How Far ?

[243Mendoza]

Does the "transonic

There is no "buffeting effect".

...

There is no shock or buffeting,those ideas come from too many old WW2 movies).

The transition from above the speed of sound to below the speed of sound is smooth and seamless.

The above is not "my opinion"... it comes from thousands of shadow graphs fired at Columbia University when I was a research consultant... we were studying the flight path of really small projectiles...
.

Wind tunnels have smooth air compared to a range with gusty sidewinds. These sidewinds can cause shocks to appear and disappear on a bullet which is near sonic.

Bullets are smooth bodies but aircraft have parts which are not and shocks can move around quickly when approaching sonic conditions.

 

[CatShooter]

Does the "transonic

There is no "buffeting effect".

...

There is no shock or buffeting,those ideas come from too many old WW2 movies).

The transition from above the speed of sound to below the speed of sound is smooth and seamless.

The above is not "my opinion"... it comes from thousands of shadow graphs fired at Columbia University when I was a research consultant... we were studying the flight path of really small projectiles...
.

Wind tunnels have smooth air compared to a range with gusty sidewinds. These sidewinds can cause shocks to appear and disappear on a bullet which is near sonic.

This comment is beyond silly, and is sheer fabrication.

You know nothing of what you speak.



.

 

[243Mendoza]

Does the "transonic

There is no "buffeting effect".

...

There is no shock or buffeting,those ideas come from too many old WW2 movies).

The transition from above the speed of sound to below the speed of sound is smooth and seamless.

The above is not "my opinion"... it comes from thousands of shadow graphs fired at Columbia University when I was a research consultant... we were studying the flight path of really small projectiles...
.

Wind tunnels have smooth air compared to a range with gusty sidewinds. These sidewinds can cause shocks to appear and disappear on a bullet which is near sonic.

This comment is beyond silly, and is sheer fabrication.

You know nothing of what you speak.
.

Is it April 1st and fools are about? I thought it was past that.

 

[CatShooter]

Wind tunnels have smooth air compared to a range with gusty sidewinds. These sidewinds can cause shocks to appear and disappear on a bullet which is near sonic.

So the blowing wind makes shock waves "appear and disappear"...? Is that right. And, pray tell, just what are your references to this magical effect?

Or did you figure this out all by yourself.


.

 

[Bryan Litz Ballistics]

Jerry,
Wow, you've been busy! Thanks for that report on your VERY long range shooting. These gems of real data can be used to confirm or invalidate the predictions of my 6-DOF bullet models which use aerodynamic tables that have some 'questionable' values critical to the prediction of transonic stability. Obviously, if my model predicts catastrophic failure in a case that you just shot thru, I can confidently adjust my aero-coefficients! I'm not as surprised to hear the >6.5mm calibers making it thru, but the .223 really surprises me. Very good work.

Catshooter,
I know what Steve does for a living, and I can vouch for his knowledge in this area. He knows what he's talking about. Allow me to elaborate on his point.
When comparing the air in a wind tunnel to the outside air on real shooting range, there's more than just crosswind to consider. Think about the mirage you see over the heated ground on a sunny day. That mirage indicates local variations in air temperature and density thru which the bullet passes. As the bullet is flying thru the transonic region, the areas of supersonic and subsonic flow are changing, and are very sensitive to the local Mach number, which depends on air temperature. As the bullet passes thru transonic speed, these variations in air temp and Mach number can cause local shocks to 'appear and disappear' as Steve describes. Experience confined to wind tunnels will not show this effect because there are not local variations in air temperature effecting Mach number like in the real world.
I also suspect that another reason for your difference of opinion may stem from the fact that you mentioned working with 'very small projectiles'. Perhaps your observations stem from a different Reynolds number regime, which is often the 'scale gremlin' of aerodynamics.
Whatever the reason for the difference of opinion, I'd rather get to the bottom of it constructively. Stubborn name calling and 'urinary jousting' don't have a good track record for problem solving.

-Bryan

 

[CatShooter]

You are assuming that because our research was with small projectiles, that we had no experence with standard projectiles - not so - we did out base line studies, and color Schlieren calibrations with standard projectiles - a 30-06, a .222, and a 30 Luger.

I am fully aware of Reynold's numbers, but your theory that mirage and local temperature variations make shock waves appear and disappear, doesn't hold water - the local variations in temperature are on the order of a few degrees at most, and don't amount to enough to effect the speed of sound more than a few feet per second, and that amounts to about 5 feet of travel of the bullet.

The energy that is in the conic shock wave at 20 fps above the speed of sound doesn't amount to anything at all... it is so minor in the overall picture. If the bullet goes through a few feet of transition, the energy involved is minuscule and far below the threshold required to effect the bullet - they are barely large enough to be more then light sound waves.

And of course, we get to the really BIG BUG in this theory.

If there is any mirage or wind effect that has a dimes worth of science,it would effect all bullets the same, and it doesn't.


.

 

[Bryan Litz Ballistics]

Catshooter,
Sounds like some interesting research you were doing. If you have access to, or can point me to some of those color Schlieren's that you talked about, I'd be interested in seeing what they look like. Not questioning you, just curious.

I am fully aware of Reynold's numbers, but your theory that mirage and local temperature variations make shock waves appear and disappear, doesn't hold water - the local variations in temperature are on the order of a few degrees at most, and don't amount to enough to effect the speed of sound more than a few feet per second, and that amounts to about 5 feet of travel of the bullet.

Your analysis is in error here. Of course, the variation in local temp only affects Mach number by a few fps, which does only correspond to a short amount of travel for the bullet. However, the bullet is in the transonic regime from about Mach 0.8 to 1.2,roughly 896 to 1344 fps) which can be a distance of 500 yards or more. During this entire distance, the bullet can have areas of supersonic and subsonic flow over it. When the bullet encounters fluctuations in local air temp and or crosswinds that affect the Mach number, these areas of local super and subsonic flow fluctuate accordingly. I think this is the 'buffeting' effect that's talked about. This happens for many 100's of yards as the bullet passes from supersonic to subsonic.

And of course, we get to the really BIG BUG in this theory.
If there is any mirage or wind effect that has a dimes worth of science,it would effect all bullets the same, and it doesn't.

The effect is different for each bullet configuration, and depends a lot on the state of the atmosphere which can change when the sun goes behind clouds. I assert that the effect is present for all bullets, but the specific aerodynamics of each bullet reacts to the effect differently.

I hope you continue to take my analysis as constructive. I'm not arguing for the sake of arguing, the truth is important to me. Unfortunately, on matters like this, there is not a broad range of direct experience to draw on. We have to rely on our critical thinking and intuition,dangerous!)

-Bryan