Research

My primary research project is an experimental investigation into a fundamental problem in compressible flow: measuring and characterizing the laminar to turbulent transition process in boundary layer flows in thermochemical nonequilibrium at high enthalpy. Higher thermal loads, by half an order of magnitude or more, result from the increased heat transfer due to turbulent flow, so laminar to turbulent transition is a critically important process in the design of hypervelocity vehicles, such as re-entering spacecraft and high-speed scramjet testbeds.

In this flow regime, where the second or Mack mode instability dominates, nonequilibrium effects for certain species (in our work, carbon dioxide) can actually suppress transition through the absorption of energy from acoustic disturbances through vibrational relaxation.

We measure the propagation and growth of turbulent spots within the boundary layer, characterize transition delay for flows in air with increasing mass fractions of carbon dioxide, and also investigate the efficacy of gas injection mechanisms into the hypervelocity boundary layer for inhibiting second mode transition, with the goal of gleaning useful data to be exploited in future aerospace vehicles.

I have also performed substantial research on multiphase flows with Prof. Chris Brennen, including the identification and characterization of two mechanisms for gas bubble release in granular beds, which has applications in aquatic ecology as well as climate modeling (the mechanism is an important source of atmospheric methane), and a separate project on the speed of sound in bubbly mixtures.

I got my start in the Prof. Joseph E. Shepherd group working on the effect of porous thrust surfaces on detonation tube impulse, and more recently assisted in the development and implementation of optical techniques to observe free stream tunnel noise and boundary layer instability.

Other projects include the measurement of mechanical properties of polar-lipid vesicles with Prof. Rob Phillips at Caltech, and a study of ZBLAN microspherical resonators fabricated in microgravity in collaboration with NASA-JPL. The latter report (2002), which is to date unpublished, has nevertheless been cited in the Chinese Journal of Lasers (2008), an IEEE Photonics conference paper (2012), and US Patent No. 8389958 (2013).