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acceleration profile

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Old   August 4, 2010, 02:32
Default acceleration profile
  #1
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Andrè Hüllmann
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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!!
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Old   August 5, 2010, 04:57
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Andrè Hüllmann
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This ist my udf, but it do not works! Can anywhere tell me what is wrong with the udf? Please!


#include <udf.h>
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)
}
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Old   August 10, 2010, 03:18
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Andrè Hüllmann
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Hello,
is there no one who can help me???

It is very important for me!
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Old   August 10, 2010, 03:34
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Jouke de Baar
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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
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Old   August 10, 2010, 05:56
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Max
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"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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