Interesting Prop-Vortex Photo

[Serge_Krauss]

Here's a FWIW photo, forwarded to me by Wayne Buran in a set of fascinating WW II aviation pictures. I looked for a thread where it might fit in, but didn't find one. Its a 1943 carrier-deck photo of a Hellcat, showing the receding path of propeller tip vortices.

[Steve Fitton]

cool picture.  Wonder if you can get those off a model prop.....!

[phil c]

A model size prop definitely throws off similar vortices, only about 5-10 times faster- 10000 rpm vs 2-4000 rpm on a Hellcat.  You can see the fog start at the tlp of the rotation and move backward 15-18 in. or so in one revolution.  The vortex tube is the main component of "circular flow" sometimes mentioned around here and in free flight circles(there it includes the circular path of the plane too).

[Duke.Johnson]

cool picture.  Wonder if you can get those off a model prop.....!

This sounds like a challenge for my son, he's a camera/photo guy.  I'll ask him to try some fancy shutter work tonight when I get home.  He'll love it! He's going out Wednesday night to do some night painting shots, this is right up his alley. Planes and cameras

[Air Ministry .]

STRANGE . You dont get them with Jets .  

 


What is the meaning of THIS ?





oops



Thinking you need moisture / humidity to achive this . Early on a damp dewy day ?

[Tim Wescott]

Great pictures, Matt.  I think you're right on the weather conditions -- you probably need air that's almost at 100% humidity, ready to condense some water out as soon as it's disturbed.

I remember getting a window seat on a dash 8 flying out of Portland on a rainy day.  When the engines were run up there was a little tornado on the ground just under the prop -- I assume that it was from the prop vortexes hitting the ground and spinning any way they could.  It sure makes it obvious how any bit of crap is going to get sucked into the prop and flung onto your airframe.

[Brett Buck]

A model size prop definitely throws off similar vortices, only about 5-10 times faster- 10000 rpm vs 2-4000 rpm on a Hellcat.  You can see the fog start at the tlp of the rotation and move backward 15-18 in. or so in one revolution.  The vortex tube is the main component of "circular flow" sometimes mentioned around here and in free flight circles(there it includes the circular path of the plane too).

   Everybody understands that these vortices are mostly fixed in space, and that forward motion of the airplane makes them into spirals, right? It's not like individual air molecules are moving around and around in the spiral shown, and backwards.

   Brett

[Dan McEntee]

   I have a photo of a T-6 Texan taxiing on the old grass strip behind Parks College in Cahokia, Illinois, years ago. It was a humid morning and before the sun got very high, and there was some faint rings that showed up on film. Not sure which box they are in, but that is a project for a long cold weekend, sorting through old photos.
   Neat photo of the Hellcat and corsair!
   Type at you later,
    Dan McEntee

[BillLee]

   Everybody understands that these vortices are mostly fixed in space, and that forward motion of the airplane makes them into spirals, right? It's not like individual air molecules are moving around and around in the spiral shown, and backwards.

   Brett

Bingo!

[frank williams]

"are mostly fixed in space, and that forward motion of the airplane makes them into spirals"

 ....... or rearward motion of the air mass ....  but wait, isn't the air mass rotating some? ....

[Brett Buck]

"are mostly fixed in space, and that forward motion of the airplane makes them into spirals"

 ....... or rearward motion of the air mass ....  but wait, isn't the air mass rotating some? ....

  Certainly, it is moving backwards and rotating to some degree. But individual air molecules aren't being thrown from the prop and then following the path of the condensation. round and round.

     Brett

[Wade Bognuda]

I would get this in the mornings when the humidity was really high flying a 1340 Cat. Not only on take-off but in flight when the light was still low. Never in the evenings, though. Not enough humidity.

[phil c]

"But individual air molecules aren't being thrown from the prop and then following the path of the condensation. round and round."

That's right.  The condensation is water droplets from the prop tip vortices moving back with the airstream.

Try trailing a streamer into a prop and see where the bits go.  They definitely fly back and follow the airflow around the fuselage some, but not at all like the condensation vortices.

The difference in the votex spacing between the P-51 on the ground and the bombers in the air shows something about the speed of the air.  You can guestimate the prop rpm and compare it to the distance along the  vortex ring per revolution.