Coaxial rotor helicopter in hover based on unstructured dynamic overset grids

The three-dimensional unsteady Euler equations solved to simulate the unsteady flows around coaxial rotor helicopter and individual-rotor helicopter in hover based on the unstructured dynamic overset grids are examined. The rotor blades are made of NACA0012 airfoil section and have a rectangular shape with an aspect ratio of 12.98 with the root cutout at 24% of the radius. The blades have no linear twist and the forward tilt angle of the rotor shaft is 0 deg. The fluctuation amplitudes of the coaxial rotor thrusts are larger than those of the individual rotor, while the fluctuation amplitudes of the top rotors are a little larger than those of bottom rotors. The interaction between the coaxial rotors makes the downwash velocity at the bottom rotor plane much larger than that at the individual-rotor plane, and the downwash velocity at the top rotor plane is a little larger than that at the individual-rotor plane.