Do Gasses Have Viscosity?

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Discussion Overview

The discussion centers around the concept of viscosity in gases, specifically questioning whether gases possess viscosity similar to liquids and exploring the factors that influence it, such as temperature and pressure. The scope includes theoretical aspects and some practical implications related to the viscosity of air.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that gases do have viscosity, comparing it to liquids.
  • One participant provides a link to a table of viscosities for air, suggesting that air, being a mixture, has specific viscosity values.
  • It is noted that the relationship between temperature and viscosity differs between gases and liquids, with gases exhibiting increased viscosity at higher temperatures.
  • A participant expresses a desire for clarification on the temperature-viscosity relationship in gases, indicating some uncertainty.
  • Another participant mentions Sutherland's formula as a method to calculate gas viscosity based on temperature.
  • There is a suggestion that viscosity may also depend on pressure, indicating a potential complexity in understanding gas viscosity.

Areas of Agreement / Disagreement

Participants generally agree that gases have viscosity, but there are differing views on the factors influencing it, particularly regarding the effects of temperature and pressure. The discussion remains unresolved on some aspects, particularly the nuances of how these factors interact.

Contextual Notes

Some assumptions about the conditions under which viscosity is measured, such as constant pressure, are not fully explored. The relationship between temperature, pressure, and viscosity in gases is acknowledged but not definitively resolved.

TriKri
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Fluids have viscosity, but do gasses have it? And in that case, what is the viscosity for normal air (I know air isn't one gas)?
 
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Like liquid, gas has viscosity of course. But only one thing they are different is for liquid, the higher the temperature, the lower the viscosity and for gas, it's opposite.
 
pixel01 said:
Like liquid, gas has viscosity of course. But only one thing they are different is for liquid, the higher the temperature, the lower the viscosity and for gas, it's opposite.

I don't doubt that you are correct, but could you or someone explain this to me?
 
Archosaur said:
I don't doubt that you are correct, but could you or someone explain this to me?
It is correct. It has to do with momentum transfer between molecules in the gas. Look up Sutherland's formula to see how to calculate a gases viscosity based on temperature.
 
pixel01 said:
Like liquid, gas has viscosity of course. But only one thing they are different is for liquid, the higher the temperature, the lower the viscosity and for gas, it's opposite.

I guess that is under a constant pressure, otherwise the viscosity is dependent on the pressure, isn't it?
 

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