Density and Dynamic Viscosity at high temperatures

kailashpp1990 · April 5, 2017, 03:17

I have inlet air( exhaust from gas) Temperature at 900 degrees, should i use air density at STP or 900 degree C to calculate the velocity ? Also what about the dynamic viscosity at 900 degree C or 300 degree C ( since newtonian fluids are used in navier stokes, viscosity is considered constant ? ) Both these will affect the mach number and reynolds number to decide what type of flow i have to use.

Thank u

FMDenaro · April 5, 2017, 04:52

https://www.cfd-online.com/Wiki/Sutherland%27s_law

kailashpp1990 · April 6, 2017, 01:51

sutherlands law has to be applied in the simulation or use it to calculate the viscosity at that temperature by hand and keep it constant for the simulation. my doubt is in the navier stokes equation the viscosity is maintained constant, right ?

FMDenaro · April 6, 2017, 03:11

If the temperature is high, the viscosity can no longer be considered constant in the simulation

April 5, 2017, 03:17	Density and Dynamic Viscosity at high temperatures	#1
kailashpp1990 New Member Kailash Join Date: Sep 2015 Posts: 8 Rep Power: 10	I have inlet air( exhaust from gas) Temperature at 900 degrees, should i use air density at STP or 900 degree C to calculate the velocity ? Also what about the dynamic viscosity at 900 degree C or 300 degree C ( since newtonian fluids are used in navier stokes, viscosity is considered constant ? ) Both these will affect the mach number and reynolds number to decide what type of flow i have to use. Thank u

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April 5, 2017, 04:52		#2
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,773 Rep Power: 71	https://www.cfd-online.com/Wiki/Sutherland%27s_law

April 6, 2017, 01:51		#3
kailashpp1990 New Member Kailash Join Date: Sep 2015 Posts: 8 Rep Power: 10	sutherlands law has to be applied in the simulation or use it to calculate the viscosity at that temperature by hand and keep it constant for the simulation. my doubt is in the navier stokes equation the viscosity is maintained constant, right ?

April 6, 2017, 03:11		#4
FMDenaro Senior Member Filippo Maria Denaro Join Date: Jul 2010 Posts: 6,773 Rep Power: 71	If the temperature is high, the viscosity can no longer be considered constant in the simulation