Head loss throught contact tank - seeking help as begineer

hi all, I’m new here, trying to experiment use of CFD modeling in a browser.

CFD modeling has always been outsourced at work it’s costly and slow, this project I’m trying to do on my own is very simple, i.e. just try to use CFD to determine headloss thru’ a ozone contact tank with different configuration (different number of up/down baffles, opening sizes etc).

Design like this I used to calculate by hand.

Now I have created a project, what do I need to do for a acad file, is it just simple dimensions with outline of the tank? How about water levels, flow rate etc… ?