Fluid Mechanics Important Questions for R20 JNTU Students
Fluid Mechanics is a core mechanical engineering subject that explains how fluids behave under different conditions of pressure, velocity, and temperature.
It’s one of the most application-based subjects under the JNTU R20 B.Tech syllabus, and mastering it helps in understanding pumps, turbines, and hydraulic systems.
This post covers chapter-wise important theory questions, numerical focus areas, and practice problems for effective exam preparation.
Unit 1: Fluid Properties and Pressure Measurement
Key Theory Questions
Define fluid and explain ideal and real fluids with examples.
Explain Newton’s law of viscosity and its importance in engineering.
Define and differentiate between specific weight, specific gravity, and specific volume.
Explain compressibility and bulk modulus of elasticity.
State and explain Pascal’s Law with applications.
What is a manometer? Explain types — simple, differential, and inclined manometers.
Explain the terms surface tension and capillarity with neat diagrams.
Derive the expression for capillary rise or fall.
Define pressure head, total pressure, and hydraulic head.
Explain the relation between absolute pressure, gauge pressure, and vacuum pressure.
Numerical Focus Areas
Manometer readings and pressure conversion.
Capillary rise/fall calculations.
Density and specific gravity problems.
Bulk modulus and compressibility relationships.
Pressure measurement at different depths.
Unit 2: Fluid Statics
Key Theory Questions
Derive the hydrostatic pressure equation for a static fluid column.
Define and derive expressions for total pressure and center of pressure on plane surfaces.
Explain the concept of buoyancy and Archimedes’ principle.
Discuss stability of submerged and floating bodies.
Define metacenter and derive the expression for metacentric height.
Explain the experimental determination of metacentric height.
Describe the working of a hydraulic press and hydraulic lift.
Explain equilibrium of floating bodies and conditions for stability.
Define pressure prism and its applications.
Explain force on curved surfaces with examples.
Numerical Focus Areas
Hydrostatic pressure and center of pressure on submerged gates.
Buoyant force and float stability problems.
Metacentric height calculations.
Forces on curved surfaces (dams, tanks).
Unit 3: Fluid Kinematics
Key Theory Questions
Explain the types of fluid flow — steady, unsteady, uniform, non-uniform, laminar, turbulent.
Define streamlines, pathlines, and streaklines and explain their differences.
Derive the continuity equation for incompressible flow.
Define and explain velocity potential and stream function.
Derive the relation between velocity potential and stream function.
Explain rotational and irrotational flows.
What is a flow net? Explain its applications.
Define circulation and vorticity.
Explain equipotential lines and streamlines intersection.
Numerical Focus Areas
Continuity equation applications for pipelines and nozzles.
Velocity potential and stream function problems.
Flow rate and mass continuity problems.
Velocity and acceleration components in 2D flow fields.
Unit 4: Fluid Dynamics
Key Theory Questions
Derive Euler’s equation of motion from Newton’s second law.
Derive Bernoulli’s equation and list its assumptions and limitations.
Explain the working and derive discharge formula for Venturimeter.
Derive the discharge equation for an orifice meter.
Explain the working principle of a Pitot tube.
Discuss the momentum equation and its engineering applications.
Define coefficient of discharge (Cd), coefficient of velocity (Cv), and coefficient of contraction (Cc).
Explain the impact of jet on stationary and moving vanes.
Derive the expression for force exerted by a jet on a plate.
Discuss applications of Bernoulli’s theorem in real systems.
Numerical Focus Areas
Bernoulli’s equation applications for nozzles and pipes.
Venturimeter and Orifice meter discharge calculations.
Velocity measurement using Pitot tube.
Impact of jet on stationary/moving vanes.
Momentum and energy equations in fluid flow.
Unit 5: Flow Through Pipes
Key Theory Questions
Define laminar and turbulent flow with examples.
Explain Reynolds experiment and derive the Reynolds number formula.
Derive Hagen–Poiseuille’s equation for laminar flow in a circular pipe.
Explain Darcy–Weisbach equation for head loss due to friction.
Discuss major and minor losses in pipe flow.
Derive expressions for loss of head due to sudden enlargement and contraction.
Define equivalent pipe and compound pipe systems.
Explain hydraulic gradient line (HGL) and total energy line (TEL).
Discuss power transmission through pipes and derive its efficiency.
What is water hammer? Explain its causes and preventive measures.
Numerical Focus Areas
Head loss due to friction (Darcy–Weisbach).
Minor losses (bend, expansion, contraction, valve).
Reynolds number and flow type determination.
Energy loss and power transmission efficiency in pipes.
Series and parallel pipe systems calculations.
Numerical Practice Questions
A U-tube manometer is connected between two pipes carrying water. If the difference of mercury levels is 250 mm, find the pressure difference.
Determine the total pressure and center of pressure on a submerged gate of 3 m height and 2 m width.
Calculate the buoyant force acting on a solid block of 0.05 m³ completely submerged in water.
A pipe of 200 mm diameter reduces to 100 mm diameter. If the velocity in the smaller pipe is 3 m/s, find the velocity in the larger pipe.
A Venturimeter has an inlet diameter of 0.2 m and throat diameter of 0.1 m. The differential manometer shows 150 mm of mercury. Find the discharge.
Calculate jet impact force when a jet of 50 mm diameter strikes a stationary plate normally at 20 m/s.
Water flows through a 100 m long pipe at 0.05 m³/s. Find head loss using Darcy–Weisbach equation if f = 0.02.
Find the Reynolds number for water flowing through a 50 mm pipe at 2.5 m/s and determine the flow regime.
Calculate power transmitted through a pipeline of 150 mm diameter over 500 m length with given head and efficiency.
A hydraulic press has a plunger diameter of 25 mm and ram diameter of 250 mm. Find the mechanical advantage and pressure ratio.
Tips for R20 JNTU Students
Remember key formulas:
Bernoulli’s equation, Continuity equation, Darcy–Weisbach, Hagen–Poiseuille, Reynolds number.
Draw neat, labeled diagrams for manometers, Venturimeter, and orifice meter.
Revise unit conversions and SI units carefully.
Focus on derivations with assumptions and limitations.
Practice university previous papers and model numericals from each unit.
Conclusion
Fluid Mechanics is a high-scoring subject when concepts and formulas are clear.
Understanding fluid behavior helps in analyzing hydraulic systems, turbines, and thermal machinery — crucial for both academic and practical mechanical applications.
By focusing on the key theory questions and numerical problems listed above, R20 JNTU students can prepare confidently for their exams.
