It's applied to the mixture. I could compute the PLI using the formula but I am not sure on the value of time to use because the simulation is steady state.
However, I have run the same simulation without the multiphase model and those huge spikes are gone:
The final values of the UDS do not change between the two simulations though, for example for the avg scalar 0 I get this with the multiphase model:
And this is from the simulation without multiphase model:
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