Advances in Turbulence Studies

Abstract

Vortex reconnection is explored in order to understand coherent structure evolution and interactions, as well as its role in fundamental turbulence phenomena such as cascade and mixing. Due to lack of measurement techniques for such topology-changing events, particularly for capturing the instantaneous 3D velocity and vorticity fields, we rely on well-resolved direct numerical simulations of the Navier-Stokes equations. The reconnection process is found to consist of a set of generic stages including bridging, threading and head-tail formation. Reconnection is incomplete as the self-induced motions of bridges and threads suggest a physical mechanism of cascade to smaller scales via successive bridging and threading: the number of stages increases with Reynolds number. These observations lead us to suggest that reconnection processes play an important role in cascade, entrainment and mixing in turbulent flows.