CBE 30355 - Lecture Notes - Nov. 9, 2023
Read through pages 258-269 of the notes and view the online narration below. Don't forget to complete the quiz in Canvas!
The main points of the lecture were
After this class you should be able to:
- Scale the transport equations to determine the length scale appropriate in a boundary layer, and develop the Prandtl boundary layer equations.
- The class notes.
- BS&L, chapter 4
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.
To see a little movie of the vortex shedding process, go
here. These lateral
forces due to vortex shedding can interact with resonant frequencies of a structure leading to an effect called aeroelastic flutter. Probably -the- classic example of this is the Tacoma Narrows bridge disaster. A nice
collection of movies of the bridge is given
here. The aeroelastic instability isn't all bad, though - a company in Spain has developed into a new method for harvesting energy from
the wind that they claim is much cheaper than conventional windmills. A description of the device may be found here.