Computer Simulation of a Compensator

[Meat Target]

I have been playing around with compensator designs over the last few years, here are a few simulations I did on one of the available compensators.

I am not going to give an opinion on if I think the design is good or bad, I just thought the videos looked interesting. Plus it gives a look at what is really going on inside the compensator.

https://www.youtube.com/watch?v=h2CSsHOkbp0

Edited December 14, 2013 by Meat Target

[kneelingatlas]

Very cool!

Edited December 14, 2013 by kneelingatlas

[Kingman]

That's really wild.

[Hi-Power Jack]

Thanks for sharing. Would love to see comparison of some

other comps ...

[praff]

thats freakin awesome.....Not that I have really searched for it, but this is the first scientific evaluation I have seen. It seems like all other evaluations are purely opinions and feel. Would really be interesting to do a comparison of a few existing designs. Although, it really is subjective since every differently designed gun requires a different effect from the comp to achieve the final desired flat shooting, fast pistol.

[Whoops!]

This is very cool.

Other's have done similar flow simulations, but they haven't posted them for the world to see.

I'd be extremely interested in seeing some models with porting involved and how it relates to pressure at the comp. It seems the first and second chambers are doing the majority of the work, I'm curious how much porting would affect that.

Edited December 14, 2013 by Whoops!

[Carmine]

About freak'n time

[Mat Price]

Thats very cool

[gng4life]

So do you have a design on the market or are you going to release one based one some of the data you have?

[jid2]

Nice, I just started setting up a SW Flow model about a week ago as well. We should talk about boundary conditions! Did you use a pressure input or a velocity?

[outerlimits]

Ton of gas coming out the exit hole-not good

[JMike]

Extremely interesting. Thanks for posting that!

[DRichardson]

Does this take into effect the "plugging" action the bullet has as it passes through each baffle? Looking at the initial flow model I don't think it does. That could greatly effect how much gas is pushed out the ports and how much would make it out the muzzle hole.

[Albertl35]

Very cool indeed.

[kneelingatlas]

Does this take into effect the "plugging" action the bullet has as it passes through each baffle? Looking at the initial flow model I don't think it does. That could greatly effect how much gas is pushed out the ports and how much would make it out the muzzle hole.

Good point!

[outerlimits]

Does this take into effect the "plugging" action the bullet has as it passes through each baffle? Looking at the initial flow model I don't think it does. That could greatly effect how much gas is pushed out the ports and how much would make it out the muzzle hole.

Good point!

+10. Years ago my smith experimented with different exit hole diameters for each chamber baffle. Results were what you would expect.

[Meat Target]

So do you have a design on the market or are you going to release one based one some of the data you have?

No, nothing on the market it’s just a hobby for me. I have built a few different ones for my own use so far, a couple of rifle and shotgun comps. I also have some pistol comp designs that I am still playing around with but I don't have any plans to sell them. Seems like everyone and their brother has their own compensator design on the market right now.

[Meat Target]

thats freakin awesome.....Not that I have really searched for it, but this is the first scientific evaluation I have seen. It seems like all other evaluations are purely opinions and feel. Would really be interesting to do a comparison of a few existing designs. Although, it really is subjective since every differently designed gun requires a different effect from the comp to achieve the final desired flat shooting, fast pistol.

That’s the biggest problem with simulation. I can predict fairly accurately how the comp performs, this one makes more down force... this on pushes forward more...this one has a lower force spike. But it won't tell me if it will hold the gun flatter. But simulation does greatly reduce the number of different versions you need to try out since you have knowledge of what the changes will do.

Nice, I just started setting up a SW Flow model about a week ago as well. We should talk about boundary conditions! Did you use a pressure input or a velocity?

That took me about half a year to figure out and get working correctly. You really can't use inlet ports even if you have an accurate pressure or velocity curve to work with. The design of the compensator will affect the flow rate of the gas out the barrel. The solution is actually fairly simple once you work through it. Hint - You need to model the barrel you are testing the comp with.

Does this take into effect the "plugging" action the bullet has as it passes through each baffle? Looking at the initial flow model I don't think it does. That could greatly effect how much gas is pushed out the ports and how much would make it out the muzzle hole.

Unfortunately SoldWorks does not calculate with "adaptive mesh" so I can't simulate the bullet moving through the compensator. I have access to another program "Ansys" that will do it, but it's a huge amount of work to get to run. One of these days I will see if I can get it going to do a comparison.

I have read a bunch of research papers from the US arsenal on muzzle brake theory and calculations, their conclusion was the presence of the bullet will increase peak forces on the baffles but its effect is minimal on the overall performance of the brake.

In the simulations I did the bullet would have left the barrel in around 0.0001 sec. So the bullet would be in the compensator for a little less that 1/4 of the total pressure pulse.

With the bullet you would see larger force spikes in the graph in the beginning but the average forces would not change much. If anything the bullet would increase the effectiveness of the compensator a little bit.

[jid2]

I've got the barrel in the model and was using the chamber opening as the inlet, and was thinking to start with steady state, with the plans to then try and define a pressure curve for the inlet. But after a short discussion with the guys at work we thought we may need to model it as external flow. That's about as far as I've got so far.

We also talked about the effect of the bullet and that solidworks was not going to be able to do it. Your assumptions sound about right on the effects the bullet plays.

[Whoops!]

thats freakin awesome.....Not that I have really searched for it, but this is the first scientific evaluation I have seen. It seems like all other evaluations are purely opinions and feel. Would really be interesting to do a comparison of a few existing designs. Although, it really is subjective since every differently designed gun requires a different effect from the comp to achieve the final desired flat shooting, fast pistol.

That’s the biggest problem with simulation. I can predict fairly accurately how the comp performs, this one makes more down force... this on pushes forward more...this one has a lower force spike. But it won't tell me if it will hold the gun flatter. But simulation does greatly reduce the number of different versions you need to try out since you have knowledge of what the changes will do.

Nice, I just started setting up a SW Flow model about a week ago as well. We should talk about boundary conditions! Did you use a pressure input or a velocity?

That took me about half a year to figure out and get working correctly. You really can't use inlet ports even if you have an accurate pressure or velocity curve to work with. The design of the compensator will affect the flow rate of the gas out the barrel. The solution is actually fairly simple once you work through it. Hint - You need to model the barrel you are testing the comp with.

Does this take into effect the "plugging" action the bullet has as it passes through each baffle? Looking at the initial flow model I don't think it does. That could greatly effect how much gas is pushed out the ports and how much would make it out the muzzle hole.

Unfortunately SoldWorks does not calculate with "adaptive mesh" so I can't simulate the bullet moving through the compensator. I have access to another program "Ansys" that will do it, but it's a huge amount of work to get to run. One of these days I will see if I can get it going to do a comparison.

I have read a bunch of research papers from the US arsenal on muzzle brake theory and calculations, their conclusion was the presence of the bullet will increase peak forces on the baffles but its effect is minimal on the overall performance of the brake.

In the simulations I did the bullet would have left the barrel in around 0.0001 sec. So the bullet would be in the compensator for a little less that 1/4 of the total pressure pulse.

With the bullet you would see larger force spikes in the graph in the beginning but the average forces would not change much. If anything the bullet would increase the effectiveness of the compensator a little bit.

Good info, thanks.

To those who think too much gas exits the front of the comp, there's always going to be a huge amount of low pressure gas that exits the front of the comp with slow loads in a handgun. The trick is utilizing the high pressure gas in the compensator.

[kneelingatlas]

From what's being said here I'm beginning to think the size of the exit holes is not as critical to performance as I once thought... Does anyone have any experience with say .375" holes and .400" holes in the same comp?

[Sudden Death]

Wouldn't fast burning powders and slower burning powders play in there too ? Even different barrel lengths ( government length and shorty , or somewhere in between ) And one of my theory's is the same comp you use for a 38 super or super comp may not be the right choice for a 9 major, even though velocities may be the same but pressures won't. This is good data, but still a lot of variables

Edited December 16, 2013 by Sudden Death

[kneelingatlas]

The video states a peak muzzle pressure of 6900psi, which I'd be willing to bet is formulated from a slow burning powder like N105 in a 5" barrel, maybe the OP can clue us in, but if the powder were faster or the barrel shorter, that number would go down.

[Meat Target]

From what's being said here I'm beginning to think the size of the exit holes is not as critical to performance as I once thought... Does anyone have any experience with say .375" holes and .400" holes in the same comp?

Depending on the compensator design the hole size can be important. If you have three of more ports then you can get away with a bigger hole because the next ports will take up the slack. If you are running one or two ports then you will want to make the hole as small as you can get away with especially if the comp is physically small where you don't have much room to let the gas expand much.

Wouldn't fast burning powders and slower burning powders play in there too ? Even different barrel lengths ( government length and shorty , or somewhere in between ) And one of my theory's is the same comp you use for a 38 super or super comp may not be the right choice for a 9 major, even though velocities may be the same but pressures won't. This is good data, but still a lot of variables

What is important is the muzzle pressure at the point the bullet exits the barrel, the higher the pressure the more energy the comp has to work with. Barrel length, powder burn rate, bullet weight... will effect this. That being said changes in pressures will not affect the compensator design very much you may only see about a 5% change in port sizing. The biggest difference is the divergent angle of the gas as it expands, at higher pressures the gas will expand at a greater angle by just a little bit which will affect the spacing of the baffles.

But in general a compensator design to work at high pressures will also work well with lower pressures, I doubt you would notice the difference between a compensator design for higher pressures and one optimized for lower pressure.

The video states a peak muzzle pressure of 6900psi, which I'd be willing to bet is formulated from a slow burning powder like N105 in a 5" barrel, maybe the OP can clue us in, but if the powder were faster or the barrel shorter, that number would go down.

The 6900psi came from my current load of 38 super TJ, 10.6gr of AA -No. 7, 124gr JHP and 5" barrel (pressure data calculated using QuickLoad). Your are correct in that changing to a faster powder with the same power factor would reduce the pressure. But if you reduce the length of the barrel a faster powder may increase the muzzle pressure, a lot of variables to play around with.

[ExtremeShot]

I use smaller ports in my comps. I have bad elbows and I made a bunch of comps with different size ports, different number of ports, different shaped ports, and it seems, at least for me, that having smaller ports (which results in more vertical surfaces for the gas to push against) feels better on my elbows.

Others have also noticed that my comp doesn't have a lot of flame or gas coming out the top. I figure all that flame and smoke coming out the top (of other comps) is gas/pressure that can't be used to reduce felt recoil. Anyway, the smaller ports seem to work good for me.

I also add an area between the end of the barrel and first port for the gas to expand before it hits the first port. I haven't done any flow model like you but my setup seems to work pretty good. It would be cool to see my design run through your model.

D

[edited for typo]

Edited December 16, 2013 by ExtremeShot