Cavitation Inception on Microparticles: A Self-Propelled Particle Accelerator

Abstract

Corrugated, hydrophilic particles with diameters between 30 and 150 m are found to cause cavitation inception at their surfaces when they are exposed to a short, intensive tensile stress wave. The growing cavity accelerates the particle into translatory motion until the tensile stress decreases, and subsequently the particle separates from the cavity. The cavity growth and particle detachment are modeled by considering the momentum of the particle and the displaced liquid. The analysis suggests that all particles which cause cavitation are accelerated into translatory motion, and separate from the cavities they themselves nucleate. Thus, in the research of cavitation nuclei the link is established between developed cavitation bubbles and their origin.

Reflections on cavitation nuclei in water

“…in which the tensile strength exceeded 10 bar in only a single case. The measurements of Marschall et al 19 and Arora et al, 20 carried out with artificial, almost perfectly spherical, smooth 30 m particles from the same batch, are illustrating. When seeding these particles into tap water filtered of natural particles larger than 1 m, Marschall et al obtained a tensile strength of ϳ0.9 bar in a nozzle flow of filtered tap water.…”

“…2. In later experiments by Arora et al, 20 particles from the same batches were seeded into filtered and degassed water ͑Milli-Q water͒ and exposed to the transient tensile stress pulse from a lithotripter of peak amplitude 70 bar and pulse duration Ͻ10 s. Here cavitation inception could not be achieved. This supports the assumption that in the nozzle flow used by Marschall et al, the less clean water and the much longer time of exposure to tensile stress made it possible for the nano-voids to merge, thus causing a relatively low tensile strength.…”

Slurry Erosion – Design of Test Devices

“…Thus, the numbers of factors influencing slurry erosion is very big and the degradation of materials is a synergic effect of all mentioned factors. The dependence of erosion rate on impact angle [13] Impact velocity and the size of solid particle has an effect on the kinetic impact energy of a single particle. With increasing impact velocity and particle size increases erosion rate.…”

“…If velocity increases above 6-9 m/s, high-velocity erosion is formed, while below this velocity, slurry erosion is called low-velocity erosion [3]. In case of presence of sub-micron particles (30 -150 µm in diameter) in a liquid flowing with velocity above 10 m/s, a sub-sonic erosion develops [13]. This type of erosion consists in inception of cavitation bubbles at particles surfaces [13].…”

“…In case of presence of sub-micron particles (30 -150 µm in diameter) in a liquid flowing with velocity above 10 m/s, a sub-sonic erosion develops [13]. This type of erosion consists in inception of cavitation bubbles at particles surfaces [13].…”