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Unformatted text preview: then determine ¢ p j real from ¢ p j model ? The propellor of a 150 m long cargo ship is 2.5 m in diameter and rotates at 100 rpm under normal operating conditions. A 1:100 scale model of the ship and its propellor is to be tested in a towing tank to ¯nd the drag force on the ship that the propellor must overcome. It is known that °ows near free surfaces depend on g , whereas e®ects of water viscosity on this °ow can be neglected. 1. Which dimensionless groups must be matched to ensure dynamic similarity? 2. At what rpm should the model propellor rotate? 3. If the drag coe±cients of the model and the fullsize ship are the same, what is the ratio of power expended by each?...
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 Fall '11
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 Surface tension, 2 m, 1 m/s, model propellor rotate

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