Fluid Mechanics and Hydraulic Machines

What is an ideal fluid?

An ideal fluid is a fluid assumed to be incompressible and non-viscous with an infinite bulk modulus.

Define specific weight (w).

Specific weight is defined as the weight of a unit volume of a fluid, calculated as w = P * g.

What is specific gravity?

Specific gravity (s) is the ratio of the density of a fluid to the density of a standard fluid.

What is the specific weight of water in N/m³?

The specific weight of water is 9810 N/m³.

What are the types of fluids categorized by viscosity?

Fluids can be categorized as Newtonian and Non-Newtonian fluids.

What is dynamic viscosity (μ)?

Dynamic viscosity is a measure of a fluid's resistance to shear stress and is defined as shear stress divided by shear rate.

What is kinematic viscosity (ν)?

Kinematic viscosity is the dynamic viscosity divided by the fluid density.

How does the viscosity of liquids change with temperature?

The viscosity of liquids generally decreases with an increase in temperature.

What is the unit of dynamic viscosity in SI?

The SI unit of dynamic viscosity is Pascal-second (Pa·s).

Define shear stress in terms of viscosity.

Shear stress (τ) is equal to the product of dynamic viscosity (μ) and the velocity gradient.

What is a Bingham plastic fluid?

A Bingham plastic fluid behaves as a solid until a certain yield stress is exceeded, after which it flows.

What does the term thixotropic mean?

Thixotropic fluids become less viscous when subjected to shear stress over time.

What is surface tension?

Surface tension is the property of a liquid that causes its surface to contract and behave like a stretched elastic membrane.

How does surface tension vary with temperature?

Surface tension decreases as the temperature increases.

What is the compressibility (B) of a fluid?

Compressibility is the measure of the change in volume of a fluid with a change in pressure.

What is Pascal's Law?

Pascal's Law states that in a stationary fluid, the pressure at any point is the same in all directions.

What is hydrostatic pressure?

Hydrostatic pressure is the pressure exerted by a fluid at rest due to the weight of the fluid above it.

Define buoyancy.

Buoyancy is the upward force exerted by a fluid on an object placed in it, equal to the weight of the fluid displaced by the object.

What is Archimedes' Principle?

Archimedes' Principle states that a body submerged in a fluid is buoyed up by a force equal to the weight of the fluid it displaces.

What type of flow is characterized by smooth, orderly layers?

Laminar flow is characterized by smooth, orderly layers.

What type of flow is characterized by chaotic and irregular fluid motion?

Turbulent flow is characterized by chaotic and irregular motion.

Define turbulence intensity.

Turbulence intensity is a measure of the fluctuation of velocity in a turbulent flow compared to the mean velocity.

What is a streamline?

A streamline is a line that is tangent to the velocity vector of the flow, representing the direction of flow at a particular point.

What is a pathline?

A pathline is the trajectory traced by an individual fluid particle over time.

What is a streakline?

A streakline is the line formed by connecting all the fluid particles that have passed a specific point in the past.

What is continuity equation for incompressible fluid?

The continuity equation for incompressible fluid states that A1V1 = A2V2, where A is the cross-sectional area and V is the flow velocity.

Define Reynolds Number.

Reynolds number (Re) is a dimensionless number used to characterize the flow regime, given by Re = (ρVD)/μ.

What happens to flow characteristics at a Reynolds number less than 2000?

Below a Reynolds number of 2000, flow is typically laminar.

How do hydraulic machines convert energy?

Hydraulic machines convert hydraulic energy into mechanical energy or vice versa.

What is the function of a draft tube in a hydraulic turbine?

The draft tube converts kinetic energy at the turbine outlet into pressure energy.

What is the difference between impulse and reaction turbines?

Impulse turbines use only kinetic energy at the inlet, while reaction turbines utilize both kinetic and pressure energy.

Define hydraulic efficiency of a turbine.

Hydraulic efficiency is the ratio of hydraulic power output to the power supplied to the turbine.

What is the function of the impeller in a centrifugal pump?

The impeller in a centrifugal pump imparts velocity to the fluid, increasing its pressure as it moves outward.

What is cavitation in pumps?

Cavitation is the formation of vapor bubbles in a fluid due to low pressure, which can cause damage when the bubbles collapse.

Define specific speed of a pump.

Specific speed is a dimensionless parameter that characterizes the geometry of a pump at a specific flow rate and head.

What does the term NPSH stand for?

NPSH stands for Net Positive Suction Head and is a measure of the pressure available to prevent cavitation in a pump.

What is the purpose of a suction pipe in a pump?

The suction pipe directs fluid to the pump, and it must be designed to maintain sufficient pressure at the pump inlet.

What is a manometer?

A manometer is a device used to measure fluid pressure by balancing it against a column of liquid.

What causes pressure loss in pipe flow?

Pressure loss in pipe flow can be caused by friction, bends, fittings, and changes in diameter.

What is a Venturi meter?

A Venturi meter is a device used to measure the flow