Cheg 355 - Lecture Notes - Nov. 9, 2006

Announcements

Class notes

The main points of the lecture were

• Boundary Layer Flows

Goals:

• Scale the transport equations to determine the length scale appropriate in a boundary layer, and develop the Prandtl boundary layer equations.

Reading

• The class notes.
• BS&L, chapter 4
• Multi-Media Fluid Mechanics: Work through Boundary Layers: Boundary Layer Concepts.

Additional Readings:

Boundary layer flows lead to fascinating phenomena. One key problem in flow past a bluff body at high Re is boundary layer separation, and the transient wakes which form behind the body. These vortices often become detatched from the object leading to what is called a von Karman Vortex Street. As the eddies are shed from alternate sides of the body, there are often large lateral forces exerted on the body. If the frequency of the Karman eddy shedding matches a resonant vibrational frequency of the object - watch out! To see a brief discussion (and a little movie) of the vortex shedding process, go here. To see a classic example of what happens when the frequency hits resonance, check out one of many websites on the Tacoma Narrows bridge disaster. One good one may be found here.

Demonstration: