| In order to protect our maritime rights and interests,we must build a strong navy.As the main force of modern naval warfare,submarine has stronger concealment ability and assault ability than surface ships.How to improve the rapidity and concealment of submarine combat is the key to improve submarine combat ability.Exploring the hydrodynamic and wake characteristics of submarine near surface sailing can provide reference for the study of the hydrodynamic performance and non-acoustic stealth performance of submarine near surface sailing.In this paper,the direct navigation resistance characteristics of SUBOFF submarine and open water characteristics of KP505 propeller are studied.Then,the self-propelled point of SUBOFF matched KP505 propeller submarine model is predicted,and the submarine selfpropelled flow field is analyzed.Finally,the influence of free fluid on the submarine’s selfpropelled hydrodynamic force,the mechanism of the hydrodynamic wake generated at the free liquid surface and the influence of the submarine’s self-propelled hydrodynamic motion on the waveform of the free liquid surface were analyzed.The main research conclusions are as follows:(1)Based on the RANS method and the standard k-ε model,the direct navigation resistance characteristics of SUBOFF submarine were studied.The relationship between the total SUBOFF submarine resistance and the direct navigation speed was obtained by polynomial fitting,and the variation law of the drag coefficients of each component with the navigation speed was obtained.The open water performance of KP505 propeller was simulated by sliding grid method,and the open water performance parameters of the propeller were predicted.The variation rules of thrust coefficient and 10 times torque coefficient with the advance coefficient were obtained by polynomial fitting.(2)Based on the equal thrust method and the relative motion method,the self-propelled points of SUBOFF+KP505 submarine model at different speeds were predicted,and selfpropelled factors were given.Then,the velocity field of the flow field around the submarine,the pressure field on the surface of the submarine and the distribution of the three-dimensional vorticity field around the submarine were analyzed.It is found that there will be a high pressure area on the surface of the submarine when the submarine is moving by itself,and the pressure in the high pressure area will increase and the range will expand with the increase of speed.Tip vortexes will be generated at the top of control platform enclosure,cross tail fin and propeller blade,and horseshoe vortexes will be formed at the intersection of control platform enclosure and boat body.With the increase of speed,horseshoe vortexes,tail tip vortexes,blade tip vortexes and hub vortexes will all grow and widen,and they will interact with the boundary layer to form complex wake fields.(3)Based on RANS method and VOF model,the self-propelled hydrodynamic performance of submarine near the free surface was numerically simulated.It is found that the free surface will increase the drag value of the submarine.When the submarine’s depth exceeds about 1/3 of the length of the submarine,the drag increase can be ignored.The free surface will increase the velocity of the flow field between the submarine and the free surface,making the forward flow asymmetrical and uneven.With the increase of speed and depth,the acceleration effect will be weakened.The wave-wave mode at the free liquid level is affected by submarine speed and depth,that is,the greater the speed,the larger the wave-wave amplitude,the larger the Kelvin wavelength and the included Angle,the greater the depth,the smaller the wave-wave amplitude,the Kelvin wave length and the included Angle are almost unchanged,but the shear wave will be more obvious,and the scattered wave will gradually weaken. |
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