# Sliding Mesh Problem

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 August 19, 2016, 05:29 Sliding Mesh Problem #1 Member   CT Join Date: May 2016 Location: Turkey Posts: 32 Rep Power: 9 Hi All, I am trying to solve an axial fan problem and i realized that if i use mrf model, i couldnt calculate the real torque value because of the fluid motion in the mrf zone. I would like to calculate the real torque value. I mean if i use mrf model, the fluid in the mrf zone is rotating with the value i described. Than i thought that if i use sliding model or dynamic mesh model, it would be more accurate solution. But i tried to use sliding mesh model and i activate mesh motion instead frame motion(same rpm). When i tried to calculate again, fluent is giving me a mesh error. The error is negative volüme detected. But i check mesh before analysis, there was not any negative volume. Also when i do it with frame motion, there is no any problem about mesh. I can solve the problem within real velocity and pressure values. What should i do to calculate the real torque value? Can anyone give me a udf for dynamic mesh? or any advise about sliding mesh? Thank you! Have a good day

 August 21, 2016, 18:36 #2 Senior Member   Have a nice time! Join Date: Feb 2016 Location: mech.eng.ahmedmansour@gmail.com Posts: 291 Rep Power: 11 Have you solved the problem? Is it a 2D simulation?

 August 22, 2016, 03:37 #3 Member   CT Join Date: May 2016 Location: Turkey Posts: 32 Rep Power: 9 No, i didnt solve it yet. It is a 3D problem.

 August 22, 2016, 04:33 #4 Senior Member   Aurelien Thinat Join Date: Jul 2010 Posts: 165 Rep Power: 15 Hi, For a sliding mesh, you need a perfect interface between the rotor and the stator. Then from your mrf setup, you can type in the fluent consol : Code: ```/define/boundary-conditions/modify-zone/mrf-to-sliding-mesh rotor-cellzone-name ()``` It should create the interface and you will be able to launch the simulation. Be aware that you need a full 360° model or the same angular subdomains between rotor and stator. Aurelien

 August 22, 2016, 04:41 #5 Member   CT Join Date: May 2016 Location: Turkey Posts: 32 Rep Power: 9 I think i have good interface between rotational and stationary bodies. I dont have stator its only a blade in the mrf zone and inlet, outlet bodies which has pressure inlet&outlet with 0 pa. They are from new part zones and interface is created automatically. Should i make this connection by using fluent interface or is it enough to make in form new part? Thank you Aurelien!

 August 22, 2016, 04:47 #6 Senior Member   Aurelien Thinat Join Date: Jul 2010 Posts: 165 Rep Power: 15 Well, if you don't have a stator cellzone, you didn't need any interface. From what you are saying, you just need to : 1) activate the sliding mesh option 2) define the rotating velocity, 3) check the axis and the origin. 4) in the dynamic mesh menu, you shouldn't have anything activated. EDIT : By stator, I mean "not rotating volume".

 August 22, 2016, 05:00 #7 Member   CT Join Date: May 2016 Location: Turkey Posts: 32 Rep Power: 9 Ah than yes i have stator volume. I did that options but an error has been occupied when i ran the calculation. The error is negative mesh volume detected. But if i use mrf model and run calculation there isnt a problem.

 August 22, 2016, 10:13 #8 Senior Member   Have a nice time! Join Date: Feb 2016 Location: mech.eng.ahmedmansour@gmail.com Posts: 291 Rep Power: 11 Check out this.. It may help you https://www.youtube.com/watch?v=KFrZoDWUC5s

 August 23, 2016, 03:25 #9 Member   CT Join Date: May 2016 Location: Turkey Posts: 32 Rep Power: 9 I solved it. In order to help other people i will explain how i solved it. I refined the mesh and i used fluent interface instead form new part model. However i already couldnt calculate the real torque value. In my opinion, it is only calculateable when use dynamic mesh model. And i cant write an udf for that case. subaru1989 likes this.

 September 2, 2016, 08:05 #10 Member   CT Join Date: May 2016 Location: Turkey Posts: 32 Rep Power: 9 I still could not calculate the torque value, searched on the forum but there is no any valid solve about this problem. I tried to set the referance value to area: blade and hub surface area and length: blade Radius but still couldnt reach the experimental torque value. I guess this topic is the biggest problem of fluent software. If some super hero WHO has perfect fluent skills can solve this problem, please notifiy me on that topic.

 September 2, 2016, 08:09 #11 Senior Member   Have a nice time! Join Date: Feb 2016 Location: mech.eng.ahmedmansour@gmail.com Posts: 291 Rep Power: 11 contact with me on 12317@eng.asu.edu.eg please

 September 2, 2016, 08:42 #12 Senior Member   Have a nice time! Join Date: Feb 2016 Location: mech.eng.ahmedmansour@gmail.com Posts: 291 Rep Power: 11 Do you have a problem in contacting me?

 September 2, 2016, 08:58 #13 Member   CT Join Date: May 2016 Location: Turkey Posts: 32 Rep Power: 9 No, I've sent you an e-mail.

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