| Porous material exhibits special properties due to the existence of small pores and has been widely used in energy absorption,vibration reduction,filtration and separation.This paper uses 304 stainless steel wire mesh as raw material to prepare porous plate.It not only maintains the conductivity,welding performance,and plastic processing properties of the base material,but also has the permeability and energy absorption of the porous material.Air-film on the surface of the vehicle is artificially applied to decrease the friction,which is defined as underwater air-film drag reduction.Underwater air-film drag reduction is important for the speed,flexibility and energy consumption of the vehicle.This paper proposes the application of stainless steel wire mesh porous materials as surface coverings on underwater vehicle.To explore the effect of underwater air film drag reduction,the following research work has been carried out:Firstly,using 304 stainless steel wire mesh as raw material,the sintered stainless steel wire mesh porous plate was prepared by winding,pressing,rolling and vacuum sintering.The pore size approximately 0?m to 60?m,and the porosity is between 20% and 40%.It is observed there are no obvious pores on the surface,and the metal skeleton remaines continuous.The pores are distributed uniformly,and the pore channels are complicated.Its permeability has a close relationship with porosity and thickness.The plate has high porosity and smaller thickness,has better gas permeability.Secondly,underwater air film drag reduction test model is designed using the porous plate.The test model is designed as a conical rotating body and a cylindrical rotating body by actual processing conditions and fluid mechanics principles.The structure is easy to fabricate.Thirdly,an underwater air film drag reduction test platform was designed.A high-pressure tank was innovatively proposed to supply water,which greatly improves the stability of water flow.At the same time,the cooperation of the hollow axis and the linear bearing is applied.The experimental system,water supply system,and force measurement system are reliably connected to form a complete water tunnel device.The underwater air film drag reduction test method is summarized,which lays the foundation for the experiment.Fourthly,the effects of water supply pressure?air-film supply pressure and tail domes on drag reduction were discussed.The experimental results reveal that when the air-film supply pressure is constant,the drag reduction ratio increases with the increase of the water supply pressure in the tank.When the water supply pressure in the tank is constant,the drag reduction ratio increases with the increase of the air-film supply pressure.The optimal drag reduction ratio reached 30.9% when water supply pressure in the tank is 0.3MPa,and air-film supply pressure is 0.2MPa.According to the shape of the flow field around the test model,the gas-liquid two-phase flow field is divided into a stable part,a lifting part,and a dissipative part.Under different conditions,there are slight differences in the three parts.The main differences are that the higher water supply pressure in the tank and the higher the gas-film supply pressure,and the flow field around the test model is finally more disordered.The tail domes mainly affect the flow field,and then further influence the fluid resistance.It makes the flow field more uniform and stable,it can achieve higher drag reduction ratio when it works with air-film.Lastly,the analysis of the air-film drag reduction mechanism show that the air proportion has great influence on drag reduction,and higher air proportion leads to higher drag reduction. |
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