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UDF for moving wall (oscillating)

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Old   March 1, 2018, 01:52
Post UDF for moving wall (oscillating)
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SAMBHU JAYACHANDRAN
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I have been doing a project on sloshing in tanks. In my experimental setup i am using a 'Shake Table Apparatus'.
so for making similar moving condition for my geometry in ansys fluent, i need to create an oscillating moving wall using a udf. I don't have much knowledge in making a udf.

I request you to kindly help me in making a udf for an oscillating wall.

Given below is the udf i had used so far, but its only giving motion along one direction. i got this udf from a video regarding "generating wawes in tank"

#include "udf.h"
#include "dynamesh_tools.h"
DEFINE_CG_MOTION(oscillate,dt,vel,omega,time,dtime )
{
Thread *t;
face_t f; /* define the variables */
t = DT_THREAD(dt);
begin_f_loop(f,t) /* loop over each face in the zone to create an array of data */
{
vel[0]=-2;
}
end_f_loop(f,t)
}


T

Thanks for reading
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Old   March 1, 2018, 04:12
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Here it moves in one direction because the UDF gives it a constant velocity of 2 m/s in negative y-direction.
You don't want a constant velocity. What velocity do you want?
(Please don't answer with "an oscillating", but make an equation.)

BTW: I don't think this is about not knowing how to make a UDF. This is about making a mathematical model for your problem. You should do that before you make code.
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Old   March 12, 2018, 01:00
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SAMBHU JAYACHANDRAN
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Quote:
Originally Posted by pakk View Post
Here it moves in one direction because the UDF gives it a constant velocity of 2 m/s in negative y-direction.
You don't want a constant velocity. What velocity do you want?
(Please don't answer with "an oscillating", but make an equation.)

BTW: I don't think this is about not knowing how to make a UDF. This is about making a mathematical model for your problem. You should do that before you make code.


Thanks for your answer sir..
So i need to find out a mathematical model for the moving object. Also if i wrote an equation, how can i give the input in the form of udf?
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Old   March 12, 2018, 03:23
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Quote:
Originally Posted by Sambhu.jayachandran View Post
Thanks for your answer sir..
So i need to find out a mathematical model for the moving object. Also if i wrote an equation, how can i give the input in the form of udf?
If your mathematical model gives an equation for the x-velocity as (for example)
Code:
v_x = 3 * time + 24 - 8 * sin(time/2)
Then you put that in the UDF as:

Code:
vel[0] = 3 * time + 24 - 8 * sin(time/2);
So you see that last step is not the biggest problem, and we can help with any small problems that you encounter. Getting the mathematical equation is the most work.
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