Hydrodynamic Characteristics Of An Innovative Light-weight Gravity Installed Plate Anchor:Physical Modeling

With the increasing global demand for energy,the exploitation of offshore oil and gas resources is gradually transferred from offshore to the deep sea,and the construction of offshore wind farms is also expanding to the deep sea.The dynamically installed anchors are used to anchor floating facilities.The dynamic penetration anchor which is installed by free fall installation mode depending on its own weight is more and more favored by the industry.At present,there are many researches on dynamic anchors,such as torpedo anchor,deep penetration anchor and OMNI-Max anchor.Based on the advantages and limitations of the OMNI-Max and torpedo anchors,an innovative light-weight gravity installed plate anchor(L-GIPLA)was designed.The research shows that the L-GIPLA has the advantages of deep embedment depth,high capacity-to-weight ratio,and diving property.The research of the L-GIPLA provides technical support for the development of marine engineering in China.The hydrodynamic characteristics of the L-GIPLA in free fall stage is the key to the penetration process of anchor in the seabed,such as penetration depth,capacity efficiency and so on.Therefore,it is of great significance to study the hydrodynamic characteristics of the L-GIPLA for the anchor installation.In this paper,the model test is used to simulate the installation process of the dynamic anchor free fall in the water,and the hydrodynamic characteristics of the L-GIPLA are studied as follows:(1)Firstly,the present study is aimed to investigate the drag coefficient,terminal velocity of the L-GIPLA at the different topological shapes and optimize it.(2)Secondly,the booster fin is designed for the hybrid anchor(L-GIPLA aid of a booster)to improve both the directional stability and terminal velocity of the anchor.(3)Thirdly,in order to mitigate the effect of the mooring line on the directional stability of the hybrid anchor,an additional fin is set at the rear of the anchor.And the control system that can control the falling deflection angle of the hybrid anchor is also introduced.(4)Finally,based on model testing results,the geometry of the L-GIPLA is optimised with folding shank.The L-GIPLA with folding shank is favourable for improving the directional stability and reducing the drag coefficient for the hybrid anchor.