Abstract
We study systematically the cavitation-induced wall shear stress on rigid boundaries as a function of liquid viscosity
$\mu$
and stand-off distance
$\gamma$
using axisymmetric volume of fluid (VoF) simulations. Here,
$\gamma =d/R_{max}$
is defined with the initial distance of bubble centre from the wall
$d$
and the bubble equivalent radius at its maximum expansion
$R_{max}$
. The simulations predict accurately the overall bubble dynamics and the time-dependent liquid film thickness between the bubble and the wall prior to the collapse. The spatial and temporal wall shear stress is discussed in detail as a function of
$\gamma$
and the inverse Reynolds number
$1/Re$
. The amplitude of the wall shear stress is investigated over a large parameter space of viscosity and stand-off distance. The inward stress is caused by the shrinking bubble and its maximum value
$\tau _{mn}$
follows
$\tau _{mn} Re^{0.35}=-70\gamma +110$
(kPa) for
$0.5<\gamma <1.4$
. The expanding bubble and jet spreading on the boundary produce an outward-directed stress. The maximum outward stress is generated shortly after impact of the jet during the early spreading. We find two scaling laws for the maximum outward stress
$\tau _{mp}$
with
$\tau _{mp} \sim \mu ^{0.2} h_{jet}^{-0.3} U_{jet}^{1.5}$
for
$0.5\leq \gamma \leq 1.1$
and
$\tau _{mp} \sim \mu ^{-0.25} h_{jet}^{-1.5} U_{jet}^{1.5}$
for
$\gamma \geq 1.1$
, where
$U_{jet}$
is the jet impact velocity and
$h_{jet}$
is the distance between lower bubble interface and wall prior to impact.
Funder
Deutsche Forschungsgemeinschaft
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
52 articles.
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