As the water flows aft at greater speed, its kinetic energy increases. It is not the increase in the draft as visually read or as shown on draft indicators.īernoulli’s theorem states that in any moving fluid, the sum of the potential energy, the kinetic energy, and the pressure energy is a constant. The squat is the decrease in under-keel water, that is, the difference between her under-keel clearances when making way and when stopped over the water. This is assuming that they are on even keel when stationary. For fine-form vessels such as passenger liners or container ships the grounding will generally occur at the STERN. If the ship moves forward at too great a speed when she is in shallow water, say where this static even-keel under keel clearance is 1.0 to 1.5 meters, then grounding due to excessive squat could occur at the Bow or at the Stern.įor full-form ships such as Supertankers or OBO vessels, grounding will occur generally at the BOW. It is not the difference between the draughts when stationary and the draughts when the ship is moving ahead. The overall decrease in the static under keel clearance, for’d or aft, is called Ship Squat. This causes a drop in pressure, resulting in the ship dropping vertically in the water.Īs well as dropping vertically, the ship generally trims for’d or aft. The streamlines of return flow are speeded up under the ship. In order not to leave a 'hole' in the water, this volume of water must return down the sides and under the bottom of the ship. When a ship proceeds through water, she pushes water ahead of her.

Grounded vessel meaning