His research is in shock-driven hydrodynamic instabilities and supercritical CO2 heat transfer. His research uses both experiments and simulations to explore these areas. He has worked with Lawrence Livermore National Laboratory in high-energy density physics to study shock-driven variable density flows such as the Richtmyer-Meshkov instability in large scale simulations. This work has applications in inertial confinement fusion power and astrophysics. McFarland built a shock tube facility for his doctoral work and performed experiments of these shock-driven flows using high speed optical diagnostics such as Planar Laser Induced Fluorescence an Particle Imaging Velocimetry. He also has worked on experiments to study the heat transfer characteristics of supercritical carbon dioxide for use in concentrated solar power plants or next generation nuclear power plants.