Learning Forum

[keunsoo2]

Hello,

I would like to cell initialization using UDF. I am trying to make a model for shock-tube.

Geometry is 2D rectangular (1m * x cm). and I want to initialize the cell as the following

-Left 30% (Driver section): 20bar, (30% N2 and 70% He)

-Right 70% (Driven section):1 bar, 100% Air

 

I looked over the UDF manual, but I am not sure how to set a mixture.

The following is the UDF that I made.

I used centroid and loop function to define pressure of each side of the cell.

 

#include "udf.h"

DEFINE_INIT(ks_shock_tube_init,d)

{

   cell_t c;

   Thread *t;

   real xc[ND_ND];

   

   thread_loop_c(t,d)

   {

      /* loop over all cells */

      begin_c_loop_all(c,t)

      {

         C_CENTROID(xc,c,t);

         if (xc[0] < 0.3 )

         {

            C_P(c,t) = 2000000.;

         }

         else

         {

            C_P(c,t) = 100000.;

         }

      }

      end_c_loop_all(c,t)

   }

} 

 

Would someone help me define the mixture and property for the cell?

 

Thanks,

Keunsoo

[Rob]

You're looking for a species macro, there are a few examples in the UDF manual. 

To add, I'd also suggest looking up the Patch operation as part of initialisation: there's no need for a UDF here unless you really like writing code. 

[keunsoo2]

Thanks for your suggestion.

I am trying to initialize with Patch and it looks good now.

Would you give me a specific example to initialize two different gas conditions with a species macro?

I am not sure which one is related to my problem.

[DrAmine]

Please check the Cell Macros form the Customization Manual.

[keunsoo2]

Still I don't know which one is proper for my case.

Would you let me know exact section number?and It would be helpful if you have an example.

 

I have another question.

According to other papers, it looks like shock-tube modeling is feasible with Fluent.
Do you have a shock-tube tutorial or example?

[DrAmine]

No we do not have official tutorial for that.
Again check the customization manual and look after C_YI.
Again you do not require UDF for patching. Possible with inbuilt features.