航向穩(wěn)定性和回轉(zhuǎn)性邱磊講解課件

1、船舶操縱性與耐波性第2章 航向穩(wěn)定性和回轉(zhuǎn)性邱磊qiu-船舶操縱性與耐波性課件船舶有哪些操縱方面的性能？1固有動穩(wěn)性(也稱直線運動穩(wěn)定性)(Inherent dynamic stability, also called straight line stability)2方向穩(wěn)定性或保向性(Course-keeping ability, also called directional stability)3初始轉(zhuǎn)首性能(Initial turning/course-changing ability)4偏轉(zhuǎn)抑制性能(Yaw checking ability)5回轉(zhuǎn)性能(Turning abilit

2、y)-大舵角下6停船性能(Stopping ability)船舶操縱性與耐波性課件固有動穩(wěn)性(直線運動穩(wěn)定性)船舶操縱性與耐波性課件航向穩(wěn)定性能(保向性)船舶操縱性與耐波性課件初始轉(zhuǎn)向性能與航行安全的關(guān)系船舶操縱性與耐波性課件回轉(zhuǎn)性能與航行安全的關(guān)系船舶操縱性與耐波性課件停船操縱 - 停船性能船舶操縱性與耐波性課件第二章 航向穩(wěn)定性和回轉(zhuǎn)性1. 航向穩(wěn)定性2. 船舶回轉(zhuǎn)性3. 回轉(zhuǎn)運動的耦合特性船舶操縱性與耐波性課件第二章 航向穩(wěn)定性和回轉(zhuǎn)性穩(wěn)定性的概念：對處于定常運動狀態(tài)的物體(或系統(tǒng))，若受到極小的外界干擾作用而偏離原定常運動狀態(tài)；當干擾去除后，經(jīng)過一定的過渡過程，看是否具有回復(fù)到原定常運

3、動狀態(tài)的能力。若能回復(fù)，則稱原運動狀態(tài)是穩(wěn)定的。(a)直線運動穩(wěn)定性(b)方向穩(wěn)定性(c)位置穩(wěn)定性船舶操縱性與耐波性課件Directionally unstable shipsAn increasing number of new ships are directionally unstable under certain conditions of trim and are difficult to steer manuallySteady steering is only achieved by continually applying small short alternating h

4、elm actionsDespite its problems, directional instability does allow a ship to make tight turnsBut it is important that the pilot or master is familiar with the ships behaviour and plans an alter course to allow for this船舶操縱性與耐波性課件影響方向穩(wěn)定性的因素(Factors affecting directional stability)Neither the centre

5、of the hydrodynamic hull force, point A, nor the neutral steering point (N0) are fixed in position for a single vesselThe location of N0 depends uponthe centripetal force relative to the turning moment required for a given rate of turn and hullformThe position of A depends upon壓力足以的位置取決于：the flow co

6、nditions around the immersed hullformits fore and aft distribution of surface areaSo, the main factors affecting the directional stability are影響方向穩(wěn)定性的主要因素有:Trim 縱傾Hullform 船型ahead speed 前進速度船舶操縱性與耐波性課件How does trim affect the directional stability?Both head and stern trim increase the ships moment o

7、f inertia 首傾和尾傾都增大了船舶的慣性矩So the required moment for a given rate of turn is increased by trim and the point N0 is moved further forwardMore important is that the trim also alters the fore and aft distribution of immersed hull surface and thus the position of A (see next page)更為重要的是縱傾也改變了首尾濕表面積的分布和壓力

8、中心A的位置stern trimhead trim船舶操縱性與耐波性課件Stern trim moves A further aft Point A is well aft of the N0-pointso the ship needs a large helm force to maintain the turn the ship will steady up quickly with midships helmThus, directional stability is increasedHead trim moves A further aheadPoint A is just aft

9、 of the N0-pointso only a small helm force is needed to maintain the turnbut the ship will be slow to steady up with midships helmThus, directional stability is decreased船舶操縱性與耐波性課件How does the hullform affect the directional stability?Moderately high CB-hulls have a relatively large moment of inert

10、ia about the vertical axes so point N0 will tend to be further forward than for finer lined shipsVery full-bodied hulls: point A tends to be even further forward than N0 so these ships are likely to be directionally unstable at small rudder anglesThe swing of the ship can distort the boundary layer

11、to the extent that flow is directed to the wrong side of the rudder and the rudder force is reversed船舶操縱性與耐波性課件How does the ships ahead speed affect directional stability?Increasing a ships ahead speed for a given rudder angle will move the N0-point further aft, thus the directional stability is dec

12、reasedA reduction in speed thus tends to increase a ships directional stability for a given rudder angleBut if the ship is moving too slow there will be insufficient flow for the rudder to be effective and the ship has lost “steerage way”.船舶操縱性與耐波性課件The directional stability can be improved by using

13、 more “deadwood” at the stern 在船尾安裝呆木analogous to the feathers on an arrow or dart!Examples of ways of increasing the deadwoodSkegs 尾鰭Fixed fins (submarine “stabilizers”) 穩(wěn)定鰭Other stern appendages 其他附體Ways of improving directional stability如何提高方向穩(wěn)定性？船舶操縱性與耐波性課件第二章 航向穩(wěn)定性和回轉(zhuǎn)性物體的運動狀態(tài)是否穩(wěn)定，不僅取決于物體的性質(zhì)，也取決

14、于所考察的運動狀態(tài)和運動參數(shù) 1需針對某運動狀態(tài)，或某一運動參數(shù)來分析其穩(wěn)定性 2具有位置穩(wěn)定性的船舶必具有直線穩(wěn)定性和方向穩(wěn)定性；具有方向穩(wěn)定性的船舶必具有直線穩(wěn)定性 3按是否操舵，穩(wěn)定性又分為自動(固有)穩(wěn)定性(取決于 船體幾何)和控制穩(wěn)定性(取決于閉合回路) 4對于通常的水面艦船，若不操舵，不具備方向穩(wěn)定性和位置穩(wěn)定性，最多具有直線穩(wěn)定性，也可能不具穩(wěn)定性 5對穩(wěn)定性概念的理解船舶操縱性與耐波性課件(2-1)小擾動方程為對穩(wěn)定性作定量分析，采用“運動穩(wěn)定性理論”分析方法。設(shè)船舶初始運動狀態(tài)：u1=const=U, v1=r1=0.擾動后引起的擾動運動參數(shù)：由于對初始狀態(tài)是小擾動，故可采用

15、線性操縱運動方程(1-25)式來描述。因不操舵， .將式(2-1)代入式(1-25)，(1-25)船舶操縱性與耐波性課件其中，第一式與后兩式無關(guān).第一式可重寫為：小擾動方程即可求得小擾動方程：(2-2)(2-3)第一式對應(yīng)的特征方程為：船舶操縱性與耐波性課件小擾動方程特征根為：故式(2-3)的解為： 總為負值，故對縱向速度擾動總具有穩(wěn)定性。因此，船舶在水平面內(nèi)的航向穩(wěn)定性主要取決于方程(2-2)的后二式。分母為正，分子為負。(2-4)(2-5)(2-3)船舶操縱性與耐波性課件二元一階常系數(shù)微分方程組(2-7)(2-8)(2-6)小擾動方程船舶操縱性與耐波性課件特征方程特征根角速度擾動方程(2-

16、7)的解為:(2-9)(2-10)速度v的小擾動方程的解為:(2-11)船舶操縱性與耐波性課件航向穩(wěn)定性分析接下來我們進行航向穩(wěn)定性分析其根為：于是有：可見：船舶操縱性與耐波性課件航向穩(wěn)定性分析皆為負實部的必要條件是：兩根將皆為實數(shù)，且必有一個正根船舶操縱性與耐波性課件航向穩(wěn)定性分析皆為負實部的必要條件是：船舶操縱性與耐波性課件航向穩(wěn)定性分析可見，航向穩(wěn)定性條件可歸結(jié)為：船舶操縱性與耐波性課件水動力導(dǎo)數(shù)分析較大的負值不定符號的小量圖2-3當具有橫向加速度擾動時船舶操縱性與耐波性課件不定符號的小量較大的負值圖2-4當具有回轉(zhuǎn)加速度擾動時船舶操縱性與耐波性課件受側(cè)向擾動速度v作用時較大的負值不很大

17、的負值圖2-5船舶操縱性與耐波性課件由角速度r引起的力和力矩不定符號的小量較大的負值圖2-6船舶操縱性與耐波性課件穩(wěn)定性衡準數(shù)C船舶操縱性與耐波性課件穩(wěn)定性衡準數(shù)C船舶操縱性與耐波性課件C0 船舶在水平面的運動具有直線穩(wěn)定性；C Iv 時，船舶具有航向穩(wěn)定性。試驗結(jié)果表明，對一般排水量船舶l(fā)v0 ，即位置力的壓力中心總位于船中前，隨水深變淺，lv 變化不大，而lr 的變化甚大，原因是隨水深變淺，Yr 增加而引起，見圖2-9。圖2-9船舶操縱性與耐波性課件開始操舵時，船舶重心的瞬時位置為回轉(zhuǎn)運動的起始點，稱之為執(zhí)行操舵點?；剞D(zhuǎn)圈的主要特征參數(shù)為： 1)反橫距從船舶初始的直線航線至回轉(zhuǎn)運動軌跡向反

18、方向最大偏離處的距離為S1。 2)正橫距從船舶初始直航線至船首轉(zhuǎn)向90度時，船舶重心所在位置之間的距離為S2。該值越小，則回轉(zhuǎn)性就越好。船舶操縱性與耐波性課件回轉(zhuǎn)圈的主要特征參數(shù)為： 3)縱距從轉(zhuǎn)舵開始時刻船舶重心G點所在的位置，至船首轉(zhuǎn)向90度時船舶縱中剖面，沿原航行方向計量的距離S3。一般船舶縱距約為3、4倍船長。其值越大，表示船舶對初始時刻的操舵反應(yīng)越遲鈍，即應(yīng)舵較慢。船舶操縱性與耐波性課件 4)戰(zhàn)術(shù)直徑從船舶原來航線至船首轉(zhuǎn)向180度時，船縱中剖面所在位置之間的距離DT。其值越小，則回轉(zhuǎn)性越好。對一般普通船DT約為36倍船長，回轉(zhuǎn)性較差者可達78倍船長?；剞D(zhuǎn)圈的主要特征參數(shù)為：船舶操縱

19、性與耐波性課件 5)定?；剞D(zhuǎn)直徑定常回轉(zhuǎn)階段船舶重心點圓形軌跡的直徑D。一般D0.9DT。通常采用相對回轉(zhuǎn)直徑DL代表回轉(zhuǎn)性優(yōu)劣。通常認為回轉(zhuǎn)性好的船，最小相對回轉(zhuǎn)直徑為3左右，回轉(zhuǎn)性差的船約為10左右，大多數(shù)船在57的范圍內(nèi)。回轉(zhuǎn)圈的主要特征參數(shù)為：船舶操縱性與耐波性課件6）進程R自執(zhí)行操舵點起至回轉(zhuǎn)圈中心的縱向距離；R=S3-R；它表示船舶對舵作用的應(yīng)答性，R越小則應(yīng)答性越好，通常R/L數(shù)值約為l2?；剞D(zhuǎn)圈的主要特征參數(shù)為：船舶操縱性與耐波性課件 船舶回轉(zhuǎn)過程中，在船上還存在一個橫向速度分量為零的點，稱為樞心點p，由圖可見，樞心點前后橫向速度反向。一般在初始操舵瞬時，樞心處于船體之撞擊中心

20、，約在船舶重心前1/10船長處。以后隨回轉(zhuǎn)過程的發(fā)展，樞心點位置向船首移動，直至定?；剞D(zhuǎn)狀態(tài)，樞心位置穩(wěn)定在重心前1/61/3船長處。所以，當船舶回轉(zhuǎn)時，若駕駛?cè)藛T站在樞心點p上，則可看到一方面船以Vp速度平移，另一方面船上前后各點以角速度r繞p點旋轉(zhuǎn)。這樣在操縱時可清晰地觀察船舶的運動情況。所以，在條件許可時，駕駛室的位置最好設(shè)在樞心附近。船舶操縱性與耐波性課件回轉(zhuǎn)圈(Turning Circle)最小回轉(zhuǎn)直徑是度量船舶操縱性能的一個重要參數(shù)(The minimum turning diameter is one measure of a ships manoeuvring characte

21、ristics)影響最小回轉(zhuǎn)直徑的因素主要有(The minimum turning diameter varies with, for example):舵角、船速、船舶尺度、水深和縱傾船舶操縱性與耐波性課件影響最小回轉(zhuǎn)直徑的一些因素(Examples of factors effecting the minimum turning diameter)速度(Speed):舵角不變，船速增大，回轉(zhuǎn)圈隨之增大(With constant rudder angle, an increase in speed results in an increased turning circle)船速很低時由

22、于舵效降低回轉(zhuǎn)圈增大Very low speed (those approaching bare steerageway) also increases theturning circle because of reduced ruddereffect 船舶尺度(Vessel size):回轉(zhuǎn)直徑隨著船舶尺度增大而增大(The turning diameter tends to increase with vessel size)水深(Water depth)：水深極淺的情況下，最小回轉(zhuǎn)直徑可能倍增(Minimum turning diameter may more than double i

23、n very shallow water)!Smaller right-handed screw vessels may show a bias in turning a tighter circle to port than to starboard, due to the transverse thrust effectthis effect is often negligible in larger ships船舶操縱性與耐波性課件PROPELLER FORCESLONGITUDINAL THRUSTTRANSVERSE THRUST (SIDE FORCE OR PADDLEWHEEL

24、 FORCE)COUPLE (TWIST)STERN WALKS THE SAME DIRECTION PROPELLER TURNS船舶操縱性與耐波性課件Visualize the lower blades walking along the bottom.Side Force單槳(SINGLE PROPELLER)STERN WALK船舶操縱性與耐波性課件調(diào)距槳CONTROLLABLE PITCH PROPELLERSSTERN WALKS TO STBDFFGDD/CG/MCMDD/CG DEVELOP STERN WAY 0% PITCH AND WHEN TWISTING DDG 5

25、1船舶操縱性與耐波性課件Turning circle - terminology縱距(Advance)Distance gained toward the direction of the original course after the rudder is put over.正橫距(Transfer)Distance gained perpendicular to the original course after the rudder is put over.反橫距(Kick)Momentary movement, at the start of a turn, of the ships

26、 stern toward the side opposite to the direction of the turn定?；剞D(zhuǎn)直徑(Final Diameter)Diameter of the ships turning circle戰(zhàn)術(shù)直徑(Tactical Diameter)Perpendicular distance between the path of the ship on original course and final course after a 180 turn船舶操縱性與耐波性課件樞心點(The pivot point)樞心點是船舶縱中線上的一個點，操舵后船舶繞通過該

27、點的垂軸旋轉(zhuǎn) (A ships (dynamic) pivot point is a point in the centreline about which the ship turns when the rudder is put over)它是船舶縱中線上唯一的漂角為零的點船舶在穩(wěn)定地直航時，不存在樞心點樞心點僅僅是因為船舶轉(zhuǎn)向而存在的!正車前進：樞心點幾乎總是位于距船首1/3船長處；倒車后退：樞心點位于船尾附近(A ships pivot point is nearly always located about one-third of the ships length from her

28、 bow when moving ahead, and at or near her stern when moving astern)船舶加速時，樞心點會向船舶運動的方向移動船舶操縱性與耐波性課件樞心點(PIVOT POINT)HEAD WAY, STEADY COURSE & SPEEDAHEAD BELL FROM DIW. LONG STEERING LEVER FROM PROPS/RUDDERSASTERN BELL FROM DIW. NO EFFECTIVE STEERING LEVER UNTIL SOME STERN WAY船舶操縱性與耐波性課件Ships Tactical

29、 Data Folder # of Screws# of RuddersLength/BeamPivot PointTurn DiagramsAcceleration/DecelerationAdvance/TransferNavigational Draft船舶操縱性與耐波性課件樞心點 船體外漂(indication of the bodily outward drift)操船者利用樞心點的位置來判斷操舵后船舶外漂究竟有多遠(Ship handlers use the position of the pivot point to indicate how far the ship will

30、drift bodily outward when the rudder is put over)知道在限制水域中轉(zhuǎn)向操船的余?？臻g(To know how much sea room that must be allowed for when making course changes in restricted waters)樞心點在重心之前，標示在產(chǎn)生非對稱流和向心力過程中船舶重心外漂有多遠(The pivot point is forward of the centre of gravity and indicates how far outwards the centre of gr

31、avity has drifted during the build up of the asymmetrical flow and centripetal force)船舶操縱性與耐波性課件漂角和樞心點(Drift angles and dynamic pivot point)定?；剞D(zhuǎn)條件下漂角沿船舶縱中線是變化的：外漂，在船尾處達到最大，向船首部遞減，在動樞心點處為零；然后是內(nèi)漂，向船首逐漸增大(A ship in steady turn conditions develops outward drift angles along its centreline that is greate

32、st at the stern, steadily decrease to zero at the dynamic pivot point, then turns inward and increases towards the bow)樞心點前移的結(jié)果是在船舶中部區(qū)域產(chǎn)生了一個凈外漂角(The forward position of the pivot point produces a net outward drift angle at the centre of gravity in the midship region)船舶操縱性與耐波性課件靜樞心點(Static pivot poin

33、t)靜樞心點為船舶初始旋轉(zhuǎn)圍繞的點(The static pivot point is the point about which the ship starts to rotate).這時只有船尾的舵力使在水中靜止不動的船舶開始旋轉(zhuǎn)(At that time, there is a single force at the stern that acts on the rudder to swing a ship that is stopped in water)船舶仍然不動，舵力矩使船尾開始旋轉(zhuǎn)起來(Thus, the ship is stationary, but helm is used

34、 to generate momentary swings of the stern by giving short bursts of ahead thrust against the rudder, for example when manoeuvring a ship alongside)當船舶繞靜樞心點開始旋轉(zhuǎn)時(When the ship starts to rotate about its static pivot point):橫向速度增加時重心外移一定距離(its centre of gravity will move a certain distance outward as

35、 it increases its outward lateral velocity) 然后船舶繞另一個樞心點旋轉(zhuǎn)(then the ship appears to rotate around another pivot point)這就是動樞心點(This is dynamic pivot point)!船舶操縱性與耐波性課件靜樞心點的位置(Location of the static pivot point)靜樞心點的位置取決于(The location of the static Pivot point depends on) 慣性矩(the moment of inertia)決定于船

36、舶質(zhì)量的分布(determined by the ships mass distribution)舵力臂(the rudder leverage)determined by the distance between the rudder and the centre gravity影響船舶慣性矩和舵力臂最重要的因素是方形系數(shù)The most important factor affecting the moment of inertia and the rudder leverage is the block coefficient (CB)縱傾對慣性矩和舵力臂也有影響(However, tr

37、im also affects the moment of inertia and the rudder leverage)船舶操縱性與耐波性課件How does hull form affect the location of static pivot point?方形系數(shù)大的船舶其慣性矩大，而舵力臂小(Ships with a high CB-value will have a high moment of inertia and a small rudder leverage)表明樞心點更靠近船首(means that the pivot point is moved closer to

38、 the bow)方形系數(shù)小的船舶其慣性矩小，而舵力臂大(Ships with a low CB-value will have a lower moment of inertia (more mass concentrated in the midship) and a larger rudder leverage)表明樞心點更靠近重心(means that the pivot point is moved closer to the centre of gravity)船舶操縱性與耐波性課件縱傾對靜樞心點位置的影響如何(How does trim affect the location o

39、f static pivot point)?艉傾使得重心更靠近舵(A stern trim moves the centre of gravity closer to the rudder, which means that)慣性矩增大，因船首質(zhì)量離重心越遠(the moment of inertia is increased, since the mass in the bow becomes further away from the centre of gravity)舵力臂減小(the rudder leverage is decreased)艏傾使得靜樞心點移向船首 (A stern

40、 trim thus moves the static pivot point forward, closer to the bow)艏傾使得重心移向船首(A head trim moves the centre of gravity closer to the bow)舵力臂增大(the rudder leverage is increased)慣性矩也增大(BUT the moment of inertia is also increased).艏傾使得靜樞心點向船尾方向移動靠近重心(However a head trim tends to move the static pivot po

41、int aft, towards the centre of gravity) 船舶操縱性與耐波性課件縱傾對靜樞心點位置的影響分析stern trimhead trim船舶操縱性與耐波性課件Criteria affecting the location of the pivot pointMoving the pivot point forwardsmall length to beam ratiotrimmed by the headdirectionally unstable shipthe wind force acts with the rudder force“high-lift r

42、udders”The Pivot Point can be situated ahead of the vessel when one or more of the criteria moving the pivot point forward is combined with a high vessel speedMoving the pivot point aftlarge length to beam ratiotrimmed by the sterndirectionally stable shipthe wind force counteracts the rudder forcethe turn