Vortex Identification in a Free-Surface Flow Problem Solved Using SPH

Department of Fluid Mechanics and Thermodynamics, Faculty of Mechanical Engineering, Czech Technical University in Prague, Technická 4, 160 00 Prague 6, Czechia

^* Corresponding author: petr.jancik@fs.cvut.cz

Abstract

This article focuses on vortex structure identification methods and their implementation into smoothed particle hydrodynamics (SPH) framework. The most common criteria based on the local velocity gradient tensor analysis like Q-criterion, Δ-criterion, and λ₂-criterion are introduced together with their implementation for SPH data. A two-dimensional ‘double dam break’ problem was chosen as a test case because it results in a violent transient free-surface flow with emerging and vanishing eddies of various sizes and intensities. Q-criterion and Δ-criterion results were virtually identical, whereas λ₂-criterion appeared to be the most restrictive in vortex identification, so it was the best in suppressing incorrect findings due to the numerical solution imperfection. The analysis of the problem was therefore conducted using the λ₂-criterion.