Numerical Analysis and Performance Evaluation of a Flapping Airfoil in the Wake of a Bluff Body

Abstract

This thesis investigates the vortex interactions between a flapping airfoil and an oscillating cylinder, focusing on how the upstream cylinder’s presence influences the airfoil’s thrust performance as it moves through the wake. The research examines the impact of oscillatory motion of cylinder on the thrust and side force metrics of the flapping airfoil while also assessing the effects of the flapping airfoil on the dynamics of cylinder. A series of CFD simulations were conducted using ANSYS Fluent 2023 R1, utilizing Overset meshing to enhance accuracy and avoid mesh deformation around both the airfoil and cylinder. Initial simulations established a baseline for the airfoil’s performance across various parameters. The results showed that vortices from the upstream oscillating cylinder significantly affected the airfoil’s aerodynamic performance, with increasing pitching amplitude generally enhancing thrust and side force coefficients at lower Strouhal numbers. However, higher Strouhal numbers resulted in diminishing returns, indicating potential thresholds where further increases in pitching amplitude no longer yield proportional benefits. The study also revealed change in dynamics in the VIV of the cylinder, with drag coefficients consistently rising and lift coefficients decreasing as Strouhal numbers increased. The findings also indicated that the oscillating airfoil influenced the cylinder’s dynamics through external aerodynamic forces, affecting both drag and lift and altering the cylinder’s oscillatory behavior. These insights highlight the complexity of fluid-structure interactions and offer valuable guidance for designing more efficient airfoil systems across various engineering applications, emphasizing the reciprocal nature of the flapping airfoil and the oscillating cylinder.