High-Fidelity Multi-Disciplinary Simulation · Service ! Excellence High-Fidelity Multi-Disciplinary Simulation 2014 Dr. Miguel Visbal Principle Research Aerospace Engineer Aerodynamic

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High-Fidelity Multi-Disciplinary Simulation

2014

Dr. Miguel Visbal Principle Research Aerospace Engineer

Aerodynamic Technology Branch Aerospace Vehicles Division (RQV)

Aerospace Systems Directorate

High-Fidelity Multidisciplinary Simulations: Background & Motivations

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High-‐fidelity first-‐principles simulation attributes: üAccurate & truly predictive üProvides fundamental understanding of flow mechanisms üLeverages flow receptivity for enhanced system performance üCost-‐effective approach for “computational experimentation” ü Provides guidance to physics-‐based design-‐oriented approaches

• Spatial & time resolved •Enabled by High-‐Performance Computing •Experimental/ computational synergistic comparisons

ü  Challenges persist in the accurate numerical simulation and understanding of dynamic multi-‐physics phenomena relevant to aerospace vehicles, e.g. transition, turbulence, separated flows, non-‐linear aero-‐elasticity, flow control, aero-‐optics, aero-‐acoustics

ü  Complex non-‐linear multi-‐disciplinary physics critical to FAD, EE, SUAS ü  Failure to account for complex multi-‐disciplinary physics impacts system performance, reliability & life-‐cycle costs

DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059

Hierarchy of Viscous Flow Simulation

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Direct Numerical Simulation (DNS)

Num

eric

al A

ccur

acy

Large-Eddy Simulation (LES)

Hybrid RANS/LES

Implicit LES (ILES)

ü Unsteady loading ü Aero-elasticity ü Active flow control ü Transition ü Aero-optics ü Acoustics

Reynolds Averaged Navier-Stokes (RANS)

ü Mean flow üsteady loads

Reduced-Order Methods (ROM)

Tim

e-O

n-St

atio

n (h

rs)

70

60

50

40

30

20

10 Current-Day Technology

Extend Laminarr Flow

Advanced Structures

2015 SensorCraft

Acttiive Aerroelasttic Wing

AAddapapttiivvee StStrrucuctturesures

Flow Conttroll

Structural Anttennas

Computtattiional Methods

Rapid Assessment Fine-scale unsteadiness


Computational Framework

4 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059

Our Aim

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Discover, Develop, Demonstrate & Transi3on: ü  High-‐fidelity solu3ons & approaches ü  Fundamental understanding ü  Flow control strategies of complex physical phenomena in support of USAF’s

dominant aerospace vehicles


Synergistic Collaborative Structure

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In-house team Dr. M. Visbal (Lead) Dr. D. Rizzetta Dr. R. Gordnier Mr. C. Barnes (Co-Op) Dr. D. Garmann (OAI) Dr. M. White (OAI) Dr. P. Morgan (OAI)

AFOSR Dr. D. Smith NRC

Industry GE Research

Academia UM MSU Lehigh Stanford ERAU ….

Summer Faculty

International Bath Univ. (UK) RTO ECL (France)

DoD HPCMO

NASA DARPA

ARO

RQV RQH


Product-Driven Research Focus

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Broad speed regime : 0.1 < Mach < 3.0


Unsteady Separation & Dynamic Stall

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ü  Dynamic stall is induced by large excursions in angle of attack due to surface motion or incoming gusts.

ü  Aggressive use of laminar flow over lightweight structures for improved energy efficiency brings about the potential for unforeseen interactions excited by incoming gusts.

ü  Coupling of large excursion of transition location, unsteady separation and elastic response may severely impact vehicle dynamics.

ü  Generation of abrupt unsteady loading, noise & vibration ü  Problem has defied prediction using standard techniques.

ü  Outstanding issues: effects of transition & compressibility at realistic Reynolds number

OBJECTIVES üPerform path-‐Uinding high-‐Uidelity LES at increased Re üProvide fundamental understanding of unsteady separation processes üIdentification strategies for effective Ulow control -‐ precursor states for sensing & control with rapid response actuators

ü  Discover unforeseen transition-‐motion induced vehicle response with significant implications for energy efUiciency

ü  Guide reduced-‐Uidelity approaches ü  Transition/ leveraging thru army rotorcraft research


Onset of Unsteady Separation & Dynamic Stall Over Pitching Airfoil

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U

α (t)

Ω SD7003 section

Ωo+ = Ω c /U = 0.05

Minf = 0.1 Rec = 0.5 x 106

αo = 4ο


Spatio-Temporal Distribution of Surface Pressure

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transition

x

-‐Cp DSV

SLV

-‐Cp

α = 4o

α = 30o

LE suction collapse

DSV

LSB pressure plateau


Role of Laminar Separation Bubble

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Low-‐pass Oiltered near-‐wall velocity


Exploration Dynamic Stall Flow Control

12 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. 88ABW-2014-3059

Control of Dynamic Stall Using HF Pulsed Actuation

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Baseline Forced

Leverage OSU experimental/comp plasma flow control research


Streamwise-Oriented Vortex Interactions with Rigid & Flexible Wings

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ü  Homogeneous/heterogeneous, close/extended formation flight are envisioned as a potential technology for reduced fuel consumption & improved range; important to operations with limited forward presence.

ü  Outstanding issues include: transonic effects at high subsonic speeds, buffeting, coupling of non-‐linear flow phenomena near the wing tip with structural flexibility, severe dynamic load environment with impact on drag reduction beneOits and life-‐cycle fatigue.

ü  Study canonical interaction to provide insight into the underlying physics of vortex-‐induced separation & buffeting and role of aero-‐elastic coupling

Multiple modes of interaction identified: dipole formation, loss of vortex coherence & vortex bifurcation

Incident vortex

Static aeroelastic deflection modifies interaction thru repositioning of incident vortex

Rigid wing Flexible wing


Flow/Acoustic Interactions on SUAS

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ü  Close-‐range ISR dictates the introduction of SUAS’s ü  Need to remain undetected for low-‐altitude operation in presence of moderate gusts ü  Vehicle size/speed result in transitional flows which may give rise to tonal-‐noise emission

compromising location due to aural detection ü  Difficult to do experimentally due to wind tunnel environment

OBJECTIVES: ü  Improve understanding/prediction of noise generation in transitional/turbulent flows

ü  Study role of laminar separation and transition (T-‐S waves) on resonance and tonal noise generation

ü  Study impact of disturbances (gusts, maneuvering, deUlections) on sound radiation

ü  Reveal approaches for noise abatement ü  Guide design-‐oriented approaches

Canonical conOigurations High-‐Oidelity overset simulations

Leverage OSU acous3c analysis tool development


Example of Sound Radiation During Onset of Unsteady Separation Over Pitching Airfoil

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x/c = 0.01

LE separation

transition

x/c = 0.2

DSV

α = 18.6o


Plasma-Based Control of Transitional Flows

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ü  Plasma-‐based flow control techniques offers potential for manipulation of transitional/turbulent flows in future vehicles

ü  BeneOits include: delay/induce transition, drag and noise reduction ü  Strategies for effective control need to be explored ü  Active flow control requires high-‐fidelity physics-‐based approaches

Objectives ü  Explore flow control strategies for canonical conUigurations including control of transition on upswept and swept wing sections using several plasma-‐based approaches

üImproved strategies for transition manipulation in drag and noise reduction applications üControl of dangerous Ulexible vehicle response due to large excursions in transition location

Plasma-‐based control devices & canonical conOigurations

Leverage OSU experimental/comp plasma flow control research


Control of Transition Induced by Surface Imperfections

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ü  Surface excrescences such as bumps, mismatched panels, gaps and other imperfection or contamination can generate premature transition to turbulent flow over a wing surface

ü  Critical to system performance (i.e., range, payload, loiter time, fuel consumption)

ü  Difficult to do experimentally

Objectives ü  Perform high-‐Uidelity Uirst-‐principles simulation of canonical conUigurations for T-‐S and crossflow instability ü  Characterize effects of pressure gradient, incoming disturbances ü  Compare to standard lower-‐Uidelity approaches (N-‐factor, PSE) ü Help establish manufacturing or surface damage tolerances

canonical conOigurations


Aero-Optical Aberration in Supersonic Flows

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ü  Laser integration is being considered for FAD concepts ü  Required for targeting, lasercomm, self-‐protection, soft ground targets, etc.. ü  Limited knowledge is available on aero-‐optical aberration in supersonic flows ü  This brings uncertainty to current HEL-‐FAD trade space studies

OBJECTIVES: ü  Characterize aero-‐optical aberration in canonical transonic/supersonic flows relevant to HEL-‐FAD integration

ü  Characterize aberration effects of post-‐shock boundary layer and shock motion (jitter)

üProvide guidance to HEL-‐FAD trade space studies üEstablish computational requirements for reliable aero-‐optic prediction üSuggest strategies for aberration mitigation

canonical conOigurations Previous emphasis: ATL-‐type turrets & shear layers

Standard grid Aero-‐optics grid


Response of Flexible Panels in Supersonic Flow

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ü  Supersonic low over elastic surfaces may give rise to complex interactions leading to limit-‐cycle oscillations, fatigue and acoustic radiation

ü  Important to supersonic aircraft and hot descent of hypersonic vehicles

ü  Complex coupling of deformations with transition and separation due to shock impingement

ü  Impacts vehicle performance due to weight considerations

canonical conOigurations

Shock impingement

Coupling of transition with surface vibrations

Flow parameters Mach No.,

p3 / p1 (or σ ) Re , δ / a, pc , xi /a

Large number of Uluid/structural parameters

Objectives: ü  Explore complex dynamics of flexible panels in low supersonic flow (M< 2) using LES and simple structural models

ü  Explore effects of shock impingement, non-‐isotropic structure üDiscover new aero-‐elastic instability regimes and potential role of flexibility as passive flow control mechanism üIdentify dangerous panel interactions

Structural parameters λ = ρ2 U3 a /D h / a , µs = 0.1 ; a / b = 0


Oblique Shock Impingement on a Flexible Panel: Inviscid Interaction

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supercritical bifurcation

subcritical bifurcation

M1 = 2, p3/p1 = 1.4, λ = 875

supercritical bifurcation

M1 = 2


Laminar Interactions over a Flexible Panel in Supersonic Flow

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oscillations correlate with stability analysis and is suppressed for a cooled wall

Coupling of instability waves with flexible panel modes

M = 2.0, Rea = 300,000, δ /a = 0.015, λ = 500

Comparison with linear stability analysis rigid flexible

Coupling of panel flexural waves with shear layer modes provides “passive” control of separation

rigid flexible

Laminar SBLI over Ulexible panel p3 / p1 = 1.8, Rea = 120,000, λ = 875



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High-Fidelity Multi-Disciplinary Simulation · Service ! Excellence High-Fidelity Multi-Disciplinary Simulation 2014 Dr. Miguel Visbal Principle Research Aerospace Engineer Aerodynamic