Estimating ship's powering 

L.K. Kupras' method 

At the initial stage of a ship's design a propulsion power estimation is to be done to ascertain that the vessel can sail at the specified speed. As the ship design development progresses, models tests are usually performed in a hydrodynamics tank, which serve to optimize the hull form, adjust the propeller(s) design and ensure the speed/power prediction for a proper choice of the propelling engine(s).