Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Computational fluid-dynamics modeling of parafoils
Submission Author:
João Pedro Leal Vieira , DF
Co-Authors:
João Pedro Leal Vieira, Manuel Barcelos Júnior
Presenter: João Pedro Leal Vieira
doi://10.26678/ABCM.COBEM2021.COB2021-1590
Abstract
The study of the aerodynamics of ram-air parachutes, or parafoils, has historically had an empirical basis from analysis made in wind tunnels. Numerical computational approaches are an alternative with greater accessibility and a reasonable assessment of the internal and external flow. Therefore, tests on a conventional closed airfoil, with well-defined aerodynamic coefficient values, have been made to validate a mesh and a turbulence model for a given geometric characteristics, more precisely the thickness, found in the Ascender airfoil, which is a reference model in this research. The membrane structure was considered rigid at its geometric position of optimum performance. The fluid dynamics numerical simulations run in a two-dimensional form, with a Reynolds Number of 300,000 in a steady-conditions glide, using the finite-volume discretization method of the RANS (Reynolds-Averaged Navier-Stokes) equations, applied by the software ANSYS Fluent. It is possible to identify performance drops in aerodynamic efficiency and a decrease in the stall angle, both associated with the air recirculation bubble generated by the opening in the leading edge through previous studies. This work aims to compare and analyze empirically referenced results achieved by the inner-out pressure differential of the Ascender parafoil with results obtained numerically. Therefore, verifying the usability of computational modeling for lower cost analysis before tests in a wind tunnel. Besides, the simulations performed to evaluate the lift coefficient's decay compared to the closed airfoil, as predicted by the theory. We found solutions for three different Ascender airfoil geometric models, with closed (rounded and straight) and opened leading edges, making it possible to visualize the influence of internal pressure on aerodynamic parameters. For the first two geometry models, previous results obtained from a panel method approach permitted an evaluation of its validity in the presented case. Finally, the results demonstrate reasonable accuracy with the proposed reference, considering the instability of aerodynamic characteristics in an open-airfoil.
Keywords
Parafoil, Computational fluid dynamics (CFD), Aerodynamics, Internal Pressure, pressure coefficient
