On binary scaling and ground-to-flight extrapolation in high-enthalpy facilities Guerric de Crombrugghe de Looringhe BSc, MSc in Engineering MRes in Aeronautics and Aerospace A thesis submitted for the degree of Doctor of Philosophy at The University of Queensland in 2016 School of Mechanical and Mining Engineering Abstract The binary scaling law is commonly used to study the aerothermodynamics of hypersonic vehi- cles in high-enthalpy facilities. It enables the duplication of the shock layer in the vicinity of the stagnation point, including binary chemistry and nonequilibrium processes, through the reproduction of the Péclet and wall Damköhler numbers. These are both conserved through the duplication of the composition of the gas, the free-stream enthalpy h1 and the product of a density and a length-scale of the flow ρL. Binary scaling is built on the assumption of a flow devoid of radiation coupling and governed by binary reactions. These two conditions drastically narrow down the envelope of flows for which binary scaling can be used. Moreover, diffusive transport and wall chemistry have never been addressed although they can have an important impact on the wall heat flux. The first part of this thesis consists in an effort to better understand the theoretical role and effect of the different assumptions done to build the binary scaling. It is first shown that diffusive transport and wall chemistry should scale appropriately. Second, that non-binary chemistry will cause the shock layer in the laboratory flow to be hotter and less dissociated. A methodology is proposed to identify clearly what free-stream conditions will affect the least the flow variables of interest. Lastly, that radiation coupling will be weaker in the laboratory flow than in flight, causing the enthalpy contained in the shock layer to be greater in the laboratory flow. These findings are verified in the second part with two experiments. The first experiment was performed in the Plasmatron plasma wind tunnel at the von Karman Institute, Belgium. Binary scaled boundary layers were obtained for flows where diffusion and wall chemistry contribute significantly to the heat flux. The stagnation point heat fluxes were measured and exhibit a good agreement with the theoretical scaling law. This also validates the use of the binary scaling law in subsonic high-enthalpy facilities. The second experiment was performed in the X2 expansion tube at the Centre for Hypersonics, Australia. Three flows were obtained over cylinders of different radii, adapting the free-stream density according to the binary scaling law. The free-stream conditions were determined in order to ensure a significant radiative coupling. Its effect could clearly be identified through measurements of the shock standoff distance, stagnation point heat flux, and shock layer radiation. A new method, based on a mix of experiments, computational fluid dynamics, and informed use of engineering correlations is proposed to perform ground to flight extrapolation for cases for which the radiative coupling is non-negligible. 4 Declaration by author This thesis is composed of my original work, and contains no material previously published or written by another person except where due reference has been made in the text. I have clearly stated the contribution by others to jointly-authored works that I have included in my thesis. I have clearly stated the contribution of others to my thesis as a whole, including statistical assistance, survey design, data analysis, significant technical procedures, professional editorial advice, and any other original research work used or reported in my thesis. The content of my thesis is the result of work I have carried out since the commencement of my research higher degree candidature and does not include a substantial part of work that has been submitted to qualify for the award of any other degree or diploma in any university or other tertiary institution. I have clearly stated which parts of my thesis, if any, have been submitted to qualify for another award. I acknowledge that an electronic copy of my thesis must be lodged with the University Library and, subject to the policy and procedures of The University of Queensland, the thesis be made available for research and study in accordance with the Copyright Act 1968 unless a period of embargo has been approved by the Dean of the Graduate School. I acknowledge that copyright of all material contained in my thesis resides with the copyright holder(s) of that material. Where appropriate I have obtained copyright permission from the copyright holder to reproduce material in this thesis. 6 Publications during candidature Journal Papers de Crombrugghe, Morgan, R. G., and Chazot, O.“Theoretical Approach and Experimental Verifica- tion of the Role of Diffusive Transport under Binary Scaling Conditions”, International Journal of Heat and Mass Transfer, 97:675-682, June 2016. Reviewed Conference Papers de Crombrugghe, G., Gildfind, D., Zander, F., McIntyre, T. J., and Morgan, R. G., “Design of Test th Flows to Investigate Binary Scaling in High Enthalpy CO2 − N2 Mixtures”, 19 Australasian Fluid Mechanics Conference, December, Melbourne, Australia, 2014. Conference Papers de Crombrugghe, G., Morgan, R. G., McIntyre, T. J., and Zander, F., “ Experimental Duplication of Venus Atmospheric Entry Flow”, 11th NASA Venus Exploration Assessment Group (VEXAG) Meeting, November 19-21, Washington DC, U.S.A., 2013. Alba, C., Lewis, L., de Crombrugghe, G., Eichmann, T., Morgan, R. G., and Greedyke, R., “Investi- gation of Surface Radiation in Earth Re-Entry Flows with Graphite Ablation”, 6th Ablation Workshop, April 10-11 , Illinois, U.S.A., 2014. Publications included in this thesis de Crombrugghe, G., Gildfind, D., Zander, F., McIntyre, T. J., and Morgan, R. G., “Design of Test Flows to Investigate Binary Scaling in High Enthalpy CO2 − N2 Mixtures’,’ 19th Australasian Fluid Mechanics Conference, December, Melbourne, Australia, 2014. Content partly incorporated in chapter 6 and appendix G. 8 Contributor Statement of contribution de Crombrugghe, G. (Candidate) Original idea (100%) Designed the experiments (90%) Wrote the paper (100%) Gildfind, D. Designed the experiments (10%) Provided expert advice (25%) Zander, F. Provided expert advice (25%) Reviewed the paper (25%) McIntyre, T. J. Reviewed the paper (25%) Morgan, R. G. Provided expert advice (50%) Reviewed the paper (50%) de Crombrugghe, Morgan, R. G., and Chazot, O.“Theoretical Approach and Experimental Verifica- tion of the Role of Diffusive Transport under Binary Scaling Conditions”, International Journal of Heat and Mass Transfer, 97:675-682, June 2016. Content partly incorporated in section 2.4 and chapter 5. Contributor Statement of contribution de Crombrugghe, G. (Candidate) Original idea (100%) Designed the experiments (90%) Wrote the paper (100%) Morgan, R. G. Provided expert advice (50%) Reviewed the paper (50%) Chazot, O. Designed the experiments (10%) Provided expert advice (50%) Reviewed the paper (50%) Contributions by others to the thesis No contribution by others Statement of parts of the thesis submitted to qualify for the award of another degree No contribution by others 10 Acknowledgment These past few years have been full of new adventures and discoveries, both from the personal and professional point of view. The year 2013 started with an important step: moving down under. In 2014, I got married. In 2015, I received a dog and bought a house. In 2016, I am submitting my Ph.D. thesis. First and foremost, I would like to thank my supervisors. Richard Morgan is not only an incredibly knowledgable (shall I say erudite?) professor, he is also a very kind and sympathetic person. Richard gave me the opportunity to explore my own research topics while remaining available if I needed guidance. Olivier Chazot is both a man of science and a humanist. He gave me the taste for the things beyond science, and our discussions about research often drifted away towards philosophy. Both Richard and Olivier proved to be extremely flexible when personal matters forced me to adapt my work. Last but not least, I would like to thank Tim McIntyre. Our weekly meetings encouraged me to have some structured progress in my work. My deepest thanks then go to all these beautiful people I met at the Centre for Hypersonics. I will never forget my first day: no one knew a new student was arriving, there was no computer, no desk, nothing. A student wearing a T-shirt referring to a “Schnitzel run” (what could it possibly be?) gave me a pile of documents to read and wished me good luck. It was Fabian Zander. I immediately understood this was the start of my first friendship in Australia, many of which would follow. Students in the dungeon do not see the Sun very often and yet they cultivate a strong sense of cooperation and sharing. Allow me mention in particular those I spent the most time with: Elise Fahy, David Gilfind, Chris James, Steven Lewis, Hadas Porat, Jorge Sancho, Umar Sheikh, Pierpaolo Toniato, Han Wei, and Brad Wheatly. Then, there is the motorbike gang that took me out of the dungeon and made me discover the wonders of Queensland: Mathew Bricalli, Stefan Brieschenk, Dawid Preller, and Juanra Llobet. But I did not spend all my candidature in the dungeon. I must also thank the following people who contributed in one way or another to this work: Nikhil Banerji, Kevin Basore, David Buttsworth, Rowan Gollan, Bernd Helber, Peter Jacobs, Francesco Panerai, Isil Sakraker, Sandy Tirtey, Anabel del Val, Tristan Vanyai, and Dylan Wise. Finally, I would also like to express my warmest thanks to the technical staff for their amazing support during my experiments: Frans de Beurs and Keith Hitchcock at the University of Queensland, and Pascal Collin at the von Karman Institute. Lastly, I want to acknowledge the continuous encouragements through thick and through thin of my wonderful wife, Ysaline, and my stupid dog, Colette.