I am modeling a system of multi-crystal silicon growth. I disabled the flow equation to solve only the energy one, starting from an clear solid-melt interface and I found during the crystal growth, the melt temperature goes to the melting point and so the whole melt gives out latent heat at the same time and results an wide liquid-solid mushy zone as well as an obscure solid-melt interface. That is not right for reality. anybody know how to fix it? my settings of liquidius and solidus temperature are same, the material is pure silicon, but that does not seem to work.

Hi,

Is it czochralski crystal growth?

no, it is DSS furnace

Try to set one temp for solid and let say 0.001 K more for liquid ... maybe this will help

R u modeling it in steady state or transient?

Transient, the steady state will never reach even in physics consideration. there is no use setting delta T to 0.00001. I have tossed the model and write my own udf and, tackled the problem.

By steady state I mean looking at a perticular instant.

Would be interesting to know how u tossed the model and written your own UDF

Yes, I agree it would be better to see what you have already estimated? If you could post your udf then it would be more clear what we are talking about.

below is my udf. the hypothesis is, the temperature gradient in melt is very small. I neglect the fluid flow and set a large thermal conductivity above the melt point.

#include "udf.h" #include "mem.h" #define Enthalpy 1317507.48 #define Latent_heat 72368.3 #define ID 8 static int last_ts = -1; /* Global variable. Time step is never <0 */ DEFINE_ADJUST(my_adjust5,d) { cell_t c,C0,C1; Thread *tf; Thread *t = Lookup_Thread(d,ID); int curr_ts,n,allow; face_t f; curr_ts = N_TIME; if (last_ts != curr_ts)

{

last_ts = curr_ts;

/* things to be done only on first iteration of each time step

can be put here */

begin_c_loop(c,t)

{

/*分辨是å�¦æœ‰æ–°çš„液ä½"å�•å…ƒï¿½ï¿½ 入到固液界é�¢ï¼Œ0表示液ä½"，1表示固ä½" ，2表示界é�¢*/

if(C_H(c,t)<=Enthalpy-100 && C_UDMI(c,t,0)==0)

{

/*Message("New boundary: C_H=%f,C_T=%f\n",C_H(c,t),C_T(c,t));*/

allow=0;

c_face_loop(c,t,n)

{

f = C_FACE(c,t,n);

tf = C_FACE_THREAD(c,t,n);

C0=F_C0(f,tf);

C1=F_C1(f,tf);

if(C0==c)

{

if(C_UDMI(C1,t,0)==1)

{allow=1;}

}

else

{

if(C_UDMI(C0,t,0)==1)

{allow=1;}

}

}

if(allow==1)

{

C_UDMI(c,t,0) = 2;

C_UDMI(c,t,1) = Latent_heat;

}

}

if(C_H(c,t)>Enthalpy+10 && C_UDMI(c,t,0)==1)

{

C_UDMI(c,t,0) = 2;

C_UDMI(c,t,1) = 0;

}

/*handle latent heat, 决定是��退出界�*/

if(C_UDMI(c,t,0)==2)

{

if(C_UDMI(c,t,1)>Latent_heat+100)

{C_UDMI(c,t,0)=0;}

if(C_UDMI(c,t,1)<-10)

{C_UDMI(c,t,0)=1;}

if(C_UDMI(c,t,1)>=0 && C_UDMI(c,t,1)<=Latent_heat)

{

C_UDMI(c,t,1)+=C_H(c,t)-Enthalpy;

Message("the enthalpy is %f\n",C_H(c,t));

}

}

}

end_c_loop(c,t)

}

begin_c_loop(c,t) {

/*handle latent heat, 决定是��退出界�*/

if(C_UDMI(c,t,0)==2)

{

C_H(c,t)=Enthalpy;

C_T(c,t)=1685;

} } end_c_loop(c,t) /*printf("%f\n",temppp);*/ }

/***********************************************/

DEFINE_ON_DEMAND(init_udm) {

Domain *d; /* declare domain pointer since it is not passed as an

argument to the DEFINE macro */

Thread *t;

Thread *tr;

cell_t c;

d = Get_Domain(1); /* Get the domain using Fluent utility */

tr = Lookup_Thread(d,ID);

/* Loop over all cell threads in the domain */

thread_loop_c(t,d)

{

begin_c_loop(c,t)

{

C_UDMI(c,t,0) = 0;

C_UDMI(c,t,1) = 0;

if(t==tr)

{

if(C_T(c,t)>1684.5 && C_T(c,t)<1685.5)

{

C_UDMI(c,t,0) = 2;

C_UDMI(c,t,1) = Latent_heat;

}

else

{

if(C_T(c,t)<=1684.5)

{C_UDMI(c,t,0) = 1;}

}

}

}

end_c_loop(c,t)

}

/* begin_c_loop(c,tr)

{

if(C_T(c,tr)>1684.6 && C_T(c,tr)<1685.4)

{C_UDMI(c,tr,1) = Latent_heat;}

}

end_c_loop(c,tr) */

}