With the development of urban air mobility (UAM) vehicles, in the near future people might be offered rides in air taxis across large cities. NASA supports the development of this revolutionary market in aviation by studying multiple new designs of vertical take-off and landing (VTOL) vehicles for a variety of missions, ensuring they will operate safely and efficiently. Many VTOL aircraft concepts developed at NASA have rotors, just like helicopters. The aerodynamic interactions between the rotors and other components, like the fuselage or wings, must be quantified to accurately predict flight performance. Studying these complex interactions while vehicles are still being developed requires high-fidelity computational fluid dynamics (CFD). Aerospace engineers at NASA’s Ames Research Center are performing CFD simulations of rotors and air taxis in “ground effect,” where the addition of a ground surface makes simulations more challenging, substantially increasing the size of the computational grids compared to those simulating the vehicle alone.