# acceleration profile

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 August 4, 2010, 02:32 acceleration profile #1 New Member   Andrè Hüllmann Join Date: Mar 2010 Posts: 10 Rep Power: 8 Hello, I really need a udf for a acceleration profile! The facts: 2sec acceleration with 0,5m/s 3sec constant velocity 2sec decelerate I don`t know how it works but I need it for my disseration! I`m so grateful for your help!!

 August 5, 2010, 04:57 #2 New Member   Andrè Hüllmann Join Date: Mar 2010 Posts: 10 Rep Power: 8 This ist my udf, but it do not works! Can anywhere tell me what is wrong with the udf? Please! #include DEFINE_PROFILE(unsteady_v, t, pos) { real time, velocity; real acceleration = 0.0835; face_t f; begin_f_loop(f, t) { time = RP_Get_Integer("time-step"); if( time <= 2) velocity = acceleration * time; F_PROFILE(f,t,pos) = velocity; if( time > 2) velocity = 2* acceleration; F_PROFILE(f,t,pos) = velocity; if( time > 5) velocity = -acceleration * time; F_PROFILE(f,t,pos) = velocity; } end_f_loop(f, t) }

 August 10, 2010, 03:18 #3 New Member   Andrè Hüllmann Join Date: Mar 2010 Posts: 10 Rep Power: 8 Hello, is there no one who can help me??? It is very important for me!

 August 10, 2010, 03:34 #4 Senior Member   Jouke de Baar Join Date: Oct 2009 Posts: 125 Rep Power: 9 Perhaps: if( time < 2.0) velocity = acceleration * time; F_PROFILE(f,t,pos) = velocity; else if( time < 5.0) velocity = 2.0* acceleration; F_PROFILE(f,t,pos) = velocity; else velocity = 2.0*acceleration - acceleration * (time-5.0); F_PROFILE(f,t,pos) = velocity; Last edited by jack1980; August 10, 2010 at 03:35. Reason: mistake in code

 August 10, 2010, 05:56 #5 Senior Member   Max Join Date: Mar 2009 Posts: 133 Rep Power: 9 "time" suggest that you want to retrieve the current flow time in seconds. RP_Get_Integer(time-step) returns the number of timesteps computed in your transient simulation so far. As long as your timestep size is not set to exactly 1s these two will not be equal. time = CURRENT_TIME will do the trick anyway. cheers

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