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question on UDF manual example

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Old   June 25, 2009, 12:58
Default question on UDF manual example
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Akour
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Hello everyone,

can anyone explain to me why C_UDSI_G is multiplied by the cell volume in the following UDF example? (in the udf manual, pasted below). Is this necessary if we want to write a scalar in terms of the derivative of another scalar?? i.e. say Ive got a UDS equation solving for some scalar H and another one solving for some scalar I, say a source term appears in the equation for scalar I, which is given by DH/DX...do i need to write this as C_VOLUME*C_UDSI_G(c,t,index of scalar H)?

Thanks for your help
AK


/************************************************** ******************
UDF for defining user-defined scalars and their gradients
************************************************** *******************/
#include "udf.h"
DEFINE_ADJUST(adjust_fcn,d)
{
Thread *t;
cell_t c;
real K_EL = 1.0;
/* Do nothing if gradient isn't allocated yet. */
if (! Data_Valid_P())
return;
thread_loop_c(t,d)
{
if (FLUID_THREAD_P(t))
{
begin_c_loop_all(c,t)
{
C_UDSI(c,t,1) +=
K_EL*NV_MAG2(C_UDSI_G(c,t,0))*C_VOLUME(c,t);
}
end_c_loop_all(c,t)
}
}
}
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