(Active) Flow and Noise Control A (Limited) Experimental Perspective - PowerPoint PPT Presentation

Some Challenging Problems in (Active) Flow and Noise Control A (Limited) Experimental Perspective F. S. Alvi Florida State University Florida Center for Advanced Aero-Propulsion Future Directions in CFD Research Aug 6-8, 2012, Hampton Roads, VA

Acknowledgements Collaborators R. Kumar, A. Uzun, M. Y. Hussaini, A. Krothapalli, J. Solomon, J. Gustavsson, W. Oates, Y. Ali, C. Foster, E. Thomas, A. Wiley, H. Lou, V. Kumar, N. Zhuang …. many, many more S. Haack, B. Cybyk (JHU/APL) Research Sponsors AFOSR, AFRL, DARPA, BOEING NASA, ONR, State of Florida and others

Outline • Problems – Supersonic Cavity Flows – Supersonic Impinging Jets – Separated Flows • Experimental & Computational Results – Base Flowfield – Response to Active Control • Steady Microjets – Pulsed Microjet Actuators • Final Thoughts

Cavity Flows Flow – Acoustic Resonance Modified Rossiter’s Model LE TE Large - scale Instabilit y (Heller & Bliss, 1975)  structures Waves Receptivity fU       m r St Acoustic waves /      0 . 5   L 1 1       2 pressure disturbanc es M 1 M     2 k   acoustic waves/pressure disturbances m – Mode no. r – Phase delay k – U conv /U ∞ Resonance observed for Low subsonic to high Supersonic Flows

Cavity Flow Visualizations Subsonic to Transonic Subsonic Flow Phase-locked Schlieren Images, L/D = 2, M = 0.5 Krishnamurti, 1955 (Kegerise, et al., 1999)

Supersonic Cavity Flow M = 2 Cavity Flo w

“Quantitative” Measurements M ∞ = 2, L/D =5 • High unsteady pressures throughout the cavity • Maximum loads near the aft

Velocity Field Phase-Conditioned L/D ~ 5 Large- scale structures       Ensemble Periodic averaged component component Phase-conditioned component

Mach 2 Cavity Flow Effect of Microjet Control baseline with control

Effect of Microjet Control Unsteady Pressure Spectra Control Off Control On Control Off 160 9 dB OASPL reduction Control On 180 20+ dB Tonal reduction Cavity front 150 170 Cavity aft 140 SPL dB 160 SPL dB 130 150 120 140 110 5 10 15 20 130 5 10 15 20 Frequency KHz Zhuang, Alvi, Shih AIAA J , 2006

Effect of Microjet Control Unsteady Velocity, V rms Ensemble-Averaged (using PIV) Microjet Control Baseline LES ( courtesy CRAFT Tech )

Microjets & Slot Jets Simulations* Microjets Velocity Iso-surfaces Slotjets * S. Arunajatesan et al. AIAA Jrnl, 2009

Effect of Microjets : Simulations* Baseline Microjet Control Velocity Iso-surfaces *Courtesy CRAFT Tech

Complex Cavity Flows Microjet Control (40 psi) * S. Arunajatesan et al., AIAA Jrnl , 2009

Unsteady Flow Field - Simulations Slotjets Baseline Microjets Simulations provide insight into the 3-D nature of the flow * S. Arunajatesan et al., AIAA Jrnl , 2009

Supersonic Impinging Jets Pressure Spectra 37-s-nc-h4-GPLPMic.lay 190 NPR 3.7 h = 4.0 No Control Ground Plane Lift Plate Microphone 180 170 160 Prms Instantaneous Shadowgraph 150 140 130 Unsteady Pressure Loads: Ground Plane ~ 185-195 dB 120 Lift Plate ~ 165-175 dB 110 5000 10000 15000 20000 25000 30000 35000 Frequency(Hz)

Control of Impinging Jets Using Steady Microjets 37-s-nc10-h4-GP.lay 190 NPR 3.7 h = 4.0 Ground Plane No Control 100 psi 180 170 Microjets (d m =400  m) Prms 160 d e =27.5 mm 150 Kulite 140 Lift plate 130 5000 10000 15000 20000 25000 30000 35000 Frequency(Hz) 400  m Microjets Unsteady Pressures and Noise Reduced by 4-12+ dB To date, control demonstrated for cold and hot impinging Jets Alvi et al. - AIAA J, 2003, 2006; JFM: 2008; Kumar et al. AIAA J 2009

Experiments & Simulations* Heated Mach 1.5 Jet Mean Axial Velocity (U/U j ) Iso-thermal Jet Total velocity magnitude iso-surfaces • Near-ideally expanded isothermal and heated impinging jet matching experimental cases • Re ≈ 0.9 × 10 6 to 1.3 × 10 6 h/d = 5 • Laminar nozzle inflow conditions • Fully 3-D LES using 200 million grid points *Uzun, A. Hussaini, M. Y. et al, 2010

Experiments & Simulations Heated Mach 1.5 Jet

Identification of Coherent Structures Pressure Iso-Surfaces Associated with Vortex Ring Structures at the Most Amplified Frequency using DMD Uzun, A., Hussaini, M. Y. et al, 2012

Pulsed (Micro)Actuators

Resonance Enhanced Microjet (REM) Actuator Schematic P o Actuator model-Gen 1 NPR= P o /P amb Under expanded source d m =1mm jet Nozzle (d =1mm) h m ( h/d) m =1-2 P amb h/d (1-2) Dime L L/d m =1-5 Cavity (L=1-5 mm) D=1.6 mm Micro Four micro nozzles at nozzles the bottom of the cavity(400 μ m dia) Cylindrical cavity H=h m +L Unsteady Solomon et al. (AIAA J 2010, 2012) Microjets

Actuator Frequency Effect of L/d & NPR Δ NPR ~ 1 changes the frequency from 6-10 kHz • Δ L (4mm) produce Δ f = 52 kHz • Δ L (1mm) produce Δ f = 22 kHz P o L/d= 1 f min = 42 kHz f max = 58 kHz L/d= 2 f min = 24 kHz f max = 36 kHz L/d= 5 f min = 6 kHz f max = 10 kHz h Source jet Impinging Cavity L Configuration

Actuator Performance Summary Δ h=0.6 mm => Δ f= 20 kHz Δ NPR=1 => Δ f= 5 kHz Δ h=0.6 mm => Δ f= 13 kHz Δ NPR=1 => Δ f= 11 kHz Δ h=0.6 mm => Δ f= 12 kHz Δ NPR=1.1 => Δ f= 7 kHz Δ h=0.6 mm => Δ f= 6 kHz Δ NPR=1.1 => Δ f= 5 kHz    1 . 45 Cylindrical geometry St 0 . 4 ( H / d ) St fd / U ideal m ideal m ideal d m : diameter of source jet U ideal : ideally expanded velocity corresponds to the source jet NPR 1 / 2         1 1 0 . 4  2          1 . 45 f ( NPR ) 1 RT ( NPR ) ( H / d )       o d 1    

Phase-Conditioned Images REM: Pulsed Actuator Phase Averaged Instantaneous 100 images averaged at each phase 30 ° - 210 ° ‘filling’ * 240 ° - 0 ° ‘spilling’ * Foster, Alvi et al. AIAA 2011

REM Actuator Simulations & Experiments Uzun, A., Hussaini, M. Y. et al,

REM Actuator Simulations & Experiments

REM Actuator:Simulations

SmartREM Actuator d = 1 mm P 0 NPR = P 0 /P amb Source Jet h Impingement Cavity Cavity V 3.52 kHz Spreader Movable Walls Controlled by Piezo-Stack 3.43kHz Actuators 8/20/2012

Separated Flows (& Control of)* • Separated flow past an airfoil is characterized by frequencies associated with the – wake – shear layer (SL) – separation bubble (SB) – actuation (if applied) • “Lock - on” describes when these components are the same or are harmonics – Harmonics could be evidence of non-linear interactions • Effectiveness of a control strategy may be related to the presence of lock- on [Kotapati et al. 2001] * Courtesy: Cattafesta, Mittal & Rowley 29

Parting Thoughts Experiments  Increasingly sophisticated, providing high-fidelity data  2-D/Stereo/Tomo-PIV /(Plenoptic) => 2 component/3component/volumetric measurements  High-speed/time resolved and Phase conditioned  Synchronous: P, V , ρ…  They provide significant physical insight into flow physics.  Difficult and expensive to run; limited conditions Actuators  A wider array of actuators with a range of control authority and bandwidth  Plasma Based (LAFPA, SJA, DBD); ZNMF (Synthtetic Jets); COMPAct, REM and more  REM: Simple, robust, scale-adapt/able, appropriate complexity & capability  Smart REM: ‘on -the- fly’ frequency control BUT more complex  Still unclear: “which actuator and under what conditions”

Parting Thoughts Simulations  Increasingly sophisticated, provide high-fidelity data for increasingly complex flows  More rigorous validation using better experimental data  Good to excellent agreement (for some cases?)  Provide physical insight into flow physics, provide properties not easily measured.  Difficult and expensive to run; limited conditions  Rarely go beyond experimental conditions? As we Progress  Simulations+Theory used to better explore flow dynamics;l arger range of conditions  Provide guidance for active-adaptive control (that is realistic/feasible ):  Temporal and Spatial requirements (freq., wavelength) for actuation and  Location (where to best place them)  Type of actuation: momentum, body force, thermal…  Provide guidance for (sparse/minimal, practical) sensing requirements  Help develop, simpler/low- order/…, practical models for closed-loop control  Plan experiments and computations together from the start  We need to improve our communication skills