Laminar Flow vs Turbulent Flow (module 5)

Question 1

What is a boundary layer?

Answer 1

-The side of the vent where the velocity rises from zero to its free stream value

-viscous effects dominate & fluid exerts drag on the surface

Question 2

What is the formula for Reynolds number? (RE)

Answer 2

Re = inertial forces / viscous forces

Question 3

What is large Re & what does it mean?

Answer 3

Re> 4000 turbulent flow

Question 4

What is a small Re & what does it mean?

Answer 4

Re< 2000 Laminar flow

Question 5

What is the importance or Re?

Answer 5

• characterizes the nature of the flow

Question 6

What is a laminar flow?

Answer 6

• refers to the parallel streamlines that gas molecules are observed to follow at low velocities
• smooth flow no disturbances
  -no lateral or radial mixing of the fluid in a laminar flow

Question 7

What is a turbulent flow?

Answer 7

• At higher velocities, the streamlines disappear altogether and the flow
  becomes turbulent
• The flow is chaotic and considerable cross-current mixing occurs

Question 8

Does turbulent or laminar flow have high energy loss?

Answer 8

Turbulent

Question 9

What is flow separation?

Answer 9

• Occurs in a boundary layer as a result of viscous losses which cause the velocity in the layer close to the surface to come prematurely to rest
• flow reversal occurs (wakes & eddies) & turbulence as a result