
9e1bb8bcc1f2a2f8abd0578d535394f3.ppt
- Количество слайдов: 21
Automatic Transition Prediction and Application to 3 D High-Lift Configurations Andreas Krumbein German Aerospace Center - DLR Institute of Aerodynamics and Flow Technology, Numerical Methods Slide 1 > 24 th Applied Aerodynamics Conference > A. Krumbein Hyatt Regency, San Francisco, California > 06 -June-06
Outline Introduction Transition Prediction Coupling Structure Test Cases Computational Results Conclusion Outlook 2 Hyatt Regency, San Francisco, California > 06 -June-06
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 3 Hyatt Regency, San Francisco, California > 06 -June-06
Introduction Different approaches: RANS solver + stability code + e. N method RANS solver + boundary layer code + e. N database method(s) RANS solver + transition closure model or transition/turbulence model 4 Hyatt Regency, San Francisco, California > 06 -June-06
Introduction Different approaches: RANS solver + stability code + e. N method RANS solver + boundary layer code + e. N database method(s) RANS solver + transition closure model or transition/turbulence model 5 Hyatt Regency, San Francisco, California > 06 -June-06
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 6 Hyatt Regency, San Francisco, California > 06 -June-06
Coupling Structure Transition Prediction Coupling Structure cycle = kcyc 7 Hyatt Regency, San Francisco, California > 06 -June-06
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 2 d, 2. 5 d (infinite swept) + 3 d 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 8 Hyatt Regency, San Francisco, California > 06 -June-06
Coupling Structured RANS solver FLOWer: 3 D 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 9 Hyatt Regency, San Francisco, California > 06 -June-06
Coupling Structure Transition Prescription: Automatic partitioning into and turbulent zones individually for each element PTupp(sec = 1) laminar PTupp(sec = 2) PTupp(sec = 3) PTupp(sec = 4) Laminar points: St, p 0 Independent of topology 10 Hyatt Regency, San Francisco, California > 06 -June-06
Test Cases KH 3 Y geometry (DLR F 11 model) Half-model with Airbus A 340 fuselage Wing-body with full span slat and flap high-lift system Landing configuration: d. S = 26. 5°, d. F = 32. 0° Measurements European High Lift Programme (EUROLIFT), partly funded by EU Airbus LSWT (Bremen, Germany) Re = 1. 35 mio. , M = 0. 174 Transition band on fuselage, 30 mm downstream of the nose 11 Hyatt Regency, San Francisco, California > 06 -June-06
Test Cases Computations a = 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: a = 10°, hot film on main wing upper side at 68% span (x. T/c)main = 0. 08 NTS = 4. 9 No indications for CF NCF = NTS 12 Hyatt Regency, San Francisco, California > 06 -June-06
Test Cases ‘Point transition‘ (no transitional flow model) Prescribed transition lines: a = 10. 0° a = 14. 0° elem upper side lower side slat (x. T/c)slat = 0. 21 at TE (x. T/c)slat = 0. 11 at TE main (x. T/c)main = 0. 08 at TE (x. T/c)main = 0. 05 (x. T/c)main = 0. 15 flap hot film data slat &main wing 68% span beneath main TE at TE a = 10°, upper side a = 10°, lower side 13 Hyatt Regency, San Francisco, California > 06 -June-06
Results Computational Results a = 10. 0°, upper side: laminar surface regions a = 10°, upper side prescribed a = 10°, upper side predicted 14 Hyatt Regency, San Francisco, California > 06 -June-06
Results a = 10. 0°, lower side: laminar surface regions a = 10°, lower side prescribed a = 10°, lower side predicted 15 Hyatt Regency, San Francisco, California > 06 -June-06
Results a = 14. 0°, upper side: laminar surface regions a = 14°, upper side prescribed a = 14°, upper side predicted 16 Hyatt Regency, San Francisco, California > 06 -June-06
Results a = 14. 0°: laminar surface regions & transition labels a = 14°, upper side predicted TS TS CF CF CF a = 14°, lower side predicted 17 Hyatt Regency, San Francisco, California > 06 -June-06
Results Comparison of prescribed & predicted transition lines a = 10°, upper side predicted a = 14°, upper side predicted calibration point for NTS section of the hot films 18 Hyatt Regency, San Francisco, California > 06 -June-06
Results Comparison of cp-distributions: h = 0. 20, 0. 38, 0. 66, 0. 88 a = 14. 0° 19 Hyatt Regency, San Francisco, California > 06 -June-06
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 3 d 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 20 Hyatt Regency, San Francisco, California > 06 -June-06
Outlook Further comparisons for the current tast cases: Skin friction lines vs. flow visualizations Global coeffcients: lift & drag More validation cases, e. g. DLR F 5 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 21 Hyatt Regency, San Francisco, California > 06 -June-06