Study on vortex-induced vibration characteristics of an underwater manipulator in a complex flow field

Underwater manipulator plays a significant role in marine development. Vortex-induced vibration occurred under the action of fluid during operation, which affected the precise positioning and control of the underwater manipulator. Therefore, this work carried out vortex-induced vibration analysis of an underwater manipulator in a complex flow field. Numerical calculation models were established and combined with experimental tests, and the vortex-induced vibration characteristics of the manipulator in complex flow fields were studied. The variations in hydrodynamic forces, flow field characteristics, and vibration responses of the manipulator under different flow field environments were analyzed. The results demonstrated that the lift coefficient of the manipulator in the shear flow field was significantly higher than that in the uniform flow field, with the lift coefficient of the lower arm increased by 18.3%. With the increase in shear rate, the shedding of vortex structures became more pronounced. Stratified flow meanwhile emerged in the flow field, which led to the intensified vibration response of the manipulator. On the other hand, the low-speed region behind the manipulator in the stepped current was larger than that in the uniform flow field. Correspondingly, compared with the uniform flow field, the lift and drag coefficients decreased by 44.8% and 12.6%, respectively. The vortex shedding exhibited a wider and longer scope in the stepped current compared to the uniform flow field. The research results of this work provided theoretical support for the construction of an accurate hydrodynamic model of an underwater manipulator and offered references for studying the hydrodynamic performance of other equipment in marine engineering.