Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session J07: Bubbles: Thin Films and Foams |
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Chair: Reza Sadr, Texas A&M University at Qatar Room: Ballroom G |
Sunday, November 24, 2024 5:50PM - 6:03PM |
J07.00001: Inertial thinning of liquid sheets due to surfactants Jun Eshima, Howard A Stone, Luc Deike The thinning of liquid sheets due to Marangoni effects are of interest in the environment, industry, and healthcare. In particular, localised surface tension gradients have been suggested as a mechanism for how the cap of a bubble may rupture (Néel and Villermaux 2018 JFM), which is relevant for sea spray aerosol formation via bubble bursting. In this talk, we present the thinning of a liquid sheet (air-liquid-air) due to a localised deposition of surfactant where we focus on the regime in which inertia and Marangoni effects are in the dominant balance. Such a regime is likely to be relevant for water films. The thinning dynamics and resulting capillary waves are described in detail through the identification of suitable similarity solutions, which are compared with numerical solutions to the thin film equations. |
Sunday, November 24, 2024 6:03PM - 6:16PM |
J07.00002: Multiscale Investigation of Effect of Nanoparticles as Foam Stabilizer: From bubble to Bulk Scale Reza Sadr, Chaudhry A Usman, Harris Rabbani Understanding foam (gas dispersion in liquid phase) dynamics and stability is crucial to many industrial applications such as drug delivery and CO2 geological sequestration. Foam is highly susceptible to destabilization owing to rapid liquid drainage, gas diffusion, and bubble coalescence. This study evaluates the synergistic effect of nanoparticles (NPs) and surfactant combinations for enhancing the mechanical strength of bobbles and the foam stability at bulk scale. Various types of NPs of different surface groups and geometry (such as silica with different surface groups, graphene oxide nanoplatelets, short-length carbon nanotubes, and iron oxide nanorods) were evaluated in synthetic seawater and high temperatures for their ability to improve the foam stability. Bulk testing involved measuring foam volume, half-life, drainage rate, and bubble size distribution under controlled conditions to assess the performance of each nanoparticle-surfactant combination. Light microscopy and image processing techniques were also used to study bubble dynamics and foam coarsening in a quasi-2D setup. The results show that NPs significantly improved the foam stability by reducing drainage and bubble coalescence. The presence of NPs was found to slow the rate of bubble growth and coarsening attributed to the formation of a robust network within the foam lamellae, however excessive NPs concentrations negatively impact foam properties that can lead to aggregation. These findings suggest that NPs effectively enhance foam stability by reinforcing the foam structure at macroscopic and microscopic levels. The results also show that optimal concentration of surfactant and NPs is crucial for achieving maximum foam stability. |
Sunday, November 24, 2024 6:16PM - 6:29PM |
J07.00003: Bulk Foam Destabilization through Local Heating Bert Vandereydt, Saurabh Nath, Kripa K Varanasi As chronic diseases become more prevalent globally, there is an increasing need for manufacturing and testing of drug and therapeutic treatments. Bioreactors are a commonly used tool in this process, from lab-scale strain and cell line development to large-scale manufacturing of for example monoclonal antibodies (mAbs), insulin, and human growth hormone. Gas is often introduced into the culture media for maintaining appropriate levels of dissolved gasses, such as oxygen. In this process of bubbling through the reactor a layer of foam is created, stabilized by the proteins and surfactants in the media. The foam is an unwanted side-effect as it decreases the productivity of the reactor due to cell entrapment and loss of valuable bioreactor space. Foam leads to a further decrease in efficiency through a reduction of gas transfer rates from the headspace, and significant downtime and loss of productivity required for careful handling of foam. The problem is exacerbated further by the constant need for higher cell densities and product yields, increasing the oxygen demand of the process and hence the foaming problem. |
Sunday, November 24, 2024 6:29PM - 6:42PM |
J07.00004: Numerical investigation of the deformation of solid surfaces due to bubble collapse Baudouin Fonkwa Kamga, Eric Johnsen The growth and collapse of cavitation bubbles near solid boundaries has been shown to induce permanent deformations and eventually material erosion. In this study, we numerically investigate the inertial collapse of a spherical bubble near a solid wall. To do so, we use a diffuse interface approach in a fully Eulerian framework capable of representing any number of fluid and solid phases via hyperbolic conservation laws. The stress and deformation in the solids are captured by solving an evolution equation for local cobasis of the deformation tensor. The numerical diffusion of interfaces, inherent to this family of schemes, is addressed by the addition of a Phase-Field method, based on the Allen-Cahn formulation. The computational cost is reduced by making use of adaptive mesh refinement. The overall scheme is consistent and conservative and allows to accurately capture deformed interfaces during the violent bubble collapse process. We investigate different configurations to differentiate and characterize the effects of the velocity jet and the shock wave generated during the collapse. |
Sunday, November 24, 2024 6:42PM - 6:55PM |
J07.00005: Stokes flow of an evolving fluid film with arbitrary shape and topology Cuncheng Zhu, David Saintillan, Albert Chern The dynamics of evolving fluid films in the viscous Stokes limit is relevant to various applications, such as the modeling of lipid bilayers in cells. While the governing equations were formulated by Scriven in 1960, solving for the flow of a deformable viscous surface with arbitrary shape and topology has remained a challenge. In this study, we present a straightforward discrete model based on variational principles to address this long-standing problem. We replace the classical equations, which are expressed with tensor calculus in local coordinate, with a simple coordinate-free, differential-geometric formulation. The formulation provides a fundamental understanding of the underlying mechanics and directly translates to discretization. We construct a discrete analogue of the system using the Onsager variational principle, which, in a smooth context, governs the flow of a viscous medium. In the discrete setting, instead of term-wise discretizing the coordinate-based Stokes equations, we construct a discrete Rayleighian for the system and derive the discrete Stokes equations via the variational principle. This approach results in a stable, structure-preserving variational integrator that solves the system on general manifolds. |
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