Significance of the strain-dominated region around a vortex on induced aerodynamic loads

TL;DR

This paper reveals that strain-dominated regions surrounding vortices significantly influence aerodynamic loads, challenging the traditional focus solely on vortex cores in flow analysis.

Contribution

It introduces the importance of strain-dominated regions around vortices in determining aerodynamic loads, expanding the understanding of vortex-induced effects.

Findings

Strain-dominated regions are dynamically important around vortices.

Strain regions can dictate aerodynamic loads during dynamic stall.

Current vortex models overlook the influence of strain-dominated areas.

Abstract

The ability of vortices to induce aerodynamic loads on proximal surfaces plays a significant role in a wide variety of flows. However, most studies of vortex-induced effects primarily focus on analyzing the influence of the rotation-dominated cores of vortices. In this work, we show that not only are vortices in viscous flows surrounded by strain-dominated regions, but that these regions are dynamically important and can sometimes even dictate the induced aerodynamic loads. We demonstrate this for a pitching airfoil, which exhibits dynamic stall and generates several force-inducing vortices. Using a data-driven force partitioning method, we quantify the influence of vortices as well as vortex-associated strain to show that our current understanding of vortex-dominated phenomena, such as dynamic stall, is incomplete without considering the substantial effect of strain-dominated regions that are associated with vortices.