Assessment of Energy Transfer of Airfoil Wakes and Vortex Shedding with a Bispectral Network Model

Abstract

The wakes of airfoils include strong vortex shedding and compact tip vortices that undergo significant changes as they convect, break down, and dissipate downstream. One of the primary causes is turbulence and triadic interactions of scales. Interactions of triples of wavenumber or frequency scales, triads, are the fundamental mechanisms of energy transfer that control the evolution of the airfoil wake from strong vortex shedding to final dissipation. Building on previous work, triads, interactions, and energy transfer are investigated using bispectral analysis to create a network model of the wake of an airfoil at three different Reynolds numbers. Reynolds numbers are selected to exhibit laminar, weak, and strong turbulent behavior. Largeeddy simulations with the curvilinear immersed boundary method are undertaken over a three-dimensional rotor blade with a variable airfoil cross-section. Instantaneous velocity snapshots and the scale-specific energy transfer method are used to quantify the bispectra and map the triads to adjacency matrices. Two directed graph networks are constructed to map the complete triad. Reynolds number has a strong impact on the number of significant triads and dominant scales. While vortex shedding interactions are strong in all cases, high turbulence networks are highly connected with many important nodes compared to the laminar case..

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AIAA Science and Technology Forum and Exposition AIAA Scitech Forum 2025

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