Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session P24: Bubbly Flow II 
Hide Abstracts 
Chair: Jack Keeler, University of Manchester Room: 606 
Monday, November 25, 2019 5:16PM  5:29PM 
P24.00001: Experimental and numerical study of bubble transport within multiphase cross flow over a cylinder. Eric Thacher, Simo Makiharju Vortexinduced vibration from cross flow over a cylinder is an important design consideration in numerous applications. For single phase flow, this phenomenon has been studied extensively; however, while past researchers have shown that increasing phase fraction decreases vibration amplitude while increasing shedding frequency, the mechanisms causing these changes are not fully understood. Studying individual bubble transport may provide insight, as indicated by Voutsinas et al. (2009) who demonstrated that the frequency shift depends on bubble size. In this work we begin by studying the flow of individual bubbles over a cylinder in crossflow, to assess the time needed for bubbles to be captured in the shed vortices. Following the method of Oweis et al. (2005), the capture time is predicted using a pointparticle tracking model, as a function of bubble size, release position, and flow rate. The numerical results are then verified experimentally using high speed camera visualization of a cylinder in cross flow within a vertical flow loop. The timeresolved transport of a single stream of monodisperse bubbles from a needle and coflow apparatus is used to assess the impact of capture time on cylinder pressure fluctuations, before expanding the study to higher void fraction flows. /abstract Authors: Eric W. Thacher and Simo A. M\ [Preview Abstract] 
Monday, November 25, 2019 5:29PM  5:42PM 
P24.00002: Modeling and validation of bubbleinduced fluctuation in bubbly flows. Jubeom Lee, Hyungmin Park The nature of twophase turbulence is of a great interest academically and practically. In general, it is decomposed into two contributions; one from the shearinduced turbulence in the absence of bubbles and the other from the bubbleinduced turbulence (agitation or fluctuation). Regarding the latter, it is further broken down into nonturbulent (a potential drift) and turbulent (perturbations due to bubble wake) parts. In the present work, we are interested in this bubbleinduced fluctuation and suggest a model, which is derived based on a mixing length model (analogous to the singlephase flow turbulence) but considering the effect of neighboring bubble and bubbleinduced liquid flow. As a result, we suggest models for turbulent and streamwise normal stresses that includes the contributions from gradients of liquid velocity, void distribution, and bubble velocity. That is, we try to combine the nonturbulent and turbulent parts together. Finally, we validate our models with available data in the literature, including our own, obtained from various flow configurations such as a bubbleswarm, laminar pipe, and bubbly wake flows. We discuss the advantages and limitations of our models. [Preview Abstract] 
Monday, November 25, 2019 5:42PM  5:55PM 
P24.00003: Some notes on eddy viscosity in wallbounded turbulent bubbly flows Tian Ma, Yixiang Liao, Dirk Lucas, Andrew Bragg Recently, based on data from DNS, Ma et al. (Phys. Rev. Fluids 2, 034301, 2017) proposed a model for closing the bubbleinduced turbulence (BIT) in a typical EulerEuler twoequation model, which appears to yield improved performance for predicting $k$ and $\varepsilon$ over the previous models. The present study departures from this BIT model and purpose to use the same DNS data to investigate the behavior of the $C_\mu$ constant and standard eddy viscosity definition. It can be shown that $C_\mu$ constant computed using the DNS database has a very different behavior than that in singlephase flow. Checking closely, the deficiency originates from the description of the standard eddy viscosity that is intrinsic to this general hierarchy of EulerEuler $k\varepsilon$ type model, hence, cannot be overcome by a more complex correction function for $C_\mu$. Departing from this point, a modification to the definition of the eddy viscosity in bubbly flows is derived for the EulerEuler twoequation models. We focus on the intermediate region  a region extended from the core region, where bubbleinduced production and dissipation are nearly in balance, and find that the modified model can lead to significantly improved predictions for the mean liquid, when compared with DNS data. [Preview Abstract] 

P24.00004: ABSTRACT WITHDRAWN 
Monday, November 25, 2019 6:08PM  6:21PM 
P24.00005: Numerical twophase flows study in channels with variable crosssection. Gustavo R. Anjos Bubbles and drops dynamics through capillaries of variable crosssection still remains of considerable importance in twophase flows. The aim of this work is to investigate twophase flows found in the cooling of new generation of computer processor units in the scope of the ThermaSMART  MarieCurie/RISE Consortium. We seek to study numerically the effects of domain boundaries to the bubble dynamics, including change in the film thickness, bubble shape and vortex shedding in channels with variable crosssection using a moving mesh/boundary domain scheme, which dramatically shortens the domain length. Such a scheme moves the computational boundary nodes according to the bubble's center of mass relative to the variable crosssection of a given problem. The new methodology proposed to simulate twophase flows in variable crosssectioned channels shows good accuracy to describe interface forces and bubble dynamics in different complex geometries with moving boundaries. [Preview Abstract] 
Monday, November 25, 2019 6:21PM  6:34PM 
P24.00006: Bubbly flow in upward 90degree elbow pipe: bubble dispersion and liquid flow structure Hongseok Choi, Hyungmin Park In gasliquid 2phase flows, interfacial structure plays an important role in determining the transport characteristics, which changes with geometry and inlet condition. We experimentally investigate change in bubble dynamics and flow structures for gasliquid bubbly flow in 90degree bent square pipe, varying mean void fraction up to 3.0{\%}. Continuous phase flows are chosen as laminar (Re $=$ 550) and turbulent flows (Re $=$ 7,000). We acquire the liquidphase velocity using twophase PIV technique, while gasphase velocity and size distribution are measured with highspeed shadowgraphy. In laminar flow, bubbles move much faster than the liquid phase, resulting in a backflow and large recirculation region at the inner wall of the pipe. The size of this region increases with mean void fraction, inducing strong turbulence at the boundary. For turbulent flow, flow structure doesn't show significant change with considered void fraction, but bubble trajectories move from the inner wall to the outer wall as mean void fraction increases. As a result, location of the maximum liquidphase turbulence changes accordingly. Analysis of the interfacial force balance and mechanism for flow structure change will be discussed further. [Preview Abstract] 
Monday, November 25, 2019 6:34PM  6:47PM 
P24.00007: Transient bubble dynamics in a constricted HeleShaw channel Antoine Gaillard, Jack Keeler, Gr\'egoire Le lay, Gr\'egoire Lemoult, Anne Juel, Alice Thompson, Andrew Hazel We explore the applicability of dynamical systems concepts recently used to study the transition to turbulence in shear flows to other subcritical transitions in fluid mechanics. We are ultimately interested in the subcritical instability of the linearly stable SaffmanTaylor finger in a HeleShaw channel, where finite perturbations can initiate complex dynamics for sufficiently large values of the driving parameter. Here, we concentrate on a geometricallyperturbed HeleShaw channel which supports multiple stable modes. We experimentally investigate and classify the different timeevolution scenarios of an air bubble of given volume when varying both the flow rate and the initial bubble shape. As the flow rate increases, the bubble exhibits increasingly complex behaviors, including oscillatory deformations and transient explorations of multipletipped unstable modes which often lead to bubble breakup, followed by multiple bubble interactions. Besides, we show that long and disordered transients can be observed at large flow rates depending on the level of noise in the system. [Preview Abstract] 
Monday, November 25, 2019 6:47PM  7:00PM 
P24.00008: The transient journey and eventual fate of an air bubble travelling in a HeleShaw channel Jack Keeler, Alice Thompson, Andrew Hazel, Gregoire Lemoult, Gregoire LaLay, Antoine Galliard, Anne Juel Displacement flow in a HeleShaw channel is a canonical problem in fluid mechanics and is an archetypal example of a patternforming system. If an airbubble is placed at the opposite end then it will propagate along the channel and change shape as it does so. Recent experimental results have shown that with the introduction of a depthperturbation to the bottom of the channel the system exhibits regions of bistability, so that starting from an initially centered bubble a wide range of timedependent outcomes are possible. For small flowrates the bubble will settle towards a stable asymmetric state but for larger flowrates the bubble shape will become increasingly deformed and a large range of transient phenomena is observed, including tipsplitting and oscillatory behaviour. In this talk, we attempt to understand the transition to disorder in this system for a bubble in HeleShaw channel by finding invariant solutions, in the form of steady states and periodic orbits, of the governing equations. Inspired by recent developments in the transition to turbulence in shear flow, and using dynamical systems theory, we discuss the idea, that when the flowrate is large enough the bubble will transiently explore the stable manifolds of weakly unstable edge states of the system. [Preview Abstract] 
Monday, November 25, 2019 7:00PM  7:13PM 
P24.00009: Instabilities in fourlayer gravitydriven HeleShaw flow Ahmed Al Brahim, Sigurdur Thoroddsen We study the dynamical rearrangement of gravitationally unstable multilayer fluid in the narrow vertical gap inside a HeleShaw cell. Four layers of immiscible fluids are superposed inside the cell, which is subsequently turned over. The rearrangements are filmed with highresolution and highspeed video. We vary the fluid properties and relative thicknesses of the layers. The layers in order of increasing density are air, oil, water/glycerin mixture and perfluorohexane. The concentration of the glycerin/water mixture is used to vary its viscosity. We classify various different dynamics of stirring and breakthrough of adjacent layers. We note a prominent phenomenon, where an airpocket breaks through the highviscosity layer to erupt into the lowerviscosity perfluorohexane layer above it. We were able to establish that the eruption velocity and the interface before eruption are highly influenced by the viscosity of the glycerin/water mixture. We also find that the thickness of the layers and the locations of the eruption have minor impact on the eruption speed and the interface beyond a specific limit. We investigate the centerofmass trajectories for each layer and notice counterflows, where the center of a layer can temporarily move against buoyancy. [Preview Abstract] 
Follow Us 
Engage
Become an APS Member 
My APS
Renew Membership 
Information for 
About APSThe American Physical Society (APS) is a nonprofit membership organization working to advance the knowledge of physics. 
© 2020 American Physical Society
 All rights reserved  Terms of Use
 Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 207403844
(301) 2093200
Editorial Office
1 Research Road, Ridge, NY 119612701
(631) 5914000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 200452001
(202) 6628700