MEGADESIGN and MegaOpt - German Initiatives for Aerodynamic Simulation and Optimization in Aircraft Design (eBook)

Preface 6
Contents 8
Part I Reduction of SimulationTime 11
Recent Developments of TAU Adaptation Capability 12
Introduction 12
TAU-Code Adaptation Overview 13
Grid Refinement Algorithm 14
Edge-Indicator Sensor Functions 14
Target Point Number Iteration 15
Recent Algorithmic Devolpments 16
Results 16
Target Functional-Based Mesh Adaption 18
Mathematical Background 18
Implementation in the DLR TAU Code 21
Results 23
Conclusion 26
References 27
Adaptive Wall Function for the Prediction of Turbulent Flows 29
Motivation 29
Formulation and Implementation 30
High-Reynolds Boundary Condition 31
Hybrid Adaptive Boundary Condition 32
Validation 33
Transonic Airfoil Flow: RAE 2822 Case 9 33
Transonic Wing Flow: ONERA M6 35
Industrial Conditions 36
Conclusion 40
References 41
Acceleration of CFD Processes for Transport Aircraft 42
Introduction 42
Overview 42
Utilization of Improved Code Features 43
Automatization of Numerical Process Chain 45
Simultaneous Approach 46
Summary/Conclusions 47
References 47
Efficient Combat Aircraft Simulations with the TAU RANS Code 48
Background 48
Objectives 50
TAU Code Efficiency Improvements 50
Polar Simulations for High Angle-of-Attack Cases 54
Conclusions 59
References 59
Part II Improvement of Simulation Quality 60
Universal Wall Functions for Aerodynamic Flows: Turbulence Model Consistent Design, Potential and Limitations 61
Introduction 61
Compressible RANS Equations 62
Turbulence Model Consistent Universal Wall Functions 63
Wall Function Formulation 64
Boundary-Layer Approximation for Universal Wall Functions 65
Model-Consistency of Universal Wall Functions and Grid-Independent Predictions 65
Flat Plate Turbulent Boundary Layer at Zero Pressure Gradient 67
Near-Wall Behaviour of RANS Models in Situations of Non-equilibrium Flow 68
NumericalMethod 69
Validation for Aerodynamic Flows 70
Transonic Airfoil Flows RAE-2822 Cases 9 and 10 70
Subsonic A-Airfoil in Highlift Configuration 72
Application to 3D Testcases 73
Combination of Wall-Functions and y+-Adaptation 74
Best Practice Guidelines 75
Conclusions 75
References 76
Computational Modelling of Transonic Aerodynamic Flows Using Near-Wall, Reynolds Stress Transport Models 78
Introduction 78
Computational Method 80
Turbulence Modelling 81
Numerical Method 86
Results and Discussion 87
RAE2822 88
ONERA M6 Wing 90
DLR-ALVAST 93
Numerical Issues 95
Results and Discussion 95
References 96
Transition Prediction for Three-Dimensional Configurations 98
Introduction 98
Description of Methods 99
Linear Stability Theory 99
Numerical Methods 99
Implementation and Parallelization Issues 103
Results 104
Parallelization Performance 104
Code Validation 105
Feasibility Study 107
Conclusions 109
References 110
Application of Transition Prediction 112
Introduction 112
Transition Prediction Coupling 114
Computational Results 116
Conclusion 124
References 125
Numerical Simulation Quality Assessment for Transport Aircraft 126
Introduction 126
Aspects of Accuracy 126
Status on Accuracy 127
Cruise Configuration Analysis 127
High Lift Configuration Analysis 130
Means to Improve Accuracy 133
Conclusions 136
References 136
Part III Fluid Structure Coupling 137
Computational Methods for Aero-Structural Analysis and Optimisation of Aircrafts Based on Reduced-Order Structural Models 138
Introduction 138
The {/it Aeroelastic Coupling Module} – Solver-Independent Coupling of Computational Fluidand Structural Dynamics Codes 140
Load/Deformation Projection for Single Beams 142
Extension of the Load/Deformation Projection to Frameworks of Beams 143
Validation against Aeroelastic Experiments 144
The Timoshenko-Beam Generator – Automatic Identification of Timoshenko-Beam Properties for Multi-Cellular Thin-Walled Wing Structures 146
Beam Identification Methodology 146
Preparation of Structural Optimisation Constraints 147
Quality of Beam Identifications 147
Evaluating the Structural Design Space in Consideration of Fluid-Structure Interaction 149
Summary 151
References 152
Development and Application of TAU-AN SYS Coupling Procedure 154
Introduction 154
The Process-Chain and Its Components 155
Aerodynamic Codes 156
Structure Code 157
Interpolation Module 157
Volume Mesh Deformation 161
Coupling Management 162
Validation 162
Study on Model Deformation under ETW Conditions 164
Structure Model 165
Results of Numerical Study 166
Summary and Conclusions 168
References 169
Fluid-Structure Coupling: Simplified Structural Model on Complex Configurations 171
Introduction 171
Short Description of WingDACC Method 171
Results on Cruise Configuration 174
Near Design Point 174
Off-Design 174
Results on High-Lift Configuration 175
Integrated Approach 176
Overlay Approach 177
Future Extensions 179
Summary/Conclusions 179
References 180
Part IV Improvement of Shape Optimization Strategies 181
Development of an Automated Artificial Neural Network for Numerical Optimization 182
Introduction 182
Assessing the Optimization Problem 183
Principles of Artifial Neural Networks 184
Application to Optimization 185
Investigation of Suitable Artificial Neural Network Topologies 186
Application to Real World Problems 189
Summary 191
References 191
modeFRONTIER c, a Framework for the Optimization of Military Aircraft Configurations 192
Description of modeFRONTIER Capabilities 192
Single and Multi-objective Strategies 195
Design of Experiments 195
Multi Objective Genetic Algorithm 196
Simplex 197
Gradient Based Algorithm, SQP 198
Multi Objective Game Theory 199
Example: modeFRONTIER Optimization with Genetic Algorithm 200
Example: modeFRONTIER Optimization through Adjoint RANS-Methodology 201
Conclusions 206
References 206
One-Shot Methods for Aerodynamic Shape Optimization 207
Introduction 207
One-Shot Method for Linear-Quadratic Problems 209
Approximate Reduced SQP Preconditioner for a Defect Correcting Iteration 209
Approximate prSQP Preconditioner for a Defect Correcting Iteration 211
Generalization to Non-linear Problems 213
Numerical Applications 215
RAE2822 Airfoil in Transonic Euler-Flow with FLOWer 215
High-Lift Configuration with TAU 216
References 219
Automatic Differentiation of FLOWer and MUGRIDO 221
Introduction 221
TAF 223
Automatic Differentiation of FLOWer 224
Automatic Differentiation of MUGRIDO 227
Conclusions 228
Appendix 228
References 231
Adjoint Methods for Coupled CFD-CSM Optimization 236
Introduction 236
Adjoint Formulation for Aero-Structure Coupling 237
Implementation 240
Validation and Application 241
Conclusion 244
References 244
Part V Aerodynamic and Multidisciplinary Optimization of 3D-Configurations 246
Aerodynamic Optimization for Cruise and High-Lift Configurations 247
Introduction 247
Gradients via Adjoint Approach 248
Primal Approach 248
Dual Approach 248
The Continuous Formulation 249
The Discrete Adjoint Approach 250
The Metric Terms 252
Planform Optimization of a Very Efficient Large Aircraft (VELA) 252
Wing Shape Optimization of the DLR-F6 Configuration 254
Flap and Slat Settings Optimization of the DLR-F11 Aircraft 256
Conclusion 258
References 258
Aerodynamic Optimization of an UCAV Configuration 261
Introduction 261
Design Optimization Process 263
Tools of the Optimization Environment 265
Aerodynamic Optimization of a Combat Aircraft by an Evolutionary Approach 269
Optimization of an Aircraft Wing by a SIMPLEX Approach 274
Optimization of a Combat Aircraft by a MOGA Genetic Approach 278
Summary 282
References 282
Flexible Wing Optimisation Based on Shapes and Structures 284
Introduction 284
MDO Process Chain 285
Optimisation Process Chain Tools 286
CAD Geometry Handling 286
Wing Structural Model 286
Flow Solver 286
CFD/CSM Static Coupling 287
CAD Shape to Mesh Deformation Connector 287
Wing Optimisation Problem 288
Forces at Stationary Horizontal Flight 288
Flow Conditions 289
Design Parameters for Aerodynamic Shape and Wing Box Structure 289
Optimisation Algorithm 289
Handling of Optimisation Constraints 290
Optimisation Results 292
Test Optimisation 292
Final Optimisation with 13 Design Variables 294
Conclusion 301
References 302
Multidisciplinary Optimization of an UAV Combining CFD and CSM 303
Optimization Process 303
Aerodynamic Analysis and Optimization 305
FEMIntegration 305
Results 307
Conclusions 308
References 308
Author Index 309