A question about the access of properties?

zouzhengkaoyan · June 27, 2010, 01:45

Hello! In the UDF of Fluent, is there any difference among the macro of MATERIAL_PROP( , ),generic property (name,c,t,prop,id,T)and C_***(c,t),such as MATERIAL_PROP(sp,PROP_RHO),generic property (name,c,t,PROP_RHO,id,T) and rho_s= C_R(cell, htread_s)?
Thank you in advanced!

TDi · July 2, 2010, 17:28

I think those must be the same thing. They're all macros defined by Fluent.

zouzhengkaoyan · July 4, 2010, 23:11

Thank you ! May be they are the same, but I find the results are not same using different macro!

gera · October 31, 2014, 01:56

Hello!

As far as I can judge, the difference is following.

MATERIAL_PROP(sp,PROP_mu) returns the value of viscosity if it is constant. If we use power dependence on temperture the returned value is zero.

generic_property(c,t,PROP_mu,i,T) takes into account temperature in cell c; so we can use viscosity as a function of temperature, but I found that it does not work for power-law option. At the same time, it works well for polynomial option.

Does anybody know how to get viscosity of mixture component if viscosity has the power-law option?

Thank you!

ghost82 · October 31, 2014, 07:40

If you can't access the mixture viscosity when it is set to power-law, what do you think of write the udf for mixture power-law viscosity, declare as a global variable the mixture viscosity so you can access it in other macros?

gera · October 31, 2014, 07:49

I've done it. Of course, it works fine, but if I change viscosity in GUI of Fluent, I need to change my udf. This is inconvinient. So the idea was to use fluent for viscosity calculation. In that case if user changes the viscosity law, for example, to "kinetic" then udf-code automatically uses new viscosity dependence (not necessary to re-compile).

June 27, 2010, 01:45	A question about the access of properties?	#1
zouzhengkaoyan New Member zouzheng Join Date: Jun 2010 Posts: 5 Rep Power: 15	Hello! In the UDF of Fluent, is there any difference among the macro of MATERIAL_PROP( , ),generic property (name,c,t,prop,id,T)and C_***(c,t),such as MATERIAL_PROP(sp,PROP_RHO),generic property (name,c,t,PROP_RHO,id,T) and rho_s= C_R(cell, htread_s)? Thank you in advanced!

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July 2, 2010, 17:28		#2
TDi Member Tim Diller Join Date: Mar 2010 Location: Austin, TX Posts: 32 Rep Power: 16	I think those must be the same thing. They're all macros defined by Fluent.

July 4, 2010, 23:11		#3
zouzhengkaoyan New Member zouzheng Join Date: Jun 2010 Posts: 5 Rep Power: 15	Thank you ! May be they are the same, but I find the results are not same using different macro!

October 31, 2014, 01:56		#4
gera Member Georgy Join Date: Apr 2011 Location: Russia Posts: 32 Rep Power: 15	Hello! As far as I can judge, the difference is following. MATERIAL_PROP(sp,PROP_mu) returns the value of viscosity if it is constant. If we use power dependence on temperture the returned value is zero. generic_property(c,t,PROP_mu,i,T) takes into account temperature in cell c; so we can use viscosity as a function of temperature, but I found that it does not work for power-law option. At the same time, it works well for polynomial option. Does anybody know how to get viscosity of mixture component if viscosity has the power-law option? Thank you!

October 31, 2014, 07:40		#5
ghost82 Senior Member Rick Join Date: Oct 2010 Posts: 1,016 Rep Power: 26	If you can't access the mixture viscosity when it is set to power-law, what do you think of write the udf for mixture power-law viscosity, declare as a global variable the mixture viscosity so you can access it in other macros?

October 31, 2014, 07:49		#6
gera Member Georgy Join Date: Apr 2011 Location: Russia Posts: 32 Rep Power: 15	I've done it. Of course, it works fine, but if I change viscosity in GUI of Fluent, I need to change my udf. This is inconvinient. So the idea was to use fluent for viscosity calculation. In that case if user changes the viscosity law, for example, to "kinetic" then udf-code automatically uses new viscosity dependence (not necessary to re-compile).