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The simulation of oil flow throught grinding wheel

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Old   August 1, 2017, 09:51
Default The simulation of oil flow throught grinding wheel
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I`m new on this forum so I would like to say Hello to anyone here. I`ve just started my adventure with ansys and the CFX module but I`ve got a very important task to do till the end of August and it is connected with my Thesis. The problem is that I am a very beginner of this kind of problems.
I have to prepare the simulation of oil flow through the rotating
grinding wheel. The grinding wheel is set on the metalic arbor. The oil is supplied centrifugal through the channels inside the metalic arbor to the inner grinding wheel surface and than (thanks to the centrifugal forces) the oil is getting to the outer grinding wheel diameter. The situation is shown in the attached picture (GW.jpg).
Next step is to add the stream of compressed cold air which is flowing from the outer nozzle onto the outer grinding wheel diameter.
I was only able to:
-create the geometry,
-automesh the geometry (Is tetrahedron mesh fine?),
-set fluid and porous domains including interfaces
-perform the simulation with many simplifications (the grinding wheel is stationary; I`ve used a water insteat of oil because I don`t know how to add the specific oil to the library; the porous domain is not define well because I don`t know how to define it as specific grinding wheel etc.).Can anybody help me please?
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File Type: jpg GW.jpg (192.4 KB, 55 views)
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Old   August 1, 2017, 19:33
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Have you done the CFX tutorial examples? They are available on the ANSYS customer webpage. They explain how to do basic operations like this.
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Old   August 2, 2017, 06:52
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Do You mean the ansys tutorials which are available on following adress? http://oximaton.drwx.eu/files/ypol_r..._tutorials.pdf
I have done the Static Mixer tutorial and then few tutorials from youtube. I havent seen any tutorial with porous domain in mentioned ansys tutorials. Maybe You could recommend me some excercises which could be helpful in my task, please?
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Old   August 2, 2017, 06:58
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There are zillions of tutorials on the ANSYS Customer webpage: https://support.ansys.com/portal/sit...CustomerPortal
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Old   August 2, 2017, 07:06
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I think it could be a problem due to I am working on common university license (remotly) and I do not have an access to the data like "*Account Number (Customer Number)" etc. So am I unable to register on mentioned site?
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Old   August 2, 2017, 07:12
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Did you read the big red box which says "Important Message for Students"?
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Old   August 2, 2017, 07:16
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If you do a full install of CFX, you will find the tutorial files under
C:\Program Files\ANSYS Inc\v181\CFX\examples

the link you found was for a very old CFX version. With some more googling, you should be able to find the tutorial pdf for newer versions...
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Old   August 2, 2017, 08:45
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After reading this big red box and further information I think that still need to be registered to enter the Ansys Customer portal. I Maybe I can download the Ansys Academic version and use its account number or maybe I`m wrong. I will try to find the newer CFX pdf tutorial version in google but for now I can see only this old one. From the other hand, how big is the limitation of Academic version of ansys CFX? Should it be enough to solve my task?
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Old   August 2, 2017, 18:57
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Hi Maxim - The tutorial files are on the link you posted, but the instructions of the tutorial are on the ANSYS Customer Page.

SeVV - I don't know what you are trying to do (other than the quick description you gave), and I don't have time to look it up for you if I did. You are going to have to look up the ANSYS Student version capabilities and determine if it is sufficient.
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Old   November 27, 2017, 15:40
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Hi everybody after long break. I`m still trying to do the simulation but I`ve got a lot of issues after adding three phases. Let me show You latest image of domains, mesh and basic setup screenshot (attached). Three phases are necessery, am I right? Air (ambienbce), Compressed cold air and Oil mist? Which turbulence model I need to use and why I still have an "OVERFLOW" error while solving?
Could You help me please?
Attached Images
File Type: jpg MQL SS.jpg (80.4 KB, 35 views)
File Type: jpg Mesh.jpg (113.5 KB, 25 views)
File Type: jpg setup.jpg (53.8 KB, 13 views)
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Old   November 27, 2017, 21:38
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Why do you say three phases? You appear to only have two phases - air and oil.

The overflow error is an FAQ: https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F
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Old   November 28, 2017, 01:53
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Thank You ghorrocks for Your post. I`ve ridden the thread that You`ve send me and I have tried changing the mesh quality (I`ve tried hex dominant and tetrahedrons of size from 0,2 mm to 2 mm), the timestep (now the simulation time is 0,5s and timestep is 0,05 s), I have also tried to use different turbulence models (k-epsilon, k-omega, SST), but I`m still unable to solve the simulation succesfully. So You mean that Air as ambience (ca 20 degree C) and compressed cold air (ca from -5 to +5 degree C) should be treat as the same phase?
Actually I`m not sure what about the oil domain in my simulation because it should be the oil mist, not pure oil. How should I configure this domain and inlet to set it as a mixture of compressed air and oil as a mist?

Last edited by SeVV; November 28, 2017 at 03:59.
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Old   November 28, 2017, 04:02
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There is no point trying to fix a simulation where the fundamental physics setup is wrong. Yes, you only have two phases - air and oil. You need to change the setup as it is a two phase simulation, not three.
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Old   November 28, 2017, 04:09
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Sure, I will reduce the simulation to two phases. How can I set the Oil domain to mixture of Air and Oil as Oil mist?
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Old   November 28, 2017, 04:12
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Have you done the CFX tutorials on multiphase flow? They are available on the ANSYS Customer website. That is the place to start in multiphase simulations.
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Old   November 28, 2017, 04:31
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This is a problem because I am using Ansys academic version and when I am trying to go to customer website and get the tutorials instructions I`m being redirected to the following site:
http://www.ansys.com/academic/free-student-products
and I`m not able to download or even preview any tutorials. Is it possible to find official tutorials somewhere else?
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Old   November 28, 2017, 04:44
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No, that is the only location for them. You are going to have to arrange access through your school/university.
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Old   December 7, 2017, 03:53
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Finally I`ve got access to ansys tutorials. I`ve done the multiphase tutorial and now I`ve learned a little more. Unfortunatelly my simulation still doesn`t work. My geometry was incomplete and there was a void between the ambience (air domain) and porous domain. Untill I`ve fixed it the solver was able to calculate all (with poor result) but after fixing the geometry and filling the void the solver doesn`t finish calculation.. again.. (Overflow or floating point exception ERRORS).
I`ve tried even the single phase simulation with both k-epsilon and SST turbulence model. I would like to perform the transient simulation and It doesn`t work with small timesteps (0,025 s) too. I`m considering what could be still wrong. A friend of mine performed this simulation in steady state in autodesk CFD software and it works (attached images). The transient simulation doesn`t work in autodesk CFD as well as in CFX.
What else can I try to do? Mayby You can give me some advice according to the element size and type? I`m mostly interested in the volume of the porosity domain (grinding wheel) especially in the active grinding wheel surface. I`m sure that this region needs to be based on the best mesh quality. I think that rest of domains could be meshed generally only to provide the proper simulation work. Thank You.
Attached Images
File Type: png 2017-12-07.png (58.6 KB, 21 views)
File Type: png 2017-12-07-1.png (71.2 KB, 21 views)
File Type: png 2017-12-07-2.png (158.4 KB, 22 views)
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Old   December 7, 2017, 05:38
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Please attach your output file.
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Old   December 7, 2017, 13:37
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Here I`m attaching the output file. Sorry for my delay, I was in work - away from my private computer. I`ve changed the extension of the file to .txt because attaching the .out files is not possible. Moreover I`m attaching the link to the compressed .cfx file. Maybe There is any visible issue in the setup..
https://drive.google.com/open?id=1pR...t81yWXDA2mrFtP
Attached Files
File Type: txt Fluid Flow CFX_010.txt (82.4 KB, 7 views)

Last edited by SeVV; December 8, 2017 at 03:18.
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