locator-based function

armin najarian · May 31, 2016, 12:22

Hello.
i am new in cfx.
i need a locator-based function in cfx.
in expressions there is a locator-based function of force: [force()@...].
but i want this function: position()@
what should i do?
thanks dears.

Opaque · May 31, 2016, 12:31

Perhaps you should rephrase your needs differently. Others in the forum may have face similar challenges and they were able to resolve it somehow.

It seems you have already concluded what you need though it may be possible (if properly described) to do with the existing functionality.

What do you think ?

armin najarian · May 31, 2016, 16:11

thanks for your answer.
when i wrote [position_x()@rigidbody], cfx gave me an error.
i think i should write a user function or user subroutine to achive my goal.
but i dont know exactly how to do it.

Opaque · May 31, 2016, 21:12

Once again you are not providing information of what you need, but how you approached and attempting others read between the lines.

I will take a good guess here: you seem to need the X,Y or Z location of the center of mass of a rigid body in your setup. To do so, a good advice is that you should read the CFX Reference Guide/Chapter 15 Functions in ANSYS CFX.

In there, you can look at the functions provided to access rigid body information, say "rbstate (<rbvar> <Axis>) @ <Location>". I let you read through the list of what "rbvar"s are available and see if any is helpful to you..

Hope the above helps,

-Maxim- · June 1, 2016, 02:19

http://xyproblem.info/

In Post, you can also set points and use the probe(variable)@point function.
If you want to evaluate variables in certain points during the run via solver manager, I have described a way recently using source points in Pre. The search function in this forum will find that post.

armin najarian · June 1, 2016, 06:35

thanks for your answering
in fact i have a boat that it has 6 degree of freedom and i want to give it an external force (instead of modeling its propeller)
so i need to write an expression for the external force and as i said my problem is 6dof.
at first i wanted to define a coordinate that moves with the rigid body. but i could not define coordinate like that.
so how should i give the boat an external force that always be in the direction of the longitudinal axis of the boat?

armin najarian · June 1, 2016, 06:37

thank u so much.
i want it in cfx pre.
i check this by using source points.

May 31, 2016, 12:22	locator-based function	#1
armin najarian New Member armin najarian Join Date: Aug 2015 Posts: 14 Rep Power: 11	Hello. i am new in cfx. i need a locator-based function in cfx. in expressions there is a locator-based function of force: [force()@...]. but i want this function: position()@ what should i do? thanks dears.

May 31, 2016, 12:31		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,860 Rep Power: 33	Perhaps you should rephrase your needs differently. Others in the forum may have face similar challenges and they were able to resolve it somehow. It seems you have already concluded what you need though it may be possible (if properly described) to do with the existing functionality. What do you think ? armin najarian likes this.

June 1, 2016, 06:35		#6
armin najarian New Member armin najarian Join Date: Aug 2015 Posts: 14 Rep Power: 11	thanks for your answering in fact i have a boat that it has 6 degree of freedom and i want to give it an external force (instead of modeling its propeller) so i need to write an expression for the external force and as i said my problem is 6dof. at first i wanted to define a coordinate that moves with the rigid body. but i could not define coordinate like that. so how should i give the boat an external force that always be in the direction of the longitudinal axis of the boat? Last edited by armin najarian; June 5, 2016 at 02:42.

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May 31, 2016, 16:11		#3
armin najarian New Member armin najarian Join Date: Aug 2015 Posts: 14 Rep Power: 11	thanks for your answer. when i wrote [position_x()@rigidbody], cfx gave me an error. i think i should write a user function or user subroutine to achive my goal. but i dont know exactly how to do it.

May 31, 2016, 21:12		#4
Opaque Senior Member Join Date: Jun 2009 Posts: 1,860 Rep Power: 33	Once again you are not providing information of what you need, but how you approached and attempting others read between the lines. I will take a good guess here: you seem to need the X,Y or Z location of the center of mass of a rigid body in your setup. To do so, a good advice is that you should read the CFX Reference Guide/Chapter 15 Functions in ANSYS CFX. In there, you can look at the functions provided to access rigid body information, say "rbstate (<rbvar> <Axis>) @ <Location>". I let you read through the list of what "rbvar"s are available and see if any is helpful to you.. Hope the above helps,

June 1, 2016, 02:19		#5
-Maxim- Senior Member Maxim Join Date: Aug 2015 Location: Germany Posts: 415 Rep Power: 13	http://xyproblem.info/ In Post, you can also set points and use the probe(variable)@point function. If you want to evaluate variables in certain points during the run via solver manager, I have described a way recently using source points in Pre. The search function in this forum will find that post.

June 1, 2016, 06:37		#7
armin najarian New Member armin najarian Join Date: Aug 2015 Posts: 14 Rep Power: 11	thank u so much. i want it in cfx pre. i check this by using source points.