Vena Contracta 'template'
 

After a dose of BAYER HEROIN (R), I revisited the fluid mechanics text and was captured by an image of the famous 'vena contracta' entry loss, for a submerged, flush, straight-edged, pipe inlet feeding off a larger reservoir.
As the water enters the inlet, it forms a Prandtl surface of discontinuity, swept, rotationally into a streamlined torroidal ring of dead water, in the form of a perfect venturi, as you'd find looking down any barrel of a HOLLEY Dual-Feed, Carter AFB, or Rochester Quadrajet carburetor.
In 'side' profile, the forebody constitutes 39.3% of its length, with 60.7% aft-body, Length / height = 6.13, and maximum rear slope angle of 21.2-degrees, before reflection, blending onto the pipe wall.
Nature working it's magic.:)

I looked for a word count feature in two word processors then gave up and counted by hand, so approximately 113 words.

113/1000 multiplied by 100 equals 11.3% of one picture.

What happens if it's a twisted pipe? Viktor Schauberger: Austrian Patents (Vortex Control of Water Flow)

Well, I can't find a better thread so what do you think about the aerodynamics this?

https://cdn11.bigcommerce.com/s-jsi2...=1?imbypass=on
bigcommerce.com: Fishing Spear Accessory for the Can Cannon

This is a dart for fishing. Arrowhead not included. In theory the plate acts like the fletching on an arrow. I have no idea how the tip is centered in the bore. Using it to fish from a boat would involve refraction of the sight line, but then don't AR-15s work under water.

Kalashnikov's do.

I suspect it's a friction fit in the barrel so loaded centered would continue centered because of the pressure firing it.

what happens
 

I'd rather not think about it, considering all that's on my table.:)

think
 

I don't want to think about it. Maybe it's own thread?;)