Mixing two types of fluid

Submitted by Sauzer on October 24, 2010 - 13:56

Questions

Is it possible to mix two different fluids in the same volume?
For example air from an inlet and smoke from another inlet (with different temperatures)?
Thank you

Assume Smoke is Air

Submitted by symscape on October 24, 2010 - 16:11.

Not sure you need to class air and smoke as different fluids. So assuming both fluids to be air, with different inlet conditions you should be fine.

If you had say air and carbon dioxide then you would have two different fluids (two species with different material properties) - which at present Caedium doesn't support.

Can you explain how to set a

Submitted by Sauzer on December 23, 2011 - 14:25.

Can you explain how to set a problem like this:
A three-way duct, with two inlets and one outlet; The two inlets have two different flow rates and temperatures.
Is it possible to have the mixed temperature at outlet and flow rate?
(The fluid is the same)
Thank you.

Setup similar to Incompressible Flow Through a Pipe into a Box

Submitted by symscape on December 23, 2011 - 15:42.

I'll assume incompressible steady state flow.

Try following the setup for the tutorial "Incompressible Flow Through a Pipe into a Box", and also:

Select Substance->State:Gas->Heat Transfer = Yes
Switch off buoyancy by setting Substance->Properties->Reference->g (gravity) = [0 0 0]
Velocity (U) and temperature (T) reference values should be set to be representative of the mean flow
Set Physics:Initial->U = Fixed Value, Value = [0 0 0] - unless there's a dominant flow direction
For each inlet set Physics:Inlet->Type:Default->U = Surface Normal, Speed = your value, and T = Fixed Value, Value = your value

Make sure the outlet is positioned well away from your inlets to let the flow develop.

At the outlet you can examine the temperature surface contours using the Scalar Fields->T tool on the Results Tool Palette as a Colormap.

To calculate the volume flow rate = Sum(U.Mag * A) you'll need to create a new results, for more details see "Fluid Flow Around a Sphere: Theory Comparison". As a check the outlet volume flow rate should be equal to the sum of the volume flow rates at your inlets.

Thank you, now I'm able to

Submitted by Sauzer on December 28, 2011 - 07:33.

Thank you, now I'm able to run the simulation!
(I've tried a lot of times with the same procedure before, probably the problem was the not developed flow).
I don't understand this:

Velocity (U) and temperature (T) reference values should be set to be representative of the mean flow.

I need to estimate the resulting velocity and temperature? Why I have to do this?
I'm learning cfd and I apologize for my questions.
I'm discovering your software and I'm impressed.

Thanks

Estimates based on hand calculations

Submitted by symscape on December 28, 2011 - 10:13.

The reference values can either be exact if you are going to use them for your inlets/outlet BCs. Or if not then they only need to be in the right range +- 25%.

It's always a good idea to have an estimate of your expected values (e.g., U) based on hand calculations (e.g., Bernoulli's principle, conservation of mass/volume flow) so you can assess your CFD results. It's easy to mistype a value and have your results off by an order of magnitude.

"To calculate the volume flow

Submitted by Sauzer on January 19, 2012 - 10:45.

"To calculate the volume flow rate = Sum(U.Mag * A) you'll need to create a new results, for more details see "Fluid Flow Around a Sphere: Theory Comparison". As a check the outlet volume flow rate should be equal to the sum of the volume flow rates at your inlets."

Thanks, I've created the results that I need. (Although I need to pay attention to scalar/vector variables, as result can varies).
Now I would like to know if I can save results formulas to use them in every project that I start.
And is there a way to see the precise result without seeing it in monitor with grid?
(I have to increase the number of subdivisions to estimate a right value)
Thank you

Load template project first

Submitted by symscape on January 19, 2012 - 11:05.

To reuse your new monitor results take your existing project and use it as a template and then start each new project by loading the template project first. The template has to use the new result in a monitor otherwise it will be dropped - you can delete the simulation model (3D views) to free up memory.

To extract the precise values from a monitor use File->Export with Save as type: Plot Series (*.csv).

Symscape