# USING IF statement in a UDF for defining Velocity profile at Inlet

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 July 19, 2012, 16:35 USING IF statement in a UDF for defining Velocity profile at Inlet #1 Member   Join Date: May 2009 Posts: 58 Rep Power: 9 Hi, I want to define a velocity profile at my inlet boundary condition. This is my UDF which is working for parabolic velocity, but I want to add a function for y<0.003 and another one for y>0.004, so I need to define and if statement. but UDF does not underestand y in the line (If y<0.003). How could I define y in my IF statement? Thanks. #include "udf.h" DEFINE_PROFILE(inlet_x_velocity, thread, position) { real x[ND_ND]; real y, v; face_t f; begin_f_loop(f,thread) { F_CENTROID(x, f, thread); y = x[1]; If (y<0.003) v= -228.*y+11.6; else v=-10200.*y+41.52 F_PROFILE(f, thread, position)=v; } end_f_loop(f, thread) }

 July 19, 2012, 17:04 #2 Senior Member     Alex Join Date: Jun 2012 Location: Germany Posts: 1,309 Rep Power: 22 Very strange. I can't see any error. But instead of assigning the value of x[1] to the variable y, you could try using x[1] directly in the if-statement and the equation.

July 19, 2012, 17:09
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Join Date: May 2009
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Quote:
 Originally Posted by flotus1 Very strange. I can't see any error. But instead of assigning the value of x[1] to the variable y, you could try using x[1] directly in the if-statement and the equation.
Thank you for your reply,

I tried that before, did not work.

It gave me an error indicating that the undeclared variable in IF statement.
Does it underestand the y variable in If statement?

 May 23, 2013, 23:46 #4 Member   Anonymous Join Date: Apr 2013 Posts: 34 Rep Power: 5 Hey Amir, I am facing the same problem. My UDF doesn't understand the if statement. How did you fix your problem?

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