steady or unsteady is better?
 

Hello to all!

To simulate stall in an airfoil with great accuracy what would give better results? A steady or unsteady solver?

Thanks in advance.

If you perform a steady simulation, you will not be able to find any periodic solutions. If this periodicity occurs in your situation, it may become difficult to get a convergent solution with certain discretization schemes. Transient simulations come with a price of course.

The problem i have with steady solution is that there is no stall, the Cl continues to rise! So, i was wandering if an unsteady solver could correctly calculate it.

Solve with unsteady first and then move to steady, it will give better convergence.

what time step should i use and how may iterations per time step?

del t = del x/v

del t= time step
del x= smallest mesh size
v= velocity

or just put time step 0.001 and no. of time step (maximum) and 20 iteration per time step

the smallest mesh size is the distance between the wall and the first cell adjacent to the wall or i understood wrong?

Smallest cell inside the domain.

A general rule for time stepping is:

Timestep = (1/10) * ((average cell size) / (average velocity))