UDF for y displacement

Mohawk · December 27, 2018, 13:38

Need help

I am working on a Stirling engine , To describe the motion of piston , I have written a UDF for the y displacement or position . Is it correct

* moving piston-CG movement of piston*/

#include "udf.h"

DEFINE_CG_motion(piston,dt,y,time,dtime)
{
real x

y = 0.06869+0.06496 * (sin(3.14*(x-0.22597)/0.54806));

}

regards,

AlexanderZ · December 28, 2018, 00:28

It seems, that your code is not correct,
use Ansys FLuent Customization manual for more information
"Dynamic Mesh DEFINE Macros"

best regards

Mohawk · December 28, 2018, 03:21

Dear AlexanderZ

could you help me with correction of this udf ?

Regards,

RCamp · December 28, 2018, 09:37

You’re missing some variables such as omega I believe.

RCamp · December 28, 2018, 09:40

It should be DEFINE_CG_MOTION(whatever_name, dt,vel, omega, time ,dtime)

RCamp · December 28, 2018, 09:53

With that I also believe you should add vector placements. So your y should be vel[1] = whatever. [1] here saying the y direction. Omega should probably be added as well where it would be omega[2]=0.0 and I would probably even have a vel[0]=0.0. This may not be necessary.

Additionally, I do not think Ansys knows what “x” is here. Instead use vel[0] or you may have to look up in the manual what Ansys stores it’s positions as. I am unsure what your x is rather it is velocity or position.

Best,

RCamp

December 27, 2018, 13:38	UDF for y displacement	#1
Mohawk Member Mustafa Join Date: May 2013 Posts: 54 Rep Power: 13	Need help I am working on a Stirling engine , To describe the motion of piston , I have written a UDF for the y displacement or position . Is it correct * moving piston-CG movement of piston/ #include "udf.h" DEFINE_CG_motion(piston,dt,y,time,dtime) { real x y = 0.06869+0.06496 (sin(3.14*(x-0.22597)/0.54806)); } regards,

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December 28, 2018, 00:28		#2
AlexanderZ Senior Member Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34	It seems, that your code is not correct, use Ansys FLuent Customization manual for more information "Dynamic Mesh DEFINE Macros" best regards

December 28, 2018, 03:21		#3
Mohawk Member Mustafa Join Date: May 2013 Posts: 54 Rep Power: 13	Dear AlexanderZ could you help me with correction of this udf ? Regards,

December 28, 2018, 09:37		#4
RCamp New Member Join Date: Jun 2018 Posts: 8 Rep Power: 7	You’re missing some variables such as omega I believe.

December 28, 2018, 09:40		#5
RCamp New Member Join Date: Jun 2018 Posts: 8 Rep Power: 7	It should be DEFINE_CG_MOTION(whatever_name, dt,vel, omega, time ,dtime)

December 28, 2018, 09:53		#6
RCamp New Member Join Date: Jun 2018 Posts: 8 Rep Power: 7	With that I also believe you should add vector placements. So your y should be vel[1] = whatever. [1] here saying the y direction. Omega should probably be added as well where it would be omega[2]=0.0 and I would probably even have a vel[0]=0.0. This may not be necessary. Additionally, I do not think Ansys knows what “x” is here. Instead use vel[0] or you may have to look up in the manual what Ansys stores it’s positions as. I am unsure what your x is rather it is velocity or position. Best, RCamp