Date of Award

Spring 5-7-2024

Embargo Period

5-8-2024

Access Type

Thesis - Open Access

Degree Name

Master of Science in Aerospace Engineering

Department

Aerospace Engineering

Committee Chair

Ebenezer Gnanamanickam

First Committee Member

Ebenezer Gnanamanickam

Second Committee Member

Richard Prazenica

Third Committee Member

Anastasios S. Lyrintzis

Abstract

Bio-inspired winglets were studied with the goal of better understanding the structure of the wingtip vortices they generate. Measurements of the tip vortex were previously carried out using stereoscopic particle image velocimetry (sPIV). The bio-inspired winglet was tested on a rectangular NACA 0012 wing section at a 5-degree angle of attack and at a chord Reynolds number of 900,000. Velocity field measurements were recorded at 0.7 and 2 chord lengths aft of the wing’s trailing edge. Compared to the wing with no attachment and a traditional blended winglet, the bio-inspired winglet’s vortex exhibited significantly less intense flow field properties. These properties include the streamwise velocity deficit within the vortex core, the tangential velocity levels surrounding the core and the vorticity within the core. Pressure field reconstruction from PIV data also revealed that the vortex core corresponding to the bio-inspired winglet had a much smaller pressure drop than the vortices generated by the other geometries. The bio-inspired winglet achieved these low intensity flow field properties through vortex spreading. Multiple pockets of vorticity and split vortices could be observed in the wake of the bio-inspired winglet. While the intensity of the bio-inspired winglet’s vortex was much lower, the net in-plane effects were still comparable to those of the baseline wing and winglet. This was made evident by assessing and comparing the total streamwise momentum, crossflow momentum and circulation within the interrogation planes. This effective vortex spreading resulted in a low intensity but produced a vortex that was several times larger than those produced by the other geometries. Lastly, the vortex of the bio-inspired winglet appeared to restructure itself in the downstream plane. The structure and shape of the vortex went from being incoherent and irregular to one comparable to a traditional vortex. Likewise, the number of vorticity pockets and split vortices decreased, likely due to interaction between them and their diffusion.

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