflection coefficient before structure with their main effect factors have been obtained through analysis of the physical experimental data. The sound consistency can be found between the empirical equations and physical model test data, and the comparison between empirical equations and theory results is also acceptable.