Simple Fluid Mixing

bman1994 · July 22, 2014, 14:09

I apologize if this is a basic question, but I am trying to model the mixing of 4 reagents with properties identical to water in a microfluidic device. I have tried making individual materials and assigning each a phase in the multiphase mixing model, but the model ended up being incorrect. I could not find a relevant tutorial, anyone have any advice or a tutorial they could refer me to?
Thanks

Mohawk · July 22, 2014, 14:13

Could you upload the geometry and specify the inlets and outlet on it ?

bman1994 · July 22, 2014, 14:22

No, unfortunately I really cant. I have 4 pressure inlets, and one pressure outlet. I simply want to have different species enter at each inlet. Is there any simple way to do that?

Mohawk · July 22, 2014, 14:31

First u need to use multiphase model . And assign a
Volume fraction 1 for for each inlet and at outlet calculate the volume fraction for each phase . In material u need to add four materials

sescobar · July 22, 2014, 15:22

I fail to understand why would you use multiphase model. If all reagents have the same properties and are in the same phase, you could model the problem using species transport model.

Mohawk · July 22, 2014, 15:30

What fluids are you going to use ?

bman1994 · July 22, 2014, 16:01

Until recently, I couldn't figure out how to add custom species to species transport model, I just figured out how to edit the mixture template to include my custom materials. I assume species transport will work better, Ill try and model this one now. Is there documentation on this? I couldnt seem to find it. As far as the fluid, water can be used to approximate each reagent.

bman1994 · July 22, 2014, 17:11

still having trouble, anyone know where i could find an example like this in documentation?

sescobar · July 22, 2014, 17:56

The way I would go about it would be to select an appropriate mixture template. It may be one that has the same number of species that you want to model. Then you can edit each of the species properties to set them equal to water and equal to each other. You can even edit the names and change them to water-1, water-2, etc. Make sure you appropriately define the diffusion coefficient, since it will play an important role on your mixing calculations.
I guess that in you have at least 4 inlet for your domain. Set the species mass fraction or mole fraction for each of the correspondent specie on each inlet. If each inlet is 100% one specie, it would be something like: inlet-1, mass fraction of water-1=1.0, and so on.
Your discretization schemes and mesh size will influence your results. It would be pertinent to try different mesh sizes in order to establish the influence of numerical diffusion. Selecting higher order monotonic schemes should reduce the amount of numerical diffusion.

July 22, 2014, 14:09	Simple Fluid Mixing	#1
bman1994 New Member MD: MARYLAND Join Date: Jul 2014 Posts: 4 Rep Power: 12	I apologize if this is a basic question, but I am trying to model the mixing of 4 reagents with properties identical to water in a microfluidic device. I have tried making individual materials and assigning each a phase in the multiphase mixing model, but the model ended up being incorrect. I could not find a relevant tutorial, anyone have any advice or a tutorial they could refer me to? Thanks

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Incompressible, miscible mixing of two fluid stream OpenFOAM	Nishchal	OpenFOAM Running, Solving & CFD	6	October 9, 2019 07:55
Fluid Dynamics Eng - PAX Mixer - San Rafael, CA	Gary Jong	FLUENT	0	February 25, 2008 21:46
Simple structure & fluid interaction	Bren	Main CFD Forum	13	August 10, 2007 15:22
Inhomogenous two fluid model with mixing fluids	vkaufmann	OpenFOAM Running, Solving & CFD	0	January 8, 2007 13:09
(Fluid mixing) Mass fraction contours	Toni Vainio	Siemens	5	February 20, 2005 13:59

July 22, 2014, 14:13		#2
Mohawk Member Mustafa Join Date: May 2013 Posts: 54 Rep Power: 13	Could you upload the geometry and specify the inlets and outlet on it ?

July 22, 2014, 14:22		#3
bman1994 New Member MD: MARYLAND Join Date: Jul 2014 Posts: 4 Rep Power: 12	No, unfortunately I really cant. I have 4 pressure inlets, and one pressure outlet. I simply want to have different species enter at each inlet. Is there any simple way to do that?

July 22, 2014, 14:31		#4
Mohawk Member Mustafa Join Date: May 2013 Posts: 54 Rep Power: 13	First u need to use multiphase model . And assign a Volume fraction 1 for for each inlet and at outlet calculate the volume fraction for each phase . In material u need to add four materials

July 22, 2014, 15:22		#5
sescobar New Member Join Date: Jun 2011 Posts: 22 Rep Power: 15	I fail to understand why would you use multiphase model. If all reagents have the same properties and are in the same phase, you could model the problem using species transport model.

July 22, 2014, 15:30		#6
Mohawk Member Mustafa Join Date: May 2013 Posts: 54 Rep Power: 13	What fluids are you going to use ?

July 22, 2014, 16:01		#7
bman1994 New Member MD: MARYLAND Join Date: Jul 2014 Posts: 4 Rep Power: 12	Until recently, I couldn't figure out how to add custom species to species transport model, I just figured out how to edit the mixture template to include my custom materials. I assume species transport will work better, Ill try and model this one now. Is there documentation on this? I couldnt seem to find it. As far as the fluid, water can be used to approximate each reagent.

July 22, 2014, 17:11		#8
bman1994 New Member MD: MARYLAND Join Date: Jul 2014 Posts: 4 Rep Power: 12	still having trouble, anyone know where i could find an example like this in documentation?

July 22, 2014, 17:56		#9
sescobar New Member Join Date: Jun 2011 Posts: 22 Rep Power: 15	The way I would go about it would be to select an appropriate mixture template. It may be one that has the same number of species that you want to model. Then you can edit each of the species properties to set them equal to water and equal to each other. You can even edit the names and change them to water-1, water-2, etc. Make sure you appropriately define the diffusion coefficient, since it will play an important role on your mixing calculations. I guess that in you have at least 4 inlet for your domain. Set the species mass fraction or mole fraction for each of the correspondent specie on each inlet. If each inlet is 100% one specie, it would be something like: inlet-1, mass fraction of water-1=1.0, and so on. Your discretization schemes and mesh size will influence your results. It would be pertinent to try different mesh sizes in order to establish the influence of numerical diffusion. Selecting higher order monotonic schemes should reduce the amount of numerical diffusion.