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Sinha Deturbulators: Flight Test Evaluation
After three years of working to configure Sumon Sinha's deturbulator
tapes for my Standard Cirrus, we finally brought it to Caddo Mills for one of those Johnson flight test evaluations. He and Jeff Baird flew it six times with those shiny silver strips on the wings, then three times without. What did they learn? Come to the Convention in Memphis to find out. Dick, as usual, will tell it straight. Will you laugh? Will you be dumbfounded? Will you believe? Jim Hendrix |
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Sinha Deturbulators: Flight Test Evaluation
Jim,
Is it a passive system, no current? Mike OxAero wrote: After three years of working to configure Sumon Sinha's deturbulator tapes for my Standard Cirrus, we finally brought it to Caddo Mills for one of those Johnson flight test evaluations. He and Jeff Baird flew it six times with those shiny silver strips on the wings, then three times without. What did they learn? Come to the Convention in Memphis to find out. Dick, as usual, will tell it straight. Will you laugh? Will you be dumbfounded? Will you believe? Jim Hendrix |
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Sinha Deturbulators: Flight Test Evaluation
Mike,
Yes, it is passive. Dr. Sinha started his research with active surfaces. He used them both as sensors to frequency content in the flow and drivers to control the flow. He eventually learned that you can dispense with the complications of electrical control simply by using the energy present in the flow-surface interaction. Think of filtering attached turbulence flows into frequencies that are hard to maintain down stream. Jim On Dec 29, 8:23 pm, "Mike" wrote: Jim, Is it a passive system, no current? Mike OxAero wrote: After three years of working to configure Sumon Sinha's deturbulator tapes for my Standard Cirrus, we finally brought it to Caddo Mills for one of those Johnson flight test evaluations. He and Jeff Baird flew it six times with those shiny silver strips on the wings, then three times without. What did they learn? Come to the Convention in Memphis to find out. Dick, as usual, will tell it straight. Will you laugh? Will you be dumbfounded? Will you believe? Jim Hendrix- Hide quoted text -- Show quoted text - |
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Sinha Deturbulators: Flight Test Evaluation
I should have acknowledged that the testing at Caddo Mills is funded by the Dallas Gliding Assocation (DGA). They perform a great service for the soaring community by sponsoring Dick Johnson's flight test evaluations. Jim Hendrix On Dec 29, 7:37 pm, "OxAero" wrote: After three years of working to configure Sumon Sinha's deturbulator tapes for my Standard Cirrus, we finally brought it to Caddo Mills for one of those Johnson flight test evaluations. He and Jeff Baird flew it six times with those shiny silver strips on the wings, then three times without. What did they learn? Come to the Convention in Memphis to find out. Dick, as usual, will tell it straight. Will you laugh? Will you be dumbfounded? Will you believe? Jim Hendrix |
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Sinha Deturbulators: Flight Test Evaluation
OxAero wrote: After three years of working to configure Sumon Sinha's deturbulator tapes for my Standard Cirrus, we finally brought it to Caddo Mills for one of those Johnson flight test evaluations. He and Jeff Baird flew it six times with those shiny silver strips on the wings, then three times without. What did they learn? Come to the Convention in Memphis to find out. Dick, as usual, will tell it straight. Will you laugh? Will you be dumbfounded? Will you believe? Jim Hendrix It is nice, but will it work on something other than an antique glider? Is it better than just putting on zig-zag tape? The tests are interesting, but mean nothing without direct comparisons to standard treatments and on a modern airfoil. |
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Sinha Deturbulators: Flight Test Evaluation
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Sinha Deturbulators: Flight Test Evaluation
The point is well taken that the Cirrus has a rather thick "first generation
glass" profile. It does produce both top and bottom separation bubbles, and these tend to move, making the exercise of removing them more difficult. This is why you will seldom see a std Cirrus with deturbulator tape - it does not appear to work very well except at specific speeds. I agree it may be harder to show large improvements on better behaved airfoils, but I suspect the old Wortman is a good place to find out if it works in difficult conditions. I presume Dr Sinha had a reason for choosing it beyond availability. In fact it does not have a separation bubble, but will have a transition bubble (If it had a separation bubble no one would want to fly it) The Laminar transition is relative stable and moves only about 3% to 5% chord, top and bottom at all normal operating speeds. There are two thing that can help improve "that airfoil" reduce the size of the transition bubble and reduce the thickness of the turbulent boundary layer. That this may be the case can be seen by the rather large improvement in lower speeds and less so at a higher speeds. I doubt a modern airfoil can be improved much in this way. How can a 90% laminar flow surface be improved, compared to the 40% on the Cirrus wing. There is still the top surface of a modern wing airfoil, but even there 66% can easily be obtained. I could see an application right there for a 1% improvement. Since a lot of competitor will spent $1500 plus on winglets to get a 1% point improvement, I would not be surprised to see this enhancement appearing on newer gliders some time in the future on the competition scene, if it works, the price is right and is easily maintained. Udo |
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Sinha Deturbulators: Flight Test Evaluation
On Jan 1, 10:36 am, "Udo" wrote:
The point is well taken that the Cirrus has a rather thick "first generation glass" profile. It does produce both top and bottom separation bubbles, and these tend to move, making the exercise of removing them more difficult. This is why you will seldom see a std Cirrus with deturbulator tape - it does not appear to work very well except at specific speeds. I agree it may be harder to show large improvements on better behaved airfoils, but I suspect the old Wortman is a good place to find out if it works in difficult conditions. I presume Dr Sinha had a reason for choosing it beyond availability.In fact it does not have a separation bubble, but will have a transition bubble (If it had a separation bubble no one would want to fly it) The Laminar transition is relative stable and moves only about 3% to 5% chord, top and bottom at all normal operating speeds. There are two thing that can help improve "that airfoil" reduce the size of the transition bubble and reduce the thickness of the turbulent boundary layer. That this may be the case can be seen by the rather large improvement in lower speeds and less so at a higher speeds. I doubt a modern airfoil can be improved much in this way. How can a 90% laminar flow surface be improved, compared to the 40% on the Cirrus wing. There is still the top surface of a modern wing airfoil, but even there 66% can easily be obtained. I could see an application right there for a 1% improvement. Since a lot of competitor will spent $1500 plus on winglets to get a 1% point improvement, I would not be surprised to see this enhancement appearing on newer gliders some time in the future on the competition scene, if it works, the price is right and is easily maintained. Udo To further emphasize Udo's point, for the Antares: The boundary layer remains laminar up to 95% of the wing chord on the lower surface of the wing, at which point turbulent flow is triggered using turbulator tape in order to avoid laminar separation bubbles. Research performed for Lange Flugzeugbau have shown that there is no discernable difference in performance between a well designed turbulator tape and triggering the boundary layer through blowing. On the on the upper surface, the boundary layer remains laminar up to 75% of the wing chord. This is the highest value currently available. How much savings could be obtained in this case, and what would be its impact on the glider performance ? Perhaps someone more expert than I could calculate this. We could ask Loek Boermans perhaps... Best Regards, Dave |
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Sinha Deturbulators: Flight Test Evaluation
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#10
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Sinha Deturbulators: Flight Test Evaluation
Udo wrote:
The point is well taken that the Cirrus has a rather thick "first generation glass" profile. It does produce both top and bottom separation bubbles, and these tend to move, making the exercise of removing them more difficult. This is why you will seldom see a std Cirrus with deturbulator tape - it does not appear to work very well except at specific speeds. I agree it may be harder to show large improvements on better behaved airfoils, but I suspect the old Wortman is a good place to find out if it works in difficult conditions. I presume Dr Sinha had a reason for choosing it beyond availability. In fact it does not have a separation bubble, but will have a transition bubble (If it had a separation bubble no one would want to fly it) The Laminar transition is relative stable and moves only about 3% to 5% chord, top and bottom at all normal operating speeds. There are two thing that can help improve "that airfoil" reduce the size of the transition bubble and reduce the thickness of the turbulent boundary layer. That this may be the case can be seen by the rather large improvement in lower speeds and less so at a higher speeds. I doubt a modern airfoil can be improved much in this way. How can a 90% laminar flow surface be improved, compared to the 40% on the Cirrus wing. There is still the top surface of a modern wing airfoil, but even there 66% can easily be obtained. I could see an application right there for a 1% improvement. Since a lot of competitor will spent $1500 plus on winglets to get a 1% point improvement, I would not be surprised to see this enhancement appearing on newer gliders some time in the future on the competition scene, if it works, the price is right and is easily maintained. Udo Sorry for bad terminology Udo. My lack of aerodynamics taxonomy. Laminar to turbulent transition - I used the separation word where I meant transition bubble. Can refer you to the discussion on http://www.standardcirrus.org/ in the Issues Turbulators section. The authors (Jim Hendrix et al.) refer to separation bubbles there, but only for refference - I used it indiscriminately. All I know is the nice laminar flow falls apart and this moves. I have only inspected 8 different aircraft, so can't claim tobe a world expert on the Cirrus, but so far none that I have seen have turbulators. I draw the (Possibly incorrect) conclusion that they are not worth it on the airfoil... |
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