鏡像法に基づく回転翼機における地面効果モデル

抄録

It is widely known that the aerodynamic characteristics of a rotor change near the ground. This phenomenon is called ground effect. The ground effect affects flight stability at low altitudes. This study aims to realize a stable flight for rotorcraft near the ground. Toward this goal, we have proposed a ground effect model of a single rotor in hovering near the ground. This paper presents a detailed derivation of the proposed model. The proposed model is the same as Joseph's model in that two vortices represent the rotor. The difference is the process of deriving the representative velocity. The model by Joseph et al. makes assumptions that are not physically or mathematically reasonable. The proposed method derives a ground effect model from the induced velocity distribution induced by the two vortices. The effective blade length physically corresponds to the fact that blade tip losses are considered in the model. We validated the proposed model by measuring the thrust of a single rotor. Furthermore, experimental results show that blade shape affects the strength of the ground effect. The proposed method can represent the strength of the ground effect by using the effective blade length. In the experiment, the ground effect was smaller for blades with smaller blade tips, and this phenomenon corresponds to the proposed model. On the other hand, a phenomenon that may be due to the combined effects of approaching the ground was also evident. Investigation of this phenomenon is a future issue.