cee4324-5984-f11hw9_solutions

cee4324-5984-f11hw9_solutions - Virginia Tech Department of...

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1 Virginia Tech Department of Civil and Environmental Engineering CEE 4324/5984 – Open Channel Flow Homework #9: Qualitative and Quantitative Surface Water Profiles Due November 29, 2011 All solutions are shown in yellow. Problem 1: (4 points) Given the junction of two rectangular reaches, “A” and “B”, carrying a discharge of 200 ft 3 /s as follows: Upstream Reach – “A” Downstream Reach – “B” Channel Width (feet) 10 feet 10 feet Channel Roughness – Manning’s n 0.030 0.030 Channel Slope (ft/ft) 0.02 0.005 Critical Depth (feet) 2.32 2.32 Normal Depth (feet) 2.16 3.51 Reach type (Mild, Critical, Steep) Steep Mild Conjugate to Normal Depth (feet) 2.48 1.43 (a) Fill in the missing entries in the last four rows of the above table. (b) Does the hydraulic jump appear on the upstream (“A”) or downstream (“B” reach? Justify your answer. Answer: The jump appears on the upstream reach (“A”) because the normal depth on the upstream reach (2.16 feet) is bigger than the conjugate to normal depth on the downstream reach (1.43 feet). We expect a jump on the upstream reach from normal depth to the conjugate to normal depth (to 2.48 feet) followed by an S 1 curve reaching 3.51 feet at the break in channel slope. The water flows at normal depth for the entirety of the downstream reach. (c) Using normal depths as the upstream (entrance) and downstream (exit) conditions, sketch the flow profile through the two reaches. Label all profiles and indicate all key depths. Answer: Please see the sketch on the following page. (d) Answer the appropriate one of the two questions below: a. If your answer to Problem 1(b) above placed the jump on reach “A”, what is the least steep new slope for reach “A” such that the jump moves downstream to reach “B”? Answer: This is the case that applies. This is the equivalent of
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This note was uploaded on 12/24/2011 for the course CEE 4324 taught by Professor Moglen during the Fall '11 term at Virginia Tech.

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cee4324-5984-f11hw9_solutions - Virginia Tech Department of...

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