# UDF for moving wall (oscillating)

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 March 1, 2018, 01:52 UDF for moving wall (oscillating) #1 New Member   SAMBHU JAYACHANDRAN Join Date: Mar 2018 Location: KERALA, INDIA Posts: 4 Rep Power: 4 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

 March 1, 2018, 04:12 #2 Senior Member   Join Date: Nov 2013 Posts: 1,451 Rep Power: 20 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.

March 12, 2018, 01:00
#3
New Member

SAMBHU JAYACHANDRAN
Join Date: Mar 2018
Location: KERALA, INDIA
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Quote:
 Originally Posted by pakk 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.

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?

March 12, 2018, 03:23
#4
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Join Date: Nov 2013
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Quote:
 Originally Posted by Sambhu.jayachandran 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.