Aircraft Design and Systems Group (AERO), Department of Automotive and Aeronautical Engineering, Hamburg University of Applied Sciences
Erscheinungsjahr:
2019
Medientyp:
Text
Schlagworte:
Aerodynamik
Ahorn
Auftrieb
Strömungsabriss
Aerodynamisches Profil
Anstellwinkel
Freier Fall
Bergahorn
Samen
Evolutionsbiologie
Aerodynamics
Maple
Lift (Aerodynamics)
Stalling (Aerodynamics)
Aerofoils
Angle of attack (Aerodynamics)
Acer pseudoplatanus
Seeds
Evolution (Biology)
Blade Element Momentum Theory
BEMT
free fall
post-stall
autorotation
620: Ingenieurwissenschaften
ddc:620
Beschreibung:
Purpose - The paper presents a theoretical framework that describes the aerodynamics of a falling maple (Acer pseudoplatanus) seed. --- Methodology - A semi-empirical method is developed that provides a ratio stating how much longer a seed falls in air compared to freefall. The generated lift is calculated by evaluating the integral of two-dimensional airfoil elements using a preliminary falling speed. This allows for the calculation of the definitive falling speed using Blade Element Momentum Theory (BEMT); hereafter, the fall duration in air and in freefall are obtained. Furthermore, the input-variables of the calculation of lift are transformed to require only the length and width of the maple seed. Lastly, the method is applied to two calculation examples as a means of validation. --- Findings - The two example calculations gave percentual errors of 5.5% and 3.7% for the falling speed when compared to measured values. The averaged result is that a maple seed falls 9.9 times longer in air when released from 20 m; however, this result is highly dependent on geometrical parameters which can be accounted for using the constructed method. --- Research limitations - Firstly, the coefficient of lift is unknown for the shape of a maple seed. Secondly, the approximated transient state is yet to be verified by measurement. --- Originality / Value - The added value of this report lies in the reduction of simplifications compared to BEMT approaches. In this way a large amount of accuracy is achieved due to the inclusion of many geometrical parameters, even though simplicity is maintained. This has been accomplished through constructing a simple three-step method that is fundamental and essentially non-iterative.