Structure Of Flow Field Around Propeller Submarine And Control Of Simplified Submarine

In the 21 st century,submarine is the main warship in the naval battle.While submarine moves underwater at high speed,flow separation,boundary layer transition and complex flow field structure like large-scale vortex shedding are generated.The relative motion between solid and fluid and the irregular movement of the fluid arouse the internal disturbance of the fluid.During propeller propulsion,the internal disturbance of the fluid is aroused by its rotation.They are the sources of submarine hydrodynamic noises,which seriously affect the stealth performance of the vehicle.Therefore,it is required that the submarine should have higher maneuverability and combat performance.It is relatively necessary to analyze the flow field and fluid dynamics characteristics of the submarine under the medium or higher Reynolds number.For the reason of the diversity of submarine shapes,the flow field of DARPA Suboff submairne model is analyzed.Then the Suboff submarine model is simplified and the control of optimizing its flow field is studied in this paper.In view of these,the following studies have been carried out:1)Based on the viscous incompressible Naiver-Stokes equation,the finite volume method is used to numerically simulate the DARPA Suboff submarine flow field of Re=107,and the distribution of velocity,pressure and the three-dimensional vortex of the flow field are analyzed.By setting different wall boundary conditions,the turbulent submarine flow is analyzed and the effect of boundary layer generated by viscous fluid is presented.At the same time,the flow field with propeller propulsion is also calculated in this paper.The results show that propeller propulsion and the flow separation at boundary layer have great influence on submarine.2)Actually,submarine models have various shapes.DARPA Suboff model is simplified,and the flow around the submarine model is numerically calculated and analyzed in this paper.Sometimes the sail of submarine is required to be exposed to the surface of the water,and sometimes it is necessary to dive into the water.According to these operational requirements,this paper separately calculates the flow field of that sail is half exposed to the water surface;the side surface of sail is in the water;and the whole submarine is in the water.The hydrodynamic characteristics of partial immersion are analyzed.The results show that the different height of sail which is exposed to the air may lead to the differences of structure of flow field.3)The submarine is mainly underwater.The flow field of underwater submarine is analyzed.The hydrodynamic characteristics show that the navigation condition is not conducive to the submarine concealment.So,by using the electromagnetic force tangent to the wall surface,the flow of the boundary layer near the wall of submarine model is controlled.The flow field with electromagnetic force is numerically calculated.Different positions of(A=1,A=2 and A=3)submarine are added with electromagnetic force,as well the different electromagnetic force coefficients are applied respectively.The flow field structure is discussed in this paper,the vorticity distribution of the flow field,forces and torques of submarine are also analyzed and Fourier transform(FFT)is used for analysis,in order to improve submarine stability and maneuverability,reduce noise,and so on.The results suggest that the vortices appeared on the sail would be effectively suppressed when the electromagnetic force is applied to the junction of the hemispherical forebody and midbody(A=1,N=1.5).Applying Lorentz force on the top of sail(A=2,N=1.5)may effectively suppress the vortex shedding and the drag force(horizontal component of force)is reduced most.The decrease of submarine torques are most obvious when the electromagnetic force acts on the side surface of sail(A=3).Therefore,intelligent utilization of Lorentz force to control the boundary layer flow of the fin may efficaciously suppress the formation of irregular vortices and shedding,reduce flow noises and contribute to improve the stealth and the dynamic performance of submarines.Based on the finite volume method,the flow field around the full-appended submarine and its self-propulsion with propeller are numerically calculated in this paper.The flow field of the full-appended submarine is greatly affected.When the propeller is rotation,the resistance of submarine is reduced.At the same time,the full appendage submarine model is simplified,after that the flow field around the submarine model is calculated.The optimization control of the flow field around the submarine by electromagnetic force is researched.The results show that the electromagnetic force can restrain the vortex shedding,eliminate the vortex street,reduce the resistance,suppress the vibration and reduce the flow noise,and so on.Therefore,the work of this paper has certain practical significance for improving submarine combat performance.