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
Highlights
It is known that the resistance of submarines at full immersion consists of friction resistance, shape, roughness, cuts, protruding parts, and fencing of retractable devices
The coefficient of resistance of the other components was considered to be such as the coefficient of friction of the equivalent plate, which was determined by a known empirical dependence on the Reynolds number
The results of calculations showed (Fig. 7, 8) that with the correct choice of size, location and number of recesses, it is possible to achieve a reduction in resistance by 2–5 %
Summary
It is known that the resistance of submarines at full immersion consists of friction resistance, shape, roughness, cuts, protruding parts, and fencing of retractable devices. Recalculation of the results of such experiments should be carried out according to the Applied mechanics rules of similarity of fluid flows using similarity criteria Such a criterion for submarines in the above case is the Reynolds test. Since it is impossible to achieve equality of Reynolds numbers for the model and nature, in particular for submarines, the recalculation was carried out according to a known approximate empirical scheme According to this scheme, the coefficient of resistance of the shape was considered independent of the Reynolds number and was determined experimentally. The coefficient of resistance of the other components was considered to be such as the coefficient of friction of the equivalent plate, which was determined by a known empirical dependence on the Reynolds number This approach is very approximate because it does not take into account the peculiarities of fluid movement in the boundary layer of fullscale objects. There is a problem of reducing the resistance of such a case through the development of special methods that do not require adjustment of its size and shape
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