Aero-Optical Effects: Physics, Analysis and Mitigation

ISBN-13: 9781119037170 / Angielski / Twarda / 2023 / 300 str.

Jumper, Eric

Opis

This book provides a detailed introduction to aero-optics and describes the current understanding of physical causes of aero-optical effects from turbulent flows at different speeds. The book presents a thorough discussion of instrumentation and data reduction and analysis. The authors examine various approaches to mitigate aero-optical effects using both flow control and adaptive optics approaches.

Spis treści

Acknowledgements ix1 Introduction 11.1 Motivation for Revisiting Aero-Optics 22 Fundamentals 72.1 Wavefronts and Index of Refraction 72.2 Huygens' Principle 82.3 Basic Equations and Optical Path Difference 112.4 Linking Equation 152.5 Image at a Focal Plane (Far-field Propagation) 172.6 Far-field Intensity in the Presence of Near-field Distortions 202.6.1 Temporal Intensity Variation 252.7 Wavefront Components 263 Measuring Wavefronts 313.1 Interferometry Methods 313.2 Wavefront Curvature Methods 333.3 Gradient-based Wavefront Sensors 353.3.1 Shack-Hartmann Wavefront Sensor 373.3.1.1 Wavefront Reconstruction Algorithm 413.3.2 Malley Probe 433.3.3 SABT Sensor 463.4 Typical Optical Set-Ups 474 Data Reduction and Interpretation 554.1 Statistical Analysis 564.1.1 Temporal and Spatial OPD rms 564.1.2 Histograms and Higher-Moment Statistics 584.2 Spectral Analysis 604.2.1 Relation between the Deflection Angle Spectrum and the Wavefront Statistics 624.2.2 Dispersion Analysis 634.3 Modal Analysis 654.3.1 Zernike Functions 664.3.2 Proper Orthogonal Decomposition (POD) 704.3.2.1 Direct Method 734.3.2.2 Snapshot Method 744.3.3 Dynamic Mode Decomposition (DMD) 824.4 Cross-correlation-based Techniques 854.4.1 Local Convective Speeds 854.4.2 Multi-point Malley Probe Analysis 894.4.3 Spatially Varying 2-D Convective Velocity 925 Aperture Effects 976 Typical Aero-Optical Flows 1056.1 Scaling Arguments 1056.2 Free Shear Layers 1066.2.1 Shear-Layer Physics 1066.2.2 Aero-Optical Effects 1096.2.3 Historical Shear Layer Measurements in AEDC 1106.2.4 Weakly Compressible Model 1146.3 Boundary Layers 1186.3.1 Model of Aero-optical Distortions for Boundary Layers with Adiabatic Walls 1226.3.2 Angular Dependence 1306.3.3 Finite Aperture Effects 1326.3.4 Nonadiabatic Wall Boundary Layers 1336.3.5 Instantaneous Far-Field Intensity Drop-Outs 1426.3.5.1 Absolute SR Threshold 1476.3.5.2 Relative Intensity Variation 1506.4 Turrets 1526.4.1 AAOL 1546.4.2 Flow Topology and Dynamics 1596.4.3 Steady-lensing Effects at Forward-looking Angles 1676.4.4 Aero-optical Environment at Back-looking Angles 1696.4.5 Shock-effects at Transonic Speeds 1727 Aero-Optical Jitter 1797.1 Local and Global Jitter 1807.1.1 Local Jitter 1807.1.2 Global Jitter 1807.2 Subaperture Effects 1837.3 Techniques to Remove the Mechanically Induced Jitter 1837.3.1 Cross-correlation Techniques 1847.3.2 Large-Aperture Experiments 1867.3.3 Stitching Method 1878 Applications to Adaptive Optics 1958.1 Beam-Control Components 1958.2 How Much Correction Is Needed 1988.3 Flow-Control Mitigation 1988.3.1 Non-Flow-Control Mitigation 1998.3.2 Some Qualities of Separated Shear Layers 2008.3.3 Using the POD Analysis to Develop Requirements 2048.4 Proper Number of Wavefront Sensor Subapertures to Actuator Ratio 2088.4.1 Numerical Simulation 2098.4.2 Simulation Results 2118.4.3 Conclusion from the Simulation Results 2139 Adaptive Optics for Aero-Optical Compensation 2179.1 Analogies from Free-Stream Turbulence Compensation 2179.1.1 Statistical Optics Theoretical Considerations 2179.1.2 Power-Law Observations from Aero-Optical Wavefront Data 2199.2 Compensation Scaling Laws for Aero-Optics 2229.2.1 Adaptive Optics Control Law and Error Rejection Transfer Function 2229.2.2 Asymptotic Results for Aero-Optics Compensation 2239.2.3 Aero-Optics Compensation Frequency 2259.2.4 Relation of Aero-Optics Scaling Laws to Free-Stream Turbulence 2279.3 Spatial and Temporal Limitations of Adaptive Optics 2289.3.1 Framework for Analysis of Aero-Optical Compensation 2289.3.2 Deformable Mirror Fitting Error for Aero-Optical POD Modes 2299.3.3 Decomposition of Correctable and Uncorrectable Power Spectrum 2339.3.3.1 DM Sensitivity Transfer Function 2339.3.4 Closed-Loop Residual Wavefront Error 2349.3.5 Effect of Latency in Aero-Optics Compensation 2369.4 Application to System Performance Modeling 2389.4.1 Scaling of Aero-Optical Statistics to Flight Conditions 2399.4.2 Joint Variations in Adaptive Optics Bandwidth and Actuator Density 2399.4.3 Relative Impact of Aero-Optics with Other Propagation and System Effects 2449.4.3.1 Comparing Aero-Optics to Free-Stream Turbulence Propagation 2459.4.3.2 Comparing Aero-Optics to System Optical Jitter 2469.4.4 Tracker Performance Degradations Related to Aero-Optics 2489.4.4.1 Track Sensor Aero-Optical Imaging Resolution Degradation 2499.4.4.2 Illuminator Propagation and Active Imaging through Aero-Optics 25010 Concluding Remarks 255References 259Index 271

O autorze

Stanislav Gordeyev is an Associate Professor at the Department of Aerospace and Mechanical Engineering at the University of Notre Dame. His expertise includes the investigation of aero-optical distortions caused by compressible turbulent flows around airborne systems.Eric J. Jumper is the Roth-Gibson Professor of Aerospace and Mechanical Engineering at the University of Notre Dame. Although he has performed research in a wide range of topics, his present principal research focus is on the understanding of aero-optical phenomena.Matthew R. Whiteley, PhD, is Vice President and Senior Scientist at MZA Associates Corporation in Dayton, Ohio. His research includes aero-optical beam control and sensing of atmospheric turbulence for laser propagation.