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OCE 3016 Home Work 5 Environmental Loading 1. Define the following: a. b. c. d. e. f. g. h. i. j. shear stress normal stress drag force inertia force buoyancy force pressure drag flow separation wake vortex horseshoe vortex Reynold’s Number 2. Consider the water flow around the cylinder shown in the figure. Sketch the slow field around the cylinder in both the side and top views. 3. Describe what happens to the drag force on a sphere when the surface is roughened. 4. Estimate the drag force (in lbf) on a score board at the end of a stadium when the wind is blowing directly at the board at 50 miles/hr. The board is 20 ft tall and 30 ft long. The mass density, ρa, and dynamic viscosity, µ, of the air are 0.076 lbm/ft3 and the 0.121 x 10-4 lbm/s ft respectively. Use the attached graph to determine the drag coefficient. 5. Estimate the terminal velocity of a 130 lbf parachutist if the diameter of the parachute is 30 ft. The mass density and dynamic viscosity of the air is the same as in problem 4. If her 200 ibf friend uses the same parachute what will be his terminal speed? a. A steady current of 6 knots (nautical miles per hour) is flowing past a piling in the water as shown in the figure. If the water depth is 20 ft and the mass density and dynamic viscosity are 62.27 lbm/ft3 and 6.733 x 10-4 lbm/s ft respectively estimate the drag force on the pile. 1 ft dia. 20 7. Compute the instantaneous force on the pile in problem 6 by a wave with a height of 8 ft and a period of 6 s at the time when the crest is at the centerline of the pile. What would the force be if the period of the wave were 8 s? What would the force be if the pile were 6 ft in diameter (6 s period)? ADVANCED PROBLEM Consider the wind anemometer shown in the figure. The wind speed is related to the revolutions per minute (rpms) of the cups. By measuring the rpms of the cups the wind speed can be estimated. 2 in. Hemispherical Cup 1 in dia. Top View a. If the anemometer is locked in position shown in the figure what are the forces on the cups and the moment about the axis of rotation when the wind speed is 20 miles/hr? Assume ρa and µ are the same as in problem 4. b. If the anemometer is now allowed to spin what is the terminal rpm of the cups when the wind speed is 20 mi/hr? Assume that the friction in the bearings is negligible. c. Determine the relationship between rpm and wind speed for this anemometer.