Hi, can anybody tell me how the non dimensional timestep is calculated? What does it mean by non dimensional timestep of delt=0.004 or else?

Hi,

Where do you get a non-dimensional timestep? CFX uses dimensional timesteps.

Glenn Horrocks

Hi Glenn,

Thanks.

I know that Cfx uses dimensional timesteps. But, from some literature, I found that they used non dimensional timesteps and I wanna compare my used timesteps in cfx(dimensional) with their non dimensional timesteps. Thats why I wannna convert this dimensional timesteps to non dimensional timesteps.

The 'non-dimensionalisation' of a problem, and hence the calculation of a non-dimensional timestep is 100% problem dependent. There is no general rule.

It might be related to (typical length)/(typical speed), but it might also be based on a diffusion timescale, or a number of other possibilities.

You will need to look at the literature you are interested in and see if that describes the choice of timestep used by the authors. If it does not, then you may have to contact the authors directly.

So, unfortunately we cannot give you an answer.

Good luck, Andy

Hi,

In addition to what Andy said, you can always convert the dimensional timestep reported by CFX to a non-dimensional timestep simply by applying the non-dimensionalisation for the time variable. Most non-dimensional schemes generate some form of reference time, then the non-dimensional timestep is simply dimensional timestep/reference time.

Glenn Horrocks