Bernoulli Effect

H

Hambone

Guest
A old shooting buddy mentioned the Bernoulli Effect in regards understanding how wind affects the bullet light.

The only info I can find I my search to better understand what he was trying to tell me about the Bernoulli Principle is in regards to how fluids behave. Which doesn't help much.

Does anyone have any info that has a direct connection with rimfire BR?
 
Actually you should look into the Magnus effect. The Bernoulli effect does not really apply direct to spinning objects and are not able to fully explain what is going on.

A brief introduction to the Magnus effect can be found on Wikipedia which was not too bad written.

http://en.wikipedia.org/wiki/Magnus_effect
 
Sir: The fluid dynamic associated with this effect is that air passing over a lifting surface produces lift. In BR [even rim fire BR] a wind from the left when combined with the bullet rotation provides lift to the bullet causing a deflection to the right[due to the wind from the left] but also a slight lift[up]to the POI. In summary: A wind from the left deflects the bullet to the right and slightly up while a wind from the right deflects the bullet to the left and slightly down. Knowing about this affect one can tighten groups if one can properly read the wind. BE WELL....V/r mk
 
perhaps Mr Mnakuchi is from Australia but in the US, Mr Frey is correct and Mr Mnakuchi has it reversed.
 
mnakuchi said:
Sir: The fluid dynamic associated with this effect is that air passing over a lifting surface produces lift. In BR [even rim fire BR] a wind from the left when combined with the bullet rotation provides lift to the bullet causing a deflection to the right[due to the wind from the left] but also a slight lift[up]to the POI. In summary: A wind from the left deflects the bullet to the right and slightly up while a wind from the right deflects the bullet to the left and slightly down. Knowing about this affect one can tighten groups if one can properly read the wind. BE WELL....V/r mk
Click to expand...


That is true, but the wind speed itself is nothing compared to the spin of the bullet itself meaning that the add on is negligible more or less. You cannot explain a 20 degree lift (or so) from a left side wind regardless of the wind speed. The Magnus effect will.

I principle you are on to something, but Bernoulli alone does not fully explain what is going on.
 
Ok. Can I just check that I've got this correct


Shooting a rifle with a rh twist barrel with a wind blowing L>R moves the bullet right andVdown and with a R>L wind moves the bullet left and^up.

In the link HTB posted there is the following comment. "Overall, the effect of the Magnus force on a bullet's flight path itself is usually insignificant compared to other forces such as aerodynamic drag." Which causes me to ask the question which "Effect" has the most influence on a .22r/f bullet?
 
Hambone said:
Which causes me to ask the question which "Effect" has the most influence on a .22r/f bullet?
Click to expand...

The Magnus effect is still the effect to consider. Sure, if you have side wind to some degree this will indeed have a bigger effect on the bullet than the Magnus effect itself. But the lift (or downward) push you will see from i.e. a 90 degree side wind comes from the Magnus effect. The Bernoulli explain what happens with a subject that is not spinning, the Magnus effect takes this into account. That is a big difference despite the kind seem to explain the same effect. But what Bernoulli cannot explain is that a bullet (with a normal drift) will be pulled slightly to the right when you get far out (ok - then you need some CF-cartridge) but this is explainable using the Magnus effect.

A spinning bullet does not behave as a wing on a plane, but that wings behaviour could be explained by Bernoulli.
 
HTB

Gotta ya .... I think.

I appreciate the further out you go the longer the bullet is subjected to all effects gravity, wind, yaw, etc.
 
To the best of my knowledge the Magnus moment and Bernoulli effect acting on rimfire projectiles at transonic and subsonic speeds have an insignificant impact.

The effect of wind on the trajectory of rimfire match ammunition causing vertical dispersion distributed along a 9:30/3:30 slant line is called aerodynamic jump.

If you search thru ARL (Army Research Lab) and BRL (Ballistic Research Lab) documents, you should be able to find multiple instances where this phenomenom is explained in detail.

Landy
 
I have it on good authority, from a man in Borden, In, that the toilets flush counterclockwise and bullets go the wrong direction down south. Surely the laws of physics aren't that maliable.
 
All I can confirm, is that all the toilets I flushed down-under were equipped with power flush units and they flushed so fast, you couldn't tell what direction the water was turning. As for the wind effect on the bullet, my 52D didn't care.
 
DonMatzeder said:
I have it on good authority, from a man in Borden, In, that the toilets flush counterclockwise and bullets go the wrong direction down south. Surely the laws of physics aren't that maliable.
Click to expand...

Don

Did he charge you a research fee or a consultation fee for that information. He likes to charge fees does our man from Borden, In
 
I told him to put it on account, on account of dirt floor machinists are plentiful and cheap in this ecconomy.....
 
HuskerP7M8 said:
To the best of my knowledge the Magnus moment and Bernoulli effect acting on rimfire projectiles at transonic and subsonic speeds have an insignificant impact.

The effect of wind on the trajectory of rimfire match ammunition causing vertical dispersion distributed along a 9:30/3:30 slant line is called aerodynamic jump.

If you search thru ARL (Army Research Lab) and BRL (Ballistic Research Lab) documents, you should be able to find multiple instances where this phenomenom is explained in detail.

Landy
Click to expand...

Some of the ARL stuff has been expanded upon, much of it by Frank Tirrell in a series of articles ,some of which had a prototype EPS type slug. These were all published in Small Caliber News. As I recall Frank's stuff went on to show that a slug travels slightly behind a pressure wave and that with a supersonic slug, when it goes back subsonic the center of pressure moves back onto the slug causing it to breifly destabilize. I believe one of the more points of research leading to widespread use of flat slugs starting out subsonic.
 
Anyone know where and how to get a read of Frank Tirrels articles now that SCN has left the building?
 
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