| Stealth is an important guarantee of submarine deterrence,and polar sea ice can provide good shelter for submarines,which makes submarine activities in the Arctic highly strategic,but the presence of sea ice is also a major reason for limiting submarine activities in the Arctic.In recent years,the global warming effect has gradually melted Arctic sea ice,and many broken ice waters and broken ice channels have appeared,which has facilitated the activities of submarines in the Arctic,but there are still many problems to be explored,first of all,submarines need to sail near the surface in some mission scenarios,but the hydrodynamic impact of the existence of polar surface ice on near-surface navigation submarines is still unknown.Secondly,the submarine realizes the floating operation through the ice crushing channel,but the broken ice in the channel will still pose a threat to the floating submarine,in addition,the broken ice drifting in the channel will also produce a load on the floating submarine,which needs to be studied.Finally,in an emergency,submarines need to break the ice layer to float,and the characteristics of ice loads on submarines when breaking ice have yet to be discovered.In view of the above problems,this thesis establishes a numerical model of crushed ice,crushed ice channel and layer ice with reference to the HSVA ice trough test and the statistical characteristics of Arctic sea ice,and uses the CFD-DEM coupling method and based on STAR-CCM+ software to study the hydrodynamic characteristics of submarine navigation near crushed ice surface before floating,the ice load characteristics of floating submarines in the ice crushing channel,the loading characteristics of ice floes on submarines in covered waters of layer ice,and the ice load characteristics of submarines when breaking layer ice,and the specific research results and conclusions are as follows:(1)The existence of polar ice crushing rink has brought many uncertainties to the nearwater navigation of submarines,and the friction resistance curve of submarines hardly changes before and after entering the crushed ice area,but due to the influence of irregular ice crushing rinks on the surface of submarines,the compressive resistance curve has produced obvious oscillations;Under the same speed,the same dive depth and the same ice thickness,the oscillation frequency and amplitude of the pressure resistance curve of submarines sailing under the waters covered by large-density crushed ice rinks are significantly greater than those of submarines sailing under smaller density crushed ice rinks.With the increase of submarine depth,the surface of the submarine weakens,the pressure resistance decreases,and at different depths,the impact of the surface ice crushing rink on the pressure resistance of the submarine is different,the closer to the surface,the greater the impact of the crushed ice on the submarine wave,so that the pressure resistance curve oscillates more violently.(2)Aiming at the problem of submarine floating on the polar channel,this thesis uses the CFD-DEM method and combines the overlapping grid technology to simulate and systematically analyze the whole process of floating in the submarine ice channel and its ice load characteristics,and studies the ice load characteristics of the floating submarine.During the rocking stage,the longitudinal rocking and rising and sinking of the submarine show periodic reciprocating motion in both positive and negative directions,and the submarine collides with the debris ice group on the surface of the channel many times,so that the ice load of the submarine at this stage has the characteristics of "segmented concentration";In the stabilization stage,due to the shaking of the submarine,the crushed ice group around the hull gradually moves away from the submarine,and the frequency of contact between the crushed ice and the submarine decreases,making the ice load of the submarine sparse at this stage.With the increase of the initial diving depth,the main parts of the submarine that are collided by the crushed ice group at the moment of exit gradually move forward,indicating that the safety of different parts needs to be considered for submarines floating at different initial depths,in addition,the length of the submarine’s rocking stage and the vertical speed when it comes out of the water are directly proportional to the initial depth of the submarine.(3)In view of this problem,this thesis studies the ice load characteristics of drifting broken ice borne by submarines after floating in the broken ice channel,and explores the differences in the ice load characteristics of submarines at different surface heights and the ice loads of submarines at different sea ice drifting speeds.The results show that the ice load of the submarine in the ice crushing channel after floating mainly includes the collision of the crushed ice on the front end area of the hull and the friction of the side area on the water surface,and the discontinuity of the collision and the continuity of friction make the change of the ice crushed ice load of the submarine a repeated "load-unload" process.Under the action of the hull wave and the constant flow dragging force,the crushed ice in front of the collision area gradually drifts backwards,so that the collision load generated by this part of the broken ice in the later simulation gradually decreases until it disappears.Due to the particularity of the crushed ice channel,the ice load of the submarine in the crushed ice channel is also different in all directions,the broken ice channel is narrower in the side and upward,and the crushed ice will accumulate upward on the side of the submarine under the action of fluid load,and the area of the ice load on the side of the submarine is much larger than the longitudinal and vertical direction,so that the lateral ice load of the submarine is significantly greater than the longitudinal and vertical ice load;By comparing the ice load data of submarines at four surface heights,namely λ =0,H/2,H and 3H/2,it is found that the ice load of the submarine is proportional to the height of the submarine,and the discrepancy of the ice load data becomes larger.In the range of four common Arctic sea ice drifting velocities(0.25kn-2kn)discussed in this thesis,the mean,one-tenth and one-third of the ice loads experienced by submarines increase with the increase of sea ice drifting speed,and the dispersion of the ice loads is proportional to the sea ice drifting speed.(4)Considering the situation that submarines need to float in the waters covered by layer ice in an emergency,this thesis studies the characteristics of ice load on submarines floating in water covered by layer ice,and discusses the ice load characteristics of different parts of the submarine and the difference of submarine ice load at different initial floating speeds.It is in the shape of an uninterrupted "wave-like" pattern;As the vertical motion amplitude of the submarine decreases,the oscillation amplitude of the ice load curve gradually attenuates and gradually approaches the mean line.Because the contact area between the command room and the layer ice is greatly reduced after the protrusion of the water surface,the ice load of the submarine command room is only larger in the early stage of the submarine floating,and the ice load in the command room is rapidly reduced after the partial fragmentation of the layer ice,while the ice load in the bow,the middle section of the hull and the stern of the boat are uninterrupted "wave-like" pattern.Since the middle section of the hull has the largest contact area with the layer ice,the maximum value of the ice load it is subjected to is the largest in each part.Since submarines with larger floating speeds have higher kinetic energy and larger motion amplitudes,the average and maximum value of submarine ice load are proportional to the submarine’s icebreaking floating speed,and submarines with larger floating speeds have a greater rise and fall amplitude of ice load during "afterburnerunloading". |
