[rkadlof]

Hey,
I want to set boundary condition - sinusoidal pressure inlet at circle shape(2d).
I think my UDF is not correct, can you take a look?


#include "udf.h"

DEFINE_PROFILE(unsteady_pressure, thread, position)
{
face_t f;
real t = CURRENT_TIME;

begin_f_loop(f, thread)
{
F_PROFILE(f, thread, position) = 100 + 200*sin(500.* t);
}
end_f_loop(f, thread)
}

[pakk]

I don't know if it is correct, because I don't know what you exactly want. "sinusoidal pressure inlet", what does that mean? Something has a sinus-shape, but what? The pressure as function of time? The pressure as function of position?

Your code looks like the pressure is a function of time. Is that what you want?

And what makes you think that your UDF is not correct? Are the results not what you expect?

[rkadlof]

thank you for fast response ;-)

I want to model point (exactly it is the small circle in huge ambient) which is point-sound source. That's why I need to apply p(t) function. Sinusoidal would be the best.
I've read some UDF tutorials, but most of them were focused on inlet at pipe like a straight line(2d). Some mistakes i have made were connected with timestep size.
(but few question to left)
1. in eq. F_PROFILE(f, thread, position) = 500 + 300 * sin(500000.* t);

500 is some const
300 is an Amplitude
500000 would be "w" - omega (angular velo)?
correct?

[pakk]

If you use F_PROFILE(f, thread, position) = 500 + 300 * sin(500000.* t); the result is:

Average pressure is 500 Pa. (Gauge pressure, the absolute pressure depends on what you set as operating pressure.)
Minimum pressure is 500 Pa - 300 Pa = 200 Pa.
Maximum pressure is 500 Pa + 300 Pa = 800 Pa.
Every 2*pi seconds (6.28... s), there are 500000 "sine shapes".
In other words: your point has a frequency of 500000/2pi = 79.6 kHz. To resolve this, your time step needs to be in the order of microseconds.

[rkadlof]

I have realized that few minutes ago. Anyhow i really appreciate your response. That makes me sure of myself.

thank you Pakk