On the Structure and Performance of Low Aspect Ratio Foil with Tubercle

  • 何 溫庭

Student thesis: Master's Thesis

Abstract

In this study experiments were conducted to investigate the effects of leading -edge tubercles on the flow structure and performance of foil surfaces Previous studies have discussed the 3D flipper and 2D rectangular foil designs of leading-edge tubercles However most of them have focused on the improvement of foil performance and not on how leading-edge tubercles alter flow structures to enhance airfoil performance Therefore this study adopted the NACA0012 to design three types of leading-edge tubercles with distinct amplitudes The developed tubercles were tested in a cavitation tank to assess the performance of the foil Subsequently particle tracking velocimetry and ink visualization methods were used to investigate the changes in the flow structure and performance of foils with the designed tubercles as well as the effects of a side wall on the tubercles According to the performance test results the foil lift coefficient decreased substantially and the drag improved significantly Specifically the performance of the NACA0012L with the largest amplitude improved considerably A comparison of the visualization results of the foils with and without tubercles revealed that the vortex generated in the tubercle trough reduced the surface-attached flow thereby decreasing the lift force However the vortex could delay the separation of the boundary layer increasing the drag and maintaining the lift force at a level that influences the stalling angle of attack Moreover it could attract a portion of the separated flow in the post-stall region and reattach it to the surface These characteristics can improve the lift force in the post-stall region
Date of Award2015 Aug 26
Original languageEnglish
SupervisorJeng-Horng Chen (Supervisor)

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