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  3. 2 a barge is used to tow the legs of...

Question: 2 a barge is used to tow the legs of...

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2. A barge is used to tow the legs of an oil rig out to the construction location 200km out in the North Sea. Each leg is 3m in diameter and 50m long. The barge owner is being paid a set rate for towing each leg. Due to weather conditions the barge can only operate with certairn tides and wind directions. The legs may be towed normal or parallel to the towing direction By calculating the drag and hence the power and total work to tow the legs in each orientation advise the barge owner which towing direction to use on the following days; (a) In a high spring tide when the tides reduce the barges speed to 7m/s. The sea temperature is 5 C. (14 marks) (b) In a low reach tide on a still summer day when the barges speed is 8.5m/s. The sea (7 marks) (c) Comment on further suggestions you might make to the barge owner based on your (4 marks) temperature is 12 C answers Temperature T Sea Water Density p kg/m 1028 Viscosity u Ns/m 1.88 x 10-3 .08 x 103 20 1025 the The coefficient of drag for turbulent flow about a cylinder is 0.3, you may assume the transitional Reynolds number to be 300,000 The coefficient of drag for laminar flow about a cylinder is shown in the table below L/D 1235 10 20 40 CD 0.74 0.82 0.91 0.981.2 For Reynolds numbers above 10,000 the coefficient of drag Co 1.0

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