Falling rate prediction of the Petrea Volubilis winged seed by using the Blade Element Momentum theory (BEM)

Many winged seeds tend to use rotation as a flight mechanism, which reduces their falling rate and increases their wind dispersal distance (Azuma & Yasuda, 1989). Observations of their flights and the study of the shape of these rotating winged seeds have allowed researchers to conclude that they can be used as bio-inspired wind rotors (Castañeda Vergara, 2010; Correa-Álvarez et al., 2016). In a recent study on the Petrea Volubilis winged seed  (Gaitan-Aroca et al., 2020), which has five petals, performance coefficients have been experimentally determined in a scaled seed model. However, the winged seed tip speed ratio, which is closely related to its falling rate and defines its efficiency as a rotor, is unknown.
This article shows the Petrea Volubilis winged seed falling rate prediction by means of the BEM theory. This theory is implemented through a computational code as the basis for the calculation of this winged seed aerodynamic performance. The input parameters for the falling rate prediction are the aerodynamic coefficients of the winged seed petals, and this prediction is supported by experimental measurements of its rotational speed.
The falling rate numerical results are then compared with those obtained experimentally. Finally, with the rotational speed and the calculated falling rate, it is possible to measure the tip speed ratio of this rotor, an important design parameter for wind and hydrodynamic rotors, which defines its operating range and efficiency.