[Tpozkar]

Hello prestigious community of CFD online,

I'm simulating transient combustion using the non-premixed model. When I made the normal calculation (no udf, constant flow rate), both mass and energy balances are low enough to consider their continuity.
However, when I use an UDF, which consists in pressure fluctuations at air inlet (flow rate changes with time), the energy imbalance increases. The higher the amplitude of pressure fluctuation at inlet the higher the energy imbalance (there is more heat incoming that going out). I get differences in heat between inlet and outlet up to 7%.
Is that a value too high to consider the calculation was wrong. Otherwise, what could be the reason of that imbalance of energy?
My mass balance still being low, only energy shows discrepancies.

Any help or advice will be highly appreciated.

[AlexanderZ]

Try to decrease timestep

Best regards