Free Fluid Flow Operations MCQs with Answers

• A. Decrease in the viscosities of both liquids & gases
• B. Increase in the viscosities of both liquids & gases
• C. Increase in the viscosity of liquids and decrease in that of gases
• D. Decrease in the viscosity of liquids and increase in that of gases

Explanation: Heating reduces intermolecular cohesion in liquids, so their viscosity decreases, while it increases molecular momentum transfer in gases…

• A. Horizontal
• B. Vertical
• C. Inclined
• D. Any

Explanation: A Venturimeter can measure flow in horizontal, vertical, or inclined pipes; the elevation difference is included in the Bernoulli equation…

• A. 9,100
• B. 13,000
• C. 7,000
• D. 2,550

Explanation: For a given fluid, Reynolds number is proportional to velocity times pipe diameter: Re₂/Re₁ = 0.70 × 1.30 = 0.91.

• A. Gravity
• B. Elastic
• C. Pressure
• D. Viscous

Explanation: The Euler number compares inertial effects with pressure forces, commonly written as Eu = ΔP/(ρV²) or an equivalent form.

• A. 1 stoke = 1 cm2/sec
• B. 1 N.sec/m2 = 10 paise
• C. 1 m2/sec = 104 stokes
• D. 1 stoke = 1 m2/sec

Explanation: A stoke is 1 cm²/s, whereas 1 m²/s equals 10^4 stokes. Therefore, the statement that 1 stoke equals 1 m²/s is the incorrect conversion…

• A. Isothermal
• B. Adiabatic
• C. Isentropic
• D. Isochoric

Explanation: Gas flowing through a very long uniform pipe has sufficient time and area for heat exchange with the surroundings, so its temperature…

• A. x1.5
• B. x0.8
• C. x-1.5
• D. x-0.8

Explanation: For a turbulent boundary layer on a smooth flat plate with zero pressure gradient, the empirical thickness relation is approximately δ…

• A. Air
• B. Mercury
• C. Water
• D. Alcohol

Explanation: Kinematic viscosity is ν = μ/ρ; in cgs units, it is numerically equal to dynamic viscosity when the density is 1 g/cm³.

• A. Power saving per unit weight of air delivered
• B. Moisture elimination in the inter-stage cooler
• C. Increased volumetric efficiency
• D. All A , B. & C.

Explanation: Intercooling in multistage compression reduces the work required, condenses moisture between stages, and increases volumetric efficiency…

• A. Independent of
• B. Directly proportional to
• C. Inversely proportional to
• D. None of these

Explanation: For a Newtonian fluid, shear stress follows Newton's law of viscosity, τ = μ(du/dy), so it is directly proportional to the velocity…

• A. Viscous force is larger than the inertia force
• B. Inertia force is larger than the surface tension force
• C. Inertia force is larger than the viscous force
• D. Inertia force is larger than the gravitational force

Explanation: Reynolds number is the ratio of inertial force to viscous force. Therefore, when Re exceeds one, inertial effects are greater than viscous…

• A. Same
• B. Slightly less
• C. Much more
• D. Slightly more

Explanation: The feed-water pump must overcome the boiler pressure as well as pressure losses in the feed line and equipment.

• A. Less
• B. More
• C. Same
• D. Either more or less; depends on the climatic conditions

Explanation: At high altitude, atmospheric pressure and air density are lower, so a compressor handles less mass of air for the same displacement and…

• A. Low vapour pressure
• B. High vapour pressure
• C. Corrosive nature
• D. High boiling point

Explanation: Water has a relatively high vapour pressure compared with commonly used heavy manometric liquids such as mercury, increasing the risk of…

• A. High degree of superheat of steam
• B. Vibration of the pipeline
• C. Partial condensation of steam
• D. Its exposure to torrential rain

Explanation: Steam can partially condense in a pipeline and form liquid-water slugs; their sudden acceleration produces water hammer and severe…

• A. Density of the fluid
• B. Diameter of the pipe
• C. Length of the pipe
• D. Velocity of the fluid

Explanation: The laminar-to-turbulent transition is governed by Reynolds number, which contains density, velocity, diameter and viscosity, but not pipe…

• A. Centrifugal
• B. Gear
• C. Reciprocating
• D. Plunger

Explanation: Centrifugal pumps are preferred for sewage because they can handle large continuous flow rates and suspended solids with relatively simple…

• A. Mach
• B. Froude
• C. Reynolds
• D. Weber

Explanation: The Froude number compares inertial forces with gravity forces in open-channel flow.

• A. Hydrostatic force
• B. Gravity force
• C. Viscous force
• D. Surface tension force

Explanation: A fluid at rest cannot sustain a viscous shear force because there is no relative motion between adjacent layers.

• A. 30°
• B. 60°
• C. 90°
• D. 120°

Explanation: The standard optimum included angle for a triangular or V-notch weir is 90°, which provides maximum discharge under the stated…