Vorticity and circulation - lecture 4

Question 1

Fluid Decomposition:
Vorticity
Divergence
Deformation

Answer 1

Fluid Decomposition (what is it doing)
Vorticity (rotation)
Divergence (spread)
Deformation (stretch)

Question 2

C [upper case]

Answer 2

Circulation
macroscopic variable
measure of the total rotation around an enclosed area (closed curve c [lower case])of a fluid

Question 3

Vorticity
relative vorticity (ζ)
absolute vorticity

Answer 3

vorticity: circulation per unit area, curl of speed
relative vorticity: vertical component of vorticity
absolute vorticity: ζ + f

Question 4

Jet stream

Answer 4

Usually Westerly and just below the tropopause, a ribbon of strong winds that affect weather systems when it meanders north-south.
Bends cause high pressure and fair weather.
Straighter bits cause acceleration, pressure falls as air rises to fill the depleted air, forming clouds and stronger winds.

Question 5

(anti-)cyclonic shear

Answer 5

cyclonic shear - wind with ζ > 0 result in low pressure system
anticyclonic shear - wind with ζ < 0 result in high pressure system

Question 6

curvature vorticity
shear vorticity

Answer 6

curvature vorticity: created by rotating air
shear vorticity: created by sheared flow, aka one, straight direction, at an angle