Silicon structrure thermal results going bad in CFD Flex 2016

Anonymous · ‎05-24-2017

HI all,

I have added the "boundary conditions" with heat flex, Just wanted to study the how much heat transferd in different parts of the silicon structure.

3 Volumes I given boundary condition as : 70 W/mm3, and another 3 volumes as :700 w/m3. The results should be controlled .. within 50-70 degree centigrade in different parts of the silicon structure. But it is going beyond that..

I am attaching my report. as well my cfd flex file. Can anybody help me where my Boundary condition or meshing is going bad.

Thanks

Jon.Wilde · ‎06-07-2017

You have a few options

Share the CFZ and I'll take a look
Suppress the air and just assign a film coefficient (5W/k/m2 is a good start) to the outer surfaces of the solids
Stick with what you have and get it working - it should be pretty simple 🙂

What is weird is that your outlet temp is 25C also - did you enlarge the air domain as we said already?

Thanks,

Jon

Jon Wilde
Technical Support Manager

CFD Knowledge Network | CFD Help | My Screencasts | Autodesk Simuation YouTube | CFD Tutorials

Anonymous · ‎06-07-2017

Hi Jon,

Hopefully, we are almost there. But still, preliminary results are not yet produced.

I need your great help to proceed with this. I am eagerly waiting for your suggestions. we can do or how can we tune CFD tool, for getting our expected results.

what we can do or how can we tune Autocad-CFD Flex tool, for getting our expected results.

Pls help me, sir.

Thanking you,

Chandra

Anonymous · ‎06-07-2017

Hi Jon,

Hope your and my new communication here went on same timing. Pls, ignore my last request.

Pls find the newest CFZ file. Pls take a look.

Pls suggest further, I will apply your new "good start" suggestions above.

Many Many thanks for your reply.

Best Regards,

Chandra

Jon.Wilde · ‎06-07-2017

The airbox is still small right? Change it to something like this:

Also, I know we spoke about dimensions before but I am still not totally sure - is this really 700m high?

Thanks,

Jon

Jon Wilde
Technical Support Manager

CFD Knowledge Network | CFD Help | My Screencasts | Autodesk Simuation YouTube | CFD Tutorials

Anonymous · ‎06-10-2017

Hi Jon,

I am facing the strange issue of "Queued" since last night in my laptop.

The CFD Flex not running as attached, snapshot. any solutions for this " I am using " LOCAL" as my solver computer.

Any help on this ?

Thanks

Chandra

Jon.Wilde · ‎06-12-2017

I would stop/uninstall/reinstall the CFD Server manager (be sure to run it as admin for this to work 🙂 ).

Jon Wilde
Technical Support Manager

CFD Knowledge Network | CFD Help | My Screencasts | Autodesk Simuation YouTube | CFD Tutorials

Anonymous · ‎06-13-2017

Hi Jon,

Thanks for your reply. I "repaired" and re-simulated. It was working not in "queued" state.

anyways, To summaries till now.

1. I have increased surround air box, 2d +1d(my_object) +3d=6D in length as per one of the article.

2. I also suppressed air (in 1 experiment, as per your advice). Gave the "film coefficient (5W/k/m2)", for 4 sides of the airbox. Put 1 as its outlet with pressure gauge as 0.

3. Did simulations, with "refinement of meshing"(edges +surfaces). else it was stopping the simulations, with just "auto mesh".

Now results are attached. The docs has the other details, what I did in the experiments.

still, the results are not Correct. Could you pls advice further,?

Best Regards,

Chandra

Jon.Wilde · ‎06-14-2017

1) OK, it's a bit long but OK, it should work 🙂

2) Why? Leave the air meshed, it must be meshed to be considered in the experiment. It was suppressed before and this is part of your problem

2.5) Please follow the guide I shared. You need Temp and P=0 on the bottom of the airbox and a P=0 on the top, nothing more for now

Hope that helps!

Jon

Jon Wilde
Technical Support Manager

CFD Knowledge Network | CFD Help | My Screencasts | Autodesk Simuation YouTube | CFD Tutorials

Anonymous · ‎06-14-2017

Hi Jon,

The guide you had referred, says that 5X in X dir, and 8Z in Z direction of the ext.valume.(air box)

http://help.autodesk.com/view/SCDSE/2014/ENU/?guid=GUID-CAC37152-DE5C-447E-8893-D65EF517A6F6

also this I referred.

http://help.autodesk.com/view/SCDSE/2016/ENU/?guid=GUID-2BF3C8A5-6D70-4F6A-A792-95A27C605E3D

Now I re-created the ext.valume air, and simulated with below BCs:

1. all 4 sides of the ext.volume, as film coief- 5 w/m2.
2. 2 inlet/outlets as pressure gauge as 0 Pa.
3. Total heat generation of air mesh as 22 Watts.(room temp)
4. Internally 3 volumes as 70 watts: Total heat generations.

Now, also I am assuming, the results are not correct?. Pls, find my report.

Do we need to apply "slip/symmetry" on air meshes?
Pls advice further.

Best Regard,
Chandra

Jon.Wilde · ‎06-14-2017

I know it, its close and will be OK 🙂

Those dimensions aren't always fantastic.

Here are my points. You MUST have a temperature at the air inlet, as per the guide and mentioned a few times above also 😉

1. all 4 sides of the ext.volume, as film coief- 5 w/m2 - why? It's OK although not super necessary
2. 2 inlet/outlets as pressure gauge as 0 Pa - You must also have an Ambient Temp on the bottom surface - the air inlet or nothing will work 🙂
3. Total heat generation of air mesh as 22 Watts.(room temp) - Why? What is this doing exactly and what is adding heat to the air? Try without this for now, it doesn't yet make sense to me
4. Internally 3 volumes as 70 watts: Total heat generations. OK, cool 🙂

Jon Wilde
Technical Support Manager

CFD Knowledge Network | CFD Help | My Screencasts | Autodesk Simuation YouTube | CFD Tutorials

Anonymous · ‎06-15-2017

Hi Jon,

I am sorry, I forgot to add surface temperature" as 25 Degree for the inlet, I am extremely sorry. I could do now.

But now, after doing all BCs as guided. The issue is the Tool goes in "Queueing " and else it goes into " Meshing errors ", after refinement as in the screen shots, and the tool goes on repeated printing as below... Could you pls advice what could be best values in "refinement in my case ? as per screen shots ?

and the tool goes on below repeated printing...

"

Mesher process started...

Loading model...