Coupled Modal-Nonmodal Interactions Due to Periodic, Infinite Train of Convecting Vortices (TCV)

TL;DR

This paper investigates how a train of convecting vortices causes strong modal and non-modal interactions, leading to significant disturbance growth and potentially explaining severe turbulence encounters.

Contribution

It introduces a computational analysis of vortex train-induced interactions, revealing a novel mechanism for turbulence transition involving combined modal and non-modal effects.

Findings

Strong disturbance growth due to vortex train excitation

Interaction of modal and non-modal components identified

Potential explanation for severe turbulence encounters

Abstract

Events during transition to turbulence either follow modal or non-modal routes, or combinations of the two. Here, we report a computational investigation of strong freestream excitation caused by a train of convecting vortices. For this TCV excitation, we show a strong interaction of modal and non-modal components causing a spectacular growth of disturbances. We propose this as the mechanism for the severe encounters due to convective vortical disturbances on the underlying shear layer.