Fluid Mechanics – Concept Sheet 2

1. 2-D in-viscid steady flow momentum equation dP/ρ+g.dz+v.dv=0 a. Bernoulli b. Euler equation
2. Ideal, steady, continuous, incompressible, in-viscid, ir-rotational , along stream line
a. Bernoulli equation b. Pascal’s law
3. Pressure head {P/(ρg)} + gravitational head (z) + velocity head{V2/(2g)} is a. constant b. varying
4. For venturimeter diameter of throat is 33 to _ % of inlet diameter a. 40 b. 50
5. Angle of divergence in venturimeter to avoid flow separation in degrees a. 6-7 b. 8-9
6. Venturimeter ideal discharge is A1A2.x/√(A12-A22); x= a. √(gh) b. √(2gh)
7. Head h=x(Sm-S)/S if ‘x’ is manometric deflection then
a. Sm is relative density of manometric fluid b. S is relative density of flowing fluid c. both
8. For venturimeter coefficient of discharge is a. 0.46-0.76 b. 0.94-0.98
9. For venturimeter coefficient of discharge is √(h-hl)/√h a. correct b. not correct
10. For orifice meter coefficient of discharge is a. 0.64-0.76 b. 0.94-0.98
11. Kinetic energy is converted into pressure energy using a. flagrant tube b. pitot tube
12. Velocity using pitot tube is a. √(2.∆P/ρ) b. √(∆P/ρ)
13. Contraction coefficient is Ratio of areas a. vena contracta to orifice b. orifice to vena contracta
14. Coefficient of velocity is ratio of _ velocities a. theoretical to actual b. actual to theoritical
15. Coefficient of discharge is ratio of _ discharges a. theoretical to actual b. actual to theoritical
16. For orifice meter Cd= a. Cc.Cv b. Cc/Cv
17. Venturimeter, flow nozzle,orifice meter,bend meter,rotameter measures a. rate of flow b. pressure
18. Pitot tube measures a. pressure b. velocity
19. Velocity in open channels is measured by a. voltage meter b. current meter
20. Hot wire anemometer measure _ velocity a. air b. gas c. both
21. Reynolds number is a. ρdv/µ b. µ/ ρdv
22. In pipe flow, transition flow a. 2000-4000 b. 5000-7000
23. In open channel flow, transition flow a. 1000-4000 b. 500-1000
24. Entrance length required to establish fully developed laminar flow (Le/D) a. 0.07Re b. 0.05Re
25. Entrance length required to establish fully developed turbulent flow (Le/D) a. 50 b. 70
26. Shear stress in circular pipe is τ= a. (∂P/∂x)*(-r/2) b. (∂P/∂x)*(r)
27. Maximum shear stress occurs at radius equals to a. Radius of pipe b. Half of Radius of pipe
28. In laminar flow shear stress is entirely due to _ action a. inertial b. viscous
29. Velocity distribution in a circular pipe (r is distance from axis) U= (0.25/µ) (-∂P/∂x)*_? a. R2-r2 b. r2-R2
30. Velocity in general is Umax*(1-r2/R2) a. yes b. no
31. Velocity profile is a. linear b. parabolic
32. Hagen-Poiseulle equn. for viscous flow discharge (Q) a. {π/(64µ)} (∂P/∂x)D4 b. {π/(128µ)} (∂P/∂x)D4
33. Point where local velocity is equal to mean velocity r=R/x; what is x? a. 0.707 b.0.577
34. Pressure drop in a pipe is xµVL/D2; what is x? a. 16 b.32 c. 64 d. 128
35. Laminar flow between 2 fixed parallel plates (t=thickness) U= (0.5/µ) (-∂P/∂x)*_? a. y2-ty b. ty-y2
36. Maximum velocity occurs at y=_? a. t b. t/2
37. Maximum velocity is _ time’s average velocity? a.2 b. 1.5
38. Discharge per unit width between plates is Q= {1/(12µ)} (-∂P/∂x)*_? A. t2 b. t3
39. Pressure drop between plates is xµVL/t2; what is x? a. 12 b.16 c. 24 d. 32
40. Kinetic energy correction factor α=_? a. (∫u2.dA)/AV2 b. (∫u3.dA)/AV3
41. Momentum correction factor β=_? a. (∫u2.dA)/AV2 b. (∫u3.dA)/AV3
42. For laminar flow α is _ and β is _ ? a. 1.33, 1.2 b. 2, 1.33
43. For turbulent flow α is _ and β is _ ? a. 1.33, 1.2 b. 2, 1.33
44. Darcy Weisbach equation head loss due to friction (hf)= a.fLV2/(gD) b. fLV2/(2gD)
45. For laminar flow friction factor is _/Re? a. 16 b. 32 c. 64
46. For uniform discharge; Head loss (hf) is inversely proportional to a. D2 b. D5
47. For turbulent flow friction factor is _/Re0.25? a. 0.316 b. 0.532 c. 0.664
48. Friction loss in pipe, if end is closed, flow takes place through sides @ regular interval a. h/3 b. h/2
49. Hydraulic mean depth (m) is a. Area/Wetted Perimeter b. Area /Characteristic length
50. Chezy’s formula V=C.√(mi); “i” is hydraulic slope a. (h/L) b. (L/h)
51. Chezy’s constant and friction factor are related as f.C2=_? a. 2g b. 4g c. 8g
52. Losses due to sudden expansion is h=_/2g a. (V1-V2)2 b. (V1+V2)2
53. Sudden expansion optimum ratio: diameters of pipes so that pressure loss is minimum a. 0.707 b. 0.5
54. Losses due to sudden contraction is h=_/2g a. (Vc-V2)2 b. (Vc+V2)2
55. Coefficient of contraction (Cc) a. Vc/V2 b. V2/Vc
56. Losses due to sudden contraction (Cc is not known) is h=_/2g a. 0.5*V22 b. V22
57. Losses at exit of pipe h=_/2g a. 0.5*V2 b. V2
58. Losses at entrance of pipe h=_/2g a. 0.5*V2 b. V2
59. Loss due to gradual expansion if kL depends on angle of expansion a. kL(V1-V2)2/2g b. a. kL(V1+V2)2/2g
60. Loss factor due to 90 and 45 degrees bend a. 1.2, 0.4 b. 0.4, 1.2
61. Hydraulic Gradient Line (HGL) joins _ points (piezometric) a. P/(ρg)+z b. P/(ρg)+z+( V2/2g)
62. HGL is always _ to TGL and lower than TGL a. perpendicular b. parallel
63. Power transmission through pipe (H is total Head); efficiency a. (H-hl)/H b. hl/H
64. When hl=H/3 ; Power transmission is a. minimum b. maximum
65. Gradual closure of valve, sudden closure of valve&pipe (rigid/elastic), a.water hammer b.cavitation
66. Valve closure is gradual if time t> _? a. L/C b. 2L/C ( Velocity of pressure wave is ‘C’)
67. Valve closure is sudden if time t< _? a. L/C b. 2L/C
68. Pressure head (gradual closure) is given by a. LV/(gt) b. VC/g
69. Pressure head (sudden closure) is given by a. LV/(gt) b. VC/g
70. Region immediate vicinity of boundary surface in which velocity of flowing fluid increases gradually from
zero at boundary surface to velocity of main stream a. boundary layer b. transfer layer
71. Distance from boundary surface in which velocity reaches 99% of main velocity
a. boundary layer thickness (δ) b. Displacement thickness (δ*)
72. Distance measured normal to boundary by which solid boundary should be displaced in order to
compensate for reduction in mass flow rate due to boundary layer growth
a. boundary layer thickness (δ) b. Displacement thickness (δ*)
73. Displacement thickness (δ*) (Limits are 0 to δ) is a. ∫1-(v/Vo)dy b. ∫(v/Vo){1-(v/Vo)}dy
74. Momentum thickness (θ) (Limits are 0 to δ) is a. ∫1-(v/Vo)dy b. ∫(v/Vo){1-(v/Vo)}dy
75. Energy thickness (δe) (Limits are 0 to δ) is a. ∫1-(v/Vo)dy b. ∫(v/Vo){1-(v/Vo) 2}dy
76. For v/Vo=y/δ; a. δ*> δe> θ b. δ*< δe < θ
77. For v/Vo=y/δ; δ*=δ/2 and θ= δ/6 and δe=δ/4 a. yes b. no
78. Shape factor( always >1) is a. δ*/θ b. θ/ δ*
79. Laminar flow u/u∞ a. (3/2)(y/ δ)-(1/2)( y/ δ)3 b. (y/ δ)0.5
80. Turbulent flow u/u∞ a. (3/2)(y/ δ)-(1/2)( y/ δ)3 b. (y/ δ)0.5
81. Laminar flow implies a. <500000 b. >500000
82. Laminar flow δ/x = a. 5/√Re b. 0.576/(Rex)0.2
83. Turbulent flow δ/x = a. 5/√Re b. 0.576/(Rex)0.2
84. Laminar flow skin friction coefficient is Cfx=2τ/(ρv2) a. 0.664/√Re b. 0.059/(Rex)0.2
85. Turbulent flow skin friction coefficient is a. 0.664/√Re b. 0.059/(Rex)0.2
86. Laminar & turbulent flow drag coefficient Cd=2Fd/(Aρv2) is_&_ times Cfx a. 2,1.25 b. 1.25, 2
87. Flow is attached means at y=0 a. ∂u/∂y<0 b. ∂u/∂y=0 c. ∂u/∂y>0
88. Flow is separated means at y=0 a. ∂u/∂y<0 b. ∂u/∂y=0 c. ∂u/∂y>0
89. Adverse pressure gradient means a. ∂P/∂x>0 b. ∂P/∂x=0 c. ∂P/∂x<0
90. Rotating boundary in direction of flow, Suction of slow moving fluid by a suction slot; Supplying additional
energy from blower; Providing a bypass in slotted wing; Providing guide blades in a bend; Injecting fluid
into boundary layer; Stream lining of body shapes a. Produces Separation b. Prevents Separation