An experimental and numerical study on the behavior of finite-length column vortex

TL;DR

This study combines experimental PIV and numerical LES methods to analyze the complex three-dimensional behavior, instabilities, and shape evolution of finite-length vortex columns, providing insights into their dynamics influenced by various forces.

Contribution

It introduces a novel experimental setup and comprehensive analysis of vortex core dynamics, including instabilities and shape changes, in finite-length vortex columns.

Findings

Vortex core shape deforms over time due to meridional swirl and axial vorticity transport.

Long-wavelength bending instabilities with a left-handed helical structure are observed.

The study highlights the influence of inertia, Coriolis, and viscous forces on vortex dynamics.

Abstract

This paper explores experimental and numerical investigation of the spatio-temporal dynamics of a finite-length vortex column in three dimensions using Particle Image Velocimetry (PIV) and Large Eddy Simulation (LES). The research examines the combined impact of bending, buckling, and core-splitting on a finite-length vortex column. More precisely, the work centers on the fundamental motions, evolutions in flow along the axis, how the shape of the vortex core changes over time, the instability caused by the long waves on the vortex column, and the division of the vortex core. A novel prototype is developed that utilizes piston-driven inflow and produces a vortex column through the principles of flow separation and Biot-Savart induction, which is studied for predicting an ex-situ cyclonic line vortex. The present study discusses the complete three-dimensional overview of the same columnar vortex. The meridional swirl and the axial transport of vorticity deform the shape of the core cross-sections in different lengths of the column. The jump in the axial velocity at the core boundary allows for the occurrence of bending instabilities with a left-handed helical structure. These instabilities have a long wavelength, similar to the length of the vortex column, and belong to the m=+1 mode. The vortex column experiences a non-uniform curvature and torsion caused by the intricate shape of the laboratory model and varying flow speeds at different heights of the vortex column. The results offer valuable insights into the role of inertia, Coriolis, and viscous forces on the dynamics of the vortex column.