Research On The Drag Reduction Of Non-smooth Underwater Vehicle

In order to combat with new high-speed vessels more effectively, the range and speed of remote underwater vehicle must be improved greatly, noise and concealment are also need to be improved, Drag Reduction is the most direct and effective method to improve underwater vehicle’s technical performance. The underwater vehicle with lower resistance and noise attracted more and more attention of experts and scholars.Nowadays, non-smooth surface drag reduction is a new method which is very popular among experts and scholars, non-smooth surface drag reduction means that the body’s surface is covered by a layer of non-smooth structure (such as a triangle groove, waves, pits, etc.), so the turbulence of near-wall was changed, which can reduce the turbulence burst intensity of near-wall, the turbulence intensity of around fluid and the turbulence energy losses, so the resistance of underwater vehicles was reduced. This method does not change the shape of the body, do not need any additional equipment, so the method is green and without fluid contamination which has high engineering value.Based on the traditional study of the non-smooth drag and noise reduction, this paper proposed a multi-condition coupled non-smooth structure drag strategies targeted to reduce every part’s drag. In this paper, the process of fluid flow through the surface is divided into two phases:the horizontal position and fluid-solid separation phase, the common non-smooth structures are divided into two kinds:the diversion structure (such as a triangle groove) and adsorption structure (such as traveling wave), put the non-smooth structures on the above positions, analyze the drag reduction mechanism of every combination, study the effects of each combination on friction and pressure drag.This paper used Pro/E+HyperMesh+Fluent build numerical simulation system to study the non-smooth surface drag reduction, firstly, using Pro/E to extract horizontal position and fluid-solid separation position modeling, then use the CFD model of HyperMesh meshing module. Finally, use Fluent as solver to solve. Repeat the process, simulate every combinations under 0.5-10m/s speed.Use the Result model of Fluent to do the post-processing, then get the required data and the flow characteristics cloud. Found:the pressure drag play a more important role on fluid-solid separation position, put adsorption structure (such as waves etc.) on this position can absorb fluid reattach on the surface of body, which can improve the pressure of the underwater vehicle’s tail, reduce the differential pressure of body, and lower the pressure drags; on the horizontal position, the frictional resistance plays a more important role, put diversion structure (such as triangle groove etc.) on this position can reduce the turbulence burst intensity of near-wall, the turbulence intensity of around fluid and the turbulence energy losses. So the frictional resistance on horizontal position was reduced.Finally, integrated the horizontal position and fluid-solid separation position, put the adsorption structure on the tail of the underwater vehicle and put the diversion structure on the horizontal position of the underwater vehicle, and put the noise into consideration to do the fluid dynamics and noise simulation. The result shows that the frictional resistance and pressure drag of underwater vehicle covered with non-smooth surface was lower than that of smooth surface. At the same time the intensity of the near-wall turbulence burst region, the turbulence intensity of around fluid and the turbulence energy losses were weakened, so the turbulent noise was reduced too.Data and conclusions in this paper could provide data support for blade design of Savonius wind turbine in engineering applications to reduce workload and blindness of engineering design, and impact mechanism of structural parameters and auxiliary structure could provide theoretical support for the further studies.