CBE 30355 - Lecture Notes - Aug. 27, 2024

Announcements

Class notes

• What are Fluid Mechanics?
• What is a fluid?

Goals:

• Identify properties of fluids.
• Know how to classify simple fluid mechanics problems.

Reading

• The class notes.
• BS&L, chapter 1

Additional Readings:

In class today we discussed fluid properties such as viscosity and density. It's a good idea to have a 'gut' knowledge of the magnitude of these quantities so you have a better chance of knowing when your calculations are off - a sort of "Wait a minute, that doesn't make any sense" ability. For a classic example of what can happen if you - don't - I offer you the Gimli Glider, described here.

Demonstration:

In class today we start things off with a "bang" - the ever popular can crushing! This demonstration shows just how large air pressure is, and is particularly topical with the recent collapse of the Titan submersible. There are actually a number of interesting transport problems associated with this demo that we will look at: the effect of the size of the opening and the dynamic pressure associated with the water rushing in to replace the condensed water vapor, the heat transfer coefficient necessary for rapid condensation, and verification that it is actually the spray of the water -into- the can which is necessary to get the "bang". A nice high speed video of the process is found at:

https://www.youtube.com/watch?v=mS8ZIrDetJM

Looking at the video frame by frame, the initial deformation takes about 25ms from first contact with the water, and then complete collapse occurs in only another 10ms!