3D Numerical Investigation of Forces and Flow Field around the Semi-Submersible Platform in An Internal Solitary Wave

Abstract

Characteristics of hydrodynamic forces and flow fields around the semi-submersible platform induced by the internal solitary wave (ISW) propagation were investigated in a 3D numerical wave tank. Good agreements between numerical results and experimental data of forces and torque on the platform were achieved. The hydrodynamic loads increased and decreased with the increases in the ISW amplitude and fluid depth ratio, respectively. The pressure mainly contributed to the force on the platform. The horizontal forces on bracings were negligible. Almost all the vertical forces on the platform were derived from those on pontoons. The horizontal force and torque on the platform increased with the increases in the angle between the platform symmetrical axis and the ISW propagation direction. The platform subjected the maximum vertical force when the angle was 0°. There were obvious velocity reductions around the platform during the ISW propagation, as visible vortexes shedding around the platform could be observed. Complexities of the distributions of flow fields around the platforms located at the 30°- and 60°-direction were greater than those around the platforms located at the 0°- and 90°-direction. Flow fields around the same kind components of each platform located at different angles were similar.

Numerical Investigation of Internal Solitary Wave Forces on a Moving Submarine

“…In stage IV, the submarine passes through the interface of the ISW again. The dynamic pressure on the head becomes larger than that on the tail, thus the C x increases and reaches the positive maximum at 7 when the submarine enters the lower layer, as seen in Figure 12g. In stage V, the dynamic pressure both on the head and the tail tends to be 0, thus the C x gradually becomes 0.…”

“…As shown in Figures 10 and 11 The loads on the submarine during the propagation of ISWs mainly consist of three components: horizontal forces F x , vertical forces F z and torque M y . The nondimensional form of these forces can be written as follows [7]:…”

“…The results indicated that the horizontal and vertical forces on the semi-submersible platform due to ISWs can be divided into three components, namely the wave pressure-difference force, viscous pressure-difference force, and the frictional force, in which the frictional force is negligible. The experiments conducted by Chen et al [6] and the numerical simulation performed by Ding et al [7] indicated that the maximums of the forces and moments increase linearly with ISW amplitude and layer depth.…”