Extra mass flux in fluid mechanics

TL;DR

This paper investigates the conditions under which extra mass flux can exist in dissipative fluid models, emphasizing the role of Galilean invariance and conservation laws in such scenarios.

Contribution

It clarifies the conditions for the existence of extra mass flux in non-relativistic fluids and provides an example of weakly non-local hydrodynamics where conservation laws hold despite differing mass flux.

Findings

Conservation of mass, momentum, angular momentum, and booster can occur with or without total mass flux equaling momentum density.

Galilean invariance constrains the relationship between mass flux and other conserved quantities.

An example of weakly non-local hydrodynamics demonstrates alternative conservation mechanisms.

Abstract

The conditions of existence of extra mass flux in single component dissipative non-relativistic fluids are clarified. By considering Galilean invariance we show that if total mass flux is equal to total momentum density, then mass, momentum, angular momentum and booster (center-of-mass) are conserved. However, these conservation laws may be fulfilled also by other means. We show an example of weakly non-local hydrodynamics where the conservation laws are satisfied as well although the total mass flux is different from momentum density.