CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLOW-3D

GMO _problem from rotational angle

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree2Likes
  • 1 Post By MuxaB
  • 1 Post By MuxaB

Reply
 
LinkBack Thread Tools Display Modes
Old   June 27, 2011, 11:47
Default GMO _problem from rotational angle
  #1
Member
 
jiko
Join Date: Sep 2010
Posts: 30
Rep Power: 6
jiko is on a distinguished road
I have a GMO rocking around fixed(Y) axis. It is observed that when the rotational angle is all positive or all negative then the oscillating x force is in reasonable range. but when this rotational angle oscillates from -M to +M value the resulting x-force is nearly zero . why? Please suggest something to fix this issue. thanks
Here the GMO is moving under prescribed sinusoidal velocity.
jiko is offline   Reply With Quote

Old   June 27, 2011, 20:05
Default
  #2
Senior Member
 
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9
MuxaB is on a distinguished road
Quote:
Originally Posted by jiko View Post
I have a GMO rocking around fixed(Y) axis. It is observed that when the rotational angle is all positive or all negative then the oscillating x force is in reasonable range. but when this rotational angle oscillates from -M to +M value the resulting x-force is nearly zero . why? Please suggest something to fix this issue. thanks
Here the GMO is moving under prescribed sinusoidal velocity.
Jiko,

I am not sure I grasp the geometry of the motion. Do you have an prepin please?
MuxaB is offline   Reply With Quote

Old   June 29, 2011, 06:04
Default
  #3
Member
 
jiko
Join Date: Sep 2010
Posts: 30
Rep Power: 6
jiko is on a distinguished road
Thanks M,
Here is the prepin file attached. the phase of 270degree is to rock the GMO evenly on both sides of the initial position. observe the x-force for 0 phase and for 270phase.

thanks.
waiting for your reply.
J
Attached Files
File Type: zip prepin.zip (1.1 KB, 21 views)
jiko is offline   Reply With Quote

Old   June 29, 2011, 23:12
Default
  #4
Senior Member
 
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9
MuxaB is on a distinguished road
Thanks for the file. The first thing I'd suggest is not using the GMRES implicit viscous solver. It does not produce reliable solution and needs further work. In fact, I don't think you need an implicit viscous solver at all. An explicit solver is always better if it does not limit the time step too much. In your case the fluid is water, so I am sure the time step stability is controlled by convection rather than viscous dissipation.

Let me know if it behaves differently with the explicit sovler.
spaudel likes this.
MuxaB is offline   Reply With Quote

Old   July 1, 2011, 05:18
Default
  #5
Member
 
jiko
Join Date: Sep 2010
Posts: 30
Rep Power: 6
jiko is on a distinguished road
Thanks Michael,

Under Numerics--> the allowed option for
pressure solver is only Implicit but for viscous stress I did switched it to the suggested Explicit. But unfortunately the problem is still there.

Could you suggest another remedy Please?

even if you try x-translation (of any GMO) and put the initial phase as 270degree. the unrealistic x-force can be observed.


jiko is offline   Reply With Quote

Old   July 1, 2011, 17:52
Default
  #6
Senior Member
 
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9
MuxaB is on a distinguished road
i'll check it out this weekend
MuxaB is offline   Reply With Quote

Old   July 12, 2011, 09:27
Default
  #7
Member
 
jiko
Join Date: Sep 2010
Posts: 30
Rep Power: 6
jiko is on a distinguished road
Hi Michael, Just a gentle reminder that I am still waiting to hear from you.
Thanks.


jiko is offline   Reply With Quote

Old   July 12, 2011, 14:04
Default
  #8
Senior Member
 
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9
MuxaB is on a distinguished road
Yes, sorry, will check it out as soon as I can.

Mike
MuxaB is offline   Reply With Quote

Old   July 12, 2011, 19:59
Default
  #9
Senior Member
 
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9
MuxaB is on a distinguished road
Quote:
Originally Posted by jiko View Post
Hi Michael, Just a gentle reminder that I am still waiting to hear from you.
Thanks.


Jiko, I ran it as you sent me and get a pretty substantial force in the x-direction. So far it is just short of 5 seconds. See the plot
Attached Images
File Type: jpg plots_on_screen_2.jpg (45.5 KB, 25 views)
spaudel likes this.
MuxaB is offline   Reply With Quote

Old   July 18, 2011, 05:11
Default
  #10
Member
 
jiko
Join Date: Sep 2010
Posts: 30
Rep Power: 6
jiko is on a distinguished road
Thanks for your time Michael, I wonder why on my PC it turns out to be much different. I would be grateful if you could send me the prepin used for these results from your end.
thanks
jiko is offline   Reply With Quote

Old   July 29, 2011, 15:59
Default
  #11
Senior Member
 
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9
MuxaB is on a distinguished road
Quote:
Originally Posted by jiko View Post
Thanks for your time Michael, I wonder why on my PC it turns out to be much different. I would be grateful if you could send me the prepin used for these results from your end.
thanks
Jiko, it is the same file you sent me. I ran it with version 10.0 of FLOW-3D. Version 9.4 should give the same results.
MuxaB is offline   Reply With Quote

Old   August 1, 2011, 04:17
Default
  #12
Member
 
jiko
Join Date: Sep 2010
Posts: 30
Rep Power: 6
jiko is on a distinguished road
thanks Mickael, so its mean that version 10 solves my problem.
jiko is offline   Reply With Quote

Old   August 15, 2011, 11:51
Default
  #13
Senior Member
 
michael barkhudarov
Join Date: Mar 2009
Posts: 331
Rep Power: 9
MuxaB is on a distinguished road
I hope so...
MuxaB is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
InterFoam contact angle JoaoMiranda OpenFOAM Running, Solving & CFD 3 August 26, 2014 11:29
Import netgen mesh to OpenFOAM hsieh Open Source Meshers: Gmsh, Netgen, CGNS, ... 32 September 13, 2011 05:50
[ICEM] Rotational periodicy setup Procyon ANSYS Meshing & Geometry 0 April 30, 2011 07:55
Normal vector, slope and aspect angle g_niro Main CFD Forum 0 February 2, 2011 18:24
Proper output of angle of attack in CFX post Kevin CFX 3 October 18, 2006 12:18


All times are GMT -4. The time now is 18:23.