1. Boundary Layer Theory: A brand-new ship is L = 750 ft long and has a...

 

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1. Boundary Layer Theory: A brand-new ship is L = 750 ft long and has a wetted area of 80,000 ft^2. Estimate its friction drag and the horsepower (in hp) required to overcome its skin friction drag for the smooth surface when the ship is moving at 14 knots (1 knot 1.69 ft/sec) in seawater at 60 degrees F. Model the problem as a two- sided smooth flat plate with an entirely turbulent BL on both sides. Now, consider if the ship is old and covered by roughness, and with the same hp, is moving at only 10 knots. What is the typical roughness height, epsilon. Do your work in the following order: a. Calculate the Reynolds number at the TE, that is, Re_L. b. Use Prandtl's turbulent BLT, with the 1/7th power-law velocity = profile to: c. Calculate skin friction drag coefficient CD for a smooth flat plate. d. Convert CD to drag force D per unit span, then for the entire span, then for both sides. e. Calculate power required to overcome D and convert to hp. f. Now calculate a new Re_L. g. Calculate a new D from the given hp, and convert to CD. h. Use Figure 7.6 of White or an equation, if appropriate, to estimate L/epsilon. i. Using L, the length, calculate epsilon. 1. Boundary Layer Theory: A brand-new ship is L = 750 ft long and has a wetted area of 80,000 ft^2. Estimate its friction drag and the horsepower (in hp) required to overcome its skin friction drag for the smooth surface when the ship is moving at 14 knots (1 knot 1.69 ft/sec) in seawater at 60 degrees F. Model the problem as a two- sided smooth flat plate with an entirely turbulent BL on both sides. Now, consider if the ship is old and covered by roughness, and with the same hp, is moving at only 10 knots. What is the typical roughness height, epsilon. Do your work in the following order: a. Calculate the Reynolds number at the TE, that is, Re_L. b. Use Prandtl's turbulent BLT, with the 1/7th power-law velocity = profile to: c. Calculate skin friction drag coefficient CD for a smooth flat plate. d. Convert CD to drag force D per unit span, then for the entire span, then for both sides. e. Calculate power required to overcome D and convert to hp. f. Now calculate a new Re_L. g. Calculate a new D from the given hp, and convert to CD. h. Use Figure 7.6 of White or an equation, if appropriate, to estimate L/epsilon. i. Using L, the length, calculate epsilon.

Answer rating: 100% (QA)

Given L 750 ft A 80000 ft v 14knots 14 x 169 2366 fts At 60F Pw 62364lbft v 12075 x 105 ... View the full answer