Parametric Investigations of the Induced Shear Stress by a Laser-Generated Bubble

Abstract

The present paper focuses on the simulation of the growth and collapse of a bubble in the vicinity of a wall. Both liquid and gas phases are assumed compressible, and their interaction is handled with the volume-of-fluid method. The main interest is to quantify the influence of the induced shear stress and pressure pulse in the vicinity of the wall for a variety of bubble sizes and bubble-wall distances. The results are validated against prior experimental results, such as the measurements of the bubble size, induced pressure field, and shear stress on the wall. The simulation predictions indicate that the wall in the vicinity of the bubble is subjected both to high shear stresses and large pressure pulses because of the growth and collapse of the bubble. In fact, pressure levels of 100 bar or more and shear stresses up to 25 kPa have been found at localized spots on the wall surface, at the region around the bubble. Moreover, the simulations are capable of providing additional insight to the experimental investigation, as the inherent limitations of the latter are avoided. The present work may be considered as a preliminary investigation in optimizing bubble energy and wall generation distance for ultrasound cleaning applications.

Jetting and shear stress enhancement from cavitation bubbles collapsing in a narrow gap

“…Although ignoring the boundary layers, these simulations describe very well gross features of the flow such as the shape of the bubble, direction of the jet and motion of the bubble centroid. Yet, close to the rigid boundaries, the no-slip boundary condition demands viscosity to be taken into account (Popinet & Zaleski 2002;Mohammadzadeh, Li & Ohl 2017;Koukouvinis et al 2018;Lauterborn et al 2018;Zeng et al 2018a;Lechner et al 2019). Han et al (2018) compared the bubble dynamics in a viscous liquid gap with simulations with a small set of parameters, but did not analyse the boundary layers.…”

Splitting and jetting of cavitation bubbles in thin gaps

“…To simulate the bubble dynamics and induced liquid jet, we assume the bubble as non-condensable gas following a polytropic equation of state and consider the surrounding liquid as a Tait-compressible liquid (Macdonald 1969), similar to Koukouvinis et al (2018). The nonlinear compressibility is computed as ψ = Dρ/Dp based on the equation of state, where ρ and p are the density and pressure, respectively.…”

Wall shear stress from jetting cavitation bubbles: influence of the stand-off distance and liquid viscosity

“…The problem consists of two phases (gas and liquid), where both are compressible and immiscible Newtonian fluids. As heat and mass transfer between two phases are negligible (Koukouvinis et al 2018;Zeng et al 2020), the governing equations for the flow are the equations of continuity and momentum:…”