gas manipulation and diagnostics of aerospace flows using optical lattices

199 Pages·2014·8.13 MB·English

GAS MANIPULATION AND DIAGNOSTICS OF AEROSPACE FLOWS USING
OPTICAL LATTICES
by
JACOB STEPHEN GRAUL
B.S., University of Rochester, 2007
M.S., University of Colorado Colorado Springs, 2012

A dissertation submitted to the Graduate Faculty of the
University of Colorado Colorado Springs
in partial fulfillment of the
requirements for the degree of
Doctor of Philosophy in Engineering
Department of Mechanical and Aerospace Engineering
2014
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Copyright By Jacob Stephen Graul 2014
All Rights Reserved
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This dissertation for the Doctor of Philosophy degree by
Jacob Stephen Graul
has been approved for the
Department of Mechanical and Aerospace Engineering
by

__________________________
Taylor C. Lilly, Chair

__________________________
Andrew D. Ketsdever

__________________________
Russell M. Cummings

__________________________
Randall J. Knize

__________________________
John R. Adams

Date ___________________
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Graul, Jacob Stephen (Ph.D., Engineering)
Optical Lattice Gas Manipulation and Diagnostics of Aerospace Flows
Dissertation directed by Professor Taylor C. Lilly

Optical lattices, the optical interference pattern created by the superposition of two counterpropagating
laser pulses, have in recent years become a promising gas manipulation and diagnostic instrument. Recently,
optical lattices have experimentally shown the capacity, in contrast to its more recognizable gas cooling
application, to non-resonantly facilitate energy deposition into a gas. While previous numerical studies have
attributed temperature changes on the order of several thousand Kelvin to the technique, these temperature
changes have not been verified experimentally. Given realistic experimental and current laser-based
limitations, such temperatures are not likely to be realized using a single-shot implementation. This work
numerically examined, using Direct Simulation Monte Carlo, optical lattice gas heating potential in two
multipass optical cavities, as well as under the influence of a chirped laser. With the inclusion of realistic
laser and gas parameters, the numerical results of these simulations suggest that the best case gas temperature
increases, from a 300 K initial condition, are 763 K, 715 K, and 1018 K in nitrogen, argon, and methane,
respectively. In an effort to address the lack of quantitative measurement of lattice-gas energy deposition,
this work has proposed the use of a double shot, optical lattice experimental setup and gas temperature
measurement approach based on coherent Rayleigh-Brillouin scattering (CRBS). Presenting the first
experimental report of broadband CRBS as applied to the measurement of translational temperatures of
collisional gases (N , Ar, CH ), this work shows that CRBS is capable of measuring gas temperatures with a
2 4
fidelity consistent with that required for the experimental quantification of optical lattice gas heating.

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DEDICATION

For my wonderful mother.

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ACKNOWLEDGEMENTS
I wish to recognize my advisor and friend―Dr. Taylor Lilly, for his guidance throughout this project.
Dr. Lilly has graciously invested every possible resource to further this author’s intellectual development,
experimental technique, and appreciation for the scientific and ethical responsibility that natural philosophers
have to humanity. I am most grateful for his mentorship these last several years, and I owe much of my
professional success to Dr. Lilly. I would also like to thank Dr. Sergey Gimelshein for his enlightening
discussions of DSMC and gas dynamics. Without access to the preeminent expertise of Dr. Lilly and Dr.
Gimelshein, it is unlikely this project would enjoy both the experimental and numerical success that is has.
I would also like to acknowledge Dr. Andrew Ketsdever and Dr. Rebecca Webb. I would not have had the
opportunity or ability to perform this fascinating work without these exceptional role models. I also wish to
thank Dr. Barry Cornella for his patience, advice, and insight. Dr. Cornella helped immensely during the
initial phase of this work, and his demeanor and work ethic has provided me with a gold standard for future
endeavors. I would also like to thank my committee―Dr. Lilly, Dr. Ketsdever, Dr. Cummins, Dr. Knize,
and Dr. Adams, for their insight and assistance throughout this process. In particular, I wish to convey my
appreciation to Dr. Adams for his careful, and immensely helpful, reading of this document. Lastly, I wish
to express my gratitude for my fellow graduate students with whom I have developed wonderful relationships
the last few years. Although there are too many to list here, I would like to specifically recognize Dr. Carlos
Maldonado, Austin Ventura, Connor Campbell, Sean Zeeck, and Garrett Dietz. Thank you all for your
friendship, and I look forward to watching your continued success.

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TABLE OF CONTENTS
CHAPTER 1.  INTRODUCTION .............................................................................................................. 1 
A.  Motivation ................................................................................................................... 2 
B.  Prior Gas Heating Work .............................................................................................. 7 
C.  Investigation of Implementation ................................................................................ 13 
CHAPTER 2.  OPTICAL LATTICE GAS HEATING THEORY ........................................................... 16 
A.  Laser Interactions ...................................................................................................... 16 
B.  Optical Lattice Gas Heating ....................................................................................... 25 
CHAPTER 3.  NUMERICAL METHODS AND VALIDATION ........................................................... 49 
A.  DSMC Background ................................................................................................... 51 
B.  Prior Validation of SMILE ........................................................................................ 53 
C.  SMILE Code .............................................................................................................. 57 
CHAPTER 4.  OPTIMIZATION: OPTICAL CAVITIES ........................................................................ 67 
A.  Optical Cavity Background ....................................................................................... 68 
B.  Proposed Cavities ...................................................................................................... 72 
C.  Results and Discussion .............................................................................................. 76 
CHAPTER 5.  OPTIMIZATION: LASER CHIRP .................................................................................. 84 
A.  Chirped Laser Background ........................................................................................ 84 
B.  Laser-based Optimization .......................................................................................... 86 
C.  Results and Discussion .............................................................................................. 86 
CHAPTER 6.  COHERENT RAYLEIGH-BRILLOUIN SCATTERING DIAGNOSTICS .................. 105 
A.  Theoretical Framework ............................................................................................ 107 
B.  Experimental Setup .................................................................................................. 109 
C.  Spectral Analysis ..................................................................................................... 112 
D.  Temperature Diagnostic Results .............................................................................. 119 
E.  Flow Velocity Results ............................................................................................. 122 
F.  Application to Optical Lattice Gas Heating ............................................................. 123 
CHAPTER 7.  CONCLUSION............................................................................................................... 127 
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BIBLIOGRAPHY ....................................................................................................................................... 130 
APPENDIX A: N DSMC CAVITY OPTIMIZATION HEATING RESULTS ....................................... 138 
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APPENDIX B: N DSMC LASER OPTIMIZATION HEATING RESULTS .......................................... 158 
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APPENDIX C: AR DSMC LASER OPTIMIZATION HEATING RESULTS ......................................... 164 
APPENDIX D: CH DSMC LASER OPTIMIZATION HEATING RESULTS ....................................... 167 
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APPENDIX E: CRBS SIGNAL SPECTRAL ANALYSIS CODE ............................................................ 169 
APPENDIX F: CRBS SIGNAL SPECTRAL RESULTS .......................................................................... 179 

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TABLES
Table 2.1: Analytical optical lattice gas heating efficiencies of N .............................................................. 38 
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Table 3.1: DSMC SMILE gas-specific simulation parameters .................................................................... 58 
Table 3.2: DSMC SMILE laser parameters .................................................................................................. 60 
Table 3.3: Kinetic gas properties at 0.8 atm and 300 K ............................................................................... 61 
Table 6.1: Values used in the production of CRBS line shape models for N , Ar, and CH . ..................... 118 
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FIGURES
Figure 1.1: Notional illustration of a one-dimensional optical lattice ............................................................ 2 
Figure 1.2: Numerical and analytical predictions of (a) energy and (b) momentum deposition as a function
of lattice velocity and intensity in air [32] ....................................................................................................... 8 
Figure 1.3: Nitrogen and methane end pulse (a) temperature and (b) induced bulk velocity following a 50 ps
pulse [3] ........................................................................................................................................................... 9 
Figure 1.4: Methane (a) gas velocity and (b) temperature increases for a 700 m/s lattice velocity at pressures
of 1390 , 13920, and 139200 Pa [4] .............................................................................................................. 10 
Figure 1.5: Simulated nitrogen translational temperature as a function of pulse number [35] ..................... 11 
Figure 1.6: Overall temperature of argon, nitrogen and methane obtained after 10 pulses [5] .................... 12 
Figure 1.7: Measured acoustic wave strength as a function of lattice velocity for (a) 300 K N and (c) 300 K
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CH alongside DSMC predictions [2, 36] ..................................................................................................... 13 
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Figure 2.1: Maximum optical lattice-induced dipole force in the (a) axial and (b) radial directions for N , Ar
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and CH under the laser parameters simulated in this work .......................................................................... 23 
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Figure 2.2: N density gradient over the 532 nm domain at various times within a 5 ns FWHM pulse as found
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through DSMC simulation ............................................................................................................................ 24 
Figure 2.3: Perturbation to collisionless gas velocity distribution resulting from an optical lattice with
velocity ξ [39]................................................................................................................................................ 28 
Figure 2.4: (a) Perturbed DSMC velocity distribution of collisional N in the axial direction compared to
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equilibrium distribution with (b) the difference between these distributions shown ..................................... 29 
Figure 2.5: 300 K nitrogen distribution derivatives as a function of velocity indicating optimal lattice
velocities for (a) energy and (b) momentum deposition ................................................................................ 32 
Figure 2.6: Nanosecond end pulse axial translational temperature as a function of lattice velocity in nitrogen
initially at 300 K ............................................................................................................................................ 33 
Figure 2.7: Translational temperature difference as a function of non-dimensional gas velocity shown by
laser chirp ...................................................................................................................................................... 34 
Figure 2.8: N final temperature as a function of single beam intensity for a single optical lattice pulse [36]
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....................................................................................................................................................................... 36 
Figure 2.9: Schematic of experimental setup with power meter to measure the impact of Bragg scattering on
post-interaction pump energies [54] .............................................................................................................. 39 
Figure 2.10: Experimentally-measured pump energy post-interaction versus laser frequency difference [54]
....................................................................................................................................................................... 40 
Figure 2.11: Comparison of experimental results with numerical prediction versus laser frequency difference
[54] ................................................................................................................................................................ 43 
Figure 2.12: DSMC SMILE calculation of the velocity distribution at the centerline of the perturbed gas at
the end of a 5 ns pulse, consistent with the experimental conditions [54] ..................................................... 45 
Figure 2.13: Nitrogen end pulse bulk velocity as a function of lattice velocity ........................................... 46 
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