SIMPLE family and Fractional Step Method
Dear friends.
I have tried to implement IBM to the incompressible NS solver which is written by M.Peric. The NS solver uses SIMPLE algorithm. But when I read articles which is related to IBM, almost of them use fractional step method instead of SIMPLE family algorithms. What are differences between them? What are strong and week points of them? Thank you very much. Sincerely, GeonHong 
In addition, my main interest is unsteady flow problems.

you can apply it to simple method too.
All you need is to give correct forcing terms to momentum equations. fluent has a ibm manual also on their site. If you get a chance have a look, they have explained how they do it. 
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