I'm a student of mechanical engineering but with no specialization in maritime applications. I hope you can clarify something for me.
I'm in the process of determining the approximate forces that would affect a ship-sized vessel positioned by anchor or mooring and I reckon that would include wind, wave and current forces.
In estimating the forces I am using the drag equation
which depends on the drag coefficient
. Different sources claim the drag coefficient of a flat faced box to be 2.1 which I reckon would be a good estimate for the drag coefficient of a barge, as it resembles a box.
However, for the drag coefficient of a ship hull I am confused. Page 7 of this paper
shows drag coefficients for a ship hull between 0.0027 and 0.0032, while the figure on the Wikipedia page
shows that for an optimally streamlined body, the coefficient is 0.04.
The streamlined body is optimised for minimum drag, so I don't see how a ship hull could have even less drag.
Can you provide me with ballpark figures for the combined viscous and friction drag coefficient of typical ship hulls? I realize it varies a lot between different ship hulls but all I need is a rough estimate.