[raz]

Hi all,

I was curious if somebody with more experience on the numerical side of things could enlighten me about the choice of time stepping schemes. I understand that second order will be more accurate but I how important is it when timesteps are already in the order of 10e-5 10e-6?

thanks

[LuckyTran]

You really shouldn't use 1st order. Always use 2nd order, or bounded 2nd order. There's really no reason not to use 2nd order. It's only a button click, and memory is cheap nowadays. The smaller your time-step, the more important it is to use a 2nd order time-stepping scheme because this is where the order of the method matters the most.

It really depends on your problem and whether the temporal characteristics is dominated by low of high frequency effects, this determines whether you can get away with 1st order vs 2nd order.

Assuming you are not just having fun and wasting compute hours (i.e. using extremely small time-steps for no reason), I'm guessing that you are using small time-steps because you have a lot of high frequency stuff that you need to resolve. In this case, you need 2nd order or you'll get inaccurate results.

If your problem was mostly low frequency, you could reasonably get away with 1st order as low frequency stuff is less affected by numerical dissipation.

[sina_mech]

Originally Posted by raz

Hi all,

I was curious if somebody with more experience on the numerical side of things could enlighten me about the choice of time stepping schemes. I understand that second order will be more accurate but I how important is it when timesteps are already in the order of 10e-5 10e-6?

thanks

Bounded 2nd order is a good choice with less oscillations, especially for compressible and/or multiphase problems. Like "LuckyTran" mentioned, I also never noticed a noticeable difference at the computational cost, and it's pretty much like first order!