[macfly]

In UDF Manual 15.0 example 2.7.4.3 there is a line to retrieve the value of a scalar at previous time step:

phi_old = C_STORAGE_R(c,t,SV_UDSI_M1(i));

Couldn't we just do this instead:

phi_old = C_UDSI_M1(c,t,i);

[franzdrs]

Hi,
I am wondering exactly the same. Did you found out if both options are equivalent?

Thanks

Franz

Originally Posted by macfly

In UDF Manual 15.0 example 2.7.4.3 there is a line to retrieve the value of a scalar at previous time step:

phi_old = C_STORAGE_R(c,t,SV_UDSI_M1(i));

Couldn't we just do this instead:

phi_old = C_UDSI_M1(c,t,i);

[macfly]

In the end I didn't use any previous time step macro. Instead I preferred to store variables in user defined memories (C_UDMI), an alternative way to compare with previous time step(s).

[pakk]

In mem.h, the following line is found:

#define C_UDSI_M1(c,t,i)C_STORAGE_R(c,t,SV_UDSI_M1(i))

This shows that

phi_old = C_UDSI_M1(c,t,i);

is the same as

phi_old = C_STORAGE_R(c,t,SV_UDSI_M1(i));

So both options seem to be exactly the same. Until Fluent decides in a newer version to change the definition of C_UDSI_M1.

[saeed676]

Originally Posted by macfly

In UDF Manual 15.0 example 2.7.4.3 there is a line to retrieve the value of a scalar at previous time step:

phi_old = C_STORAGE_R(c,t,SV_UDSI_M1(i));

Couldn't we just do this instead:

phi_old = C_UDSI_M1(c,t,i);

Hi, I am beginner at using UDFs but I wonder maybe why not straight forward use this macro to calculate old value at previous timestep, suppose it's phi_old = temperature variable
phi_old = C_T_M1(c, t)

Thanks