Propulsion.

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1 Propulsion Types of energy source: Animal power, usually human rowing, but horse-driven boats have been used (both owing with ropes from the shore in canals, and turning a on a treadmill linked to a propeller, aboard). Environmental power-gathering: wind power (sails), solar power (photovoltaic). Electrical propulsion in marine engineering refers to electricmotor-driven propellers, with electricity produced by heat engines, and not to direct electric sources, like batteries or solar panels, used in some small boats, and most small underwater vessels. Chemical fuels carried aboard, usually a petroleum-derivative liquid-fuel, taking advantage of the surrounding oxidizer in the air. Marine diesel is by far the most used fuel. Nuclear fuel, only used in nuclear submarines, using highly enriched fuel (>20 % U-235) in fission-reactors, usually of pressurized-water type (PWR), always through steam turbines (they are similar to external combustion engines). Rowing The goal in rowing is to make the unit (the rowers and the boat) cover the distance as fast as possible from the start to the finish. Physical performance is necessary to achieve this basic goal and the muscles of the human body produce the necessary energy. All movements have to be performed in a way that the rower is able to transfer his/her physiological performance into optimal propulsion. The long stroke is necessary to produce a high level of rowing performance. The movement of the rower has to be as horizontal as possible so that the vertical displacement of the centre of gravity is minimized without losing length in the stroke. The horizontal velocity of the rower relative to the boat should be as small as possible. Eight-person rowing shells can obtain speeds of 18 mph.

2 On December 26, 2015, British-born Canadian, John Beeden, 53, became the first person to successfully row non-stop, unassisted from North America to Australia covering 7400 nautical miles in 209 days. Sails The principle of physics behind aerofoil theory is Bernoulli s Principle. When wind comes in contact with the front of the wing, the air splits up and some air travels over the wing and some travels under the wing. Air travelling over the wing has a further distance to go than air that travels under the wing. In order to meet back up with the same air at the trailing end, air that has travelled over the wing has to travel further, so must travel faster. According to Bernoulli's priniple, the pressure above the wing is lower than the pressure underneath, so the is a net force lift the wing, and in fact the airplane attached to it. Much the same principle lies behind sails. When the wind blows and fills the sail, the sail becomes shaped like an aerofoil. how-sails-work.html

3 In 2012, the Vestas Sailrocket II achieved a speed of over 65 knots (75+ MPH) down the record course in Walvis Bay, Namibia Propellers A vessel's propeller works by thrusting a column of water away from the main body of the ship, thereby producing a reactive force that moves the boat forward. Most naval vessels use a screw-type propeller that transmits thrust through the main shaft to the thrust bearing. This reactive force reacts to the backward force of the water column to push the boat forward. Propeller blades rotate downward while water rushes in to fill the space left behind to create a pressure differential. Water accelerates from the front of the propeller towards the back, creating a column of water slightly bigger than the propeller itself. Higher velocity creates a water jet out of the rear of the propeller, which adds momentum and thrust to the water. This thrust moves the boat forward. Propeller blades work in water much like fan blades work in air.

4 Flow visualization of unsteady propeller blade loads OpenFOAM.shtml

5 The current World Unlimited Water Speed Record was set by an Australian motorboat racer named Ken Warby, in a wooden boat called the Spirit of Australia that he built in his back yard. On October 8, 1978, on the Tumut River near Sydney, Warby took the boat up to mph.

6 Weighing in at 131 tons, the - to date largest ship propeller drives the Emma Maersk, the world s largest container ship, with a load capacity of up to 14,770 twenty-foot containers, a length of 397 m.

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8 photo by Eric Greene