- **Fluent UDF and Scheme Programming**
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- - **(??) sinusoidal motion for DEFINE_CG_MOTION**
(*https://www.cfd-online.com/Forums/fluent-udf/81821-sinusoidal-motion-define_cg_motion.html*)

(??) sinusoidal motion for DEFINE_CG_MOTIONI'm testing with a simple UDF for sinusoidal angular velocity motion but it has a problem.
macro [DEFINE_CG_MOTION] presents [omega] for angular velocity variable and [time] to passes time variable, so try this to describe a pseudo-vibrating cantilever. omega is time dependant variable and displacement(angle) is intergation of the omega over the time passed. so I assumed if I put some intergand of the time into UDF, Fluent will reflect its integration to the moving boundary. Few graphs were ploted for investigation http://yfrog.com/51graphbj(http://yfrog.com/51graphbj) and equations are... w_1=sin(2*pi*t) F_1 = INTEGRAL(w_1, t) w_2=sin(2*pi*t + pi/2) F_2 = INTEGRAL(w_2, t) w_3=sin(2*pi*t - pi/2) F_3 = INTEGRAL(w_3, t) I choosed blue one(w_2) and its UDF code were... DEFINE_CG_MOTION(move, dt, vel, omega, time, dtime) { NV_S(vel, =, 0.0); NV_S(omega, =, 0.0); omega[2]=sin(2*M_PI*time + M_PI/2); } my desired output was correct y position of lever though, it only moves over y=0 but y>0 and vise versa (no alternation of -+. just up and down under y=0 or over y=0). I have no idea for [dtime] and [accumulater+= valiable] form to the that situation. So I put integrand in the UDF and hope the Fluent updates position of that intergrand for the time, but it seemed not that explictly :( SO... It seems obiously there are stupid assumption or mis-understanding of UDF. Can I recieve a wise solution? |

First of all, I don't see why F_1 is always positive in your picture (http://yfrog.com/51graphbj).
If angular velocity is: 1. then the integral of it should be: which alternates between 2. then the integral of it should be: which again alternates between My suggestion is to check around which origing you define this omega! |

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