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Cavitation
Posted: Sat Aug 16, 2008 11:56 pm
by PVC Arsenal 17
Posted: Sun Aug 17, 2008 2:41 am
by trollhameran
I didnt read all of it but that is pretty cool, I expect ill read it all later.
Posted: Sun Aug 17, 2008 3:52 am
by jackssmirkingrevenge
We've touched on the subject
before 
Posted: Sun Aug 17, 2008 10:41 am
by spuzi14
The shrimp thing was fascinating. I didn't understand the wikipedia definition at first. The video helped me understand it.
Posted: Sun Aug 17, 2008 10:59 am
by PVC Arsenal 17
jackssmirkingrevenge wrote:We've touched on the subject
before
barely!
Posted: Sun Aug 17, 2008 6:10 pm
by jrrdw
My Chevy's failing oil pump is a good example i think. The gears inside of it spin on highly polished shafts. A groove gets worn in between the shaft and gear.
Burs form and hang up the gear slowing down the pump, (
and the engine as well, it's driven off the rear gear of the cam shaft)and the flow of oil. The bur shears off and the pump speed jumps up 150-200 RPM's.
That in turn crushes the flow of oil through the pump at a rate more then it can handle for it's size. Compressing the oil surge greatly.
And that my friends causes vapor balls to form, (Cavitation)!
Yes, one day it's going to blow up/lock up and leave me sitting ect.....
I have a new one but the swap out is a lot of work that I hate to do. I think I'll wait untill the worst happens and just swap engines, it's about the same amout of work.......... :scratch:
Posted: Wed Aug 20, 2008 1:23 pm
by Biopyro
You can use this principle to cleanly snap off the bottom of a beer bottle, if you don't strike hard enough you will hear the sound associated with cavitation.
NEPTUNE'S HAMMER
Obtain some V8 juice or orange juice in a small glass bottle. (Any vacuum-packed non-carbonated liquid should work.) Hold it in one hand and strike the top with the heel of your other hand. If you strike it hard, the glass bottom will fly off and the liquid will blast downwards. If you strike it more softly, you'll hear a loud "snap" sound. Practice striking it sofly enough to obtain the interesting noise. Now break the seal and let in the air, and you'll find that you can't create the snapping sound anymore. The sound is caused by cavitation, by a "water hammer" effect. Liquids are held together by atomic bonding, and if you create negative pressure, you can tear open some bubbles made of vacuum. When the bubbles slam shut again, the water pressure becomes momentarily immense. But if the liquid is at atmospheric pressure to begin, you can't create enough negative pressure to get to the cavitation realm. (This works with canned vegetables too, and with glass jars of pasta sauce.)
from
http://www.amasci.com/~billb/cgi-bin/in ... .html#menw
Posted: Wed Aug 20, 2008 3:02 pm
by Ragnarok
Biopyro wrote:You can use this principle to cleanly snap off the bottom of a beer bottle, if you don't strike hard enough you will hear the sound associated with cavitation.
Wow, it actually works...
Now I have to clean up all this smashed glass though. Bummer.
Posted: Wed Aug 20, 2008 3:11 pm
by Biopyro
oh damn, I forgot to say try and do it in a plastic bag! Sometimes it is perfectly clean, but often it does send bits of glass everywhere. There are also examples on youtube
Posted: Wed Aug 20, 2008 3:16 pm
by Ragnarok
Biopyro wrote:oh damn, I forgot to say try and do it in a plastic bag!
Don't worry!!
I did plan ahead, and did it into a large basin which caught the results quite nicely, and clean up was minimal.
The wording just amused me. I don't use the word "bummer" enough - it's fun!
Posted: Wed Aug 20, 2008 4:03 pm
by clide
Ah thanks for that link Biopyro. I've heard of that trick before, but like the guy in the video I couldn't get it to work because I was told to fill the bottle up all the way.
Posted: Mon Aug 25, 2008 8:18 am
by PVC Arsenal 17
Biopyro wrote:You can use this principle to cleanly snap off the bottom of a beer bottle, if you don't strike hard enough you will hear the sound associated with cavitation.
Hey I do that all the time! I didn't know it was cavitation though.