Physics of Operation Electrostatic Body Force Steps to model actuator in flow Body Force, fb(x,t)

Physics of Operation Electrostatic Body Force Steps to model actuator in flow Body Force, fb(x,t)

Physics of Operation Electrostatic Body Force Steps to model actuator in flow Body Force, fb(x,t)

Johnson, Brian, Managing Editor has reference to this Academic Journal, PHwiki organized this Journal PLASMA-ENHANCED AERODYNAMICS – A NOVEL APPROACH AND FUTURE DIRECTIONS FOR ACTIVE FLOW CONTROL Thomas C. Corke Clark Chair Professor University of Notre Dame Center as long as Flow Physics in addition to Control Aerospace in addition to Mechanical Engineering Dept. Notre Dame, IN 46556 Ref: J. Adv. Aero. Sci., 2007. Presentation Outline: Background SDBD Plasma Actuators Physics in addition to Modeling Flow Control Simulation Comparison to Other FC Actuators Example Applications LPT Separation Control Turbine Tip-gap Flow Control Turbulent Separation Control Summary Single-dielectric barrier discharge (SDBD) Plasma Actuator High voltage AC causes air to ionize (plasma). Ionized air in presence of electric field results in body as long as ce that acts on neutral air. Body as long as ce is mechanism of flow control. Ref: AIAA J., 42, 3, 2004 The SDBD is stable at atmospheric pressure because it is self-limiting due to charge accumulation on the dielectric surface.

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Flow Response: Impulsively Started Plasma Actuator Phase-averaged PIV Long-time Average Example Application: Cylinder Wake, ReD=30,000 OFF ON Video Physics of Operation Electrostatic Body Force D – Electric Induction (Maxwell’s equation) (given by Boltzmann relation) solution of equation – electric potential Body Force

Current/Light Emission ~ (t) Current/Light Emission ~ (x,t) Voltage t/T More Optimum Wave as long as m Electron Transport Key to Efficiency a b c d

Steps to model actuator in flow Space-time electric potential, Space-time body as long as ce Flow solver with body as long as ce added Space-Time Lumped Element Circuit Model: Boundary Conditions on (x,t) Electric circuit with N-sub-circuits (N=100) Ref: AIAA-2006-1206 Space-time Dependent Lumped Element Circuit Model (governing equations) Voltage on the dielectric surface in the n-th sub-circuit Plasma current air capacitor dielectric capacitor

Model Ip(t) Experiment Illumination Model Space-time Characteristics Plasma Propagation Characteristics Effect of Vapp dxp/dt vs Vapp (xp)max vs Vapp Model Model Plasma Propagation Characteristics Effect of fa.c. dxp/dt vs fa.c. (xp)max vs fa.c. Model Model

Numerical solution as long as (x,y,t) Model provides time-dependent B.C. as long as Body Force, fb(x,t) Normalized fb(x,t) t/Ta.c.=0.2 t/Ta.c.=0.7 Example: LE Separation Control Computed cycle-averaged body as long as ce vectors NACA 0021 Leading Edge

Example: Impulsively Started Actuator t=0.01743 sec Velocity vectors 2 = -0.001 countours Example: AoA=23 deg. Steady Actuator U =30 m/s, Rec=615K Comparison to Other FC Actuators SDBD plasma actuator is voltage driven, fb~V7/2. For fixed power (I·V), limit current to maximize voltage. Low ohmic losses. Flow simulations require body as long as ce field (not affected by external flow, solve once as long as given geometry). “Zero-mass Unsteady Blowing” generally uses voice-coil system. Current driven devices, V~I. Losses result in I2R heating. Flow simulations require actuator velocity field (flow dependent).

Maximizing SDBD Plasma Actuator Body Force At Fixed Power Sample Applications LPT Separation Control Turbine Tip-Clearance-Flow Control Turbulent Flow Separation Control A.C. Plasma Anemometer LPT Separation Control Span = 60cm C=20.5cm Plasma Side Flow Pak-B Cascade Ref: AIAA J. 44, 7, 51-58, 2006 AIAA J. 44, 7, 1477-1487, 2006

Johnson, Brian Freedom Communications - Phoenix Managing Editor

Plasma Actuator: x/c=0.67, Re=50k Actuator Location Steady Actuator Sep. Ret. Plasma Actuator: x/c=0.67, Re=50k Deficit Pressure Loss Coeff. vs Re 200% 20% Base Flow Unsteady Plasma Act. Document tip gap flow behavior. Investigate strategies to reduce pressure- losses due to tip-gap-flow. Passive Techniques: How do they work Active Techniques: Emulate passive effects Turbine Tip-Clearance-Flow Control Approach: Reduce losses associated with tip-gap flow Objective: Ref: AIAA-2007-0646

Experimental Setup Flow Pak-B blades: 4.14” axial chord Under-tip Flow Morphology t/g =2.83 t/g =4.30 g/c=0.05 Separation line: Receptive to active flow control. Tip-flow Plasma Actuator Re=500k z/span Unsteady Excitation Response Shear Instability: 0.01Johnson, Brian Managing Editor

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