[cfd_Matrix]

hi everyone,

i have to write UDF (unsteady model) for non-reversible changes in material density with temperature using DEFIN_PROPERTIES :

If T< Tcr (critical temperature), rho = 5.0 Kg/m3
else

If T>= Tcr , rho = 20 Kg/m3 and it keep this values even if the temperatures return below Tcr.

what change to make to take into account the non reversible change

Thanks in advance

DEFINE_PROPERTY(density, c, t)
{

real rho;
real temp;

temp = C_T(c, t);

C_CENTROID(r,c,t);

if(temp<600)
{
rho=5.0;

}

else
{
rho=20.0;
}

return rho;
}

[AlexanderZ]

#include "udf.h"

DEFINE_INIT(my_init_func,d)
{
	cell_t c;
	Thread *t;
	thread_loop_c(t,d)
	{
		begin_c_loop_all(c,t)
		{
			C_UDMI(c,t,0) = 0;
		}
		end_c_loop_all(c,t)
	}
}

DEFINE_PROPERTY(density, c, t)
{
	real rho;
	real temp;
	temp = C_T(c, t);
	if (temp<600) && (C_UDMI(c,t,0) < 1)
	{
		rho = 5.0;
	}
	else
	{
		rho = 20.0;
		C_UDMI(c,t,0) = 1;
	}
	return rho;
}

[cfd_Matrix]

thank you very much for help !

[cfd_Matrix]

Originally Posted by cfd_Matrix

thank you very much for help !

Dear sir, i hope this mail find you good , I am working on a two-phase (gas-liquid) flow problem using the VOF method. I need to calculate the vof gardient (both magnitude and three componants vector) to use them in define source terms, i'm using DEFINE_ADJUST to store vof gradient in UDMIS, but I get errors when interpreting th UDF , : Scalar_Reconstruction undeclared variable;

DEFINE_ADJUST(adjust_gradient_heat, domain)
{
Thread *t;
Thread **pt;
cell_t c;
int phase_domain_index = 1.0;
Domain *pDomain = DOMAIN_SUB_DOMAIN(domain,phase_domain_index);

{
Alloc_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_N ULL);
Scalar_Reconstruction(pDomain, SV_VOF,-1,SV_VOF_RG,NULL);
Scalar_Derivatives(pDomain,SV_VOF,-1,SV_VOF_G,SV_VOF_RG, Vof_Deriv_Accumulate);
}


mp_thread_loop_c(t,domain,pt)
if (FLUID_THREAD_P(t))
{
Thread *ppt = pt[phase_domain_index];
begin_c_loop (c,t)
{

C_UDMI(c,t,0) = C_VOF_G(c,ppt)[0];
C_UDMI(c,t,1) = C_VOF_G(c,ppt)[1];
C_UDMI(c,t,2) = C_VOF_G(c,ppt)[2];
C_UDMI(c,t,3) = sqrt(C_UDMI(c,t,0)*C_UDMI(c,t,0) + C_UDMI(c,t,1)*C_UDMI(c,t,1) + C_UDMI(c,t,2)*C_UDMI(c,t,2)); // magnitude of gradient of volume fraction
C_UDMI(c,t,4) = C_UDMI(c,t,0)/C_UDMI(c,t,3); // nx -> x gradient of volume fraction divided by magnitude of gradient of volume fraction
C_UDMI(c,t,5) = C_UDMI(c,t,1)/C_UDMI(c,t,3); // ny -> y gradient of volume fraction divided by magnitude of gradient of volume fraction
C_UDMI(c,t,6) = C_UDMI(c,t,2)/C_UDMI(c,t,3); // nz -> z gradient of volume fraction divided by magnitude of gradient of volume fraction
}
end_c_loop (c,t)
}
Free_Storage_Vars(pDomain,SV_VOF_RG,SV_VOF_G,SV_NU LL);
}

[AlexanderZ]

compile code

[cfd_Matrix]

Dear friend, i have quastion , What change i have to make to the UDF if it is a 2 phases VOF problem with air as primary phase and the second material (that undergoes non reversible density change) is the secondary phase. The non reversible change muste ocuure to the seonde phase only not air. thanks in advance.

[cfd_Matrix]

Originally Posted by cfd_Matrix

Dear friend, i have quastion , What change i have to make to the UDF if it is a 2 phases VOF problem with air as primary phase and the second material (that undergoes non reversible density change) is the secondary phase. The non reversible change muste ocuure to the seonde phase only not air. thanks in advance.

#include "udf.h"

DEFINE_INIT(my_init_func,d)
{
cell_t c;
Thread *t;
thread_loop_c(t,d)
{
begin_c_loop_all(c,t)
{
C_UDMI(c,t,0) = 0;
}
end_c_loop_all(c,t)
}
}

DEFINE_PROPERTY(density, c, t)
{
real rho;
real temp;
temp = C_T(c, t);
if (temp<600) && (C_UDMI(c,t,0) < 1)
{
rho = 5.0;
}
else
{
rho = 20.0;
C_UDMI(c,t,0) = 1;
}
return rho;
}