Choosing Hydrodynamic fields

TL;DR

This paper discusses criteria for selecting hydrodynamic fields in continuum mechanics, focusing on granular and multi-component fluids, and evaluates the relevance of temperature and velocity fields for accurate large-scale descriptions.

Contribution

It provides a detailed analysis of how to choose appropriate hydrodynamic fields in complex fluid systems, including granular and multi-component fluids.

Findings

Temperature is justified as a hydrodynamic field in granular fluids.

Single versus multiple species temperatures and velocities are compared.

Guidelines for selecting hydrodynamic fields in multi-component systems.

Abstract

Continuum mechanics (e.g., hydrodynamics, elasticity theory) is based on the assumption that a small set of fields provides a closed description on large space and time scales. Conditions governing the choice for these fields are discussed in the context of granular fluids and multi-component fluids. In the first case, the relevance of temperature or energy as a hydrodynamic field is justified. For mixtures, the use of a total temperature and single flow velocity is compared with the use of multiple species temperatures and velocities.