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-   -   Initialisation of UDS at t=0 (https://www.cfd-online.com/Forums/fluent/122508-initialisation-uds-t-0-a.html)

 moloykb August 21, 2013 06:54

Initialisation of UDS at t=0

Dear All,

I want to calculate the concentration contour, in the three fluid zone in a transient situation. For that I need to initialize concentration equal to 1 at zone 1 at t=0 whereas for zone 2,3 concentration is equal to 0 at t=0. I am using only 1 single UDS equation. How to implement this initial condition. Any help is highly appreciated.

 bigfootedrockmidget August 22, 2013 08:47

Find the fluid id's of the different zones, and then do something like this: copy,paste,build,load and set function hook.

Code:

```#define ID_FLUID_1 136 #define ID_FLUID_2 242 #define ID_FLUID_3 281 DEFINE_INIT(Set_start_conc,d){ cell_t c; Thread *t; double x[ND_ND];     t=Lookup_Thread(d,ID_FLUID_1); begin_c_loop(c,t){   C_UDSI(c,t,0) = 1.0 // value of user defined scalar 0    } end_c_loop(c,t)         t=Lookup_Thread(d,ID_FLUID_2); begin_c_loop(c,t){   C_UDSI(c,t,0) = 0.0;            } end_c_loop(c,t) t=Lookup_Thread(d,ID_FLUID_3); begin_c_loop(c,t){   C_UDSI(c,t,0) = 0.0;            } end_c_loop(c,t) }```

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