REFLECTOR: Vortex generators location for armpit cooling scoops

Fri Aug 16 19:09:05 CDT 2013

Thank you so much for that prescription. I can tell you put a lot of time VG And testing.

Sent from my iPhone

On Aug 16, 2013, at 5:05 PM, Brian Michalk <michalk at awpi.com> wrote:

> I never really believed that a vortex generator worked, until I was flying in a 737 on a humid day and could see how a VG mounted on the engine nacelle cause a vortex that carried over the wing right above an aileron.
> 
> I've thought a lot about vortex generators for years and how in the world they accomplish what people claim.  People say they help the air stay attached to the wing.  Now, that's an odd claim, because they make turbulent air, and how does that keep it attached to the wing.
> 
> So yes, think of it as a mini tornado.  If we want to keep the air attached, think of it as adding pressure to the air that presses it against the wing.  Where does that pressure come from?  It comes from putting more air molecules in the place we want them, near the wing, which means that they come from somewhere else, meaning that somewhere else must have a vacuum because we took some molecules from that place.
> 
> The vortex generator makes a tornado.  It is a swirling mass of air, with the center of the vortex being a vacuum, and the mass of the molecules rotating about center, wanting to go in a straight line tangent to the rotation, but the vacuum keeps the molecules going in a circle.
> 
> So, the VG makes an area of vacuum, providing higher pressure some distance away from the vacuum.  I can visualize how this works on a wing to offset stall.
> 
> For a NACA duct, I can visualize the tornado, with it's side going right into the NACA inlet.
> 
> Anyway, this is how I see it in my mind.  I was baffled for years, and I hope this helps others see how they work.  If I'm totally wrong, I would like to know why.
> 
> Now, if I could ever figure out trailing edge fences, or the drag inducing right angle exhaust, I will be a happy man.
> 
> On 08/16/2013 11:02 AM, Laurence Coen wrote:
>> Jeff,
>>  
>> A vortex is like a tiny tornado.  Newton pointed out that things in motion tend maintain direction and motion.  Air flowing over a curved surface wants to go in a straight line so it tends to separate from the surface. Vortex generators help the air stay attached and follow the curve.  The way I picture my vortexes working is the upper one spins CW and the lower CCW thus stuffing air down into the oil cooler opening.  Of course         if I actually knew all about aerodynamics I'd be cruising at 300 kts on 4 gal/hr.  Never the less I saw a 10F drop across the board in oil temp.  Placement was by sticking them where I thought they would work.  No science at all.
>>  
>> Larry Coen
>> N136LC
>> 
>> From: jeff findarle
>> Sent: Thursday, August 15, 2013 5:52 PM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: Vortex generators location for armpit cooling scoops
>> 
>> OK, So I am trying to understand what is happening here         aerodynamically? Sorry, but I am new to all this. It looks like you are trying to disturb the airflow over the fuselage to somehow help air to the cooler? Is this correct and did you see any benefit from it? If it is working, could you maybe take a pic with a measuring tape depicting the distances from the openings. Would be greatly appreciated.
>> 
>>  
>> TEAM JEFF,
>> Jeff Findarle, GRI & Darin Heckel
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>> 
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>> 
>> From: Laurence Coen <lwcoen at hotmail.com>
>> To: Andrew Ellzey <ajlz72756 at yahoo.com>; Velocity Aircraft Owners and Builders list <reflector at tvbf.org> 
>> Sent: Thursday, August 15, 2013 10:18 AM
>> Subject: Re: REFLECTOR: Vortex generators location for armpit                     cooling scoops
>> 
>> Andy,
>>  
>> There are no vortex generators in front of my armpit scoops (see previous).  They are in front of my oil cooler inlet on the nose and I attached a photo to give an idea of what they look like.  They are made of angle aluminum and attached with silicone rubber cement.  Something                         1 1/4" tall should do it.  The ones in the picture are 1" tall by 1" wide.
>>  
>> Larry Coen
>> N136LC
>> 
>> From: Andrew Ellzey
>> Sent: Wednesday, August 14, 2013 10:19 PM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: Vortex generators location for armpit cooling scoops
>> 
>> Larry,
>>  
>> So that is the question, how tall are your vortex generators, how far out in front of the armpit scoops did you place them? Did                             you make them, or buy them and if you bought them, where from. Can you please send a photo.
>>  
>> Thanks,
>>  
>> Andy
>> 
>> From: Laurence Coen <lwcoen at hotmail.com>
>> To: Velocity Aircraft Owners and Builders list <reflector at tvbf.org> 
>> Sent: Wednesday, August 14, 2013 6:25 PM
>> Subject: Re: REFLECTOR: Vortex generators                                     location for armpit cooling scoops
>> 
>> Andrew,
>>  
>> I have armpit scoops on my SR/RG that look just like yours.  When I mounted them I was concerned about the boundary layer and extended the scoops 3/4" out from the fuselage so the entire scoop is outside the boundary layer.  I also added an insert that looks like venturi that in theory should help with pressure recovery.  The fact                                         that I don't have cylinder head cooling problems doesn't mean that it will work for you.  I am down draft cooling a 220 HP Franklin.  I have vortex generators ahead of my oil cooler inlet and that did lower my oil temp.  If you try vortex generators I would suggest that they be tall enough so they stick out of the boundary layer.
>>  
>> Larry Coen
>> N136LC
>> 
>> From: Andrew Ellzey
>> Sent: Wednesday, August 14, 2013 3:50 PM
>> To:
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