Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Wait... what? Air viscosity increases with increasing temperature?

Cycle · 08-21-2015, 02:53 PM

How do we reconcile the following two viewpoints?

Air viscosity increases with increasing temperature:
https://en.wikipedia.org/wiki/Viscos...osity_of_a_gas

Drag is linearly dependent on density so if you heat the air by 1%, density decreases by 1% and drag also drops by 1%.
https://www.physicsforums.com/thread...e-drag.804563/

So which is it? Does hotter air increase air viscosity (and thus drag), or does hotter air decrease air density (and thus drag)?

08-21-2015, 02:53 PM	#1 (permalink)
Cycle EcoModding Lurker Join Date: Mar 2015 Location: California Posts: 92 Thanks: 10 Thanked 19 Times in 17 Posts	Wait... what? Air viscosity increases with increasing temperature? How do we reconcile the following two viewpoints? Air viscosity increases with increasing temperature: https://en.wikipedia.org/wiki/Viscos...osity_of_a_gas Drag is linearly dependent on density so if you heat the air by 1%, density decreases by 1% and drag also drops by 1%. https://www.physicsforums.com/thread...e-drag.804563/ So which is it? Does hotter air increase air viscosity (and thus drag), or does hotter air decrease air density (and thus drag)?