A study of the effect of recesses on the motion resistance of submarines by methods of computational fluid dynamics

Abstract

A new method of reducing the resistance of submarines is presented, which consists in installing special circular recesses on its surface in the stern. It is found that during the movement, in the recesses there is a macro-vortex flow, in which pressure decreases significantly. This phenomenon affects the characteristics of the boundary layer and in general the pressure distribution on the surface of the hull, i. e. the resistance of the submarine. Using the methods of computational fluid dynamics, the influence of the number and size of the recesses at their fixed location on the resistance of two types of "Lira" and "Gepard" submarines is investigated. The results show that the decrease in resistance increases with increasing Reynolds number and reaches 6 % for "Lira" with 4 recesses with a diameter of d=0.01 D at Re=1.55. 108 and 2 % at Re=1.35. 108 for "Gepard" with 7 recesses with a diameter of d=0.01 D. The effect of the number of cells of the computational grid on the results of calculations in the Flow Simulation (USA, France, Canada) and Flow Vision (Russian Federation) software packages was also studied. The effect of resistance reduction obtained in both software packages is approximately the same, but the absolute values differ due to the small number of cells in Flow Vision, which is due to the limited capabilities of the used 2nd version of this complex. There was also a slight effect of resistance reduction on the model of the "Persia-110" (Iran) submarine with recesses during towing tests in the research basin at significantly lower Reynolds numbers. Unlike most resistance reduction means, the use of this method does not require significant changes in the design of the housing. This makes it possible to use it both on new facilities and on facilities that have already been commissioned