In this report, we present the theory on aerodynamics of quadrotors using the well established momentum and blade element theories. From a robotics perspective, the theoretical development of the models for thrust and horizontal forces and torque (therefore power) are carried out in the body fixed frame of the quadrotor. Using momentum theory, we propose and model the existence of a horizontal force along with its associated power. Given the limitations associated with momentum theory and the inadequacy of the theory to account for the different powers represented in a proposed bond graph lead to the use of blade element theory. Using this theory, models are then developed for the different quadrotor rotor geometries and aerodynamic properties including the optimum hovering rotor used on the majority of quadrotors. Though this rotor is proven to be the most optimum rotor, we show that geometric variations are necessary for manufacturing of the blades. The geometric variations are also dictated by a desired thrust to horizontal force ratio which is based on the available motor torque (hence power) and desired flight envelope of the vehicle. The detailed aerodynamic models obtained using blade element theory for different geometric configurations and aerodynamic properties of the aerofoil sections are then converted to lumped parameter models that can be used for robotic applications. These applications include but not limited to body fixed frame velocity estimation and individual rotor thrust regulation [1, 2].
Aerodynamic performance enhancement and noise reduction for Darrieus vertical axis wind turbines: V-shaped blades and trailing-edge serrations
达里厄垂直轴风力机是城市风能利用的主流装置之一。市场对高风能转换效率的追求推动了在降低噪声的同时提高风力机功率系数的研究。本文对一种V形叶片和尾缘锯齿的小型垂直轴风力机的空气动力学和气动声学特性进行了进一步的研究。通过实验验证了采用雷诺平均Navier-Stokes SST k Ω湍流模型和FW-H方法的可行性。在正常风速条件下，V型叶片在较宽的叶尖速比范围内均能有效提高VAWT的功率性能，而尾缘锯齿也会略微提高VAWT在最佳叶尖速比下的功率输出。尾缘锯齿V型叶片风力机的功率系数比原风轮提高了28.3%。此外，与传统的椭圆分布相比，首次在垂直轴风力机中发现了哑铃形的噪声方向性分布。V型叶垂直轴风力机产生的低频噪声较小，尾缘锯齿实现了预期的降噪效果。本研究为高效率、低噪音风力机的设计提供了一种可行的解决方案。
