scholarly journals Computational analysis of single rising bubbles influenced by soluble surfactant

2018 ◽  
Vol 856 ◽  
pp. 709-763 ◽  
Author(s):  
Chiara Pesci ◽  
Andre Weiner ◽  
Holger Marschall ◽  
Dieter Bothe
Keyword(s):  
Bubble Dynamics ◽  
Solution Procedure ◽  
Bubble Surface ◽  
Fluid Interfaces ◽  
Arbitrary Lagrangian Eulerian ◽  
Deformable Interface ◽  
Mesh Resolution ◽  
Surfactant Transport ◽  
Physical Phenomena ◽  
Soluble Surfactant

This paper presents novel insights into the influence of soluble surfactants on bubble flows obtained by direct numerical simulation (DNS). Surfactants are amphiphilic compounds which accumulate at fluid interfaces and significantly modify the respective interfacial properties, influencing also the overall dynamics of the flow. With the aid of DNS, local quantities like the surfactant distribution on the bubble surface can be accessed for a better understanding of the physical phenomena occurring close to the interface. The core part of the physical model consists of the description of the surfactant transport in the bulk and on the deformable interface. The solution procedure is based on an arbitrary Lagrangian–Eulerian (ALE) interface-tracking method. The existing methodology was enhanced to describe a wider range of physical phenomena. A subgrid-scale (SGS) model is employed in the cases where a fully resolved DNS for the species transport is not feasible due to high mesh resolution requirements and, therefore, high computational costs. After an exhaustive validation of the latest numerical developments, the DNS of single rising bubbles in contaminated solutions is compared to experimental results. The full velocity transients of the rising bubbles, especially the contaminated ones, are correctly reproduced by the DNS. The simulation results are then studied to gain a better understanding of the local bubble dynamics under the effect of soluble surfactant. One of the main insights is that the quasi-steady state of the rise velocity is reached without ad- and desorption being necessarily in equilibrium.

Detailed Investigation of Detached-Eddy Simulation for the Flow Past a Circular Cylinder at Re=3900

2012 ◽  
Vol 232 ◽  
pp. 471-476 ◽  
Author(s):  
Rui Zhao ◽  
Chao Yan
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Flow Structures ◽  
Detached Eddy Simulation ◽  
Eddy Simulation ◽  
Flow Past ◽  
Large Eddy ◽  
Mesh Resolution ◽  
Physical Phenomena

The flow past a circular cylinder at a subcritical Reynolds number 3900 was simulated by the method of detached-eddy simulation (DES). The objective of this present work is not to investigate the physical phenomena of the flow but to study modeling as well as numerical aspects which influence the quality of DES solutions in detail. Firstly, four typical spanwise lengths are chosen and the results are systematically compared. The trend of DES results along the span increment is different from previous large-eddy simulation (LES) investigation. A wider spanwise length does not necessary improve the results. Then, the influence of mesh resolution is studied and found that both too coarse and over refined grids will deteriorate the performance of DES. Finally, different orders of numerical schemes are applied in the inviscid fluxes and the viscous terms. The discrepancies among different schemes are found tiny. However, the instantaneous flow structures produced by 5th order WENO with 4th order central differencing scheme are more abundant than the others. That is, for the time-averaged quantities, the second-order accurate schemes are effective enough, whereas the higher-order accurate methods are needed to resolve the transient characteristics of the flow.

scholarly journals Bubble Dynamics in Soft and Biological Matter

2019 ◽  
Vol 51 (1) ◽  
pp. 331-355 ◽  
Author(s):  
Benjamin Dollet ◽  
Philippe Marmottant ◽  
Valeria Garbin
Keyword(s):  
Viscoelastic Medium ◽  
Bubble Dynamics ◽  
Nonlinear Behavior ◽  
Bubble Surface ◽  
Solid Particles ◽  
Advanced Materials ◽  
Viscoelastic Layer ◽  
Future Research ◽  
Oscillatory Dynamics ◽  
Biological Matter

Bubbles are present in a large variety of emerging applications, from advanced materials to biology and medicine, as either laser-generated or acoustically driven bubbles. In these applications, the bubbles undergo oscillatory dynamics and collapse inside—or near—soft and biological materials. The presence of a soft, viscoelastic medium strongly affects the bubble dynamics, both its linear resonance properties and its nonlinear behavior. Surfactant molecules or solid particles adsorbed on a bubble surface can also modify the bubble dynamics through the rheological properties of the interfacial layer. Furthermore, the interaction of bubbles with biological cells and tissues is highly dependent on the mechanical properties of these soft deformable media. This review covers recent developments in bubble dynamics in soft and biological matter for different confinement conditions: bubbles in a viscoelastic medium, coated by a viscoelastic layer, or in the vicinity of soft confinement or objects. The review surveys current work in the field and illustrates open questions for future research.

Numerical Simulations of Dynamics and Heat Transfer Associated With a Single Bubble in the Presence of Noncondensables

2007 ◽  
Author(s):  
Jinfeng Wu ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Bubble Dynamics ◽  
Numerical Procedure ◽  
Saturation Temperature ◽  
Bubble Surface ◽  
Moving Mesh Method ◽  
Bubble Liquid ◽  
Noncondensable Gas ◽  
Noncondensable Gases ◽  
Level Set Function

Under subcooled boiling conditions, the liquid may contain dissolved noncondensabe gases. During phase change at the bubble-liquid interface, noncondensable gases will be injected into the bubble along with vapor. Due to heat transfer into sub-cooled liquid, vapor will condense in the upper regions of the bubble and the bubble interface is impermeable to noncondensables. As a result, noncondensabe gases will accumulate at the top of bubbles. This existing gradient of noncondensable concentration inside bubble determines the saturation temperature gradient around the bubble surface. The nonuniform saturation temperature may cause a difference in surface tension which would give rise to thermocapillary convection in the vicinity of the interface. So far, this description is merely a hypothesis. It is felt that much inspection is in vital demand to clarify the uncertainty as to the role of noncondensables throughout this process. In this study, air is taken as noncondensable gas, and the aim is to investigate the effects of noncondensable air on heat transfer and bubble dynamics. The results from a numerical procedure coupling level set function with moving mesh method show the evidence of effects of noncondensable air imposed on heat transfer and the induced flow pattern is presented as well.

Experimental and Computational Analysis of Fluid Interfaces Influenced by Soluble Surfactant

2017 ◽  
pp. 395-444
Author(s):  
Chiara Pesci ◽  
Holger Marschall ◽  
Talmira Kairaliyeva ◽  
Vamseekrishna Ulaganathan ◽  
Reinhard Miller ◽  
...  
Keyword(s):  
Computational Analysis ◽  
Fluid Interfaces ◽  
Soluble Surfactant

Visualization of Micro-Scale Bubble Dynamics in Pure Liquids and Aqueous Surfactant Solutions

Volume 4 ◽  
2004 ◽  
Author(s):  
S. Sethu Raghavan ◽  
Raj M. Manglik
Keyword(s):  
Bubble Dynamics ◽  
Bubble Diameter ◽  
Dynamic Surface Tension ◽  
Bubble Surface ◽  
Dimethyl Formamide ◽  
Time Interval ◽  
Dynamic Surface ◽  
Micro Scale ◽  
Surfactant Solutions ◽  
Air Interface

Growth and departure of a single adiabatic bubble in pure liquids and aqueous surfactant solutions is visualized. High-resolution photographic records are obtained that characterize the micro-scale bubble dynamics (shape, size, and post-departure translation), the mean bubble diameter at different time periods of its growth and departure, and the bubble surface age (the time interval from the newly formed interface to the attainment of departure diameter). This pre- and post-departure dynamics of air bubbles is visualized in water, N, N dimethyl-formamide (DMF), and ethyl alcohol (all pure liquids), and aqueous surfactant solutions of SDS (1250 wppm, 2500 wppm, and 5000 wppm), CTAB (200 wppm), and Triton X-305 (1000 wppm). The evolution of different bubble shapes, sizes, and departure frequencies is presented to highlight the effects of surface-active forces. In the case of surfactant solutions, the dynamic effects of the molecular-scale adsorption-desorption dynamics of the additive at the liquid-air interface that manifests in the dynamic surface tension is also delineated.

scholarly journals Spreading of Micrometer-Sized Droplets under the Influence of Insoluble and Soluble Surfactants: A Numerical Study

2019 ◽  
Vol 3 (3) ◽  
pp. 56
Author(s):  
Thomas Antritter ◽  
Peter Hachmann ◽  
Tatiana Gambaryan-Roisman ◽  
Bernhard Buck ◽  
Peter Stephan
Keyword(s):  
Numerical Study ◽  
Sorption Kinetics ◽  
Small Scale ◽  
Surfactant Adsorption ◽  
Insoluble Surfactant ◽  
Surfactant Transport ◽  
Soluble Surfactants ◽  
The One ◽  
Printing Processes ◽  
Soluble Surfactant

Wetting and spreading of surfactant solutions play an important role in many technical applications. In printing processes, the size of individual droplets is typically on the order of a few tens of microns. The purpose of this study is to develop a better understanding of the interaction between spreading and surfactant transport on these small length and related time scales. Therefore, numerical simulations based on the volume-of-fluid method including Marangoni stresses and transport of an insoluble or soluble surfactant are performed. The results for an insoluble surfactant show competing effects of Marangoni flow on the one hand, and a decreasing surfactant concentration as the droplet spreads on the other hand. Even in the case of a soluble surfactant, adsorption and desorption could only partly mitigate these effects, demonstrating the importance of the sorption kinetics for fast, small scale wetting processes.

Experimental and Numerical Study of Single Bubble Dynamics on a Hydrophobic Surface

2007 ◽  
Author(s):  
Youngsuk Nam ◽  
Gopinath Warrier ◽  
Jinfeng Wu ◽  
Y. Sungtaek Ju
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Growth Period ◽  
Hydrophobic Surface ◽  
Bubble Surface ◽  
Bubble Nucleation ◽  
Root Mean Square Roughness ◽  
Energy Harvesters ◽  
Enhanced Boiling

The growth and departure of single bubbles on two surfaces with very different wettability is studied using high-speed video microscopy and numerical simulation. Isolated artificial cavities of approximately 10μm diameter are microfabricated on a bare and a Teflon-coated silicon substrate to serve as nucleation sites. The bubble departure diameter is observed to be almost three times larger and the growth period almost 60 times longer for the hydrophobic surface than for the hydrophilic surface. The waiting period is practically zero for the hydrophobic surface because a small residual bubble nucleus is left behind on the cavity from the previous ebullition cycle. The experimental results are consistent with our numerical simulations. Bubble nucleation occurs on nominally smooth hydrophobic regions with root mean square roughness (Rq) less than 1 nm even at superheat as small as 3 °C. Liquid subcooling significantly affects bubble growth on the hydrophobic surface due to increased bubble surface area. Fundamental understanding of bubble dynamics on heated hydrophobic surfaces will help to develop chemically patterned surfaces with enhanced boiling heat transfer and novel phase-change based micro-actuators and energy harvesters.

Boundary Element Simulations of Free and Forced Bubble Oscillations in Potential Flow

2014 ◽  
Author(s):  
Yulia A. Itkulova ◽  
Olga A. Abramova ◽  
Nail Gumerov ◽  
Iskander Akhatov
Keyword(s):  
Boundary Element ◽  
Potential Flow ◽  
Bubble Dynamics ◽  
Fast Multipole Method ◽  
Computational Cost ◽  
Bubble Surface ◽  
Graphics Processors ◽  
Problem Size ◽  
Linear Interaction ◽  
Bubble Oscillations

The study of shrinking, expanding, and strongly interacting bubbles at high Reynolds numbers is of significant interest for micro- and nanotechnologies. One of such interests is related to self-propulsion of bubbles due to non-linear interaction of bubble shape modes. In the present study bubble dynamics in potential flow is considered. The boundary element method (BEM) which offers a low computational cost and provides an accurate representation of bubble surface is employed for studies. To accelerate computations and increase problem size the fast multipole method (FMM) and graphics processors (GPUs) are used. For mesh stabilization, which appears to be an issue, a new parametric spherical filter based on spherical harmonic expansion is developed and implemented. The dynamics of high order surface modes of bubble at free and forced bubble oscillations is studied.

A new formulation and analysis of a collapsing bubble with different content in a liquid induced during acoustic cavitation

2016 ◽  
Vol 26 (6) ◽  
pp. 1729-1746
Author(s):  
Ali Alhelfi ◽  
Bengt Ake Sunden
Keyword(s):  
Partial Differential Equations ◽  
Numerical Model ◽  
Differential Equations ◽  
Bubble Dynamics ◽  
Acoustic Cavitation ◽  
Ultrasonic Field ◽  
Bubble Surface ◽  
Correct Prediction ◽  
Partial Differential ◽  
Content Type

Purpose – The purpose of this paper is to present numerical investigation of the gas/vapor bubble dynamics under the influence of an ultrasonic field to give a more comprehensive understanding of the phenomenon and present new results Design/methodology/approach – In order to formulate the mathematical model, a set of governing equations for the gas inside the bubble and the liquid surrounding it are used. All hydrodynamics forces acting on the bubble are considered in the typical solution. The systems of equations required to be solved consist of ordinary and partial differential equations, which are both nonlinear and time dependent equations. A fourth order Runge-Kutta method is applied to solve the ordinary differential equations. On the other hand, the finite difference method is employed to solve the partial differential equations and a time-marching technique is applied. Findings – The numerical model which is developed in the current study permits a correct prediction of the bubble behavior and its characteristics in an acoustic field generated at this occasion. Originality/value – Previous studies considering numerical simulations of an acoustic bubble were performed based on the polytropic approximation or pressure uniformity models of the contents inside the bubble. In this study, an enhanced numerical model is developed to study the acoustic cavitation phenomenon and the enhancement concerns taking into account both the pressure and temperature gradients inside the bubble as well as heat transfer through the bubble surface into account which is very important to obtain the temperature of the liquid surrounding the bubble surface.

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