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Uncoupled Fluid Flow and Thermal or Mass Transfer

14 REPLIES 14
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Message 1 of 15
tfjield
697 Views, 14 Replies

Uncoupled Fluid Flow and Thermal or Mass Transfer

I am really trying to perform an uncoupled mass transfer with fluid flow (diffusion with advection) analysis.

 

I can transform the diffusion equation into the heat equation and use the coupled thermal and fluid flow analysis...  Then transform back into concentrations...

 

But is it possible to perform the analysis uncoupled?  Can I do the CFD first, get a result, then do a mass transfer analysis with those flow conditions?  Or do a thermal analysis with those flow conditions?

 

Ideally I would be able to do the CFD using the flow through porous media model, and then do a mass transfer analysis through those results.

 

Is any of this possible?

Using Autodesk CFD and Fusion 360
14 REPLIES 14
Message 2 of 15
Joey.X
in reply to: tfjield

hi, tfjield

I agree that you have legitimate requirement. However, mass transfer in current software does not interact with other analysis types including fluid flow and thermal. 

Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation
Message 3 of 15
tfjield
in reply to: Joey.X

Hi Joey, I understand; I only included what I wanted to do so that you would know my end goal.  But since I can't use mass transfer with fluid flow, I'm wondering about using thermal instead?

 

Currently, I have transformed the diffusion coefficients so that Joules represent mass and temperature represents concentration, and I'm able to get static and transient thermal results that transform back into the appropriate concentration gradients.  But when coupled, I'm not able to use porous materials, etc.  Also, I don't need the simulation to be coupled, since in my case, the "temperature" is not affecting the fluid flow. 

 

Is it possible to do an uncoupled simulation, meaning I just solve the CFD portion first so I have the correct fluid movement, then come back in later and add a heat source?  Can I do this using the porous model?

Using Autodesk CFD and Fusion 360
Message 4 of 15
Joey.X
in reply to: tfjield

If I understand your questions, you are trying to one way fluid to thermal coupling , and the the thermal analysis is a dummy mass transfer(for your convective real mass transfer problem).  If this is correct, you can do this trick but beware some points

- Turn off buoyancy force and turn the gravity to zero . This acts as special body force in fluid/thermal coupling analysis.

- Using same mesh (and comformal) mesh between your fluid analysis and thermal analysis.   

- One way fluid to thermal coupling only to get fluid convection effect in.

- This is not offcially supported. 

- Use identical thermal diffusivity (this is a combination of multiple thermal material parameters) as mass diffusivity in your real model. 

And Yes, you can do fluid through porous media analysis (Darcy flow only) first instead of regular fluid flow.

Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation
Message 5 of 15
tfjield
in reply to: Joey.X

That's exactly what I'm looking for!

 

Thanks!

Using Autodesk CFD and Fusion 360
Message 6 of 15
tfjield
in reply to: Joey.X

Hey Joey,

 

So I'm trying to perform this simulation but I'm not sure how to get the results from the CFD into the thermal analysis.  The wiki said that I should use Loads from File...  But the only options are .xyz, .nod, and .ele files...  It doesn't appear to take the native format files, such as .sfv.

 

If I try to export data from the CFD, I can only export as .out, .csv, or .op2.

 

Can you explain how to get the CFD results into the thermal analysis?

 

Thanks!

 

 

Using Autodesk CFD and Fusion 360
Message 7 of 15
Joey.X
in reply to: tfjield

In thermal analysis/FEAEditor tab/In right hand graphics window/right click/select "fluid convection"(above loads from file"). 

It has options to read .sfv, ufv and .pfv.

Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation
Message 8 of 15
John_Holtz
in reply to: tfjield

The command is also available on the ribbon in the thermal analysis: "Setup > Thermal Loads > Fluid Convection".

 



John Holtz, P.E.

Global Product Support
Autodesk, Inc.


If not provided already, be sure to indicate the version of Inventor Nastran you are using!

"The knowledge you seek is at knowledge.autodesk.com" - Confucius 😉
Message 9 of 15
tfjield
in reply to: John_Holtz

Thanks, guys!  That option is so close to "Loads from File" it's almost embarrassing!  lol

Using Autodesk CFD and Fusion 360
Message 10 of 15
tfjield
in reply to: Joey.X

Hey Guys, so now I have another workflow question...

 

I've created a file with two design scenarios.  The first one is my fluid flow, and the second is the thermal solver.  I have been able to successfully load the fluid velocity results into the thermal solver, thanks to your help.

 

But if I want to run this simulation with a variety of heat fluxes or velocities, it doesn't appear that I can have more than one load case in the thermal solver.  I can change multipliers for heat sources, for example, but only one at a time, then I have to run the model, get the results, change it, run it again, etc.

 

So that brings me to my question:  What is the best way of saving results so that I can bring them back in later and look at them?  Do I have to archive the entire model and results?  Or is there a simpler way to just save a series of results?

 

Thanks again!

Using Autodesk CFD and Fusion 360
Message 11 of 15
Joey.X
in reply to: tfjield

For steady and transient thermal analysis (may reading fluid results as convection loads), there are no official ways (as what I know) to perform multiple computations corresponding to multiple loads since steady thermal has single output only with the loads, and transients thermal analysis has outputs at true time steps which corresponding to a set of loads only.

In comparison, you can do this at (a) steady fluid flow (b) steady coupled fluid/thermal analysis, use pseudo -time steps in steady analysis with different loads.

As ASIM-MECH/MP is highly customizable software, there are some unofficial ways(not from UI) by pushing the load setting into model settings and run (possible multiple) console programs (pre-processor, processor, and after-processor utilities) to get results which corresponding to different loads. Notes this approach handles partial loads only and I would suggest consult this to technical supports and simSquad.

Again, this is a legitimate request (thank you) and is a good candidate for adding loads as the partial parameters of automated "parametric design study" (PDS). 

Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation
Message 12 of 15
tfjield
in reply to: Joey.X

Thanks, Joey.  So do you have any suggestions on how to proceed via the GUI?

 

I have my two design scenarios, where the first is the CFD and the second is thermal.  I want to run the thermal solver with the output from the CFD, but I would like to do it at 5 different flow rates, for example.

 

So I've run the CFD with one load curve consisting of 5 pseudo time steps at 5 different flow rates.  I can select which load case to use in the thermal analysis.

 

But then I need to run the thermal solver 5 times, which isn't a problem, but how do I manipulate the results?  Each time I run it, it overwrites the previous set of results.

 

What is the suggested workflow to be able to manipulate several results from a single simulation?  Archive the whole model every time I get a result?  Or there an easier way to switch back and forth from one set of results to another?

 

This question applies not just to this particular example, but almost every analysis I run I end up adjusting loads and constraints.  How does one manage the results?

 

Thanks!

 

 

Using Autodesk CFD and Fusion 360
Message 13 of 15
Joey.X
in reply to: tfjield

For your specific case, even it's relatively simple, UI does not support it as what you have observed. 

You can do this with a batch files(.bat), copy result files to another location after each run. 

Below is the whole workflow. (need script + tool)

Setup model with 5 pseudo time steps for fluid analysis and one DS for thermal analysis. 

(1) Run 1 , get result 1

     copy results (or whole model including results) to location-1

(2) Touch Model DB(the location to read fluid result at 2nd time step) 

      Run model , get results 2

     copy results 2 (or whole model including results) to location-2  

Repeat step (2)  for step (3) (4) (5)  

The key is that you need a tool to touch model DB silently before running model, or if you have other way to touch excel file silently. That's why I am suggesting for tech support. 

Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation
Message 14 of 15
tfjield
in reply to: Joey.X

I see.  OK, I can do that.  Right now, I'm less interested in updating the database programmatically and more interested in just saving my results.  I'll do as you suggested and create a batch file.  Then I can just click on it and have my results and model copied to an archive location.  At least that way I'll be able to navigate back and forth between the instances without rerunning the simulation.

 

Thanks!

Using Autodesk CFD and Fusion 360
Message 15 of 15
Joey.X
in reply to: tfjield

Good to know it works for you. 🙂

Jianhui Xie, Ph.D
Principal Engineer
MFG-Digital Simulation

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