Part 2: Some Classical Concepts and Equations in Fluid Mechanics

Question 1

True or False: Differential analysis can yield results for a few points in the flow field

Answer 1

False, differential analysis can yield results for ANY point in the flow field. This is why it is favoured over Control Volume Analysis that can only yield “global results”

Question 2

What are the different types of fluid motion?

Answer 2

Transition ( no velocity gradient present), linear deformation, rotation , angular deformation

Question 3

What is rotation?

Answer 3

the average angular velocity of two mutually perpendicular lines about a point

Question 4

The existence of a streamline implies that continuity is ____________

Answer 4

Satisfied

Question 5

True or False: Flow can occur across a streamline

Answer 5

False

Question 6

The existence of a valid potential function, (Phi), means that the flow is ___________

Answer 6

Irrotational

Question 7

Streamlines and Equipotential lines are _________ to each other

Answer 7

orthogonal

Question 8

True or False: The velocity of flow is always perpendicular to the equipotential line

Answer 8

True

Question 9

True or False: The velocity is always perpendicular any streamline

Answer 9

False, Velocity is parallel to the streamline

Question 10

What is a Flow Net?

Answer 10

A flow net is a family of streamlines and equipotential lines drawn throughout a flow field.

Question 11

Where is the pressure lowest on a flow net?

Answer 11

The pressure is lowest where the equipotential lines are the closest. This is also where the highest velocity is.

Question 12

The difference between the water level upstream and the water level down stream is called _________

Answer 12

The Driving Head

Question 13

True or False: A free vortex is irrotational

Answer 13

True

Question 14

True or False: In a Forced vortex the highest velocity is on the outer edge.

Answer 14

True

Question 15

What are the four Bernouilli assumptions?

Answer 15

• Inviscid fluid
• Steady Flow
• Incompressible Flow
• Flow is along a Streamline

Question 16

In general, Potential Flow theory gives reasonable solutions to real fluid flow problems when:

Answer 16

1) the fluid is of low viscosity
2) The velocity is relatively high
3) The fluid is accelerating

Question 17

True or False: For an inviscid flow there will be Shear stresses.

Answer 17

False, For inviscid flow there will be NO shear stress. There will however be normal stress due from pressure

Question 18

The Naiver-Stokes equations are the basic differential equations describing _________

Answer 18

The flow of incompressible Newtonian Flow

Question 19

True or False: Navier-Stokes law apply to both Laminar and Turbulent Flow

Answer 19

True

Question 20

What is Plane Poiseuille Flow?

Answer 20

Poiseuille Flow is a steady, laminar flow between infinite horizontal, fixed, parallel plates. Flow occurs in the x-direction only. Maximum Velocity will occur at the centre between the points.

Question 21

What is Couette Flow?

Answer 21

Couette flow is a steady, laminar flow between infinite horizontal, parallel plates. With flow occurring in the x-direction only and one plate moving.

Question 22

What is Hagen-Poiseuille Flow?

Answer 22

Hagen Poiseuille Flow is a steady, laminar flow in a straight, horizontal, circular tubes of constant size.