I mean aerodynamic as in least air resistance.
Let's say lowest drag for a given volume.Most aerodynamic given what constraint? Lowest drag for a given cross sectional area? Lowest drag for a given volume? In general, the shape will tend to be somewhat similar to a teardrop, but it will vary depending on your constraints.
Yes, there is potential to reduce the drag by about 5% more by a more complete boat tail. The longer bullets that result would require a faster twist rate to maintain gyroscopic stability. The longer base would also reduce powder capacity by extending further into the cartridge case. These effects tend to combine to increase peak operating pressures in the barrel without increasing muzzle velocity. There is also the additional challenge of keeping such a design cylindrically symmetric. Imperfections in the overlap between the geometric center and the center of mass create significant inaccuracies as the bullet leaves the barrel. Resulting pitch and yaw also contribute to aerodynamic drag and tend to cancel out the small advantage gained with the longer boat tail.It's not bad, though it would be better with a more complete boat tail (which it does not have because of the requirements of barrel launching as well as spin stability concerns).
Some of these appear to flux, like a sine wave. Ie. at Mach 0.9 it has low drag, then at Mach 1 it has high drag, but at mach 1.1 it has low drag again. Is this the natural order of things, or are your statistics incorrect? If your statistics are correct, this would seem to indiciate that air has some kind of inherent frequency, causing wave phase cancellation effects.
Take a look at the graph in this wiki article:Some of these appear to flux, like a sine wave. Ie. at Mach 0.9 it has low drag, then at Mach 1 it has high drag, but at mach 1.1 it has low drag again. Is this the natural order of things.
Whoops. I can see why you'd draw that conclusion from the sample set I typed in my post. (The article talks about the effects of subsonic vs. supersonic.)Take a look at the graph in this wiki article:
I don't see any video, but one thing to keep in mind is that those numbers aren't telling you absolute drag, they're telling you the relative suitability of the shape for that speed regime. All of those shapes will have an absolute drag profile that looks pretty much like the Wiki chart, but the VK happens to be a bit below most of the others at mach 1, and a bit above the others at 1.5, dropping back down below the others at 2. That doesn't mean that the drag quantity is oscillating however.Whoops. I can see why you'd draw that conclusion from the sample set I typed in my post. (The article talks about the effects of subsonic vs. supersonic.)
But if you look at the chart it seems to continue even after sonic boom...it goes 0.9 low then 1 high then 1.1 low then 1.25 high then 1.4 low and so forth.
The von Karman almost seem to be symetrrical, with drag highest at 1.5 and then low drag at 1.0 and 2.0. Which the possibilities in my mind makes this seem to be some kind of phase timbre effect, being analogous to sound theory, or the results in the chart are inaccurate.
What Im trying to say is Wikipedia provides a chart like this, implying a simple drag related to the sonic boom.
I'm saying its not so simple, I think its more analogous to this video below.
(can't find it just think of a crazy looking video with sine waves and eq frequencies and such.)
Welcome to the PF.known as the teardrop - it's the shape water forms when it runs down a window because it's been pushed into that position by the air flowing over it on the way down
USGS said:The common raindrop is actually shaped more like a hamburger bun
The most aerodynamic shape does happen to be fairly close to a stereotypical "teardrop" shape though (with a longer nose - see the paper I linked in my earlier post for a full analysis), despite the fact that raindrops arrange themselves into a very different shape.Welcome to the PF.
I think you may have made a typo here, and also have a misconception about raindrop shapes. When you said the teardrop shape is formed by airflow as the water runs down a window, there is no airflow when water is running down a window. I think you meant to say that the teardrop shape develops because of airflow when in freefall (like rain). However, that also turns out to be a popular misconception...