垂直オートローテイション時のロータまわりの流れ場の可視化実験とその応用

抄録

It is well recognized that the autorotation capability of a rotor plays a fundamental role in the flight safety of a helicopter following power failure. Although the vertical autorotation is a basic steady free flight mode of an isolated rotor descending in the air, there is little research to investigate its aerodynamic and dynamic behaviours by taking the wake deformation into account. In this research, to grasp quantitatively the wake structures of a rotor in the vertical autorotation and to develop a reasonable wake model to be consistent with steadiness of the descending motion, flow visualization studies for model rotors are conducted. Pictures obtained by visualization studies show clearly the facts that regular and steady flow fields are formulated around the rotor in the vertical autorotation state, and this aerodynamic working condition is different from the vortex ring or the turbulent wake state defined by the classical rotor aerodynamics. Based on flow visualization results, a simplified wake model which represents dominant tip and root helical vortices by definite numbers of the circular ring vortices is proposed and several numerical analyses of the flow fields are carried out. Numerical results show good correration with those of visualization and wake survey by a hot wire anemometer.