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Old   April 17, 2010, 06:03
Default Flapping Wing motion
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Balkrishna Patankar
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I am doing a CFD analysis of flapping wing motion in FLUENT . For the same I have written a UDF which looks like :
Code:
#include "udf.h"

DEFINE_CG_MOTION(myudf, dt, v_cg, omega, time, dtime) 
{

     Thread *t; 


    real c=0.2; 

    real omega_t=6.28; 
     NV_S(v_cg, =, 0.0);
    NV_S(omega, =, 0.0); 

     t=DT_THREAD((Dynamic_Thread *)dt); 

     v_cg[1]=2*3.14*c*cos(omega_t*time); 
    omega[2]=3.14*3.14*sin(omega_t*time)/4; 

     Message("time:%f vx_cg:%f vy_cg:%f omegaz:%f \n",time, v_cg[0],v_cg[1],omega[2]);
}
Which is the code given in Adrien Pesenti's website . However I have troubles hooking this udf to FLUENT. My airfoil doesnt move (change its angle) when I check mesh motion under Solve-> Mesh Motion. Please can anyone help me out with this ....
Also another option is actually defining the path taken by the CG in time ..... writing a profile file .... . How does one actually write a profile file ???
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Old   August 3, 2010, 02:13
Default rotation about z axis
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ahmad
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hi dear balkrishna...
long ago you were studying a case that contained flapping wing motion, now i'm working on something like that,i sent you two images that both of them are kind of peristaltic pump,i want to rotate two/one small cylinder about z axis,i should write an udf,i've written an udf for this but does not work;I will be thankful if you could help me out
looking forward to ur help.
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Old   August 3, 2010, 02:14
Default rotation about z axis
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sorry I forgot to attach images;
Attached Images
File Type: jpg 1.JPG (68.2 KB, 98 views)
File Type: jpg 2.JPG (79.1 KB, 65 views)
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Old   August 3, 2010, 02:17
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Balkrishna Patankar
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Yes write a UDF ... it will be simpler ... please attach the UDF ... or paste the code ....
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Old   August 3, 2010, 02:29
Default rotation about z axis
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dear balkrishna,it's kind of you to reply my post

i use the following udf

# include "udf.h"
# include "dynamesh_tools.h"
DEFINE_CG_MOTION(pump,dt,vel,omega,time,dtime)
{
Thread *t;

real freq_t;
NV_S(vel,=,0.0);
NV_S(omega,=,0.0);
if(!Data_Valid_P())
return;
freq_t = 4.0;
t= DT_THREAD((Dynamic_Thread*)dt);
vel[0] = 0.0;
vel[1] = 0.0;
vel [2] = 0.0;
omega [0] = 0.0;
omega [1] = 0.0;
omega [2] = freq_t;
}

in your opinion is that what i want,if yes what's the problem that it does not work,if not plz help me write an appropriate udf...
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Old   August 3, 2010, 02:31
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what doesnt work in this ... the udf is fine .... what are the errors you are getting ?
are you getting negative volumes in the mesh ? Also use cg_vel and cg_omega for the variables vel and omega .....
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Old   August 3, 2010, 02:34
Default rotation about z axis
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no i mean the small circle does not rotate about center of bigger circle,i have problem in motion!
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Old   August 3, 2010, 02:35
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yes ... i faced a similar problem .... use cg_vel instead of vel and cg_omega instead of omega
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Old   August 3, 2010, 02:39
Default rotation about z axis
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plz explain it more, how should i do it in udf,how can cg_vel rotate small circle about z axis???
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Old   August 3, 2010, 02:41
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try this udf ....
Code:
# include "udf.h"
# include "dynamesh_tools.h"
DEFINE_CG_MOTION(pump,dt,cg_vel,cg_omega,time,dtime)
{
    Thread *t; 

    real freq_t;
    NV_S(vel,=,0.0);
    NV_S(omega,=,0.0);
    if(!Data_Valid_P())
        return;
    freq_t = 4.0;
    t= DT_THREAD((Dynamic_Thread*)dt);
    cg_vel[0] = 0.0;
cg_vel[1] = 0.0;
    cg_vel [2] = 0.0;
    cg_omega [0] = 0.0;
    cg_omega [1] = 0.0;
    cg_omega [2] = freq_t;
}
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Old   August 3, 2010, 02:54
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Balkrishna Patankar
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yes it can ....
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Old   August 3, 2010, 03:50
Default rotation about z axis
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dear balkrishna...
i compiled ur udf and three images that i sent u are results,as u can see small cylinder changes its position so small, i want to move center of the cylinder on the inner edge of bigger cylinder,how can i do this large displacement??
Attachment 4299

Attachment 4300

http://www.4shared.com/file/R2SbkdqT...ltic-pump.html
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Old   August 3, 2010, 03:55
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i have dans guardian banning the attachment download .... read the documentation for larger displacement .... ....
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Old   August 3, 2010, 06:08
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i did not understand ur post,i had another post in mind
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Old   August 3, 2010, 06:10
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Balkrishna Patankar
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check the fluent docs ....
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Old   November 1, 2012, 10:20
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hi,

I am trying to move a 2d cylinder in y direction by using UDF:-
# include "udf.h"
# include "dynamesh_tools.h"
DEFINE_CG_MOTION(pump,dt,cg_vel,cg_omega,time,dtim e)
{
Thread *t;
real freq_t;
NV_S(cg_vel,=,0.0);

if(!Data_Valid_P())
return;
freq_t = 0.01;
t= DT_THREAD((Dynamic_Thread*)dt);
cg_vel[0] = 0.0;
cg_vel[1] = freq_t;

}

But I am having a problem while compiling it in Visual Studio Command Prompt. While executing nmake command to compile an error is appearing which is saying NMAKE : fatal error U1077: "sed" :return code '0X1'

can anybody tell how to eliminate this error????

Thank You

Regards

Vidit Sharma
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Old   November 1, 2012, 10:34
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try interpreting it .... do not compile it.
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Old   November 1, 2012, 10:41
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Quote:
Originally Posted by balkrishna View Post
try interpreting it .... do not compile it.
Dear Sir,

I tried to interprete it but it says "line8: structure reference not implemented"
Fluent user guide also says to compile the moving mesh macros.

Thank You,

regards
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Old   April 13, 2016, 04:16
Default flapping wings
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mohamed
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I am doing a CFD analysis of flapping wing motion in FLUENT and I need udf code to define the motion I do not know how to write it can any one help me with it thanks
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Old   April 13, 2016, 15:42
Default CFD udf code fluent
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[QUOTE=moh_zain;594803]I am doing a CFD analysis of flapping wing motion in FLUENT and I need udf code to define the motion I do not know how to write it can any one help me with it thanks
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