Hyatt Regency, San Francisco, California > 06-June-06 Slide 1 > 24 th Applied Aerodynamics Conference > A. Krumbein Automatic Transition Prediction and Application to 3D High-Lift Configurations Andreas Krumbein German Aerospace Center - DLR Institute of Aerodynamics and Flow Technology, Numerical Methods

Hyatt Regency, San Francisco, California > 06-June-06 Slide 2 > 24 th Applied Aerodynamics Conference > A. Krumbein Outline Introduction Transition Prediction Coupling Structure Test Cases Computational Results Conclusion Outlook Outline

Hyatt Regency, San Francisco, California > 06-June-06 Slide 3 > 24 th Applied Aerodynamics Conference > A. Krumbein 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

Hyatt Regency, San Francisco, California > 06-June-06 Slide 4 > 24 th Applied Aerodynamics Conference > A. Krumbein Introduction Different approaches: RANS solver+ stability code + e N method RANS solver+ boundary layer code + stability code + e N method RANS solver+ boundary layer code + e N database method(s) RANS solver+ transition closure model or transition/turbulence model

Hyatt Regency, San Francisco, California > 06-June-06 Slide 5 > 24 th Applied Aerodynamics Conference > A. Krumbein Introduction Different approaches: RANS solver+ stability code + e N method RANS solver+ boundary layer code + stability code + e N method RANS solver+ boundary layer code + e N database method(s) RANS solver+ transition closure model or transition/turbulence model

Hyatt Regency, San Francisco, California > 06-June-06 Slide 6 > 24 th Applied Aerodynamics Conference > A. Krumbein Introduction Objectives of the talk: Documentation of the 1 st 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

Hyatt Regency, San Francisco, California > 06-June-06 Slide 7 > 24 th Applied Aerodynamics Conference > A. Krumbein Transition Prediction Coupling Structure Coupling Structure cycle = k cyc

Hyatt Regency, San Francisco, California > 06-June-06 Slide 8 > 24 th Applied Aerodynamics Conference > A. Krumbein Coupling Structure Transition Prediction Module: Laminar boundary-layer method for swept, tapered wings (conical flow) e N 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

Hyatt Regency, San Francisco, California > 06-June-06 Slide 9 > 24 th Applied Aerodynamics Conference > A. Krumbein 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, 2 nd & 4 th 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

Hyatt Regency, San Francisco, California > 06-June-06 Slide 10 > 24 th Applied Aerodynamics Conference > A. Krumbein P T upp (sec = 1) P T upp (sec = 2) P T upp (sec = 3) Coupling Structure Transition Prescription: Automatic partitioning into laminar and turbulent zones individually for each element Laminar points: S t,p  0 Independent of topology P T upp (sec = 4)

Hyatt Regency, San Francisco, California > 06-June-06 Slide 11 > 24 th Applied Aerodynamics Conference > A. Krumbein Test Cases KH3Y 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° Measurements European High Lift Programme (EUROLIFT), partly funded by EU Airbus LSWT (Bremen, Germany) Re  = 1.35 mio., M  = Transition band on fuselage, 30mm downstream of the nose

Hyatt Regency, San Francisco, California > 06-June-06 Slide 12 > 24 th Applied Aerodynamics Conference > A. Krumbein Test Cases Computations  = 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, 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  (x T /c) main = 0.08  N TS = 4.9 No indications for CF  N CF = N TS

Hyatt Regency, San Francisco, California > 06-June-06 Slide 13 > 24 th Applied Aerodynamics Conference > A. Krumbein 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° elemupper sidelower sideupper sidelower side slat(x T /c) slat = 0.21at TE(x T /c) slat = 0.11at TE main(x T /c) main = 0.08at TE(x T /c) main = 0.05(x T /c) main = 0.15 flapbeneath main TEat TEbeneath main TEat TE

Hyatt Regency, San Francisco, California > 06-June-06 Slide 14 > 24 th Applied Aerodynamics Conference > A. Krumbein Results  = 10°, upper side prescribed  = 10°, upper side predicted  = 10.0°, upper side: laminar surface regions Computational Results

Hyatt Regency, San Francisco, California > 06-June-06 Slide 15 > 24 th Applied Aerodynamics Conference > A. Krumbein Results  = 10°, lower side prescribed  = 10°, lower side predicted  = 10.0°, lower side: laminar surface regions

Hyatt Regency, San Francisco, California > 06-June-06 Slide 16 > 24 th Applied Aerodynamics Conference > A. Krumbein Results  = 14.0°, upper side: laminar surface regions  = 14°, upper side prescribed  = 14°, upper side predicted

Hyatt Regency, San Francisco, California > 06-June-06 Slide 17 > 24 th Applied Aerodynamics Conference > A. Krumbein Results  = 14.0°: laminar surface regions & transition labels TS  = 14°, upper side predicted CF  = 14°, lower side predicted

Hyatt Regency, San Francisco, California > 06-June-06 Slide 18 > 24 th Applied Aerodynamics Conference > A. Krumbein Results Comparison of  prescribed & predicted transition lines  = 10°, upper side predicted  = 14°, upper side predicted section of the hot films calibration point for N TS

Hyatt Regency, San Francisco, California > 06-June-06 Slide 19 > 24 th Applied Aerodynamics Conference > A. Krumbein Results Comparison of  c p -distributions:  = 0.20, 0.38, 0.66, 0.88  = 14.0°

Hyatt Regency, San Francisco, California > 06-June-06 Slide 20 > 24 th Applied Aerodynamics Conference > A. Krumbein 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

Hyatt Regency, San Francisco, California > 06-June-06 Slide 21 > 24 th Applied Aerodynamics Conference > A. Krumbein 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