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-   -   moving mesh (http://www.cfd-online.com/Forums/fluent/36333-moving-mesh.html)

sulfi April 10, 2005 23:33

moving mesh
 
Dear friends,

could you tell me how to do the moving mesh analysis in fluent. my case is a planing craft, which should move up and down due to the dynamic pressure acting on it. Please send me any moving mesh tutorial which will help me doing the same.

thanking u sulfi

handou April 11, 2005 02:56

Re: moving mesh
 
you should use the dynamic mesh method. write a udf to describe your motion. do you have the FLUENT tutorial files? there is a example very similar to yours.

sulfi April 11, 2005 13:42

Re: moving mesh
 
handou thank u for ur reply

in fluents sliding mesh tutorials they are specifying the rotor motion velocity as the velocity of the mesh.

But i am simulating a planing craft which should move depending on the dynamic pressure acting on its bottom.

please help me doing the above problem.

send me if u have any other turorials of moving mesh

thanking u

handou April 12, 2005 08:36

Re: moving mesh
 
this is a example in the guide. hope it can help. #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 x-component of velocity */ vel[0] = v_prev; }

sulfi April 12, 2005 08:54

Re: moving mesh
 
thank u handou.

But i am not able to follow the uDF properly. can u send the whole example of the guide.so that i can solve that problem which may help me better understand how to set up a moving mesh problem and may help me to write the UDF. can u explain the UDF eloberately

handou April 12, 2005 09:32

Re: moving mesh
 
sorry, i never used this udf before. i just copy it from the help file for you. don't you have the udf help file? it's about 2MB big. can i send it to your email?

Shuto April 12, 2005 16:58

Re: moving mesh
 
I think this problem is quite difficult especially if you have no former experience with a dynamic mesh.

If the flow is going to drive the motion of the body you will need to incorporate feedback from the simulation into the udf.

I recommend that initially you write a very simple udf to produce linear motion. Once you have got that working then move on to incorporating flow effects.

Hope this helps, Shuto.

sulfi April 13, 2005 23:52

Re: moving mesh
 
Dear handou,

i havnt got the two files sent by you. file. when i downloaded the message came file corrupted. can u send it again.

Thanking u

sulfi


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