Onset of cavity deformation upon subsonic motion of a projectile in a fluid complex plasma

TL;DR

This paper investigates how a cavity around a projectile in a complex plasma deforms at subsonic speeds, revealing that dust cloud pressure can become negative due to friction, leading to cavity deformation and enabling pressure estimation.

Contribution

It introduces a model using Navier-Stokes equations to describe cavity deformation in complex plasmas, accounting for dust-neutral friction effects.

Findings

Negative dust cloud pressure can occur behind the projectile due to friction.

Threshold velocity for cavity deformation decreases with larger cavity size.

Measuring this velocity allows estimation of the dust cloud's static pressure.

Abstract

We study deformation of a cavity around a large projectile moving with subsonic velocity in the cloud of small dust particles. To solve this problem, we employ the Navier--Stokes equation for a compressible fluid with due regard for friction between dust particles and atoms of neutral gas. The solutions shows that due to friction, the pressure of dust cloud at the boundary of the cavity behind the projectile can become negative, which entails formation of a microscopic void free from dust particles -- the cavity deformation. Corresponding threshold velocity is calculated, which is found to decrease with increasing cavity size. Measurement of such velocity makes it possible to estimate the static pressure inside the dust cloud.