As I was digging through some of the research material that I have amassed throughout the years, I came across this one (see attached)― Non-Newtonian Behavior of Ballistic Gelatin at High Shear Rates, Experimental Mechanics (2012) 52:551–560. I thought that you might like to see it.
Non-Newtonian Behavior of Ballistic Gelatin at High Shear Rates, Experimental Mechanics (2012) 5.pdf
In the attached paper there is a simple power law that allows for the adjustment of dynamic viscosity at high shear rates which is really useful for calculating Reynolds Numbers (Re = ρVD/μ) for high-velocity penetration events in the 10-4 seconds range. The coefficients for the power law were fitted against the empirical data using the 'least squares' method.
The equation is:
μ = αγ(n-1)
where μ = dynamic viscosity in centipoise (cp) for 10% gelatin
γ = shear strain rate in s-1
α = 4.5 x 10-3 kg∙s(n-2)
n = 2.22
As stated in the paper above, when the dynamic viscosity for a projectile is calculated for shear strains of 2,000s-1 and 8,000s-1, dynamic viscosity increases about 5 times as shown below:
4.5 x 10-3 kg∙s(2.22-2) x 2,000s-1(2.22-1) = μ = 3,243 cp
4.5 x 10-3 kg∙s(2.22-2) x 8,000s-1(2.22-1) = μ = 17,598 cp
Of course, the Q-model can be used to compute such time frames.
For the latest test that I conducted here: https://pistol-forum.com/showthread....slug-(P152XT1) ―
―the computed duration for that test was on the order of 4.858 milliseconds, so dynamic viscosity would have been on the order of―
4.5 x 10-3 kg∙s(2.22-2) x 2,058s-1(2.22-1) = μ = 3,716 cp
―which means that the average Reynolds Number (Re = ρVD/μ) for this event would be Re = 29.211 indicating that turbulence would be very low since Re < 2,000.
ETA: This paper might also add some valuable insight:
Laminar, Turbulent, and Inertial Shear-Thickening Regimes in Channel Flow, PRL 113, 254502 (2014.pdf
Last edited by the Schwartz; 04-16-2019 at 03:54 PM.
''Politics is for the present, but an equation is for eternity.'' ―Albert Einstein
Full disclosure per the Pistol-Forum CoC: I am the author of Quantitative Ammunition Selection.
''Politics is for the present, but an equation is for eternity.'' ―Albert Einstein
Full disclosure per the Pistol-Forum CoC: I am the author of Quantitative Ammunition Selection.
Good video.
I attended a ballistics workshop with Johann way back when. Good dude.
"It's surprising how often you start wondering just how featureless a desert some people's inner landscapes must be."
-Maple Syrup Actual
I definitely think that there are a few obvious points regarding the RCB stuff:
- There's no way to compare a bullet's performance in clear gel to anything other than its performance in clear gel. Trying to come up with some sort of conversion for ordnace gelatin or tissue or water-filled ziploc baggies or whatever is pointless.
- It goes completely wonky at higher velocities. Shooting it with rifles may be fun, but that's about it.
- The amount of tea-leaf reading people do over yaw cycles and "temporary cavities" in clear gel is silly, since it has no real correlation to what happens in tissue.
That Being Said™, however, I'll note that the pistol bullets I have usually seen that expanded well through 4LD and were found in the denim on the far side of a 16" block of clear gel were projectiles like the 124gr +P or 147gr HST and GDHP. So I guess they work well in that stuff, too.
Last edited by Tamara; 04-20-2019 at 09:51 PM.
In the past I was very obsessive and opinionated re: self defense ammunition and caliber selection. When I started working in the ER in my 1st year of medical school and realized how much of a non-factor the bullet was in GSW patient outcomes I quickly got off my soap box.
I am still choosy enough to only buy Speer/Federal products because I think they represent the highest quality product on the market, but I don't give really any of this stuff thought anymore. I really don't think it matters.
Hence my comment about Ralpie’s brother and the denim....