I figured I would start a new thread rather than stir up the shit-storm which has brewed in the 5,000m thread and what started in the GSC 414 G2 thread.
In the 5km thread another member asked me to do a quick check on a bullet design that he'd rolled together. I agreed to put it through the computer models that Ply1951Guy and I (mostly PlyGuy) have come up with in the past several months of research and development work.
Groper,
Here's the first IGES file that you sent. I asked Ply1951Guy to run it through the CFD models and do some initial investigation on it. This is not an entire, start to finish, analysis but rather a proof of concept and something to create pretty pictures. The computing system takes time to run each model and we didn't want to jeopardize our research time line through running multiple models and full analysis for what has turned into an online bickering contest. I promised we'd take a quick look, I really don't feel like getting dragged into the fighting over who said/did what. To all those reading, please take the analysis for what it's worth, please avoid from all the name calling, smack talking BS. I started a new thread to avoid the black cloud following those other ones, I appreciate the hard work going on to push the envelope in the "real" world. We would both like to continue with our research and push the computational envelope as well.
What we can do currently:
CFD Analysis that has been correlated to less than 1% difference with Mr. Bryan Litz's radar data on several commercially available bullets. This has been leveraged to analyze some research work and investigation into several common "high level" questions in bullet flight theory for small arms munitions. We are currently able to predict, with a high degree of certainty:
Overall Drag and Drag Coefficients
Various Ballistic Coefficients
Center of Pressure Location
Magnus Moments
Overturning Moments
Precession Rate
Pitching/Yawing Moments
Shock Wave formation
Driving Band aerodynamic behavior
Gyroscopic stability based on aerodynamic properties, not empirical Miller Stability
We are currently working on:
Dynamic Stability
Transsonic Stability Prediction
In general our models are run at a number of various velocities and various orientations needed to calculate the stability predictions. For the sake of time, as I mentioned above, only 1 simulation point was run for the bullet model that you sent over. Again, not a slight towards anyone here, but neither myself or Francis want to be involved with the internet bickering. I almost didn't do this work due to the fighting going on over the topics, but I know I promised that we would so here's the results.
This bullet was run at:
Mach 2.5 = 2815 fps @ Standard Temperature and Pressure (STP) Freestream Velocity
Incidence angle = 0*
14.5mm projectile, 1601 grains appx. weight
<span style="font-weight: bold">Img removed for upload space</span>
The total drag on the shape at Mach 2.5 is appx 22 Newtons
Based upon the 1600.85gr bullet weight and other physical parameters this translates to:
G1 BC = 1.215 +/-1% @ M2.5
G7 BC = 0.564 +/-1% @ M2.5
Obviously there is a lot more work involved to predict gyroscopic/dynamic stability @ the muzzle, average ballistic coefficient over flight regime, transsonic stability downrange, etc. To do this would have taken approximately 3 weeks of work on our part due to the solution times for each model.
If anyone has additional technical questions either of us will evaluate how much information that we have and are willing to divulge at this point and get back to them. Please be understanding that this approach is very new and the tools used are highly proprietary, when we are ready to go public it will be in the form of Research Journals and we'll make an announcement on the forum. Potentially we will be offering bullets and/or analysis to bullet makers for high confidence development data before real projectiles are ever fired in test.
Thanks.
In the 5km thread another member asked me to do a quick check on a bullet design that he'd rolled together. I agreed to put it through the computer models that Ply1951Guy and I (mostly PlyGuy) have come up with in the past several months of research and development work.
Groper,
Here's the first IGES file that you sent. I asked Ply1951Guy to run it through the CFD models and do some initial investigation on it. This is not an entire, start to finish, analysis but rather a proof of concept and something to create pretty pictures. The computing system takes time to run each model and we didn't want to jeopardize our research time line through running multiple models and full analysis for what has turned into an online bickering contest. I promised we'd take a quick look, I really don't feel like getting dragged into the fighting over who said/did what. To all those reading, please take the analysis for what it's worth, please avoid from all the name calling, smack talking BS. I started a new thread to avoid the black cloud following those other ones, I appreciate the hard work going on to push the envelope in the "real" world. We would both like to continue with our research and push the computational envelope as well.
What we can do currently:
CFD Analysis that has been correlated to less than 1% difference with Mr. Bryan Litz's radar data on several commercially available bullets. This has been leveraged to analyze some research work and investigation into several common "high level" questions in bullet flight theory for small arms munitions. We are currently able to predict, with a high degree of certainty:
Overall Drag and Drag Coefficients
Various Ballistic Coefficients
Center of Pressure Location
Magnus Moments
Overturning Moments
Precession Rate
Pitching/Yawing Moments
Shock Wave formation
Driving Band aerodynamic behavior
Gyroscopic stability based on aerodynamic properties, not empirical Miller Stability
We are currently working on:
Dynamic Stability
Transsonic Stability Prediction
In general our models are run at a number of various velocities and various orientations needed to calculate the stability predictions. For the sake of time, as I mentioned above, only 1 simulation point was run for the bullet model that you sent over. Again, not a slight towards anyone here, but neither myself or Francis want to be involved with the internet bickering. I almost didn't do this work due to the fighting going on over the topics, but I know I promised that we would so here's the results.
This bullet was run at:

Mach 2.5 = 2815 fps @ Standard Temperature and Pressure (STP) Freestream Velocity
Incidence angle = 0*
14.5mm projectile, 1601 grains appx. weight
<span style="font-weight: bold">Img removed for upload space</span>
The total drag on the shape at Mach 2.5 is appx 22 Newtons
Based upon the 1600.85gr bullet weight and other physical parameters this translates to:
G1 BC = 1.215 +/-1% @ M2.5
G7 BC = 0.564 +/-1% @ M2.5
Obviously there is a lot more work involved to predict gyroscopic/dynamic stability @ the muzzle, average ballistic coefficient over flight regime, transsonic stability downrange, etc. To do this would have taken approximately 3 weeks of work on our part due to the solution times for each model.
If anyone has additional technical questions either of us will evaluate how much information that we have and are willing to divulge at this point and get back to them. Please be understanding that this approach is very new and the tools used are highly proprietary, when we are ready to go public it will be in the form of Research Journals and we'll make an announcement on the forum. Potentially we will be offering bullets and/or analysis to bullet makers for high confidence development data before real projectiles are ever fired in test.
Thanks.