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Old   September 22, 2012, 09:15
Exclamation importance of CG motion
Aamer Shahzad
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Originally Posted by sheth View Post
Hey JG, I finally got it working. Thanks for all your help. The constants in equation were not the issue, even with the constants it went well. The wing just bends slightly so I think I need to set dynamic parameters so it doesn't happen.

For those who are trying here is what to follow:
1. Use Euler angles to define angles (Theta, Phi... etc in Euler Angles)
2. Orient Geometry As it shall be at time t=0.
3. In dynamic mesh, when you define dynamic zone, mention CG properly (Very IMP), In my case I wrote the Cg position x,y,z and I didn't mention the cg orientation when defining dynamic mesh zones.
4. Follow the order X, Y, and then Z, i.e. The first rotation will be about X axis, second will be about Y axis, and third will be about Z axis.
5. The UDF that JR has provided works perfectly, its in this thread itself, so many thanks to JG for that.
6. If your motion is not proper, then play with positive negative sign, I had to do this in my case also. Try changing signs of equations, and you may get proper motion.

hope you are doing fine. you wrote that mentioning CG position and orientation is important. Will you please tell how to give CG position and orientation correctly.
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Old   September 22, 2012, 10:55
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Will you please tell how to give CG position and orientation correctly.
I assume you are using DEFINE_CG_MOTION macro give motion to wing. In Dynamic Mesh zones when you define your wing as "Rigid Body" you also need to define CG location of wing which will be used as a reference point by the wing to perform the desired motion(as instructed to it by the UDF) say for example flapping motion around x-axis(chord axis) was desired for me I gave x and y coordinates of the CG location in CG position tab and wing used these coordinates as reference point to give desired motion, hope it helps you
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Old   March 3, 2014, 08:29
Default UDF FOR AN OSCILLATING FLAT PLATE (vertical oscillation)
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Hi all I am trying to write UDF for a flow over an oscillating flat plate. I have very very little knowledge of C++ so I am a novice, please I will need assistance from anybody that could help. After going through the Fluent Manual I believe I will need to write DEFINE CG_MOTION udf. Please I need your help. This is my personal email My major concern to write the udf for the plate oscillating along the y-axis


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Old   July 10, 2015, 15:05
Default 2d moving mesh for piston movement
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Kindly help me in writing the udf to move a piston profile inside a cylinder to determine the flow pattern and turbulence. Many thanks in advance..
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