船舶設計外文翻譯---船舶在開敞水域和受限航道的坐底現(xiàn)象

1、<p><b>　　附錄二、外文翻譯</b></p><p>　　<文獻翻譯一：原文></p><p>　　ship squat in open water and in confined channels</p><p>　　What exactly is ship squat?</p><p>

2、　　When a ship proceeds through water, she pushes water ahead of her. In order not to leave a ‘hole’ in the water, this volume of water must return down the sides and under the bottom of the ship. The streamlines of retur

3、n flow are speeded up under the ship. This causes a drop in pressure, resulting in the ship dropping vertically in the water. </p><p>　　As well as dropping vertically, the ship generally trims for’d or aft.

4、Ship squat thus is made up of two components, namely mean bodily sinkage plus a trimming effect. If the ship is on even keel when static, the trimming effect depends on the ship type andbeing considered. </p><

5、p>　　The overall decrease in the static underkeel clearance (ukc), for’d or aft, is called ship squat. It is not the difference between the draughts when stationary and the draughts when the ship is moving ahead. </

6、p><p>　　If the ship moves forward at too great a speed when she is in shallow water, say where this static even-keel ukc is 1.0–1.5 m, then grounding due to excessive squat could occur at the bow or at the ster

7、n.</p><p>　　For full-form ships such as Supertankers or OBO vessels, grounding will occur generally at the bow. For fine-form vessels such as Passenger Liners or Container ships the grounding will generally

8、occur at the stern. This is assuming that they are on even keel when stationary.</p><p>　　If is >0.700, then maximum squat will occur at the bow.</p><p>　　If is <0.700, then maximum squat

9、 will occur at the stern.</p><p>　　If is very near to 0.700, then maximum squat will occur at the stern, amidships and at the bow. The squat will consist only of mean bodily sinkage, with no trimming effect

10、s.</p><p>　　It must be generally, because in the last two decades, several ship types have tended to be shorter in length between perpendiculars (LBP) and wider in Breadth Moulded (Br. Mld). This has lead to

11、 reported groundings due to ship squat at the bilge strakes at or near to amidships when rolling motions have been present. </p><p>　　Why has ship squat become so important in the last 40 years?</p>&

12、lt;p>　　Ship squat has always existed on smaller and slower vessels when under-way. These squats have only been a matter of centimetres and thus have been inconsequential.</p><p>　　However, from the mid-19

13、60s to this new millennium, ship size steadily has grown until we have Supertankers of the order of 350 000 tonnes dead-weight (dwt) and above. These Supertankers have almost out-grown the Ports they visit, resulting in

14、small static even-keel ukc of only 1.0–1.5 m.</p><p>　　Alongside this development in ship size has been an increase in service speed on several ships, e.g. Container ships, where speeds have gradually increa

15、sed from 16 up to about 25 kt.</p><p>　　Ship design has seen tremendous changes in the 1980s and 1990s. In Oil Tanker design we have the ‘Jahre Viking’ with a dwt of 564 739 tonnes and an LBP of 440 m. This

16、is equivalent to the length of five football pitches.</p><p>　　In 2002, the biggest Container ship to date, namely the ‘Hong Kong Express’ came into service. She has a dwt of 82 800 tonnes, a service speed o

17、f 25.3 kt, an LBP of 304 m, Br. Mld of 42.8 m and a draft moulded of 13 m.</p><p>　　As the static ukc have decreased and as the service speeds have increased, ship squats have gradually increased. They can n

18、ow be of the order of 1.50-1.75m, which are of course by no means inconsequential.</p><p>　　Department of Transport ‘M’ notices</p><p>　　In the UK, over the last 20 years the UK Department of Tr

19、ansport have shown their concern by issuing four ‘M’ notices concerning the problems of ship squat and accompanying problems in shallow water. These alert all Mariners to the associated dangers.</p><p>　　Sig

20、ns that a ship has entered shallow water conditions can be one or more of the following:</p><p>　　1. Wave-making increases, especially at the forward end of the ship.</p><p>　　2. Ship becomes mo

21、re sluggish to manoeuvre. A pilot’s quote … ‘a(chǎn)lmost like being in porridge.’</p><p>　　3. Draught indicators on the bridge or echo sounders will indicate changes in the end draughts.</p><p>　　4.

22、Propeller rpm indicator will show a decrease. If the ship is in ‘open water’ conditions, i.e. without breadth restrictions, this decrease may be up to 15% of the Service rpm in deep water. If the ship is in a confined ch

23、annel, this decrease in rpm can be up to 20% of the service rpm.</p><p>　　5. There will be a drop in speed. If the ship is in open water conditions this decrease may be up to 30%. If the ship is in a confine

24、d channel such as a river or a canal then this decrease can be up to 60%.</p><p>　　6. The ship may start to vibrate suddenly. This is because of the entrained water effects causing the natural hull frequency

25、 to become resonant with another frequency associated with the vessel.</p><p>　　7. Any rolling, pitching and heaving motions will all be reduced as ship moves from deep water to shallow water conditions. Thi

26、s is because of the cushioning effects produced by the narrow layer of water under the bottom shell of the vessel.</p><p>　　8.Turning circle diameter (TCD) increases. TCD in shallow water could increase 100%

27、.</p><p>　　9. Stopping distances and stopping times increase, compared to when a vessel is in deep waters.</p><p>　　10. Rudder is less effective when a ship is in shallow waters.</p><

28、p>　　What are the factors governing ship squat?</p><p>　　The main factor is ship speed V. Detailed analysis has shown that squat varies as speed to the power of 2.08. However, squat can be said to vary app

29、roximately with the speed squared. In other words, we can take as an example that if we have the speed we quarter the squat. Put another way, if we double the speed we quadruple the squat!!</p><p>　　In this

30、context, speed V is the ship’s speed relative to the water. Effect of current/tide speed with or against the ship must therefore be taken into account.</p><p>　　Another important factor is the block coeffici

31、ent CB. Squat varies directly with CB. Oil Tankers will therefore have comparatively more squat than Passenger Liners.</p><p>　　Procedures for reducing ship squat</p><p>　　1. Reduce the mean dra

32、ft of the vessel if possible by the discharge of water ballast. This causes two reductions in one:</p><p>　　(a) At the lower draft, the block coefficient CB will be slightly lower in value, although with Pas

33、senger Liners it will not make for a signifi-cant reduction. (b) At the lower draft, for a similar water depth, the H/T will be higher in value. It has been shown that higher H/T values lead to smaller squat values.</

34、p><p>　　2. Move the vessel into deeper water depths. For a similar mean ship draft, H/T will increase, leading again to a decrease in ship squat.</p><p>　　3. When in a river if possible, avoid inte

35、raction effects from nearby moving ships or with adjacent riverbanks. A greater width of water will lead to less ship squat unless the vessel is outside her width of influence.</p><p>　　4. The quickest and m

36、ost effective way to reduce squat is to reduce the speed of the ship. </p><p>　　False drafts</p><p>　　If a moored ship’s drafts are read at a quayside when there is an ebb tide of say 4 kt then

37、the draft readings will be false. They will be incorrect because the ebb tide will have caused a mean bodily sinkage and trimming effects. In many respects this is similar to the ship moving forward at a speed of 4 kt. I

38、t is actually a case of the squatting of a static ship.</p><p>　　It will appear that the ship has more tonnes displacement than she actually has. If a Marine Draft Survey is carried out at the next Port of C

39、all (with zero tide speed), there will be a deficiency in the displacement ‘constant.’ Obviously, larger ships such as Supertankers and Passenger Liners will have greater errors in displacement predictions.</p>&l

40、t;p><b>　　Summary</b></p><p>　　In conclusion, it can be stated that if we can predict the maximum ship squat for a given situation then the following advantages can be gained:</p><p&

41、gt;　　1. The ship operator will know which speed to reduce to in order to ensure the safety of his/her vessel. This could save the cost of a very large repair bill. It has been reported in technical press that the repair

42、bill for the QEII was $13 million … plus an estimate for lost Passenger bookings of $50 million!!</p><p>　　2. The ship officers could load the ship up an extra few centimetres (except of course where load-li

43、ne limits would be exceeded). If a 100 000 tonnes dwt Tanker is loaded by an extra 30 cm or an SD14 General Cargo ship is loaded by an extra 20 cm, the effect is an extra 3% onto their dwt. This gives these ships extra e

44、arning capacity.</p><p>　　3. If the ship grounds due to excessive squatting in shallow water, then apart from the large repair bill, there is the time the ship is ‘out of service’. Being ‘out of service’ is

45、indeed very costly because loss of earnings can be as high as £100 000 per day.</p><p>　　4. When a vessel goes aground there is always a possibility of leakage of oil resulting in compensation claims fo

46、r oil pollution and fees for clean-up operations following the incident. These costs eventually may have to be paid for by the shipowner.</p><p>　　備注：Dr C.B.Barrass．Ship Design and Perfor

47、mance for Masters and Mates[M]．Butterworth-Heinemann，2004．148~179</p><p>　　<文獻翻譯一：譯文></p><p>　　船舶在開敞水域和受限航道的坐底現(xiàn)象</p><p>　　什么是船舶的坐底現(xiàn)象?</p><p>　

48、　當船舶在水中向前航行時，她會推開在船首的水。為了不使得在船首處水中形成一個”空洞”，這個排開的水必須返回船舷兩側(cè)和船底。返回的水流流線在船底加速。這導致了船底壓力下降，使得船舶在水中垂直下沉。</p><p>　　除了船底垂直下沉外，船舶一般表現(xiàn)為首傾或者尾傾。船舶坐底由兩部分組成，即船體下沉加上一個縱傾影響。如果船舶靜態(tài)時是平吃水，船舶的縱傾效應取決于船型和船舶的方形系數(shù)。</p><p&

49、gt;　　在靜態(tài)時船底富余水深整體上減少，不論船首和船尾，被稱為船舶坐底。這在船舶靜態(tài)時吃水和前進中吃水沒有差異。</p><p>　　如果船舶在淺水域中以很大的速度航行的話，比如過船舶靜態(tài)時船底富余水深為1.0至1.5米，那么由于過度的坐底可能使得船首或者船尾發(fā)生觸底。</p><p>　　對于肥大型船舶，比如超級油輪或礦砂船，船舶觸底一般發(fā)生在船首。對諸如定線客船或集裝箱船，觸底一般發(fā)

50、生在船尾。這只是假設在靜止時船舶表現(xiàn)為平吃水。</p><p>　　如果大于0.700，那么最大下沉將出現(xiàn)在船首</p><p>　　如果小于0.700，那么最大下沉將出現(xiàn)在船尾</p><p>　　如果非常接近0.700，那么最大下沉將出現(xiàn)在船尾、船中和船首。這里的船舶坐底只考慮了船體下沉而沒有考慮船舶縱傾的影響。</p><p>　　這必

51、須是普遍的，因為在過去的二十年，幾個船型往往趨向于垂線間長變短和船寬變大。這導致了當船舶存在橫搖時因坐底使得船中處擱淺。</p><p>　　為什么船舶坐底現(xiàn)象近40年來變得這么嚴重？</p><p>　　船舶坐底總是存在于較小和較慢的在航船舶。這些下沉僅數(shù)厘米，因此也就無關緊要了。</p><p>　　然而，從60年代中期到這個新千年，船舶的規(guī)模穩(wěn)步增長，直到我們

52、擁有了350000噸及以上載重噸的超級油輪。這些超級油輪在其訪問的港口即使是在小靜態(tài)時平吃水也只有1.0到1.5的富余水深。</p><p>　　除了船型的不斷發(fā)展，船舶的速度也在不斷增長。例如集裝箱船，其速度已經(jīng)逐漸從注冊時的16節(jié)增至現(xiàn)在的25節(jié)。</p><p>　　船舶設計在20世紀80年達和90年代發(fā)生了巨大的變化。油輪的設計，我們擁有了564739載重噸的Jahre Vikin

53、g號，其垂線間長達到440米。這相當于五個足球場的長度。</p><p>　　在2002年，迄今為止最大的集裝箱船，即”香港快運”投入使用。載重噸82800，航速25.3節(jié)，垂線間長304米，船寬42.8米，吃水13米。</p><p>　　由于靜態(tài)時船底龍骨下富余水深的減少和船速的增加，船舶坐底現(xiàn)象逐漸增多。他們現(xiàn)在可以在1.50到1.75米之間，這當然絕不是無關緊要的。</p&g

54、t;<p><b>　　運輸部”M”的通知</b></p><p>　　在英國，過去20年，英國運輸部已發(fā)出的”M”通知有關船舶坐底和船舶淺水航行時所有的影響問題。這些警告所有和船員相關的危險。</p><p>　　船舶進入淺水域?qū)⒂幸粋€或者多個以下現(xiàn)象：</p><p>　　波浪的作用增加，特別是船首波。</p>

55、<p>　　船舶操縱變得更加遲緩。一個引航員的說法...就像在粥里。</p><p>　　在橋上的吃水指示或回聲測深儀的回波將最終確定吃水的變化。</p><p>　　螺旋槳轉(zhuǎn)速指示器將明顯減少。如果該船在開敞水域，例如沒有寬度的限制，這種減少將高達額定轉(zhuǎn)速的15%，而如果在受限航道，這中轉(zhuǎn)速減少量將高達額定轉(zhuǎn)速的20%。</p><p>　　同時也將有船

56、速的下降。如果在開敞水域，船速下降高達30%。如果在受限航道，船速下降則高達60%。</p><p>　　船體開始突然震動。這是因為夾帶的水造成的自然頻率，和船舶相關的另一種頻率的共振效應。</p><p>　　任何的橫搖，縱搖和首搖運動將會減輕，從深水駛?cè)霚\水時。這是因為船底的狹小空間起到了緩沖作用。</p><p>　　回旋半徑增加，在淺水中將增加一倍。<

57、/p><p>　　與深水中相比，船舶制動距離和停車次數(shù)增加。</p><p>　　在淺水域中舵效變差。</p><p>　　船舶坐底與那些因素有關?</p><p>　　主要因素是船速。詳細的分析表明船舶下沉變化隨著速度的變化而變化。然而，下沉量的變化可以說與船速的平方相近。換言之，我們可以以此為例子，如果我們的速度下降一半，下沉量為四分之一；如

58、果速度提高一倍，則下沉兩將翻一翻。在這種情況下，船速為對水速度。因此，對于當前船舶的影響，還要考慮潮流的速度。另一個重要的因素是船舶的方形系數(shù)，船體下沉量與船舶方形系數(shù)成正比。油輪因此比客輪下沉更多。</p><p><b>　　減少船舶坐底的過程</b></p><p>　　1.如果可能的話，通過排放壓載水來減少船舶的平均吃水。這將導致兩個中的一個減少：</p

59、><p>　?。ㄒ唬┰诔运^小時，方形系數(shù)的值將會略微下降，但與客輪相比不會有一個明顯的減少。</p><p>　?。ǘ┰诔运^小時，對于相對水深來講，H/T值將增加。它已表明，H/T值增加將使得船舶坐底降低。</p><p>　　2.船舶開至更深的水域。對于類似的平均吃水和H/T值的增加將導致船舶坐底進一步降低。</p><p>　　3.當在

60、一條河流中，如果可能的話，避免鄰近船只和岸壁的影響。航道寬度越大船舶坐底將越小，除非該船只在航道的影響寬度內(nèi)。</p><p>　　4.最快捷和有效地方法是減小船速來降低坐底。</p><p><b>　　負吃水</b></p><p>　　如果一系泊船的吃水從岸邊看時，當存在落潮流為4節(jié)時，讀出來的吃水是錯誤的。他們將不正確是因為落潮會造成船

61、舶下沉和縱傾。在很多方面相當于船舶正以4節(jié)的速度前進。實際上它是一個船舶靜態(tài)的下沉。</p><p>　　船舶將會表現(xiàn)為比實際排水量要大的噸數(shù)。如果在下一個港口開展吃水調(diào)查（零潮速），將會有一個不足之處是位移不變。顯然，這樣超級油輪和定期客船將有較大的預測誤差。</p><p><b>　　綜述</b></p><p>　　總之，可以說，如果我

62、們可以預測船舶在特定情況下的最大下沉量，那么我們得到的以下好處便會增加：</p><p>　　船舶駕駛員便會知道船速降到多少能夠確保船舶的安全。這可以節(jié)省一大筆的修理費。據(jù)報道，QEII的維修費為1300萬美元...外加5000萬美元的旅客預訂損失。</p><p>　　船員可以額外的增加幾厘米吃水（當然除了在載重線的限制將被超出外）。</p><p>　　如果由于