Multiblock Grid Generation Results of the EC/BRITE EURAM Project EUROMESH, 1990-1992 Edited by Nigel P. Weatherill, Michael J. Marchant, and D. A. King Notes on Numerical Fluid Mechanics (NNFM) Volume 44 Series Editors: Ernst Heinrich Hirschel, Munchen Kozo Fujii, Tokyo Bram van Leer, Ann Arbor Keith William Morton, Oxford Maurizio Pandolfi, Torino Arthur Rizzi, Stockholm Bernard Roux, Marseille Volume 26 Numerical Solution of Compressible Euler Flows (A. Dervieux I B. van Leer I J. Periaux I A. Rizzi, Eds.) Volume 27 Numerical Simulation of Oscillatory Convection in Low-Pr Fluids (B. Roux, Ed.) Volume 28 Vortical Solution of the Conical Euler Equations (K. G. Powell) Volume 29 Proceedings of the Eighth GAMM-Conference on Numerical Methods in Fluid Mechanics (P. Wesseling, Ed.) Volume 30 Numerical Treatment of the Navier-Stokes Equations (w. Hackbusch I R. Rannacher, Eds.) Volume 31 Parallel Algorithms for Partial Differential Equations (w. Hackbusch, Ed.) Volume 32 Adaptive Finite Element Solution Algorithm for the Euler Equations (R. A. Shapiro) Volume 33 Numerical Techniques for Boundary Element Methods (w. Hackbusch. Ed.) Volume 34 Numerical Solutions of the Euler Equations for Steady Flow Problems (A. Eberle I A. Rizzi I H. E. Hirschel) Volume 35 Proceedings of the Ninth GAMM-Conference on Numerical Methods in Fluid Mechanics (J. B. Vos I A. Rizzi II. L. Ryhming, Eds.) Volume 36 Numerical Simulation of 3-D Incompressible Unsteady Viscous Laminar Flows (M. Deville I T.-H. La I Y. Morchoisne, Eds.) Volume 37 Supercomputers and Their Performance in Computational Fluid Mechanics (K. Fujii, Ed.) Volume 38 Flow Simulation on High-Performance Computers I (E. H. Hirschel, Ed.) Volume 39 3-D Computation of Incompressible Internal Flows (G. Sottas II. L. Ryhming. Eds.) Volume 40 Physics of Separated Flow - Numerical, Experimental, and Theoretical Aspects (K. Gersten, Ed.) Volume 41 Incomplete Decompositions (ILU) - Algorithms, Theory and Applications (W. Hackbusch I G. Wittum, Eds.) Volume 42 EUROVAL - An European Initiative on Validation of CFD Codes (w. Haase I F. Brandsma I E. Elsholz I M. Leschziner I D. Schwamborn, Eds.) Volume 43 Nonlinear Hyperbolic Problems: Theoretical, Applied, and Computational Aspects Proceedings of the Fourth International Conference on Hyperbolic Problems, Taormina, Italy, April 3 to 8,1992 (A. Donato I F. Oliveri, Eds.) Volume 44 Multiblock Grid Generation - Results of the ECIBRITE-EURAM Project EUROMESH, 1990-1992 (N. P. Weatherilll M. J. Marchant I D. A. King, Eds.) Volume 45 Numerical Methods for Advection - Diffusion Problems (c. B. Vreugdenhil I B. Koren, Eds.) Volumes 1 to 25 are out of print. The addresses of the Editors and further titles of the series are listed at the end of the book. Multiblock Grid Generation Results of the ECIBRlTE-EURAM Project EUROMESH, 1990-1992 Edited by Nigel P. Weatherill, Michael J. Marchant, and D. A. King Die Deutsche Bibliothek - CIP-Einheitsaufnahme Multiblock grid generation: results of the Ec/BRlTE-EURAM project EUROMESH, 1990-19921 ed. by Nigel P. Weatherill ... - Braunschweig; Wiesbaden: Vieweg, 1993 (Notes on numerical fluid mechanics; 44) ISBN-J3: 978-3-528-07644-3 e-ISBN-J3: 978-3-322-87881-6 DOl: 10.1007/978-3-322-87881-6 NE: Weatherill, Nigel P. [Hrsg.]; Europaische Gemeinschaften; GT All rights reserved © Friedr. Vieweg & Sohn Verlagsgesellschaft mbH, BraunschweiglWiesbaden, 1993 Softcover reprint of the hardcover 1st edition 1993 Vieweg ist a subsidiary company of the Bertelsmann Publishing Group International. No part of this publication may be reproduced, stored in a retrieval system or transmitted, mechanical, photocopying or otherwise, without prior permission of the copyright holder. Printed on acid-free paper ISSN 0179-9614 ISBN-J3: 978-3-528-07644-3 Foreword Computational Fluid Dynamics research, especially for aeronautics, continues to be a rewarding and industrially relevant field of applied science in which to work. An enthusiastic international community of expert CFD workers continue to push forward the frontiers of knowledge in increasing number. Applications of CFD technology in many other sectors of industry are being successfully tackled. The aerospace industry has made significant investments and enjoys considerable benefits from the application of CFD to its products for the last two decades. This era began with the pioneering work ofMurman and others that took us into the transonic (potential flow) regime for the first time in the early 1970's. We have also seen momentous developments of the digital computer in this period into vector and parallel supercomputing. Very significant advances in all aspects of the methodology have been made to the point where we are on the threshold of calculating solutions for the Reynolds-averaged Navier-Stokes equations for complete aircraft configurations. However, significant problems and challenges remain in the areas of physical modelling, numerics and computing technology. The long term industrial requirements are captured in the U. S. Governments 'Grand Challenge' for 'Aerospace Vehicle Design' for the 1990's: 'Massively parallel computing systems and advanced parallel software technology and algorithms will enable the development and validation of multidisciplinary, coupled methods. These methods will allow the numerical simulation and design optimisation of complete aerospace vehicle systems throughout the flight envelope'. This volume contains a set of papers describing work carried out during the EuroMesh project on 'Multi-Block Mesh Generation for Computational Fluid Dynamics'. The work was performed under a cost shared research contract (AERO 0018) within the programme BRITFJEURAM Area 5 Aeronautics of the Commission of the European Communities (CEC). EuroMesh was a pre-competitive research project lead by British Aerospace Regional Aircraft Ltd under the umbrella of the Aeronautics initiative managed and administered by the CEC DGXIIF. The project ran for two years with fourteen partners (6 from the aeronautics industry, 3 universities and 5 research institutes) from seven countries from the European Community and EFTA. I would like to thank all those involved with EuroMesh for their enthusiasm and cooperation. In particular I would like to thank the Task Managers and Working Group Coordinators for their efforts. I would also like to offer my gratitude to Nigel Weatherill and Michael Marchant (University College of Swansea) for their assistance in the preparation of this publication and to Drietrich Knoerzer (CEC-DGXIIh) for his guidance on the running of the project. D. A. King, BAe Woodford, February 1993. v Contents Page I. Introduction The EUROMESH Project 3 D. A. King An introduction to grid generation using the multiblock approach 6 N. P. Weatherill II. Topology Generation. 19 Topology generation within CAD systems 21 V. Treguer-Katossky, D. Bertin and E. Chaput A topological mOOeller 27 R. Scateni Advancing front technique used to generate block quadrilaterals 32 T. Schbhfeld III. Surface Grid Generation and Geometry Modelling 35 Surface mesh generation using projections 37 J. M. de la Viuda Generation of surface grids using elliptic PDEs 45 P. Weinerfelt Generation of structured meshes over complex surfaces 48 B. Morin and V. Treguer-Katossky Surface modelling using Coons multipatch and non-uniform rational surface 55 E. Chaput Reparametrization of block boundary surface grids 63 S. Farestam Ain:raft surface generation 71 H. Sobieczky VII Contents (continued) Page IV. Volume Grid Generation 17 Use ofONERA grid optimization method at CASA 79 J. M. de Ia Viuda, J. J. Guerra and A. Abbas Multi-block mesh generation for complete aircraft configurations 86 K. Becker and S. Rill Development of 3D multi-block mesh generation tools 117 J. Oppelstrup, o. Runborg, P. Mineau, P. Weinerfelt, R. Lehtimi'ki and B. Arlinger Multi-block mesh optimization 130 T. Fol and V. Treguer-Katossky Smoothing of grid discontinuities across block boundaries 139 P. Mineau V. Grid Optimization and Adaption Methods 149 Grid adaption in computational aerodynamics 151 R. Hagmeijer and K. M. J. de Cock Embedding within structured multi-block computational fluid dynamics simulation 169 S. N. Sheard and M. C. Fraisse Adaptive mesh generation within a 2D CFD environment using optimisation techniques 179 A.F.E.Home Two dimensional multi-block grid optimisation by variational techniques 189 M. R. Morris Local mesh enrichment for a block structured 3D Euler solver 199 T. Schomeld The adaptation of two-dimensional multiblock structured grids using a PDE-based method 207 D. Catherall Contribution to the development of a multiblock grid optimization and adaption code . 224 O-P. Jacquotte, G. Coussement, F. Desbois and C. Gaillet General grid adaptivity for flow simulation 263 M. J. Marchant, N. P. Weatherill and J. Szmelter Error estimates and mesh adaption for a cell vertex finite volume scheme 290 J. A. Mackenzie, D. F. Mayers and A. J. Mayfield Multigrid methods for the acceleration and the adaptation of the transonic flow problems 311 A. E. Kanarachos, N. G. Pantelelis and I. P. Voumas VIII I. INTRODUCTION 1 The EUROMESH Project D.A. King Research Department British Aerospace RAL Woodford Aerodrome,Woodford,Cheshire,SK7 lQR - UK Computational Fluid Dynamics (CFD) methods are now well established as an integral part of the aerodynamic design process throughout the civil aerospace industry. They have been successfully employed in the wing design for modern civil transport aircraft and executive jets over the last two decades. Some significant increments in wing per formance have been associated with the introduction of new CFD methods. The design of the Airbus A310 saw the introduction of double curvature wings into the Airbus fam ily in part through the introduction of transonic small perturbation (TSP) methods. The A330/340 wing was primarily designed with viscous-coupled full potential tech niques. The next generation civil transports will be designed using methods both well established and those capable of modelling full aircraft configurations with Euler and Navier-Stokes flow solvers. These new methods will enable adverse aerodynamic inter ference effects to be designed out from an early stage in the product development through an integrated total aircraft approach. CFD techniques continue to underpin our ability to design aircraft with ever decreasing drag, emitting less pollution and consuming less fuel. In addition, the introduction of various new aerodynamic technologies and design concepts (eg laminar flow for lower drag, low cost for manufacture etc) will rely heav ily on CFD to minimise high cost testing or prototyping. For high speed cruise design the traditional approach of designing in the wind tunnel has largely been replaced by design on the supercomputer with checking in the tunnel. This has yealded significant cost and performance benefits. However 3D CFD is not yet able to predict Clmax and so low speed design and optimisation is still carried out experimentaly. Advanced CFD methods have yet to make the same impact on dynamic design issues such as aeroelastic flutter and buffet. The major European airframe manufacturers have made substantial investment in the development and calibration of state-of-the-art computational aerodynamics codes. Most companies have specialised teams dedicated to the development, integration and appli cation of CFD to the design and analysis of their products. However, industry has traditionally relied on the support of universities and research establishments to carry out innovative basic research into new improved methods through both national gov ernmental and direct industrial support. The success of CFD in Europe is due in no 3 small part to the success of that partnership. The commercial sector has been slow to offer suitable proprietary CFD systems to the aerospace industry in part because of its unique transonic modelling requirements but also because of the relatively high accuracy and consistancy levels demanded for aircraft design. The development and marketing of commercial codes tends to have been concentrated on those industries whoose most basic requirement involves complex physical modelling (eg of combustion, radiation or two-phase flows). Alongside transition, turbulence modelling and high performance computing one of the key pacing items for industrial CFD is the development of fast user friendly techniques for the generation of a suitable computational mesh for aircraft components or entire configurations. Aerodynamic designers generally require very high standards of flow prediction from CFD to enable them to progress the evolution of a design without regular recourse to the wind tunnel. This means that meshes should be of a high quality to facilitate accurate modelling of the complex air flows accross a wide speed range around the various configurations of interest. In addition the grid generation systems should be very flexible and easy to use to enable key geometric features to be modelled within realistic design time-frames. Effective interfaces are required between company CFD and CAD systems to ensure accurate geometrical representation and rapid model set up times. Where geometric compromises are necessitated appropriate tools should be in place. A key design aim for a grid generation system should be to remove the need for the user to interact with the field (off surface) mesh. This has not generaly been a feature of current industrial (or any other) systems for modelling whole aircraft shapes. The need for use during an intensive design cycle rather than post design analysis yields distinct requirements for a system. Very rapid model set-up times for incremental adjustments to configurations are essential where daily or hourly turnaround is required. Over the last 15 years a number of grid generation approaches have been proposed to meet these requirements. The use of irregular (unstructured) grids of tetrahedra with finite element solvers or non-aligned meshes with finite volume or difference solvers have been popular with some groups. In addition over the last 7-8 years considerable interest has evolved in regular (structured) grid multi-block methods. Many different imple mentations of multi-block grid generation systems have been developed across Europe. Subtley different block topology concepts have been adopted with a wide variation to the degree of automation to the generation. A number of approaches for grid node specifica tion from simple algebraic teechniques to direct solution of partial differential equations or optimisation formulations have been implemented. Further work is required to bring these industrial systems up to a fully acceptable standard and there is considerable scope for benefits to be accrued from collaboration on development and assesment. With an increasing focus of the aerospace business towards European companies and con sortia competing with large North American companies and perhaps with the Japanese in the next century the time is right for coordinated European wide collaboration on CFD development. A framework for pre-competative industrial collaborative research 4