Effect of Gyroscopic Couple on a NAVAL SHIP

EFFECT OF GYROSCOPICCOUPLE ON A NAVAL SHIP Presented by – AMBARNIL BHARDWAJ Roll no- M-15/12 Mechanical Engineering, JORHAT ENGINEERING COLLEGE What is GYROSCOPIC COUPLE? The turning moment which opposes any change of the inclination of the axis of rotation of a gyroscope is known as gyroscopic couple. based on the principles of angular momentum. a gyroscope is a spinning wheel or disc in which the axle is free to assume any orientation. Mechanically. Gyroscope . .A gyroscope is a device for measuring or maintaining orientation. A GYROSCOPE . . This centrifugal force is called reactive force. itself. Reactive force – When a body. This external force applied is known as active force. .Some important terms   Active force . a force in the direction of centripetal acceleration (known as centripetal force) has to be applied externally over the body. is moving with uniform linear velocity along a circular path. The action of the reactive force is to tilt or move the body along radially outward direction. so that it moves along the required curved path. it is subjected to the centrifugal force radially outwards.When a body moves along a curved path with a uniform linear velocity. Plane of precession – The plane in which axis of spin rotates is known as plane of precession.    Axis of spin – The axis about which a wheel or a disk revolves or spins is known as axis of spin. Plane of spinning – The plane in which a wheel or disc rotates is known as plane of spinning. . Axis of precession – The axis about which the axis of spin turns is known as axis of precession. (g) Rolling is limited angular motion of the ship about the longitudinal axis. (e) Steering is turning on the side when viewing from the top.Terms used in a naval ship         Some of the terms used in connection with the motion of naval ships or sea vessels are given below (a) Bow is the fore or the front end. (c) Starboard is the right-hand side when looking from the stern. (f) Pitching is limited angular motion of the ship about the transverse axis. (d) Port is the left-hand side when looking from the stern. (b) Stern or aft is the rear end. . . Consider the ship taking a left turn. and rotor rotates in the clockwise direction when viewed from the stern. while it moves forward. as shown in figure. .Effect of Gyroscopic Couple on a Naval Ship during Steering Steering is the turning of a complete ship in a curve towards left or right. When the rotor of the ship rotates in the clockwise direction when viewed from the stern. The effect of this reactive gyroscopic couple is to raise the bow and lower the stern. it will have its angular momentum vector in the direction ox as shown As the ship steers to the left. . the active gyroscopic couple will change the angular momentum vector from ox to ox′. The reactive gyroscopic couple of the same magnitude will act in the opposite direction (i. The vector xx′ now represents the active gyroscopic couple and is perpendicular to ox. Thus the plane of active gyroscopic couple is perpendicular to xx′ and its direction in the axis OZ for left hand turn is clockwise.e. in anticlockwise direction). When the ship is steering to the right under similar conditions as discussed in note 4 above. The effect of the reactive gyroscopic couple on a boat propelled by a turbine taking left or right turn is similar as discussed above. 4. when viewed from the stern and the ship is steering to the left. When the ship steers to the right under similar conditions as discussed above. then the effect of reactive gyroscopic couple will be to raise the bow and lower the stern. . 6. 5. When the ship is steering to the right under similar conditions as discussed in note 2 above. then the effect of reactive gyroscopic couple will be to raise the bow and lower the stern. then the effect of reactive gyroscopic couple will be to raise the stern and lower the bow. the effect of the reactive gyroscopic couple. When the rotor rotates in the anticlockwise direction. 2. When the rotor rotates in the clockwise direction when viewed from the bow or fore end and the ship is steering to the left. will be to raise the stern and lower the bow. 3.Notes: 1. then the effect of reactive gyroscopic couple will be to lower the bow and raise the stern. Effect of Gyroscopic Couple on a Naval Ship during Pitching Pitching is the movement of a complete ship up and down in a vertical plane about transverse axis.e. as shown In this case. the transverse axis is the axis of precession. the motion of the axis of spin about transverse axis is simple harmonic. . The pitching of the ship is assumed to take place with simple harmonic motion i. Notes : 1. will try to move the ship toward star-board. The maximum gyroscopic couple tends to shear the holding-down bolts. whether it is pitching downwards or upwards. The effect of the gyroscopic couple is always given on specific position of the axis of spin i. the effect of the reactive gyroscopic couple.e.When the pitching is upward. On the other hand. 2. The pitching of a ship produces forces on the bearings which act horizontally and perpendicular to the motion of the ship. . 3. is to turn the ship towards port side. the effect of the reactive gyroscopic couple. if the pitching is downward. αmax = (ω1)2 . if sin ω1t = 1. ∴ Maximum angular acceleration during pitching. The angular acceleration is maximum. The angular acceleration during pitching.4. . the axis of precession becomes parallel to the axis of spin. there will be no effect of the gyroscopic couple acting on the body of the ship.Effect of Gyroscopic Couple on a Naval Ship during Rolling We know that. the axis of precession (i. however. longitudinal axis) is always parallel to the axis of spin for all positions. the axis of precession should always be perpendicular to the axis of spin.e. Hence. If. for the effect of gyroscopic couple to occur. there is no effect of the gyroscopic couple acting on the body of a ship. In case of rolling of a ship. . ...THANK YOU..