Water-Salt Solution - FLUENT

CSolarFD · November 25, 2015, 11:45

Hi everybody

- Does anybody know how to define a water-salt solution in fluent?
- How to construct a three different layers for this water salt solution ( different salt concentratoins) ?

Thanks

CSolarFD · November 26, 2015, 09:34

No answer !

CSolarFD · December 1, 2015, 09:00

Any suggestions ..

Salt dissolved in the water .. How to define that in fluent please?

zobekenobe · July 28, 2017, 08:35

Use the species transport model without reactions. this will allow you to create a mixture template in which you could define the pseudo material (salt water solution) by defining the properties straight away.

MayTheFlowBeWithYou · July 31, 2017, 05:17

I have been doing this by using a user-defined scalar, which represents the mass fraction of salt.

zobekenobe · July 31, 2017, 06:07

Quote:

Originally Posted by MayTheFlowBeWithYou

I have been doing this by using a user-defined scalar, which represents the mass fraction of salt.

Can you share some details or the strategy employed? Would be of great help

MayTheFlowBeWithYou · July 31, 2017, 09:58

Well, a lot of it would depend on what you exactly plan to do with the saline solution. But in the most simple case you could just activate one Use-Defined Scalar (UDS).

If you look in the manual (1.3.1. Single Phase Flow), you'll find the transport equations Fluent will use to handle this UDS.

As you can see from the equations it tried to make the scalar itself dimensionless. This means that the diffusion coefficient used is multiplied by the density (so if you specify the diffusion coefficient of salt in fluent you will have to multiply by the density, otherwise you'll be 1000x too low).

This also implies that, for concentrations, the scalar effectively represents a mass fraction. Thus if you just specify the mass fractions at the inlet(s) and outlet(s), you'll have a simple system that can have a concentration of salt moving through it.

November 25, 2015, 11:45	Water-Salt Solution - FLUENT	#1
CSolarFD New Member SAM Join Date: Nov 2015 Posts: 12 Rep Power: 11	Hi everybody - Does anybody know how to define a water-salt solution in fluent? - How to construct a three different layers for this water salt solution ( different salt concentratoins) ? Thanks

December 1, 2015, 09:00		#3
CSolarFD New Member SAM Join Date: Nov 2015 Posts: 12 Rep Power: 11	Any suggestions .. Salt dissolved in the water .. How to define that in fluent please? Last edited by wyldckat; December 1, 2015 at 16:20. Reason: merged two posts posted on the same day

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November 26, 2015, 09:34		#2
CSolarFD New Member SAM Join Date: Nov 2015 Posts: 12 Rep Power: 11	No answer !

July 28, 2017, 08:35		#4
zobekenobe Member zobekenobe Join Date: Mar 2009 Location: Dublin, Ireland Posts: 72 Rep Power: 17	Use the species transport model without reactions. this will allow you to create a mixture template in which you could define the pseudo material (salt water solution) by defining the properties straight away.

July 31, 2017, 05:17		#5
MayTheFlowBeWithYou Member I have to remain anonymous, I'm sorry. Join Date: Jun 2017 Location: The Netherlands, Delft University of Technology Posts: 48 Rep Power: 9	I have been doing this by using a user-defined scalar, which represents the mass fraction of salt.

July 31, 2017, 09:58		#7
MayTheFlowBeWithYou Member I have to remain anonymous, I'm sorry. Join Date: Jun 2017 Location: The Netherlands, Delft University of Technology Posts: 48 Rep Power: 9	Well, a lot of it would depend on what you exactly plan to do with the saline solution. But in the most simple case you could just activate one Use-Defined Scalar (UDS). If you look in the manual (1.3.1. Single Phase Flow), you'll find the transport equations Fluent will use to handle this UDS. As you can see from the equations it tried to make the scalar itself dimensionless. This means that the diffusion coefficient used is multiplied by the density (so if you specify the diffusion coefficient of salt in fluent you will have to multiply by the density, otherwise you'll be 1000x too low). This also implies that, for concentrations, the scalar effectively represents a mass fraction. Thus if you just specify the mass fractions at the inlet(s) and outlet(s), you'll have a simple system that can have a concentration of salt moving through it.