How is fuel distributed evenly to multi-engine rockets like the Falcon 9, Electron, or multi-engined Centaurs? I would presume that there is only one main propellant line that goes down the raceway then there is some kind of "splitter"? My fluid dynamics understanding is... limited evidently so if, by any chance you know of any recommended sources that I can read to better understand fluid dynamics in the engineering setting that would be much appreciated!
Partial answer (for Centaur and Saturn 1-B)
The H2 line emerges from the boost pump, which is mounted at one side of the base of the H2 tank. The line then wraps around the O2 tank and splits near its base to reach both engines.
The O2 line emerges from its boost pump which is located in the center base of the O2 tank. The line splits almost immediately and leads to both engines.
Schematic from Titan/Centaur T/C-1 Post Flight Evaluation Report (Colorized by me)
Here's an interesting (to me anyway) example from the Saturn 1-B. This stage had parallel tanks, not tandem, so all the drain points were near the bottom of the stage. With 8 engines there was a lot of plumbing.
Schematic from H-1C-D Engine Manual which I'm not seeing online ATM. Colorized by me.