UC Irvine

Urban air mobility as a fast transportation solution has captured the attention of private companies and government aviation departments in the 21st century. The new designs of aerial vehicles are coming one after another but often neglecting the aerodynamic characteristics and the effect of interacting rotors. The Multirotor Test Bed (MTB) project was initiated at NASA Ames Research center to support the NASA Revolutionary Vertical Lift Technology (RVLT) Project to study rotorcraft performance specifically for multirotor aircraft. The MTB is a modular multirotor that can make testing feasible for up to six rotors at different angles and rotor arrangements, including tall and short configurations at different horizontal and vertical distances. The MTB is assembled and tested in the U.S Army’s 7- by 10-Foot Wind Tunnel. This work focuses on the importance of aerodynamic interaction between MTB rotors using the Comprehensive Hierarchical Aeromechanics Rotorcraft Model (CHARM) software, developed commercially by Continuum Dynamics, Inc. The CHARM software is capable of modeling Vertical Take Off and Landing (VTOL) aircraft aerodynamics in maneuvering and steady flight conditions. CHARM allows the user to define flow and body characteristics, including the rotor geometry, aerodynamic condition, wind tunnel speed, and airfoil tables as inputs. This report first examines CHARM’s capability by comparing its predictions to the UH-60A Black Hawk rotor and SUI Endurance rotor experimental test results in hover and forward flight conditions. These comparisons can help to validate CHARM results, provide a better understanding of simulated flight characteristics, and demonstrate its predictive capability. With these validations as the foundation, this work then simulates one MTB rotor in hover, and further compares with wind tunnel test data as the confirmation of the CHARM parameters. Once accurate performance is verified, the MTB rotor is simulated in forward flight both in the wind tunnel and in a free field environment. The simulation variables include one, two, four, and six rotors at the short and tall configurations, and with shaft angles of 0, -5, and -10 degrees. These results can demonstrate the rotor wake interaction and its impact on rotor performance. This information can also help determine which configurations should be explored for the future wind tunnel tests. This study can be used as guidance for using CHARM to predict rotor behavior and understanding the importance of the rotor wake interaction for future air mobility designs.