EPTT 2020

12th Spring School on Transition and Turbulence

EMPIRICAL AERODYNAMICS OF BIO-INSPIRED WINGS

Submission Author: Guilherme Pimentel , SP
Co-Authors: Guilherme Pimentel , Heidi Korzenowski
Presenter: Guilherme Pimentel

doi://10.26678/ABCM.EPTT2020.EPT20-0023

 

Abstract

Flow control devices have been widely studied over the years. The motivation for this study involves a potential gain in hydrodynamics and aerodynamics performance in engineering design such as wings, control surfaces, propellers, turbines, automotive airfoils, etc. The wavy leading edge has been investigated as a low Reynolds number flow control mechanism that performs better in the drag reduction caused by the delay in the detachment of the boundary layer, increasing the stall angle and consequently increasing the maximum lift coefficient when compared with smooth leading edges. In this sense, it is necessary to analyze the phenomenology of bio-inspired wings aerodynamics, performing aerodynamic forces measurements and flow visualizations in wind tunnel. The advance in the laminar-turbulent transition slows the flow separation condition, then increasing the maximum lift coefficient (Cl), decreasing the length of runway required for takeoff and approximation. This work aims to present to the scientific community an experimental aerodynamic analysis on the biomimetization of three-dimensional wings, whose analysis is part of the Author's Undergraduate Thesis. In this work, the aerodynamic behavior on wings with wavy leading-edge, biomimetized from the humpback whale fins, will be presented. Forces measurements were performed for a better understanding of the phenomenology involved. To investigate the effects of the wavy leading-edge, two sets of three 3D model wings were prototyped. Each set consists in a smooth leading-edge and two wavy leading-edge models (X- γ- λ), where “X” represents the initials of the airfoil in use (“N” for NACA 2412 and “C” for Clark Y) with different wavelength (γ) and amplitude (λ), both defined by a percentage of a constant chord (c). Forces measurements indicates that the NACA 2412 airfoil responded positively to biomimetization. The best configuration that showed a better increase in stall angle, lift increase, and a better drag decrease was N6γ22λ. There is also a performance improvement in the N3γ11λ configuration. Therefore, it is evident in these experiments that the biomimetization benefited the performance related to the delay of the detachment of the boundary layer, increasing the stall angle and maximum lift coefficient. However, the Clark Y airfoil did not respond as expected. The drag values were higher and lift values were lower compared to its smooth model. However, the stall of the models always decreased smoothly, without an abrupt drop of lift. This observation shows what has already been observed in Miklosovic's experiments, where it is said that the effect of the wavy leading-edge depends on the geometric shape of the wing and the turbulence regime in which it is immersed.

Keywords

Biomimicry, Aerodynamics, Wavy Leading Edge, airfoils

 

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