Shockwave Shadows in Ultra Slow Motion

[dcali]

The energy mostly gets transferred to the weights. Eventually, it will leave the system through friction, air resistance and other losses.

But that's not the easy way to look at it, and you'd still have energy transferred to *both* weights - kinetic energy that was stored in the spring.

When you look at a system, momentum must be conserved. That is, the sum of all the parts' mass * velocity must always equal zero. So if the bullet moves, something must also move in the opposite direction - the gun. Since the gun weighs so much more than the bullet, it will be moving much more slowly, but the momentum will be equal to that of the bullet and gas, but in the opposite direction.

That is the simplest way to look at it. The forces, pressure, energy, etc, don't need to be considered, only masses and their velocities.

Think about a gun floating in air. The pressure in the chamber increases. Why would gun stay still while the bullet accelerated? The pressure is acting on them both. Why would one move and the other not?

 

[Bc'z]

The energy mostly gets transferred to the weights. Eventually, it will leave the system through friction, air resistance and other losses.

But that's not the easy way to look at it, and you'd still have energy transferred to *both* weights - kinetic energy that was stored in the spring.

When you look at a system, momentum must be conserved. That is, the sum of all the parts' mass * velocity must always equal zero. So if the bullet moves, something must also move in the opposite direction - the gun. Since the gun weighs so much more than the bullet, it will be moving much more slowly, but the momentum will be equal to that of the bullet and gas, but in the opposite direction.

That is the simplest way to look at it. The forces, pressure, energy, etc, don't need to be considered, only masses and their velocities.

Think about a gun floating in air. The pressure in the chamber increases. Why would gun stay still while the bullet accelerated? The pressure is acting on them both. Why would one move and the other not?

Thank you

 

[243Mendoza]

how about starting a thread separately on the recoil debate and keep this tread about the great high speed bullet schlierens? Just a suggestion from forum member.

Btw, I think there would not be much visual difference between tipped and non tipped bullets as long the ogive geometry is the same. The only difference would be a smaller normal shock in front of the tipped bullet.

 

[Texas10]

That, i think would be very interesting to see, transsonic shock wave variances caused by ogive shape. Would probably shine some valuable light on why some bullets remain stable while making the transition from super to subsonic flight while others do not.

 

[dcali]

Another interesting thing we don’t often get to observe is where exactly the flow goes turbulent for any given design. It’s my understanding that it’s different for different bullets and hard to predict. This impacts the bearing surface drag.

 

[jawjaboy]

That was cool.

 

[chkunz]

Another interesting thing we don’t often get to observe is where exactly the flow goes turbulent for any given design. It’s my understanding that it’s different for different bullets and hard to predict. This impacts the bearing surface drag.

This is probably not economically feasible with the high speed digital photography that is shown above. But there may be something that could be learned from computational fluid mechanics (CFD) although it would probably be expensive. But I am some what dated in that technology. There most likely has been significant advances I the last ten to fifteen years since I had some experience with this technology.

 

[dcali]

This is probably not economically feasible with the high speed digital photography that is shown above. But there may be something that could be learned from computational fluid mechanics (CFD) although it would probably be expensive. But I am some what dated in that technology. There most likely has been significant advances I the last ten to fifteen years since I had some experience with this technology.

I don't know a whole lot about CFD, but I used to do a lot of FEM, and it's tough to get that stuff to match reality without also testing - not sure if CFD has the same limitations. I do know there are some efforts out there to combine CFD and rigid body dynamics as a replacement for 6DOF trajectory models. That strikes me as insanely complex, but also kind of interesting.

The setup that they used in the video doesn't look out of range for a typical bullet manufacturer. Not hobbyist level, but doable, and possibly as useful as the radars that have started cropping up. They didn't show how long it took to get the videos they actually got. For all I know that took week. But it it is a matter of getting set up and then firing some rounds, that could be interesting.

 

[243Mendoza]

This is probably not economically feasible with the high speed digital photography that is shown above. But there may be something that could be learned from computational fluid mechanics (CFD) although it would probably be expensive. But I am some what dated in that technology. There most likely has been significant advances I the last ten to fifteen years since I had some experience with this technology.

Transition from laminar to turbulent flow has been in the research phase for decades. CFD can use various models for this calculation.

 

[Gene Beggs]

WOW ! This thread has delved into some things that I've never even thought of before. One thing that stands out clearly to me is the fact that when the bullet begins to move, recoil starts. It may not be nearly as strong as the main force of recoil that results from bullet exit but it is certainly strong enough to move the entire gun rearward. If this were not true, tuners would not work; and we have certainly proven in recent years that they do indeed work well and predictably.

All I can say about this thread is WOW! Keep it up fellas. We've got some brilliance at work here.

Gene Beggs

 

[SGK]

It would seem to me, from a rather basic point of view, that at a minimum the bullet must force the air out of the barrel in order to move forward. That alone creates recoil. (We have a jet of air forwards creating an equal and opposite force rearward.) It is true that if the forces were completely contained while the bullet is in the barrel there would be no recoil, but they aren't.

 

[tom]

Cool video.

It scares me to think about what some of you people do after it gets dark.

Tom

 

[ronsatspokane]

Consider a situation where the mass of the gun is significantly less that the mass of the bullet being fired. The gun accelerates, knocking the shooter on their ass and the bullet falls on the table where the muzzle was prior to the trigger being pulled. Who would like to sign up to test this case? I had a 338 Lapua that felt very much like that.

 

[Texas10]

Of the Slo-Mo video that I've viewed much has been revealed that common knowledge previously seemed to exclude. For instance, a certain amount of gas and burning powder leaves the barrel before the bullet emerges. Recoil is beginning however, the main thrust of the recoil seems to be related to the expulsion of the very high pressure gas once the bullet has cleared the muzzle. What we see at that point is very similar to a rocket engine expelling volumes of gas at supersonic speeds and creating the reactionary force we call thrust.

For a great example of barrel whip, watch the Slo Mo guys video on bullet racing. There you can see the barrel of an AK-47 bend and whip as the bullet travels and exits the muzzle. https://video.search.yahoo.com/sear...8cfc70215a80118f302571f796b6d9c2&action=click

 

[Gene Beggs]

It would seem to me, from a rather basic point of view, that at a minimum the bullet must force the air out of the barrel in order to move forward. That alone creates recoil. (We have a jet of air forwards creating an equal and opposite force rearward.) It is true that if the forces were completely contained while the bullet is in the barrel there would be no recoil, but they aren't.

 

[Gene Beggs]

There is another important consideration with the fact that the bullet must 'force the air out of the barrel in order to move forward' besides its effect on recoil. I have said for years, this is the reason our benchrest rifles go out of tune as temperature increases throughout the day.

Keep in mind that as the bullet sits there in the chamber before firing it goes from a dead stop to around 2.7 mach in the length of the barrel. Since the space in the barrel ahead of the bullet is charged with the weight of the atmosphere, the bullet must push and compress this air against atmospheric pressure in order to exit the muzzle. The heavier the atmosphere the more resistance the bullet encounters as it accelerates down the bore which of course, affects in bore timing. If ambient temp goes up and atmospheric pressure decreases, in-bore time is reduced and bullets begin to exit early. We can compensate for this by reducing the powder charge slightly (approximately .3 grains for each 5 degree increase in ambient temperature) or if so equipped, by adjusting the tuner to increase barrel frequency slightly. Most tuners in use today INCREASE vibration frequency when the tuner is turned IN toward the breach.

Gene Beggs