Maneuvering in Irregular Waves + Added Resistances

1. When discussing the ship maneuvering in waves, it should consider irregular waves to represent actual seaway.

2. The task of naval architect is to ensure (within the limits of other design requirements):

  • the hull form and propulsion arrangement as much as possible to be efficient in the hydrodynamic sense
  • the ultimate test is that the ship shall perform, at the required speed with the minimum of shaft power
  • here, the problem is to attain the best combination of low resistance and high propulsive efficiency.
  • in general, this ("attain the best combination of low resistance and high propulsive efficiency" ) can only be attained by a proper matching of hull and propeller.
3. Therefore, before we go to explore what best match of hull and propeller, in order to assess and examine the ship maneuvering in irregular waves, it is mandatory to back one step - should attain the best combination of low resistance and propulsive - and investigate the effect of irregular waves to the ship motion in maneuvering motion i.e. in turning circle and zig-zag. We want to at least 90% sure that what the estimated added resistance and its effect to the ship motion.
-- update: from the comparison so far between exp and cal for KVLCC2, there is effect of added resistance to the straight moving course ( rudder angle = 0). The reduction in the speed advance is due to added resistance from the irregular waves short crested.-2019-2-25

4. As such, my research chose KVLCC2 and KCS ship types. By using this two models, free running test were conducted. The results from the experiment in the tank test were compared side-by-side with the calculation results. The results comprised of low frequency motion and high frequency motion.

5. Besides that, the comparison also on the index of the turning circle.

2019-02-25

****QUASI-STEADY PROBLEM.

In the thesis by Nicholaas, it mentioned on the if too much drop decrease or variation on u (velocity) of the ship, so the quasi-steady assumption will be no more valid. So the Ro' (which is constant) no more can stand alone. It need additional terms that may depend on the u.










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