IUTAM Laminar-Turbulent Transition: 9th IUTAM Symposium, London, UK, September 2–6, 2019 (IUTAM Bookseries, 38)

This volume comprises the carefully revised papers of the 9th IUTAM Symposium on Laminar-Turbulent Transition, held at the Imperial College, London, UK, in September 2019. The papers focus on the leading research in understanding transition to turbulence, which is a challenging topic of fluid mechanics and arises in many modern technologies as well as in nature. The proceedings are of interest for researchers in fluid mechanics and industry who have to handle these types of problems, such as in the aeronautical sector. Preface Contents Invited Papers Unraveling Transition and Turbulence Using Nonlinear Optimization 1 Introduction 2 Mathematical Framework 2.1 Computation of the Minimal Seed 2.2 Applications to Flow Control 2.3 Computation of Heteroclinic Orbits 2.4 Extention to Turbulent Conditions 3 Results 3.1 Optimal Perturbations in Transitional Flow 3.2 Optimal Perturbations in Turbulent Flow 4 Conclusions References Predicting Laminar-Turbulent Transition Influenced by Surface-Induced Flow Distortions 1 Introduction 2 Paths to Transition 3 Approaches to Predicting Transition 3.1 Nonlinear Amplitude Methods 3.2 Linear Amplitude Methods 4 Model Prediction as a Tool for Understanding 4.1 Revisiting Step Effects on TS-Dominated Transition 4.2 Gap Effects on TS-Dominated Transition 5 Conclusions References 40 Years of Transition Research at NASA: A Personal Perspective 1 Introduction 2 Computational Methods for Compressible Stability Analysis 3 2D Partial-Differential Eigenvalue Problem 4 Linearized Navier–Stokes 5 Parabolized Stability Equations 6 Development of Quiet Tunnels 7 Supersonic and Hypersonic Boundary Layer Transition 8 Cone/Flat-Plate Transition Reynolds Number Controversy 9 Effect of Bluntness and Real Gas on Hypersonic Boundary Layer Transition 10 Instability of Rotating Disk Flow 11 Nonlinear Development of Görtler and Crossflow Vortices 12 The Attachment-Line Boundary Layer 13 Epilogue References Progress in Stability and Transition Research 1 Introduction 2 Personal Areas of Research 3 Verification and Validation 3.1 Verification 3.2 Validation 4 Summary References Progress in Development of Amplitude Method of Transition Prediction on Swept Wing 1 Introduction 2 Non-Linear PSE-Method for Random Perturbations 3 Receptivity of Boundary Layer to Surface Roughness and FST 4 Statistical Description of Intermittency in Transition Zone 5 Comparison of Amplitude Method with Experiment 6 Conclusions References Coherent Structures, Dynamical Systems, Edge States Nonlinear Optimal Disturbances in Compressible Shear Flows 1 Introduction 2 Methodology 3 Results and Discussions 4 Conclusions References On Subharmonic Resonance and Other Nonlinear Mechanisms in Wavepackets in Boundary Layers 1 Introduction 2 DNS Code 3 Code Validation 4 Nonlinear Stages of a Wavepacket 5 Conclusions References Numerical Simulation of Gas Injection Effect on Boundary Layer Instability for Space Vehicles 1 Introduction 2 Numerical Simulation 2.1 Laminar Flow Over Hemispherical Model 2.2 Laminar Flow Over ExoMars Vehicle Model 3 Stability Computations 4 Conclusion References Two-Dimensional Self-Sustaining Processes Involving Critical Layer/Wall Layer Interaction 1 Introduction 2 Interaction Properties 3 A 2D SSP at Large R with Two Critical Layers 4 A 2D SSP at Large R with a Single Critical Layer 5 Navier-Stokes Comparison 6 Conclusion References Study of Transition to Turbulence Using Discrete Directed Percolation Model 1 Introduction 2 Navier-Stokes Equations and Burgers Equation 2.1 Navier-Stokes Equations 2.2 Burgers Equation 3 Ultradiscretization 4 Discrete and Ultradiscrete Burgers Equation 4.1 Discrete Burgers Equation 4.2 Cellular Automaton 5 Results and Discussions 5.1 Burgers Cellular Automaton 5.2 Effect of Reynolds Number 6 Conclusions References Nonlinear Evolution of Multiple Helical Modes in the Near-Nozzle Region of Subsonic Circular Jets: A Weakly Nonlinear Critical-Layer Theory 1 Introduction 2 Asymptotic Theory: Weakly Nonlinear Critical Layer 2.1 Asymptotic Scaling and The Amplitude Equation 2.2 Fourier Decomposition and Upstream Condition 3 Numerical Solutions 4 Conclusion References Experiments Investigation of Distributed Roughness Element System Based on Dielectric Barrier Discharge for the Suppression of Stationary Cross-Flow Vortices on the Swept Wing 1 Introduction 2 Experimental Setup 3 Results 4 Conclusion References Bump-Induced Transition in Compressible High Reynolds Number Flow: Experimental Results and Correlation with Linear Stability Analysis 1 Introduction 2 Experimental and Numerical Setup 2.1 Experimental Setup 2.2 Numerical Setup 3 Results 4 Conclusions References Experimental Analysis of the Effect of Suction and Step Height on Boundary-Layer Transition 1 Introduction 2 Experimental Setup 3 Results and Discussion 4 Conclusions References On the Interaction of Freestream Turbulence and Attachment-Line Boundary Layer 1 Introduction 2 Freestream Turbulence Approaching a Stagnation Point 3 Attachment-Line 4 Experimental Setup 5 Results 6 Conclusions References Isolated Roughness and Tollmien-Schlichting Waves in Boundary-Layer Transition 1 Introduction 2 Experimental Setup 3 Roughness-Induced Transition With and Without T-S Waves 4 Conclusions References Instabilities and Transition on a Rotating Cone–Old Problems and New Challenges 1 Introduction 2 Local Linear Stability Analysis 3 Experimental Set-Up 4 Results and Discussions 4.1 Old Problems: Stationary Modes 4.2 New Challenges: Nonstationary Modes 5 Summary and Discussion References An Experimental Investigation of the Effects of Wires and Forward-Facing Steps on the Laminar-Turbulent Transition of a Sucked Boundary Layer 1 Introduction 2 Experimental Facility 3 Suction Parameters and Reference Smooth Configurations 4 Combined Effect of Surface Defects and Suction on Transition 4.1 Experimental Characterization 4.2 Numerical Analysis 5 Conclusion References Control of Unsteady Görtler Instability Modes by Steady Görtler Vortices 1 Introduction 2 Experimental Setup 3 Disturbance Source 4 Main Results References Transitional Intermittency in a Flat Plate Boundary Layer Subjected to Elevated Free-Stream Turbulence 1 Introduction 2 Experimental Setup 3 Results 4 Conclusions References Response of NLF Airfoils to Small Scale Turbulence 1 Introduction 1.1 Atmospheric Turbulence 1.2 Small Scale Turbulence and Its Effect on Transition 2 Experimental Setup 3 Results, Baseflow Conditions 4 Results, Increased Turbulence Level 4.1 Spectral Development 4.2 Spanwise Wavenumber Spectrum 4.3 Temporal Development 4.4 Transition Prediction at Increased Turbulence Level 5 Conclusions References Disturbances in a Three Dimensional Boundary Layer at Elevated Free Stream Turbulence 1 Introduction 2 Experimental Setup 3 Results 4 Summary References Flow Control Experimental Investigation of Spanwise-Periodic Surface Heating for Control of Crossflow-Dominated Laminar-Turbulent Transition 1 Introduction 2 Experimental Setup 2.1 DLR-SPECTRA Configuration 2.2 Actuator: Spanwise Periodic Heating 2.3 Wind Tunnel Facility 2.4 Measurement Techniques 3 Results 3.1 Characterization of the Surface-Temperature Distribution 3.2 Impact of Surface Heating on Boundary-Layer Stability 3.3 Systematic Variation of Heating Power 3.4 Effect on the Scenario of Laminar-Turbulent Transition 4 Conclusion References Nonlinear Optimal Control Using Deep Reinforcement Learning 1 Introduction 2 Reinforcement Learning: Introductory Elements 2.1 Bellman's Optimality Condition 2.2 Reinforcement Learning 2.3 General Classification for RL Algorithms 2.4 Deep Deterministic Policy Gradient as an Actor-Critic Algorithm for DRL 3 Control of Chaotic Regimes: The Kuramoto-Sivashinsky System 3.1 Implementation of DDPG 3.2 Results 4 Conclusions and Perspectives References Linear Impulse Response of a Plasma Jet 1 Introduction 2 Problem Formulation 2.1 Jet Simulations 2.2 Linear Stability Theory 3 Results 3.1 Comparison of Base States 3.2 Absolute Instabilities 3.3 Full Impulse Response 3.4 Conclusions References Control of Travelling Crossflow Vortices Using Volume Forcing 1 Introduction 2 Numerical Method 2.1 Basic Setup 2.2 Localized Volume Forcing 3 Base-Flow Characteristics and Reference Case 4 Investigations of Control 4.1 Single Row of Actuators 4.2 Multiple Rows of Actuators 5 Conclusions References Experimental Attenuation of a Trailing Vortex Inspired by Stability Analysis 1 Introduction 2 Methodology 2.1 Experimental Setup 2.2 Actuation Modes 2.3 Lift and Drag Measurements 3 Results 3.1 Near Field: Disturbance Characterization 3.2 Intermediate Field: Time-Averaged Quantities 4 Conclusions and Future Work References General Stability Analysis Distributed Excitation of Crossflow Waves Due to Scattering of Freestream Vortices by Surface Waviness 1 Introduction 2 Theoretical Analysis 3 Experimental Setup and Base Flow 4 Most Important Results References Overview of the AFT Model for Transition Prediction in Complex Aerodynamic Flows 1 Introduction 2 Transition Prediction in General CFD Applications 3 Amplification Factor Transport Transition Model 4 Conclusion and Outlook References BiGlobal Stability Analysis of Swept-Wing Boundary Layers with Forward and Backward Facing Steps 1 Introduction 2 Mathematical Approach 3 Base Flow Computations 4 Numerical Strategy 5 Results and Discussion 6 Conclusions References Effect of Discrete Widely Spaced Suction on a Transitioning Flow at High Suction Rates 1 Introduction 2 Experimental Setup 3 Results References Global Stability Analysis and DNS of a Swept Airfoil Section in Subsonic Flow 1 Introduction and Methodology 1.1 DNS and Global Stability Methods 2 Results 3 Conclusion References Instability of Tilted Shear Flow in a Strongly Stratified and Viscous Medium 1 Introduction 2 Equations of Motion 3 The Origin of the Instabilities in Strong Stratification 3.1 Squire's Theorem for Weakly Tilted Shear Flows 4 Stabilisation of the Low Fr Instability Frrightarrowinfty 5 Numerical Results 5.1 Numerical Analysis for Highly Tilted Shear Flows 5.2 Absolute Instability 6 Conclusion References Towards Understanding of Natural Boundary-Layer Transition for Low-Speed Flows via Random Excitation 1 Introuduction 2 Approach 2.1 Computational Framework 2.2 Vortical Free-Stream Turbulence Generation 2.3 Random Excitation Using a 2-D Blowing and Suction Slot 3 Secondary Instability Investigation 4 Direct Numerical Simulations 5 Conclusion References On the Propagation of Two Types of Disturbances Through a Laminar Boundary Layer Subjected to Separation and Transition 1 Introduction 2 Experimental Setup 3 Flow Development Under Steady Conditions 4 Flow Development Under the Effect of Disturbances 5 Conclusions References Stability and Control of the Flow in a Porous Channel 1 Introduction 1.1 Motivation and Our Contribution 1.2 Related Work 2 Flow Setup and System Formulation 2.1 Base Flow Solution 2.2 Linear Stability 3 Control Framework 4 Control Synthesis—Linear Quadratic Regulator (LQR) 4.1 Non-modal Stability 5 Results and Discussions 6 Conclusion References Use of Instabilities for Optimal Laminar Separation Delay 1 Introduction 2 Methodology 2.1 Computational Setup 2.2 Direct Numerical Simulations 3 Steady Separation Delay 3.1 Maximal Transient Perturbation Growth 3.2 Nonlinear Optimization 3.3 Effect of Spanwise Wavenumber 4 Unsteady Separation Delay 5 Conclusions References Wave Packet Dispersion in Inflectional and Non-inflectional Flows 1 Introduction 2 Problem Formulation 2.1 Base Flows 2.2 Numerical Solution of the Orr-Sommerfeld Equation 3 Results 4 Conclusions References Linearized Formulation for Fluid-Structure-Interaction for Rigid-Body Motion 1 Introduction 2 Linearization of FSI 3 Linear Results 3.1 Oscillating Cylinder 3.2 Rotating Cylinder with Splitter-Plate 3.3 Aeroelastic Instability of NACA0012 3.4 Structural Sensitivity of the Eigenvalue 4 Conclusions References Investigations of Laminar to Turbulent Transition in an Oscillating Airfoil Boundary Layer 1 Introduction 2 Investigated Case 3 Experimental Results 4 Linear Stability Analysis 5 Analysis and Discussion 6 Conclusions References Global Stability Analysis of JAXA H-II Transfer Vehicle Re-entry Capsule 1 Introduction 2 Numerical Method 2.1 Stability Problem 2.2 Code Features 3 Global Stability Analysis of JAXA's HTV-R Capsule 3.1 RANS Baseflow Solution 3.2 Global Stability Results 4 Conclusions References Global Linear Stability and Sensitivity of Hypersonic Shock-Boundary Layer Interactions 1 Introduction 2 Physical Problem Setup 3 Linear System Formulation 4 Global Linear Stability 4.1 The Onset of Linear Instability 4.2 Beyond the Critical Parameters: A Small λz Instability 5 Sensitivity to External Perturbations : Input-Output Analysis 6 Conclusions and Future Work References On the Influence of Frequency and Spanwise Wavelength on the Formation of Görtler Vortices 1 Introduction 2 Results 3 Conclusions References Non-modal Linear Stability Analysis of Ablation Flows Relative to Inertial Confinement Fusion 1 Introduction 2 Model 2.1 Base Flow 2.2 Linear Perturbations 3 Optimal Perturbation 3.1 Direct-Adjoint Method 3.2 Optimal Initial Perturbations 4 Discussion and Conclusion References Transition Due to Aerofoil-Wake Boundary Layer Interaction 1 Introduction 2 Experimental Setup 3 Disturbance Profile 4 Streaky Structure 5 Conclusion References High Speed and Hypersonics Roughness-Induced Laminar-Turbulent Transition in the Boundary Layer of a Capsule-Like Geometry at Mach 20 Including Non-equilibrium 1 Introduction 2 Numerical Setup 3 Results 4 Conclusions References The Role of Receptivity in Prediction of High-Speed Laminar-Turbulent Transition 1 Introduction 2 Wave Packets Excited by Coherent and Incoherent Disturbances 3 Effect of the External Forcing Coherence 4 Uncertainty in the External Disturbance Environment 5 Conclusions References Numerical Investigation of the Nonlinear Transition Stages in a High-Enthalpy Hypersonic Boundary Layer on a Right Cone 1 Introduction 2 Numerical Approach 3 Three-Dimensional Wave Packet 4 Controlled Fundamental Breakdown 4.1 Primary and Secondary Instability Regime 4.2 Controlled Fundamental Breakdown 5 Conclusions References Direct Numerical Simulations (DNS) of Natural Transition in High-Speed Boundary Layers Using a Broadband Random Forcing Approach 1 Introduction 2 Geometry and Flow Conditions 3 Random Forcing Approach 4 Results 5 Conclusions References Sensitivity of Boundary-Layer Stability and Transition to Thermochemical Modeling 1 Introduction 2 Methodology 2.1 Chemical Rates and Thermodynamic Properties 2.2 Mean Flow Conditions 2.3 Design of Experiments 3 Results 3.1 Analysis of Variation 4 Conclusions References Effects of Streaky Structures on the Instability of Supersonic Boundary Layers 1 Introduction 2 Effect of Roughness-Induced Streaks on Viscous First-Mode Instability 3 Secondary Instability of Streaks Induced by Free-Stream Turbulence 4 Summary and Conclusions References Sensitivity of Reacting Hypersonic Boundary Layers to n-periodic Surface Roughness 1 Introduction 2 Theoretical Background 2.1 Governing Equations and Modelling Approaches 2.2 Linearised Analysis 3 Methods 3.1 Computational Setup and Tools 3.2 Automatic Linearised Stability Analysis of Large Nonlinear Systems 3.3 Extension to N-Periodic Systems of Roughness Units 4 Preliminary Results and Discussion 5 Conclusions and Future Work References Hypersonic Boundary Layer Instability and Control by Passive Porous Coatings 1 Introduction 2 Experimental Setup 3 Results 4 Conclusions References Numerical Study of Crossflow Jet Generated Instabilities in a High-Speed Boundary Layer 1 Introduction 2 Problem Formulation and Numerical Method 3 Results 4 Conclusions References Influence of High-Temperature Effects on the Stability of the Wake Behind an Isolated Roughness Element in Hypersonic Flow 1 Introduction 2 Theoretical Framework 3 Numerical Methodology 4 Stability Analysis of the Smooth Wedge Configuration 5 Stability Analysis in the Roughness Wake 6 Conclusions References Effect of the Single Roughness on Shock Wave/Laminar Boundary Layer Interaction 1 Introduction 2 Experimental Setup 3 Results 4 Conclusions References Linear Instability of Shock-Dominated Laminar Hypersonic Separated Flows 1 Introduction 2 Small-Amplitude Disturbances 3 Frequency Analysis 4 Conclusion References Controlled Cross-Flow Mode Interaction in Mach 6 Boundary Layer 1 Introduction 2 Experimental Setup 3 Results 4 Summary References Stability Analyses of Hypersonic, Conical Flows with Transpiration Cooling 1 Introduction 2 Numeric Methods 2.1 Mean Flow Solver 2.2 Stability Code 3 Geometry and Test Matrix 4 Results 4.1 Reference Test Cases Without Effusion 4.2 Effusion Test Cases 5 Conclusion References Nonlinear PSE Transition Predictions in Hypersonic Boundary Layers with Finite-Rate Chemical Reactions 1 Introduction 2 Problem Formulation 3 Numerical Tools 4 Results 5 Conclusions References Roughness and Receptivity Investigation of a Sectioned Boundary Layer Suction System in Case of Failure of One of Its Sections in Application to the Three-Dimensional Boundary Layer Laminarization on the Swept Wing 1 Introduction 2 Experimental Setup 3 Results 3.1 Low Freestream Turbulence Regime 3.2 Elevated Freestream Turbulence Regime 4 Conclusion References Destabilisation of Stationary and Travelling Crossflow Disturbances Due to Forward and Backward Facing Steps over a Swept Wing 1 Introduction 2 Methods 2.1 Base Flow Generation 2.2 Boundary Layer Extraction 2.3 Stability Tools 3 Results 4 Conclusions References Deep Learning Based Transition Prediction for Aeronautical Applications 1 Introduction 2 Methodology 2.1 Database Generation, Problem Statement and Input Definition 2.2 Code Implementation and Set-Based MLP Structure Definition 2.3 Final Neural Network Setup and Training 3 Validation and Testing 4 Conclusions References Numerical Studies on the Influence of Step-Like Surface Irregularities on the Development of Tollmien-Schlichting Waves 1 Introduction 2 Problem Description 2.1 Setup 2.2 AHLNS Equations 2.3 N-factor envelope 3 Numerical Results 3.1 Base Flow Computations 3.2 Base Flow Results 3.3 Instability Analysis 3.4 Effect of Step Height and Shape 3.5 Prediction of Transition Location 4 Summary and Conclusions References Receptivity to Surface Imperfections 1 Introduction 2 Analysis 3 Results 4 Discussion and Conclusions References Influence of Cylindrical and Two-Dimensional Roughness Elements on the Laminar-Turbulent Transition on Flying Wing Model 1 Introduction 2 Experimental Setup and Investigation Methods 3 Results 3.1 Flow Structure Near the Wing Surface 3.2 Boundary Layer Structure Depending on the Height of the Three-Dimensional Roughness Element 3.3 Determining the Area of the Boundary Layer Maximum Receptivity 3.4 Influence of 2d-Roughness Element 4 Conclusions References On the Effects of Sound in Subsonic Boundary Layer Flows 1 Introduction 2 Acoustic Boundary Layer Modelling 2.1 Inviscid Reflection 2.2 Viscous Reflection 3 Acoustic Boundary Layer Profiles 4 Conclusions References Receptivity of Unsteady Compressible Görtler Flows to Free-Stream Vortical Disturbances 1 Introduction 2 Mathematical and Numerical Procedures 2.1 Flow Definition, Scaling, and Equations of Motion 3 Results 3.1 Growth Rates 3.2 Energy Growth 3.3 Neutral Map 3.4 Asymptotic Analysis at Relatively High Frequency 3.5 Comparison with Experimental and Theoretical Results 4 Conclusions References Leading-Edge Receptivity of Moderately Supersonic Boundary Layers to Free-Stream Disturbances 1 Introduction 2 Free-Stream Disturbances 3 Boundary Layer Disturbances Generated by Free-Stream Vorticity 4 Boundary Layer Disturbances Generated by the Fedorov/Khokhlov Mechanism at Near Critical Obliqueness Angles 5 The Viscous Triple-Deck Region 5.1 Numerical Results 6 The Inviscid Triple-Deck Region 7 Next Stage of Evolution 8 Conclusions References Direct Numerical Simulations of Tollmien-Schlichting Disturbances in the Presence of Surface Irregularities 1 Introduction 2 Numerical Setup 3 Results and Discussion 3.1 Base Flow Calculations 3.2 Evolution of Tollmien-Schlichting Disturbances 4 Conclusions References Stability Analysis of Boundary Layer Flow with Rotating Cylindrical Surface Roughness Elements 1 Introduction 2 Numerical Methods 2.1 Baseflow Computation 2.2 Bi-Global Linear Stability Analysis 2.3 Linear Stability Mechanisms 3 Results 3.1 Base Flow 3.2 Linear Stability 3.3 Instability Mechanisms 4 Conclusions References Triadic Resonance Analysis of Distributed Roughness Effects on Crossflow Instability in Swept-Wing Boundary Layers 1 Introduction 2 Mathematical Description 2.1 Perturbation Equations 2.2 Crossflow Eigenmodes and Roughness Modes 2.3 Generalized Resonance Mechanisms 3 Numerical Results on Effects of Roughness Through Resonant Interactions 3.1 Stationary Vortices 3.2 Travelling Vortices 4 Conclusions References Intro -- Preface -- Contents -- Invited Papers -- Unraveling Transition and Turbulence Using Nonlinear Optimization -- 1 Introduction -- 2 Mathematical Framework -- 2.1 Computation of the Minimal Seed -- 2.2 Applications to Flow Control -- 2.3 Computation of Heteroclinic Orbits -- 2.4 Extention to Turbulent Conditions -- 3 Results -- 3.1 Optimal Perturbations in Transitional Flow -- 3.2 Optimal Perturbations in Turbulent Flow -- 4 Conclusions -- References -- Predicting Laminar-Turbulent Transition Influenced by Surface-Induced Flow Distortions -- 1 Introduction -- 2 Paths to Transition -- 3 Approaches to Predicting Transition -- 3.1 Nonlinear Amplitude Methods -- 3.2 Linear Amplitude Methods -- 4 Model Prediction as a Tool for Understanding -- 4.1 Revisiting Step Effects on TS-Dominated Transition -- 4.2 Gap Effects on TS-Dominated Transition -- 5 Conclusions -- References -- 40 Years of Transition Research at NASA: A Personal Perspective -- 1 Introduction -- 2 Computational Methods for Compressible Stability Analysis -- 3 2D Partial-Differential Eigenvalue Problem -- 4 Linearized Navier-Stokes -- 5 Parabolized Stability Equations -- 6 Development of Quiet Tunnels -- 7 Supersonic and Hypersonic Boundary Layer Transition -- 8 Cone/Flat-Plate Transition Reynolds Number Controversy -- 9 Effect of Bluntness and Real Gas on Hypersonic Boundary Layer Transition -- 10 Instability of Rotating Disk Flow -- 11 Nonlinear Development of Görtler and Crossflow Vortices -- 12 The Attachment-Line Boundary Layer -- 13 Epilogue -- References -- Progress in Stability and Transition Research -- 1 Introduction -- 2 Personal Areas of Research -- 3 Verification and Validation -- 3.1 Verification -- 3.2 Validation -- 4 Summary -- References -- Progress in Development of Amplitude Method of Transition Prediction on Swept Wing -- 1 Introduction