Analysis, Design & Test of Low Reynolds Number Rotors and Propellers

The successful development of unmanned air vehicles (UAVs) has allowed aeronautical design to proceed without the limitations that are inherent to manned vehicles. As a result, extremely small UAVs are currently under development, including both aircraft and rotorcraft. Also, UAVs are being designed to work at extremely high altitudes, or in extraterrestrial environments with extremely thin atmospheres, such as Mars. UAVs that are small in size or operate in extremely low-density environments experience much lower Reynolds numbers than do conventional aircraft. Since aeronautical CFD has been mostly concentrated on high-Reynolds-number flows, the aerodynamics and computational simulation at low Reynolds numbers are poorly understood. These flows may exhibit combinations of laminar, transitioning, and fully turbulent flows (and may include compressibility effects) that present challenges to both experimental and computational disciplines. A practical analysis and design tool is proposed for three-dimensional low-Reynolds-number flows. The approach is based on vorticity confinement, a CFD approach that allows viscous effects to be modeled with relatively coarse grids and low computational requirements. Vorticity confinement allows vortical structures, such as separating boundary layers, to persist and be convected in a physically consistent manner. This effort extends the vorticity confinement approach to the low-Reynolds-number flow regime.