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



On 2/7/19 2:59 PM, bernard cleyet wrote:

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

There are two ways of writing the equation for throughput
as a function of pressure-drop and viscosity:
-- one in terms of dynamics viscosity;
-- one in terms of kinematic viscosity.

One of them has a factor of density built into the definition
of viscosity; the other has a factor of density in the flow
law.

Or to say the same thing another way, much depends on whether
you care about the /mass/ of fluid throughput, or the /volume/.

Most experts would not talk about "the" viscosity in a situation
like this, where the density is changing.

The flame demo is just for gee whiz. It's not an expert-level
determination of anything. For starters, the "size" of the
flame depends on both the mass of fuel and the velocity with
which it emerges.