Practical Ship Hydrodynamics

Ship manoeuvring 205
The ship performs a pull-out manoeuvre and the following curve for P is
recorded:
0.020
0.010
0.007
•
y (rad/s)
10 20
(a) Determine the constants T and ˛!
(b) Sketch a corresponding curve of P for the case that at t D 0, P D
0.002 rad/s instead of P D 0.02 rad/s.
5. Determine the rudder lift at 10° rudder angle for the semi-balanced rudder
behind a propeller and hull of a ferry as shown below. The ship speed is
30 kn, the propeller thrust 4000 kN. The wake fraction is w D 0.25. Correct
the rudder lift for the propeller loading according to Söding (1998a, b).
Following Goodrich and Mooland (1979) we may assume that at 10°
rudder angle a semi-balanced rudder as the one depicted may have 79.2%
of the lift of a ‘normal’ rudder.
Dimensions are to be taken from the sketch (see p. 206).
6. The container ship in Tables 5.1 and 5.2 sails in a turning circle with rudder
in the centre position using just its bow thruster at maximum power. The
bow thruster is located 4 m aft of the forward perpendicular. The power of
the thruster is 4000 kW. The pipe diameter is 2.5 m. The ship speed is 5 kn.
The efficiency of the bow thruster is D 0.8.
Compute the radius of the turning circle R assuming linear correlation
between hull forces and motions. The radius of the turning circle follows
from the relation U D r Ð R, wherer is the yaw rate.
Forward speed changes the thrust of a bow thruster T from the value at
zero speed T0:
T/T 0
−5 5 10
1
U (kn)
t (s)