While at the Air Force Academy a few weeks back I was in an engineering seminar and one thing they discussed was the Magnus Effect, which was noted for its effect on the point of impact for artillery rounds.
For those of you not familiar, here's the basics: http://en.wikipedia.org/wiki/Magnus_effect
From Wikipedia:
The Magnus effect can be found in advanced external ballistics. A spinning bullet in flight is often subject to a sideways wind. In the simple case of horizontal wind, the Magnus effect causes an upward or downward force that depends on the direction of the wind which affects the projectiles point of impact. Even in completely calm air, a bullet will experience a small sideways wind component. This is because bullets have a yaw motion that causes the nose of the bullet to point in a slightly different direction from the direction in which the bullet is actually traveling. This means that the bullet is "skidding" sideways at any given moment, and thus experiences a small sideways wind component. (yaw of repose) All in all, the effect of the Magnus force on a bullet is not significant when compared to other forces such as drag. However, the Magnus effect has a significant role in bullet stability because the Magnus force does not act upon the bullet's center of gravity, but the center of pressure. This means that the Magnus force affects the yaw of the bullet. The Magnus effect will act as a destabilizing force on any bullet with a center of pressure located ahead of the center of gravity, while conversely acting as a stabilizing force on any bullet with the center of pressure located behind the center of gravity. The location of the center of pressure depends on the flowfield structure, in other words, it depends on whether the bullet is in super-sonic or sub-sonic flight. What this means in practice depends on the shape and other attributes of the bullet. In any case the Magnus force greatly affects stability because it tries to "twist" the bullet along its flight path, twisting it either towards the axis of flight (stabilizing) or away from the axis of flight (destabilizing).
So this got me to thinking. When we shoot long range, we must of course account for the distance the bullet will drift due to wind. We look at our ballistics chart and find that at say 1000 yards, the bullet will drift X number of inches in a 10mph crosswind. However, that number does not take into account what direction the wind is coming from. The rifling in our barrel causes the bullet to spin a certain direction. According to the Magnus Effect, all other variables being exactly the same, the bullet will hit in a different place if the wind is coming 90 degrees from the left versus coming 90 degrees from the right. Is there any way to account for this? Is the effect even big enough to worry about? Or it it more like the Coriolis effect in that, while it's there, it doesn't make much of an impact over a (relatively) short 1000 yards?
Just something that got me to thinking. Perhaps this is well known and I just hadn't heard the name for it before. What do you guys think?
For those of you not familiar, here's the basics: http://en.wikipedia.org/wiki/Magnus_effect
From Wikipedia:
The Magnus effect can be found in advanced external ballistics. A spinning bullet in flight is often subject to a sideways wind. In the simple case of horizontal wind, the Magnus effect causes an upward or downward force that depends on the direction of the wind which affects the projectiles point of impact. Even in completely calm air, a bullet will experience a small sideways wind component. This is because bullets have a yaw motion that causes the nose of the bullet to point in a slightly different direction from the direction in which the bullet is actually traveling. This means that the bullet is "skidding" sideways at any given moment, and thus experiences a small sideways wind component. (yaw of repose) All in all, the effect of the Magnus force on a bullet is not significant when compared to other forces such as drag. However, the Magnus effect has a significant role in bullet stability because the Magnus force does not act upon the bullet's center of gravity, but the center of pressure. This means that the Magnus force affects the yaw of the bullet. The Magnus effect will act as a destabilizing force on any bullet with a center of pressure located ahead of the center of gravity, while conversely acting as a stabilizing force on any bullet with the center of pressure located behind the center of gravity. The location of the center of pressure depends on the flowfield structure, in other words, it depends on whether the bullet is in super-sonic or sub-sonic flight. What this means in practice depends on the shape and other attributes of the bullet. In any case the Magnus force greatly affects stability because it tries to "twist" the bullet along its flight path, twisting it either towards the axis of flight (stabilizing) or away from the axis of flight (destabilizing).
So this got me to thinking. When we shoot long range, we must of course account for the distance the bullet will drift due to wind. We look at our ballistics chart and find that at say 1000 yards, the bullet will drift X number of inches in a 10mph crosswind. However, that number does not take into account what direction the wind is coming from. The rifling in our barrel causes the bullet to spin a certain direction. According to the Magnus Effect, all other variables being exactly the same, the bullet will hit in a different place if the wind is coming 90 degrees from the left versus coming 90 degrees from the right. Is there any way to account for this? Is the effect even big enough to worry about? Or it it more like the Coriolis effect in that, while it's there, it doesn't make much of an impact over a (relatively) short 1000 yards?
Just something that got me to thinking. Perhaps this is well known and I just hadn't heard the name for it before. What do you guys think?
