CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT > Fluent UDF and Scheme Programming

Modelling Contact and Frictional Force in 6DOF

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 17, 2021, 12:31
Default Modelling Contact and Frictional Force in 6DOF
  #1
New Member
 
Will Crawford-Jones
Join Date: Jan 2021
Posts: 19
Rep Power: 2
wcj1n18 is on a distinguished road
Hi,

Let's say I have a 6DOF model and I would like this to start in 'contact' with the wall, hence, it will begin such that the edge of my 6DOF object is at the position of the proximity threshold. Based on this, contact is occurring. Now, I have little understanding of UDFs, however, I think it should be possible for me to write a UDF that calculates the normal force from the 6DOF object to the wall. This would consist of the component of all shear stresses, pressures and the weight of the object in the direction of the wall's normal. Rather than writing a UDF that simply reflects the velocity at contact, I would like to write one that models the contact force from wall to the object.

I think this may be possible by defining a thread that is in 'contact' with the wall (there are contact macros for this) and overwriting the pressure on these cell faces and making this equal and opposite to the shear stresses, pressures and weight I previously mentioned. Is there a way I can overwrite pressures in this way?

I thought that DEFINE_ADJUST may work but it seems to only work across the whole domain. Presumably there is an equivalent to DEFINE_ADJUST for a given thread, in this case the contact thread? This would balance the forces on the 6DOF object and prevent motion.

As an added point I would also like to do the same with friction. If I can solve this problem with the contact force then it can't be much of a leap to do the same by overwriting the shear force on the 6DOF object as well (again, at the point of 'contact').

Thanks a lot for any advice you can provide!
wcj1n18 is offline   Reply With Quote

Old   March 12, 2021, 02:41
Default
  #2
Senior Member
 
Alexander
Join Date: Apr 2013
Posts: 1,639
Rep Power: 23
AlexanderZ will become famous soon enough
Quote:
possible by defining a thread that is in 'contact' with the wall (there are contact macros for this)
you've told there is macro to find cells in contact zone, I don't know this marco, but if you know you should use it

DEFINE_ADJUST is not related to loop over domain
its a macro which executes your code before each iteration/timestep, that's it, nothing else

so if you have macro to check if the cell is in contact that's what you need, loop over all cells and check the criteria
__________________
best regards


******************************
press LIKE if this message was helpful
AlexanderZ is offline   Reply With Quote

Old   March 12, 2021, 04:17
Default
  #3
New Member
 
Will Crawford-Jones
Join Date: Jan 2021
Posts: 19
Rep Power: 2
wcj1n18 is on a distinguished road
Thanks for the response. I think then it is in theory possible to create a UDF that simulates normal contact forces as your body moves in contact with boundaries. What I'm less sure about is frictional (tangential) forces. For now, I have switched to Star CCM+, however, I may return to Fluent in the future.
Thanks again!
wcj1n18 is offline   Reply With Quote

Reply

Tags
contact, define_adjust macro, sdof, udf

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
frictional contact problem zizou3 ANSYS 0 April 29, 2014 12:50
Segment to Segment frictional contact sksharma317 Structural Mechanics 0 December 28, 2013 00:04
Average frictional stress on surface weighted by elements area (Ansys Workbench Mech) Giulio89 Structural Mechanics 0 July 8, 2013 09:44
Ansys Workbench contact problem! JoelHenrik ANSYS 1 October 1, 2010 14:57


All times are GMT -4. The time now is 15:50.