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January 16, 2013, 01:04 
lagrange gun UDF

#1 
New Member
mehdi
Join Date: Jan 2013
Posts: 3
Rep Power: 5 
I want to simulate a piston which move on the differential pressure force acting on its two surfaces.
The UDF tha I use is: /************************************************** ********** * 1degree of freedom equation of motion (xdirection) * compiled UDF ************************************************** **********/ #include "udf.h" static real v_prev = 0.0; DEFINE_CG_MOTION(piston,dt,vel,omega,time,dtime) { Thread *t; face_t f; real NV_VEC(A); real force, dv; /* reset velocities */ NV_S(vel, =, 0.0); NV_S(omega, =, 0.0); if (!Data_Valid_P()) return; /* get the thread pointer for which this motion is defined */ t = DT_THREAD(dt); /* compute pressure force on body by looping through all faces */ force = 0.0; begin_f_loop(f,t) { F_AREA(A,f,t); force += F_P(f,t) * NV_MAG(A); } end_f_loop(f,t) /* compute change in velocity, i.e., dv = F * dt / mass velocity update using explicit Euler formula */ dv = dtime * force / 50.0; v_prev += dv; Message ("time = %f, x_vel = %f, force = %f\n", time, v_prev, force); /* set xcomponent of velocity */ vel[0] = v_prev; } But it doesn't work. would you please help me? thanks. 

January 21, 2013, 09:42 

#2 
Senior Member
Marion
Join Date: Jul 2012
Location: France
Posts: 122
Rep Power: 7 
Hi,
Why don't you use the "Compute_Force_And_Moment" function for the calculation of the force? I've seen it in the 6DOF examples of the tutorials. Marion. 

January 22, 2013, 09:40 

#3  
Senior Member
Ehsan Asgari
Join Date: Apr 2010
Posts: 297
Rep Power: 9 
Quote:
What tutorial exactly do you refer?! I can't find it among Fluent tutorials. If you'd have such tutorial would you please send it to me?! Me Email is syavash_azna@yahoo.com Thank you 

January 23, 2013, 01:05 

#4  
New Member
mehdi
Join Date: Jan 2013
Posts: 3
Rep Power: 5 
Quote:
Dear Marion Would you please send me that axample? aydinkabir88@gmail.com thanks in advance. 

January 23, 2013, 15:32 

#5  
Senior Member
Daniele
Join Date: Oct 2010
Location: Italy
Posts: 992
Rep Power: 16 
Quote:
This is the same approach I proposed to you in private message. Daniele 

August 9, 2014, 00:34 

#6 
New Member
arash
Join Date: Aug 2014
Posts: 9
Rep Power: 4 
Hi everyone
I have been working on moving projectile in a barrel. I need udf for dynamic mesh(Six degree of freedom solver). can anyone help me? 

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