Time step limited by chemical time-scale
 

While running my engine simulation into Converge, I noticed that the time step gets limited by the chemical time-scale. The default time-step is 1e-8 s and chemical time-scale 0.5.

Even by reducing the time-step to 1e-9 and chemical time-scale to 0.1 while the simulation is running doesn't help getting out of this issue.

Increasing the chemical time-scale helps, but what does that mean exactly, and what should I change to avoid that happening in the first place?

Thanks! :)

Hello Matt,


In CONVERGE, we limit the amount of energy added (or temperature increase) over a time step due to combustion. The parameter mult_dt_chem is used to control the time step size allowed by combustion.


https://mail.google.com/mail/u/0?ui=...d=ii_k5grsyjx0


dt<= (dt_previous * mult_dt_chem)/max(deltaT/T)



Generally speaking, you should not be hitting time step limit by combustion unless you are using very large cell sizes or there is something odd about the mechanism. For recommended grid sizes, please take a look at one of the example cases provided in CONVERGE STUDIO that is closest representation to your engine.

Hi Nitesh,

Thank you for your answer. I think the issue may be that I use the default grid size of 4mm, so I will try to reduce it and see what happens. Issue is that it already takes 8 days for a simulation to complete, but I'll see.

Thanks!