Granular Flow, Collisional Cooling and Charged Grains

TL;DR

This paper analyzes the non-Newtonian behavior of granular flow in a vertical pipe, focusing on velocity evolution, collisional cooling, and effects of electric charge on flow dynamics.

Contribution

It introduces a detailed analysis of how collisional cooling and electric charge influence granular flow in a vertical pipe, including velocity dependence and steady state behavior.

Findings

Steady state velocity follows a power law with pipe width (exponent 3/4 to 3/2).

Flow accelerates with more efficient collisional cooling at low densities.

Electric charge and solid fraction significantly affect collisional cooling and flow characteristics.

Abstract

The non-Newtonian character of granular flow in a vertical pipe is analyzed. The time evolution of the flow velocity and the velocity fluctuations (or granular temperature) is derived. The steady state velocity has a power law dependence on the pipe width with an exponent between 3/4 and 3/2. The flow becomes faster the more efficient the collisional cooling is, provided the density remains low enough. The dependence of collisional cooling on the solid fraction, the restitution coefficient and a possible electric charge of all grains is discussed in detail.