Simulation of granular jet: Is granular flow really a "perfect fluid?"

TL;DR

This study uses three-dimensional simulations to investigate whether granular flows behave like perfect fluids, revealing that their viscosity remains finite and differs from the idealized behavior of quark-gluon plasma.

Contribution

The paper demonstrates through simulations that granular jets do not exhibit perfect fluid behavior, challenging previous assumptions based on experimental similarities.

Findings

Small shear stress is reproduced in simulations.

Granular flow viscosity is finite and aligns with kinetic theory.

Granular jets are not true perfect fluids.

Abstract

We perform three-dimensional simulations of a granular jet impact for both frictional and frictionless grains. Small shear stress observed in the experiment[X. Cheng et al., Phys. Rev. Lett. 99, 188001 (2007) ] is reproduced through our simulation. However, the fluid state after the impact is far from a perfect fluid, and thus, similarity between granular jets and quark gluon plasma is superficial, because the observed viscosity is finite and its value is consistent with the prediction of the kinetic theory.