Numerical simulation of Petrea Volubilis falling seed
Creators: name:  C. MENDEZ 
name:   F. BAJAC 
name:   J. KURITA 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: FLIGHT PHYSICS
COMPUTATIONAL FLUID DYNAMICS

description: Petrea Volubilis is an evergreen vine species native to central and South America, characterized by having auto rotating seeds [1]. These seeds have an excellent capacity for speed reduction and stability, making them a great candidate for the development of parachute like devices and all similar possible applications. Speed reduction devices have multiple applications and are the subject of much research worldwide, mostly based on nature [2]. Similarly, other authors [3] have successfully analyzed the kinematics of falling maple seeds and the initial transition to a helical motion. From the experimental and computational point of view, the authors were able to conclude how Leading Edge Vortices elevate the lift of auto rotating plant seeds [4]. All mentioned works are based on the maple seed case. Computational Fluid Dynamics (CFD) is a great tool used to study the aerodynamics of the seeds [5] and its possible applications [6] of the Petrea Volubilis. By analyzing CFD solutions on a three-dimensional scanned seed, it is possible to identify key design parameters that rule this falling seed\'s behavior. For this, we perform two simulation platforms using the Open source called OpenFoam [7] and SolidWorks [8]. Both simulations will be compared with experimental measurements of the seed\'s fall and tested for different conditions to test the results\' quality and simulation time. This CFD result will be used to determine the design parameters for the parachute mechanism. The characterization of the seed was carried out. Measurements such as the average weight of several samples were conducted. Falling steady-state velocities, as well as rotational speeds, were measured at our experimental setup. Later, they were digitized using a 3D scanner with a maximum resolution of 67,000 points/in. This ensures a reliable model that represents the real seed in both size and texture. The resulting file was obtained in .stl format, so it had to be post-processed to be easily handled in the simulation tools such as SolidWorks software. Once the digital model was ready, the boundary conditions for the simulation were set. The study consisted of the external and, internal flow analysis inside a cylinder where the digital model of the seed was placed with a rotating condition. The working fluid was set to be air at standard ambient conditions. Two main boundary conditions were established: an inlet velocity to the cylinder with a vertical direction upwards and an angular velocity, corresponding to the falling and spinning velocities of the seed, respectively. The input values of both parameters were taken from measurements at the experimental setup. The goal of this simulation is to validate this simulation by comparing the calculated drag force that the seed generates at such falling and rotating conditions with the actual seed weight. Since it is assumed a steady-state condition, i.e., terminal velocity, it is expected this drag force results to be similar to the weight. In this work, we propose to study the aerodynamics of the Petrea Volubilis\'s seed fall towards the development of new applications based on nature. This work presents a novel study of this seed\'s characteristics and advantages and proposes possible alternative designs for the speed-reducing mechanism. One of the intended applications is to be used in high altitude balloon payload recovery. Scientific experiments conducted at stratospheric environments required an alternative parachute mechanism to reduce weight budget and possibly passive control in the falling trajectory. This is important since balloon style vehicles have a very restricted limit on payload weight lifting capacity. [1] Villasenor, J.L.. Checklist of the native vascular plants of Mexico Revista Mexicana de Biodiversidad 87: 559-902, 2016. [2] D. Lentink, W. B. Dickson, J. L. van Leeuwen, M. H. Dickinson, Leading-Edge Vortices Elevate Lift of Autorotating Plant Seeds, 2009, Science 12, Vol 324, pp 1438-1440. [3] Varshney, Kapil, Song Chang, and Z. Jane Wang. \"The kinematics of falling maple seeds and the initial transition to a helical motion.\" Nonlinearity 25.1 (2011): C1. [4] Lentink, David, et al. \"Leading-edge vortices elevate lift of autorotating plant seeds.\" Science 324.5933 (2009): 1438-1440. [5] J. Holden, T. Caley, M.. Turner. Maple Seed Performance as a Wind Turbine, Scitech Forum,AIAA, 2015-1304, https://doi.org/10.2514/6.2015-1304. [6] J. Gaitan-Aroca, F. Sierra, J. Castellanos, Bio-Inspired Rotor Design Characterization of a Horizontal Axis Wind Turbine, Energies, 2020, 13, 3515. [7] https://www.openfoam.com [8] https://www.solidworks.com