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

A flood wave with a known inflow hydrograph is routed through a large reservoir. The outflow hydrograph will have

  1. attenuated peak with reduced time-base

  2. attenuated peak with increased time-base

  3. increased peak with increased time-base

  4. increased peak with reduced time-base
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 Main function of any reservoir in the flood routing is to reduce the peak and increase the time base so that there will be less damage on the downstream of flow.

Multiple choice

Water emerges from an ogee spillway with velocity = 13.72 m/s and depth = 0.3 m at its toe. The tail water depth required to form a hydraulic jump at the toe is

  1. 6.48 m

  2. 5.24 m

  3. 3.24 m

  4. 2.24 m
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the hydraulic jump formula: y2 = (-y1 / 2) + sqrt((y1^2 / 4) + (2 * v1^2 * y1 / g)). Given v1 = 13.72, y1 = 0.3, g = 9.81. Froude number Fr = 13.72 / sqrt(9.81 * 0.3) = 13.72 / 1.716 = 7.99. y2 = 0.3/2 * (sqrt(1 + 8 * 7.99^2) - 1) = 0.15 * (sqrt(1 + 510.7) - 1) = 0.15 * (22.6 - 1) = 3.24 m.

Multiple choice

In the inclined manometer shown in the figure below, the reservoir is large. Its surface may be assumed to remain at a fixed elevation. A is connected to a gas pipeline and the deflection noted on the inclined glass tube is 100 mm. Assuming $\theta$= 30o and the manometric fluid as oil with specific gravity of 0.86, the pressure at A is

  1. 43 mm water (vacuum)

  2. 43 mm water

  3. 86 mm water

  4. 100 mm water
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 $\text{height of manometer fluid in the manometer} \\ \hspace{2cm} = 100 \times sin 30^0 = 50 mm\\ \text{as per Pascal's law}\\ P_A = P_B = \rho gh = 0.86 \times 50 \times 1 = 43 mm \hspace{0.2cm}\text{of water}$

Multiple choice

A frictionless fluid of density r flows through a bent pipe as shown below. If A is the cross sectional area and V is the velocity of flow, the forces exerted on segment 1-2 of the pipe in the x and y directions are, respectively
  1. $\rho AV^2; 0$
  2. $rAV^2; \sqrt{2} \rho AV^2$

  3. 0; 0

  4. $0; \frac{1}{\sqrt{2}} \rho AV^2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 Force = Change in momentum per second. but in the present case at section 1 and section 2 there is no change in either direction of velocity, magnitude of velocity and area of cross-section between section 1 and section 2. So $F_x = 0, F_y =0$