Numerical investigation of Reynolds number effects on rotor aerodynamic performances in hover

Abstract

The main topic that is investigated in the present research is the turbulent flow around small-scale rotor blades in hovering flight condition. Small-scale rotorcraft imply somewhat specific operating conditions such as low Reynolds numbers, considerable viscous effects, degraded aerodynamic performances, flow separation, rotational flow, cyclic load cases, etc. It is therefore very important to perform as accurate as possible flow simulations that will enable obtaining practical aerodynamic data that can be used in subsequent structural and flight mechanics analyses. This paper provides the description of steps that are to be conducted when simulating hovering flow. Here, a quasi-steady approach, that combines RANS equations closed by k-ω SST turbulence model with the multiple reference frames, is adopted. Both quantitative and qualitative results are presented. Furthermore, the numerical model is validated against the obtained experimental data. The correspondence between the two sets of results can be considered satisfactory (relative differences for thrust coefficient amount to 15%, while they are even lower for the torque coefficient), while the effects of Reynolds number are not significant when throttle is above 40%.