The Influence of Rotor Overlapping Azimuth on Compound Coaxial Helicopter Performance Based on Unsteady CFD Simulation

In this paper, a computational fluid dynamics simulation method is developed to study the influence of rotor overlapping azimuth on aerodynamic performance compound coaxial helicopter. The verified by comparing numerical results with wind tunnel experiment data NASA rotor. Two azimuths upper and lower blades are considered, isolated helicopter in hover forward analyzed respectively. State 1 means overlap at 0/180° or 90/270°, state 2 45/225° 135/315°. It found that rotors not affected hover, but total thrust fluctuation amplitude 76.3% smaller than forward. hovering flight helicopter, compared 1, lift wing 42.7% smaller; flat tail 52.4% smaller. 83.5% 61.2% can be concluded working has better 1; changing high engineering application value, which increase stability reduce fluctuations.