Types of Flow

CHAPTER 3

TYPES OF FLOW

3.1 FLUID FLOW

3.2 UNIFORM FLOW AND STEADY FLOW

3.3 COMPRESSIBLE AND INCOMPRESSIBLE FLOW

3.4 LAMINAR AND TURBULENT FLOW

3.5 REYNOLDS NUMBER

LEARNING OUTCOMES

At the end of this chapter, student should be able to:

i Define each types of flow including pathline, streamline and

stream tube

ii Discuss the differences / characteristics of steady,

unsteady, uniform, non-uniform, laminar, transitional and

turbulent flow

iii Calculate Reynolds Number

iv Determine the types of flow based on Reynolds Number

#

3.1 FLUIDS IN MOTION

Fluids can move or flow in many ways.

Water may flow smoothly and slowly in a quiet stream

or violently over a waterfall.

The air may form a gentle breeze or a raging tornado.

To deal with such diversity, it helps to identify some of

the basic types of fluid flow.

#

3.1 FLUID FLOW

Pathlines : The path followed by a liquid particle in motion is called a

pathline. Thus, the pathline shows the direction of a particle for a certain

period of time or between two given section.

Pipe

A liquid particle

t1

t0

Path line

#

3.1 FLUID FLOW

Streamlines : The imaginary line drawn in a fluid, in such a way that the

tangent to which at any point gives the direction of motion at the point. Thus,

the stream line shows the direction of motion of a number of particles at the

same time.

– Because the fluid is moving in the same direction as the streamlines, fluid

can not cross a streamline.

– Streamlines can not cross each other. If they were to cross this would

indicate two different velocities at the same point. This is not physically

possible.

– The above point implies that any particles of fluid starting on one

streamline will stay on that same streamline throughout the fluid.

Streamlines around a wing shaped body

#

3.1 FLUID FLOW

When the flow is steady, streamlines are often used to represent

the trajectories of the fluid particles.

A streamline is a line drawn in the fluid such that a tangent to the

streamline at any...