Recent Progress in Advanced Wind Tunnel Boundary Simulation:

NATO AVT-284 Research Workshop

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Joseph H. Morrison & Eric L. WalkerNASA

Alexander J. KrynytzkyThe Boeing Company

Cabot BroughtonNational Research Council-Canada

Workshop Committee

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CO-CHAIRS CANADA Mr. Cabot A. BroughtonNational Research Council Canada

USA Mr. Joseph H. MorrisonNASA Langley Research Center

PANEL MENTOR GERMANY Dr. Andreas SchuetteGerman Aerospace Center (DLR)

TECHNICAL EVALUATOR USA Mr. Alexander Krynytzky

FRANCE Mr. Sylvain MoutonONERA

GERMANY Dr. Markus JacobsDNW German-Dutch Wind Tunnels

Dr. Guido DietzEuropean Transonic Windtunnel

NETHERLANDS Ir. Sinus HegenDNW German-Dutch Wind Tunnels

UK Prof. Andrew RaePerth College UHI

USA Dr. William J. DevenportVirginia Tech

Mr. William SchumanArnold Engineering Development Complex

Dr. Eric L. WalkerNASA Langley Research Center

TECHNICAL COMMITTEE

Background

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• 2-day workshop sponsored by NATO Science and Technology Office (STO) Advanced Vehicle Technology (AVT) Panel

• Held 16-18 April 2018 in Torino, Italy

• Twelve technical presentations, two keynote addresses, six open discussion periods (4.5 hours), technical evaluation presentation

• Objectives:• Evaluate high fidelity CFD simulation of wind tunnel boundaries, other

installation effects including support hardware and compare with established results,

• Develop recommendations for the use of high fidelity simulation of wall boundaries and model support hardware

• Identify key areas requiring further research and development

Workshop Goal and Scope

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Simulation of Wind Tunnel BoundariesWalls, In-flow, Out-flow, Support Systems

Correction to Equivalent Free Air

Experimental Validation of Computational Methods

What is the current state of practice?

What are the limitations?

What improvements are needed?

Workshop Paper Summary (Public Release)

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Ref Authors Title

2 H. C. Lee, T. H. Pulliam, C. L. Rumsey, and J.-

R. Carlson

Simulations of the NASA Langley 14x22 Subsonic Wind Tunnel for the

Juncture Flow Experiment

3 M. J. Smith Large-Eddy-Simulation-Based Wind Tunnel Assessments

4 F. J. M. Wubben and H. Maseland Verification of wind tunnel model support and wall interference

assessments in DNW-HST by CFD simulations

5 V. Hawke, J. Melton, and T. Romer CFD and Experimental Investigation of the NASA Ames 11-Foot

Transonic Wind Tunnel

6 A. Cartieri and D. Hue Using RANS computations to calculate support interference effects on the

Common Research Model

7 P. Chwalowski, W. A. Silva, C. D. Wiesemann,

and J. Heeg

CFD Model Of The Transonic Dynamics Tunnel With Applications

8 W. Devenport, K. Brown, A. Borgoltz, and E.

Paterson; C. Bak, N. Sorensen, A. Olsen, M.

Gaunan, A. Fischer, and C. Grinderslev

Advanced Wind Tunnel Boundary Simulation for Kevlar Wall

Aeroacoustic Wind Tunnels

9 B. Koenig, E. Fares and M. C. N. Wright Lattice Boltzmann Simulation of the ETW Slotted Wall Test Section

10 S. M. Rivers, S. N. Nayani, A. F. Tinetti, S. E.

Brynildsen, and R. J. Ferris

Numerical Study of the High-Speed Leg of the National Transonic

Facility

11 J.-L. Hantrais-Gervois and J.-F. Piat A Methodology to Derive Wind Tunnel Wall Corrections from RANS

Simulations

https://tinyurl.com/AdvWTSimI

Meeting Organization

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• Solid Walls

• Support Systems

• Ventilated Walls

• Corrections

• Validation

Meeting Organization

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• Solid Walls

• Support Systems

• Ventilated Walls

• Corrections

• Validation

Low-Speed Specific/General: Ref. 2

NASA Langley 14’ x 22’; Lee, Pulliam, Rumsey, & Carlson

M = 0.2; Empty Tunnel, Support Interference, Juncture Flow Model

OVERFLOW (RANS)

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Low-Speed Specific/General: Ref. 3

Georgia Tech, NSWCCD 8’x10’; Smith

M ~ 0; Wall Interference; Simple Frigate Shape at 1:50 scale

FUN3D (RANS, URANS, DES/LES)

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Technical Discussion 1: Experimental/Computational Comparisons

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• CFD typically does not set reference flow conditions the same way the wind tunnel does

• Use of internal flow in tunnel to get external flow on test article

• CFD exit boundary conditions are used to match tunnel reference conditions

• Different from free-air CFD• Different from how wind tunnels are operated• Nuances not universally understood

• Need to perform experimental calibration procedures on numerical tunnel

Technical Discussion 1: Experimental/Computational Comparisons

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• Need to understand:• Impact of inflow conditions on CFD solution• Impact of outflow boundary condition on CFD solution• How much of the wind tunnel needs to be modeled in CFD

• Test Section only• Settling chamber + Contraction + Test Section + Diffuser• Entire Circuit• As-built vs. As-designed

• What do we need for measurements?• Inflow uniformity and flow angularity• Outflow (Separation in Diffuser?)• Empty test section turbulence levels? • Uncertainty• What level of detail?

Meeting Organization

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• Solid Walls

• Support Systems

• Ventilated Walls

• Corrections

• Validation

High-Speed General: Ref. 4

DNW-HST;

Wubben & Maseland

M = 0.78; Empty Tunnel, Wall & Support Interference

WIN3VE (Linear Potential), NLR ENFLOW (RANS)

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High-Speed Specific: Ref. 5

NASA Ames 11-ft Unitary; Hawke, Melton, & Romer

M = 0.8, 1.2; Empty Tunnel STAR-CCM (RANS)

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High-Speed Specific: Ref. 6

ONERA S1MA; Cartieri & Hue

M = 0.85; Support Interference; Large Reference Model

ONERA-elsA (RANS)

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Meeting Organization

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• Solid Walls

• Support Systems

• Ventilated Walls

• Corrections

• Validation

High-Speed Specific: Ref. 7

NASA Langley TDT; Chwalowski, Silva, Wieseman, & Heeg

M = 0.5, 0.7, 1.1; Empty Tunnel, Dynamics

FUN3D (RANS)

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Low-Speed Specific/General: Ref. 8

Virginia Tech Stability Wind Tunnel, Denmark Technical University;

Devenport, Brown, Borgoltz, Paterson, Bak, Sørensen, Olsen, Gaunaa, Fischer, & Grinderslev

M ~ 0; Wall Interference

EllipSys (RANS)

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Technical Discussion 2: Use of high fidelity CFD for correction

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• Classical methods dominate for transport aircraft models; various approaches come into play with increasing compressibility effects; conservatism of airframe manufacturers

• Benchmark for validation of CFD approaches: small model in a solid-wall test section -> more challenging cases

• Perspective offered during discussion• Validation of CFD started using WT as “Truth”• Realization that WT has errors may not be the free-air support interference-free

“Truth” • Attempts to circumvent corrections using comprehensive modeling of installed

experiment• Most cases are difficult or challenging, requiring combined efforts of computational

& experimental communities

Technical Discussion 2: Use of high fidelity CFD for correction

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• Where can conventional corrections be trusted? • Usually when they are small (i.e., the model is appropriately sized relative to the

test section)

• High fidelity CFD correction may be needed for complex, unconventional or special situations where models are large • Trust in these methods needs to be demonstrated

High-Speed General: Ref. 9

ETW; König, Fares, & Wright

M = 0.852, 0.865; Wall Interference

PowerFLOW® (Lattice-Boltzman)

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High-Speed General: Ref. 10

NASA Langley NTF;

Rivers, Nayani, Tinetti, Brynildsen, & Ferris

M = 0.7, 0.8, & 0.85; Empty Tunnel, Wall

Interference

USM3D (RANS), PowerFLOW® (Lattice-

Boltzman)

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Technical Discussion 3: Computational Modeling for Validation Experiments

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• How much of the tunnel needs to be represented in the CFD model?

• Inlet contraction required if the boundary layer on test section walls are important • As-built issues

• Downstream end of the test section important for transonic facilities; plenum flow reentry to diffuser

• Modeling past the downstream end of the test section diffuser may be necessary to dampen the response of the flow solver

• Transonic partially open test section: reduced order model of the wall and plenum behavior vs a detailed geometrical representation of the ventilated wall and plenum

• More work required on tunnel jet core flow physics: total pressure gradients, flow angularity, turbulence • Two-fold problem: wind tunnel measurements and CFD evaluation

Technical Discussion 3: Computational Modeling for Validation Experiments

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• CFD techniques for initiating and converging a calculation • Use of wind tunnel controller algorithms

• Role and importance of model deflection measurements & actual wind tunnel surfaces

Meeting Organization

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• Solid Walls

• Support Systems

• Ventilated Walls

• Corrections

• Validation

High-Speed General: Ref. 11

ONERA S2MA; Hantrais-Gervois & Piat

M = 0.7, 0.8, 0.85, 0.9; Empty Tunnel, Wall Interference

elsA (RANS)

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Technical Discussion 4: Use of RANS in the Experimental Process

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• Future applications of RANS level modeling:

• Wall and support interference corrections (Developing)

• Guidance in test planning (Current value added)

• Test execution, data evaluation, and analysis (Developing)

• Combined use of wind tunnel and computational simulation is most useful for research activities addressing new vehicles and technologies

Technical Discussion 4: Use of RANS in the Experimental Process

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• Wind tunnel groups need to incorporate personnel with computational simulation skills into their work flow either by directly hiring that skill into the team, or by training; and vice versa

• RANS support interference corrections may be more valuable than classical or experimental approaches

• Classical wall interference analyses still outperform RANS modeling for many wall interference applications

• Not all tests need corrections; cost-benefit issues for any correction procedures

Meeting Organization

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• Solid Walls

• Support Systems

• Ventilated Walls

• Corrections

• Validation

Technical Discussion 5: Supporting Validation Testing

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• Experimental data should allow discrimination among computational model predictions

• Require collaboration and dialogue between experimentalists and computationalists• e.g., Juncture Flow Model

• Use risk reduction experiments to support CFD validation and ensure capture of proper flow physics • Especially for flows that challenge the predictive model

• Effect of surface roughness is an area requiring better understanding

Technical Discussion 5: Supporting Validation Testing

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• Necessity of CFD processes and analyses to parallel experimental processes • Prioritization of required validation data• Ensuring similarity of temporal and spatial aggregation for comparison

• Cross-training of computationalists and experimentalists

• Responsibility of computationalists to prioritize the data they need from experimentalists

Technical Discussion 6: Path Forward

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• NATO AVT-338 Specialists’ Meeting on Advanced Wind Tunnel Boundary Simulation II • 2.5 day meeting, 15-20 papers + topical discussion• Berlin, Germany• 17-19 May 2021• Call for papers: expected release in Fall 2019

• More cross-training between CFD and ground test technical communities in academia, government, and industry

• Need to improve the integration of the computational and experimental toolsets

AVT-284: https://tinyurl.com/AdvWTSimI