Open Channel and Pipeline Flow Assignment

| November 16, 2015

ENV3104 Hydraulics II 2015 Assignment 2 1 Assignment 2 Open Channel and Pipeline Flow Examiner: M.H. Gillies Due Date: 25 May 2015 Weighting: 15% Objectives 1. Evaluate and apply the equations available for the description of open channel flow 2. Solve simple pipe networks using an appropriate method 3. Apply rigid and elastic water hammer theory to the analysis of pipeline systems 4. Design a range of hydraulic structures including: fixed and movable crest weirs; gated control structures; pipe conveyance structures; spillways and energy dissipation structure; critical flow measuring flumes; gulley control structures ; weir and culvert type structures using the minimum specific energy concept. Rationale This assignment is based on the material covered in this course. As such you will be directed to attempt tutorial questions from modules 10, 12 and 16 before starting this assignment Important Information Before starting please review the policy of Engineering and Surveying Faculty: “All assessable work in a course is to be the individual student’s own work, unless advised otherwise in the Course Specification. It is unacceptable for students to share solutions to assessable work on this Study Desk site, or in any other manner. Violations of this principle are regarded as Academic Misconduct and will be dealt with under the USQ Academic Regulations.” For guidance on what constitutes Academic Misconduct and its various categories, at USQ refer to the USQ Student Academic Misconduct Policy available at: http://policy.usq.edu.au/portal/custom/detail/definitions/index.html By submitting this assignment you hereby certify that: The submission is entirely my own work except where due acknowledgement is made in the text and that no part has been copied from any other person’s work. ENV3104 Hydraulics II 2015 Assignment 2 2 Special Instructions a. Computer programs or spreadsheets must be the work of the individual student. b. Assignments can be validated by using a similar problem where the solution is known c. A proportion of the marks is allocated to the communication aspects of the assignment. Marks will be deducted for untidy and poorly presented work, poor English expression, and failure to cite sources of information. d. This assignment is based on the material contained in Modules 10, 12 & 16. It is essential that students attempt the tutorial problems for these modules before completing the assignment. e. Plagiarism is taken seriously in this course, as such your assignment report will be checked using Turnitin and your spreadsheets (if you have chosen to use Excel or equivalent) will be checked for plagiarism using Excel-Smash Instructions for Submission Submission for this assignment is in two parts: – Report introducing the problem, description of the methods and equations used, results and brief discussion. – Electronic copy of all computer code or spreadsheets used so the examiner can validate the models (ALL within a single Zip File) The report should be compiled in such a manner that assessment can be completed without access to the electronic copies of the code/spreadsheet files The assignment is to be submitted electronically via study desk. The link is available on the course studydesk. Please note that hand written equations or working within the body of the report are permitted. Late Submissions If students submit assignments after the due date without (prior) approval of the examiner then a penalty of 5% of the total marks gained by the student for the assignment may apply for each working day late up to ten working days at which time a mark of zero may be recorded. No assignments will be accepted after model answers have been posted Assessment Task This assignment is comprised of three (3) questions with the marks allocated as follows Question 1 – Pipe Network 65 marks Question 2 – Surge Tank 50 marks Question 2 – Control Structure 35 marks ENV3104 Hydraulics II 2015 Assignment 2 3 Question 1 – Pipe Network (65 Marks) A pipe network as shown in Figure 1 has been constructed in order to convey water from two reservoirs (G & H) to a number of delivery points. The details of each pipe are given in the table below. You may also neglect all minor losses that may occur in the system. A B C D E F I G 50 L/s 45 L/s 20 L/s 40 L/s 50 m 30 m (2) (1) (3) (4) (5) (6) (7) (10) (8) (10) H (9) Figure 1 – Pipe network for Q1 Pipe AB BC CD DE EF FA AD EG GH IF Length (m) 220 500 250 150 550 150 200 220 1000 200 Diameter (mm) 200 150 150 200 150 100 200 250 250 200 Roughness (mm) 0.15 0.06 0.06 0.25 0.06 0.06 0.15 0.25 0.25 0.15 a) Use the linearisation method to solve for the unknown discharges in each pipe of the network. b) The pressure head at points H & I is given in terms of metres head of water. Assuming the network is situated on a level grade estimate the pressure head in metres at each pipe junction (A, B, C, D, E, F,G ) HINT: The open loop from H to I can be analysed as a normal loop once you account for the difference in energy (water level) between the reservoirs. The difference between I and H will remain constant. ENV3104 Hydraulics II 2015 Assignment 2 4 Question 2 – Surge Tank (50 Marks) A hydroelectricity plant is supplied from a reservoir via a 5km, 1.8m diameter steel pipeline with roughness of 0.035mm. The pipeline follows the ground surface which has a constant grade and drops by 10m over the length of the pipeline. The water level in the reservoir is maintained at a constant 20 m above the inlet end of the pipeline. A surge tank, with diameter of 5.0 metres (Fs = 0.9) is positioned at the end of this 5km pipeline in order to mitigate any pressure surges due to changes in flow rate. For the purposes of modelling you may assume that varying the flow in the hydroelectricity plant has the same impact as a valve positioned immediately downstream of the surge tank. At time zero the hydro plant is stopped with zero flow in the pipeline. The turbines in the plant are enabled to ramp up to full speed slowly over a period of 110 seconds. At full speed the discharge to the turbines is 9 m3 /s. Model the flows within the pipe and surge tank using the numerical solution technique (equations 12.21 & 12.22) described by Marriott (Nalluri and Featherstone) in Section 12.4. You should use a time step of 5 seconds or smaller and account for the change in f with velocity. From your model produce plots of a) the variation of water level in the surge chamber expressed relative to the ground level at the surge tank over time b) the variation of velocity in the tunnel over time Plot each of these over a time of 15 minutes. c) Discuss why the surge tank was incorporated into the design of the system Important Hints: – The z in the equations is the water level relative to the zero flow water level in the surge chamber. – A diagram will be very useful in understanding the system. ENV3104 Hydraulics II 2015 Assignment 2 5 Question 3 – Control Structure (35 marks) An irrigation scheme is fed from a river via a diversion channel. The irrigation channel is 3 m wide and is constructed of concrete with an estimated value of 0.019 for the Manning n. The bed slope is 0.001. The discharge into the channel is controlled by a vertical sluice gate (Cc = 0.61). The depth upstream of the gate is a constant 3.0 m, and the maximum discharge is 9 m3 /s. The designer of the gate has started to prepare a rating curve for the sluice gate (YG vs Q) for free flowing conditions as shown below in the table. The issue is that the designer did not have time to finish the job and is missing the gate openings for a number of flow rates. The depth on the downstream side of the gate is equal to the normal flow depth. Independently you have determined the normal flow depths over the operating range of discharges, which is also included in the table below. Q yg yg yn or y3 (assuming free flowing) (For submerged) (normal flow D.S. of hydraulic jump) (m3/s) (m) (m) (m) 1 0.0718 ?? 0.4207 2 0.1443 ?? 0.6694 3 0.2181 ?? 0.8871 4 0.2933 ?? 1.0890 5 ?? ?? 1.2812 6 ?? ?? 1.4667 7 ?? ?? 1.6473 8 ?? ?? 1.8242 9 ?? 0.7807 1
.9981 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 0.0 0.2 0.4 0.6 0.8 1.0 Flow Rate (cumecs) Gate Opening (m) Assuming Free Flowing Assuming Submerged Figure 2 – Gate rating curve (a) Calculate the missing gate opening assuming free flowing (b) Determine at what discharge the gate changes from freely flowing to submerged conditions (to the nearest m3 /s). (c) Calculate the new gate opening (YG) for those discharges for where the gate is submerged by the depth downstream of the gate. (d) Finish the rating curve HINT: See section 13.8 and Example 13.1 in Chadwick et al. (provided on Studydesk) ENV3104 Hydraulics II 2015 Assignment 2 2 References Chadwick, A., Morfett, J. And Borthwick, M. 2004, Hydraulics in Civil and Environmental Engineering. 4th Edition E & F N Spon. Marriott, M. 2009, Nalluri and Featherstone’s Civil Engineering Hydraulics. 5th Edition, WileyBlackwell.

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