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-   -   Two-Sided Wall in FLUENT (http://www.cfd-online.com/Forums/fluent/82218-two-sided-wall-fluent.html)

mlippy38 November 19, 2010 16:23

Two-Sided Wall in FLUENT
 
Hi all,

I am trying to model a simple two-sided wall with a fluid flowing on each side of the wall. This is an early, simplified step on the way to modeling a compact heat exchanger. I want to see the temperature change between the two fluids and across the wall.

I am attempting to create the geometry in ANSYS DesignModeler and mesh with the ANSYS Mesher as well (both in the Workbench). It has been difficult finding people with experience with these ANSYS products, but I hoped that some people on this forum would be able to help with a few issues I am having.

I am having two issues:

- FLUENT should create a "shadow zone" at the interface between each of the liquids and the solid in order for me to be able to create a "Coupled" thermal BC. For some reason, there are only Wall BCs being created. They do not allow for a Coupled BC to be created. I have simplified my mesh to the point where this must be an issue with the 3-D model created in Design Modeler. Has anyone else seen this issue?

- My mesh loads into FLUENT fine for the first time, but subsequent loads often bring an error that reads: "Model information file is not compatible with mesh." I can't figure out where this is coming from either. Any ideas?

My geometry and models are very simple, and I imagine that there is just one small step that is holding me back. I just can't seem to locate that one issue. I appreciate any response that may lead me in the right direction.

ezabille November 20, 2010 18:06

u must connect facese in your modle choose connect faces from geometry and select all faces in your model

mlippy38 November 22, 2010 10:28

Quote:

Originally Posted by ezabille (Post 284240)
u must connect facese in your modle choose connect faces from geometry and select all faces in your model

I don't see where that is an option in DesignModeler. Can you point me in the right direction?

ezabille November 22, 2010 17:02

in gambit
 
Quote:

Originally Posted by mlippy38 (Post 284343)
I don't see where that is an option in DesignModeler. Can you point me in the right direction?

if u working in gambit ;
after you draw the model and finsh it choose from geometry facec connect faces select all faces then apply
;)

Hathaway March 3, 2011 15:49

. . . and without gambit?
 
I am having the same issue and Gambit is not an option for me. Certainly there must be a way to prepare a mesh for a conjugate solid-fluid heat transfer problem using the ANSYS Workbench Design Modeler and Mesher applications.

Does anyone know how to approach it without resorting to an outside meshing program?

mlippy38 March 3, 2011 16:09

Quote:

Originally Posted by Hathaway (Post 297839)
I am having the same issue and Gambit is not an option for me. Certainly there must be a way to prepare a mesh for a conjugate solid-fluid heat transfer problem using the ANSYS Workbench Design Modeler and Mesher applications.

Does anyone know how to approach it without resorting to an outside meshing program?

In DesignModeler, select all bodies -> Right click -> Form new part

This will connect all the bodies and create shadow zones.

Hathaway March 3, 2011 19:40

Success
 
Quote:

Originally Posted by mlippy38 (Post 297842)
In DesignModeler, select all bodies -> Right click -> Form new part

This will connect all the bodies and create shadow zones.

Amazingly straightforward! I was hesitant to do so previously because I assumed I would lose my ability to have the solid meshed with a coarse hex grid and the fluid with an unstructured tet grid, however after joining the bodies into a single part, I was still able to control the meshing of each body in the same manner. Upon bringing the mesh into FLUENT, all the appropriate shadow zones were in place.

Thanks for the speedy and helpful advice!

dreamz January 23, 2014 01:14

two sided wall, two zone problem
 
Hi,
I am trying a two zone problem for analysing conjugate heat transfer. I have modeled a plate in Ansys design modeler. Over the plate i have modeled an air domain by using frozen option. I joined the two bodies. I did get a shadow zone in fluent. Hence, I get the coupled option activated in heat transfer.
My intention is to get temperature variation in the solid plate as well is in the air domain. For the same I intend to apply heat flux at that face of the plate, which interacts with the air domain. I can apply neumann and dirichlet boundary conditions at other faces of plate and domain.

However, i do not get option of heat flux in coupled boundary condition. Even suppose I want to apply constant temperature boundary condition I don't get any option their. I tried giving the W/m3 value but got convergence in first step, which is wrong.. Kindly help in this problem.
Following is the link for the geometry of my problem...
http://tinypic.com/m/i1fv9v/2
http://tinypic.com/m/i1fv9v/2

thermal energy March 13, 2014 10:12

hello dear friends,


ı have a question about coupled boundry condition. ı need help. thank you. good work.

Should i activate coupled option for both wall and wall-shadow, for each side of the two-sided wall?

dreamz March 13, 2014 10:26

Yes.. You have to activate coupled option for both, wall and wall-shadow.

thermal energy March 13, 2014 10:43

thanks for your quick help. good work dear friend.

thermal energy March 13, 2014 11:00

thanks for your quick reply. good work dear friend

thermal energy March 13, 2014 17:35

hello dreamz, ı have one more question. first, ı study to model pcm-based heat sink with internal fins. ı use vof model. when the vof is activated, three more addition properties come while creating my pcm. these addition properties are "molecular weight", "standard state enthalpy" and "reference temperature". ı do not know first and second values. because pcm that we use does not have spesific molecular structure. also referance tempereture mean what?

ı do not know exactly what should ı do. but in fluent tutorial it said that "When you are solving a reacting flow using the finite-rate or eddy dissipation model, you will need to define the standard state enthalpy". so it does not neccesary or ?

thanks again.

dreamz March 15, 2014 06:23

Hi, thermal energy
Actually I have used the vof model very rarely, since I haven't dealt much into problems using that. So, I may not be the right person to answer this. However, as far as the molecular weight is concerned, it will be the molecular weight of the fluid that you are using. You have mentioned a fluid that flows on both side of the wall, so in materials whichever fluid is specified, put its molecular weight.
Try to find on google for the value. The same you can do for standard state enthalpy which is the value of enthalpy at some specified temperature (mostly it is 25 degree celcius). So, that might be your reference temperature.

However, take my advice with a pinch of salt, since I am not that experienced in using VOF models.. Hope this helps you

thermal energy March 15, 2014 17:24

thank you so much dreamz for your interest. if ı bore you with questions, ı am sorry. also you said, "I may not be the right person to answer this". but may be you give suggestions to me. my problem is:


I try to simulate melting process using VOF model. Pcm is solid phase initialy. Upper part of the solid there is air. They do not mix eachother. the rectangular box is %85 full with solid pcm, %15 air . My primary phase air, secondary phase is pcm (phase change material).

Initial condition of Wholesystem temperature is 293K, but air temp is 300K. how to set air temp ? from materials -referance temperature?

For cell zone condition, all cell zone (air, pcm, fin ) show mixture. Also for example, if I change pcm to phase2, all of cell zone change to phase 2 . is it ok or not

Only for secondary phase (pcm), I patch within fluent by adapt-region-mark then patch. Ok? Value of volume fraction should be 1 or 0 while patching?? I am confused. Initialy pcm is solid. the rectangular box is %85 full with solid pcm. %15 air

For initial values phase-2 volume fraction is 0 or 0.85. Ok?

I did some iteration for a short time to check model. For results, in graphics-countors I can not see total temperature for phase 1 and 2 I see only entalphy values in temperature countor for phase1 and 2.

Alson it shows only for mixture for countors of solidification/melting -liquid fraction . Mixture shows what?

Any interaction should I use like surface tension etc.

Thanks again for your help.

dreamz March 16, 2014 00:51

Thermalenergy: Even I learn a lot when I try to tackle different fluent problems. Please let me know the geometry of your problem, the dimensions etc. Or better, share the geometry file. I would try to solve the problem.

thermal energy March 16, 2014 16:23

thank you dreamz. yazicimy@gmail.com, this is my e-mail adresss. you can send me empty message, then ı send you e-mail back with files. may be it will be more easy for us. what about you? then also we can share the solution here.

thermal energy March 18, 2014 04:37

hello, dreamz?


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