Partial Optimal Transport for a Constant-Volume Lagrangian Mesh with Free Boundaries

TL;DR

This paper presents a novel Lagrangian mesh method based on partial optimal transport that accurately controls volume and tracks complex interface evolutions with free boundaries in various simulations.

Contribution

It extends optimal transport-based mesh representations to handle free boundaries and arbitrary topologies, enabling precise volume control and interface tracking.

Findings

Successfully models objects with free boundaries and topology changes.

Accurately controls volume in dynamic simulations.

Handles complex interface interactions and collisions.

Abstract

This article introduces a representation of dynamic meshes, adapted to some numerical simulations that require controlling the volume of objects with free boundaries, such as incompressible fluid simulation, some astrophysical simulations at cosmological scale, and shape/topology optimization. The algorithm decomposes the simulated object into a set of convex cells called a Laguerre diagram, parameterized by the position of $N$ points in 3D and $N$ additional parameters that control the volumes of the cells. These parameters are found as the (unique) solution of a convex optimization problem -- semi-discrete Monge-Amp\`ere equation -- stemming from optimal transport theory. In this article, this setting is extended to objects with free boundaries and arbitrary topology, evolving in a domain of arbitrary shape, by solving a partial optimal transport problem. The resulting Lagrangian scheme makes it possible to accurately control the volume of the object, while precisely tracking interfaces, interactions, collisions, and topology changes.