Hello,

These values are purely subjective and will decide the convergence and the accuracy of the solution.

The value for **time step size** will define the level of unsteadiness of the flow that needs to be captured. Make sure you set it below the smallest time scale of the flow. But this also depends on what you are primarily looking for from the simulation.

The value of **Number of time steps** will define the total flow time simulated. Total flow time = time step size x number of time steps.

The value of **Max iterations/time step** will define the level convergence of the solution for every time step.

What I told you is more of a bird's eye perspective, but to know more in detail, refer to this section of the Fluent's User guide: 32.13. Performing Time-Dependent Calculations (ansys.com)

If you are not able to access the link, refer to this forum discussion: Using Help with links (ansys.com)

Thank you.