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Sinha Deturbulator Progress Reports

Progress Articles
9/17/2003 First successful test of Sinha deturbulator on a glider
10/18/2003 Further drag reductions on Standard Cirrus wing
  Baseline polar for performance testing
2/8/2004 Progress Report: SSA Convention in Atlanta
2/28/2004 First outer-span test
5/27/2004 Wind tunnel goes into operation
8/31/2004 Stereolithography used for wind tunnel wing sections
12/3/2004 First success on upper surface of Standard Cirrus wing
12/12/2004 More success on upper surface of Standard Cirrus wing
2/18/2005 First Sink-Rate Measurement
(revised 3/13/2005)
2/26/2005 Second Sink-Rate Measurement: Some Encouraging Data
3/19/2005 First Parallel Flight - vs. ASW-28
3/19/2005 Measurements with Full Top Surface Deturbulation
9/12/2005 A Performance Endurance Issue
10/29/2005 It’s Deturbulation Time Again
1/9/2006 Paper Presented at AAIA Annual Conference
2/3/2006 Talk Presented at SSA Annual Convention
5/6/2006 Paper Presented at AAIA Flow Control Conference
7/1/2006 Notes on Endurance and the Temperature/Humidity Issue
10/21/2006 Measurements Show 20% Improvement!
(revised 1/3/07)
12/13/2006 Deturbulator Performance Confirmed!
1/2/2007 Calibrated Airspeeds
12/13/2006 Summary of Johnson Flight Test
(revised 2/10/2007)
12/13/2006 Details of Johnson Flight Test
(revised 12/26/2007)
12/01/2007 Johnson Effect Confirmed
(revised 12/26/2007)
06/7/2008 Third Parallel Flight - vs. Diana 1
(revised 8/3/2008)

Publications and Presentations
1/2006 Sailplane Performance Improvement Using a Flexible Composite Surface Deturbulator - Sinha
(PDF, 1174 KB)
6/2006 Drag Reduction of Natural Laminar Flow Airfoils with a Flexible Surface Deturbulator - Sinha
(PDF, 757 KB)
2/2007 Wing Surface Deturbulators - Johnson
(PowerPoint, 2140 KB)
2/2007 Revolutionary Aerodynamics - Sinha
(PDF, 856 KB)
6/2007 Optimizing Wing Lift to Drag Ratio Enhancement with Flexible-Wall Turbulence Control - Sinha
(PDF, 588 KB)
8/2007 Improving Automotive Fuel Efficiency with Deturbulator Tape - Sinha
(PDF, 1368 KB)

More success on upper surface of Standard Cirrus wing (12/12/2004)

Figure 22. Results at the 53" span station after replacing the FCSD.

Today's flight yielded repeated success on the upper wing surface. At the 53" span station, the original FCSD was removed and replaced with another strip that was prefabricated, rather than put together on the wing surface. The new sample produced a solid improvement at low speeds but a slight loss at high speeds compared to old one. We are encouraged to see that reinstalling a strip produced consistent results (Fig. 22).

Fig. 23 shows the aileron station, nine days after the last reported data. No change was made at this station. The improved performance may be due to different aileron deflections.

This was the first time that I saw an unmistakable difference in flight characteristics due to the unbalanced treatment of the wings at high speeds. Previously I had noticed a tendancy to roll left at stall. Today this was more pronounced and began well before the stall. I think this is due to the improved low speed performance of the FCSD at the lowest speeds. However, also today I noticed a definite need to apply greater right stick as the glider increased speed. When applying no side pressure to the stick while diving, the glider consistently rolled left at a rate that increased with speed. The amount of this unbalanced behavior was surprising, considering that only two 12" strips of FCSD were used and only on the upper wing surface. The moment arm for the strip at the aileron station, gives it an advantage in turning the glider.

Since the baseline data for the aileron station was taken with too much turbulence, and since there is a difference in two flights possibly due to aileron deflection variations, I thought it would be interesting to see what the performance would look like if the 12/032004 and 12/12/2004 curves were averaged and the baseline straightened. This is plotted in Fig. 24. I believe this is a pretty good indication of what is actually happening at the 167" span station. We'll see when I get better clean wing data.

Figure 23. Results at the 167" aileron span station nine days later.

At this point, with a number of drag data plots for different surfaces and span stations (Figs. 13, 16, 20, 21, 23, 24), it is interesting to note that the graphs are all generally similar. The best cases show moderate, flat, single digit percentage improvements at low speeds, and performance increasing with airspeed. Generally, the faster you fly the better it works.

Jim Hendrix
Oxford Aero Equipment

Figure 24. Average of 12/03 & 12/12 at 167" station vs straightened baseline.

Airspeeds shown in graphs are instrument calibrated. The aircraft airspeed system is not calibrated. Errors in the Standard Cirrus static/Pitot system bias the data towards higher speeds. This makes polars seem better than they really are. However, this is not an issue when the purpose is only to show comparitive data on the same glider.


© Copyright 2003-2008 Jim Hendrix