Study On Hydrodynamic Performance And Speed Prediction Of Wave-propelled Unmanned Boat

The ocean is rich in resources.Since the 21 st century,with the increase of population,the development of the world economy has been gradually constrained by the lack of resources.All countries are trying to develop new ways to utilize marine resources.To develop the ocean,we must first understand the ocean and build an ocean observation system,fixed marine observation equipment such as moored buoys and submersible buoys are widely used to measure hydrometeorological elements such as wave height,current,water temperature,wind speed,and air pressure.These devices can conduct observations in a specific sea area,but cannot achieve mobile observations.With the development of the marine industry,hydrofoil propulsion has become a research hotspot.The wave-propelled unmanned craft consists of a surface hull and a hydrofoil installed at the bow or stern.The hydrofoil moves with the boat body in waves to obtain thrust and drive the unmanned craft to run forward at a certain speed.It has the characteristics of low energy consumption and long endurance,which makes the wave-propelled unmanned craft have a very broad application prospect in the field of ocean observation.In this paper,the STAR-CCM+ software was used to simulate the free-navigation performance of the wave-propelled unmanned craft when encountering different wave conditions,and the variation laws of its speed,motion response and hydrofoil propulsion performance with parameters such as wave height,wave period,and torsional spring stiffness are obtained.First,the STAR-CCM+ software was used to model the catamaran without hydrofoil based on the Reynolds-averaged Navier-Stokes turbulence model,the VOF method and the overset mesh technology,and the mesh independence were verified.The motion responses of the catamaran in head waves at zero forward speed is simulated,and the results are compared with the Aqwa results based on the potential flow theory to verify the accuracy.Then,the fixed wing catamaran with bow is modeled and simulated according to the parameters in the literature,and the calculated results are compared with the model test results.Then,the drift velocity of the catamaran before hydrofoil installation is calculated when encountering the head wave and the following wave.Then,a fixed hydrofoil is installed at the bow of the catamaran,and the motion response function and sailing speed of the wave-propelled boat when sailing in head and following waves are calculated.The influence of the wave period and wave height on the thrust of the hydrofoil,the speed of the hull and the motion response was analyzed,and the propulsion mechanism of the wave-propelled boat was explored by analyzing the flow field around the hydrofoil.Finally,the multi-body coupling and slip mesh technology are used to simulate the wave-propelled unmanned craft with hinged wings,and the influence of parameters such as wave conditions and spring stiffness on the hydrofoil thrust,the sailing speed and the motion response of the wave-propelled unmanned boat was analyzed.The numerical simulation results show that the hydrofoil mounted on the bow can produce thrust force under certain wave conditions so that the unmanned boat can navigate autonomously at low speed;The wave drift force acting on the hull and the thrust generated by the flapping hydrofoil are in the same direction when the wave propelled boat is sailing in the following waves,while opposite in the head waves,so that the free sailing speed of the wave-propelled boat in the following waves is higher than that in the head waves.The stiffness of the torsion spring has influence on the pressure resistance of the wave propulsion boat with articulated hydrofoil in waves.