Dr. Sinha's deturbulator

[pierre smith]

Somehow I stumbled across this new invention while researching Cirrus gliders and this new technology looks really promising. Verified drag reduction and increased speeds. Bob Axom are you listening?

http://71.18.117.131/aero.asp

Regards,
Pierre

[Bob Axsom]

I read the information at the web site and I am currently printing the 16 page PDF file linked to it. I Have to say it looks tacky in the photo - notice the pull wrinkles in the corner etc. but I'm certainly keeping an open mind. When I was a young fellow 50 years ago I used to compete in free flight model competition. tricks like a thread attached to the upper camber of the airfoil, filiment stretched in front of the leading edge and multiple spars on the upper camber back to about 40% of the chord were some of the things tried to improve performance in that flight regime. There is an effect when you do things like this but I'll wait a little while before I try it. Maybe after I read the PDF file.

Thanks for the information

Bob Axsom

[tin man]

A well known test pilot and reno racer here in the bay area uses zipper tape on the bottom of his lancair wing, he wouldn't use it if it didn't work and he's not one to boast much.
Tom

[aelkins]

Interesting reading...
Being your basic bubba pilot, my mindset has been limited to lower-pressure -vs- higher-pressure pertaining to lift/drag/etc..
This gives a new window of knowledge. (at least for me)

The tape (containing strategically located ridges) positioned in the proper flow-zone of the wing cuases small vortices within the boundary layer. (morphing the camber air-flow)...
Looks good in theory.. but, I'll wait until the pros prove it out..

I noticed that in the pdf file, they conducted tests using oil streaks across the airfoil to determine flow/drag.
Shucks, I've been running that test on my C150 belly for years.
It's a shame all that data was wasted..

[N395V]

SinhaTech will begin selling hand-prototyped Version II Deturbulator kits for wings we have analyzed. Please see the list below. If you wish to add your glider model, we will require a deposit of USD $1,000 with the remaining USD $1,000 due on delivery.

I am afraid I can't be open minded about this.

20% ooops 25% improvement? Reminds me of the Billy Bob commercials for Orange clean. Buy one get one free plus 4 back scratchers and an easy reach. a $700 value for only $25.95

Zone of ZERO friction with tape placed well behind 30% of chord?

Maybe Innodyn can put it on their turbine blades for better fuel efficiency and it can run on salt fuel derived from salt water by running RF waves through pie plates into test tubes.

[n5lp]

Originally Posted by N395V

I am afraid I can't be open minded about this.

20% ooops 25% improvement? Reminds me of the Billy Bob commercials for Orange clean. Buy one get one free plus 4 back scratchers and an easy reach. a $700 value for only $25.95...

I know this whole deal sounds fishy. I also know Dick Johnson who did the Standard Cirrus glider testing. He is a highly qualified and very experienced performance tester who has no reason to fudge results and is not easily bamboozled. There are many glider manufacturers who are disgruntled because Dick did not find the performance they had claimed.

[keen9a]

Even believing all of the results (and they do look real), the applicability to RV's isn't really there unless you are going to fly very high.

The big 30% Max L/D improvement is great, but its MAX L/D which you care little about when you're trying to go fast. When we're flying an RV as fast as we can, the wing is already flying with good clean airflow over most if not all of the wing. There's no problem for the deturbulators to fix.

Take a look at page 9 of the AIAA Report. The deturbulated wing does great at low airspeed, but the lines cross around 85 knots CAS. Above that the deturbulators are creating drag.

Now if you climb really high, Max L/D will occur at a higher airpeed where you might be able to take advantage of the technology at higher speeds, but you lose HP faster with a normally aspirated piston engine.

[az_gila]

Originally Posted by keen9a

Even believing all of the results (and they do look real), the applicability to RV's isn't really there unless you are going to fly very high.

The big 30% Max L/D improvement is great, but its MAX L/D which you care little about when you're trying to go fast. When we're flying an RV as fast as we can, the wing is already flying with good clean airflow over most if not all of the wing. There's no problem for the deturbulators to fix.

Take a look at page 9 of the AIAA Report. The deturbulated wing does great at low airspeed, but the lines cross around 85 knots CAS. Above that the deturbulators are creating drag.

Now if you climb really high, Max L/D will occur at a higher airpeed where you might be able to take advantage of the technology at higher speeds, but you lose HP faster with a normally aspirated piston engine.

The testing is on a fiberglass sailplane with a laminar flow wing and a very smooth surface. The waviness measured (using a glider "standard" 2 inch gauge) is only about 0.002 to 0.004 inches.

I don't believe the RV airfoil is truly laminar (can an aerodynamics guy confirm this?) and even the best RV wing does not have the smoothness of the older Cirrus wing. The skin joints and any rivet "rings" in the surface are probably more than 0.002 inches alterations to the airflow.....

The speed thing is a common glider problem... optimization at lower speeds usually causes a degradation at higher speeds. It then becomes a question of what speed ranges do you need for your specific flight conditions. Strong thermals in the Western US favor fast speeds, and a slight loss at thermalling speeds if OK. Weaker conditions in Europe probably favor optimization at lower airspeeds. I guess RVs usually want to be optimized at high speed cruise...

As a previous poster mentioned, turbulators have been common on sailplanes for many years....



This invention seems to act in a similar way, but by creating much smaller vortexes than the "zig-zag" tape shown above that is about 0.020 inches thick.

Sounds good for my sailplane when the $$ comes down....

gil in Tucson

[keen9a]

Originally Posted by az_gila

I don't believe the RV airfoil is truly laminar (can an aerodynamics guy confirm this?) and even the best RV wing does not have the smoothness of the older Cirrus wing.

All airfoils have some laminar flow, but the airfoils labeled as laminar flow airfoils have been designed to maximize the cordwise distance that the flow remains laminar. The RV 6,7,8 airfoil is a NACA 2300 series airfoil which is about the best there was for low drag before the "truely" laminar flow airfoils came along. And your right, we don't have the surface smoothness required for them to work anyway.

Originally Posted by az_gila

This invention seems to act in a similar way, but by creating much smaller vortexes than the "zig-zag" tape shown above that is about 0.020 inches thick.

Actually, the claim here is that these strips reduce turbulence in the flow to keep the flow laminar. Zig-zag tape works by ensuring the flow is turbulent, and adding energy to the turbulent flow which helps delay/prevent flow separation.

Guess I should have explained this first, but here's a quick and dirty explaination of the flow across our RV wings:

1) Air hitting the leading edge forms laminar flow for approx the first 1/3 of the wing. In laminar flow, all of the particles of air are moving in roughly the same direction and the drag is very low.

2) Next, usually near the thickest part of the airfoil (or just aft) the flow becomes turbulent. All this means is that there are small eddies formed close to the surface. The drag is higher than laminar flow, but it is also less likely to become separated flow. The more turbulent the flow is the more drag and less likely separation is.

3) Finally, if you are flying at high angle of attack (AoA), the flow will become separated flow near the leading edge with the point of separation moving forward as AoA increases until stall where lots of the flow separates. Separated flow is no longer following the shape of the wing surface, and will even have some reverse flow where air fills the gap between the separated flow and the surface. Separated flow is very draggy.

Zig-zag strips make sure the flow is turbulent, and adds turbulence (I used energy earlier/same thing here) to prevent separated flow.

The deturbulator strips damp out the very small amount of turbulence in the laminar flow to keep in laminar. Really cool, and really amazing that they've come up with a passive system to do that.

[az_gila]

Originally Posted by keen9a

All airfoils have some laminar flow, but the airfoils labeled as laminar flow airfoils have been designed to maximize the cordwise distance that the flow remains laminar. The RV 6,7,8 airfoil is a NACA 2300 series airfoil which is about the best there was for low drag before the "truely" laminar flow airfoils came along. And your right, we don't have the surface smoothness required for them to work anyway.
......
The deturbulator strips damp out the very small amount of turbulence in the laminar flow to keep in laminar. Really cool, and really amazing that they've come up with a passive system to do that.

Thanks Ben... I guess I was stuck in the old turbulator mindset when I was reading about the smaller vortexes.... I missed the flexing to dampen bit...

You are right about it being cool, and it will be interesting to see practical results when more installations are completed.

$2000 is probably less than adding winglets to gliders, and it sounds like this idea has more effect....

gil in Tucson

Mini-Nimbus owner - incidentally, it is the Mini-Nimbus that was tested by Dick Johnson in 1977-78 - he has been testing gliders for a long time....