Hydrodynamics

Question 1

1. Hydrodynamics deals with fluids that are ___.
   A. At rest B. In motion C. Viscous only D. Incompressible only

Answer 1

✅ Answer: B – In motion
It studies forces and energy of moving fluids.

Question 2

2. The total head in a moving fluid is the sum of ___.
   A. Pressure, velocity, and potential heads B. Only potential head C. Dynamic and static heads D. Height only

Answer 2

✅ Answer: A – Pressure, velocity, and potential heads
H = P/γ + V²/2g + z.

Question 3

3. Bernoulli’s theorem is based on ___.
   A. Conservation of energy B. Conservation of mass C. Momentum principle D. Pascal’s law

Answer 3

✅ Answer: A – Conservation of energy
Applies to steady, incompressible, frictionless flow.

Question 4

4. In Bernoulli’s equation, V²/2g represents ___.
   A. Velocity head B. Pressure head C. Potential head D. Flow head

Answer 4

✅ Answer: A – Velocity head
Energy due to motion.

Question 5

5. The assumption of Bernoulli’s equation excludes ___.
   A. Compressible fluid B. Viscous losses C. Both A & B D. Laminar flow

Answer 5

✅ Answer: C – Both A & B
Ideal fluid assumption only.

Question 6

6. The line joining points of equal total head is called ___.
   A. Energy grade line B. Hydraulic grade line C. Streamline D. Equipotential line

Answer 6

✅ Answer: A – Energy Grade Line (EGL)
Represents total energy per unit weight.

Question 7

7. The line joining points of equal piezometric head is ___.
   A. EGL B. HGL C. Streamline D. Pathline

Answer 7

✅ Answer: B – Hydraulic Grade Line (HGL)
HGL = P/γ + z.

Question 8

8. The vertical distance between EGL and HGL equals ___.
   A. Head loss B. Pressure head C. Velocity head D. Elevation head

Answer 8

✅ Answer: C – Velocity head
Difference = V²/2g.

Question 9

9. The equation of motion for steady flow along a streamline is ___.
   A. Euler’s equation B. Bernoulli’s C. Darcy–Weisbach D. Navier–Stokes

Answer 9

✅ Answer: A – Euler’s equation
Differential form of Bernoulli’s derived from Newton’s law.

Question 10

10. The dynamic pressure is given by ___.
    A. ρgh B. ½ρV² C. ρV² D. γh

Answer 10

✅ Answer: B – ½ρV²
Kinetic energy per unit volume.

Question 11

11. The discharge through a venturimeter is given by Q = ___.
    A. A√(2gh) B. A₁A₂√(2gh)/(A₁²–A₂²)½ C. C_d A₁A₂√[2g(h₁–h₂)/(A₁²–A₂²)] D. None

Answer 11

✅ Answer: C – C_d A₁A₂√[2g(h₁–h₂)/(A₁²–A₂²)]
Combines Bernoulli + continuity.

Question 12

12. The coefficient of discharge (C_d) for a venturimeter typically ranges from ___.
    A. 0.4–0.5 B. 0.6–0.7 C. 0.95–0.99 D. 1.0–1.1

Answer 12

✅ Answer: C – 0.95–0.99
Very efficient flow device.

Question 13

13. Flow measurement using a Pitot tube is based on ___.
    A. Continuity B. Bernoulli’s principle C. Pascal’s law D. Archimedes’ principle

Answer 13

✅ Answer: B – Bernoulli’s principle
Measures stagnation and static pressure difference.

Question 14

14. The theoretical velocity from a Pitot tube is ___.
    A. √(2gh) B. 2gh C. h² D. gh

Answer 14

✅ Answer: A – √(2gh)
From V = √(2gh).

Question 15

15. The discharge through an orifice under constant head is proportional to ___.
    A. H B. √H C. H² D. 1/H

Answer 15

✅ Answer: B – √H
From Torricelli’s theorem.

Question 16

16. The coefficient of discharge for sharp-edged orifice is approximately ___.
    A. 0.5 B. 0.6 C. 0.8 D. 1.0

Answer 16

✅ Answer: B – 0.6
Accounts for contraction and velocity loss.

Question 17

17. A mouthpiece has higher discharge than orifice because ___.
    A. Longer B. Less contraction loss C. Shape difference D. Pressure difference

Answer 17

✅ Answer: B – Less contraction loss
Mouthpiece streamlines expand smoothly.

Question 18

18. The flow through a nozzle is considered efficient when ___.
    A. Losses are high B. Flow separates early C. Discharge is maximum with minimum loss D. No pressure recovery

Answer 18

✅ Answer: C – Discharge maximum with minimum loss
Good nozzle design minimizes energy loss.

Question 19

19. In a siphon, flow continues as long as ___.
    A. Inlet above outlet B. Air enters tube C. Pressure in summit < atmospheric D. Fluid compressible

Answer 19

✅ Answer: C – Pressure in summit < atmospheric
Maintains suction head difference.

Question 20

20. The maximum height to which water can be lifted by siphon is approximately ___.
    A. 5 m B. 8 m C. 10 m D. 12 m

Answer 20

✅ Answer: C – 10 m
Limited by atmospheric pressure (~10.3 m water).

Question 21

21. The loss of head in sudden enlargement is ___.
    A. (V₁–V₂)²/2g B. (V₂–V₁)²/2g C. (V₁+V₂)²/2g D. Negligible

Answer 21

✅ Answer: A – (V₁–V₂)²/2g
Energy loss due to eddy formation.

Question 22

22. The loss of head in sudden contraction is ___.
    A. k(V²/2g) B. (V₁–V₂)/g C. (V₂+V₁)²/2g D. Negligible

Answer 22

✅ Answer: A – k(V²/2g)
k ≈ 0.5 for sharp contraction.

Question 23

23. The discharge over a rectangular weir = ___.
    A. 2/3 C_d b√(2g) h³/² B. C_d b h² C. C_d b h D. 1.33bh²

Answer 23

✅ Answer: A – (2/3)C_d b√(2g) h³/²
Standard rectangular weir equation.

Question 24

24. The discharge over a V-notch (triangular weir) = ___.
    A. 1.84 C_d h³/² tan(θ/2) B. 2.5h² C. h² tanθ D. C_d h²/2

Answer 24

✅ Answer: A – 1.84 C_d h³/² tan(θ/2)
For 90° V-notch, Q = 1.38 h³/² approx.

Question 25

25. The head loss due to friction in pipes can also be expressed as ___. A. h_f = f (L/D) (V²/2g) B. h_f = V²/2g C. h_f = ρV²/2 D. h_f = gV/2

Answer 25

✅ Answer: A – h_f = f (L/D) (V²/2g) Darcy–Weisbach formula for pipe friction.