Ship resistance and propulsion

The total (upward) force due to this buoyancy is equal to the (downward) weight of the displaced water.

These can be split up into more components: Froude's method for extrapolating the results of model tests to ships was adopted in the 1870s.

To get the proper residuary resistance, it was necessary to recreate the wave train created by the ship in the model tests.

He found for any ship and geometrically similar model towed at the suitable speed that: There is a frictional drag that is given by the shear due to the viscosity.

(Main article: Skin friction drag) In a viscous fluid, a boundary layer is formed.

The boundary layer undergoes shear at different rates extending from the hull surface until it reaches the field flow of the water.

The divergent waves are observed as the wake of a ship with a series of diagonal or oblique crests moving outwardly from the point of disturbance.