Computational Domain... Help!!
 

Hello, I am new to CFD and I have a project of the incompressible flow past the square cylinder of cross-section 20mm for Reynolds number 11000 (steady) and 22000 (transient). I have to study the effect of gap ratio G/H=0.25 and 1 from the below wall on wake and pressure coefficient.
I am confused with the computational domain that should I have to create the domain with dimensions same as any experimental data to compare the results at the end??