Question 4 (10 marks) This question asks you to apply results you obtained in OEL 2.1: Flow around a cylinder (an used t

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Question 4 10 Marks This Question Asks You To Apply Results You Obtained In Oel 2 1 Flow Around A Cylinder An Used T 1 (102.4 KiB) Viewed 67 times

Question 4 10 Marks This Question Asks You To Apply Results You Obtained In Oel 2 1 Flow Around A Cylinder An Used T 2 (104.31 KiB) Viewed 67 times

Question 4 (10 marks) This question asks you to apply results you obtained in OEL 2.1: Flow around a cylinder (an used to answer Question 1) to a real-world problem. It uses concepts discussed in Chapter 10, Section 10.3 'Similarity and modelling? Polytunnel An agricultural polytunnel comprises a light metal framework with a thin plastic covering, as shown in Figure 3(a). u Х (a) 4 m (b) Figure 3 (a) A typical polytunnel; (b) a model of the polytunnel Its behaviour in wind can be modelled as a solid semicircle protruding into a uniform air flow, as seen in Figure 3(b). a. By equating Reynolds numbers based on diameter (note: the diameter of the cylinder in OEL 2.1 is 5 cm compared to 4 m for the agricultural polytunnel), estimate the wind speed Un equivalent to the air speed in the tunnel at which you measured pressures around the cylinder in OEL 2.1. (3 marks)

a. By equating Reynolds numbers based on diameter (note: the diameter of the cylinder in OEL 2.1 is 5 cm compared to 4 m for the agricultural polytunnel), estimate the wind speed Uco equivalent to the air speed in the tunnel at which you measured pressures around the cylinder in OEL 2.1. (3 marks) b. Use your results from OEL 2.1 to calculate the equivalent velocity at the top of the polytunnel (marked X in Figure 3(b)). Hint: you can expect the velocity at this point to be the same multiple of free-stream velocity as you observed in the wind tunnel in OEL 2.1. (3 marks) c. Assuming that the flow pattern does not change significantly, calculate the velocity and pressure at the top of the polytunnel when the wind is blowing at 20 ms-1. Give your answer as a gauge pressure relative to atmospheric pressure. (4 marks) < Previous Å Next > Question 3 (30 marks) Question 5 (15 marks)