Fluid Mechanics Overview

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Questions and Answers

What characterizes an ideal fluid?

It always offers shear resistance.

It flows steadily and without friction. (correct)

It exists in practical applications.

It has viscosity and is compressible.

How is steady flow defined?

The pressure is inconsistent throughout the fluid.

The characteristics at a point do not change with time. (correct)

The velocity changes constantly with time.

The flow depth varies with distance.

Which of the following is a property of real fluids?

They possess viscosity. (correct)

They do not change their velocity over time.

They have no shear resistance.

They flow uniformly in all situations.

What distinguishes non-uniform flow from uniform flow?

Velocity varies at different points in the fluid. Signup and view all the answers

During laminar flow in circular pipes, how is the velocity distribution characterized?

It follows a three-dimensional paraboloid of revolution. Signup and view all the answers

What happens as the critical velocity is exceeded in a flowing fluid?

Turbulence increases with the velocity of flow. Signup and view all the answers

What characterizes turbulent flow?

Particles follow irregular, crossing paths. Signup and view all the answers

Which statement is true regarding uniform fluid flow?

Velocity at a given instant is the same at all points. Signup and view all the answers

What is the primary property of a streamline in fluid dynamics?

The velocity vector at every point is tangent to the streamline. Signup and view all the answers

Which of the following best defines a stream tube?

A closed curve that does not permit fluid to pass through its walls. Signup and view all the answers

How is the mass flow rate (M) expressed?

As the mass density multiplied by volume flow rate. Signup and view all the answers

Which law states that mass cannot be created or destroyed in a closed system?

Law of Conservation of Mass Signup and view all the answers

What does the continuity equation represent for incompressible fluids?

It states that the flow rate remains constant throughout the fluid system. Signup and view all the answers

The First Law of Thermodynamics is primarily concerned with what aspect?

The transformation of energy from one form to another. Signup and view all the answers

In the equation for volume flow rate, what does 'Q' represent?

Volume flow rate in m³/s Signup and view all the answers

Which relationship best describes the flow of fluid in a pipe according to the principle of mass conservation?

The amount of fluid entering a pipe must equal the amount leaving. Signup and view all the answers

What characterizes compressible fluid flow?

The fluid density remains constant throughout the flow. Signup and view all the answers

In what type of fluid flow do particles rotate about their own axes during movement?

Rotational fluid flow Signup and view all the answers

Which equation correctly represents one-dimensional flow?

u = f(x), v = 0, w = 0 Signup and view all the answers

What distinguishes a two-dimensional fluid flow from a one-dimensional flow?

Velocity depends on two spatial coordinates. Signup and view all the answers

What is a path line in fluid flow?

A line made by a single particle as it moves over time. Signup and view all the answers

How is an irrotational fluid flow defined?

Particles do not rotate about their axes while flowing. Signup and view all the answers

Which characteristic best describes a three-dimensional flow?

Velocity depends on time and three spatial coordinates. Signup and view all the answers

What is the purpose of a streak line in fluid dynamics?

To show the line occupied by particles from specific origins at a given moment. Signup and view all the answers

What happens to the potential energy of a fluid as it flows from a higher elevation to a lower one?

It decreases while kinetic energy increases. Signup and view all the answers

Newton's Second Law is described as which of the following?

The resultant force acting on a system equals the rate at which the momentum of the system is changing. Signup and view all the answers

Which of the following best describes a continuity equation in physics?

It describes the transport of a conserved quantity. Signup and view all the answers

What unit is used to express kinetic energy in the SI system?

Newton-meter (N-m) or Joule (J) Signup and view all the answers

What is the formula for calculating potential energy based on mass and height above a datum plane?

Potential Energy = Wz Signup and view all the answers

How is kinetic energy per unit weight defined?

Kinetic Energy Weight = v^2/2g Signup and view all the answers

What term is used for potential energy per unit weight?

Elevation head Signup and view all the answers

In fluid dynamics, which energy conversion takes place as a fluid descends?

Potential energy is converted to kinetic energy. Signup and view all the answers

Study Notes

Ideal and Real Fluids

Ideal fluids are theoretical constructs that lack viscosity and are incompressible.
Real fluids possess viscosity, which is the resistance to flow.
Density, viscosity, and surface tension are crucial properties of real fluids.

Types of Fluid Flow

Steady flow: Velocity, pressure, and other characteristics remain constant over time at a specific point.
Unsteady flow: Velocity and other characteristics change with time at a specific point.
Uniform flow: Velocity is the same at all points in the fluid at a given instant.
Non-uniform flow: Velocity varies at different points in the fluid at a given time.
Laminar flow: Individual particles follow well-defined paths without crossing or intersecting.
Turbulent flow: Particles follow irregular paths that cross and re-cross each other.
Compressible flow: Density remains relatively constant as the fluid moves.
Incompressible flow: Density varies due to pressure changes.
Rotational flow: Fluid particles rotate about their axis while flowing along a streamline.
Irrotational flow: Fluid particles do not rotate about their axis while flowing along a streamline.
One-dimensional flow: Velocity is a function of time and one space coordinate. Occurs in long, straight pipes or between parallel plates.
Two-dimensional flow: Velocity is a function of time and two space coordinates. Occurs in plane flows.
Three-dimensional flow: Velocity is a function of time and three space coordinates.

Fluid Flow Illustrations

Path lines: Tracks the path of a single particle over time.
Streak lines: Shows the instantaneous positions of all particles originating from a specific point.
Streamlines: Lines tangent to the velocity vector at every point, representing the instantaneous velocity direction of the fluid.
Stream tube: A tube formed by streamlines, across which no fluid can pass.

Fluid Flow Equations

Discharge or flow rate (Q): Amount of fluid passing through a section per unit time.
- Volume flow rate (Q) = Av
- Mass flow rate (M) = ρQ
- Weight flow rate (W) = γQ
- A: cross-sectional area
- v: mean velocity
- ρ: mass density
- γ: weight density

Basic Laws of Fluid Flow

Conservation of mass: States that mass can only be transformed, not created or destroyed.
- In fluid flow, the amount of fluid entering a system equals the amount leaving, assuming no leaks or accumulation.
- Represented by the continuity equation: 𝐴1𝑣1 = 𝐴2𝑣2
First law of thermodynamics: States that energy can be transformed but not created or destroyed.
- Energy in fluid flow exists in kinetic, potential, and internal forms.
- Total energy remains constant but can convert between forms.
Newton's second law: States that the resultant force acting on a system equals the rate of change of its momentum.

Energy and Heads of Fluids in Motion

Energy: Ability to do work. In fluids, it exists as kinetic, potential, and pressure energies.
Kinetic energy: Energy possessed by a mass due to its motion.
Velocity head: Kinetic energy per unit weight (𝑣𝟐 𝟐𝒈)
Potential energy: Energy possessed by a mass due to its position.
Elevation head: Potential energy per unit weight (z)
Pressure energy: Energy possessed by a fluid due to its pressure.
Pressure head: Pressure energy per unit weight (P/γ)

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Description

Explore the concepts of ideal and real fluids, including their properties like viscosity and density. Understand the various types of fluid flow such as steady, unsteady, laminar, and turbulent flows. This quiz will test your knowledge of fluid dynamics principles.