Sidewall effects on aerodynamic characteristics of hexacopter rotor under low Reynolds number conditions – toward Martian pit creator exploration –

Exploration of pit creators on Mars is being planned to use a hexacopter. In this study, to investigate the aerodynamic characteristics of a hexacopter rotor operating near sidewalls under the low-Reynolds-number and high-Mach-number conditions of the Martian environment, numerical simulations were conducted using the CFD solver, rFlow3D. The Reynolds number and the Mach number at the blade tip were 10,000 and 0.77, respectively. Firstly, we examined the aerodynamic characteristics of a single rotor near a sidewall. When the distance from the sidewall to the blade tip falls below the rotor radius, the thrust and torque coefficients decrease significantly. This is caused by the decrease of the effective pitch angle of the blade on the wall side, resulting from the higher inflow velocity in the direction of the perpendicular to the rotational plane. Furthermore, these aerodynamic characteristics revealed that when a hexarotor operates near a sidewall, a thrust imbalance between the rotors closer to the wall and those farther away generates a pitching moment on the hexacopter. The moment makes the hexacopter tilt towards the wall. Comparison with Earth's environment under the same flight condition showed that a stronger pitching moment toward the wall was generated on Earth than that on Mars.