Learning Forum

[p.brosnan]

Hi,

I am using the SI and HCCI closed 0-D reactors models for engine combustion simulation. I am exporting the data to MATLAB for post-processing. I would like a fixed step solver instead of a variable step solver, so my sequence lengths are the same (step sizes range from 5.2E-05 to 5.4E-05 sec with the variable step solver) when imported into MATLAB. However, all I can change is the maximum step size; hence, my simulations have different sequence lengths. Can a fixed step solver (i.e., 5.0E-05 sec) be used in these Chemkin models?

[Judy Cooper]

Hi:

Unfortunately a variable timestep is what is generally used to run these types of problems, so the fixed option is unavailable.  Your best option is to set the initial and max step size the same and make both small enough that the timestep length is unlikely to fall below the level that is set.