Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session T35: Bubbly Flow Physics II |
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Chair: Martin Bertodano, Purdue University Room: 243 |
Monday, November 21, 2022 4:10PM - 4:23PM |
T35.00001: Exact computation of the color function from piecewise linear interfaces Désir-André KOFFI BI, Stephane L Zaleski, Basil Kottilingal, Gretar Tryggvason, Serena Costanzo, Ruben Scardovelli, Yue Ling, Jiacai Lu A good evaluation of the color function is of importance in the simulation of multiphase flows, both for use in obtaining accurate surface tension and generally for capturing realisitc physics. The errors of some methods such as the Front-Tracking method are especially acute when the density ratio is large. Then small errors in the color evaluation can lead to large errors in the density, and as a consequence erroneous velocity field. A new geometric computation of the color function from piecewise linear interfaces (called "Front2VOF") is presented, allowing an exact computation of the volume inside a triangulated surface intersecting an arbitrary cubic grid cell. Thus the method is of use within the Front-Tracking method, and is implemented in the PARIS Simulator (http://www.ida.upmc.fr/~zaleski/paris/index.html) code. The computation is independant of direction of integration. Tests are conducted using the oscillating bubble case, and comparisons are done between the Front2VOF algorithm and other methods based on the solution of a Poisson equation. |
Monday, November 21, 2022 4:23PM - 4:36PM |
T35.00002: Computational studies of gas-liquid-solid flows in froth flotation Lei Zeng, Jiacai Lu, Gretar Tryggvason Froth flotation, where buoyant bubbles are used to separate hydrophobic particles from a slurry and bring them to the top of a tank where they can be skimmed off, is the most widely used mineral separation technique. While many of the processes involved are reasonably well understood, their complex interactions make it difficult to predict the overall selectivity. Here we use fully resolved numerical simulations to examine the interactions of large bubbles with smaller hydrophobic and hydrophilic particles. The bubbles are followed using a front-tracking/finite volume method and the solid particles are included as regions of different density with zero deformation gradient. The Generalized Navier Boundary Condition (GNBC) is used to model the triple-point, for particles sticking to bubbles. We show results for single and several bubbles moving through fluid containing many solid particles and discuss how the various governing parameters, such as bubble size and deformability and the volume fraction of both the gas and the solids affect the rate at which bubbles collect hydrophobic particles. Preliminary results for the formation of particle laden foam at the free surface are also shown. |
Monday, November 21, 2022 4:36PM - 4:49PM |
T35.00003: Numerical simulations of bubble oscillations and detachment on electrodes in aqueous electrolysers used for green hydrogen production Thomas Abadie, Bhavani Chinnathambi, Morgan Kerhouant, Omar K Matar Bubble formation, detachment and dynamics are of key importance for designing efficient electrochemical processes such as hydrogen production. In aqueous electrolytic solutions, the dissolved gas supersaturation, the continuous phase dynamics, as well as the surface properties influence bubble formation and the resulting void fraction. In addition, the bubble sizes and their frequency of detachment affect the electrode coverage and resulting overpotentials, which can be detrimental to efficient electrochemical processes. While research has focused on hydrophobic micro-structured surfaces to minimize the adhesion forces and therefore bubble diameters, less attention has been brought to dynamic boundary conditions at the surface of the electrode due to the change in contact angle as a result of temperature, potential and concentration gradients along the electrode. In this study, we use the open-source platform OpenFOAM to solve the one-fluid formulation of the Navier-Stokes equations as well as the transport of dissolved gases in the aqueous solution. The fluid transport equations are coupled to the electrostatic equations and the contact angle at the electrode varies with the voltage. The methodology is validated through comparison with literature data and simulations are performed to study the effects of operating conditions, namely varying contact angle and shear flow on bubble detachment. |
Monday, November 21, 2022 4:49PM - 5:02PM |
T35.00004: A numerical study on horizontal clustering of rising air bubbles Ingu Lee, Haecheon Choi In bubbly flows, the hydrodynamic interactions among bubbles and flow structure result in inhomogeneous distributions of bubbles. We perform direct numerical simulations of air bubbles rising in stagnant water to investigate their clustering mechanism. A bubble interface is tracked by a level-set method, and bubble coalescence is modeled based on a contact time concept in film-drainage theory. Strong and weak horizontal clusterings occur in monodispersed rising bubbles with small (deq = 1mm) and large (deq = 2mm and 3mm) bubbles, respectively. In all cases, the bubbles at short distances (rij <2deq) tend to align horizontally. This alignment is caused by vortex-induced interactions as well as by potential interactions. After bubble-to-bubble collision without coalescence, counter-rotating vortex pair occur between the bubbles, and the structures push the bubbles against each other, while maintaining horizontal alignment. Horizontal alignment by the vortex pair occurs more frequently as the deformability of the bubbles decreases. |
Monday, November 21, 2022 5:02PM - 5:15PM |
T35.00005: Investigation of bubble transport in a turbulent recurrent flow Sanaz Abbasi, Thomas Lichtenegger, Amirfarhang Mehdizadeh The high number of degrees of freedom present in turbulent flows implies extremely expensive calculations making detailed, long-term and large-scale studies unfeasible. Therefore, the challenge of maintaining a reasonable accuracy and reducing the computational cost still exists. “Recurrence CFD” (rCFD) is a data-assisted approach to time-extrapolate the dynamics of recurrent systems. In other words, based on the temporal life-cycle characteristic of dominant flow structures obtained from a short-time detailed simulation, we study the long-time evolution of a system. Along with this time-extrapolation, we could study long-term transport processes according to the underlying flow field by solving only the passive transport equation, which renders rCFD an excellent and reliable method to study large-scale systems. |
Monday, November 21, 2022 5:15PM - 5:28PM |
T35.00006: A two-component lattice Boltzmann model for solute transport in bubbly flows Craig Byrne, Orest Shardt The mass transfer of soluble gas into and out of a solvent is an essential mechanism in processes such as oxygenation, aeration, and stripping of carbon dioxide. An effective tool to understand such systems is numerical simulation of the applicable transport equations coupled with the relevant thermodynamics of the solvent-solute mixture. This allows for determination of mass transfer rates and shape changes of dissolving/growing bubbles at different flow regimes. |
Monday, November 21, 2022 5:28PM - 5:41PM |
T35.00007: Thermofluid modeling of an oscillating heat pipe Yuxuan Li, Jeff D Eldredge, Adrienne S Lavine, Timothy S Fisher, Bruce L Drolen Transient complex thermofluid systems are widely applied in fields such as aerospace engineering and electronics cooling. Oscillating heat pipes (OHPs) are examples of such systems. They consist of serpentine channels containing trains of liquid slugs and vapor bubbles, in which the vapor bubbles thermally expand and compress, moving the train and thereby delivering heat from hot regions to cold condensers. The modeling approach reported here aims to capture the essential physics of OHPs with minimal complexity. It contains two modules. The first module solves the two-dimensional heat equation in the embedding solid structure. The second module uses first principles to solve the one-dimensional fluid motion and heat transfer equations within the fluid-filled OHP channels, including simple models for the phenomena of liquid film deposition and dynamics, nucleate boiling, and bubble dry-out, while conserving mass, momentum, and energy. These two modules are weakly coupled by the immersed boundary method (IBM), which enables flexibility in OHP channel configuration and plate shape. In contrast to previous approaches that rely on empirical correlations for model parameters, our approach treats parameters as uncertain values to be estimated by data assimilation. We compare pointwise temperature measurements with published experimental OHP studies and show good agreement. In particular, the model captures critical changes in performance due to dry-out. |
Monday, November 21, 2022 5:41PM - 5:54PM |
T35.00008: Two scale Two-Fluid Model Martin Bertodano, Alexander Bertodano, Alejandro Clausse Stability analyses are performed on a new two-mode formulation of the incompressible variational Two-Fluid Model (TFM) [A. Clausse, and M. Lopez de Bertodano, Physics of Fluids 33: 033324, 2021]. The Zuber-Findlay drift flux variables, i.e., the volumetric flux and the drift flux, are used. The two resulting momentum equations are a short wave equation for the Drift Flux describing void waves and the well-known long wave Drift-Flux Model (DFM). A dispersion analysis performed with this decomposition shows that the instabilities decouple into local and long wavelengths respectively. The analysis of the wave equation demonstrates that the inertial coupling and a slug flow drag correlation make the model well-posed dispersive and slug wave unstable because of a kinematic instability. A new two-phase kinematic condition is derived and nonlinear simulations result in pulse waves. Finally, simulations of the long-wave density wave instability with and without slug waves are performed to illustrate the two-scale capability of the current two-mode TFM. |
Monday, November 21, 2022 5:54PM - 6:07PM |
T35.00009: A numerical study of microtube geometry effect on flow boiling and pressure drop using the Volume of Fluid method Hua-Yi Hsu, Chia Wei Lin, Ranjith Kumar, Yu Chen Lin, Tzu-Chen Hung, Ming-Chieh Lin Other than high heat flux pursing, pressure is also crucial for microtube applications since it determines the power and efficiency of the pump. However, only a few studies focus on how tube geometry influences pressure drop. This study conducts a numerical investigation of the geometry effect on microtube flow boiling and pressure drop using the Volume of Fluid (VOF) method. There are three types of geometries used in this study: divergent, normal, and convergent microtubes, with different lengths and hydraulic diameter ratios. It is shown that the total pressure drop in the divergent microtube is the lowest. The heat flux will be decreased as the massive vapor bubbles clog the tube. However, the shorten divergent microtube can even obtain an increase of 35414.3 W/m2 in heat flux and reduce of 237.04 Pa in pressure drop compared to the normal one under certain flow conditions while the tube-clogging effect is not dominant. A larger inflow mass flux can delay the vapor bubble formation on the heated wall, which is beneficial to prevent the tube clogging and leads to higher heat flux. On the other hand, higher heat flux can be achieved in the convergent microtube due to the increased velocity inside the tube, but it induces the highest total pressure drop. This study can provide a better fundamental understanding of the microtube geometry effect on flow boiling and relevant physical insight for the future design of microscale heat transfer applications. |
Monday, November 21, 2022 6:07PM - 6:20PM |
T35.00010: Implementation and Verification of a Variational Two Fluid Model in Ansys CFX Raghav Ram, James Howard, Martin Bertodano A novel variational Two Fluid Model (TFM) in terms of the volumetric and drift fluxes has been derived by Clausse and Bertodano [1]. Their formulation yields the two natural modes of the TFM, i.e. the Drift Flux Model and the Two Fluid Wave Equation (TFWE). The variational method differs from the mechanistic method in that it allows a complete and objective definition of the inertial coupling based on the flow topology, resulting in a more complete dynamic TFM. |
Monday, November 21, 2022 6:20PM - 6:33PM |
T35.00011: The Emptying of a Perforated Bottle Hans Mayer, Callen Schwefler, Peyton Nienaber Bottle emptying, characterized by the familiar “glugging” of the gas and liquid flows at the neck, has previously been explored. Studies in the literature have considered the influence of bottle shape, size, inclination, and fluid properties. We have investigated an interesting scenario in which introducing a miniscule perforation, i.e., a hole typically 5% of the bottle neck diameter, can dramatically alter emptying. We report on experiments showing that perforated bottles emptying through glugging (being unaffected by the perforation in any observable way), jetting (when the perforation is large enough to allow full venting and only liquid outflow from the neck), or a combination of jetting that transitions to glugging sometime during the course of emptying. For a bottle with fixed shape and size, perforation size dictates the emptying mechanism. A combination of jetting and glugging is always found to yield emptying times exceeding the non-perforated case (glugging only). The perforation size causing maximum emptying time, and the emptying time increase, is correlated to the neck diameter. To complement our experiments, we theoretically model the emptying of a perforated bottle using a combination of existing glugging theory and single-phase flow (for the jetting regime). |
Monday, November 21, 2022 6:33PM - 6:46PM |
T35.00012: Dynamics of Argon Gas Bubble Pair Rising in Liquid Steel in the Presence of a Transverse Magnetic Field Purushotam Kumar, Surya P Vanka Bubbly flows are present in various industrial processes including metallurgical processes in which gas bubbles are injected at the bottom of bulk liquid metal to stir the liquid metal and homogenize the metal. Understanding the motion of such bubbles is essential, as it has been shown that bubble flotation can remove inclusions. In this work, we have numerically studied three-dimensional dynamics of a pair of inline Argon bubbles rising in molten steel under the influence of a transverse magnetic field. We have explored the effects of two transverse magnetic field strenghts (Bx = 0 and 0.2 T). The bubbles' motion and transient rise velocities are compared under different magnetic fields. The shape deformations and path of the bubbles are discussed. The flow structures behind the bubbles are analyzed. We found that structures are more organized and elongated under a magnetic field, whereas it is complex and intertwined when the magnetic field is not included. We have used a geometry construction-based volume of fluid (VOF) method to track interface, maintain mass balance and estimate the interface curvature. Additionally, we have incorporated a Sharp Surface Force Method (SSF) for surface tension forces. The algorithm is able to minimize the spurious velocities. |
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