02航向稳定性和回转性讲解课件.ppt

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-changing abi

2、lity)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

3、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

4、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 stabilityv In many operational circumstances it is more important for In many operational circumstances it is more imp

5、ortant for a ship to be able to proceed in a straight line than to a ship to be able to proceed in a straight line than to turn,i.e.having a good directional stabilityturn,i.e.having a good directional stability在实际操船在实际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。中许多时候是保持直线运动的性能比转向性能更重要。directional stability:with the

6、rudder set at midships,and in the absence of external forces,the ship will travel in a straight linev Many Many hullformshullforms(for example relatively short and wide (for example relatively short and wide hulls)do not have this level of directional hulls)do not have this level of directional stab

7、ilitystability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、追随性)v Is the requirement to turn in a satisfactory manner when a Is the requirement to tu

8、rn in a satisfactory manner when a rudder order is givenrudder order is given操舵指令发出后船舶是否按要求转向了？操舵指令发出后船舶是否按要求转向了？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

9、 these response quantities are dependent uponBoth these response quantities are dependent upon应舵性的应舵性的大小取决于：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 T

10、he 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 rudder area,increasing the length of a ship will make it For a fixed rudder area,increasing the length of a s

11、hip will make it more directionally stable but less responsive to its ruddermore directionally stable but less responsive to its rudder舵面积不变舵面积不变时时,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 However,increasing rudder area will always improve the response However,increasing rudder area will always improve t

12、he response characteristics of a characteristics of a hullformhullform and usually improve its directional and usually improve its directional stability as wellstability as well增大舵面积，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

13、 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 manoeuvrability)(Slow speed manoeuvrability)v At low speeds the rudder is limited in its effectiveness due At low speeds the rudder i

14、s limited in its effectiveness due to the lack of flow across its surfacesto 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 specified in terms of Levels of slow speed manoeuvrability are specified in terms of turning circle and other quantifiable paramete

15、rs at speeds turning circle and other quantifiable parameters at speeds below 5 knotsbelow 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节时的回转圈等参数表示节时的回转圈等参数表示v There are however some ways 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

16、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 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

17、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 will steer in a straight line in flat calm conditions with the rudder amidshipsflat calm conditions with the rudder amidshipsa deviation from a

18、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 actions once the disturbance has passedv On the other hand,a ship is said to be On the other hand,a ship is said to be“directionally unstabledire

19、ctionally 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 absence of an external cause.cause.directionally stable shipdirectionally 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 stab

20、ility affect the How does the directional stability affect the shipships steerage behaviour?s steerage behaviour?方向稳定性对驾驶有什方向稳定性对驾驶有什么影响么影响?v For a For a directionally directionally stable stable shipship the hydrodynamic hull force produces the hydrodynamic hull force produces only a small turning

21、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

22、unstableunstable ship ship the hydrodynamic force is moved the hydrodynamic force is moved further forward,and thus produces an increasing proportion of the further forward,and thus produces an increasing proportion of the turning moment whilst the bodily outward acceleration diminishturning moment

23、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

24、ship with minimal directional stability by applying excessive counter helm,creating a cycle of ever increasing oscillatory 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 hydrodynam

25、ic hull force acts sufficiently far forward to provide When the hydrodynamic hull force acts sufficiently far forward to 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 sa

26、id to act trough the sustain the rate of turn it is said to act trough the“neutral pointneutral point”,N,N0 0 v Neutral 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 ou

27、tward controlling push from the rudder to the main hull force,so the outward controlling push of the rudder is lostof the rudder is lostv 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

28、 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 shipsv An increasing number of new ships are directionally unstable under An increasing number of new ships are dire

29、ctionally unstable under certain conditions of trim and are difficult to steer manuallycertain conditions of trim and are difficult to steer manually Steady steering is only achieved by continually applying small short alternating helm actionsv Despite its problems,directional instability does allow

30、 a ship to make Despite its problems,directional instability does allow a ship to make tight turnstight turns 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 af

31、fecting directional(Factors affecting directional stability)stability)v Neither the centre of the hydrodynamic 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

32、 vesselin position for a single vesselv The location of NThe location of N0 0 depends upon depends upon the centripetal force relative to the turning moment required for a given rate of turn and hullformv 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 cond

33、itions around the immersed hullform its fore and aft distribution of surface areav So,the 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Ho

34、w does trim affect the directional How does trim affect the directional stability?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

35、increased by trim and the point N0 is moved further forwardv More important is 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 t

36、he 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

37、a large helm force to maintain the turn the ship will steady up quickly with midships helmv Thus,Thus,directional stability is directional stability is increasedincreasedv Head trim moves A further ahead moves A further aheadv Point A is just aft of the NPoint A is just aft of the N0 0-pointpoint so

38、 only a small helm force is needed to maintain the turn but the ship will be slow to steady up with midships helmv 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

39、 the directional stability?stability?v Moderately high CModerately 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

40、 forward than for finer lined shipsthan for finer lined shipsv 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 unstabledirecti

41、onally unstable at small at small rudder anglesrudder 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 s

42、hips ahead speed affect directional stability?directional 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 decre

43、aseddirectional stability is decreasedv A reduction 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 f

44、low for the rudder to be effective and the 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 feather

45、s on an arrow or dart!v Examples of 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如何提高方向稳定性？如何提高方向稳定性？船海系：邱磊船海系：邱磊船舶操纵性

46、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 5v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

47、耐波性船舶操纵性与耐波性课件课件(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,uu uvvrruuvvrr 0(1-25)1()()0uu

48、XuumXu1()()()vvrrGYvm Yv vYmu rYmxrY 1()()()vvGrGzrNvNmx vNmx u rIN rNuuumuXuX 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()Gvvrrm vu rx rY vY vY rY r1()zGvvrrI rmx v ruN vN vN rN ruumuXuX u()0uumXuXu第一式对应的特征方程为：第一式对应的特征方程为：

49、3()0uumXX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。31tuu e 分母为正，分子为负。(2-4)(2-5)3(2-3)3()0uumXX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

50、)(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:ttererr2121(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:1212ttvv 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)()()(21212212AAACABAACAB212120ABC21214,2BBCAAA 其根