Bubbles In non-Newtonian Fluids Research Articles

Hydrodynamics and Interfacial Surfactant Transport in Vascular Gas Embolism

Abstract Vascular gas embolism—bubble entry into the blood circulation - is pervasive in medicine, including over 340,000 cardiac surgery patients in the U.S. annually. The gas–liquid interface interacts directly with constituents in blood, including cells and proteins, and with the endothelial cells lining blood vessels to provoke a variety of undesired biological reactions. Surfactant therapy, a potential preventative approach, is based on fluid dynamics and transport mechanics. Herein we review literature relevant to the understanding the key gas–liquid interface interactions inciting injury at the molecular, organelle, cellular, and tissue levels. These include clot formation, cellular activation, and adhesion events. We review the fluid physics and transport dynamics of surfactant-based interventions to reduce tissue injury from gas embolism. In particular, we focus on experimental research and computational and numerical approaches involving how surface-active chemical-based intervention. This is based on surfactant competition with blood-borne or cell surface-borne macromolecules for surface occupancy of gas–liquid interfaces to alter cellular mechanics, mechanosensing, and signaling coupled to fluid stress exposures occurring in gas embolism. We include a new analytical approach for which an asymptotic solution to the Navier–Stokes equations coupled to the convection-diffusion interaction for a soluble surfactant provides additional insight regarding surfactant transport with a bubble in non-Newtonian fluid.

On the terminal velocity of single bubbles rising in non-Newtonian power-law liquids

To describe bubbly flows, an accurate prediction of the bubble rise velocity is crucial. For non-Newtonian fluids, closures for the bubble rise velocity provided in the literature are usually empirical and rather restricted in their applicability. In this work, a Front-Tracking Computational Fluid Dynamics model has been used to investigate the behaviour of a single bubble rising in a power-law fluid, for a very wide range of viscosities covering both shear-thinning and shear-thickening behaviour, where the power-law exponent n was varied between 0.5 and 1.5 and for three different bubble diameters (viz. 0.5 mm, 2 mm and 4 mm). The non-Newtonian behaviour of the continuous phase strongly influences the shape of the single rising bubbles caused by the viscosity profiles that develop in the flow field. As a consequence, large non-spherical bubbles become more spherical in shear-thickening fluids (in comparison to the same bubble in a Newtonian liquid), whereas small spherical bubbles lose their sphericity in shear-thinning fluids. To determine the bubble rise velocity for bubbles in non-Newtonian fluids with a power law behaviour, the drag closure derived for bubbles rising in Newtonian liquids proposed by Dijkhuizen et al. (2010), which combines viscous drag and shape-induced drag in a single correlation, is adapted using a modified Reynolds number. In this work it is shown that this adapted correlation is able to predict the terminal rise velocity of single bubbles rising in non-Newtonian power-law fluids within 20% accuracy for the majority of the investigated cases, provided that the drag regime does not change.

Bubble pinch-off in Newtonian and non-Newtonian fluids

Bubble pinch-off is a rapid process and until now is not well-understood especially for the final stage near the breakup point. In this work, we aim at investigating the air bubble pinch-off at a submerged nozzle in various fluids, including Newtonian and non-Newtonian fluids. Different fluids exert different effects on the pinch-off dynamics as well as shape evolution immediately after pinch-off. A scaling law was applied to describe the bubble pinch-off in Newtonian fluids and the exponents: b=0.5 for low viscosity fluids and b=1 for high viscosity fluids, are in a good agreement with the conventional values predicted by the numerical simulation. For bubbles in non-Newtonian fluids, the pinch-off dynamics is mainly governed by the fluid rheology. The universal scaling exponent exists between 0.5 and 1 for low shear-thinning fluids while a non-universal character occurs for bubble pinch-off in high shear-thinning fluids. Our experimental results were confirmed by the numerical simulation.

Shock wave emission from a hemispherical cloud of bubbles in non-Newtonian fluids

Shock wave emission from a hemispherical cloud of bubbles, situated in non-Newtonian fluids, is investigated by high-speed photography, with up to 20million frames/s and an exposure time of 5ns, and acoustic measurements. The non-Newtonian fluids consist of a 0.5% polyacrylamide (PAM) aqueous solution, with a strong elastic component, and a 0.5% carboxymethylcellulose (CMC) aqueous solution, with a weak elastic component. In the relatively inelastic CMC solution, the maximum amplitude and the duration of the shock wave emitted during bubble cloud rebound are almost identical to the case of water. A significant reduction of the shock wave pressure was found in the elastic PAM solution. This difference ranges from a factor of 2, for a maximum radius of the bubble cloud Rmax≈800μm, up to a factor of 3, at Rmax≈270μm. A decrease of the shock wave duration was also observed in the elastic PAM solution. The observed reduction is attributed to an increased resistance to extensional flow which is conferred upon the liquid by the polymer additive and to an increase of the cavitation threshold of the liquid. At a maximum radius of about 400μm, the shock pressure for a bubble cloud, situated in water and 0.5% CMC solution, is with a factor of six larger than the value measured in the case of individual cavitation bubbles. This difference is smaller in the case of a 0.5% PAM solution where the shock pressure for a bubble cloud is only three times larger than for a single bubble. The results are discussed with respect to cavitation erosion in polymer solutions and collateral effects in pulsed high-intensity focused ultrasound surgery, such as histotripsy used for the destruction of blood clots.

Chaotic behavior of gas bubble in non-Newtonian fluid: a numerical study

In the present paper, the nonlinear behavior of bubble growth under the excitation of an acoustic pressure pulse in non-Newtonian fluid domain has been investigated. Due to the importance of the bubble in the medical applications such as drug, protein or gene delivery, blood is assumed to be the reference fluid. Effects of viscoelasticity term, Deborah number, amplitude and frequency of the acoustic pulse are studied. We have studied the dynamic behavior of the radial response of bubble using Lyapunov exponent spectra, bifurcation diagrams, time series and phase diagram. A period-doubling bifurcation structure is predicted to occur for certain values of the effects of parameters. The results show that by increasing the elasticity of the fluid, the growth phenomenon will be unstable. On the other hand, when the frequency of the external pulse increases the bubble growth experiences more stable condition. It is shown that the results are in good agreement with the previous studies.

Bubbles in Non-Newtonian Fluids: A Multiscale Modeling

In this paper, the concept of a multiscale modeling approach is highlighted with which physical phenomena at different scales can be studied. The work reports a multiscale approach to describe the dynamics of a chain of bubbles rising in non-Newtonian fluids. By means of the Particle Image Velocimetry (PIV) and the Lattice Boltzmann (LB) simulation, a deep understanding of the complex flow pattern around a single bubble is gained at microscale. The interactions and coalescences between bubbles rising in non-Newtonian fluids are experimentally investigated by the PIV measurements, birefringence and rheological characterization for both an isolated bubble and a chain of bubbles formed from a submerged orifice. Two aspects are identified as central to interactions and coalescence: the stress creation by the passage of bubbles and their relaxation due to the fluid’s memory. This competition between the creation and relaxation of stresses displays non-linear complex dynamics. Along with the detailed knowledge around a single bubble, these fundamental mechanisms governing bubbles’ collective behavior in a train of bubbles at mesoscale lead to a cognitive modeling based on behavioral rules. By simulating bubbles as adaptive agents with the surround fluid via residual stresses, model predictions for consecutive coalescence between a great number of bubbles compare very satisfactorily with the experimental investigation at macroscale. Obviously this new approach captures important quantitative and qualitative features of the collective behaviors of bubbles at macroscale level which are predicted by the mesoscopic cognitive modeling approach of the interactions rules which are deduced from the understanding of the microscopic mechanism of the flow around a single bubble.

Numerical simulation of the interactions between three equal-interval parallel bubbles rising in non-Newtonian fluids

The motion and interactions of three equal-interval parallel bubbles in non-Newtonian fluids were numerically simulated by volume of fluid method (VOF), in which the continuous surface tension model and the power-law model were adopted to represent surface tension and rheological properties of non-Newtonian fluids, respectively. The computational method was validated by the comparison of the processes of coalescence of two in-line bubbles and rising of two parallel bubbles between experiment and simulation. This method was then applied to study the effect of initial bubble diameter, initial horizontal bubble interval and rheological properties of non-Newtonian fluids on lateral coalescence and rising of three parallel bubbles. The dimensionless critical horizontal interval of bubble coalescence was obtained under different physical property conditions. The critical horizontal interval of bubble coalescence decreases with the increase of initial bubble diameter and flow index of non-Newtonian fluids. When the initial horizontal bubble interval is less than the critical horizontal interval of bubble coalescence, three bubbles will coalesce into a bigger bubble. The coalescing bubble could breakup into two identical daughter bubbles when the initial bubble diameter was increased or the flow index of non-Newtonian fluids was decreased. Three parallel bubbles rising in non-Newtonian fluids will experience repulsive interactions once the initial horizontal bubble interval is greater than the critical horizontal interval of bubble coalescence, the horizontal bubble interval increased gradually owing to the repulsive effect, while the vertical distance between bubbles varied dramatically for spherical bubble and ellipsoidal bubble due to the differences of their flow field structures.

The Drag Coefficient and the Shape for a Single Bubble Rising in Non-Newtonian Fluids

The dynamical characteristic of a single bubble rising in non-Newtonian fluid was investigated experimentally. The bubble aspect ratio and rising velocity were measured by high speed camera. The shape regimes for bubbles in non-Newtonian fluids was plotted by means of Reynolds number Re, Eötvös number Eo and Morton number Mo. The effects of bubble shape and liquid rheological property on the total bubble drag coefficient were studied. A new empirical drag coefficient correlation covering spherical bubble and deformed bubble was proposed, the predicted results shows good conformity to experimental values over a wide range of 0.05 < Re < 300.

Gas–liquid flow stability and bubble formation in non-Newtonian fluids in microfluidic flow-focusing devices

This communication describes the gas–liquid two-phase flow patterns and the formation of bubbles in non-Newtonian fluids in microfluidic flow-focusing devices. Experiments were conducted in two different polymethyl methacrylate (PMMA) square microchannels of, respectively, 600 × 600 and 400 × 400 μm. N2 bubbles were generated in non-Newtonian polyacrylamide (PAAm) solutions of different concentrations. Slug bubble, missile bubble, annular and intermittent flow patterns were observed at the cross-junction by varying gas and liquid flow rates. Gas and liquid flow rates, concentration of PAAm solutions, and channel size were varied to investigate their effect on the mechanism of bubble formation. The bubble size was proportional to the ratio of gas/liquid flow rate for slug bubbles and could be scaled with the ratio of gas/liquid flow rate as a power–law relationship for missile bubbles under wide experimental conditions.

Modified model of bubble formation in non-Newtonian fluids

Based on the comprehensive forces balance model, a modified model of the formation of a single bubble in non-Newtonian fluid under constant flowrate was developed by taking account of the effect of the ingoing gas through orifice as well as its variation on the radial expansion of bubble. The modified model involves the radial expansion equation of bubble surface and the forces balance equation in vertical direction of the bubble respectively. The shape variation of bubbles formed in polyacrylamide (PAM) aqueous solutions under various conditions was predicted numerically. The practical formation of bubbles was real-time visualized and recorded by a CCD camera and a computer by means of a special laser image measurement system. Results show that the predicted shapes of the bubbles by the present model agree well with experimental observation.

Origin of the negative wake behind a bubble rising in non-Newtonian fluids

The present work aims at understanding the behavior of individual bubbles in non-Newtonian fluids. By means of a Particle Image Velocimetry (PIV) device, the complete flow field around either a single non-spherical bubble rising in polyacrylamide (PAAm) solutions or a solid sphere settling down in the same fluids shows for the first time the similar coexistence of three distinct zones: a central downward flow behind the bubble or the sphere (negative wake), a conical upward flow surrounding the negative wake zone, and an upward flow zone in front of the bubble or the sphere. This excludes then the possible influence of the interface deformation on the negative wake. A theoretical lattice Boltzmann scheme coupled to a sixth-order Maxwell model was developed for computing the complex flow field around a solid sphere. The good agreement with the experimental measurements provides evidence that the physical mechanism responsible for the negative wake in such fluids could be related to the fluid's viscoelastic properties.

Towards the understanding of bubble interactions and coalescence in non-Newtonian fluids: a cognitive approach

The present work provides new insights into the behavior of air bubbles in non-Newtonian fluids. The interactions and coalescence between bubbles rising in non-Newtonian fluids were simultaneously investigated by means of birefringence measurements and particle image velocimetry for a chain of bubbles formed from a submerged orifice. Two aspects are identified for the first time as central to interactions and coalescence: (i) the stress creation by the passage of bubbles, and (ii) their relaxation due to the fluid's memory. This competition displays complex nonlinear dynamics, from periodic phenomena to deterministic chaos. From these fundamental mechanisms, a cognitive model based on behavioral rules has been developed to describe collective behaviors of a group of bubbles. By simulating bubbles as adaptive agents with their fluid via residual stresses, model predictions for consecutive coalescence between a great number of bubbles compare very satisfactorily with the experimental investigation.

Bubbles in non-Newtonian fluids: Formation, interactions and coalescence

The present work aims at studying the behaviors of air bubbles in non-Newtonian fluids from formation to coalescence. The experimental data reveal that the bubble rise velocity depended upon the injection period and that coalescence took place for short injection periods. The rheological simulation and birefringence visualization prove for the first time that in-line interactions are governed by a dynamical competition between the creation and relaxation of stresses in fluids. The chaos analysis was applied to time series data of bubble passage recorded at different heights in the bubble column. The calculation of several parameters: the largest Lyapunov exponent, the correlation dimension, the power spectrum, and the phase portraits, corroborates the deterministic chaotic mechanism of the coalescence between bubbles. A new theoretical model was developed for describing the non-spherical bubble formation at an orifice. Owing to the knowledge of the interactions, the present model is able to calculate the instantaneous shape of the bubble during its formation and determine the final size of detachment as well as the frequency of bubble formation. The theoretical results compare very satisfactorily with the experimental investigation.

Dynamice of bubbles in non-Newtonian fluids.

Dynamice of bubbles in non-Newtonian fluids.

On Mass Transfer from Bubbles in Non-Newtonian Fluids at Low Reynolds Numbers. An Appraisal of the Thin-Boundary-Layer Approximation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOn Mass Transfer from Bubbles in Non-Newtonian Fluids at Low Reynolds Numbers. An Appraisal of the Thin-Boundary-Layer ApproximationM. Moo-Young and T. HiroseCite this: Ind. Eng. Chem. Fundamen. 1972, 11, 2, 281–282Publication Date (Print):May 1, 1972Publication History Published online1 May 2002Published inissue 1 May 1972https://doi.org/10.1021/i160042a024RIGHTS & PERMISSIONSArticle Views27Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (206 KB) Get e-Alerts