Research On The Mechanism Of A Circular Cylinder In Regular And Freak Waves

Cylindrical structures are widely used in offshore engineering,such as the hard tank of a Spar platform,columns of a semi-submersible,jackets,drilling pipes,risers and so on.Interactions between the waves and offshore structures are of great importance for engineering applications for long time,such as the non-linear phenomena of wave run-up,wave slamming.The modle test focuses on the wave elevation,but the evolvement rule of the flow field underwater is unclear,so it is important to study on the flow field of wave run-up by model test.The freak wave is extremely dangerous to offshore structures due to its unexpected high wave height,strong nonlinearity.Few efforts were exerted to investigate the flow field of the freak wave and the interactions between offshore structures.First of all,the flow field of the regular wave and freak wave is measured and compared with the linear wave theory.It can be deduced that the velocity gradient of the freak wave is larger than the regular wave's by the Comparison of horizontal particle velocity measurements under the crest point.The the paper focuses on the inline wave force and wave run-up acting on a truncated vertical circular cylinder and its impact factor such as the wave parameters and the submerged depth of the cylinder.Then model test were performed to investigate the slamming force on the truncated cylinder due to freak wave.The flow field around the truncated cylinder is measured by PIV and the influences of the submerged depth on velocity and the develop of flow field investigated due to regular wave.Finally,model test were performed to investigate the wave force and flow field on horizontal cylinder with different submerged depth due to the regular wave and the freak wave.The influences of different parameters such as wave steepness,the submerged depth and scatter parameter on slamming force and flow field were also investigated.