Easy Fix? Input parameters for Density and Viscosity

LiamH · March 14, 2014, 16:55

Hey Everyone,

I am currently trying to match lab data and I am using the values obtained from the measured viscosity and density. Is it possible to create input parameters for these values or is it much more complicated to do so? I am having to change the fluid properties every time I run a simulation.

macfly · March 15, 2014, 09:52

Hi Liam,

It is easy to do once you have learned the basics about using UDF macros. Look at the Ansys Fluent UDF Manual, the DEFINE_PROPERTY macro is what you're looking for. Look at example 2.3.20.4 in version 15.0 of the manual, it's about temperature-dependent viscosity.

If you have never used UDFs, you will read in the UDF Manual that you have to either compile or interprete a UDF in Fluent. Don't try to compile your UDF, it's a complete headache. Interprete your UDF instead.

Kokemoor · March 17, 2014, 16:53

In v15 you can definitely set the density and viscosity to input parameters; I'm pretty sure you can in 14.5 as well. Having a hard time finding it in the manual, but it's pretty straightforward.

In the Create/Edit Material window where you set the fluid properties, click the drop down menu for 'constant' and select 'New Input Parameter'. It'll prompt you for a name and starting value, just like any other parameter. You should be able to do this for density, viscosity, and any other material properties.

March 14, 2014, 16:55	Easy Fix? Input parameters for Density and Viscosity	#1
LiamH New Member Liam Join Date: Sep 2013 Location: Calgary, Alberta Posts: 19 Rep Power: 12	Hey Everyone, I am currently trying to match lab data and I am using the values obtained from the measured viscosity and density. Is it possible to create input parameters for these values or is it much more complicated to do so? I am having to change the fluid properties every time I run a simulation.

March 15, 2014, 09:52		#2
macfly Senior Member François Grégoire Join Date: Jan 2010 Location: Canada Posts: 392 Rep Power: 17	Hi Liam, It is easy to do once you have learned the basics about using UDF macros. Look at the Ansys Fluent UDF Manual, the DEFINE_PROPERTY macro is what you're looking for. Look at example 2.3.20.4 in version 15.0 of the manual, it's about temperature-dependent viscosity. If you have never used UDFs, you will read in the UDF Manual that you have to either compile or interprete a UDF in Fluent. Don't try to compile your UDF, it's a complete headache. Interprete your UDF instead. LiamH likes this.

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March 17, 2014, 16:53		#3
Kokemoor Senior Member Andrew Kokemoor Join Date: Aug 2013 Posts: 122 Rep Power: 13	In v15 you can definitely set the density and viscosity to input parameters; I'm pretty sure you can in 14.5 as well. Having a hard time finding it in the manual, but it's pretty straightforward. In the Create/Edit Material window where you set the fluid properties, click the drop down menu for 'constant' and select 'New Input Parameter'. It'll prompt you for a name and starting value, just like any other parameter. You should be able to do this for density, viscosity, and any other material properties.