For a fixed rudder area, increasing the length of a ship will make it more directionally stable but less responsive to its rudder舵面积不变
时,船长增大,方向稳定性变好,应舵性变差
船海系：邱磊
《船舶操纵性与耐波性》课件
directionally unstable ship 不具方向ห้องสมุดไป่ตู้定 性
directionally stable ship具 有方向稳定性
船海系：邱磊
运动响应(Response，应舵性、追随性)
《船舶操纵性与耐波性》课件
Is the requirement to turn in a satisfactory manner when a rudder order is given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 Both these response quantities are dependent upon应舵性的 大小取决于：
《船舶操纵性与耐波性》课件
船海系：邱磊
航向稳定性能(保向性)
《船舶操纵性与耐波性》课件
船海系：邱磊
初始转向性能与航行安全的关系
《船舶操纵性与耐波性》课件
船海系：邱磊
回转性能与航行安全的关系
《船舶操纵性与耐波性》课件
船海系：邱磊
停船操纵
-- 停船性能
《船舶操纵性与耐波性》课件
船海系：邱磊
第二章
(a)直线运动稳定性
(b)方向稳定性 (c)位置稳定性
船海系：邱磊
方向稳定性Directional stability
《船舶操纵性与耐波性》课件
In many operational circumstances it is more important for a ship to be able to proceed in a straight line than to turn, i.e. having a good directional stability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。
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 actions once the disturbance has passed
船海系：邱磊
Neutral directional stability随遇方向稳定性
《船舶操纵性与耐波性》课件
When the hydrodynamic hull force acts sufficiently far forward to provide both the centripetal force and the entire turning moment required to sustain the rate of turn it is said to act trough the ―neutral point‖, N0 Neutral directional stability transfers the turning moment completely from the rudder to the main hull force, so the outward controlling push of the rudder is lost
船海系：邱磊
方向稳定性(Directional stability)
《船舶操纵性与耐波性》课件
A ship that is ―directionally stable‖ will steer in a straight line in flat calm conditions with the rudder amidships
the magnitude of the rudder„s dimensions 舵的几何大小
the rudder angle 舵角 the ship„s speed 船速
船海系：邱磊
操纵性权衡(Manoeuvrability trade-off)
《船舶操纵性与耐波性》课件
The need for good directional stability and minimum response oppose each other方向稳定性与应舵性矛盾
初始转首性能(Initial turning/course-changing ability) 偏转抑制性能(Yaw checking ability) 回转性能(Turning ability)--—大舵角下 停船性能(Stopping ability)
船海系：邱磊
5
6
固有动稳性(直线运动稳定性)
It is easy to over-steer a 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
However, increasing rudder area will always improve the response characteristics of a hullform and usually improve its directional stability as well增大舵面积，总能提高应舵性，且方向稳定性也变好
On the other hand, a ship is said to be ―directionally unstable‖ if a course deviation begins or continues even in the absence of an external cause.
航向稳定性和回转性
《船舶操纵性与耐波性》课件
1. 航向稳定性 2. 船舶回转性 3. 回转运动的耦合特性
船海系：邱磊
第二章
航向稳定性和回转性
《船舶操纵性与耐波性》课件
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。
directionally unstable ship
directionally stable ship
船海系：邱磊
ship’s steerage behaviour?方向稳定性对驾驶有什 么影响?
《船舶操纵性与耐波性》课件
For a directionally stable ship the hydrodynamic hull force produces only a small turning moment (i.e. A is close to G) 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 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 For a directionally unstable ship the hydrodynamic force is moved further forward, and thus produces an increasing proportion of the turning moment whilst the bodily outward acceleration diminish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 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
船舶操纵性与耐波性
第2章 航向稳定性和回转性
船舶有哪些操纵方面的性能？
《船舶操纵性与耐波性》课件
1
2 3 4
固有动稳性(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(Course-keeping ability, also called directional stability)
船海系：邱磊
低速操纵性(Slow speed manoeuvrability)
《船舶操纵性与耐波性》课件
At low speeds the rudder is limited in its effectiveness due to the lack of flow across its surfaces 低速下舵效差 Levels of slow speed manoeuvrability are specified in terms of turning circle and other quantifiable parameters at speeds below 5 knots低速操纵性水平以航速低于5节时的回转圈等参数表示 There are however some ways to improve slow speed manoeuvrability(提高低速操纵性有多种方法): ―Correct‖ rudder position “纠正”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 采用辅助操纵设备提高低速操纵性