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6DOF UDF - contact detection, constrained movement

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Old   January 31, 2020, 12:43
Question 6DOF UDF - contact detection, constrained movement
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Fluent offers movement constraints straight from the GUI, as long as you select 1DOF.



I guess there's also "contact detection", but I don't know how to operate it, nor whether it actually does what I'm looking for.

How would I achieve the same effect in multiple translation axes via custom UDF? Probably something along the lines of:

Code:
	real offset_from_centre = sqrt((DT_CG(dt)[0])^2 + (DT_CG(dt)[1])^2);

	if (offset_from_centre >= abs(clearance*0.99))
	  /*CONSTRAIN MOVEMENT*/;
	else
	  {
	  /*DO NOTHING*/;
	  }
Does anyone have an idea of how to do this?
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Old   January 31, 2020, 14:22
Default Disable Motion
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Contact Detection is meant for action on the basis of contact, e.g., if you wish to simulate closing of engine valves or a jumping ball that reverses its motion as soon as it touches the ground.

Since you wish to stop the motion, just set the velocities to 0. This may not be the solution you are looking for, depending upon what constrains the motion. If you can provide further description of the scenario, better suggestions can be expected.
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Old   January 31, 2020, 19:39
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Quote:
Originally Posted by vinerm View Post
Contact Detection is meant for action on the basis of contact, e.g., if you wish to simulate closing of engine valves or a jumping ball that reverses its motion as soon as it touches the ground.

Since you wish to stop the motion, just set the velocities to 0. This may not be the solution you are looking for, depending upon what constrains the motion. If you can provide further description of the scenario, better suggestions can be expected.
Let's say the body reaches a wall. If I set its velocity to zero, will it not be glued to the wall for ever?

How would I prevent movement away from the centre, but at the same time permit movement towards the centre?
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Old   February 1, 2020, 05:33
Default Constrain the position
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Yes, that's true. It will stay wherever it is. Look for SDOFO_ and SDOFP_ macros within DOF. Those might be useful for what you wish to achieve. Those are new and I have not used any of those but those can be used for constraining the motion; probably those are meant only for constraining the motion.
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