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Passing point data to UDF using C_UDMI

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Old   November 17, 2005, 06:55
Default Passing point data to UDF using C_UDMI
  #1
Sam Bennett
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Dear all,

I have written the following code to load the temperature from a point (zone ID = 15) into the user defined memory.The point was created in Fluent using surace/point. When it's run as interpreted I get a segmentation violation. Yes I have turned on user memory. I have also tried looping over the face and using F_UDMI, same problem. The zone ID is from surface/manage, as a point isn't listed as a boundry. Is this where my problem comes from?

Thanks for your help in advance,

Sam

DEFINE_ADJUST(sensor_temp, domain)

{

cell_t c;

int ID = 15;

Thread *thread = Lookup_Thread(domain, ID);

begin_c_loop(c, thread)

{ C_UDMI(c,thread,0) = C_T(c,thread); }

end_c_loop(c, thread)

}
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Old   November 17, 2005, 07:49
Default Re: Passing point data to UDF using C_UDMI
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RoM
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You cant acces values from postprocessing surfaces in udf. Where did you get that thread id from? To get a list of all surfaces/cell zones you can access by udf type //define/bc/lz in tui.

RoM
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Old   November 22, 2005, 06:59
Default Re: Passing point data to UDF using C_UDMI
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Sam Bennett
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Dear RoM,

I got the zone ID from the manage surfaces panel, it doesn't show up on the list you get when you type in //define/bc/lz.So I probably can't use a "point" from Fluent.

Is there any other way of accesing temperature from a position not on a boundry condition?

Thanks, Sam
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Old   November 22, 2005, 08:12
Default Re: Passing point data to UDF using C_UDMI
  #4
RoM
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One possible way is to create a new fluid zone which holds only the cells you want to access. First you will need to mark these cells with the adapt->region panel. After you have marked your cells you can create a new fluid zone with grid->seperate->cells (save before). The new fluid zone is a boundary and will show up when you type //define/bc/lz. You can get its ID from there and use it in your udf. If you dont need the additional fluid zone anymore you can use grid->merge to merge it with your original fluid zone.

Good Luck, RoM
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Old   November 23, 2005, 11:50
Default Re: Passing point data to UDF using C_UDMI
  #5
Sam Bennett
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Hi RoM, thanks for your suggestion. I tried doing that but got a (SEGMENTATION VIOLATION), the same as when I tried using a point ID. Any more suggestions?
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Old   November 28, 2005, 02:50
Default Re: Passing point data to UDF using C_UDMI
  #6
RoM
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You can get the cell center corrdinates with the C_CENTROID macro and use it to pick the cells you want.

DEFINE_ADJUST(sensor_temp, domain)
{
cell_t c;
real c_cen[ND_ND]; /* cell center coordinates */
int ID = 15; /* fluid zone id */
Thread *thread = Lookup_Thread(domain, ID);

begin_c_loop(c, thread)
{
C_CENTROID(c_cen,c,thread); /* c_cen[0]=x, c_cen[1]=y, c_cen[2]=z */
if( /* pick cell, dependend on c_cen coords */ )
C_UDMI(c,thread,0) = C_T(c,thread);
else
C_UDMI(c,thread,0) = 0.;
}
end_c_loop(c, thread)
}

RoM
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Old   December 1, 2005, 09:46
Default Re: Passing point data to UDF using C_UDMI
  #7
Sam Bennett
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Thanks RoM, I've sorted it out using a the cell centroid firdt to find th cell, and then later just using the number directly.Thanks again.

Sam
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