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[Phys-L] Gaseous viscosity Was: Re: fluids



This conversation reminds me of a suspect viscosity demonstration, which I’ve demonstrated several times at AAPT section meetings. No one has "called me" on it.


It consists of Cu refrigeration tubing connected to a propane bottle supply. The other end terminates in a tee. The other legs go to two spirals. Same tubing. Initially the flames are the same length. If one heats (propane torch) or cools (solid CO2 in alcohol) one, the flame lengths differ — (“like” 100%) I “like” this demo., because it’s counter intuitive.

Suspect, because not only does the viscosity change correctly as shown by the differing flame lengths, but the density changes. What effect is this??

bc too lazy to look up the viscosity of propane and density change w/ temp and think about it.


On 2019/Feb/07, at 11:21, John Denker via Phys-l <phys-l@mail.phys-l.org> wrote:


Continuity is first cousins to conservation. It's always true.
The full fancy statement of continuity takes density into account, but
for simplicity let's assume constant density. Also let's assume the
stream does not break up into droplets.