103 Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM)

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1 103 Notes on Numerical Fluid Mechanics and Multidisciplinary Design (NNFM) Editors W. Schröder/Aachen K. Fujii/Kanagawa W. Haase/München E.H. Hirschel/München B. van Leer/Ann Arbor M.A. Leschziner/London M. Pandolfi/Torino J. Periaux/Paris A. Rizzi/Stockholm B. Roux/Marseille Y. Shokin/Novosibirsk

2 DESider A European Effort on Hybrid RANS-LES Modelling Results of the European-Union Funded Project, Werner Haase Marianna Braza Alistair Revell (Editors) ABC

3 Dr. Werner Haase Höhenkirchener Str. 19D D Hohenbrunn Germany Dr. Marianna Braza Institut de Mécanique des Fluides de Toulouse UMR CNRS/INPT N 5502 Allée du prof. Camille Soula F Toulouse France Marianna.Braza@imft.fr Dr. Alistair Revell School of Mechanical Aerospace and Civil Engineering C40, George Begg Building The University of Manchester P.O. Box 88 Manchester M60 1QD UK alistair.revell@manchester.ac.uk ISBN e-isbn DOI / Notes on Numerical Fluid Mechanics and Multidisciplinary Design ISSN Library of Congress Control Number: applied for c 2009 Springer-Verlag Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable for prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typeset & Cover Design: Scientific Publishing Services Pvt. Ltd., Chennai, India. Printed in acid-free paper springer.com

4 NNFM Editor Addresses Prof. Dr. Wolfgang Schröder (General Editor) RWTH Aachen Lehrstuhl für Strömungslehre und Aerodynamisches Institut Wüllnerstr. zw. 5 u Aachen Germany office@aia.rwth-aachen.de Prof. Dr. Kozo Fujii Space Transportation Research Division The Institute of Space and Astronautical Science 3-1-1, Yoshinodai, Sagamihara Kanagawa, Japan fujii@flab.eng.isas.jaxa.jp Dr. Werner Haase Höhenkirchener Str. 19d D Hohenbrunn Germany office@haa.se Prof. Dr. Ernst Heinrich Hirschel (Former General Editor) Herzog-Heinrich-Weg 6 D Zorneding Germany e.h.hirschel@t-online.de Prof. Dr. Bram van Leer Department of Aerospace Engineering The University of Michigan Ann Arbor, MI USA bram@engin.umich.edu Prof. Dr. Michael A. Leschziner Imperial College of Science Technology and Medicine Aeronautics Department Prince Consort Road London SW7 2BY U.K. mike.leschziner@ic.ac.uk Prof. Dr. Maurizio Pandolfi Politecnico di Torino Dipartimento di Ingegneria Aeronautica e Spaziale Corso Duca degli Abruzzi, 24 I Torino Italy pandolfi@polito.it Prof. Dr. Jacques Periaux 38, Boulevard de Reuilly F Paris France jperiaux@free.fr Prof. Dr. Arthur Rizzi Department of Aeronautics KTH Royal Institute of Technology Teknikringen 8 S Stockholm Sweden rizzi@aero.kth.se Dr. Bernard Roux L3M IMT La Jetée Technopole de Chateau-Gombert F Marseille Cedex 20 France broux@l3m.univ-mrs.fr Prof. Dr. Yurii I. Shokin Siberian Branch of the Russian Academy of Sciences Institute of Computational Technologies Ac. Lavrentyeva Ave Novosibirsk Russia shokin@ict.nsc.ru

5 Preface Preface In aircraft design, efficiency is determined by the ability to accurately and reliably predict the occurrence of, and to model the development of, turbulent flows. Hence, the main objective in industrial computational fluid dynamics (CFD) is to increase the capabilities for an improved predictive accuracy for both complex flows and complex geometries. This text part taken from Haase et al (2006), describing the results of the DESider predecessor project FLOMANIA is still - and will be in future valid. With an ever-increasing demand for faster, more reliable and cleaner aircraft, flight envelopes are necessarily shifted into areas of the flow regimes exhibiting highly unsteady and, for military aircraft, unstable flow behaviour. This undoubtedly poses major new challenges in CFD; generally stated as an increased predictive accuracy whist retaining affordable computation times. Together with highly resolved meshes employing millions of nodes, numerical methods must have the inherent capability to predict unsteady flows. Although at present, (U)RANS methods are likely to remain as the workhorses in industry, the DESider project focussed on the development and combination of these approaches with LES methods in order to bridge the gap between the much more expensive (due to high Reynolds numbers in flight), but more accurate (full) LES. Therefore the primary objective of the DESider project, amongst several key goals, was to demonstrate the capabilities of these so-called hybrid RANS-LES approaches in the application to industrially relevant test cases with a focus on aerodynamic flows characterised by separation, wakes, vortex interaction and buffeting, i.e. flow features with the central common theme; inherent unsteadiness. An additional aspiration that has been met was to demonstrate the extent to which hybrid RANS-LES methods can be applied to multi-disciplinary topics such as aero-acoustics (noise reduction) and aero-elastics (reduced A/C weight, unsteady loads, fatigue issues, improved A/C safety), thus enabling further tools towards a cost-effective and more accurate design. All the goals achieved during the DESider project and described in this book have resulted from what has been a highly successful co-operation between European industries, research establishments and universities, leading to much improved knowledge dissemination and achieving cross-fertilisation between different the various represented engineering industries; airframe, helicopters, power generation, car and train industries. This close collaboration, stimulated by the financial support from the European Union, can quite genuinely claim to have promoted and accelerated the enhancement

6 VIII Preface of CFD approaches of each DESider partner to a far greater extent than would have otherwise been possible with the partners functioning individually in isolation. The present book undertakes to describe the outcomes of the DESider project in their entirety and the editors keenly hope that this book clearly and effectively contributes to the area of accurate flow prediction in the form of new and innovative results and methods. Moreover, we hope that the chapter on hybrid RANS-LES methods, the newly developed turbulence models and the assessment and validation of methods based on a variety of test cases will help seed and motivate further and extended future investigations and validation work. Acknowledgments are due to each and all DESider partners who have contributed in a remarkably open and collaborative manner to ensure success and in doing so, making it such a pleasure for the editors to summarize the programme s technical achievements in the present book. Thanks are also due to A. Podsadowski and D. Knörzer, the European Commission s Scientific Officers of the DESider project, who have provided every help at every corner along to route to making this programme a success. Moreover, the financial support received for this book from the European Union via the KATnet-II network is very much appreciated. Last but not least, the editors of this book would like to express their gratitude to W. Schröder, the General Editor of the Springer series Notes on Numerical Fluid Mechanics and Multidisciplinary Design, as well as to his colleague A. Hartmann for their help and editorial advice. January 2009 Werner Haase Marianna Braza Alistair Revell München Toulouse Manchester

7 Contents Contents I The DESider Project. 1 1 Summary Introduction The Aeronautics and Space Priorities as a Background for DESider State of the Art Technical Project Description Research Approach and Technical Achievements Dissemination and Exploitation General Plans According to the Technical Annex An Attempt to Structure Dissemination and Exploitation Work Publication of Results Description of Tasks List of Partners and Addresses Conclusion The DESider Web Site and How to Access It II Presentation of Modelling Approaches DES and Its Modifications and Enhancements Introduction DES97 Formulation and General Principles of Building DES Models Based on Different RANS Models DDES Motivation and Objective DDES Formulation IDDES Motivation and Objective IDDES Formulation The X-LES Method A Hybrid URANS-LES Strategy for Large Eddy Simulation at High Reynolds Numbers Introduction Model Formulation Illustrative Results University of Manchester Hybrid RANS LES Method. 38

8 X Contents 4.1 Introduction Hybrid RANS - LES Method Channel Flows Trailing Edge Computations Zonal Detached Eddy Simulation, ZDES, ONERA Motivations Formulation ZDES Length Scale Subgrid Length Scale Treatment of the Damping Functions University of Manchester Embedded LES Method Introduction Synthetic Eddy Method Motivations Description of the Method Isotropic Synthetic Fluctuations as Inlet Boundary Conditions Introduction Synthesized Turbulence Formulation of the Scale-Adaptive Simulation (SAS) Model during the DESIDER Project Introduction Rotta s kl Model The KSKL Model The SST-SAS Model Numerical Treatment Convective Terms High Wave Number Treatment Scale-Adaptive Simulation (SAS) Capability RANS/URANS Modelling The Stress-Strain Lag Model The SST-Cas Model URANS/OES Tensorial Eddy-Viscosity Modelling Tensorial Eddy-Viscosity Concept in the Turbulence Behaviour Law Summary of the OES Anisotropic First-Order Model 66 III DESider Measurements The DESider Bump Experiment Motivation Model Desin Wall Measurements LDV Measurements PIV Measurements Accuracy Estimation Main Statistics of the Flow.. 77

9 Contents XI 1.6 Coherent Structures Introduction Characteristics of the Extracted Vortices Unsteadiness Characterization Conclusion The IMFT Circular Cylinder Experiment Experimental Set-Up Configuration Measurements Reynolds Averaging Phase Averaging and Proper Orthogonal Decomposition Experimental Results Flow Regime Time Independent Reynolds Averaged Fields Instantaneous Motion Coherent Structure Identification by Means of the POD Conclusions. 103 IV Applications Test Cases Circular Cylinder Flow Turbulence Models Used by the Related Partners Numerical Parameters Results Comparison of Global Parameters Comparison of Statistically Averaged Fields Comparison of Unsteady Fields Coherent Structures Identification by Means of the POD Conclusions TU Munich Delta Wing Test Case Description Description of the Computations Grids Numerical Methods and Turbulence Models Results Conclusions NACA0021 at 60 o Incidence Introduction General Flow Description Participants and Some Details of Simulations DES Results and Discussion. 129

10 XII Contents Effect of Time Sample, Span Size of the Domain, and Wind-Tunnel Walls Effect of Background RANS Model for DES Effect of Grid-Refinement Cross-Plotting of Results SAS and TRRANS Results and Discussion Integral Forces Concluding Remarks Ahmed Car Body (25 o and 35 o Slant Angle) Introduction Geometry Description and Flow Conditions Participants Overview Results Ahmed Body with 25 o Slant Angle Ahmed Body with 35 o Slant Angle Concluding Remarks Decay of Isotropic Turbulence Background and Motivation Flow and Test Case Description Table of Participants and Methods Results and Discussion Conclusion Three-Element Airfoil Test Case Description Geometry and Conditions Grid Computations and Models Zonal-Detached Eddy Simulation (ZDES) Delayed-Detached Eddy Simulation (DDES) Results and Discussion ZDES DDES Conclusions Simpson s 3D Hill Test-Case Test-Case Description The Computations Chalmers University FOI Imperial College EDF Discussion Conclusions Fully Developed Channel Low Reynolds Number Models Wall Functions Technical Description

11 Contents XIII Mandatory Low-Re Grid, Re = Recommended Low-Re Grids, Re = 8000 and Recommended Wall-Model Grids, Re = 4000, 8000 and Participants and Methods Chalmers EDF FOI ICSTM NTS TUB UMIST Results Concluding Remarks Bump in Square Channel (ONERA Experiment) Introduction Physical Properties and Boundary Conditions Grid Information Participating Partners, Turbulence Models, and Simulation Details Results of Simulations Mean Pressure Distribution along the Bottom Wall Mean Velocity Profiles Profiles of the Reynolds Stresses Two- and Three-Dimensional Visualisation Discussion Conclusions Supersonic Base Flow Introduction Test Case Presentation Participants and Methods Used Results and Discussion RANS Solutions Turbulence-Resolving Simulations Conclusions Separated Flow behind an Aerofoil Trailing Edge without Camber Description of Test Case Partner-Specific Practices Imperial College London (ICL) New Technologies and Services (NTS) University of Manchester (UMan) Results and Discussion Conclusions FA-5 Configuration Introduction

12 XIV Contents 12.2 Experimental Setup and Data Structured Grid Unstructured Grid Computations Conclusion Circular Cylinder on a Ground Plate Overview Flow Geometry Participants Results Pressure Coefficient Velocity Profiles Turbulent Intensity Streamlines Conclusions Fuel Assembly Industrial Test-Case Introduction The Computational Domain Turbulence Modeling Grid Generation URANS and LES Computations High Performance Computation (HPC) Tests (100 MCells) Conclusions and Perspectives EC145 Helicopter Fuselage An Industrial Case Test Case Description Geometry Flight Conditions Computation Challenges Experiment Partners, Numerical Tools, Grids and Computations Partners and Numerical Tools Grids Computations Results Global Loads Cp-Distribution Oil Flow Conclusion Oscillating Airfoil NACA0012 at 15 o A Basic Case for Aero Elasticity Test Case Description Dynamic Stall Flow Conditions Experimental Data Computations , Computational Grids

13 Contents XV Computational Details Results for URANS Results for DES Conclusion M219 Cavity Flow Introduction Description of Test Case Information of Modelling Methods Results and Discussion Unsteady Flow Features Time-Averaged Mean Flow Features Acoustic Tonal Modes Due to Pressure Oscillations Concluding Remarks Appendix for M219 Cavity Flow: Computations with and without Bay Doors Introduction Results and Discussion Rossiter Mode Frequencies Sound Pressure Levels (SPL) Summary of Conclusions Car Side-Mirror An Aero-Acoustics Case Background and Motivation Flow and Test Case Description Summary of the FLOMANIA Study Partners Contributing, Numerical and Modelling Setup Results Processing of the SPL Spectra Comparison of LES, DES and SAS in the Wake Region Effect of Grid Resolution The Upstream Horseshoe Vortex Conclusions Simplified Landing Gear Test Case Introduction Computational Setup Results Conclusions V Technical, Partner-Related Reports Methods, Models and Applications Performed Contribution of Alenia Aeronautica: Main Results Obtained within the Project 309

14 XVI Contents 1.1 Description of Numerical Techniques and Turbulence Models Implemented in Code UNS3D The Code UNS3D URANS Turbulence Model DES Turbulence Model Decay of Isotropic, Homogeneous Turbulence TC 02, Delta Wing at High Incidence TC E2 Oscillating NACA0012 Airfoil TC A1, M219 Cavity Flow SAS Model Development and Validation Activity of the ANSYS Group in the DESider Project Model Development Model Validation Chalmers Contribution Inlet Boundary Conditions Channel Flow: Direct Numerical Simulations D Hill Flow Onera Bump The SAS Model The Turbulence Model Channel Flow LES of the Flow around a 3D Hill LES of the Flow over a Finite Cylinder Contribution of Dassault to DESider Introduction Presentation of Navier-Stokes Solver Validation of Numerics on DIHT Test-Case Implementation and Validation of DES Modelisation Spalart-Allmaras Based DES k-ε SST Based DES Calibration on DHIT Case Implementation and Validation of Wall Blending Function Spalart Based DES k-ε SST Based DES Validation on 3D Generic Flat Plate Validation on Generic S-Duct Application to Aero-Acoustics Conclusions Contributions of DLR in DESider Numerical Method - The DLR TAU Code Work Undertaken during the DESider Project DIT NACA NACA 0012 (Oscillating at 15 AoA) Basic Aero-Elasticity Case. 342

15 Contents XVII Supersonic Base Flow at M= Ahmed Body FA5 Aircraft Additional Work Performed by DLR Grid Convergence Study for NACA0021 at 60 AoA High Wave Number Dissipation Reduction in the 343 TAU Code... 6 EADS-MAS Methods and Applications Methods and Turbulence Models NACA Delta Wing FA5 Generic Airplane M219 Cavity A Look Back on DESider at Eurocopter Germany Numerical Aerodynamics at ECD Potential Applications Methods Models Facts and Lessons Learnt Notes Test-Cases Models Conclusion EDF Achievements in Desider Introduction General Overview of the Overset Grid Technique Coupling Boundary Faces Coupling with a Body Force in the Overlapping Region RANS/LES Coupling Examples The Back-Step Facing Step Test-Case Normal RANS/LES Coupling Tangential Coupling Channel Flow Use of Code/Code Coupling for Wall Treatment 364 (RALEWA Method). 8.4 Conclusions Towards Efficient and Accurate Hybrid RANS-LES Modeling for Aerodynamic Applications Introduction DES and Hybrid RANS-LES Modelling DES Based on the k-equation Model (k-des Model) Hybrid RANS-LES Modelling Examples of Application Using the HYB0 Model Flow over a Three-Dimensional Hill 372

16 XVIII Contents Supersonic Base Flow M219 Cavity Flow Summary and Outlook Approximate Near-Wall Treatments Based on Hybrid RANS-LES and Zonal Methods for LES at High Reynolds Numbers Description of Schemes Hybrid RANS-LES Scheme Zonal Scheme Performance in Channel Flow Separated Flow from a Hydrofoil Separated Flow over a Three-Dimensional Hill Conclusions Statistical and Hybrid Turbulence Modelling for Strongly Detached Flows Around Fixed/Oscillating Bodies Anisotropic OES Modelling Tensorial Eddy-Viscosity Concept DES Associated with OES Results NACA0012 at Re=10 5, a=20 - in House Test Case NACA021 beyond Stall Test Case Pitching NACA0012 Airfoil The Ahmed Car Body Conclusions Hybrid RANS LES Simulations at NLR Using X-LES and a High-Order Finite-Volume Method X-LES Method High-Order Finite-Volume Method Grid Convergence Shear Layer Instability Application Conclusion Contribution of NTS General Overview DES Enhancements Delayed DES (DDES) DDES with Improved Wall-Modelling Capability (IDDES) Digest of the Validation Activity Contribution by NUMECA Introduction Code Description Turbulence Modelling Selected Results Calibration and Validation

17 Contents XIX Aerofoil at a High Angle of Attack The DESider Bump The Ahmed Body Concluding Remarks, Observations and Recommendations Contribution by ONERA Task 2.2: Measurements of Separating/Re-attaching Flows Task 3.2: DES with Improved Modelling Task 3.3: Embedded LES The Near-Future Approach Task 3.4: Hybrid LES A Step Forward Task 4.1.2: Application Challenges DES Implementation, Validation and Application at TU-Berlin Modelling Developments Test Cases DES Investigations DES Validation for Massively-Separated Flows Time Step Sensitivity of DES Dependency of DES on the Underlying RANS Model Assessment of the Numerical Scheme Additional Length Scale Substitutions and the Grey Area Problem Correction of RANS Model Damping Term Behaviour in LES Mode The IDDES Method for Wall-Modelled LES and Combination with Adaptive Wall Functions Conclusions and Outlook University of Manchester Contribution Introduction The Stress-Strain Lag Model Synthetic Eddy Method Hybrid RANS - LES Method Conclusions VI Summary of Experience with Hybrid RANS-LES Methods and a Look Ahead References.. 437