Abstract
This study investigated the dynamics of vapor bubble growth and collapse for a laser-induced bubble. The smoothed particle hydrodynamics (SPH) method was utilized, considering the liquid and vapor phases as the van der Waals (VDW) fluid and the solid wall as a boundary. We compared our numerical results with analytical solutions of bubble density distribution and radius curve slope near a wall and the experimental bubble shape at a wall, which all obtained a fairly good agreement. After validation, nine cases with varying heating distances (L2 to L4) or liquid heights (h2 to h10) were simulated to reproduce bubbles near or at a wall. Average bubble radius, density, vapor mass, velocity, pressure, and temperature during growth and collapse were tracked. A new recognition method based on bubble density was recommended to distinguish the three substages of bubble growth: (a) inertia-controlled, (b) transition, and (c) thermally controlled. A new precollapse substage (Stage (d)) was revealed between the three growth stages and collapse stage (Stage (e)). These five stages were explained from the out-sync between the bubble radius change rate and vapor mass change rate. Further discussions focused on the occurrence of secondary bubbles, shockwave impact on the wall, system entropy change, and energy conversion. The main differences between bubbles near and at the wall were finally concluded.
Highlights
Vapor bubbles have recently drawn intensive attention in many research fields [1], such as micro- or nanomanipulation [2], the heat transfer of two-phase heat exchangers [3,4], and medical vapor bubble cancer treatment [5,6,7]
Many studies have focused on vapor bubble dynamics, both experimentally or numerically
Gonzalez-Avila et al studied the dynamics of bubbles in a highly variable liquid gap [13], and Sun and Zachary et al concluded that thermal effects played an important role in the entire growth and collapse of bubbles in microchannels [14,15]
Summary
Vapor bubbles have recently drawn intensive attention in many research fields [1], such as micro- or nanomanipulation [2], the heat transfer of two-phase heat exchangers [3,4], and medical vapor bubble cancer treatment [5,6,7]. Numerical simulations could help to better understand bubble dynamics and provide more details about bubble density, velocity, and heat fluctuations, including volume of fraction (VOF), the lattice Boltzmann method (LBM), and smoothed particle hydrodynamics (SPH). Wang built a model to calculate vapor bubble growth and collapse in microgravity but used a lot of empirical parameters and formulas for determining the bubble interface [25]. These works could not provide thorough information from bubble growth to bubble collapse, as bubble growth would affect the subsequent collapse.
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