Advice on Physical Timescale

Oli

Hi,

I am running a simulation looking at the dispersion of a gas ejected at high speed normal to a wall. I am wondering what is the best approach for setting the physical timescale.

While the domain is large (200 - 300m edge dimension) the length from the jet to the wall it impacts is just 10m. The jet exit velocity is approximately 60 m/s, so the timescale involved for the impingement is small. However, if I base the physical timescale on this, it will take a very long time to model the dispersion throughout the much larger domain.

I have initially set the simulation using a local timescale factor of 5, just to get it started. However, I obviously want to change back to a physical timescale before the simulation finishes. Should I base this on the impinging jet, something like (crudely) 10/60?

Many thanks in advance for your advice.

Oli