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groovyBC and probe problem, needing your help!

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Old   April 14, 2010, 04:27
Default groovyBC and probe problem, needing your help!
  #1
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I am simulating the synthetic jet on NACA 0015 airfoil.
so I have a suction/blowing type boundary condition, and a prescribed velocity distribution is imposed at the boundary:
y=47.95*sin(2*pi*50*time). It's normal to the patch.
I have a groobyBC type boundary condition in my ./0/U, the code is
Code:
jet// the patch name
    {
    	type		groovyBC;
	valueExpression		"47.95*sin(2.0*pi*50*time())*normal()";
	value		uniform (0 0 0);
    }
Meanwhile, I have a probe code in system/controlDict, here it is
Code:
functions 
( 
probes1
    	{
        // Type of functionObject
       		type probes;
		log	true;
		outputControl timeStep;
		outputInterval 1;

        // Where to load it from (if not already in solver)
        functionObjectLibs ("libsampling.so");

        probeLocations
        (
            (0.045 0.02338 0.01875)// the point near the patch
        );
Now, the problem is magnitude of the velocity vector is far greater than 47.95, some of the vector is
Code:
 
//time Ux Uy Uz
0.04486             (79.4339 -16.8528 -3.46622e-21)
      0.04488             (77.6659 -15.7305 -4.04792e-21)
       0.0449             (75.7184 -14.4926 -4.59096e-21)
      0.04492             (73.599 -13.1451 -5.092e-21)
      0.04494             (71.3162 -11.6939 -5.54669e-21)
      0.04496             (68.8783 -10.1458 -5.9491e-21)
      0.04498             (66.2938 -8.50744 -6.29237e-21)
        0.045             (63.5716 -6.78616 -6.57194e-21)
      0.04502             (60.7203 -4.98953 -6.77717e-21)
      0.04504             (57.7497 -3.12517 -6.89967e-21)
      0.04506             (54.6711 -1.19994 -6.92882e-21)
      0.04508             (51.4999 0.781713 -6.85615e-21)
       0.0451             (48.2558 2.81933 -6.68789e-21)
      0.04512             (44.9628 4.91865 -6.43502e-21)
I have no idea about the error!! Please help me !
Any hints very much appreciated!
Regards
wwbbit
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Old   April 14, 2010, 12:38
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Bernhard Gschaider
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Quote:
Originally Posted by wwbbit View Post
I am simulating the synthetic jet on NACA 0015 airfoil.
so I have a suction/blowing type boundary condition, and a prescribed velocity distribution is imposed at the boundary:
y=47.95*sin(2*pi*50*time). It's normal to the patch.
I have a groobyBC type boundary condition in my ./0/U, the code is
Code:
jet// the patch name
    {
        type        groovyBC;
    valueExpression        "47.95*sin(2.0*pi*50*time())*normal()";
    value        uniform (0 0 0);
    }
Meanwhile, I have a probe code in system/controlDict, here it is
Code:
functions 
( 
probes1
        {
        // Type of functionObject
               type probes;
        log    true;
        outputControl timeStep;
        outputInterval 1;

        // Where to load it from (if not already in solver)
        functionObjectLibs ("libsampling.so");

        probeLocations
        (
            (0.045 0.02338 0.01875)// the point near the patch
        );
Now, the problem is magnitude of the velocity vector is far greater than 47.95, some of the vector is
Code:
 
//time Ux Uy Uz
0.04486             (79.4339 -16.8528 -3.46622e-21)
      0.04488             (77.6659 -15.7305 -4.04792e-21)
       0.0449             (75.7184 -14.4926 -4.59096e-21)
      0.04492             (73.599 -13.1451 -5.092e-21)
      0.04494             (71.3162 -11.6939 -5.54669e-21)
      0.04496             (68.8783 -10.1458 -5.9491e-21)
      0.04498             (66.2938 -8.50744 -6.29237e-21)
        0.045             (63.5716 -6.78616 -6.57194e-21)
      0.04502             (60.7203 -4.98953 -6.77717e-21)
      0.04504             (57.7497 -3.12517 -6.89967e-21)
      0.04506             (54.6711 -1.19994 -6.92882e-21)
      0.04508             (51.4999 0.781713 -6.85615e-21)
       0.0451             (48.2558 2.81933 -6.68789e-21)
      0.04512             (44.9628 4.91865 -6.43502e-21)
I have no idea about the error!! Please help me !
Any hints very much appreciated!
Regards
wwbbit
I'd be pretty surprised if this was a problem of groovy per se. Adjust the writeTime to get data written out at t=0.045 (or earlier) and inspect it. Have a look at the U file and look for the jet-patch. It has the current value of the expression (which should be in the expected range).

Then look at the result in paraview (cell values!!!!).
I'm suspecting:
- a problem with the other boundary conditions
- an interpolation problem
For all these I deny all responsibility

Bernhard
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Old   April 15, 2010, 02:15
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Does the vector normal() generally have the length 1 ?
For a test I would replace normal() with normal() / mag(normal()) .
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Old   April 15, 2010, 04:23
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Thanks for your all quick reply!
I'll have try!
I'll post the result as soon as i get it.
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Old   April 17, 2010, 00:31
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Hi,Bernhard!
I think you are right!
With the utility of patchAverage, I found the magnititude of velocity is right now. Although the point (0.045 0.02338 0.01875) is near the patch, the velocity is not right of the jet patch with the effect of other patch.
It's not the groovy and probes problem.
Now everything is going well!
Thanks!
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