There are tables and calculations for this. My brother, a third engineer
Maritime, learned this stuff and he says that theory and reality are rarely the same. Your dealing with a lot of variables here. Run, diameter, wall and joint smoothness, pressure, viscosity, pressure head and turn radius are the major variables. As you know, as with any calculations, the more variables you are dealing with, the less accurate will be your estimate.
Be wary that the ratings you get for pumps are for (unrealistic) ideal conditions, meaning full voltage, no run and no pressure head. Less than ideal conditions can slow down a pumps rate considerably.
I think the most accurate thing you could do is to build a physical model and measure that. Doing it with tables and formulas will probably be frustrating and probably not yield a very accurate estimate.