Learning Forum

[zdfrankman]

I am writing a UDF to have a source term only on the nodes that make up the walls. I was using this previously:

/******************************************************************
UDF that adds species source term to duct flow
*******************************************************************/

#include "udf.h"

#define CON .01

DEFINE_SOURCE(cell_x_source, cell, thread, dS, eqn)
{
  real source;

/******************************************************************
This loop checks if the cell has a near-zero velocity. If it does, it sets the source rate to the species concentration, mimicking a reaction
*******************************************************************/

  if (C_U(cell,thread) <= .000001)
  {
    source = C_YI(cell,thread, 1);

  }
  else
  {
    source =  0.;
  }

  return source;
}

 

 

 

However, the entire cell acts as a source. I would instead like for only the nodes that make up the wall to act as a source. How can I do that?

 

Thank you!

[Rob]

 

There’s not a source term for walls, so you will need to add material to the whole cell. I suggest looking at the cell loop options, using a low velocity may cause problems if you have a recirculation zone. You can set a species flux/concentration at the walls, will that do?

 

[zdfrankman]

Hello Rob,

 

A flux or source term will linearly add or subtract a species from the channel. I require a simulation to accurately model the concentration-dependent nature of a wall surface reaction.

 

Is there a way to perform a wall surface reaction that does not also permit wall surface species diffusion through the wall?

[Rob]

Where are you setting wall diffusion? 

[zdfrankman]

In the code I wrote, the channel walls are unchanged from normal settings, and therefore the Species -> Species Boundary Condition ->O2 and N2 are set to "Zero Diffusive Flux"

[Rob]

That's to let you disolve material off a wall as needed. 

[zdfrankman]

Understood!

 

Is there any way to prevent species diffusion through the wall during a wall surface reaction?