Research On The Underwater Manipulator Vortex-Induced Vibration Response Characteristics

In order to respond to the important instructions of the national natural resources to help the high-quality development of the marine economy,the rational exploration and utilization of marine resources is imperative,and the application of the underwater manipulator conforms to the needs with the development of the times.In marine engineering,the underwater manipulator will interact with ocean waves and ocean currents,so the vortex-induced vibration will cause the positioning error,wake disturbance,and reduce the service life,resulting in economic losses and ecological losses.By studying the flow around section of the underwater manipulator,the effects of sectional shape,spacing and incoming flow direction on the hydrodynamic performance and flow field characteristics of the underwater manipulator in the subcritical range are analyzed.The results show that the lift and drag coefficients of the elliptical section are 76.15% and 51.30% lower than those of the circular section,respectively.When the lower arm is located upstream,the lift coefficient of the upper arm is 3.4 times that of the lower arm.With the increase of the direction of the flowing direction,the RMS value of the lift coefficient of the downstream oval section increased by 1.5 times.Study the response of the underwater manipulator vortex-induced vibration in the subcritical range,and analyze the impact of the positions and the flow velocity on the underwater manipulator.The results show that the trajectory of the underwater manipulator was symmetrical,and as the flow velocity increased,the motion trajectory was offset towards the back of the zero point.When the lower arm was in the second quadrant,its own displacement was small and its vibration was weak,also the displacement of the rear circular section will also decrease.The transverse displacement of circular section increased with the increase of velocity,while the transverse displacement of elliptical section decreased with the increase of velocity.Finally,analyze the response of the underwater manipulator vortex-induced vibration.The results show that the displacement at the end is greater than the middle point in all states.As the angle of the arm 2 increases,the amplitude gradually decreases,and the frequency is almost synchronized.With the increase of flow velocity,the transverse displacement decreases,the vibration frequency decreases,and the difference between the displacement of the end of the lower arm and the displacement of the middle point increased.In the current flow,the end of the manipulator increases by 1.3 times compared to the transverse displacement of the middle point,and the vibration frequency difference between the arm section is weakened.In countercurrent conditions,the vorticity vibration response of the manipulator is enhanced,and the midpoint displacement is greater.However,the growth rate of the mid-point displacement is smaller than the end,and the two points reach the same frequency vibration state.The research content of this paper will provide theoretical guidance to reveal the vortex-induced vibration characteristics of the underwater manipulator and other marine equipment(such as marine risers and submarine cables,etc.).It can also be used as fundamental research to help the precise positioning and accurate fishing of the underwater manipulator in the ocean.