Calculating Reynolds Number for Turbulent Gas Flow

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Discussion Overview

The discussion focuses on the applicability of the Reynolds number in calculating turbulent gas flow in circular pipe sections, particularly comparing ideal gases like air to real fluids such as water. Participants explore the nuances of using the Reynolds number for different fluid states and the implications of non-ideal behaviors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • The original poster (OP) questions whether the Reynolds number can be calculated for an ideal gas like air in the same manner as for water.
  • One participant asserts that the Reynolds number can be used for gas flows, providing links for further reading.
  • Another participant notes that while the definition of Reynolds number does not change with fluid state, accurate property values for gases can complicate calculations, especially when considering non-ideal behaviors.
  • A different participant emphasizes that gases and fluids are measured similarly regarding turbulence, but acknowledges the complexities introduced by non-ideal gases.
  • One participant poetically reflects on the visibility of turbulent gas flow compared to water and discusses the concept of Reynolds number as a dimensionless quantity that can model transitions between laminar and turbulent flow.

Areas of Agreement / Disagreement

Participants express varying views on the complexities of applying the Reynolds number to gases versus liquids, with some agreeing on its applicability while others highlight the challenges posed by non-ideal conditions. The discussion remains unresolved regarding the extent to which ideal gas assumptions can be applied in practice.

Contextual Notes

Participants mention the need for accurate property values and corrections for pressure and temperature when dealing with non-ideal gases, indicating limitations in applying the Reynolds number without considering these factors.

Mancunian
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Hello

Im currently looking at turbulent gas flow in circular pipe sections by calculating the Reynolds the number. Does the Reynolds equation hold for say flow of an ideal gas - air as it does for a real fluid say water.

This may sound like a stupid question and I supose I've got my head in a twist between the difference of a real fluid and a ideal gas, but I would like to know if I can calculate the reynolds number for a gas - in the same way I would say water through a pipe.

Any help would be greatly appreciated

A very confused Mancunian
 
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Reynolds number definition does not change due to fluid state that I have ever seen. The trick comes in, when dealing with gases, is getting accurate property values. An ideal gas is pretty easy, but it gets tricky when going away from the ideal model and you have to start correcting for pressure (compressibility) and temperature. At work, our aero guys have proprietary aero-thermo codes specifically for calculating properties that are non ideal in our engine decks.
 
Mancunian said:
Does the Reynolds equation hold for say flow of an ideal gas - air as it does for a real fluid say water.
calculate the reynolds number for a gas - in the same way I would say water through a pipe.
A confused Mancunian
Hello Mancunian
don't be confused, Gases and fluids are measured equally in their way of getting turbulent or remaining laminar... That is hydrodynamics, yet remarcs of non ideal gases (electrically?) or ideal fluids (non -Stokes) remain of consequence.
greetings Janm
 
Hello turbulence freaks
You have to admit that yesterday waterballet is not only a olympic game anymore but entried entertainment. I know you want to hear here about turbulent gas flow, more difficult to see (coloured gasses?) then turbulent water (still remaining best drawing of L. daVinci) yet hanging water bassins brought to the public in Russia as an experiment for multimedia...
I was astounded...
And for calculating reynolds number for gasses: The Reynolds number is a dimensionless number. The way I was tought about that is: you can make a model with the same Reynolds number with very varied number of dimensions but if the Reynolds number is the same you get the transition of laminar to turbulent or the other way around in the same way as a model which uses the whole North Sea saying Norway has won...
Sorry for eventually poetic changes, but I am still impressed of the ESC...
greetings Janm
 

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