MODIFIED CORE-LINE TECHNIQUES FOR VORTEX IDENTIFICATION USING LIUTEX

Abstract

Vortex dynamics govern critical processes in turbulent flows, yet conventional identification methods struggle to resolve individual structures’ morphology and evo- lutionary pathways. Detecting and extracting vortex structures by objective algo- rithms may lead to a better understanding of turbulence regeneration dynamics through the automated and quantitative assessment of the structures. Although there are many vortex-identification criteria available, they pinpoint only the spatial regions belonging to vortices, with no information on the specific identity, topology, and shape of individual vortices. In this dissertation, we develop a new scheme based on Vortex axis tracking by iterative propagation (VATIP), called modified VATIP al- gorithm, for three-dimensional vortex axis-line tracking and analysis in wall-bounded turbulent flows. This new algorithm employs the Liutex magnitude R, a rigorous rotation strength metric, to guide axis-line propagation through three-dimensional velocity fields. This alternative method makes a significant improvement over some of the weaknesses of the original method, thus resulting in a better physical and accurate representation of vortex structures. Moreover, we introduce an advanced version of the predictor-corrector vortex identification method, called the modified PCM. The idea revolves around replacing pressure and vorticity variables by Liutex magnitude R and the real eigenvector ⃗r, respectively. Our approach enables enhanced isolation of the rigid rotational components of the flow field in complex geometries. This methodological advancement allows for more accurate characterization of vortex core dynamics, along with numerically inherent artifacts, which will be proven further in theory and computatio.