IMPORTANT: Read the following instructions before starting the assessment.

Time Allowed: This Final Assessment has been designed so that a well-prepared student could complete it within two hours plus an extra 30 minutes for submission.

Book Designation:

This assessment is open book, you are permitted to access your course manuals and other written material including online resources. However, the assessment must be your own work.

Format:

-      There are 4 QUESTIONS in this exam.

-     You must answer ALL 4 QUESTIONS.

-      The exam is 40 Marks with each Question worth 10 marks

-     An information sheet is provided for your reference, in a similar manner to the course tests.

Submission:

-      It is your responsibility to ensure your assessment is successfully submitted on time.

-     We recommend you aim to submit a couple of minutes in advance of the deadline, to allow time to deal with any technical issues that might arise.

-      This exam needs to be handwritten, either using paper and pen or digitally on a tablet. We will not accept typed answers.

-      The submission format is PDF. Please ensure that the file is perfectly readable before your

final submission. We also STRONGLY recommend you download your submitted document from Inspera, after submitting it, to verify you have uploaded the correct document

-      Make sure your calculation steps are neat and clear. State any assumptions made.

-      If an item of information appears to be missing, make a reasonable assumption and state your assumption clearly. See the “Support” and “Question Interpretation” notes on the next page.

-     Unless otherwise stated, you may assume that p = 1000 kg/m3  and g = 9.81 m/s2 .

-      Set your answers out clearly and legibly.  Incomplete or poorly presented answers whilst otherwise correct will not gain full marks.

-     Don’t forget to include the units of each magnitude.

Question Interpretation:

Please note that during the final assessment period you cannot contact your instructors for

clarification on how to interpret the wording of any specific questions or to verify that your answer is correct. Interpreting wording and making appropriate assumptions is part of what is being assessed.

You will need to interpret the question yourself and check your own answers.

Question 1 (Total 10 marks)

a)   A rigid cylinder with inside diameter of 15 mm contains a column of water 500 mm long. What will the column length be if a force of 2 kN is applied to its top by a frictionless

plunger? Assume a bulk modulus of 2.23 GPa. (2 marks)

b)   A submarine is situated 1000 m below sea level. The pressure inside the submarine is

controlled. If water inside the submarine boils at a temperature of 90°C, what is the pressure difference between the inside and outside of the submarine? Take the density of sea water as 1 023 kg/m3. (2 marks)

c)   A mercury manometer is used to measure the pressure in a vessel containing water as shown  in the figure below. The following measurements were taken: h1 = 150 mm and h2 = 300 mm.

i)    What was the pressure in the vessel at its center (point A) based on the measured values? (2 marks)

ii)   If the diameter of the pressure vessel is 2m, what is the pressure at its bottom?

Figure for Question 1c

(1 mark)

d)   The design of a new aquarium requires a semi-spherical glass window protruding into the

water, allowing children to look at the fish from different directions. A section through the

window is shown in the figure below. The centre point of the window is 12 m below the

water surface and it has a radius of 600 mm. Calculate the following: (Given: the volume of a sphere  =  πr3)

i)  The size and line of action of the horizontal hydrostatic force on the window. (2 marks)

ii) The size and direction of the vertical hydrostatic force on the window. (1 mark)

Figure for Question 1d

Question 2 (Total 10 marks)

a)   Explain what a Venturi Meter is and how it works. (2 marks)

Water flows from a reservoir (water level 3.4 m above datum) through a pipe of diameter 0.35 m

before passing through a 0.1 m nozzle and discharging as a free jet to atmosphere. This situation is   shown in the Figure for Question 1. The pipe system contains a horizontal section, a sloping section (with the same diameter as the horizontal section) and a Venturi Meter with a throat diameter of

0.13 m.

Figure for Question 2

b)   Assuming no energy losses in the system, calculate the discharge through the pipe. (2 marks)

c)   The water level h in the piezometer within the 0.35 m pipe section is 0.45 m above the centreline of the pipe. If the discharge coefficient of the Venturi Meter is 0.95, calculate the height of the

water level in the piezometer located at the throat (diameter = 0.13 m). (2 marks)

d)   Calculate the Reynolds number of the flow within the throat of the Venturi Meter, and describe whether this would change in a 1:10 scale model of the same system. (2 marks)

e)   State whether the water level in the downstream piezometer tube would be the same or different as that of the upstream piezometer tube, and justify your answer. (1 mark)

f)    The piezometer located at the throat of the Venturi Meter is replaced by a total head tube (also called a stagnation tube or pitot tube). Determine the height of water within the tube. (1 mark)

Question 3 (Total 10 marks)

The figure below shows a section through the inlet channel of a wastewater treatment plant. A screen is installed in the channel to remove solids from the wastewater, and a mechanical scraper

automatically cleans the screen when the flow depth at (1) reaches 2.3 m. Just after the screen is

t(l)tie(.)1(8).f(i)the(s)

screen opening area is blocked by solids and flow is only possible flow through the remaining 70 %).

screen

(1)                                                                              (2)

Consider a unit width of the system and answer the following questions:

a)   Calculate the flow rate through the system. (4 marks)

b)   Assuming both a constant flow rate and constant flow depth at (2), what fraction of the screen area will be blocked when the mechanical scraper is activated? (3 marks)

c)   Calculate the horizontal force of the wastewater flow on the screen just after it has been cleaned. Ignore friction losses in the channel. (3 marks)

Question 4 (Total 10 marks)

A pumping system in a city lying at an elevation 1 700 m above sea level is required to move water from a reservoir with a water level of 250 m to another reservoir with a water level of 290 m. The pipe system consists of a 250 mm diameter pipe with length 2 000 m and an absolute roughness of 0.1 mm. The secondary losses in the pipe has a total secondary loss coefficient of 30. If the required flow rate between the reservoirs is 50 l/s, work from basic principles to calculate the following:

a)   The total head that the pump system has to deliver. (3 marks)

b)   The pressure at the suction side of the pump. Assume that the pump eye is at an elevation of 252 m, and that it is situated 100 m from the intake point on the pipeline. Assume that one quarter of the secondary losses occur in the suction pipe. (3 marks)

c)   Determine whether the pump will be safe from cavitation if the NPSH required is 6 m. Assume a water temperature of 15 。C. (4 marks)