REVOLUTIONARY AERODYNAMICS The Sinha- Deturbulator Sumon K. Sinha, Ph.D., P.E, SINHATECH, 3607 Lyles Drive Oxford, Mississippi /

TRADITIONAL AERODYNAMICS for Maximizing L/D Maintain Laminar Flow Avoid Boundary Layer Separation Maintain Elliptical Spanwise Lift Distribution

MOTIVATION Highest L/D is for Sailplanes (70 for AR of 33 with flaps, 48 for AR of 22 without flaps) L/D Restricted by Limits of Laminar Flow Can we do better than Laminar Flow?

Modified Boundary Layer (Thickness Exaggerated) Deturbulator Modified Velocity Profile Unmodified Velocity Profile SLIP LAYER : Deturbulator Stabilized Viscous Sub-layer with slow Reversed Flow negates Skin Friction Drag and Speeds up Freestream Flow Airfoil The Sinha-Deturbulator Approach

Base Airfoil Airfoil with Deturbulator Transition to Turbulent flow Turbulent Boundary Layer High Skin Friction Laminar Boundary Layer Low Skin Friction Marginally Separated Boundary Layer Alters “Virtual” Shape of Airfoil; Increases Lift Coefficient Deturbulator attenuates Turbulent Mixing Keeps separated regions nearly stagnant Almost Zero Skin Friction (Lower than in Laminar Flow) Thickness of Deturbulator Tape encourages Marginal Separation Dynamic Flow-Flexible- Surface interaction on Deturbulator maintains nearly stagnant regions of marginal separation HOW THE SINHA- DETURBULATOR INCREASES LIFT AND REDUCES DRAG

Boundary Layer Velocity Profiles Showing Effect of Deturbulation

SINHA FLEXIBLE COMPOSITE SURFACE DETURBULATOR (FCSD) Membrane Tension  m S Boundary Layer Flow Flexible Membrane  6  m thick Substrate Base glued to aerodynamic surface High Strips or Ridges Low Strips as needed to fix flexural damping Fundamental Flexural Vibration Mode of Membrane Shown (Amplitude  0.1  m)  m thick Air-Gap (Membrane Substrate) Wing or other aerodynamic body

FLOW-FCSD INTERACTION BEST INTERACTION where  p/  x = 0 FCSD passes oscillation without damping at the Interaction frequency : f = U/s Attenuates other frequencies This stabilizes the shear layer and mitigates turbulent dissipation

MODIFICATION OF TURBULENCE BY FLEXIBLE SURFACE SPECTRA OF STREAMWISE VELOCITY FLUCTUATIONS With (top) and Without (bottom) Flexible-Surface Interaction for Separated Flow over a Cylinder in Crossflow for Re = 150,000, M = 0.05 at θ = 90º from stagnation (From: Sinha and Wang, 1999, AIAA Paper ) INTERACTION FREQUENCY f = U/s With Interaction Without Interaction

TESTS ON NLF 0414F WING AFW or FCSD BL-Mouse Global GT-3 Trainer

Transition from AFW to FCSD Unexcited AFW produced a boundary layer profile very similar to the excited AFW. Difference in percentage drag reduction is minimal. FCSD Simplifies the manufacturing and installation procedure. More pragmatic on retrofitting existing aircrafts CLEAN WING TRIPPED FLOW w FCSD AFW FCSD GT-3 WING BOTTOM VEL 0.8C

DETURBULATOR CLOSE UP & SURFACE OIL FLOW PATTERNS LSB TRANSITION ATTACHED TURBULENT FLOW FCSD MODIFIED SLIP LAYER CLOSE UP OF FCSD

TESTS ON STANDARD CIRRUS SAILPLANE TO IMPROVE L/D Drag Pressure Sensors Gross Weight: 728 lbs Best L/D: 52-kts Wing Loading: 6.8 lb/ft 2 Aspect Ratio: 22.5

C L change 0.25 to 0.62 C D change from to L/D change 17 to 89

SKIN FRICTION REDUCTION

Automobile & Truck Drag Reduction: Increased Highway miles/gallon Stagnant Wake

Mean and RMS Velocity Fluctuations Behind Truck Cab Deturbulator Reduces Mean and Fluctuation Velocities (h/h-cab 0.5 to1.2). Confirmation that wake stagnates

Minivan Gas Mileage Increase

Sink Rates with Modified Full Span FCSD Treatment

L/D Improvement with Modified Full Span FCSD Treatment

SUMMARY OF REVOLUTIONARY FCSD AERODYNAMICS FCSD Reduces Turbulence Creates “Slip Layer” Reduces Skin Friction Increases Lift Reduces Induced and Parasitic Drag Across Speed Range. Increased Best Sailplane L/D by 18 % (Johnson Tests 2006) Max Sailplane L/D increase 30% Max Section L/D increase (Low-Re) ~ 400%

OTHER Important ISSUES Consistency Robustness Integration with Wing at the Design stage Version – 2 of the Deturbulator solves performance degradation due to moisture. Verified on automobiles. Sailplane test results pending

ACKNOWLEDGEMENTS National Science Foundation NASA Oxford Aero Equipment Global Aircraft Robert Williams DGA

QUESTIONS ?