Strange Suction Effect While Dumping Air

[guruboy]

I was dumping air from my tank today and noticed something interesting.

It is a convertible yoke/din valve with the yoke insert in. If I open the valve on midway so that there is good airflow coming out, I can put my fingertip near the opening and it will actually get sucked in while the air is coming out. I can't actually press against the opening though, there is a kind of air cushion formed by the escaping air, but I definitely feel a suction pulling on my fingertip.

 

[teknitroxdiver]

Is the yoke insert tight?

Also, keep in mind that sticking your finger in the path of high-pressure air can cause subcutaneous emphysema, where air is forced through your skin and gets trapped underneath. Not good.

 

[cool_hardware52]

I was dumping air from my tank today and noticed something interesting.

It is a convertible yoke/din valve with the yoke insert in. If I open the valve on midway so that there is good airflow coming out, I can put my fingertip near the opening and it will actually get sucked in while the air is coming out. I can't actually press against the opening though, there is a kind of air cushion formed by the escaping air, but I definitely feel a suction pulling on my fingertip.

Likely the venturi principle. Makes carburetors work and airplanes fly. Try this: Take two strips of paper ~2" x 11" and let them hang down about 2 inches apart. Now blow between them.

Tobin

 

[fmerkel]

+1 for venturi effect.
Ever notice in good tornado videos that stuff gets sucked into the funnel, before the funnel gets there? Same thing.High speed air creates a vacuum in it's vicinity. It's part of the reason they are SO destructive. Stuff doesn't just get blown down. Junk gets sucked in, doing it's own damage, then the high speed debris along with the wind becomes much more destructive. Houses often 'blow up/explode' caused by this vacuum, before the tornado even hits them.

We have a dive here in Puget Sound that I think the dive current works on this principal in certain circumstances.

 

[WarrenZ]

I have noticed this with my din tanks you definatally can't do the golf ball trick with them. Just keep in mind you don't want to blast high-pressure air through your skin.

 

[Jack Hammer]

Yes, it's normal.

 

[Couv]

I thought this action was due to Bernoulli's Principle. But to be honest, I cannot explain the difference between Bernoulli's and the Venturi's Principles. At any rate, the faster the gas flows over a surface (your finger) the lower the pressure, so the area with no flow will have a higher pressure and push the object toward the low pressure. The same principle is at work on an aircraft wing creating lift.