Cheg 355 - Lecture Notes - Dec. 2, 2004

Announcements

The homework assigned today should be turned in to Phil on Friday, December 10. Hopefully the TA's will have them graded by the final exam review session.

Class notes

The main points of the lecture were

• Turbulence

Goals:

• Determine the characteristic length scale of the viscous sublayer in turbulent pipe flow.
• Estimate the magnitude of the eddy viscosity.

Reading

• The class notes.
• BS&L, chapter 5
• Multi-Media Fluid Mechanics: Continue working through Boundary Layers: Separation.

Additional Readings:

An interesting example of boundary layer separation, turbulence, and angular momentum is the design of a frisbee. Basically, the angular momentum produced by the spin of the frisbee (and the weighted edges) keeps the frisbee stable (constant orientation) while the aerodynamic lift produced by its motion relative to the air keeps it up. Boundary layer control is important too: The ridges around the edge of the frisbee promote turbulence and delay boundary layer separation, reducing drag. A nice discussion of the various effects is given here.

Demonstration: