[Tcoat]

Originally Posted by Spektyr

I could be wrong, but my understanding of fluid dynamics would say that there's a fairly small range of variation in diameter that would work. The inlet/outlet diameter of the oil pump itself is a big factor. At some point you have to funnel the pickup tube up/down to that size.

As your pickup tube diameter increases beyond the size of the oil pump inlet you're going to see less flow around the outside because the pump cannot lift the entire volume of oil in the tube uniformly. The height of the column of oil is set, so the wider you make the pickup the heavier that much oil becomes and the pump has only so much lifting power. The result will be a column of oil within the total volume that actually moves upward, concentrating any particulates or chunks suspended in the oil to that part of the screen.

As the center of the screen gets blocked, the column will "hunt" around for an unblocked path, kind of like a tornado looking for a trailer park.

Again, I'm not certain, but my guess would be that the smoothest, most efficient (laminar) flow would be achieved when the tip of the pickup tube is at or very close to the same surface area as the inlet of the oil pump, so I doubt that it's undersized.

In summery