Important information – please read carefully:

Instructions:

This assignment is worth 90% of the overall module marks for EG-362

•   The solutions may be handwritten (including electronically) or typed. If you                handwrite your solutions on paper, you can either scan them as a single document or  take a photo of each sheet and insert each photo into a single word processing file and submit it as a portable document format (PDF).  Scanning applications are                  recommended. Two such apps are below (you may use other applications that you are familiar with):

Microsoft Office Lens1

Adobe Scanner App2

•   Before submitting your assessment, review the document for readability considering the following?

Ø Are images clear and in focus?

Ø Are the images easy to read?

Ø Are the images oriented in the correct way?

Ø Will the marker/moderator be able to read and mark your work easily?

•   Include the method steps you have followed to obtain your answers in your submission.

•   Clearly state your student number on each page of your submission.

•   Please allow plenty of time for uploading your assessment before the submission time.

•   Canvas will allow multiple submissions.  Only the last submission will be marked.

For this assessment:

Answer ALL questions

Time allowed to complete this assessment:  4 hours

Submission date and time:  27 May 2022 at 14h00.                                                Students who have been allocated extra time have been contacted individually.

Submission method:   Submission through Canvas. Link below:

https://canvas.swansea.ac.uk/courses/25341/assignments/220958

This is an open book assessment, which means you can access appropriate academic sources  to help you complete your assessments as necessary. If you are using books or websites other than those provided by your lecturer(s) or given in the module reading list you must reference these in the usual way.

For more information regarding referencing follow the link below:

Engineering – Referencing: https://libguides.swansea.ac.uk/Engineering/Referencing

•   This is an individual assessment; working in groups, helping or receiving help from other students or third parties is not permitted. The work you submit must be your own work.  The usual University regulations regarding academic misconduct apply.  For further information regarding Academic Misconduct please follow the links:

Academic Misconduct Procedure3

•   To  check  you  have  successfully  submitted  your  assignment,  please  go  into  the ‘Assignments’ area and click on the assignment title. In the top right-hand corner, you should see the text ‘Submitted’ and confirmation of the submission time.

•   Please make sure you retain any evidence of submission, should there be any query at a later date.

•    If you  have  circumstances  that  impact  your  ability  to  complete  or  submit  your assessment  by   the   deadline,   you   may  be   eligible   to   submit   an   Extenuating Circumstances request. Please see the following webpage for guidance –

https://myuni.swansea.ac.uk/academic-life/extenuating-circumstances/

•     If you experience IT issues during your assessment, you can contact the University’s Customer Service Team either by emailing [email protected] or calling +44 (0)  1792 295500. For issues relating to Quizzes, you can email the Faculty’s Assessment Team via – [email protected]

•    For queries relating to student support and/or provisions, please contact the Student Support Team: studentsupport-scienceengineering@swansea.ac.uk

Question 1

(a) Figure 1a shows a commercial vehicle and a car. Sketch carefully the detail flow patterns that you would expect to find for each vehicle where the fluid has ideal and real properties. Also for each case, provide a brief explanation of the flow pattern you have presented and include in your discussion any likely pressure variations that occur over the vehicle body. If both vehicles are travelling at the same speed, why will the aerodynamic forces differ. (You may wish to copy the image into your answer document).

[9 marks]

Figure 1a: Truck and Car Profiles (from Freevector)

(b) A fluid film is used to clean a fixed surface as shown in Figure 1b below for an angular setting of θ .  Starting from first principles, derive an expression for the shear stress that is exerted on the surface, explaining and justifying any assumptions that you make.

[8 marks]

Film thickness h

θ

Figure 1b: Fluid Flow Down an Inclined Surface

(c) The Figure 1c below shows an experimental truck that is used to explore its aerodynamic performance.  The vehicle aerodynamics is to be modelled using CFD.  With the aid of sketches, explain how you would undertake an initial study, explaining any assumptions that you would make and how you would set up the computational domain to undertake the study, also paying particular reference to the boundary conditions that you would apply.

[8 marks]

Figure 1c: Experimental Truck (from Aerodyne UK)

[TOTAL 25 MARKS]

Question 2

(a) What is boundary layer flow and what are the key assumptions used in simple analytical solutions. What are the outputs from simple solutions and to what practical configurations do they apply most closely and why.

[5 marks]

(b) In turbulent flows contrast the approaches that are used to represent the velocity profile within the boundary layer and comment on any limitations that each may offer.

[5 marks]

(c) Figure 2a below shows the outline of a structure on which pressures are measured and the consequent pressure gradients calculated.  The pressure gradients shown are positive zero and negative.   Using sketches show the velocity profile that you would expect in each region and explain the balance of stresses that are present in each. This should include any progressive changes that you would expect within each region.

[7 marks]

Negative pressure gradient zone

Zero pressure gradient zone

Positive pressure

gradient zone

Figure 2a: Structure Outline and Pressure gradient Zones

(d) A round bar shown in Figure 2b is mounted on the end of a motor shaft at its central fixing point.  The bar is used to provide an aerodynamic load on the motor. By assuming that the air flow around the shaft is everywhere turbulent, calculate the power absorption by the shaft for a rotational speed of 2000 revolutions per minute.   The geometry is d=0. 1m, L=1.0m.  Explain any assumptions that you make and justify all parameter choices.

[8 marks]

L/2                      

Central fixing

Figure2b: Power Absorption Bar

[TOTAL 25 MARKS]

Question 3

(a) A centrifugal pump, with  salt water as the working fluid, has the impeller blades rotating at 750 rpm. The fluid enters the blades in the radial direction, i.e. at an angle of a1  = 0o , and exits the blades at an angle of 35o  from the radial direction. i.e. a2  = 35o .  The  inlet  radius  and  blade  width  are  T1  = 12.0 cm   and     b1  = 18.0 cm, respectively. The outlet radius and blade width are T2  = 24.0 cm and  b2  = 16.2 cm, respectively. Assuming 100 percent efficiency, and if the volumetric flow-rate through the pump is 0.573 m3/s, compute the net head produced by the centrifugal pump. Furthermore, calculate the required brake horsepower in Watts. Take the density of salt water to be p = 998.0 kg/m3 .

[8 marks]

(b) The Figure below shows a Rotor-Stator assembly in an axial flow pump.

Rotor                         Stator

T!1

in

!1                                             T

The volumetric flow-rate through the pump is 0.4 m3/s, the average open cross-       sectional area through the impellers if 0.06 m2, and the impeller blades rotate at 500 rpm. At a radius T=25cm:

i.          draw the velocity diagram at the leading edge of the rotor.

[3 marks]

ii.         compute the rotor leading edge blade angle.

[4 marks]

(c) For a Pelton wheel with a fixed turning angle  (less than 180o ), radius T (T > 0), fluid density p, jet velocity Vj , volumetric flow rate v̇ , and angular velocity  , the angular velocity  and radius T are constrained by the following relation

  = k rn

where k and n are positive integer constants. For this design:

i.      Derive an expression for the ideal shaft work.

[2 marks]