Help:SIMPLER/PISO or Fractional step?

Quarkz

hi,

I am trying to develop a FV NS code using either SIMPLER/PISO or fractional step scheme. it's supposed to compute the unsteady airfoil's lift/drag with the possiblity to extend to movable airfoil & also 3D. However, it'll start from 2d structured grids.

I'm now considering which scheme to use. SIMPLER/PISO seems to be better documented but fractional step seems to be more popular for unsteady flow

I've some questions:

1. is fractional step usually faster than SIMPLER/PISO?

2. are both suitable for unsteady problems?

3. for airfoil problem, is it difficult to impose BC for fractional step?

thanks in advance!