CEGE0026: Fluids and Soils III
Alternative Assessment – 2019/2020
The Assessment is worth 50% of the total module
- Answer ALL questions. Question 1 is on Fluids [pages 2-7]; question 2 is on Soils [pages 8-9].
- Your submission should not exceed 1,500 words, excluding references and figures. A penalty of 10% on the overall mark will be applied for submissions exceeding the word limit. Messy presentation will also be penalised.
- This assignment should take you half a day to one day of solid work (about 4-6 hours) to complete.
- Marking guidelines are appended at the end of the assignment.
- Only one upload is required for submission. Submissions may be typed or hand-written, and may include diagrams, formulae etc. where appropriate.
- Please insert a table as shown below on the front page of your submission:
|Number of figures|
|Number of tables|
Question 1 [50 marks]
You have been tasked to use your knowledge from Fluids III to analyse the flow of a South American river as allocated in Table Q1a. The information in Table Q1a and Figures Q1b and Q1c have been taken from Sichangi et al (2016). You have been allocated a river as shown in the Table Q1a, and you must use data for your allocated river to solve the question. You may want to refer to the original source for a more complete understanding of the problem, however the elements that are being tested in this question are based on your Fluids III knowledge – not the new concepts that are the focus of Sichangi et al (2016).
Please answer the following questions for your allocated river. If you answer the questions for a different river you will only be marked for the methodology.
(a) Use Manning’s equation with the information in Table Q1a, Figures Q1b and Q1c (ignore H0 values) to estimate the maximum and minimum river flow velocity. Briefly provide explanations of any assumption used in your analysis/calculations. If required extend your river banks vertically upwards at either side of the river banks (do not extend the width of your river basin).
(b) How do your results compare with the given discharge values in Table Q1a? Provide an assessment of your analysis.
(c) You have been tasked to draw and annotate a specific energy curve for your allocated river. In your analysis you should include the Froude number and the critical flow properties (water depth, energy and velocity). For this assume that the river discharge per unit width ( ) is constant and is given as where is the river discharge (m3/s) (use the discharge value from Table Q1a) and is the river width (m). State and explain any additional assumptions that you have used in your analysis.
(d) The next stage of the river analysis will require some Computational Fluids Dynamics modelling. It is proposed to use a Reynolds Averaged Navier-Stokes method. You have been tasked to provide an explanation of (1) by identifying the physical properties of the flow that are picked-up using this model.
where ( ) are the horizontal, vertical and depth velocity components, is time, is pressure, is kinematic viscosity ( ), ) are the velocity fluctuation and ( ) are the horizontal, vertical and depth axis.
Table Q1a: River allocation and properties
|Discharge (m3/s)||Slope||Length (km)|
|Negro (Sao Felipe)||
|Amazon (Santo Antônio do Iça)||
|Amazon (São Paulo de Olivencia)||
Figure Q1b: River cross sections taken from Sichangi et al (2016).
Figure Q1c: River depth estimates (ignore H0 values) taken from Sichangi et al. (2016) Fig 5.
Sichangi, A.W., Wang, L., Yang, K., Chen, D., Wang, Z., Li X., Zhou, J., Liu W. & Kuria, D. (2016). Estimating continental river basin discharges using multiple remote sensing data sets. Remote Sensing of Environment, 179, 36-53.
Question 2 [50 marks]
Figure 2 shows a schematic diagram (not to scale) of a smooth retaining wall founded on impermeable ground. The aim of this exercise is to determine the force resulting from active earth pressures exerted at the back of the wall, using different approaches and comparing them.
The retained ground is silty clay, with properties shown in the figure. The water table is at the retained ground surface. For each approach, you are expected to describe the assumptions and the different steps taken, with detailed text as well as equations. You will also need to show, for each approach, that the force you have calculated is the optimum one for design. Note that the word numbers provided for each sub-question are only suggestions of how you may want to divide your text between them.
(a) Calculate the active force on the wall by using an upper bound approach. The failure mechanism can be assumed to be a plane. You must show the velocity (displacement) diagram.
(b) Calculate the active force on the wall using Coulomb’s approach.
(c) Compare the answers in (a) and (b) with what would be predicted using Rankine’s approach, and comment.
END OF ASSESSMENT
Exemplary (90%-100%): Fulfilled all the required tasks with an exceptional level of insight, thoroughness, and originality. Comprehensive yet clear and concise. Impeccable English and presentation.
Outstanding (80%-89.99%): Fulfilled all the required tasks to a very high standard with no significant error but may be lacking slightly in some aspects of secondary significance (e.g. conciseness or some minor presentation flaws).
Very Good (70%-79.99%): Shows an understanding of the problem and how to solve it. Got everything right except for a few minor errors, inaccuracies or presentation flaws.
Good (60%-69.99%): Good understanding of the problem and how to solve it. Got most of the results right but made a few mistakes or showed some slight misunderstandings. Good overall presentation but may be lacking in a few places.
Satisfactory (50%-59.99%): Shows a Satisfactory understanding of the problem and solves a significant fraction of it correctly but may contain some serious mistakes or misunderstanding. Presentation acceptable but can be poor in places.
Fair (40%-49.99%): Most requirements attempted but shows limited understanding of the problem or detailed knowledge. Contains mistakes, misunderstandings, or irrelevant material. Organisation and expression and presentation inadequately poor and standard or presentation.
Fail (0%-39.99%): Very limited understanding of the question asked and how to answer it. Some marginally relevant material and limited content but badly organised with frequent errors and misconceptions. Serious weaknesses in presentation. Also applies to submissions that are most completely irrelevant, messy or missing altogether, or submissions showing clear plagiarism.
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