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Visualizing Transport and Mixing in Particle-based Fluid Flows

Tobias Rapp and Carsten Dachsbacher

Vision, Modeling, and Visualization 2019

Fluid phases and LCS
We visualize time-dependent transport and mixing in a multiphase fluid simulation of a fuel spray nozzle. Here, the different fluid types are illustrated together with particles close to Lagrangian coherent structures (black).

Abstract

To gain insight into large, time-dependent particle-based fluid flows, we visually analyze Lagrangian coherent structures (LCS), a robust skeleton of the underlying particle dynamics. To identify these coherent structures, we build on recent work that efficiently computes the finite-time Lyapunov exponent (FTLE) directly on particle data. We formulate the LCS definitions for particles based on robust approximations for higher-order derivatives of the FTLE. Based on these formulations, we derive a per-particle distance to the closest coherent structure. This allows us to visually analyze and explore the Lagrangian transport behavior directly on the particle data. We show that this is especially beneficial to detect and visualize flow features on different time scales. Lastly, we apply our approach to study mixing in multiphase flows by visualizing the different types of fluids and their relation to the coherent structures.

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Paper

DOI: 10.2312/vmv.20191330