# UDF & MDM

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 June 19, 2003, 08:28 UDF & MDM #1 paolo Guest   Posts: n/a Sponsored Links Hi all, can someone tell me why this udf doesn't work? I'using that to simulate an impuse shaped plunge velocity in time for a profile and I want to calculate the CL for the profile. the udf works when I use for qdot the function sinus. As soon as I use the exponential function fluent doesn't seem to understand it in the sense that the resulting CL is zero, so for him I'm inputting a zero amplitude velocity..... #include "udf.h" #include "dynamesh_tools.h" #include "stdio.h" #include "math.h" DEFINE_CG_MOTION(plunge, dt, vel, omega, time, dtime) { real pi; real Timp; real Amp; real qdot; Amp = 0.000088363; Amp = 0.0000088363; Timp = 0.08; pi = 3.145926; NV_S (vel, =, 0.0); NV_S (omega, =, 0.0); qdot = 0.0; /* if (time < 1*Timp) */ if (time == dtime) { qdot = Amp*exp(time); qdot = Amp*exp(-((time-Timp/2)/(0.1*Timp))*((time-Timp/2)/(0.1*Timp))); qdot = Amp*pi/Timp*sin(2*pi*time/Timp); qdot = Amp*exp(-pow((time-Timp/2)/(0.1*Timp),2)); qdot = 100*Amp; } else { qdot = 0.0; } vel[1]= qdot; }

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