Full-Vehicle Hierarchical Design Model for VTOL UAVs and Manned Rotorcraft

To fulfill the mission performance requirements for the coming generation of Army VTOL UAVs and manned rotorcraft, design tools are required that can encompass both the wide range of possible multirotor configurations and the technical challenges ofanalyzing realistic, integrated airframes. In addition to design issues shared with full scale rotorcraft, small rotary wing UAVs are constrained by rotor performance limitations inherent in operating at low Reynolds numbers and subsonic Mach number, aswell as complex effects such as multiple rotor aerodynamics, duct interaction, sidewinds, and rotor/empennage interaction. The effort proposed here will address these problems by exploiting the established full-airframe modeling capabilities of the CHARMcomprehensive model while introducing enhancements and innovations tailored to the environment of low Reynold number rotorcraft. In particular, the fast boundary element and vortex modeling in CHARM will be supplemented by state of the art finite volumemethods to capture challenging real flow effects arising from turbulent and viscous mechanisms. The effort will include validation studies for isolated rotors, multiple rotors, and representative ducted systems, and will lay the groundwork for eventualdevelopment of an integrated model incorporating improved viscous modeling capabilities as part of a hierarchy of full-vehicle design tools. The recent rapid expansion of unmanned rotorcraft roles in Army and other DOD applications (e.g., the UCAR and OAVprograms) will offer a range of opportunities for use of this design software in supporting prime contractors. Strong growth is also evident in civil rotary wing/UAV concepts, including surveillance, imaging, and inspection roles, and the design andanalysis capabilities to be developed here can directly support these new initiatives.