Flow Interactions and                                                                                           Control   ...
2012 AFOSR SPRING REVIEWNAME: Douglas SmithBRIEF DESCRIPTION OF PORTFOLIO:Foundational research examining aerodynamic inte...
Inspiration …                     Parameter boundaries LOW                                                                ...
Inspiration …                  Disciplinary boundaries                                                                    ...
Scientific Challenges                                                                                      Flow Physics   ...
Opportunities …          • Create opportunities in               Gust tolerance/mitigation               Agility        ...
Scientific Challenges                                                                                        Flow Physics ...
Portfolio map                                          Future                           Graham          Fasel            W...
Exploiting the nonlinear dynamics of near-wall                        turbulence for skin-friction reduction              ...
Control of boundary-layer separation for lifting surfaces                                                    H. Fasel, Ari...
AN INTEGRATED STUDY OF SEPARATION CONTROL                                L. Cattafesta (FSU), R. Mittal (JHU), & C. Rowley...
Rotorcraft Brownout – Advanced Understanding Control                    and Mitigation                        G. Leishman,...
Rotorcraft Brownout – Advanced Understanding Control                               and Mitigation                         ...
Development of a Compact and Easy-to-Use 3-D                     Camera For Measurements in Turbulent Flow Fields         ...
Portfolio map                                          Future                           Graham          Fasel            W...
Biological Inspiration  Courtesy of Breuer & Swartz, Brown  DISTRIBUTION A: Approved for public release; distribution is u...
Challenges & Questions        CHALLENGES                                                 QUESTIONSUnsteady, periodic flow-...
Bio-Inspired AerodynamicsHIGH                                          MURI07 3D aero-elastic, dynamic flight  Bio-Inspire...
From Gliding to Powered Flight                         50 million years ago bats evolved from gliding to powered          ...
Effect of Membrane Flexibility on Leading Edge                              Separation                                 R G...
Control of Low Reynolds Number Flows with Fluid-                            Structure Interactions                        ...
Flapping-Wing Vortex Formation and Scaling                                                   M. Ringuette (YIP 2010), Buff...
Three-dimensional Vortex Formation On A Pitching                     Wing        D. Rockwell (Lehigh) & M. Visbal (AFRL/RB...
High-Resolution Computational Studies and Low-Order                  Modeling of Agile Micro Air Vehicle Aerodynamics     ...
Energy Extraction From Unsteady Winds                             Williams (IIT)/ Colonius (Caltech)             Albatross...
Transformational Computing in                Aerospace Science & Engineering  To create transformational approaches in com...
Portfolio map                                          Future                           Graham          Fasel            W...
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Smith - Flow Interactions and Control - Spring Review 2012

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Dr. Douglas Smith presents an overview of his program - Flow Interactions and Control - at the AFOSR 2012 Spring Review.

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Smith - Flow Interactions and Control - Spring Review 2012

  1. 1. Flow Interactions and Control 08 MAR 2012 Dr. Douglas Smith Program Manager AFOSR/RSA Integrity  Service  Excellence Air Force Research Laboratory9 March 2012 DISTRIBUTION A: Approved for public release; distribution is unlimited. 1
  2. 2. 2012 AFOSR SPRING REVIEWNAME: Douglas SmithBRIEF DESCRIPTION OF PORTFOLIO:Foundational research examining aerodynamic interactions oflaminar/transitional/turbulent flows with structures, rigid or flexible,stationary or moving.Fundamental understanding is used to develop integrated controlapproaches to intelligently modify the flow interaction to some advantage.LIST SUB-AREAS IN PORTFOLIO:Flow Physics for ControlFlow Control EffectorsLow Reynolds Number Unsteady AerodynamicsAeromechanics for MAVs DISTRIBUTION A: Approved for public release; distribution is unlimited. 2
  3. 3. Inspiration … Parameter boundaries LOW HIGH TransitionLaminar Flow Turbulent Flow• Smooth & orderly • Disorderly, but asymptotic Affected by … • Roughness • Freestream turbulence DISTRIBUTION A: Approved for public release; distribution is unlimited. 3
  4. 4. Inspiration … Disciplinary boundaries ChemicalNovel Materials Interactions CNT wire array Biology Energy DISTRIBUTION A: Approved for public release; distribution is unlimited. 4
  5. 5. Scientific Challenges Flow Physics for ControlUnsteady FlowLow Rey Control Aero Flow Control Fluid- Structure Interaction DISTRIBUTION A: Approved for public release; distribution is unlimited
  6. 6. Opportunities … • Create opportunities in Gust tolerance/mitigation Agility Hover Integrated lift & thrust • Reconfigurable aircraft • Coordinated flight, swarming • Drag reduction, Enhanced efficiencyRequire an understanding of aerodynamic-structure interactions and control. DISTRIBUTION A: Approved for public release; distribution is unlimited. 6
  7. 7. Scientific Challenges Flow Physics for ControlUnsteady FlowLow Rey Control Aero Flow Control Fluid- Structure Interaction DISTRIBUTION A: Approved for public release; distribution is unlimited..
  8. 8. Portfolio map Future Graham Fasel Wygnanski Flow Physics Jones Work Swartz for YIP Golubev Control BuchholzUnsteady YIP Colonius Dong Flow MaheshLow Rey Ringuette YIP Control Williams Aero Breuer Karagozian Eldredge Edwards Rowley Hedrick Spedding Williamson Thurow Gopalarathnam Mittal GlezerBio-inspiration OL LRIR Bernal Cybyk Cattafesta Alvi Thomson Gregory Visbal LRIR MURI LRIR Deng Ukeiley Sodano Sondergaard Leishman Morris Flow Rempfer Rockwell Hubner Control Shkarayev Gordnier LRIR Fluid- Flow IfjuSnyder Wark Gursul Structure Control Little YIPLRIR Lang Sytsma Koochesfahani Interaction Key to Lines Flow physics & Control Low Reynolds number Flow control collaboration unsteady aerodynamics Flight physics for MAVs PI Co-PI 2012 New Start Applied flow control
  9. 9. Exploiting the nonlinear dynamics of near-wall turbulence for skin-friction reduction M. Graham, Wisconsin Background and objective Recent results• Drag in many aerodynamic flows is dominated by near-wall turbulent flow structures• Approaches to skin-friction reduction often focus on Active manipulation of these structures via suction/blowing or topography (riblets) vorticity• In liquids, dramatic changes in these structures and corresponding high levels of drag reduction (>70%) Hibernating can be achieved by adding long-chain polymers. velocity• Recent discoveries: • polymer stresses suppress normal “active” Turbulent turbulence” but do not affect intervals of Upper branch ECS flow “hibernating” turbulence that exhibit very low Turbulent bursts skin friction, High-drag active turbulent dynamics • hibernating turbulence intervals are found occasionally even without polymer additives. Initial condition drag Low-drag excursions- that becomes hibernation turbulent⇒Goal: Exploit these observations to develop new Basin boundary: boundary control schemes to make these low-drag • lower-branch ECS • edge state Initial condition intervals more frequent and thus reduce overall drag that becomes in aerodynamically important flows. laminar Laminar flow Proposed schematic of the state space dynamics of DISTRIBUTION A: turbulent wall-bounded flow. Approved for public release; distribution is unlimited. 9
  10. 10. Control of boundary-layer separation for lifting surfaces H. Fasel, Arizona0.027 m/s Investigating the transition process of separation bubbles in the presence of freestream turbulence • Experimental observations  description of bubble behavior0.054 m/s separation bubble • Simulations require that freestream turbulence is included to predict exp observation0.087 m/s reattachment Simulation Experiment Profiles of time-averaged u-velocity DISTRIBUTION A: Approved for public release; distribution is unlimited. 10
  11. 11. AN INTEGRATED STUDY OF SEPARATION CONTROL L. Cattafesta (FSU), R. Mittal (JHU), & C. Rowley (Princeton) EXPERIMENTS • Investigation into nonlinear coupling of stalled airfoil Reattached separation (bubble) Koopman a =12° 4 Detached separation 10 • Shear layer probe reveals quadraticλn · v 1) Investigate nonlinear interactions between 5 coupling  nonlinear coupling between 10 these phenomena shear layer and wake instabilities 6 10 Leverage nonlinear interactions for 2) 2 4 6 8 10 12 14 effective control strategies fSB/wake mode (f = 4.45) DYNAMICAL ANALYSIS SIMULATED EXPERIMENTALSL mode (f = 8.90) St » 0.26 St » 0.53Spatial harmonic (f = 13.34) Oscillating structures Fixed frequency structures similar DISTRIBUTION A: Approved for public release; distribution is unlimited. 11
  12. 12. Rotorcraft Brownout – Advanced Understanding Control and Mitigation G. Leishman, Maryland DISTRIBUTION A: Approved for public release; distribution is unlimited. 12
  13. 13. Rotorcraft Brownout – Advanced Understanding Control and Mitigation G. Leishman, Maryland• Rotor wake dynamics “in ground effect” is at the root of the problem• Unsteady, 2-phase, 3-dimensional fluid dynamics problem• Wake impinging on the ground creates: – Transient excursions in flow velocities – Unsteady shear stresses and pressures – Secondary vortical flows and local regions of flow separation – Turbulence Simulated dust clouds using a Lagrangian free-vortex rotor wake method and Lagrangian sediment particle tracking Summary of the six sediment mobilization, uplift, and suspension method (~1012 particles) along with contours of induced mechanisms observed from a bed below a rotor: creep; modified velocity on the ground (note high 3-dimensionality) for a saltation, vortex-induced trapping, unsteady suction pressure dynamic simulation of a helicopter landing over a surface effects, secondary suspension, particle bombardment/splash release; distribution is unlimited. covered with a sediment bed DISTRIBUTION A: Approved for public 13
  14. 14. Development of a Compact and Easy-to-Use 3-D Camera For Measurements in Turbulent Flow Fields B Thurow, Auburn Conventional Plenoptic imaging imaging Lense-let arrayConventional 2-D Imaging Systems Lightfield Imaging 2-D information neglects inherent 3-D nature Plenoptic camera records both theof turbulent flows position and angle of light rays that Camera integrates angular information, which enter the cameraleads to depth-of-field and blur Eliminates the need for complex, Reduced aperture (restricted angular expensive multi-camera arrangementsinformation) leads to low signal levels  Dense sampling of 3-D scene Near Mid Far DISTRIBUTION A: Approved for public release; distribution is unlimited. 14
  15. 15. Portfolio map Future Graham Fasel Wygnanski Flow Physics Jones Work Swartz for YIP Golubev Control BuchholzUnsteady YIP Colonius Dong Flow MaheshLow Rey Ringuette YIP Control Williams Aero Breuer Karagozian Eldredge Edwards Rowley Hedrick Spedding Williamson Thurow Gopalarathnam Mittal GlezerBio-inspiration OL LRIR Bernal Cybyk Cattafesta Alvi Thomson Gregory Visbal LRIR MURI LRIR Deng Ukeiley Sodano Sondergaard Leishman Morris Flow Rempfer Rockwell Hubner Control Shkarayev Gordnier LRIR Fluid- Flow IfjuSnyder Wark Gursul Structure Control Little YIPLRIR Lang Sytsma Koochesfahani Interaction Key to Lines Flow physics & Control Low Reynolds number Flow control collaboration unsteady aerodynamics Flight physics for MAVs PI Co-PI 2012 New Start Applied flow control
  16. 16. Biological Inspiration Courtesy of Breuer & Swartz, Brown DISTRIBUTION A: Approved for public release; distribution is unlimited. 16
  17. 17. Challenges & Questions CHALLENGES QUESTIONSUnsteady, periodic flow-fields To what extent can the flow be treated as quasi-steady? Can the flow be treated as 2-DThree-dimensional flow-fields along the span of the wing? What can we learn from these 2-D treatments?Low Reynolds number flows How good are inviscid approximations?Laminar-transitional flows How well must these flows be resolved?Separation & Leading-edge vortices Why separated flow? Do LEVs have universal formation scaling?Wing kinematics How sensitive are the aerodynamics to the kinematics? Rectilinear vs flapping?Wing flexibility What is the role of flexibility in DISTRIBUTION A: Approved for public release; distribution is unlimited. aerodynamic efficiency? modifying 17
  18. 18. Bio-Inspired AerodynamicsHIGH MURI07 3D aero-elastic, dynamic flight Bio-Inspired Neuro-physiological control Flight Evolutionary biology Hubner et al, Alabama Gordnier, AFRL Breuer/Swartz et al, Brown Aerodynamics & Wing Structure Flexibility Surface flexibility/compliance Flow induced vibrations Natural, passive flow control Hi-fidelity Simulations Wood Snyder, AFRL Harvard Source: Wikimedia Commons Visbal, AFRL/Rockwell, Lehigh 3D/wing tip effects Transition to turbulence Rigid Wing Aerodynamics Starting/stopping transients Leading edge vortex formationLOW Universal scaling Ringuette, SUNY-Buffalo OL, AFRL DISTRIBUTION A: Approved for public release; distribution is unlimited. 18
  19. 19. From Gliding to Powered Flight 50 million years ago bats evolved from gliding to powered flapping flight. BUT… • What pressures led from passive gliding to powered flight? • What is the role passive wing deformation or motion in biological flight?Onychonycteris finneyi self-excited oscillations stationary DISTRIBUTION A: Approved for public release; distribution is unlimited. 19
  20. 20. Effect of Membrane Flexibility on Leading Edge Separation R Gordnier, AFRL/RBAC Rigid, Flat Wing Rigid, Flexible Wing Cambered WingMembrane Flexibility: Reduces the extent of leading edge separation CL CD L/D Cmy Enhances lift at the cost of Rigid-Flat 0.965 0.235 4.112 -0.160 increased L/D Reduces nose down pitching Rigid-Cambered 1.020 0.269 3.794 -0.140 moment Flexible 1.024 0.262 3.903 -0.122 Membrane DISTRIBUTION A: Approved for public release; distribution is unlimited. 20
  21. 21. Control of Low Reynolds Number Flows with Fluid- Structure Interactions I Gursul, BathObjectives: Rectangular Elliptical Elliptical Rectangular b/c=2 b/c=2 b/c=1 b/c=1(i) exploit fluid-structure interactions to delay stall and increase lift of airfoils and wings at low Reynolds a numbers(ii) improve maneuverability and gust response of MAVs.Approach: b(i) simulate aerolastic vibrations by means of small-amplitude plunging oscillations of airfoils and wings(ii) develop flexible wings based on this knowledge. c a b d d DISTRIBUTIONcA: Approved for public release; distribution is unlimited. 21
  22. 22. Flapping-Wing Vortex Formation and Scaling M. Ringuette (YIP 2010), BuffaloObjective … • find a scaling parameter connecting the vortex formation/strength to the kinematics, which should relate to important force features if a formation-parameter scaling holdsApproach … • characterize the general 3-D vortex topology • track how the vortex loop evolves in space and time • find the effects of non-dimensional parameters such as AR, Rossby no., on strength, vortex loop stability CCD camera Top view Stage Plate θ Not to scale Laser • Tip vortex effect • TV flow anchors insufficient to anchor LEV to plate, LEV, observe prevents shedding shedding & eventual • Colors indicate flow breakdown of vortex along vortices structure AR=2, =48° AR=4, =48° DISTRIBUTION A: Approved for public release; distribution is unlimited. 22
  23. 23. Three-dimensional Vortex Formation On A Pitching Wing D. Rockwell (Lehigh) & M. Visbal (AFRL/RBAC)Experiments Simulations Vortex structure Surface pressure DISTRIBUTION A: Approved for public release; distribution is unlimited. 23
  24. 24. High-Resolution Computational Studies and Low-Order Modeling of Agile Micro Air Vehicle Aerodynamics J. Eldredge, UCLAOBJECTIVES• Develop low-order phenomenological models (< ~10 dof for flapping wing flight,• Examining a progression of canonical wing motions, with both rigid and flexible wings.• Simultaneously explore the physics of canonical wing motions using high-fidelity numerical simulations.MAIN ACHIEVEMENTS• Constructed a low-order model based on point vortex dynamics• Successfully demonstrated that model captures force generated by a 2-d flat plate in pitch-up Lift vs Angle of Attack• High-fidelity simulation requires ~1,000,000 degrees of freedom; low-order model requires only 6 RAPID PITCH-UP High-fidelity results Low-order model streamlines Drag vs Angle of Attack DISTRIBUTION A: Approved for public release; distribution is unlimited. 24
  25. 25. Energy Extraction From Unsteady Winds Williams (IIT)/ Colonius (Caltech) Albatross remains aloft indefinitely! Model gliders flying at 400+ mph!! How? … DYNAMIC SOARING!!Albatross Extracting energy from spatial velocity gradients in the wind. apparent Ta Lee of an ocean swell L D Wind gust tilted L Lo OR D Wz Wz Up-gust Down-gust ½ cycle ½ cycle U+wx • Investigate unsteady and nonlinear phenomena relevant to gusts over wings • Without flow control can extract energy from flow • Integrate active closed-loop flow with flight control • Demonstrate benefits of increased range and endurance by extracting energy from gusting flowsWilliams/Colonius DISTRIBUTION A: Approved for public release; distribution is unlimited. 25
  26. 26. Transformational Computing in Aerospace Science & Engineering To create transformational approaches in computing for aerospace science and engineering. “How can we exploit quantum computing architectures specifically to advance aerospace computing?”Applications of QC in Aerospace S&E Quantum Speedup for Turbulent Meyer et al, UCSD Combustion Simulations Givi et al, Pitt Phase Today Fourier Ampl H sim X-form est. amplif LES of Turbulent Tomorrow Reacting Flows QA Ly=x Resolved SGS large scales modelInvestigate QC improvements in… FDF1. Solving systems of ODEs SDE2. OptimizationFuture … of (non)smooth fcns3. Evolving the gnd state of a • Develop quantum sim techniques molecule for stochastic diff eqs (SDEs)PMs: Drs. Douglas Smith & David Stargel, RSA Partners: Drs. Curcic, Fahroo, Luginsland DISTRIBUTION A: Approved for public release; distribution is unlimited. 26
  27. 27. Portfolio map Future Graham Fasel Wygnanski Flow Physics Jones Work Swartz for YIP Golubev Control BuchholzUnsteady YIP Colonius Dong Flow MaheshLow Rey Ringuette YIP Control Williams Aero Breuer Karagozian Eldredge Edwards Rowley Hedrick Spedding Williamson Thurow Gopalarathnam Mittal GlezerBio-inspiration OL LRIR Bernal Cybyk Cattafesta Alvi Thomson Gregory Visbal LRIR MURI LRIR Deng Ukeiley Sodano Sondergaard Leishman Morris Flow Rempfer Rockwell Hubner Control Shkarayev Gordnier LRIR Fluid- Flow IfjuSnyder Wark Gursul Structure Control Little YIPLRIR Lang Sytsma Koochesfahani Interaction Key to Lines Flow physics & Control Low Reynolds number Flow control collaboration unsteady aerodynamics Flight physics for MAVs PI Co-PI 2012 New Start Applied flow control

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