Physics

Fluid Mechanics and Hydraulics

376 Questions

Fluid mechanics and hydraulics questions address the principles of fluid flow, pipe resistance, and open channel dynamics. The topics include Bernoulli equation, Navier-Stokes equation, and hydrograph calculations. These concepts are crucial for civil and mechanical engineering competitive examinations.

Fluid flow equationsOpen channel flowPipe frictionHydraulic jumpHydrograph analysis

Fluid Mechanics and Hydraulics Questions

Multiple choice

An isolated 4-hour storm occurred over a catchment as follows:

Time 1st hour 2nd hour 3rd hour 4th hour
Rainfall (mm) 9 28 12 7

The$\phi$ index for the catchment is 10 mm/h. The estimated runoff depth from the catchment due to the above storm is

  1. 10 mm

  2. 16 mm

  3. 20 mm

  4. 23 mm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total rainfall = 9 + 28 + 12 + 7 = 56 mm. Phi index = 10 mm/h. Runoff occurs when rainfall > phi. Hours 1, 2, 3, 4 have rainfall 9, 28, 12, 7. Rainfall > 10 occurs in hours 2 (28-10=18) and 3 (12-10=2). Total runoff = 18 + 2 = 20 mm.

Multiple choice

A rectangular open channel needs to be designed to carry a flow of 2.0 m3/s under uniform flow conditions. The Manning’s roughness coefficient is 0.018. The channel should be such that the flow depth is equal to half the width and the Froude number is equal to 0.5.

Keeping the width, flow depth and roughness the same, if the bed slope of the above channel is doubled, the average, boundary shear stress under uniform flow conditions is

  1. 5.6 N/m2

  2. 10.8 N/m2

  3. 12.3 N/m2

  4. 17.2 N/m2
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 $\tau = \omega RS_0, \text{Now}, S_0 = 0.0042\\ R = y/2 = \frac{0.836}{2} = 0.418 \\ \therefore \tau = 9810 \times 0.418 /times 0.0042 \\ \hspace{0.8cm} = 17.22 N/m^2$

Multiple choice

A plain sedimentation tank with a length of 20 m, width of 10 m and a depth of 3 m is used in a water treatment plant to treat 4 million litres of water per day (4 MLD). The average temperature of water is 20°C. The dynamic viscosity of water is 1.002 x 10–3 N.s/m2 at 20°C. Density of water is 998.2 kg/M3. Average specific gravity of particles is 2.65.

What is the surface overflow rate in the sedimentation tank?

  1. 20 m3/ m2/ day

  2. 40 m3/ m2/ day

  3. 67 m3/ m2/ day

  4. 133 m3/ m2/ day
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

 $\text{Surface overflow rate} = \frac{Q}{Area of the tank}\\ = \frac{4 \times 10^6 \times 10^{-3}}{20 \times 10}m^3/day = 20 m^3 / m^2 / day$

Multiple choice

A plain sedimentation tank with a length of 20 m, width of 10 m and a depth of 3 m is used in a water treatment plant to treat 4 million litres of water per day (4 MLD). The average temperature of water is 20°C. The dynamic viscosity of water is 1.002 x 10–3 N.s/m2 at 20° C. Density of water is 998.2 kg/M3. Average specific gravity of particles is 2.65.

What is the minimum diameter of the particle which can be removed with 100% efficiency in the above sedimentation tank?

  1. 11.8 x 10–3 mm

  2. 16.0 x 10–3 mm

  3. 50 x 10–3 mm

  4. 58 x 10–3 mm
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation