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incorrect cg motion UDF sdof_properties::libudf on zone 6 (assuming no motion) |
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March 18, 2013, 19:51 |
incorrect cg motion UDF sdof_properties::libudf on zone 6 (assuming no motion)
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#1 |
New Member
Mohamed Magdy Mohamed
Join Date: Jan 2013
Posts: 9
Rep Power: 13 |
Hi,
I'm trying to simulate the movement of floating body in sea. I'm using a udf for wall movement : #include "udf.h" #include "dynamesh_tools.h" DEFINE_CG_MOTION(wave,dt,vel,omega,time,dtime ) { vel[0]=((4)*(sin((63)*(time)))); } and another one for the floating body six_dof_property: /************************************************** ***** SDOF property compiled UDF with external forces/moments ************************************************** *****/ #include "udf.h" DEFINE_SDOF_PROPERTIES(sdof_properties, prop, dt, time, dtime) { prop[SDOF_MASS] = 85167.33; prop[SDOF_IXX] = 174112.84; prop[SDOF_IYY] = 28237716.54; prop[SDOF_IZZ] = 28237716.54; prop[SDOF_ZERO_TRANS_X] = TRUE; prop[SDOF_ZERO_TRANS_Y] = TRUE; prop[SDOF_ZERO_ROT_X] = TRUE; prop[SDOF_ZERO_ROT_Z] = TRUE; printf ("\n updated 6DOF properties"); } when i check the "six DOF" option in dynamic mesh the wall doesn't move and this message appears: Unable to read motion history while if i unchecked it an error appears -but the waves are generated correctly-: incorrect cg motion UDF sdof_properties::libudf on zone 6 (assuming no motion) Can someone please help. Thanks. Last edited by M.Magdy; March 22, 2013 at 07:54. |
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March 19, 2013, 03:42 |
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#2 |
Senior Member
Paritosh Vasava
Join Date: Oct 2012
Location: Lappeenranta, Finland
Posts: 732
Rep Power: 23 |
Try this
#include "udf.h" #include "dynamesh_tools.h" DEFINE_CG_MOTION(wave, dt, cg_vel, cg_omega, time, dtime) real t = CURRENT_TIME; { cg_vel[0] = ((4)*(sin((63)*(t)))); cg_vel[1] = 0.0; cg_vel[2] = 0.0; cg_omega[0] = 0.0; cg_omega[1] = 0.0; cg_omega[2] = 0.0; } |
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March 19, 2013, 04:15 |
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#3 |
Senior Member
Paritosh Vasava
Join Date: Oct 2012
Location: Lappeenranta, Finland
Posts: 732
Rep Power: 23 |
Also you do not need 'dynamesh_tools.h'.
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March 19, 2013, 08:28 |
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#4 |
New Member
Mohamed Magdy Mohamed
Join Date: Jan 2013
Posts: 9
Rep Power: 13 |
Thank you but the problem is still the same
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March 19, 2013, 09:51 |
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#5 |
Senior Member
Paritosh Vasava
Join Date: Oct 2012
Location: Lappeenranta, Finland
Posts: 732
Rep Power: 23 |
Sorry initially I thought that there is problem with the first part and did not pay any attention to the second part.
Anyways, there are two things here 1. 'prop[SDOF_ZERO_TRANS_X] = TRUE;' and 'prop[SDOF_ZERO_TRANS_Y] = TRUE;' means that you want/allow the object to move in X and Y direction but not in Z-direction. 2. 'prop[SDOF_ZERO_ROT_X] = TRUE;' and 'prop[SDOF_ZERO_ROT_Z] = TRUE;' means that you want/allow the object to rotate in X and Z axes but not over Y-axis. Don't you think that these two are not consistent with each other? Remove the line with 'prop[SDOF_ZERO_ROT_X] = TRUE;' and then try again. Don't forget to compile and not interpret. |
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March 20, 2013, 09:59 |
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#6 |
New Member
Mohamed Magdy Mohamed
Join Date: Jan 2013
Posts: 9
Rep Power: 13 |
Hi Vasava,
Thanks for your reply but I'm afraid it didn't solve the problem. if you could tell me whether I should in my case check the box beside "six DOF" in dynamic mesh options or not. knowing that :
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March 21, 2013, 03:20 |
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#7 |
Senior Member
Paritosh Vasava
Join Date: Oct 2012
Location: Lappeenranta, Finland
Posts: 732
Rep Power: 23 |
You say that mass of the box is 85167.33 (kg I suppose). Isnt that too heavy to be moved by wave of water?
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March 22, 2013, 00:50 |
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#8 |
New Member
Mohamed Magdy Mohamed
Join Date: Jan 2013
Posts: 9
Rep Power: 13 |
No because the body is a cylinder of length 30m and diameter 3m and 4cm thickness
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March 28, 2013, 08:59 |
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#9 |
New Member
Stefanos Katifeoglou
Join Date: Oct 2011
Location: Athens, Greece
Posts: 19
Rep Power: 15 |
If you allow me, i would like to add a comment that may seem helpful, according to my experience.
Sometimes this occurs if the moving zones aren't adequately defined. In recent fluent editions you don't have to define the meanflow deforming zone. You just need to set the rigid body motion of the moving zone (the moving wall and/or a sourrounding moving fluid zone that includes the boundary layer, around the body, if turbulence modeling is employed). In addition, if there are edge zones recognized by fluent as borders between the rigid-deforming zones, they should also be introduced in the dynamic mesh zones panel as rigidly moving zones, according to the same udf. |
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April 4, 2023, 13:00 |
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#10 |
New Member
Lucía
Join Date: Apr 2023
Posts: 7
Rep Power: 3 |
I have the same problem and I cant find the problem. In my case I want to move one of the walls of a rectangle and my .cpp file is the following one:
#include "udf.h" #include "dynamesh_tools.h" DEFINE_CG_MOTION(wave,dt,cg_vel,cg_omega,time,dtim e) { cg_vel[0]=0.0; cg_vel[1]=(0.12e-6*(sin( 20*3.1415927* time))); cg_vel[2]=0.0; cg_omega[0]=0.0; cg_omega[1]=0.0; cg_omega[2]=0.0; } And when I add to the dynamic mesh I obtain this message: Warning: incorrect grid motion UDF wave::libudf on zone 4 (assuming no motion) If can anyone help. Thanks |
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