time step size.
 

In the unsteady convergence, can some one pls tell me how to correctly calculate the time step size?

I'd also would like to know how to monitor for convergence for unsteady problem.

thanks.

Sham.

Re: time step size.
 

Stability is the issue to be kept in mind. What kind of numerical scheme are you using.

-h

Re: time step size.
 

Depends also on what frequency of your model you want to describe...Luca

Re: time step size.
 

Thanks guys,

I am modelling a 2D pipeline on the seabed with a gap. This is to see the vortex shedding structure. I use an ske turbulence model.

Luca, I hope you can explain what do you mean what frequency of the model that I want to describe. I hope you guys can help me with this.

I'd really appreciate all the help.

Sham.

Re: time step size.
 

You can use the explicit scheme in which the time step is automatically calculated by the FLUENT to satisfy the stability conditions.

Sincerely,

Saad

Re: time step size.
 

The total time T=L/u, where L - length of your pipeline, u - inlet velocity. The pipeline length, for example 100m. In that case it is better to divited the length by 10000 parts, thus time step=T/10000, where 0 < time step < T.

I wish you every success!!!