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Q7) A ship of length 150 m and breadth 19 m floats at a draught of 8.5 m in sea water of density 1025 kg/m³. In this condition the block coefficient ( C_b) is 0.69.

At a speed of 16 knots the following data applies:

delivered power = 6800 kW

quasi propulsive coefficient (QPC) = 0.71

correlation factor (SCF) = 1.20

Wetted surface area (S) = 2.57√∆L  ( m²)

Calculate the pull required to tow a similar model of length 5 m at the corresponding speed in fresh water of density 1000 kg/m³.  (16)

Note: The frictional coefficient for the model in fresh water of density 1000 kg/m³ is 1.694

The frictional coefficient for the ship in sea water of density 1025 kg/m³ is 1.413

Speed in m/s with the speed index (n) for ship and model 1.825