Learning Forum

[a.y.al-wardi]

I'm working on a multiphase simulation in Fluent where ozone is modeled as the secondary phase. I used UDF to model ozone decomposition using a simple first-order decay (shown in the picture below): 

It was expected that the negative source term would accelerate ozone decay, but surprisingly, the case with the UDF shows slower decay compared to running the same multiphase model without the UDF. 

This was also compared to a species transport simulation:

• With no reaction, decay is slower.

• With a built-in first-order reaction, decay is faster (as expected).

Given that I’m using the same rate constant (0.004) across all models; why is ozone decay slower with udf than without it in the multiphase model?

[Rob]

Which multiphase model are you using? How well converged is the solution? 

[a.y.al-wardi]

Multiphase mixture model. The solution is converged to below 1e-3. 

[Rob]

What's causing the decay otherwise? Are you removing phase and mass? 

[a.y.al-wardi]

Forced convection using a fan to remove the ozone from the chamber.