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Define time step size with max or min of Temp in a domain

Hi cfd-online

I have a very very sensible unsteady simulation and it must run with small time step size.

I want to use DEFINE_DELTAT and set Deltat function of some cell variable in a domain.

for example
if max Temp < T1 then Deltat=a
if max Temp >= T1 then Deltat=b
if max Liquid fraction > 0 then Deltat=c
.
.
.

is it possible to do that?

I think "Looping Over Cell Threads in a Domain (thread_loop_c)" can help me if I use that in DEFINE_DELTAT macro.

thank you

my udf is:

Red number is line number in udf commands .

Code:

DEFINE_DELTAT(mydeltat, domain)

{

        real time_step;

        real T_max=0.0 ;

        real T1=303.0 ;

        real T2=300.5 ;

        real T3=304.0 ;

        Thread t;

    cell_t c;

54        thread_loop_c(t,domain)

        {

56                begin_c_loop(c,t)

                {

58                        temp = C_T(c,t);

                        if (temp > T_max || T_max == 0.0) T_max = temp;

                }

                end_c_loop(c,t)

        }

        if (T_max < T1) time_step = 1.0;

        else time_step = 0.00001;

        return time_step;

}

error after build in compiler window:

Done.

(chdir "libudf")(chdir "win64\2ddp")# Generating ud_io1.h
Paper_PCM_Prop_and_DeltaT_v2.c
..\..\src\Paper_PCM_Prop_and_DeltaT_v2.c(54) : error C2440: '=' : cannot convert from 'thread_struct *' to 'Thread'
..\..\src\Paper_PCM_Prop_and_DeltaT_v2.c(54) : error C2088: '!=' : illegal for struct
..\..\src\Paper_PCM_Prop_and_DeltaT_v2.c(54) : error C2232: '->next' : left operand has 'struct' type, use '.'
..\..\src\Paper_PCM_Prop_and_DeltaT_v2.c(56) : error C2232: '->nelements' : left operand has 'struct' type, use '.'
..\..\src\Paper_PCM_Prop_and_DeltaT_v2.c(58) : error C2232: '->storage' : left operand has 'struct' type, use '.'

Done.

whats wrong in udf?

Instead of making "t" a thread variable, in

Code:

Thread t;

you should make it a pointer to a thread variable:

Code:

Thread *t;