What does compressible flow look like in a duct undergoing heating/cooling?

In summary, compressible flow in a duct undergoing heating or cooling involves changes in fluid density and velocity as temperature variations affect pressure and flow characteristics. When heated, the fluid expands, leading to reduced density and increased velocity, while cooling causes contraction and increased density, which can result in different flow regimes. The behavior is governed by thermodynamic principles and can lead to phenomena such as shock waves or flow separation, depending on the duct design and operating conditions. Understanding these effects is crucial for efficient thermal management in engineering applications.
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s34n
3
0
Been trying to find out what compressible flows would look like, to picture why you get the not so intuitive property changes.

Started with looking into what might be happening in Rayleigh flow. Theres plently of examples on how to use maths to calculate property changes when going from inlet to outlet of a duct, but I've not been able to find anything that gives a visual picture of what is happening with the flow within the duct and at the heating/cooling point.

My reference material has been this book link to pdf copy of Fluid Mechanics: Fundamentals & Applications (link to copyright book removed by moderator) , Rayleigh flow starting at page 693 of the book (718 of the PDF).
And the table for Rayleigh flow property changes, Table 12-3 on page 696 (721 of pdf).

Should I be thinking of the heating/cooling causing a creation of an artifical nozzel out of the affected fluid at the wall of the duct?

Is the heating/cooling of the fluid meant to be equal across the cross section of the duct at the one point?

Cheers
 
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  • #2
Thread is in Moderation for Mentor review...
 
  • #3
After deleting a link to a PDF textbook copy of questionable origin, this thread is re-opened.
 
  • #4
If anyone has any suggestions on where to look or who/where to ask about visualising compressible flows, that would be welcomed as well.

Cheers
 
  • #6
Thanks onatirec.

Interesting video. Its those sorts of images and ideas that make me think maybe theres a nozzel being created out of the affected fluid, but thats just my crazy thoughts at the moment.

Cheers
 

FAQ: What does compressible flow look like in a duct undergoing heating/cooling?

How does heating affect compressible flow in a duct?

Heating a compressible flow in a duct increases the temperature of the gas, which in turn increases its velocity if the flow is subsonic. This is due to the fact that the speed of sound in the gas increases with temperature, leading to an increase in the Mach number. If the flow is supersonic, heating can cause the flow to decelerate.

How does cooling affect compressible flow in a duct?

Cooling a compressible flow in a duct decreases the temperature of the gas, which reduces its velocity if the flow is subsonic. This is because the speed of sound in the gas decreases with temperature, leading to a decrease in the Mach number. If the flow is supersonic, cooling can cause the flow to accelerate.

What is the effect of heating on the pressure and density of the flow?

Heating a compressible flow in a duct generally causes the pressure to increase and the density to decrease. The increase in temperature causes the gas molecules to move more rapidly, exerting greater pressure on the duct walls. The density decreases because the gas expands as it is heated.

What is the effect of cooling on the pressure and density of the flow?

Cooling a compressible flow in a duct generally causes the pressure to decrease and the density to increase. The decrease in temperature reduces the kinetic energy of the gas molecules, resulting in lower pressure. The density increases because the gas contracts as it is cooled.

How does the Mach number change with heating and cooling in a duct?

When a compressible flow in a duct is heated, the Mach number increases if the flow is subsonic and decreases if the flow is supersonic. Conversely, when the flow is cooled, the Mach number decreases if the flow is subsonic and increases if the flow is supersonic. This behavior is due to the changes in the speed of sound and gas velocity with temperature.

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