Applying Bernoulli's equation to problems involving a perfect gas

[Hak]

I would like to know the opinions of experienced forum users regarding an issue that seems to happen often in problems: namely, applying Bernoulli's equation to perfect gas. Is it permissible to do so, even if only to find reasonable estimates? Two examples I found out might be:

- The problem of finding the internal pressure trend in a leaky space station.

-Estimating the pressure change due to a train passing through a tunnel.
(I just don't see how this can be done without Bernoulli!).

Then I also read in an old article (which I can't find now) that it is possible to prove that the viscosity of a perfect gas is well defined and depends on the root of the temperature, but I haven't found much on the web. Does anyone have any idea how to do this? Could you give me some help in this regard?

 

[Frabjous]

Then I also read in an old article (which I can't find now) that it is possible to prove that the viscosity of a perfect gas is well defined and depends on the root of the temperature, but I haven't found much on the web. Does anyone have any idea how to do this? Could you give me some help in this regard?

”ideal gas” is used more commonly than “perfect gas” in English. I found several links searching on this.

 

[Chestermiller]

See Chapter 1 of Transport Phenomena by Bird, Stewart, and Lightfoot for answer to your question about viscosity of a gas in the ideal gas limit. This same book also has a section on Bernoulli equation customized to ideal gases.

 

[Hak]

See Chapter 1 of Transport Phenomena by Bird, Stewart, and Lightfoot for answer to your question about viscosity of a gas in the ideal gas limit. This same book also has a section on Bernoulli equation customized to ideal gases.

Thanks.

 

[erobz]

I would like to know the opinions of experienced forum users regarding an issue that seems to happen often in problems: namely, applying Bernoulli's equation to perfect gas. Is it permissible to do so, even if only to find reasonable estimates? Two examples I found out might be:

- The problem of finding the internal pressure trend in a leaky space station.

-Estimating the pressure change due to a train passing through a tunnel.
(I just don't see how this can be done without Bernoulli!).

Then I also read in an old article (which I can't find now) that it is possible to prove that the viscosity of a perfect gas is well defined and depends on the root of the temperature, but I haven't found much on the web. Does anyone have any idea how to do this? Could you give me some help in this regard?

I believe Bernoulli's is ok for low speed gas flows (Mach 0.3 or lower), so long as the flow is steady. High speed flows, unsteady flows, and or both high speed/unsteady would need adjustment.

 

[Hak]

I believe Bernoulli's is ok for low speed gas flows (Mach 0.3 or lower), so long as the flow is steady. High speed flows, unsteady flows, and or both high speed/unsteady would need adjustment.

Thank you.

 

[Hak]

This same book also has a section on Bernoulli equation customized to ideal gases.

Is this section on Chapter 3?

 

[Chestermiller]

Is this section on Chapter 3?

Yes, Eqn. 3.5-12

 

[boneh3ad]

You might also search for "Sutherland's law" for finding the viscosity of gases like air.