02航向稳定性和回转性

1、船舶操纵性与耐波性 第2章 航向稳定性和回转性 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 船舶有哪些操纵方面的性能？船舶有哪些操纵方面的性能？ 固有动稳性固有动稳性(也称直线运动稳定性也称直线运动稳定性)(Inherent dynamic stability, also called straight line stability) 方向稳定性或保向性方向稳定性或保向性(Course-keeping ability, also called directional stability) 初始转首性能初始转首性能(Initial turning/course-cha

2、nging ability) 偏转抑制性能偏转抑制性能(Yaw checking ability) 回转性能回转性能(Turning ability)-大舵角下大舵角下 停船性能停船性能(Stopping ability) 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 固有动稳性固有动稳性( (直线运动稳定性直线运动稳定性) ) 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 航向稳定性能航向稳定性能( (保向性保向性) ) 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 初始转向性能与航行安全的关系初始转向性能与航行安

3、全的关系 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 回转性能与航行安全的关系回转性能与航行安全的关系 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 停船操纵停船操纵 - - 停船性能停船性能 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 第二章第二章 航向稳定性和回转性航向稳定性和回转性 1. 1. 航向稳定性航向稳定性 2. 2. 船舶回转性船舶回转性 3. 3. 回转运动的耦合特性回转运动的耦合特性 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 第二章第二章 航向稳定性和回转性航向稳

4、定性和回转性 v稳定性的概念：稳定性的概念： 对处于定常运动状态的物体(或系统)，若受到极小 的外界干扰作用而偏离原定常运动状态；当干扰去 除后，经过一定的过渡过程，看是否具有回复到原 定常运动状态的能力。若能回复，则称原运动状态 是稳定的。 (a)直线运动稳定性直线运动稳定性 (b)方向稳定性方向稳定性 (c)位置稳定性位置稳定性 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 方向稳定性方向稳定性Directional stabilityDirectional stability v In many operational circumstances it is m

5、ore In many operational circumstances it is more important for a ship to be able to proceed in a important for a ship to be able to proceed in a straight line than to turn, i.e. having a good straight line than to turn, i.e. having a good directional stabilitydirectional stability在实际操船中许多时候是保持直线运在实际

6、操船中许多时候是保持直线运 动的性能比转向性能更重要。动的性能比转向性能更重要。 directional stability: with the rudder set at midships, and in the absence of external forces, the ship will travel in a straight line v Many hullforms (for example relatively short and wide Many hullforms (for example relatively short and wide hulls) do not

7、have this level of directional hulls) do not have this level of directional stabilitystability许多船型不具有方向稳定性许多船型不具有方向稳定性 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 directionally stable ship具 有方向稳定性 directionally unstable ship 不具方向稳定 性 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 运动响应运动响应(Response(Response，应舵性，应舵性、追随性

8、、追随性) ) v Is the requirement to turn in a satisfactory manner Is the requirement to turn in a satisfactory manner when a rudder order is givenwhen a rudder order is given操舵指令发出后船舶是否按要操舵指令发出后船舶是否按要 求转向了？求转向了？ The ship must respond to its rudder and change heading in a specified minimum time 在给定的最短时间内

9、船舶必须应舵 转首 There should be minimum overshoot of heading after a rudder order is given超越角应最小 v Both these response quantities are dependent uponBoth these response quantities are dependent upon应舵应舵 性的大小取决于：性的大小取决于： the magnitude of the rudders dimensions 舵的几何大小 the rudder angle 舵角 the ships speed 船速 船

10、海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 操纵性权衡操纵性权衡(Manoeuvrability trade-off)(Manoeuvrability trade-off) v The need for good directional stability and minimum The need for good directional stability and minimum response oppose each otherresponse oppose each other方向稳定性与应舵性矛盾方向稳定性与应舵性矛盾 v For a fixed rudde

11、r area, increasing the length of a ship will make For a fixed rudder area, increasing the length of a ship will make it more directionally stable but less responsive to its rudderit more directionally stable but less responsive to its rudder舵舵 面积不变时面积不变时, ,船长增大船长增大, ,方向稳定性变好方向稳定性变好, ,应舵性变差应舵性变差 v Ho

12、wever, increasing rudder area will always improve the response However, increasing rudder area will always improve the response characteristics of a hullform and usually improve its directional characteristics of a hullform and usually improve its directional stability as wellstability as well增大舵面积，

13、总能提高应舵性，且方向稳定性也变好增大舵面积，总能提高应舵性，且方向稳定性也变好 But rudder dimensions are limited by stern geometry艉部几何限 制 Also, large rudders will increase drag and so reduce the ships speed for a given delivered horse power from the propeller阻力增 大，导致速降 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 低速操纵性低速操纵性(Slow speed manoeuvrab

14、ility)(Slow speed manoeuvrability) v At low speeds the rudder is limited in its effectiveness At low speeds the rudder is limited in its effectiveness due to the lack of flow across its surfacesdue to the lack of flow across its surfaces 低速下舵效差低速下舵效差 v Levels of slow speed manoeuvrability are specif

15、ied in Levels of slow speed manoeuvrability are specified in terms of turning circle and other quantifiable parameters terms of turning circle and other quantifiable parameters at speeds below 5 knotsat speeds below 5 knots低速操纵性水平以航速低于低速操纵性水平以航速低于5 5节时的回节时的回 转圈等参数表示转圈等参数表示 v There are however some w

16、ays to improve slow speed There are however some ways to improve slow speed manoeuvrabilitymanoeuvrability( (提高低速操纵性有多种方法提高低速操纵性有多种方法) ): : “CorrectCorrect” rudder position rudder position “ “纠正纠正”舵的位置舵的位置 To improve the flow rate it is often positioned directly behind the propeller Use devices that

17、 can improve slow speed manoeuvrability Use devices that can improve slow speed manoeuvrability 采用辅助操纵设备提高低速操纵性采用辅助操纵设备提高低速操纵性 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 方向稳定性(Directional stability) v A ship that is A ship that is “directionally stabledirectionally stable” will steer in a straight line in

18、will steer in a straight line in flat calm conditions with the rudder amidshipsflat calm conditions with the rudder amidships a deviation from a set course increases only while an external force or moment is acting to cause the deviation. the vessel will come to a new steady heading without any helm

19、 actions once the disturbance has passed v On the other hand, a ship is said to be On the other hand, a ship is said to be “directionally unstabledirectionally unstable” if a if a course deviation begins or continues even in the absence of an external course deviation begins or continues even in the

20、 absence of an external cause. cause. directionally stable ship directionally unstable ship 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 How does the directional stability affect the How does the directional stability affect the shipships steerage behaviour?s steerage behaviour?方向稳定性对驾驶有方向稳定性对驾驶有 什么影响什么影响? ?

21、 v For a For a directionally directionally stable stable shipship the hydrodynamic hull force produces the hydrodynamic hull force produces only a small turning moment (i.e. A is close to G) only a small turning moment (i.e. A is close to G) 对于具有方向稳定性对于具有方向稳定性 的船，船体上的水动力只产生较小的回转力矩的船，船体上的水动力只产生较小的回转力

22、矩 The helm is heavy and a ship with excessive directional stability is reluctant to alter course at all 船舶的方向稳定性太好，即使操大舵角也难以转向 v For a For a directionally directionally unstableunstable ship ship the hydrodynamic force is moved the hydrodynamic force is moved further forward, and thus produces an in

23、creasing proportion of the further forward, and thus produces an increasing proportion of the turning moment whilst the bodily outward acceleration diminishturning moment whilst the bodily outward acceleration diminish对于方向对于方向 稳定性不好的船，其水动力作用中心前移，能产生更大的回转力矩，并能抵消向稳定性不好的船，其水动力作用中心前移，能产生更大的回转力矩，并能抵消向 外的

24、加速度外的加速度 Control of the ship is more tentative as it will be quicker to develop a swing on applying helm, but slower to “steady-up” 操船时要格外小心以免摇摆，直航难 It is easy to over-steer a ship with minimal directional stability by applying excessive counter helm, creating a cycle of ever increasing oscillatory

25、swings to port and starboard 方向稳定性奇差的船操纵起来容易左右振荡摇摆 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 Neutral directional stabilityNeutral directional stability随遇方向稳定性随遇方向稳定性 v When the hydrodynamic hull force acts sufficiently far forward to provide When the hydrodynamic hull force acts sufficiently far forward t

26、o provide both the centripetal force and the entire turning moment required to both the centripetal force and the entire turning moment required to sustain the rate of turn it is said to act trough the sustain the rate of turn it is said to act trough the “neutral pointneutral point”, N, N0 0 v Neut

27、ral directional stability transfers the turning moment completely Neutral directional stability transfers the turning moment completely from the rudder to the main hull force, so the outward controlling push from the rudder to the main hull force, so the outward controlling push of the rudder is los

28、tof the rudder is lost v Neutral directional stability is only likely to occur at smaller helm Neutral directional stability is only likely to occur at smaller helm angles and lower rates of turn when Nangles and lower rates of turn when N0 0 is closer to midships is closer to midships 船海系：邱磊船海系：邱磊

29、船舶操纵性与耐波性船舶操纵性与耐波性课件课件 Directionally unstable shipsDirectionally unstable ships v An increasing number of new ships are directionally unstable under An increasing number of new ships are directionally unstable under certain conditions of trim and are difficult to steer manuallycertain conditions of

30、trim and are difficult to steer manually Steady steering is only achieved by continually applying small short alternating helm actions v Despite its problems, directional instability does allow a ship to make Despite its problems, directional instability does allow a ship to make tight turnstight tu

31、rns But it is important that the pilot or master is familiar with the ships behaviour and plans an alter course to allow for this 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 影响方向稳定性的因素影响方向稳定性的因素(Factors affecting directional (Factors affecting directional stability)stability) v Neither the centre of the hyd

32、rodynamic hull force, Neither the centre of the hydrodynamic hull force, point A, nor the neutral steering point (Npoint A, nor the neutral steering point (N0 0) are fixed ) are fixed in position for a single vesselin position for a single vessel v The location of NThe location of N0 0 depends upon

33、depends upon the centripetal force relative to the turning moment required for a given rate of turn and hullform v The position of A depends uponThe position of A depends upon压力中心的位置取决于：压力中心的位置取决于： the flow conditions around the immersed hullform its fore and aft distribution of surface area v So, t

34、he main factors affecting the directional So, the main factors affecting the directional stability arestability are影响方向稳定性的主要因素有影响方向稳定性的主要因素有: : Trim 纵倾 Hullform 船型 ahead speed 前进速度 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 How does trim affect the directional How does trim affect the directional stabilit

35、y?stability? v Both head and stern trim increase the ships moment of inertia Both head and stern trim increase the ships moment of inertia 首倾和尾首倾和尾 倾都增大了船舶的惯性矩倾都增大了船舶的惯性矩 So the required moment for a given rate of turn is increased by trim and the point N0 is moved further forward v More important i

36、s that the trim also alters the fore and aft More important is that the trim also alters the fore and aft distribution of immersed hull surface and thus the position of A (see distribution of immersed hull surface and thus the position of A (see next page)next page)更为重要的是纵倾也改变了首尾湿表面积的分布和压力中心更为重要的是纵倾

37、也改变了首尾湿表面积的分布和压力中心A A的位置的位置 stern trimhead trim 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 v Stern trim moves A further aft moves A further aft v Point A is well aft of the NPoint A is well aft of the N0 0-point-point so the ship needs a large helm force to maintain the turn the ship will steady up quickly

38、 with midships helm v Thus, Thus, directional stability is directional stability is increasedincreased v Head trim moves A further ahead moves A further ahead v Point A is just aft of the NPoint A is just aft of the N0 0- - pointpoint so only a small helm force is needed to maintain the turn but the

39、 ship will be slow to steady up with midships helm v Thus, Thus, directional stability is directional stability is decreaseddecreased 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 How does the hullform affect the directional How does the hullform affect the directional stability?stability? v Moderately high C

40、Moderately high CB B-hulls have a relatively large moment of inertia -hulls have a relatively large moment of inertia about the vertical axes so point Nabout the vertical axes so point N0 0 will tend to be further forward will tend to be further forward than for finer lined shipsthan for finer lined

41、 ships v Very full-bodied hullsVery full-bodied hulls: point A tends to be even further forward than : point A tends to be even further forward than N N0 0 so these ships are likely to be so these ships are likely to be directionally unstabledirectionally unstable at small at small rudder anglesrudd

42、er angles The swing of the ship can distort the boundary layer to the extent that flow is directed to the wrong side of the rudder and the rudder force is reversed 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 How does the ships ahead speed affect How does the ships ahead speed affect directional stability?di

43、rectional stability? v Increasing a ships ahead speed for a given rudder Increasing a ships ahead speed for a given rudder angle will move the Nangle will move the N0 0-point further aft, thus the -point further aft, thus the directional stability is decreaseddirectional stability is decreased v A r

44、eduction in speed thus tends to increase a A reduction in speed thus tends to increase a ships directional stability for a given rudder ships directional stability for a given rudder angleangle But if the ship is moving too slow there will be insufficient flow for the rudder to be effective and the

45、ship has lost “steerage way”. 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 v The directional stability can be improved by using more The directional stability can be improved by using more “deadwooddeadwood” at at the sternthe stern 在船尾安装呆木在船尾安装呆木 analogous to the feathers on an arrow or dart! v Examples of

46、ways of increasing the deadwoodExamples of ways of increasing the deadwood Skegs 尾鳍 Fixed fins (submarine “stabilizers”) 稳定鳍 Other stern appendages 其他附体 Ways of improving directional stabilityWays of improving directional stability如何提高方向稳如何提高方向稳 定性？定性？ 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 第二章第二章 航向稳定

47、性和回转性航向稳定性和回转性 物体的运动状态是否稳定，不仅取决于物体的性质，也 取决于所考察的运动状态和运动参数 1 需针对某运动状态，或某一运动参数来分析其稳定性 2 具有位置稳定性的船舶必具有直线稳定性和方向稳定性； 具有方向稳定性的船舶必具有直线稳定性 3 按是否操舵，稳定性又分为自动自动(固有固有)稳定性稳定性(取决于 船体几何)和控制稳定性控制稳定性(取决于闭合回路) 4 对于通常的水面舰船，若不操舵，不具备方向稳定性和 位置稳定性，最多具有直线稳定性，也可能不具稳定性 5 v对稳定性概念的理解对稳定性概念的理解 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件

48、 (2-1) 小扰动方程小扰动方程 v 为对稳定性作定量分析，采用为对稳定性作定量分析，采用“运动稳定性理论运动稳定性理论”分析方法。分析方法。 v 设船舶初始运动状态：设船舶初始运动状态：u1=const=U, v1=r1=0. .扰动后引起的扰扰动后引起的扰 动运动参数：动运动参数： v 由于对初始状态是小扰动，故可采用线性操纵运动方程由于对初始状态是小扰动，故可采用线性操纵运动方程(1-25)(1-25) 式来描述。因不操舵，式来描述。因不操舵， . .将式将式(2-1)(2-1)代入式代入式(1-25)(1-25)， 1, ,u u uv vrru uv vrr 0 (1-25) 1

49、()()0 uu XuumXu 1 ()()() vvrrG Y vm Y v vYmu rYmxrY 1 ()()() vvGrGzr N vNmx vNmx u rIN rN u uu muXuX u 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 其中，第一式与后两式无关其中，第一式与后两式无关.第一式可重写为：第一式可重写为： 小扰动方程小扰动方程 v即可求得小扰动方程：即可求得小扰动方程： (2-2) (2-3) 1 () Gvvrr m vu rx rY vY vY rY r 1 () zGvvrr I rmx v ruN vN vN rN r uu muX

50、uX u ()0 uu mXuXu 第一式对应的特征方程为：第一式对应的特征方程为： 3 ()0 uu mXX 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 小扰动方程小扰动方程 v特征根为：特征根为： v故式故式(2-3)(2-3)的解为：的解为： v 总为负值，故对纵向速度扰动总具有稳定性。因总为负值，故对纵向速度扰动总具有稳定性。因 此，船舶在水平面内的航向稳定性主要取决于方程此，船舶在水平面内的航向稳定性主要取决于方程 (2-2)(2-2)的后二式。的后二式。 3 1 t uu e 分母为正， 分子为负。 (2-4) (2-5) 3 (2-3) 3 ()0 u

51、u mXX 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 二元一阶常系二元一阶常系 数微分方程组数微分方程组 (2-7) (2-8) (2-6) 小扰动方程小扰动方程 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 特征方程特征方程 特征根特征根 角速度扰动方程角速度扰动方程(2-7)(2-7)的解为的解为: : tt ererr 21 21 (2-9) (2-10) 速度速度v的小扰动方程的小扰动方程 0AvBvCv 的解为的解为: : 12 12 tt vv ev e (2-11) 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐

52、波性课件课件 航向稳定性分析航向稳定性分析 v接下来我们进行航向稳定性分析接下来我们进行航向稳定性分析 0)( )()( 2121 2 21 2 A A A C A B A A C A B 2121 2 0ABC 2 12 14 , 2 BBC AAA 其根为：其根为： 于是有：于是有： 可见：可见： 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 航向稳定性分析航向稳定性分析 0 C A 12 ,皆为负实部的必要条件是：皆为负实部的必要条件是： : BC AA 当为任意值, 为负值时 2 12 14 , 2 BBC AAA 两根将皆为实数，且两根将皆为实数，且 必有一

53、个正根必有一个正根 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 航向稳定性分析航向稳定性分析 0,0 CB AA 12 ,皆为负实部的必要条件是：皆为负实部的必要条件是： 2 4 : CCB AAA 当0, 时 2 12 14 , 2 BBC AAA 12 , B A 0, 则皆为负数. 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 航向稳定性分析航向稳定性分析 v可见，航向稳定性条件可归结为：可见，航向稳定性条件可归结为： 0,0 CB AA 2 4 : CCB AAA 当0, 时 2 12 14 , 2 BBC AAA 12 , 0 B

54、 A 皆为复数; 而使其实部为负的附加条件仍为: 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 水动力导数分析水动力导数分析 v Y 较大的负值较大的负值 v N 不定符号的小量不定符号的小量 图2-3 当具有横向加速度扰动时当具有横向加速度扰动时 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 r Y 不定符号的小量不定符号的小量 r N 较大的负值较大的负值 图2-4 当具有回转加速度扰动时当具有回转加速度扰动时 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 受侧向扰动速度受侧向扰动速度v作用时作用时 v Y 较大

55、的负值较大的负值 v N 不很大的负值不很大的负值 图2-5 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 由角速度由角速度r引起的力和力矩引起的力和力矩 r Y 不定符号的小量不定符号的小量 r N 较大的负值较大的负值 图2-6 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 稳定性衡准数稳定性衡准数C C 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 稳定性衡准数稳定性衡准数C C 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 C0 船舶在水平面的运动具有直线稳定性； C Iv 时，船舶

56、具时，船舶具 有航向稳定性有航向稳定性。 v试验结果表明，对一般排试验结果表明，对一般排 水量船舶水量船舶lv0 ，即位置力，即位置力 的压力中心总位于船中前，的压力中心总位于船中前， 随随水深变浅，水深变浅，lv 变化不大，变化不大， 而而lr 的的变化变化甚甚大大，原因是，原因是 随水深变浅，随水深变浅，Yr 增加而增加而 引起，见图引起，见图2-9。 图图2-9 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 开始操舵时，船舶重心的瞬时开始操舵时，船舶重心的瞬时 位置为回转运动的起始点，称位置为回转运动的起始点，称 之为之为执行操舵点执行操舵点。 回转圈的主要特征

57、参数为：回转圈的主要特征参数为： 1)反横距反横距从船舶初始的 直线航线至回转运动轨迹向 反方向最大偏离处的距离为 S1。 2)正横距正横距从船舶初始直 航线至船首转向90度时，船 舶重心所在位置之间的距离 为S2。该值越小，则回转性 就越好。 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 回转圈的主要特征参数为：回转圈的主要特征参数为： 3)纵距纵距从转舵开始时刻 船舶重心G点所在的位置， 至船首转向90度时船舶纵中 剖面，沿原航行方向计量的 距离S3。一般船舶纵距约为3、 4倍船长。其值越大，表示 船舶对初始时刻的操舵反应 越迟钝，即应舵较慢。 船海系：邱磊船海系

58、：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 4)4)战术直径战术直径从船舶从船舶 原来航线至船首转向原来航线至船首转向180 度时，船纵中剖面所在位度时，船纵中剖面所在位 置之间的距离置之间的距离DT。其值。其值 越小，则回转性越好。对越小，则回转性越好。对 一般普通船一般普通船DT约为约为36 倍船长，回转性较差者可倍船长，回转性较差者可 达达78倍船长。倍船长。 回转圈的主要特征参数为：回转圈的主要特征参数为： 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 5)定常回转直径定常回转直径定常回定常回 转阶段船舶重心点圆形轨迹转阶段船舶重心点圆形轨迹 的直径

59、的直径D。一般。一般D0.9DT。 通常采用相对回转直径通常采用相对回转直径D L代表回转性优劣。通常认代表回转性优劣。通常认 为回转性好的船，最小相对为回转性好的船，最小相对 回转直径为回转直径为3左右，回转性左右，回转性 差的船约为差的船约为10左右，大多数左右，大多数 船在船在57的范围内。的范围内。 回转圈的主要特征参数为回转圈的主要特征参数为： 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 6 6）进程）进程R R自执行操自执行操 舵点起至回转圈中心舵点起至回转圈中心 的纵向距离；的纵向距离；R=S3-R； 它表示船舶对舵作用的它表示船舶对舵作用的 应答性，

60、应答性，R越小则应答越小则应答 性越好，通常性越好，通常R/L数值数值 约为约为l2。 回转圈的主要特征参数为：回转圈的主要特征参数为： 船海系：邱磊船海系：邱磊 船舶操纵性与耐波性船舶操纵性与耐波性课件课件 船舶回转过程中，在船上还存在 一个横向速度分量为零的点，称 为枢心点p， 由图可见，枢心点前后横向速度反向。一 般在初始操舵瞬时，枢心处于船体之撞击 中心，约在船舶重心前1/10船长处。以后 随回转过程的发展，枢心点位置向船首移 动，直至定常回转状态，枢心位置稳定在 重心前1/61/3船长处。所以，当船舶回 转时，若驾驶人员站在枢心点p上，则可 看到一方面船以Vp速度平移，另一方面船 上