Sutherland Law

EDE16 · July 9, 2016, 15:50

Hi all,

Im having an issue with mass flow rate thats a little too high at my outlet. Using Stagnation inlet and pressure outlet and just wondering if the reference value and reference temperature in the sutherland law when solving for the dynamic viscosity should be changed to suit the temperature of the gas in your system?

marmot · July 11, 2016, 05:16

The reference values should reflect the type of Gas and the model needs a reference value of viscosity for a given temperature. It might be interesting to try a constant value of viscosity just to see the impact on mass flow rate, depending on how much your temperatures change of course.

Be sure to also ask yourself can the issue with the mass flow rate be based on other things, grid density, turbulence model, geometric location of boundary conditions to name a few,

fluid23 · July 11, 2016, 11:48

I have run into trouble before trying to apply Sutherland's law at inlet and outlet boundaries. Unless you have a large variation in temperature I would recommend using a bulk average temperature of your whole domain to control dynamic viscosity.

July 9, 2016, 15:50	Sutherland Law	#1
EDE16 Member Join Date: Jun 2016 Posts: 52 Rep Power: 9	Hi all, Im having an issue with mass flow rate thats a little too high at my outlet. Using Stagnation inlet and pressure outlet and just wondering if the reference value and reference temperature in the sutherland law when solving for the dynamic viscosity should be changed to suit the temperature of the gas in your system?

July 11, 2016, 05:16		#2
marmot Senior Member kevin alun Join Date: Sep 2011 Location: Germany Posts: 106 Rep Power: 14	The reference values should reflect the type of Gas and the model needs a reference value of viscosity for a given temperature. It might be interesting to try a constant value of viscosity just to see the impact on mass flow rate, depending on how much your temperatures change of course. Be sure to also ask yourself can the issue with the mass flow rate be based on other things, grid density, turbulence model, geometric location of boundary conditions to name a few,

July 11, 2016, 11:48		#3
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	I have run into trouble before trying to apply Sutherland's law at inlet and outlet boundaries. Unless you have a large variation in temperature I would recommend using a bulk average temperature of your whole domain to control dynamic viscosity.