02航向稳定性和回转性-邱磊讲解课件.ppt
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1、船舶操纵性与耐波性船舶操纵性与耐波性第第2 2章章 航向稳定性和回转性航向稳定性和回转性邱磊邱磊qiu-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(Ini
2、tial turning/course-changing 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
3、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
4、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对处于定常运动状态的物体( (或系统或系统) ),若受到极小,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,则称原运动状态定常运动状态的能力。若能回复,则称原运动状态是是稳定的稳定的。(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Directionally un
5、stable shipsDirectionally unstable shipsv 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 trim and are difficult to steer manually
6、 Steady steering is only achieved by continually applying small short alternating helm actionsv Despite its problems, directional instability does allow 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
7、 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 hydrodynamic hull force, Neither the centre of t
8、he 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 vesselv The location of NThe location of N0 0 depends upon depends upon the centripetal force relative to
9、 the turning moment required for a given rate of turn and hullformv The position of A depends uponThe position of A depends upon压力足以的位置取决于:压力足以的位置取决于: the flow conditions around the immersed hullform its fore and aft distribution of surface areav So, the main factors affecting the directional So, th
10、e 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 纵倾纵倾 Hullform 船型船型 ahead speed 前进速度前进速度船海系: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 stability?stability?v Both head and stern trim incr
11、ease 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 forwardv More important is that the trim also alters the fore and aft M
12、ore 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
13、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 trimStern 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 with midships helmv Thus, Thus, directi
14、onal stability is directional stability is increasedincreasedv Head trimHead 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 only a small helm force is needed to maintain the turn but the ship will be slow to steady up wit
15、h 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 the directional stability?stability?v Moderately high CModerately high CB B-hulls have a relati
16、vely 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 shipsv Very full-bodied hullsVery full-
17、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 anglesrudder angles The swing of the ship can disto
18、rt 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?directional stability?v Increasing a ships ahe
19、ad 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 decreasedv A reduction in speed thus tends to increase a A r
20、eduction 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 ship has lost “steerage way”.船海系:邱磊船海系:邱磊船舶操纵性
21、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 ways of increasing the deadwoodExamples of ways of
22、 increasing the deadwood Skegs 尾鳍尾鳍 Fixed fins (submarine “stabilizers”) 稳定鳍稳定鳍 Other stern appendages 其他附体其他附体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,物体的运动状态是否
23、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也取决于所考察的运动状态和运动参数 1 1需针对某运动状态,或某一运动参数来分析其稳定性需针对某运动状态,或某一运动参数来分析其稳定性 2 2具有位置稳定性的船舶必具有直线稳定性和方向稳定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性;具有方向稳定性的船舶必具有直线稳定性 3 3按是否操舵,稳定性又分为自动按是否操舵,稳定性又分为自动(固有固有)稳定性稳定性(取决于取决于 船体几何船体几何)和控制稳定性和控制稳定性(取决于闭合回路取决于闭合回路) 4 4对于通常的水面舰船,若不操舵,不具备方
24、向稳定性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,也可能不具稳和位置稳定性,最多具有直线稳定性,也可能不具稳定性定性 5 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
25、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()()0uuXuumXu1()()()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
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