Unsteady Flow-Time Step Size
 

Hello,

I using unsteady flow option in fluent to solve a non-premixed combustion problem.

I need to define the number of steps and the steps size. The total chamber length is around 250mm and the maximum velocity is around 0.5 cm/s.

Please anyone could tell me what should be the number of steps and the step size, and also the max. number of iteration. How should i calculate them?

Thank you very much.

Re: Unsteady Flow-Time Step Size
 

Hi

The time-step is dependent of the size of the cells. You should take the minimum cellsize in your domain. The timestep is then:

dt = size/speed/4. (courant number around 0.25 with reactions)

this is the maximum dt.

The number of iterations is then: 0.25/0.005/dt.

good luck!

Raoul