Alexandros Gerakis: USING NON-LINEAR OPTICS TO SHINE LIGHT ON AEROSPACE ENGINEERING CHALLENGES
Sir Horace Lamb famously said that “I am an old man now, and when I die and go to heaven, there are two matters on which I hope for enlightenment. One is quantum electrodynamics and the other is the turbulent motion of fluids. About the former, I am really rather optimistic.” Although nowadays we can travel in less than a day’s time from Perth, Australia to London, UK, and from Newark, USA to Singapore, there are still many open scientific questions in the aerospace engineering realm, especially when it comes to supersonic and hypersonic flight. Mastering hypersonic wind tunnels is one key component of the research involved but advanced, accurate and non-perturbative diagnostics is another key part. In this talk I will discuss laser diagnostic efforts developed to tackle the latter, by concentrating on the research efforts of our group in this field by utilizing Coherent Rayleigh-Brillouin scattering (CRBS).
CRBS is a four-wave mixing diagnostic technique that relies on the creation of an optical lattice in a medium due to the interaction between polarizable particles and intense laser fields. Single shot CRBS1 has already been demonstrated to be the coherent analog of spontaneous Rayleigh-Brillouin scattering in measuring the temperature, pressure, bulk and shear viscosity, speed of sound and polarizability of a gas or gas mixture2. Additionally, in situ measurements of ~5 nm nanoparticles produced in an arc discharge have been facilitated with CRBS3. In this talk, an overview on the theory and experimental aspects of single shot CRBS will be presented. Furthermore, I will discuss the feasibility and working progress towards the use of single shot coherent Rayleigh-Brillouin scattering (CRBS) as a gas flow and temperature measuring technique, with anticipated measurable velocities down to 5-10 ms-1, applicable to atomic and molecular gases, gas mixtures, as well as partially ionized gases.