# Pitch Ramp Motion for 2D Airfoil through UDF

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 April 28, 2010, 14:14 Pitch Ramp Motion for 2D Airfoil through UDF #1 Senior Member   aerospain Join Date: Sep 2009 Location: Madrid, Spain Posts: 125 Rep Power: 9 Hi everyone, I would like to define a ramp function for a 2D airfoil's pitch motion in FLUENT 12.1. I know how to do this with UDFs since I've already done it for a sinusoidal function. I just need to change the function, simplesss! My questions are the following: How do I stop the airfoil at a given angle of attack and leave it at that attitude? The catch is that I would like the calculation to keep running for some time at the final angle. Can I use conditional instructions in the UDF? In that case, what would be the "flag" for the yes/no condition? or, How could I do it by "Calculation Activities"? I'm assuming the activity I should define is the Steady or Transient mode at the time/iteration step the airfoil reaches the final angle. Thanks in advance cheers!

 April 28, 2010, 15:41 #2 Senior Member   Jouke de Baar Join Date: Oct 2009 Posts: 125 Rep Power: 8 I think you can use MIN and MAX. You could youse this for your time? Something like: angle = 0.5 * MIN(time,1) would increase the angle from 0 at t=0 to 0.5 at t=1 and then stay at 0.5 for the remaining time.

 April 28, 2010, 16:55 #3 Senior Member   aerospain Join Date: Sep 2009 Location: Madrid, Spain Posts: 125 Rep Power: 9 Thank you Jouke, I'm glad there are implicit functions for logical operations. From the way of defining the angle, I'm assuming the numerical stability of the calculation will depend directly on the physical time step (which is defined inside FLUENT12.1). I could always use another variable instead of time and use the latter to calculate the value of this new variable. I'll work on it. Thanks again

 July 30, 2010, 11:48 rotation about z axis #4 Member   ahmad Join Date: Jul 2010 Posts: 57 Rep Power: 8 hi everybody... guys if you are familiar with udf could u help me with this problem,i am trying to simulate peristaltic pump and for this i need to write an udf file to rotate on of edges about z axis,i will be thanfull if u could help me with this problem. thank you in advance..

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