[Светлана]

Hello,

In ansys cfx there is 'air ideal gas' (fluid) and 'soot' (solid). How do I model a mixture of these two materials? I can specify the mass fraction of soot but I am seriously struggling to find the button for the 'mixture of fluid and solid' option, is it required to activate a particle model somewhere? If so, where? Please advise.

Regards,
Svetlana

[ghorrocks]

Have a look at the CFX tutorial examples. There are multiphase model examples of all the main types of flow, including solid particles like you are considering.

[Светлана]

Originally Posted by ghorrocks

Have a look at the CFX tutorial examples. There are multiphase model examples of all the main types of flow, including solid particles like you are considering.

I would like to model soot as a fluid, in an approximation. Just like I can model presence of any new gas.



This requires me to specify the dynamic viscosity, conductivity, and density.


I was able to find the density of soot particles in existing papers, and conductivity, but not the viscosity. Even as a function of particle size would be great to have.


For some reason this simplified approach does not appear to be included in existing literature.

[ghorrocks]

You can't model soot as a fluid as it is not a fluid.

You have three main options:
1) A Eularian particle phase
2) A Lagrangian particle phase
3) An additional variable, with convection and possibly diffusion.

Option 3 is by far the easiest, but really only allows you to track the motion of the soot. Option 1 is reasonably easy and allows additional physics like relative slip between the particles and the fluid. Option 2 is by far the hardest and most computationally expensive. It allows you to track the path of individual soot particles.

[Светлана]

Thanks, is there any example (paper or tutorial) about option 3, please? I could find energy source term for radiation of soot particles, but not the additional variable.