The Experts below are selected from a list of 25521 Experts worldwide ranked by ideXlab platform
Detlef Lohse - One of the best experts on this subject based on the ideXlab platform.
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comparison of boundary integral and volume of fluid methods for compressible Bubble Dynamics
International Journal of Multiphase Flow, 2021Co-Authors: Youssef Saade, Detlef Lohse, Devaraj Van Der MeerAbstract:Abstract The Boundary Integral Method (BIM) has been widely applied to simulate oscillating Bubbles, for its high efficiency and accuracy. A conventional BIM assumes the fluid surrounding the Bubble to be inviscid and incompressible. Wang & Blake (J. Fluid Mech., 659, 2010, 191–224) proposed an improved model for Bubbles in a weakly compressible flow, which is referred to as CBIM. In this study, an all-Mach method (AMM) implemented in the free software program Basilisk for the simulation of compressible multiphase flows, and using a geometric Volume-of-Fluid (VoF), is employed to study and estimate the accuracy of BIM and CBIM at different Mach numbers. First, for a spherical Bubble, an extended Rayleigh-Plesset equation, CBIM and AMM give very close results when M a ≲ 0.3 . However, a deviation between these three schemes gradually becomes evident as M a increases from 0.3 to 0.6. Second, for the nonspherical deformation of a Bubble close to a wall, the results obtained from CBIM and AMM show many similarities, including the evolution of the nonspherical Bubble morphology, jet impact velocity, and impact pressure on the wall. Apart from the liquid compressibility, the gas inertia/density is found to be another factor that may affect the applicability of CBIM. In addition, we compare the CBIM and BIM results against an experiment of a spark-generated cavitation Bubble, in which the liquid compressibility is found to play a vital role. From the perspective of engineering applications, BIM can reproduce the main features of the Bubble Dynamics in the first cycle if the initial conditions are set properly. The new findings provide a reference for research of Bubble Dynamics in both fundamental and applied problems.
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modelling large scale airgun Bubble Dynamics with highly non spherical features
International Journal of Multiphase Flow, 2020Co-Authors: Devaraj Van Der Meer, Detlef Lohse, Andrea Prosperetti, Aman ZhangAbstract:Abstract A thorough understanding of the Dynamics of meter-sized airgun-Bubbles is very crucial to seabed geophysical exploration. In this study, we use the boundary integral method to investigate the highly non-spherical airgun-Bubble Dynamics and its corresponding pressure wave emission. Moreover, a model is proposed to also consider the process of air release from the airgun port, which is found to be the most crucial factor to estimate the initial peak of the pressure wave. The numerical simulations show good agreement with experiments, in terms of non-spherical Bubble shapes and pressure waves. Thereafter, the effects of the port opening time T open , airgun firing depth, heat transfer, and gravity are numerically investigated. We find that a smaller T open leads to a more violent air release that consequently causes stronger high-frequency pressure wave emissions; however, the low-frequency pressure waves are little affected. Additionally, the non-spherical Bubble Dynamics is highly dependent on the Froude number Fr. Starting from F r = 2 , as Fr increases, the jet contains lower kinetic energy, resulting in a stronger energy focusing of the Bubble collapse itself and thus a larger pressure peak during the Bubble collapse phase. For Fr ≥ 7, the spherical Bubble theory becomes an appropriate description of the airgun-Bubble. The new findings of this study may provide a reference for practical operations and designing environmentally friendly airguns in the near future.
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Shortwave infrared imaging setup to study entrained air Bubble Dynamics in a MEMS-based piezo-acoustic inkjet printhead
Experiments in Fluids, 2019Co-Authors: Arjan Fraters, Tim Segers, Hans Reinten, Herman Wijshoff, Detlef Lohse, Marc Van Den Berg, Michel VersluisAbstract:Abstract: Piezo-acoustic inkjet printing is the method of choice for high-frequency and high-precision drop-on-demand inkjet printing. However, the method has its limitations due to Bubble entrainment into the nozzle, leading to jetting instabilities. In this work, entrained air Bubbles were visualized in a micrometer scale ink channel inside a silicon chip of a MEMS-based piezo-acoustic inkjet printhead. As silicon is semi-transparent for optical imaging with shortwave infrared (SWIR) light, a highly sensitive SWIR imaging setup was developed which exploited the optical window of silicon at 1550 nm. Infrared recordings of entrained Bubbles are presented, showing rich phenomena of acoustically driven Bubble Dynamics inside the printhead. Graphic abstract: [Figure not available: see fulltext.].
Oleg Krichevsky - One of the best experts on this subject based on the ideXlab platform.
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Bubble Dynamics in double stranded dna
Physical Review Letters, 2003Co-Authors: Gregoire Altanbonnet, Oleg Krichevsky, Albert LibchaberAbstract:We report the first measurement of the Dynamics of Bubble formation in double-stranded DNA. Fluctuations of fluorescence of a synthetic DNA construct, internally tagged with a fluorophore and a quencher, are monitored by fluorescence correlation spectroscopy. The relaxation Dynamics follow a multistate relaxation kinetics, with a characteristic time scale of $50\text{ }\ensuremath{\mu}\mathrm{s}$. A simple model of Bubble Dynamics based on constant zipping-unzipping rates is proposed to account for our experimental data. The role of different secondary structures stabilizing the open Bubble is tested.
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Bubble Dynamics in double-stranded DNA.
Physical review letters, 2003Co-Authors: Grégoire Altan-bonnet, Albert Libchaber, Oleg KrichevskyAbstract:We report the first measurement of the Dynamics of Bubble formation in double-stranded DNA. Fluctuations of fluorescence of a synthetic DNA construct, internally tagged with a fluorophore and a quencher, are monitored by fluorescence correlation spectroscopy. The relaxation Dynamics follow a multistate relaxation kinetics, with a characteristic time scale of 50 microseconds. A simple model of Bubble Dynamics based on constant zipping-unzipping rates is proposed to account for our experimental data. The role of different secondary structures stabilizing the open Bubble is tested.
Eric Johnsen - One of the best experts on this subject based on the ideXlab platform.
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single Bubble Dynamics in histotripsy and high amplitude ultrasound modeling and validation
Physics in Medicine and Biology, 2020Co-Authors: Lauren Mancia, Mauro Rodriguez, Jonathan R Sukovich, Eric JohnsenAbstract:A variety of approaches have been used to model the Dynamics of a single, isolated Bubble nucleated by a microsecond length high-amplitude ultrasound pulse (e.g. a histotripsy pulse). Until recently, the lack of single-Bubble experimental radius vs. time data for Bubble Dynamics under a well-characterized driving pressure has limited model validation efforts. This study uses radius vs. time measurements of single, spherical histotripsy-nucleated Bubbles in water to quantitatively compare and validate a variety of Bubble Dynamics modeling approaches, including compressible and incompressible models as well as different thermal models. A strategy for inferring an analytic representation of histotripsy waveforms directly from experimental radius vs. time and cavitation threshold data is presented. We compare distributions of a calculated validation metric obtained for each model applied to 88 experimental data sets. There is minimal distinction (<1%) among the modeling approaches for compressibility and thermal effects considered in this study. These results suggest that our proposed strategy to infer the waveform, combined with simple models minimizing parametric uncertainty and computational resource demands accurately represent single-Bubble Dynamics in histotripsy, including at and near the maximum Bubble radius. Remaining sources of parametric and model-based uncertainty are discussed.
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single Bubble Dynamics in histotripsy and high amplitude ultrasound modeling and validation
arXiv: Fluid Dynamics, 2020Co-Authors: Lauren Mancia, Mauro Rodriguez, Jonathan R Sukovich, Eric JohnsenAbstract:A variety of approaches have been used to model the Dynamics of a single, isolated Bubble nucleated by a microsecond length high-amplitude ultrasound pulse (e.g., a histotripsy pulse). Until recently, the lack of single--Bubble experimental radius vs. time data for Bubble Dynamics under a well-characterized driving pressure has limited model validation efforts. This study uses radius vs. time measurements of single, spherical histotripsy-nucleated Bubbles in water [Wilson et al., Phys. Rev. E, 2019, 99, 043103] to quantitatively compare and validate a variety of Bubble Dynamics modeling approaches, including compressible and incompressible models as well as different thermal models. A strategy for inferring an analytic representation of histotripsy waveforms directly from experimental radius vs. time and cavitation threshold data is presented. We compare distributions of a calculated validation metric obtained for each model applied to $88$ experimental data sets. There is minimal distinction ($< 1\%$) among the modeling approaches for compressibility and thermal effects considered in this study. These results suggest that our proposed strategy to infer the waveform, combined with simple models minimizing parametric uncertainty and computational resource demands accurately represent single-Bubble Dynamics in histotripsy, including at and near the maximum Bubble radius. Remaining sources of parametric and model-based uncertainty are discussed.
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numerical modeling of Bubble Dynamics in viscoelastic media with relaxation
Physics of Fluids, 2015Co-Authors: Matthew Warnez, Eric JohnsenAbstract:Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation Bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical Bubble Dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller–Miksis equation with full thermal effects (inside and outside the Bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin–Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate Bubble Dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase Bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time.
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Bubble Dynamics in a viscoelastic medium with nonlinear elasticity
Journal of Fluid Mechanics, 2015Co-Authors: Renaud Gaudron, Matthew Warnez, Eric JohnsenAbstract:In a variety of recently developed medical procedures, Bubbles are formed directly in soft tissue and may cause damage. While cavitation in Newtonian liquids has received significant attention, Bubble Dynamics in tissue, a viscoelastic medium, remains poorly understood. To model tissue, most previous studies have focused on Maxwell-based viscoelastic fluids. However, soft tissue generally possesses an original configuration to which it relaxes after deformation. Thus, a Kelvin–Voigt-based viscoelastic model is expected to be a more appropriate representation. Furthermore, large oscillations may occur, thus violating the infinitesimal strain assumption and requiring a nonlinear/finite-strain elasticity description. In this article, we develop a theoretical framework to simulate spherical Bubble Dynamics in a viscoelastic medium with nonlinear elasticity. Following modern continuum mechanics formalism, we derive the form of the elastic forces acting on a Bubble for common strain-energy functions (e.g. neo-Hookean, Mooney–Rivlin) and incorporate them into Rayleigh–Plesset-like equations. The main effects of nonlinear elasticity are to reduce the violence of the collapse and rebound for large departures from the equilibrium radius, and increase the oscillation frequency. The present approach can readily be extended to other strain-energy functions and used to compute the stress/deformation fields in the surrounding medium.
Chao-tsung Hsiao - One of the best experts on this subject based on the ideXlab platform.
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Modeling of surface cleaning by cavitation Bubble Dynamics and collapse
Ultrasonics Sonochemistry, 2016Co-Authors: Georges L. Chahine, Jin Keun Choi, Anil Kapahi, Chao-tsung HsiaoAbstract:Surface cleaning using cavitation Bubble Dynamics is investigated numerically through modeling of Bubble Dynamics, dirt particle motion, and fluid material interaction. Three fluid Dynamics models; a potential flow model, a viscous model, and a compressible model, are used to describe the flow field generated by the Bubble all showing the strong effects Bubble explosive growth and collapse have on a dirt particle and on a layer of material to remove. Bubble deformation and reentrant jet formation are seen to be responsible for generating concentrated pressures, shear, and lift forces on the dirt particle and high impulsive loads on a layer of material to remove. Bubble explosive growth is also an important mechanism for removal of dirt particles, since strong suction forces in addition to shear are generated around the explosively growing Bubble and can exert strong forces lifting the particles from the surface to clean and sucking them toward the Bubble. To model material failure and removal, a finite element structure code is used and enables simulation of full fluid-structure interaction and investigation of the effects of various parameters. High impulsive pressures are generated during Bubble collapse due to the impact of the Bubble reentrant jet on the material surface and the subsequent collapse of the resulting toroidal Bubble. Pits and material removal develop on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress or its ultimate strain. Cleaning depends on parameters such as the relative size between the Bubble at its maximum volume and the particle size, the Bubble standoff distance from the particle and from the material wall, and the excitation pressure field driving the Bubble Dynamics. These effects are discussed in this contribution.
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spherical Bubble Dynamics in a bubbly medium using an euler lagrange model
Chemical Engineering Science, 2015Co-Authors: Georges L. Chahine, Chao-tsung HsiaoAbstract:Abstract For applications involving large Bubble volume changes such as in cavitating flows and in bubbly two-phase flows involving shock and pressure wave propagation, the Dynamics, relative motion, deformation, and interaction of Bubbles with the surrounding medium play crucial roles and require accurate modeling. We present in this paper a fundamental study of the dynamic oscillations of a “primary” Bubble in a bubbly mixture using a two-way coupled Euler–Lagrange model. It addresses a simplified spherical configuration while using the full three-dimensional code. A main objective of the study is to investigate how the Dynamics of a “primary” Bubble is affected by the presence of a surrounding bubbly medium and how it differs from its behavior in a pure liquid. This helps elucidate the physics at play for this relatively simple configuration. The model simulates the mixture as a continuum and solves the corresponding Navier Stokes equations with grids moving with the interface of the primary Bubble wall. The surrounding microBubbles are tracked in a Lagrangian fashion accounting for their volume evolution. The two-way coupling between the bubbly medium and the primary Bubble Dynamics is realized through the local density of the mixture obtained from the tracking of the microBubbles and the determination of their volumes and spatial distribution. The simulations clearly indicate that the surrounding microBubbles absorb energy emitted from the primary Bubble during its oscillations. This results in a reduction of the maximum radius and the period of oscillations of the primary Bubble as compared to the Dynamics in the pure liquid. Also, accounting for the Dynamics of the field Bubbles brings out the presence in the two-phase medium of a phase shift between density and pressure distributions. Such a shift is not captured by two-phase homogeneous medium models. These effects increase with increase in the mixture void fraction and in the initial Bubble sizes in the mixture. The numerical observations are found to be in good qualitative agreements with previously published experimental data ( Jayaprakash et al., 2011 ) investigating spark generated Bubble Dynamics in a bubbly medium.
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modelling single and tandem Bubble Dynamics between two parallel plates for biomedical applications
Journal of Fluid Mechanics, 2013Co-Authors: Chao-tsung Hsiao, Jin Keun Choi, Georges L. Chahine, Sowmitra Singh, Yurii A Ilinskii, Evgenia A Zabolotskaya, Mark F Hamilton, Georgy Sankin, Fang Yuan, Pei ZhongAbstract:Carefully timed tandem microBubbles have been shown to produce directional and targeted membrane poration of individual cells in microfluidic systems, which could be of use in ultrasound-mediated drug and gene delivery. This study aims at contributing to the understanding of the mechanisms at play in such an interaction. The Dynamics of single and tandem microBubbles between two parallel plates is studied numerically and analytically. Comparisons are then made between the numerical results and the available experimental results. Numerically, assuming a potential flow, a three-dimensional boundary element method (BEM) is used to describe complex Bubble deformations, jet formation, and Bubble splitting. Analytically, compressibility and viscous boundary layer effects along the channel walls, neglected in the BEM model, are considered while shape of the Bubble is not considered. Comparisons show that energy losses modify the Bubble Dynamics when the two approaches use identical initial conditions. The initial conditions in the boundary element method can be adjusted to recover the Bubble period and maximum Bubble volume when in an infinite medium. Using the same conditions enables the method to recover the full Dynamics of single and tandem Bubbles, including large deformations and fast re-entering jet formation. This method can be used as a design tool for future tandem-Bubble sonoporation experiments.
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simulation of surface piercing body coupled response to underwater Bubble Dynamics utilizing 3dynafs a three dimensional bem code
Computational Mechanics, 2003Co-Authors: Georges L. Chahine, Kenneth M Kalumuck, Chao-tsung HsiaoAbstract:We have developed a three-dimensional BEM based code (3DYNAFS©) to study nonlinear free surface flows. The code is being used here to study Bubble Dynamics, such as that due to an underwater explosion, beneath surface piercing bodies. Six degree-of-freedom rigid body motion of the surface piercing bodies are modeled producing a fully coupled fluid-structure interaction effect simulation. Validation of the code is presented by comparison of simulations with laboratory experimental data obtained from high speed video recordings of surface piercing bodies interacting with Bubbles generated by electric spark discharge. Two cylindrical body configurations are considered under both free floating and rigidly constrained conditions. The results of the numerical simulation show very good comparison to the experimental data in terms of Bubble shapes and periods, the time evolution of the Bubble and the induced motion of the bodies.
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Study of Tip Vortex Cavitation Inception Using Navier-Stokes Computation and Bubble Dynamics Model
Journal of Fluids Engineering, 1999Co-Authors: Chao-tsung Hsiao, Laura L. PauleyAbstract:The Rayleigh-Plesset Bubble Dynamics equation coupled with the Bubble motion equation developed by Johnson and Hsieh was applied to study the real flow effects on the prediction of cavitation inception in tip vortex flows. A three-dimensional steady-state tip vortex flow obtained from a Reynolds-Averaged Navier-Stokes computation was used as a prescribed flow field through which the Bubble was passively convected. A “window of opportunity” through which a candidate Bubble must pass in order to be drawn into the tip-vortex core and cavitate was determined for different initial Bubble sizes. It was found that Bubbles with larger initial size can be entrained into the tip-vortex core from a larger window size and also had a higher cavitation inception number.
Yuh-ming Ferng - One of the best experts on this subject based on the ideXlab platform.
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investigating effects of heating orientations on nucleate boiling heat transfer Bubble Dynamics and wall heat flux partition boiling model for pool boiling
Applied Thermal Engineering, 2019Co-Authors: T J Chuang, Y.h. Chang, Yuh-ming FerngAbstract:Abstract Studying the nucleate pool boiling is an important research in the thermal science. Therefore, the pool boiling experiments are performed in this paper to investigate the effects of heating orientations on the characteristics of boiling heat transfer and Bubble Dynamics. Based on the measured data, the boiling heat transfer capability increases as the inclined angle of heating surface is elevated. This enhanced effect is pronounced in the lower heat flux region and is insignificant in the higher heat flux region, which is also reported in the previous works. The characteristics of Bubble growth, departure, sliding, and coalescence as well as the corresponding timings can be clearly revealed in the frames taken from the high-speed videos. Based on the measurement and observation, the merged Bubble diameter and departure frequency increase with the increasing heating orientation. However, the active nucleate site density is measured to be independent of the inclined angles. The relationship of Bubble Dynamics with the wall superheat and the heating orientation can be obtained using the least-square-error regression method. With the input of these regressed correlations, the wall heat flux partitioning model can be assessed with the present measured boiling curves under various heating orientations. Good agreement reveals that the measured results and the corresponding regression equations provided herein can assist in validation of other boiling heat transfer models. This is one of main contributions from the present work in addition to providing additional data to understand the boiling characteristics of pool boiling under variable heating orientations.
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Experimental investigation on Bubble Dynamics and boiling heat transfer for saturated pool boiling and comparison data with previous works
Applied Thermal Engineering, 2019Co-Authors: Y.h. Chang, Yuh-ming FerngAbstract:Abstract This paper experimentally investigates the boiling heat transfer capability and the Bubble dynamic characteristics for the saturated pool boiling through thermocouple measurement and high-speed camera observation. The Bubble Dynamics include the Bubble departure diameter, the Bubble departure frequency, and the nucleation site density. The boiling curve for the pool boiling is also obtained. Applicability of the boiling heat transfer models in the thermal industries strongly relies on the appropriate correlations for these Bubble dynamic parameters. In this paper, the correlations for the Bubble departure diameter/departure frequency, the nucleation site density, and the boiling curve have been assessed with the present measurements. The data from the previous works are also compared to demonstrate reasonability of the present results. Using the least-square-method, the relationship of Bubble Dynamics with the wall superheat can be regressed. Comparison of the boiling curves between the measurements and predictions are also presented. The predicted boiling curve is obtained from the wall heat flux partitioning model with the input of the regressed equations for the Bubble Dynamics. The agreement reveals that the present boiling curve and Bubble Dynamics can provide the useful information for validation of CFD two-phase and boiling heat transfer models, which is one of main contributions from the present work.
