Practical Ship Hydrodynamics
Practical Ship Hydrodynamics
Practical Ship Hydrodynamics
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96 <strong>Practical</strong> <strong>Ship</strong> <strong>Hydrodynamics</strong><br />
What is the resistance of a ship with Lpp D 150 m if the ship is geometrically<br />
and dynamically similar to the base ship and the approach of ITTC’57<br />
is used (essentially resistance decomposition following Froude’s approach)?<br />
The wetted surface may be estimated by (Schneekluth and Bertram<br />
(1998), p. 185):<br />
S D ⊲3.4r 1/3 C 0.5Lwl⊳r 1/3<br />
Lwl may be estimated by Lwl D 1.01Lpp.<br />
The Reynolds number shall be based on Lpp. The correlation coefficient<br />
can be neglected.<br />
4. A sailing yacht has been tested. The full-scale dimensions are Lpp D 9.00 m,<br />
S D 24.00 m 2 , rD5.150 m 3 . The yacht will operate in sea water of D<br />
1.025 t/m 3 , D 1.19 Ð 10 6 m 2 /s.<br />
The model was tested with scale D 7.5 in fresh water with D<br />
1000 kg/m 3 , D 1.145 Ð 10 6 m 2 /s.<br />
The experiments yield for the model:<br />
Vm (m/s) 0.5 0.6 0.75 0.85 1.0 1.1 1.2<br />
RT,m (N) 0.402 0.564 0.867 1.114 1.584 2.054 2.751<br />
(a) Determine the form factor following Hughes–Prohaska.<br />
(b) Determine the form factor following ITTC’78. For simplification<br />
assume the exponent n for Fn to be 4 and determine just the ˛ and k<br />
in regression analysis.<br />
5. A container ship shall be lengthened by adding a parallel midship section<br />
of 12.50 m length (40 0 container and space between stacks). At full engine<br />
power (100% MCR D maximum continuous rating), the ship is capable of<br />
V D 15.6 knots.<br />
<strong>Ship</strong> data (original):<br />
Lpp 117.20 m<br />
Lwl 120.00 m<br />
B 20.00 m<br />
T 6.56 m<br />
rbilge 1.5 m<br />
CB 0.688<br />
lcb 0.0<br />
Wake fraction and thrust deduction shall be given by:<br />
w D 0.75 Ð CB 0.24 t D 0.5 Ð CB 0.15<br />
D 1.19 Ð 10 6 m 2 /s, D 1025 kg/m 3 .<br />
The ship is equipped with a propeller with 0 D 0.55. The relative rotative<br />
efficiency is R D 1.<br />
What is the power requirement after the conversion, if the propeller is<br />
assumed to remain unchanged? Base your prediction on Lap–Keller (Lap<br />
(1954), Keller (1973)) with a correlation coefficient cA D 0.35 Ð 10 3 .<br />
6. A ship of 150 m length sails with 15 kn on water of 12 m depth. It experiences<br />
a dynamic sinkage amidships of 1 m and a trim (bow immerses) of
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