[SarahG]

Hello,

I have attempted to write a UDF, below, which needs to do as the comment in the header says. The model is an aerofoil with a small 'slot' where a 'pressure-outlet' boundary condition is designated.

When I tested it, it didn't compile; the error says 'XtGrabPointer failed'. I think there need to be three statements in the 'for'. Although I seem to remember reading that you can get by with only two statements, and neglect the last one, so long as you keep the semicolon for the first two. Can somebody please verify this??

Also, can anybody please hint as to a better way of structuring this? Perhaps different kinds of loops..

I am (obviously) a novice in C, I'm afraid, so any feedback will be much appreciated.

/* alpha cycles upwards then downwards in angle of attack between 3 and 8 degrees. A pressure ejection must begin at ~5 degrees while alpha is decreasing, and finish at ~3 degrees while still decreasing, like an on-off switch. This matches a half square wave with phase delay of -2pi/3*/

#include "udf.h"
#define PI 3.14159

DEFINE_PROFILE(blowing, thread, position)
{
face_t f;
begin_f_loop(f, thread)
{
real period = 12.08305;
real t = CURRENT_TIME;
real alpha;
int n=0;

for(alpha = (5.5+2.5*sin(0.52*t)); t<=(n+1)*period; )
{
if(t<=(n+1)*period)
{

if(((2*n+1)*(period/2)<=t<=(n+1)*period) && (5.0584>=alpha>=3.0392) )
{
F_PROFILE(f, thread, position) = 0.5;
}
else
{
F_PROFILE(f, thread, position) = 0;
}

}
else
{
n += 1; /*if t>(n+1)*period, increment integer counter by 1 before going further*/
}
/* still in the body of the for, so back to first if?- sarah does not understand*/
}


}
end_f_loop(f, thread)
}

[pakk]

'XtGrabPointer failed'

This does not really look like a compiler error... Can you show exactly how this error is showing on your screen?