Unit F2

Question 1

What is stream function

Answer 1

It is function of the position x and y, and time ( if the flow is not steady )
Lines of constant ψ are streamlines.
Expressed in m² /s

Question 2

What are the properties of streamlines

Answer 2

Streamlines are lines which re tangent to the velocity field
The mathematical definition of streamline is: dx/u = dy/v
There is no flow across streamlines as they are tangent to the velocity field
The flow rate between two streamlines is constant
If the streamlines are closer together for equal increase to of ψ, the flow velocity is higher
Streamlines cannot intersect except at points where the velocity is zero (if not the flow velocity would have two direction, which is impossible)

Question 3

What are the four distinct components the general motion of a fluid particle can be divided into?

Answer 3

1. Translation
2. Rotation
3. Extensional deformation
4. Shear deformation

Question 4

What happens at point x = y= 0 in streamlines

Answer 4

Lies on streamline = 0 this streamlines defines the boundary of the flow where u= v= 0. Usually, non zero velocities would mean flow in in two directions at once which isn’t possible

Question 5

How do you know if a flow field is one or two dimensional

Answer 5

Two dimensional means the u and y velocity field equations have non zero velocities in x and y

Question 6

What does it mean if the fluid particle trajectory curve and the streamline curve are not the same

Answer 6

Flow is unsteady