predictable friction loss

[bob_at_cw]

I am researching the best shape for a hose clamp to provide a consistent and predictable friction loss in the 1 to 2 psi range. The hose diameter will be either 3 or 4 inches and the water flow will typically be in the range of 10 to 50 gpm. The idea is that the hose clamp can be finely adjusted to a set-point to provide the desired friction loss.

I've considered a "venturi" shape versus a sudden contraction/sudden expansion shape to provide flow characteristics that are predictable but most references that I have look at it from the standpoint of accounting for "minor losses" rather than defining a precise relationship.

My fluid mechanics skills are quite dusty at present and so I would like to see if anyone has any suggestions.

Thanks much.

[edgepflow]

An orifice plate may be a good choice. There is a "recoverable" and "unrecoverable" pressure drop. There are many calculators available and most orifice plate manufacturers could also tell these two values.

[bob_at_cw]

Thank you for the excellent suggestion. I do, however, need for the device to be non-invasive to the hose.

[edgepflow]

OK, I see what you are trying to do.

Go to this website

http://pressure-drop.com/

Use the online calculation. Enter a "gradual contraction." I put in 30 gpm, and a 3" X 1.25" contraction with 45 deg angle, provides a 1.5 psi pressure drop.

[bob_at_cw]

Thanks edgepflow! - that is a great reference.