Gentlemen:
I keep reading and seeing on these forums, the use of the word "Hydrostatic" instead of "Hydrolic" in regards for disrupting vital argans of animals. The word "static" means "stationary" such as a pipe standing full of water, where you have "Hydrostatic pressure" .
The dictonaries, say, this about "Hydrostatic"...
"Branch of science concerned with mechanical properities of fluid, "Not In Motion." Hydrolics, has to do with the mechanial propperties of fluid "in motion". Not a large deal, but somewhat confusing. I just read, and it may have been Ross Seyfried, who used the word "Hydrostatic". I thinik this a common misunderstanting. Or else I am very confused. The blood in animals, or in humans for that mater
are never "static", but are under "Hydrolic"
action of the heart. A bullet causes a catastrophic "Hydrolic" effect that can disrupt the entire system, depending on the size of the
animal and bullet performance. Thank you, I just wanted to get that off my chest. Merry Christmas.

[ 12-24-2002, 00:20: Message edited by: George Hoffman ]

Mr. Hoffman I believe it was Roy Weatherby sir, who brought about the subject matter some years ago in an article about his 257 Weatherby, if my mind serves me correctly. In any event there have been several pages written in gun rags over the last 45 years or so on the issue. Merry Christmas!

George:

Actually the distinction is hydrostatics versus hydrodymanics.

But let's not confuse this forum with science!!

Will

George,
Good point.

Hydrostatic is an ignorant term for this use.

Hydraulic, hydrodynamic, or even HYDROKINETIC would be much better terms for this use.

Thank you gentlemen. I have learned something today and confess to having used the wrong term for years. I will henceforth strike "hydrostatic" from my limited vocabulary.

You guys sure the term hydrostatic is wrong?
I think it applies to the forces traveling through a static fluid as in the body. Hydrolic Force is a force transfered via the motion of a fluid ie a small piston moves at one endof a closed system causes another piston to move at the other of the system......

Hydrostatic is still the correct term. The blood is of course, in motion, but it is insignificant to the velocity of the bullet. So, the static part would still apply for the mathematical model.

For example, full up 2 jugs, poke a small hole in one, then shoot them both with your favorite high velocity rifle. Assuming the water level hasn't dropped too much prior to impact, they will react much the same.

I do reserve the right to be corrected, since it has been a while since I took fluid mechanics.

I honestly don't know the correct answer. However, if you run a search on Google, you will find that "hydrostatic shock" when referring to bullet wounds is the most common useage.

Regards,

Terry

Gentlemen, I must agree with Will. The correct term is hydrodynamic! Hydrokinetic refers to both static and dynamic i.e. the entire field of fluid mechanics. Static referring to a state of equilibrium, while dynamic referrs to a state in flux.

Lucs

It should be hydrodynamic. My bad if I used the wrong word.

Pretty much an agreed upon occurence at 2100 fps with humans, defined by a doctor, in conjunction with the FBI, and their study on wounding.

s

"Hydro-Static" implies a static fluid pressure in the absence of flow. Heat exchangers and pressure vessels of all discription are leak tested hydrostatically, airstatically, or a combination of both, as in boiler weld repair testing.
The rationale here is that the high velocity projectile imparts a blow which so abruptly raises the static pressure of the body cavity fluids, that the resultant pressure waves create rupture and distress far beyond the actual bullet affected area, thus shocking the nervous system to a greater extent than would a projectile of moderate velocity. Weatherby viewed the body of the animal as a "closed system", with no in-out flow, possessing a certain static pressure of fluids, however low. From this perspective, I think the terminology is correct.
Think of it as a nanosecond change in static pressure, rather than attempting to describe the wave itself.

[ 12-24-2002, 09:44: Message edited by: Nickudu ]

Hydrodynamic was settled on to describe the actual effect that occurs, when a projectile around 2100 fps strikes an area that is mainly non-compressible fluid. Since the energy wave has no where to go, it is transfered through the fluid, in a wave, to a point where that fluid can enter a cavity, or area, that has little resistence. End result is something like the organ explodes, lets say into a lung cavity, that then compresses the air in the lung, creating further havoc.

It's sort of like hitting a groundhog with a 223,...

None the less, this explosive action seems to disappear when the animal gets larger then deer size, I believe. In other words, pretty much nothing you can shoulder fire is going to create hydrodynamic shock in an animal that is 2000 pounds, or greater, except a laws rocket.
s

Well, folks you may use what ever suits you, that is the way things are done where firearms are concerned. Nothing said or named has any real meaning except to the namer himself!

Hydrostatic shock is correct in the meaning which Weatherby used it. HYDRO is basicly water or fluid, STATIC is staionary. It has nothing to do with the destroying of organs, but the fact that water is not compressable, and therefore sudden violent pressure applied to a body of water that is contained in a tube, as is blood inside an artery, has to go someplace, as it can't be compressed into a smaller volume,something has to yeald to the sudden pressure,so blows the tube apart.

Since we have been useing the word HYDROSTATIC since the 40s, I see absolutely no gain by changeing it today! Really, all one needs know is high velocity causes it, what ever you want to call it, and it kills all out of perportion to the size of bullet used. A 100 gr Hornady soft point .243 bullet hitting the heart/lung cavity of a muledeer at 2800 to 3000 fps is like a handgranade in the chest, because of the HYDROSTATIC SHOCK!

MacD37

Perhaps because WBY has been using the term, the doctors involved for the FBI want to distance themselves from those terms.

That said, I think the reason they want to use that term is some areas allow such effect, some don't. Lungs are air, compressible medium, so
at least with humans, it's quite possible to take a high velocity, 223, through your lungs, have two small holes, and no major damage.

But, your point is well taken.

Depends on the bullet placement.

Hydrodynamic is a bit more accurate. You are taking fluid, transfering energy through it, and when it hits a spot where that energy can exit, massive rupture, due to energy moving accross the
water based mass. Not to mention this energy radiates out from the impact area, creating trauma as the energy is transfered to nerves etc. as a high velocity 'punch'.

Dr. S