Definition of vortex boundary using stagnation pressure

TL;DR

This paper introduces a new, physically consistent method for identifying vortex boundaries in turbulent flows using stagnation pressure surfaces, enhancing visualization and analysis of complex fluid dynamics.

Contribution

It presents a novel, Galilean invariant approach based on stagnation pressure that accurately defines vortex boundaries and centers, improving upon existing methods.

Findings

The method effectively visualizes complex turbulent flows.

It provides a robust, physically grounded vortex boundary definition.

The approach ensures circulation conservation in the inviscid limit.

Abstract

A novel method is proposed to identify vortex boundary and center of rotation based on tubular surfaces of constant stagnation pressure and minimum of the stagnation pressure gradient. The method is derived from Crocco's theorem, which ensures that the gradient of stagnation pressure is orthogonal to both the velocity and vorticity vectors. The method is Galilean invariant, requires little processing and is robust. It enables visualization of complex turbulent flows and provides a physically consistent definition of vortex boundaries for quantitative analyses. This vortex boundary is a material surface that is representative of the kinematics of the flow by construction, constitutes a vortex tube, ensures conservation of circulation in the inviscid limit and provides a unique relation to the conservation of momentum equations and vortex loads.