Dr. Varoutis's research interests span a broad range of topics, including gas flows far from local equilibrium (rarefied gas dynamics), computational and experimental fluid mechanics, deterministic and stochastic numerical methods for the Boltzmann and model kinetic equations, direct simulation Monte Carlo (DSMC) techniques, high-speed and high-altitude aerothermodynamics, micropropulsion, gas-phase effects in NEMS-MEMS devices, vacuum gas dynamics, and the modeling, analysis, and design of vacuum systems. His work also focuses on edge plasma physics and neutral particle transport with applications in the exhaust systems of Tokamak and Stellarator fusion devices.