An aerofoil component defines an in use leading edge and a trailing edge. The leading edge has at least one serration defining an apex and a nadir. The leading edge has a generally chordwise extending slot located at the nadir of each serration.

The present disclosure provides a method and system for determining a helicopter rotor airfoil. The method includes: randomly generating a sample point by using a Latin hypercube sampling (LHS) method (S1); determining characterization equations of upper and lower airfoil surfaces of an airfoil based on the airfoil sample point by using a class shape transformation (CST) method (S2); performing dynamic characteristic simulation on the airfoil according to the characterization equations of the upper and lower airfoil surfaces by using a computational fluid dynamics (CFD) method, to obtain a flow field characteristic of the airfoil (S3); establishing a mapping relationship between the sample point and the flow field characteristic by using a Kriging model, and training the mapping relationship by using a maximum likelihood estimation method and an expected improvement (EI) criterion, to obtain a trained mapping relationship (S4); determining an optimal sample point based on the trained mapping relationship by using Non-dominated Sorting Genetic Algorithm II (NSGA-II) (S5); and determining a rotor airfoil based on the optimal sample point (S6). The method performs optimized design on aerodynamic characteristics of the airfoil in a state with a changing incoming flow and a changing angle of attack, and can effectively alleviate dynamic stall in this state.

A motor includes a fixed shaft, a first rotor supported by the fixed shaft in a rotatable manner relative to the fixed shaft, a first stator fixed to the fixed shaft and applying rotation torque that rotates the first rotor toward one side in a circumferential direction of the fixed shaft, a second rotor provided at a position different from a position of the first rotor in an axial direction in a rotatable manner relative to the fixed shaft, and a second stator fixed to the fixed shaft and applying rotation torque that rotates the second rotor toward another side in a circumferential direction of the fixed shaft.

A motor includes a fixed shaft, a first rotor supported by the fixed shaft in a rotatable manner relative to the fixed shaft, a first stator fixed to the fixed shaft and applying rotation torque that rotates the first rotor toward one side in a circumferential direction of the fixed shaft, a second rotor provided at a position different from a position of the first rotor in an axial direction in a rotatable manner relative to the fixed shaft, and a second stator fixed to the fixed shaft and applying rotation torque that rotates the second rotor toward another side in a circumferential direction of the fixed shaft.

A fluid-redirecting structure includes a rigid body having an upstream end, a downstream end, and an axis of rotation, the rigid body incorporating a plurality of troughs each spiralled from a tip at the upstream end to the downstream end about the axis of rotation, the troughs being splayed with respect to the axis of rotation thereby to, proximate the downstream end, direct incident fluid along the troughs away from the axis of rotation.

A structure adapted to traverse a fluid environment includes an elongate body having a root, a wingtip, a leading edge and a trailing edge; and a rigid winglet associated with the wingtip and having a winglet body extending substantially normal to one of a suction side and a pressure side of the elongate body to a termination point that is rearward of the trailing edge. In an embodiment, the structure is a rotor blade that may be incorporated into a wind turbine.

Sounds are generated by an aerial vehicle during operation. For example, the motors and propellers of an aerial vehicle generate sounds during operation. Disclosed are systems, methods, and apparatus for actively adjusting the position and/or configuration of one or more propeller blades of a propulsion mechanism to generate different sounds and/or lifting forces from the propulsion mechanism.

The ‘Air Wheel’ rotor is a rotor with blades of variable pitch and variable twist. The ‘Air Wheel’ rotor comprises one or more hubs connected to the closed axisymmetric wing via flexible blades. There is provided a wide range of combinations of the wing relative width and coning angle typical for a lifting rotor with a thin planar wing attached to the tips of long blades, for a shrouded fan in a wide annular wing, or an impeller in a rotating cylindrical wing is provided.

The ‘Air Wheel’ rotor combines and enhances the advantages of a rotor and a wing. The ‘Air Wheel’ rotor has high aerodynamic properties, and eliminates limitations of the rotor size and flight speed. The ‘Air Wheel’ rotor can be used for designing vertical take-off and landing aircraft.

The ‘Air Wheel’ rotor is a rotor with blades of variable pitch and variable twist. The ‘Air Wheel’ rotor comprises one or more hubs connected to the closed axisymmetric wing via flexible blades. There is provided a wide range of combinations of the wing relative width and coning angle typical for a lifting rotor with a thin planar wing attached to the tips of long blades, for a shrouded fan in a wide annular wing, or an impeller in a rotating cylindrical wing is provided.

The ‘Air Wheel’ rotor combines and enhances the advantages of a rotor and a wing. The ‘Air Wheel’ rotor has high aerodynamic properties, and eliminates limitations of the rotor size and flight speed. The ‘Air Wheel’ rotor can be used for designing vertical take-off and landing aircraft.

A propeller having a means for creating fluid flow in a non-axial direction and redirecting it in an axial direction.