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潜艇的设计第2部分-潜艇的形状

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潜艇的设计第2部分-潜艇的形状 Some Aspects of Submarine Design Part 2. Shape of a Submarine 2026 Prof. P. N. Joubert 1 1University of Melbourne Defence Science and Technology Organisation DSTO–TR–1920 ABSTRACT A shape for a next generation submarine has been drawn based on a survey of av...
潜艇的设计第2部分-潜艇的形状
Some Aspects of Submarine Design Part 2. Shape of a Submarine 2026 Prof. P. N. Joubert 1 1University of Melbourne Defence Science and Technology Organisation DSTO–TR–1920 ABSTRACT A shape for a next generation submarine has been drawn based on a survey of available knowledge. The reasons for each detailed portion of the shape are explained. The aim of the design is to produce a submarine with minimum practical resistance and with minimum water flow noise especially over the forward passive sonar while still carrying out all its normal functions. It is assumed the role of the submarine would be little different from the current vessel but may be powered differently and carry different equipment. The diameter of the hull has been increased while the length has been decreased compared to the present vessel. It is estimated the comparative resistance will be reduced by ten percent. The larger diameter will allow an extra deck over a portion of the length of the vessel giving greater flexibility to internal arrangements. All openings in the first five metres of the shape have been moved elsewhere including the torpedo tubes and interceptor array, to give the smoothest possible flow over the forward passive sensors. The nose shape is derived from a NACA forebody with a 14.2 percent thickness-length ratio and shows a favourable value of the minimum pressure over its length. The question of achieving natural laminar flow over this short length is discussed and found to be possible but is unproven. APPROVED FOR PUBLIC RELEASE DSTO–TR–1920 Published by Defence Science and Technology Organisation 506 Lorimer St, Fishermans Bend, Victoria 3207, Australia Telephone: (03) 9626 7000 Facsimile: (03) 9626 7999 c© Commonwealth of Australia 2006 AR No. 013-761 December, 2006 APPROVED FOR PUBLIC RELEASE ii UNCLASSIFIED DSTO–TR–1920 Some Aspects of Submarine Design Part 2. Shape of a Submarine 2026 EXECUTIVE SUMMARY In about the year 2026, the present class of Australian submarines, the Collins class, will be approaching obsolescence. The machinery, the structure, communications, sensors, weaponry will need updating and replacing and the hull structure will have reached the end of its design life. This represents an opportunity to improve certain aspects of the design which is only possible with a new vessel. One of the most important aspects of submarine operation is to move as silently as possible and to be able to detect others with passive sonar. Consequently this exercise in developing the shape of a new design has three aims, 1) to move as silently as possible with the lowest practical resistance, thus giving a greater top speed and less fuel consumption at transit speeds, 2) to give the best possible flow over the forward passive sonar and 3) a more flexible interior volume with more deck space. All this should be possible without in any way compromising all the other functions and operations. A shape is shown with the best practical ratio of length-to-diameter which gives the minimum resistance. The diameter has been increased while the length has been decreased compared to Collins. The increase in diameter allows an extra deck over portion of the length of the vessel but should not increase the draft to a limit which would interfere with navigation in ports or when docking. It will add to the minimum depth for dived operations where a mission justifies risking the submarine. It will also add to the minimum operational depth of water which enables a submarine to duck under a ship. In order to maintain the same diving depth as Collins, the frames need to stronger. This should be accomplished by deeper webs. A mathematically derived nose shape has been drawn which maintains perfect symme- try over the first five meters from the nose. This shape should give the planned pressure distribution and properly constructed to the finest tolerances, will probably give laminar flow in this region. The passive sonar would then have superior capabilities. The problems with maintaining laminar flow are discussed and it does appear feasible. In the event the boundary layer is tripped to turbulence the result will still represent a vast improvement over the present nose shape and flow over the sonar. The construction of the pressure hull follows standard practice, with successive trun- cated cones forming part of the forebody and all the afterbody. A length of parallel mid-body joins the nose and tail. The casing is not formed until aft of station 5000 (5 metres) and the distortion from circular is gradual thus preserving the symmetry of the nose ahead. The casing is blended into the circular hull smoothly without longitudinal valleys. The torpedo tubes have been moved aft from a horizontal line across the nose to two vertical lines on either side with the most forward part of the shutter at station 5000. The turtle back has been shaped in an attempt to minimise lateral pressure variation. Model testing is essential to confirm design changes and to establish measured values for speed-power relationships. It is estimated for equal volumes the total resistance would be reduced by ten percent compared to a shape like Collins. UNCLASSIFIED iii DSTO–TR–1920 Author Prof. Peter Joubert Contractor for Maritime Platforms Division P.N Joubert, a World War II fighter pilot, after demobilisation from the RAAF, studied aeronautical engineering at Sydney University. He then joined CSIRO, where he designed a ra- dio controlled meteorological glider. Subsequently he was ap- pointed as a lecturer in mechanical engineering at Melbourne University specialising in fluid mechanics. In 1954 he attended the MIT where he built and tested high-speed catamarans in the towing tank. At Melbourne University he built a new wind tunnel and much research was initiated and conducted there. He has authored over 120 scientific papers, most of them in fluid mechanics, boundary layers, roughness, and vortices and recently with a PhD student, the flow about a submarine body in a turn. Over the years he has received many research grants including one from the US Navy. His work with his students and colleagues is recognised internationally such as by the Gen- eral Motors Research Laboratories and other international ship research bodies. He has been studying flow patterns on sub- mersibles since 1998 and has helped with certain modifications to Collins. In 1972 he was granted a personal chair and since retirement has been invited to continue as a Professorial Fel- low. He was awarded a medal in the Order of Australia in 1996 for contributions to road and yacht safety. He was awarded the AGM Michell medal in 2001 by the College of Mechanical Engineers and is a Fellow of the Australian Academy of Tech- nological Science and Engineering. In 2005 he was awarded an honorary Doctorate of Engineering by the University of Mel- bourne for his distinguished eminence. As a yacht designer he has had over 100 yachts built to his designs, including a high- speed catamaran for the world sailing speed record and ocean racing yachts. Some of these have won against world-class com- petition, the Sydney-to-Hobart race in 1983 and second places in 1968, 2002 and 2003. As a sailor he has raced his own de- signs in 27 Sydney-to-Hobart races and survived the storm of 1998. In 1993 he was awarded the Commodore’s medal of the Cruising Yacht Club of Australia for outstanding seamanship after his crew had rescued eight survivors from a sunken yacht at night in a strong gale. v DSTO–TR–1920 Contents Glossary ix 1 Introduction 1 2 Criteria for Optimum Shape of a Submarine 2 2.1 Cross-Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Length-to-Diameter Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.3 Surface Roughness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.4 Prismatic Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.5 Limitations on Draft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.6 Diving Depth (Critical Pressure) . . . . . . . . . . . . . . . . . . . . . . . 5 2.7 Number of Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Length of 2026 7 4 Flow Over the Nose 7 4.1 Torpedo Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 4.2 Intercept Array . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.3 Natural Laminar Boundary Layers at High Reynolds Number . . . . . . . 9 4.4 Possibilities for Natural Laminar Flow . . . . . . . . . . . . . . . . . . . . 11 4.5 Prediction of Transition . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.6 Nose Shape for 2026 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.7 Construction Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.8 Factors Against Laminar Flow . . . . . . . . . . . . . . . . . . . . . . . . 16 4.9 Boundary Layer Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 4.10 Symmetrical:Asymmetrical Nose shape . . . . . . . . . . . . . . . . . . . . 17 5 Aft Body Shape 17 6 Design of the Sail 18 7 Control Surfaces 19 7.1 Stability and Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 8 Profile of 2026 19 vii DSTO–TR–1920 9 Discussion 21 References 23 Appendices A Circularity 25 Figures 1 Drag components for constant volume form. . . . . . . . . . . . . . . . . . . . 3 2 Total resistance components for bare hull showing effect of change in prismatic coefficient. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Number of decks with hull diameter. Also useful deck area. . . . . . . . . . . 6 4 Number of decks with hull diameter. . . . . . . . . . . . . . . . . . . . . . . . 6 5 Externally positioned intercept array. . . . . . . . . . . . . . . . . . . . . . . . 10 6 Profiles of high speed Dolphin body and proposed X-35. . . . . . . . . . . . . 11 7 Instability points on two-dimensional elliptic cylinders and Re. . . . . . . . . 13 8 Pressure distribution on forebodies with contours according to NACA section. 15 9 Profiles of 2026 and Collins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 viii DSTO–TR–1920 Glossary AIP Air Independent Propulsion CSIRO Commonwealth Scientific and Industrial Research Organisation MPD Maritime Platforms Division NACA National Advisory Council of Aeronautics (forerunner to NASA) NASA National Aeronautical and Space Administration RAAF Royal Australian Air Force SSPA Swedish Maritime Research Laboratory µ Fluid viscosity ρ Fluid density A Surface area D Body diameter Ff Friction force L Body length U∞ Freestream fluid velocity Re Reynolds number, a ratio of fluid inertial and viscous forces, = ρU∞Lµ Rex Local value of Reynolds number, usually measured at transition point Cp Pressure Coefficient = Pressure1 2 ρU2∞ Cf Skin-friction Coefficient = Ff 1 2 ρU2∞A CP Prismatic Coefficient = Displaced Volume Midship Area×Waterline Length t Sail thickness c Sail chord (length) ix DSTO–TR–1920 1 Introduction Considering a replacement design for the Collins Class Submarine which might be required about the year 2026, at this time of writing, the operational tasks required of this submarine would not appear to be greatly different to what was listed in the report of December 2003, [1]. If the tasks are altered then of course the design will need to be altered. What is discussed here is preliminary; it is intended that it may form a basis for what eventually is decided. It is highly likely the range requirements would be at least as large as Collins (10,000 nautical miles) and probably extended given the expanded area of interest flagged in the Minister’s Defence update 15 December 2005. It would be highly desirable if the transit speed could be increased to minimise time lost in transit. The type of power unit must be left to later developments. AIP may have possibilities. Nuclear power would allow a fast transit but is not yet acceptable in Australia. Diving depth is a most important variable and some designs have gone to much trouble and expense in order to achieve the deepest possible operating depth. Whether this feature needs to be altered I cannot say, but it will be assumed that there is no change required. In which case the pressure hull can be ended with flat bulkheads as with Collins Class. A deeper diving depth would require domed end closures which present greater difficulties to construct (Daniel [3]). The whole submarine then becomes more expensive. The greater depth would require a stronger hull and as a result the hull weight would be increased leaving less available for fuel, machinery and other items. This in turn means a slower vessel. One makes a design choice and suffers the consequences. Weaponry is being altered on a continuous basis. Launch systems which allow the use of stand-off land attack missiles, surface to air missiles and anti-ship missiles will probably need to be considered and included. The ability to carry and launch unmanned underwater vehicles will be part of the wish list as will likely be the operational support of special operations forces. Detection and communications are being improved constantly. Covert forward intel- ligence gathering and surveillance is an important activity and it is equally important to be able to communicate this information. The ability to communicate real time data with voice transfer would surely be an aim. Sloan [2] discusses some of these factors from the designers vewpoint. At some stage decisions are made, the design is commenced and thereafter the process becomes difficult to alter in any major way. The aim of this design study is to produce a shape with the following features, 1. Minimum resistance within all other design constraints, thus increasing cruising range, top speed and reducing fuel consumption. 2. Minimum flow noise especially over the forward sonar and other sensors. 3. A flexible interior giving most deck space for a given volume. 1 DSTO–TR–1920 2 Criteria for Optimum Shape of a Submarine Gertler, in 1950 [10], reported the results of resistance experiments on a systematic series of twenty four mathematically related streamlined bodies of revolution, showing how the resistance of these bodies at deep submergence varies with changes in five selected geometrical parameters. These geometrical parameters were the fineness ratio, prismatic coefficient, nose radius, tail radius and the position of the maximum section. Before this work was undertaken there was no systematic data on the resistance of streamlined forms deeply submerged in a fluid. The series forms were compared on an equal volume basis including the estimated added resistance due to control surfaces necessary for prescribed directional stability char- acteristics. These comparisons indicated that there is a large variation in submerged resistance among these forms and that there is a definite minimum resistance on each parameter variation except for the nose radius. These test results formed the basis for the choice of the shape of the USS Albacore [25], whose construction was authorised in 1951. This experimental vessel was the forerunner of all successful US Navy submarines such as Barbel and Skipjack. 2.1 Cross-Section To withstand the high pressures on the hull at depth, the most efficient structural shape with the lowest stresses is one of circular cross-section. Departures from absolute circularity have to be minimised as discussed by Capt. H. E. Saunders [4], otherwise early failures can result (see Appendix A). The circle has the lowest wetted surface for a given contained volume so this is an advantage for underwater resistance. For surface travel the circle contributes no hull form stability which is a disadvantage especially when a vessel rises to the surface with water in the voids of the sail and casing thus momentarily increasing the height of the centre of mass and decreasing the stability margin. 2.2 Length-to-Diameter Ratio The ratio of length-to-diameter bears a strong effect on the total resistance. The two main portions of the underwater resistance of the bare hull are due to pressure drag (sometimes called form drag) and skin friction. The pressure drag is created by the streamlines on the rear of the body being displaced from the geometric surface by the thickening boundary layer. Consequently the rise in pressure near the tail of the body as the streamlines widen, is not as great as would occur without a boundary layer. This imbalance between nose and tail produces a nett pressure force on the submarine creating a drag force. Skin friction drag acts tangentially at the surface and is proportional to the wetted surface. The more wetted surface the greater the skin friction. Therefore if the displaced 2 DSTO–TR–1920 Drag Total SkinFriction PressureDrag Length:DiameterRatio 6 10 Figure 1: Drag components for constant volume form. volume of the submarine is contained in a long thin shape, then the skin friction is greater than for a shorter, beamier shape of the same volume which has less wetted surface. The variation in the two components of resistance, pressure drag and skin friction, looks like the plot in Figure 1. The combined resistance shows a minimum at about L/D of 6 to 7; the curve has no defined minimum being almost horizontal in this range. It is proposed that a new shape be considered of shorter length and greater diameter which will reduce the total drag coefficient closer to the ideal. 2.3 Surface Roughness The main factor, apart from surface area, which affects the skin friction resistance is the roughness of the surface. It is important that designers limit the effects of surface openings, raised edges, recessed joins (shutters), lateral arrays and other features which cause added resistance. 2.4 Prismatic Coefficient The prismatic coefficient defines the amount of volume in the ends of the submarine. It is formed as the ratio of the displaced volume with that contained in a prism formed by the 3 DSTO–TR–1920 mid-ship cross-sectional area and the length. The variation of the submerged resistance with this parameter can be significant (see Figure 10 in Gertler [10]). R. J. Daniel in his paper on submarine design [3] suggests an optimum value of about 0.6 (also shown in Gertler). Collins has a prismatic coefficient greater than 0.8, while the new shape for 2026 calculates as 0.76. The variation of the resistance with change in prismatic is shown by Arentzen and Mandel [6] in their Figure 6. Figure 2 shows this variation. The combined effect of the reduction in L/D and CP should give a reduction in total resistance coefficient of over eight percent. Figure 2: Total resistance components for bare hull showing effect of change in prismatic coefficient (Arentzen and Mandel [6]). 4 DSTO–TR–1920 2.5 Limitations on Draft It should be possible to increase the floating draft of a submarine to greater than that of Collins, which is nominally 7.0 metres, and still be able to navigate the important harbours where it docks and berths. The weight of any new vessel needs to be established early in the design. Hence the floating draft can be established from the displaced volume required to support this weight added to all the other loadings. Arentzen and Mandel [6] suggest that 36 feet (10.98 metres) is the upper practical limit for the diameter of a military submarine which would have a draft of 30 feet (9.14 metres). Of more importance is the operational requirement of a dived intrusion in shallow water where the submarine may be at risk. The bottom clearance plus the hull diameter with the casing height plus the fin and periscope heights are now increased by the larger hull diameter. A similar i
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