Maneuver

The term maneuvering describes the controlled change of position or position of a vehicle. A vehicle maneuvers by driving or flying a maneuver. The surface, which sweeps a vehicle when Manövriervorgang is Maneuvering called the maneuverability denotes the property of the vehicle to run under its own and / or external control aids the desired maneuvers.

Examples

• Parking and unparking an automobile
• Evasive maneuvers of a motorcycle
• Williamson turn ( man-over-board maneuver ) of a ship
• Jibe of a sailboat
• Docking a space shuttle to a space station
• Change of lane of a vehicle
• Flight maneuvers such as landing a helicopter on a ship in heavy seas

Categories

One can distinguish between two categories:

• Road vehicles are frictionally tied to the ground, their maneuvering movements result directly from the driver's steering movements according to the laws of kinematics .
• Aircraft and watercraft must be at an angle to the flow in order to compensate for changes in direction of the centrifugal force with hydro- or aerodynamic lift forces. They therefore obey their control organs with a delay.

Ships

The maneuvering of ships as a sub-discipline of ship hydrodynamics plays a special role . After controversial discussions in the professional world, the IMO succeeded in establishing a consensus on certain permissible values ​​of standardized standard maneuvers and defining them as the standard. This guideline essentially describes how slowly a ship can react to its rudder. These are mainly parameters of the 10/10 and 20/20 Z maneuvers.

In the 10/10 maneuver, 10 ° rudder is placed and after a 10 ° course deviation counter rudder, etc., and the 20/20 maneuver is defined accordingly. Essentially, it is stipulated after which distance a certain course change must be achieved and the angle by which the ship may continue to turn in the undesired direction after the counter-rudder has been turned. Certain dimensions of the turning circles at a 35 ° rudder angle are also prescribed.

A particularly interesting phenomenon is yaw stability . Certain ships are greedily unstable. You drive straight ahead without laying oars in the sense of an unstable equilibrium, i.e. H. so not at all. The rate of rotation as a function of the rudder angle has a hysteresis loop , i.e. H. If you gradually change the rudder angle and lead it through the zero point, you come across an area in which the ship turns the wrong way round and only suddenly changes its direction of rotation at larger rudder angles.

In order to measure the relationship between the rudder angle and the rate of rotation and to represent it as a control curve, a Dieudonné spiral maneuver is carried out, which can be imagined as a sequence of turning circles. A simplified way of determining yaw instability is the pull-out maneuver, which measures the value against which the rate of turn converges when you put the rudder amidships after a disturbance.

The stability lever arm is sometimes used as a characteristic value. It describes how far the hydrodynamic center of forces lies in pure circular travel without a drift angle in front of the hydrodynamic center of forces with pure translation without rotation. The ship is yaw-stable with a positive stability lever arm.

Maneuvering behavior

The maneuvering behavior of ships can be affected by environmental influences: In shallow water, less water flows under the ship and more sideways past it, which worsens the flow of the rudder. As a result, it can happen that a ship no longer obeys its rudder when passing a shoal.

If two ships sail too close to each other, in the sense of the Bernoulli equation, there is an excess of speed in the gap and consequently a negative pressure because the gap amidships has a narrower cross-section. The ships cling to each other. The same applies to encounters too close. In the vicinity of port facilities, vertical walls reflect the potential flow, the ship is sucked in by its own potential-theoretical mirror image.

Man overboard maneuvers

The characteristic values ​​of the Williamson turn are also relevant for safety : In the case of " man overboard ", the rudder is laid hard, and only if the correct course angle deviation, with which the counter-rudder has to be laid hard, is known, the opposite course with the Bringing the initial course to cover and finding the accident victim.

The decision on sensible standards for the maneuverability of ships is made more difficult by the fact that new and unconventional control and propulsion organs are constantly being implemented. Examples include pod drives, which, not unlike outboard motors, house huge electric motors (direct current machines) in a nacelle equipped with propellers and can be rotated all around.

Corresponding model tests, system identification calculations and, in the future, increasingly maneuver- related CFD calculations are one of the tasks of the shipbuilding research institutes .

See also: maneuvers (shipping)