hyatt regency, san francisco, california > 06-june-06 slide 1 > 24 th applied aerodynamics...

> 24th Applied Aerodynamics Conference > A. KrumbeinHyatt Regency, San Francisco, California > 06-June-06

Automatic Transition Prediction and Application to 3D High-Lift Configurations

Andreas KrumbeinGerman Aerospace Center - DLRInstitute of Aerodynamics and Flow Technology, Numerical Methods


Outline

Outline


Introduction

Introduction

Aircraft industry requirements:

RANS based CFD tool with transition prediction

Automatic, no intervention of the user

Reduction of modeling based uncertainties

Accuracy of results from fully turbulent flow or flow with prescribed transition often not satisfactory

Improved simulation of the interaction between transition locations and separation


Introduction

Different approaches:

RANS solver + stability code + eN method

RANS solver + boundary layer code + stability code + eN method

RANS solver + boundary layer code + eN database method(s)

RANS solver + transition closure model or transition/turbulence model


Introduction

Objectives of the talk:

Documentation of the 1st application of the complete system to an industrially relevant aircraft configuration with a multi-element wing

Documentation of the results for different flow conditions: fully turbulent flow, flow with prescribed and predicted transition

Demonstration that the technique is ready to be applied to complex configurations

Demonstration that the underlying procedure yields reasonable results for a complex configuration


Transition Prediction Coupling Structure

Coupling Structure

cycle = kcyc


Coupling Structure

Transition Prediction Module:

Laminar boundary-layer method for swept, tapered wings (conical flow)

eN database-methods for Tollmien-Schichting and Cross Flow instabilities

Laminar separation approximates transition if transition downstream of laminar separation point

2d, 2.5d (infinite swept) + 3d wings

Single + multi-element configurations

N factor integration along chordwise gridlines

Attachment line transition, by-pass transition & transition inside laminar separation bubbles not yet covered


Coupling Structure

Structured RANS solver FLOWer:

3D RANS, compressible, steady/unsteady

Structured body-fitted multi-block meshes

Finite volume formulation

Cell-vertex and cell-centered spatial discretizations schemes

Central differencing, 2nd & 4th order artificial dissipation scaled by largest eigenvalue

Explicit Runge-Kutta time integration

Steady: local time stepping & implicit residual smoothing, embedded in a multi-grid algorithm

eddy viscosity TMs (Boussinesq) & alg./diff. RSMs


PTupp(sec = 1)

PTupp(sec = 2)

PTupp(sec = 3)

Coupling Structure

Transition Prescription:

Automatic partitioning into laminar and turbulent zonesindividually for each element

Laminar points: St,p 0

Independent of topology

PTupp(sec = 4)


Test Cases

Test CasesKH3Y geometry (DLR F11 model)

Half-model with Airbus A340 fuselage

Wing-body with full span slat and flap high-lift system

Landing configuration: S = 26.5°, F = 32.0°

MeasurementsEuropean High Lift Programme (EUROLIFT), partly funded by EU

Airbus LSWT (Bremen, Germany)

Re = 1.35 mio., M = 0.174

Transition band on fuselage, 30mm downstream of the nose


Test CasesComputations = 10.0° and 14.0°

Fully turbulent, prescribed & predicted transition

Spalart-Allmaras one-equation TM with Edwards & Chandra mod.

97 blocks, 5.5 mio. points, 96.500 on surface

Transition prediction in sections: 11 on slat 13 on main wing 13 on flap

Calibration of critical N factors: = 10°, hot film on main wing upper side at 68% span (xT/c)main = 0.08

NTS = 4.9

No indications for CF NCF = NTS


Test Cases

‘Point transition‘ (no transitional flow model)

Prescribed transition lines:

hot film data slat &main wing 68% span

= 10°, upper side = 10°, lower side

= 10.0° = 14.0°

elem upper side lower side upper side lower side

slat (xT/c)slat = 0.21 at TE (xT/c)slat = 0.11 at TE

main (xT/c)main = 0.08 at TE (xT/c)main = 0.05 (xT/c)main = 0.15

flap beneath main TE at TE beneath main TE at TE


Results

= 10°, upper sideprescribed

= 10°, upper sidepredicted

= 10.0°, upper side: laminar surface regions

Computational Results


Results

= 10°, lower sideprescribed

= 10°, lower sidepredicted

= 10.0°, lower side: laminar surface regions


Results

= 14.0°, upper side: laminar surface regions

= 14°, upper sideprescribed



Results

= 14.0°: laminar surface regions & transition labels

TSTS

TS

TS

TS


CF

CF

CF

CF

= 14°, lower sidepredicted


Results

Comparison ofprescribed & predicted transition lines



section of the hot films

calibration point for NTS


ResultsComparison ofcp-distributions: = 0.20, 0.38, 0.66, 0.88

= 14.0°


Conclusion

Conclusion The complete coupled system (RANS solver & transition prediction module) was succesfully applied to a complex aircraft configuration of industrial relevance WB with 3-element high-lift system

The predicted transition lines are reasonable and quite different from estimated ones based on an experiment

But, they are of preliminary character:Transition prediction module does not yet cover all transition mechanisms which can occur in 3d high-lift flows

Transition inside laminar separation bubbles, attachment line transition & by-pass trasition can not be detected

More validation on complex configurations necessary

It seems to be evident that transition inside laminar separation bubbles is of high importance

It was shown that a fully turbulent simulation or an estimation of the transition lines can result in significant deficiencies


Further comparisons for the current tast cases:Skin friction lines vs. flow visualizations

Global coeffcients: lift & drag

More validation cases, e.g. DLR F5 wing → transonic test case & other more complex test cases

Empirical criteria for: - transition inside laminar separation bubbles - attachment line transition - bypass transition

Incorporation of a fully automated linear stability code into the transition prediction module → alternative for database methods

Consideration of relaminarization

Acknowledgments: Work carried out in EUROLIFT II project, partly funded by EU Computational grid provided by Airbus Germany

Outlook

Outlook

hyatt regency, san francisco, california > 06-june-06 slide 1 > 24 th applied aerodynamics...

Documents

bypass transition transition

separation slide

prescribed transition

aerodynamics conference

cyc slide

transition locations

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