Fluid mechanics is the branch of physics that studies the behavior of fluids (liquids, gases, and plasmas) and the forces acting on them.
Differentiate between a real fluid and an ideal fluid.
An ideal fluid is one that is non-viscous and incompressible, whereas a real fluid has viscosity and is compressible.
Define viscosity.
Viscosity is the measure of a fluid’s resistance to deformation or flow. It is a property that determines how easily a fluid can flow.
Explain Pascal’s law.
Pascal’s law states that any change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid and to the walls of its container.
What is the difference between steady and unsteady flow?
In steady flow, the velocity of the fluid particles at any point remains constant with time, while in unsteady flow, the velocity changes with time.
Fluid Statics:
State Archimedes’ principle.
Archimedes’ principle states that an object submerged in a fluid is buoyed up by a force equal to the weight of the fluid it displaces.
Define buoyancy.
Buoyancy is the upward force exerted by a fluid that opposes the weight of an immersed or submerged object.
Explain the concept of center of buoyancy.
The center of buoyancy is the centroid of the displaced volume of fluid when an object is immersed in a fluid. It is the center of gravity of the fluid displaced.
Fluid Dynamics:
What is Bernoulli’s equation?
Bernoulli’s equation describes the conservation of energy in a fluid flow and relates pressure, velocity, and elevation at any two points in a steady flow.
Define streamline and pathline.
A streamline is an imaginary line that represents the path of a fluid particle in steady flow. A pathline traces the actual path followed by a particular fluid particle in unsteady flow.
Explain the significance of Reynolds number.
Reynolds number is a dimensionless quantity used to predict the flow patterns in different fluid flow situations. It is essential for determining whether a flow is laminar or turbulent.
Fluid Kinematics:
What is the difference between Eulerian and Lagrangian approaches in fluid mechanics?
In the Eulerian approach, properties are observed at fixed points in space, while in the Lagrangian approach, properties are tracked as they move with the fluid particles.
Define velocity and acceleration in fluid mechanics.
Velocity is the rate of change of position of a fluid particle with respect to time. Acceleration is the rate of change of velocity.
Explain the concept of streamline, streakline, and pathline.
A streamline is an imaginary line representing the path of a fluid particle. A streakline is the line composed of all fluid particles that have previously passed through a particular point. A pathline traces the path of a specific fluid particle.
Fluid Flow Measurements:
What is a Pitot tube, and how is it used in fluid mechanics?
A Pitot tube is a device used to measure fluid flow velocity. It works on the principle of converting kinetic energy into potential energy, with the static pressure indicating the fluid velocity.
Explain the working principle of a venturi meter.
A venturi meter measures fluid flow by constriction of the flow path. The pressure difference across the constriction is used to determine the flow rate.
Define flow rate and discharge in fluid mechanics.
Flow rate is the volume of fluid passing through a section per unit time. Discharge is the flow rate multiplied by the cross-sectional area of the flow.
Fluid Forces:
What is the buoyant force, and how is it calculated?
The buoyant force is the upward force exerted on an object submerged in a fluid. It is equal to the weight of the fluid displaced by the object.
Explain the term “drag force.”
Drag force is the resistance force exerted on an object moving through a fluid in the opposite direction to its motion.
Define lift force in fluid mechanics.
Lift force is the upward force generated on an object moving through a fluid, perpendicular to the direction of motion. It is commonly associated with the lift on an airplane wing.
Fluid Pumps and Turbines:
Differentiate between a pump and a turbine.
A pump is a device that transfers fluid from a lower to a higher elevation, while a turbine does the opposite, extracting energy from flowing fluid to perform work.
Explain the working principle of a centrifugal pump.
A centrifugal pump works by converting mechanical energy from a motor into kinetic energy in the liquid, which is then converted into pressure energy as it exits the impeller.
What is the function of a hydraulic turbine?
A hydraulic turbine converts the energy from flowing water or fluid into mechanical energy, which can be used to drive a generator and produce electricity.
Fluid Friction:
Define Darcy-Weisbach equation.
The Darcy-Weisbach equation is used to calculate the head loss (pressure drop) due to fluid friction in a pipe.
What is the Moody chart used for in fluid mechanics?
The Moody chart is used to determine the friction factor (f) in the Darcy-Weisbach equation, which is crucial for calculating pressure drop in pipes.
Applications in Engineering:
How does a hydraulic system work?
A hydraulic system uses a fluid (usually oil) to transmit force within a closed system. It is commonly used in applications like heavy machinery and brakes.
Explain the concept of cavitation in fluid mechanics.
Cavitation occurs when the local pressure in a fluid drops below the vapor pressure, causing the formation and collapse of vapor bubbles. It can lead to damage in pumps and other components.
What is the purpose of a nozzle in fluid mechanics?
A nozzle is used to accelerate the flow of a fluid by increasing its velocity. It is often employed in applications such as rocket engines and fuel injectors.
Environmental Fluid Mechanics:
How does fluid mechanics relate to environmental engineering?
Fluid mechanics is crucial in understanding and analyzing the movement of air and water in environmental systems, such as rivers, lakes, and oceans.
What is the impact of fluid mechanics on water treatment processes?
Fluid mechanics principles are applied to design and optimize processes in water treatment plants, ensuring efficient mixing, separation, and transport of contaminants.
Miscellaneous:
Define capillary action.
Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or against, external forces like gravity.
Explain the concept of kinematic viscosity.
Kinematic viscosity is the ratio of dynamic viscosity to density. It describes a fluid’s resistance to flow under