- Assignment 2

Open Channel and Pipeline Flow:

Examiner: Jahangir Alam

Due Date: 23 May 2016

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 USQ’s Academic Integrity Policy and Procedure:

“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/documents/13752PL

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.

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 attempting 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 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 10% 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 60 marks

Question 2 – Surge Tank 50 marks

Question 2 – Cut Throat Flume 40 marks

Question 1 – Pipe Network (60 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.

Figure 1 – Pipe network for Q1

Pipe AB BC CD DE EF FA AD FH EG

Length (m) 220 500 250 150 550 150 200 300 450

Diameter (mm) 200 150 150 100 150 175 200 225 200

Roughness (mm) 0.15 0.1 0.06 0.25 0.06 0.15 0.15 0.25 0.06

a) Use the linearisation method to solve for the unknown discharges in each pipe of the network.

b) The pressure head at points H & G 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 )

HINT:

• The partial loop from H, F, E, G can be analysed as a normal loop once you account for the difference in energy (water level) between the reservoirs.

• Nodes H and G do NOT have node equations

• you only need to remove node equations if you have too many equations • You should end up with 3 loops

Question 2 – Surge Tank (50 Marks)

The first step in this question is to complete the tutorial problem 12.2 in the study guide. The question below can be completed by minor modification of the code written for that question.

A hydroelectricity plant is supplied from a reservoir via a pipeline 4.5 km long and 2.6 m in diameter. The pipeline terminates at its downstream end in a control valve. This pipeline is cast iron (lookup roughness)

Under normal operating conditions the hydro plant runs with a steady discharge of 15+ N1 cumecs, where N1is the second last digit of your student number

You have been given the task of determining the size of the surge tank which is to be installed at the downstream end of this pipeline and immediately upstream of the valve. This tank must be designed in order to deal with the surge that would occur when the valve downstream of the tank is closed completely and instantaneously

Surge Tank Design Criteria:

Unrestricted on inlet (FS = 0)

Maximum allowable water height= 4.0+ N2 m above level in reservoir.

(Where N2 is the last digit in your student number)

For example if your student number is Q1528616 then:

The steady discharge is =15+1=16 m3/s

Max allowable water height is = 4.0+ 6 =10m

Task:

a) Determine the minimum surge tank size (nearest ½ m) to satisfy the max. allowable height

For the case of complete closure (Q changes from 15+ N1 m3/s to Q = 0)

b) Plot the water level in the surge tank (relative to reservoir) over time for at least 2 upsurges

c) Plot the velocity in the pipeline over the same period (different set of axes).

HINT: The surge tank in the tutorial problem reaches a maximum height of approx 11.8m during complete closure

Question 3 – Cut Throat Flume (40 Marks)

A Cut-throat flume is to be constructed for measuring flow at a certain location of an irrigation channel. The shape of the channel cross-section is rectangular with a width of 2.5 m and the Manning roughness n is of 0.025.

The maximum flow rate (Qmax.) in the channel is 0.1+(0.05×N1)m3/s

The bed slope of the channel So is 0.001+(0.0001×N2)

Where, N1is the second last digit and N2 is the last digit in your student number.

For example if your student number is 0008006549 then

Max. Q= 0.1+(0.05×4)= 0.3 m3/s SO = 0.001+(0.0001×9)= 0.0019

Flume Design Criteria:

• Flume length (L) = 1.5 m

• Floor of flume is above channel bed

• Total Width (B) must be less than channel width, see figure 7-26 in Reading 16.1

• The ratio of Ha:L should be less than 0.4

• Maximum upstream afflux =0.1+(yn ×1.25) metres

The flume will discharge under free flow condition, which means you need to ensure that there will be no submergence at the downstream end, and eventually the flow at the downstream will be at normal depth yn .

Use the method and equations described in the selected reading 16.1 for the Module 16.

Your tasks:

a) Design the flume in terms of Length, Width and floor height, a proposed methodology

is as follows:

• Determine the normal flow depth

• Guess a flume width and determine appropriate coefficients

• Calculate Ha & Hb at max Q

• Determine a flume floor height (above bed) that ensures free flowing conditions but will not exceed the allowable upstream afflux

• Check against design criteria and revise width and floor height if required

b) Draw a sketch of your flume showing dimensions from TOP and SIDE views

c) Draw a rating curve (Q vs Ha) for the design range of the flume

d) Briefly discuss why a flume might be more appropriate than other forms of flow measurement for this situation

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, Wiley- Blackwell.

Kraatz. D.B. & Mahajan I.K. 1975, Small Hydraulic Structures, FAO Irrigation and Drainage Paper 26/2. FAO, Rome

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