Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 1 Navier-Stokes High-Lift Airfoil Computations with Automatic Transition Prediction using the DLR TAU Code Andreas Krumbein German Aerospace Center Institute of Aerodynamics and Flow Technology, Numerical Methods

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 2 Outline Introduction Transition Prediction Coupling Structure Test Case: 2D A310 take-off configuration Computational Results Conclusion Outlook

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 3 Introduction Aircraft industry and research requirements: RANS based CFD tool with transition handling Better numerical simulation results Capturing of otherwise unconsidered physical phenomena At first: impact on lift and drag Characteristics Transition prescription Transition prediction Modelling of transitional flow areas Automatic:no intervention of the user Autonomous:necessary user information as little as possible

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 4 Introduction Reduction of modelling 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 At first in FLOWer code 3d multi-element wing configurations Later in TAU code 3d multi-element wing configurations Fuselages and nacelles TAU transition prediction module developed by Institute of Fluid Mechanics, Technical University of Braunschweig in German research initiative MEGADESIGN

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 5 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

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 6 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

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 7 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 + fully automated stability code + e N method RANS solver+ boundary layer code + e N database method(s) RANS solver+ transition closure model or transition/turbulence model

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 8 Transition Prediction Coupling Structure Coupling Structure cycle = k cyc FLOWer

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 9 Transition Prediction Coupling Structure Coupling Structure cycle = k cyc FLOWer & TAU

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 10 Transition Prediction Coupling Structure Coupling Structure cycle = k cyc FLOWer & TAU

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 11 Coupling Structure Transition Prediction Module of TAU: RANS infrastructure part: BL data from RANS grid (BL mode 2)  Transition inside separation bubble possible  High mesh density necessary External codes:  Laminar boundary-layer method COCO (G. Schrauf) for swept, tapered wings (BL mode 1)  Transition inside separation bubble NOT possible  Laminar separation approximates transition if transition downstream of laminar separation point  e N database-methods for TS and CF instabilities (PD mode 1)  Local, linear stability code LILO (G. Schrauf) (PD mode 2) 2d, 2.5d (infinite swept) + 3d wings + 3d fuselages/nacelles (only BL mode 2) Single + multi-element configurations N factor integration along:  Line-in-Flight cuts  Inviscid streamlines Attachment line transition & by-pass transition not yet covered

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 12  = 14°, upper side predicted  = 14°, lower side predicted TC 214 from EUROLIFT II Re  = 1.35 mio., M  = 0.174, SAE, e N database methods FLOWer results

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 13 TS  = 14°, upper side predicted CF  = 14°, lower side predicted FLOWer results TC 214 from EUROLIFT II Re  = 1.35 mio., M  = 0.174, SAE, e N database methods

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 14 FLOWer results Comparison of  c p -distributions:  = 0.20, 0.38, 0.66, 0.88  = 14.0°

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 15 2d A310 take-off configuration M = 0.221, Re = 6.11 x 10 6,  = 21.4° grid 1: 22,000 points grid 2: 122,000 points, noses refined SAE turbulence model prediction on upper sides, lower sides fully laminar, N TS  8.85 (F1) exp. Transition locations  slat: 15% & flap: 34.5% kink on main upper side  19% different mode combinations: a) BL mode 1 & PD mode 1  BL code & TS database method b) BL mode 1 & PD mode 2  BL code & stability code c) BL mode 2 & PD mode 2  BL in TAU & stability code Test Case

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 16 TAU results Surface pressure grid 1 grid 2 a.) & b.) results identical  all lam. seps. c.) no convergence  grid too coarse c.) all from stability code

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 17 TAU results Skin friction grid 1 grid 2 a.) & b.) no separation bubbles a.) & b.) very small sep. bubble on slat c.) no convergence c.) much larger slat bubble & flap improved

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 18 TAU results Skin friction very small bubble large bubble grid 2 slat flap transition locations: error reduced by 40%

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 19 TAU results Transition locations and separation grid 2

Andreas Krumbein > 30 January 2007 MIRACLE Final Meeting, ONERA Châtillon, Folie 20 TAU transition prediction module works fast and reliable for 2d multi-element configurations Transition inside laminar separation bubbles can be detected with high accuracy when appropriate prediction approach is used Therefor, high grid densities are required much more testing necessary: more test cases needed with TS transition (e.g. CAST 10, A310 landing) full aircraft WB+HTP+VTP (wing with full-span flap without slit) WB high-lift configuration with full-span slat and flap from EUROLIFT II transition criteria:- transition in lam. sep. bubbles - attachment line transition - by-pass transition development of a stream-line oriented bl code with transverse pressure gradient COCO-3d → replaces COCO in 2007 unsteady transition prediction method based on e N method alternative approaches based on transport equations in future DLR T&T-project RETTINA done by TU-BS Conclusion/Outlook