Vortex Generators

[Eric62]

Birdy raised the question under the pics of Russ's new cab gyro about fitting Vortex Generators ( Turbulators as some call them ).
They were fitted to the doors on mine when I bought the cab , with some extra ones to fit in line below that row but I didnt get around to doing . Dont know if they made any difference as it was rarely cold enough to fly with the doors on.
Owen would know as he would have done a lot of testing with them.
I have seen large twin engine planes at the airstrip that have them fitted to the wings ( a lot smaller & a heap of them ) & the pilots reckon they get better lift , improved fuel consuption etc.
I have also seen something similar fitted to the side of pantech trucks that was claimed to reduce drag , the guys that have them fitted swore they worked.
This has probably been discussed before , but I couldnt locate the topic.

[tomhall]

Eric, I had the pleasure of visiting and flying with Pat McNear near Fort Myers, FL. He is using some very interesting V.G.'s that you can see at : www.airtab.com He can cruise at 100+mph ! Tom Hall in MN

[Eric62]

Tom,
thats the ones I was talking about . Thanks for the info. I dont suppose you have any pics of Pat's machine ?
Birdy - they are available in Aus., but I dont know where , I will try & find out.Might be the go on your WASARAF!

[bartc150]

Here's some pics of Pat's RAF.

http://www.rotaryforum.com/forum/showpost.php?p=73172&postcount=1

[JByrd]

Hi Eric,

I am glad to say that in my opinion, the vortex generators on the aft edge of the cabin is actually quite a good idea and installed in the right place. This stirs the air just at the point of were it has to make the sharp curve around the cabin.

What it essentially does is increase the pressure recovery aft of the bluntness of the cabin (less suction in the wake). This reduces drag somewhat and should increase the moving volume of air into the center of the pusher propeller.

They do increase overall drag slightly of themselves but the global effect is to reduce the cabin drag enough to be of a positive benefit. The downside is the sharpness of the surface to body (i.e. head) contact and a silght increase in acoustic noise, but likely no factor in gyro operations.

Additional - 2006.03.25 - One of the most successful uses of vortex generators I ever observed was a problem with a wind tunnel not making performance parameters after new construction. A flow field survey determined the air was jetting down the center of the tunnel and a very thick boundary layer 1-2 feet was developing around the entire circumference of the exit cone before the fan. The outer perimeter of the fan was essentially not engaging fast flow. There was a lot of vibration and non-symmetrical loading on the propeller.

One of the practical minded engineers (Joe Brusse to his credit) decided to install vortex generators aft of the test section (to not disturb the flow) around the circumference of the duct about 80 feet ahead of the fan. The result, nearly a 20% increase in tunnel speed in the test section for a relatively slight increase in electrical power.

The principle of the situation is the higher kinetic energy air flowing along the tunnel center line is more strongly mixed with the lower kinetic energy air in the boundary layer around the perimeter. Thus, high speed air in the center line is slowed down and the low speed air around the perimeter of the tunnel cylinder is sped up. The air meets the fan at a more uniform speed all over the prop area. The full propeller area is much more efficiently utitlized.

Jim B.

[birdy]

Thanx for all this.
I got onto Owen last night ecka, and after talkn to him, i recon ill try sum. He's sendn sum over in the mail, should be ere ina week.