# UDF for moving wall (oscillating)

 Register Blogs Members List Search Today's Posts Mark Forums Read 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: 5 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=-2; } end_f_loop(f,t) } T Thanks for reading   March 1, 2018, 04:12 #2 Senior Member   Join Date: Nov 2013 Posts: 1,915 Rep Power: 23 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
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SAMBHU JAYACHANDRAN
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 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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 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 = 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.  Thread Tools Search this Thread Show Printable Version Email this Page Search this Thread: Advanced Search Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules Similar Threads Thread Thread Starter Forum Replies Last Post DF15 Fluent UDF and Scheme Programming 33 August 20, 2020 13:36 Sanyo CFX 17 August 15, 2015 06:20 hinca CFX 15 January 26, 2014 17:11 Robert Fluent UDF and Scheme Programming 2 July 31, 2013 08:34 Kiran FLUENT 0 July 31, 2008 08:31

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