Sample/practice exam 6 June 2017, questions and answers - Fluid Mechanics And Hydraulics PDF

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Exam Review Notes: Final Exam The questions in this revision lecture will NOT be necessarily in the exam. To receive a grade of 4 or better for the course, the student must: 1) achieve an aggregate mark of at least and 2) achieve at least for the exam. 1 WORKING TIME: 3 Hrs 00 Mins PERUSAL TIME: 10 ...

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Exam Review Notes:

Final Exam 

The questions in this revision lecture will NOT be necessarily in the exam.

 

To receive a grade of 4 or better for the course, the student must: 1) achieve an aggregate mark of at least 50% overall; and 2) achieve at least 40% for the exam.

   

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WORKING TIME: 3 Hrs 00 Mins PERUSAL TIME: 10 Mins EXAMINATION TYPE: Closed Book (tables and formulae will be provide) MAKE A REALISTIC ASSUMPTION AND STATE THAT, IF REQUIRED. PERMITTED MATERIALS : CALCULATOR: Scientific calculator DICTIONARY: Electronic dictionaries are NOT permitted.

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Structure of the Final Exam

Q1. (Part A – Multiple Choice)

Part A (40 marks) short Answer Multiple Choice • Calculation • Missing word/brief description Choose the most appropriate choice Parts B (60 marks) Problems • Workout Problems

Based on the following equation, 1 Pascal is equivalent to:

(A) (B) (C) (D) (E)

USE 2B PENCIL TO MARK THE ANSWERS OF PART A ON THE MARK SENSE CARD

1 N/m 1 kg/(ms2) 1 kgm/s2 1 kgm2/s2 None of the above

p   g z

USE 2B PENCIL TO WRITE ANSWERS OF PART B ON THE EXAM PAPER Content: From Week 1 to Week 12

This examination is worth 60% 3

Ans. B 4

Q3. (Part A)

Q 2. (Part A – Multiple Choice) The phenomenon shown in the following photographs is the result of ________.

The figure shows a mercury/water manometer with one side open to the atmosphere (101 kPa). Given that the mercury has a specific gravity of S = 13.6, find the absolute pressure at the point A.

(A) Hydraulic jump (B) Surface tension (C) Vortex shedding (D) Cavitation (E) None of the above

(A) 56.8 kPa (B) 23.8 kPa (C) 14.9 kPa (D) 95.8 kPa (E) None of the above Ans. D (Cavitation)

A.

SHg = 13.6

What is the velocity of the water at the exit of the tee shown in the figure? All pipes have circular cross sections. A. 5 m/s B. 4 m/s C. 1 m/s D. 8 m/s E. None of the abov

30 m

Ans. 882E6 N, 20m 7

15 cm

Q 5. (Part A)

F  gh A  pA

40 m

Water

10 cm

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The dam wall shown in the figure is 200 m wide. Find the resultant hydrostatic force acting on the dam wall (and centre of pressure) assuming that the submerged surface is rectangular. (A) 882E6 N, 15m (B) 4.41E6 N, 20m (C) 882E6 N, 20m (D) 4.41E6 N, 15m (E) None of the above

Swater = 1.0

Ans. 95.8 Kpa 5

Q 4. (Part A)

p   g z

Ans. None of the above 8

Q 6. (Part A)

Q 7. (Part A)

The top of the reservoir containing water is open to the atmosphere. A 5 mm diameter orifice is located 290 mm below the free surface. Neglecting viscous losses, estimate the velocity of the fluid through the orifice. (A) 5.68 m/s (B) 2.38 m/s (C) 14.9 10-6 m/s (D) 1.15 m/s (E) None of the above Ans. 2.38 m/s

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Q 8. (Part A)

A solid spherical buoy with a density of 300 kg/m3 is tied to submerged post as shown. Find the tension in the cable if the diameter of the buoy is 0.6 m

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cable

Ans. 801 N

Q 9 (Part A)

Q  VA

The momentum equation is a statement of … and relates the sum of the … acting on an element of fluid to its … or rate of change of momentum A. B.

Q = 0.5 L/s

C. D.

pump

salt water ( = 1023 kg/m3)

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E.

water 20C

FB   gDisplaced

(A) 1603 N (B) 801 N (C) 401 N (D) 1204 N (E) None of the above

Water is pumped continuously around the loop in a steady state. The flow rate over the spillway is 0.5 L/s. Neglecting evaporation, find the average velocity of the water inside the 25 mm diameter pipe. (A) 2.028 m/s (B) 0.019 m/s (C) 1.02 m/s (D) 0.51 m/s (E) None of the above

Vsphere  43 r 3  16  D3

Newton's Second Law / forces / acceleration Newton's Laws / mass / acceleration Newton's Second Law / forces / flow rate Newton's Laws / force / acceleration None of the above

25 mm inside diameter pipe

Ans. 1.019 m/s

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Ans. A

Q 10.(Part A) 

Q 11. (Part A)

Which equations can be used to estimate force on this bended pipe? A. B. C. D. E.

Q  VA V  0.85 C HW Rh 0.63 S e 0.54

Water flows from a reservoir through a 4 km long pipeline as shown. Calculate the discharge if the diameter of the pipe is 0.25 m and the CHW= 140.

Continuity Equation Bernoulli Equation Momentum Equation Either a or b or b and c a, b and c

water 10C

L = 4 km D = 0.25 m

100 m

(A) 0.14 m3/s (B) 1.02 m3/s (C) 2.04 m3/s (D) 0.51 m3/s (E) None of the above Ans. Q=0.139 m3/s

Ans. E

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Q 12. (Part A)

Re 

VD 

Fr 

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Q 13. (Part A)

V gDc

Reynolds number and Froude number are the ratios of the following forces, respectively. A. B. C. D. E.

q2 2gy 2

yc  3

q2 g

Water flows in an open rectangular channel 5 m wide with a velocity of 2.0 m/s. The depth of the water is 0.9 m. Which of the following is the alternate depth?

Kinetic and Viscous, Kinetic and gravitational Kinetic and gravitational, Kinetic and Viscous Kinetic and Viscous , Kinetic and surface tension Kinetic and gravitational, Kinetic and surface tension Kinetic and Viscous, Kinetic and shear

(A) 0.10 m (B) 0.69 m (C) 0.54 m (D) 1.11 m (E) None of the above

Ans. A 15

E y

16

Ans. 0.543 m

Q 14. (Part A) What is the friction factor of an asphalt cast iron pipe with a diameter of 100 mm and a discharge of 45 Lit/s of water with T=20 o C? A. B. C. D. E.

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Ans. 0.021

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SEC and SET evaluation forms www.griffith.edu.au/ experience

The Moody Diagram 

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0.043 0.010 0.032 0.021 Not enough information given

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Exam Q. (Part B) What power needs to be supplied by the pump to the water for a discharge of 0.5 L/s?

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LV2 h  f L V L P  m gh p D 2g D 2g p1 V1 2 p2 V2    z  hp  z  2 2  hLtot  hT g 1 12 g g 2 2g

40 m of 25 mm (inside diameter) galvanized pipe (ks = 0.15 mm)

Kexit = 1.0

8m

The Moody Diagram

hL  f

20 m

water 20C Q = 0.5 L/s Kinlet = 0.5

pump Ans. P=74.14 W

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22

V0 2 2 VD Re  

Q 1. (Part B)

FB   g DisplacedFD  C D A p 

A submerged spherical buoy (diameter 0.5 m, density 200 kg/m3) is in a current flowing with a velocity of 0.2 m/s. The buoy is tied. Neglecting drag on the cable and the weight of the cable, determine the angle that the cable makes with the vertical and the tension in the cable.

0.2 m/s

 =?

23

water, 20C

24 Ans. 0.21o, 511.9 N

Three-Dimensional Bodies 

Drag Coefficient,  Function

CD

of Reynolds

Number, Re

Sphere: (Red < 300,000)

CD 





24 1  0.15 Red0.687 Re d 0.42   1 42500 Red1.16

Figure 11.8, Crowe et al. (2009) 26

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Q 2. (Part B)

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air :

1 1  0.2Ma 2  A    A* Ma  1.2 

 k 1  k 1 2  2 Ma 2  Tt  T1 1  Ma1   T 21  2 2    

Air is drawn through the 50 mm entrance diameter of a de Laval nozzle with a speed of 150 m/s, temperature 350 oK. what is the required diameter of the throat to have sonic flow? What would be the velocity and temperature at the exit with a diameter of 75 mm?

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Ans. A= 0.04 m, T= 139.4 K and V=667.5 m/s

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Extra Q. (Part A) Good Luck with your exam!

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L V2 h  f L V P  m gh p L D 2g D 2g p1 V1 2 p2 V 2  z   hp   z  2 2  hLtot  hT g 1 1 2 g g 2 2g hL  f

Water (20C) discharges through a turbine at 1.5 m3/s after passing through a 400 m pipeline (inside diameter 0.9 m, equivalent sand grain roughness ks = 0.45 mm). Assuming the turbine has an efficiency of 65%, determine the power output from the turbine.

exit diameter 2.0 m

(inlet: K = 0.5)

Length: 400 m I.D. 0.9 m

50 m

turbine

Q = 1.5 m3/s 29

Extra Q. (Part A) Water flows through the venturi shown in Figure 3 below. Piezometers are attached to the upstream pipe and minimum area section, and the velocity in the upstream pipe is 4.00 m/s. The difference between the two water levels in the peizometers is 50 mm. Determine the velocity in the minimum area section (point. 2). 0.05 m

4.00 m/s

1

2

Figure 5

31

30

Ans. 454.7 KW...