Numerical investigation of a Wave-Powered Vertical Profiler

Abstract

The wave-power vertical profiler harvests surface wave energy through a buoy, and the converts the wave energy into a kinetic energy of a vehicle (underwater vehicle with sensors for profiling) via a mooring cable. The vehicle is aided by a unidirectional motion mechanism to submerge and surface in water. In this paper, a numerical simulation method is proposed to analyze the motion characteristics of the wave-power vertical profiler and reconstruct the entire moving process.Firstly, numerical work is conducted using Ansys Fluent software to investigate the response of the buoy to Stokes waves of different heights. Secondly, the relationship between the underwater vehicle's motion velocity and fluid resistance are studied. Finally, the numerical simulation results are combined using Matlab software to reconstruct the motion process and draw corresponding curves. Compared with the results from the water tank tests, our method can effectively reconstruct the vehicle's motion, with an accuracy rate of 96.5% in simulating the velocity values during the surfacing phase and a good match with the experimental results under natural sea conditions. We found that wave height is the determining factor for the vehicle's sinking time; the weight of the counterweight affects the vehicle's maximum sinking speed; the vehicle's net buoyancy and drag coefficient determine its surfacing speed, while the weight of the buoy can be ignored. Based on these conclusions, we recommend a counterweight weight of 100 N when the wave height is less than 0.6 m and an increase in weight when it exceeds 0.6 m. The recommended net buoyancy value for the vehicle is between 10 and 40 N, and the recommended buoy weight is 65 kg. We hope that these findings will be helpful for the design of wave energy buoys.