Liquid Foam Research Articles

Scaling Laws in the Dynamics of Collapse of Single Bubbles and 2D Foams.

Avalanches of rupturing bubbles play an important role in the dynamics of collapse of macroscopic liquid foams. We hypothesized that the occurrence of cascades of rupturing bubbles in foams depends, at least in part, on the power released during the rupture of a bubble. In this paper, we present results on the dynamics of single bubble bursting obtained by analyzing the pressure wave (sound) emitted by the bubble when collapsing. We found that the released energy varies linearly with bubble size, the frequency of the emitted sound follows a power law with exponent 3/2 (compatible with the Helmholtz resonator model) and the duration of a rupturing event seems to be independent of bubble size. To correlate the dynamics of individual bubbles with the dynamics of foams, we studied the occurrence of avalanches on bubble rafts and found that the phenomenon appears to be a self-organized criticality (SOC) process. The distribution functions for the size of the avalanches are a power law with exponents between 2 and 3, depending on the surfactant concentration. The distribution of times between ruptures also follows a power law with exponents close to 1, independently of the surfactant concentration.

The study of bubble size distribution in reservoir during foam flooding and optimization design of gas alternating foaming liquid injection

Foam flooding is one of the enhanced oil recovery (EOR) technologies that have great development potentials. The theoretical models of foam flooding at present include empirical models and mechanism models. The empirical models usually simplify the blocking effect of foam system in porous medium as a reduction coefficient of fluid mobility (mainly for gas phase). The mechanism models introduce the processes of foam propagation and decay, and its numerical simulation theory views these two processes as chemical reactions that involve reactants and products. However, these two kinds of foam models do not represent the micro-mechanical effects between the gas bubble and pore-throat in porous medium. In this work, a geometric model of pore-throat was established based on the core data of rate-controlled porosimetry. Then, the snap-off time of generating gas bubble in core sample was calculated with the data of foam flooding experiment. Finally, combined with numerical simulation, the distribution of bubble size in reservoir during foam flooding was calculated. Comparing different plans of gas alternating foaming liquid injection, it was found that when consuming the same amount of gas and foaming liquid, the increasing-ratio of gas alternating foaming liquid injection has a larger sweep range of foam and a more extended zone of effective-sized bubble than the constant-ratio injection does, which indicates that the increasing-ratio of gas alternating foaming liquid injection has a higher efficiency.

Generation of the bubble-free layer during the metal foaming process

This study focuses on the generation of the bubble-free layer during the fabrication of the metal foam using the direct melt foaming method. The theoretical models for the three stages during the foaming process have been established, and the boundary conditions have been discussed. The results from the theoretical study indicated that the bubble number of the liquid foam played a critical role in the generation of the bubble-free layer, thus, improving the bubble number retards the velocity of the bubble-free layer generation. The liquid film rupture led to the expansion of the local cross-sectional area of the Plateau border channel and increased the drainage velocity, thus, resulting in an enhancement in the bubble-free layer. Additionally, the verification experiments were conducted by employing the graphene nanoflakes (GNFs) as the heterogeneous nucleation agent. The findings indicated that the generation of the bubble-free layer was hindered, and the bubble-free layer was altogether absent in case the content of the heterogeneous nucleation agent was enhanced.

3D structure of lightweight, conductive cellulose nanofiber foam

We investigate the three-dimensional (3D) structuring of cellulose nanofiber (CNF) foam-based ink using direct ink writing 3D printing and the transformation of CNF foam from an insulator to a conductor. The colloidal stability of a CNF foam is critical to producing a solid CNF foam which can be used as a template for the synthesis of conducting polymers. Liquid CNF foam ink is produced by simple stirring of CNF suspension with sodium dodecyl sulfate as an emulsifier. The shear thinning behavior of the liquid CNF foam ink enables printing through a needle. Flexible design of CNF foam structures is enabled by 3D printing using computer-aided design. Lightweight conductive CNF foams are prepared via in situ polymerization of polypyrrole on a solid CNF foam. The topological features of the resultant porous conductive CNF foams are observed, and their conductivity is investigated.

Effects of butynediol alkoxylate trisiloxane on the surface activity, wetting, and foam properties of polyether trisiloxane

Foam control of polyether trisiloxane (PTS) superspreader solutions with a traditional defoamer, such as silica-filled polydimethylsiloxane, is weak or even ineffective, which represents a problem that needs to be solved. In this paper, we describe a new foam control method for PTS by blending this superspreader with low foaming butynediol alkoxylate trisiloxane (TBEO). TBEO can be dissolved in PTS, acting as a foam control agent. The two components were pre-blended in different proportions (10–90% PTS-TBEO) before dilution. Performance tests of PTS-TBEO were conducted by measuring the equilibrium surface tension, dynamic surface tension, wettability, foam morphology, and foam stability. It was found that the addition of TBEO had an insignificant effect on the equilibrium and dynamic surface tension of the PTS foaming system. In addition, with an increase in the proportion of TBEO, the spreading speed of the mixture aqueous solution at different hydrophobic interfaces slows down, but the change at a low proportion of TBEO (10–40%) is negligible. However, the introduction of TBEO with different proportions will cause the originally stable foam to show different degrees of “cliff-like” decline, and with the increase of TBEO proportion, the relative antifoam efficiency also increases. And from the perspective of the interaction between TBEO molecules and the foam liquid film, the mechanism of TBEO in suppressing foam height of PTS superspreader solution was further explored.

Application of the Agrimonia eupatoria L. Extract for the Kvases Production

The article concerns the research of the herb Common Agrimony (Agrimonia eupatoria L.) use in the kvass manufacture, because the plant has a high content of flavoring and biologically active substances (flavonoids, tannins, arbutin, etc.). Researchers used standard, adopted in the brewing and soft drinks industry test methods and methods of processing obtained results. To produce kvass with the best quality characteristics, a man has to use Agrimonia eupatoria L. extract. In order to obtain this extract with the maximum amount of flavoring and biologically active substances (polyphenolic substances, ascorbic acid) a man must macerate 3-5 mm cut grass using purified water as a solvent in a ratio of 1:10 at a temperature of 40 ± 3 °C for 5-6 hours. Agrimonia eupatoria L. extract is an opaque brown liquid with a weak greenish tint, weakly expressed sweet-apricot aroma and taste; the mass fraction of dry substances is 3.0 ± 0.1 %; acidity – 2.5 ± 0.2 units; the content of polyphenolic substances is not less than 13.5 mg / 100 cm3; the content of ascorbic acid – not less than 4.5 mg / 100 cm3 . The authors developed kvass technology, including the preparation of kvass wort and Agrimonia eupatoria L. extract separately, its blending, fermentation, cooling, clarification and bottling. Based on the organoleptic and physical and chemical parameters obtained during the study, the researchers recommended the optimal ratio of kvass wort and Agrimonia eupatoria L.: 90:10 – 80:20. They developed regulated quality indicators of the new kvass: appearance – a transparent foaming liquid with opalescence, without foreign inclusions; color – brown with greenish tones; aroma and taste – refreshing, sweet and sour, bread, with light tones of Agrimonia eupatoria L. extract. The use of an aqueous extract from the herb Agrimonia eupatoria L. in the kvass production enables to get products with original organoleptic characteristics

Quasi-two-dimensional foam flow through and around a permeable obstacle

In a study of the evolving structure of two-dimensional liquid foams flowing through an inhomogeneous confining cell, the motion and deformation of their elementary components, the bubbles, are quantified for various confinement ratios. The flow experiments highlight the elastoplastic properties of foams, controlled by their liquid fraction, which are notably responsible for the symmetry breaking of the flow, with multipolar deformation and velocity fields around the localized inhomogeneity.

Experimental studies of the removal properties of liquid and solid foaming surfactants

Using the laboratory model of a well, foaming and removal properties of liquid and solid surfactants (savenol, light and dark stinol, Sofir M2, TEAS and Nadra) are studied. The authors determine experimentally the height of the level of the foam in the glass column at the end of the foam-forming process and the duration of re-moving half volume of liquid out of the foam. Using height and duration values, the authors determine the multi-plicity and stability of the foam. Based on the results of experiments on the laboratory model of the well, a graph-ical dependence of the multiplicity and stability of the foam on the mass concentration of surfactants in fresh and salt water, in mineralized water with the addition of hydrocarbon condensate for various temperatures is con-structed. Based on the results of experimental studies, the influence of the concentration of surfactants in a foam-ing liquid, the salinity of water, hydrocarbon condensate and temperature on the foaming ability of liquid and solid surfactants for the removal of liquid from watered gas and gas condensate wells is analyzed. The authors determine the optimal values of the concentrations of foaming surfactants in aqueous solutions. Above these val-ues the multiplicity and stability of the foam varies slightly. It has been established that the outflow properties of the solid Nadra surfactant are the best in saline water and in solutions with hydrocarbon condensate, in contrast to the investigated liquid surfactants. Based on experimental studies, the patterns of foaming of aqueous surfac-tant solutions with modeling bottomhole temperature (from 20 to 80 °) are established. The authors recommend the use of various types of surfactants under different operating conditions of wells with a high fluid content in the well production. Foaming surfactants are supplied to the bottom of the well in the form of aqueous solutions and samples of solid surfactants. As a result, the foamed formation fluid brings to the surface not only the liquid phase, but also the solid particles that accumulate at the bottom due to corrosion of the pipe metal, the destruction of cement stone and rock of the bottomhole formation zone.

Description of the Preliminary Proposals and Modeling for Applying the Mechanical Foam Breakers Techniques in the Processing Trays Columns

A preliminary proposal and some novel ideas have been described and theoretically analyzed in the present study for applying the mechanical and physical foam control methods in the trays column, that some common methods have been modeled and new configurations are created. study has tried to satisfy the much promising capability to utilize the Revolving Paddles and Ultrasonic methods. flow driven foam breaker demonstrates a self-driven mechanism while it is running continuously, turbo driven and liquid sprays foam breaker models are using the same process fluids and providing a clean fast correction action, Stethoscope and magnetostriction Ultrasonic models are utilizing the Ultrasonic waves for defoaming action. the recognized designs supposed applicable and reliable to be installed and functioned in the trays columns and the similar applications in different industries with no more chemical agents' consumption, accordance with the operation criteria and the technical standards and the safety precautions. CFD simulation and numerical analysis have been initiated for two models as an example that include flow driven foam breaker and the Ultrasonic Stethoscope model, while the study pointed to illustrate the basic ideas of the listed models and explored the main components and avoid going through deep details.

Analysis of the characteristics of flue gas foam seepage and its influencing factors

The flue gas foam-assisted steam flooding technology is beneficial to inhibit the steam channeling, delay the steam overriding and improve the heat utilization rate. At the same time, it is also conducive to carbon dioxide storage, which has a broad application prospect. However, the current research on the seepage characteristics and influencing factors of flue gas foam-assisted steam flooding is insufficient. In this paper, the sand pack flooding experiments were carried out by changing the gas-liquid ratio, injection rate, temperature, permeability and other parameters. The results showed that in the case of low gas-liquid ratio, the number and size of foams are small and the connectivity between foams is poor. When the gas-liquid ratio is high, the gas-phase composition is high so that gas channeling occurs and the plugging effect is reduced. Experiments showed that when the gas-liquid ratio is 2:1, the resistance factor is the largest and the plugging performance is the best. When the injection rate is 3mL/min, the foam is stable, which is beneficial to the foam plugging. When the injection rate is lower than 3 mL/min, the foam is sparse and the foam liquid film is thin so that the plugging effect is poor. When the injection flow rate is higher than 3 mL/min, more foam with smaller size will be formed under the influence of shear action, and the Jamin effect on the pore throat will be weakened, which is difficult to be plugged by the foam system. With the increase of experimental temperature, the intermolecular force of the solution was strengthened, the foam volume was enlarged and the liquid film was thinned so that the foam stability and the plugging performance were weakened. Oil saturation has a greater impact on the plugging ability of the flue gas foam. The higher the oil saturation, the weaker the plugging ability is. The research can provide reference for the application of flue gas foam plugging technology.

Experimental Study of Foam Flow in Highly Permeable Porous Media for Soil Remediation

Foam has shown promising characteristics for soil remediation, especially as a blocking agent. In very permeable porous media, high groundwater velocity reduces the efficiency of in situ remediation by decreasing the contact time with contaminants. To use foam to reduce water velocity, this paper investigates its properties in very permeable porous media (> 4.10−10 m2). Alpha olefin sulfonate foam injection experiments were conducted in columns containing glass beads or sand, with varying permeabilities and injection techniques. Pressure and mass balance data were acquired to measure foam resistance factor and liquid saturation. The results show that foam pregeneration is mandatory for generating a highly viscous foam in highly permeable porous media. However, the permeability of the foam generator does not affect the results within the range studied. Pregeneration generated highly viscous foam, even in very high permeable porous media (> 10−9 m2). The influence of permeability on the apparent viscosity of foam in porous media was related to the shear-thinning foam behavior. These experimental results show that foam injection is a relevant method for water blocking and mobility control in highly permeable porous media.

Ultrasoft Liquid Metal Elastomer Foams with Positive and Negative Piezopermittivity for Tactile Sensing

AbstractSoft, capacitive tactile (pressure) sensors are important for applications including human–machine interfaces, soft robots, and electronic skins. Such capacitors consist of two electrodes separated by a soft dielectric. Pressing the capacitor brings the electrodes closer together and thereby increases capacitance. Thus, sensitivity to a given force is maximized by using dielectric materials that are soft and have a high dielectric constant, yet such properties are often in conflict with each other. Here, a liquid metal elastomer foam (LMEF) is introduced that is extremely soft (elastic modulus 7.8 kPa), highly compressible (70% strain), and has a high permittivity. Compressing the LMEF displaces the air in the foam structure, increasing the permittivity over a large range (5.6–11.7). This is called “positive piezopermittivity.” Interestingly, it is discovered that the permittivity of such materials decreases (“negative piezopermittivity”) when compressed to large strain due to the geometric deformation of the liquid metal droplets. This mechanism is theoretically confirmed via electromagnetic theory, and finite element simulation. Using these materials, a soft tactile sensor with high sensitivity, high initial capacitance, and large capacitance change is demonstrated. In addition, a tactile sensor powered wirelessly (from 3 m away) with high power conversion efficiency (84%) is demonstrated.

Temperature dependence of film rupture and internal structural stability in liquid aluminium alloy foams

The morphology of solid metallic foams is governed by the evolution of the cellular structure during the foaming process in the liquid state. We study quantitatively film ruptures in liquid aluminium alloy foams and determine their temperature dependence and spatial distribution and analyse how they evolve during isothermal holding. The coalescence rate of AlSi8Mg4 and AlSi9 foams was found to increase linearly with temperature within the range studied. We introduce the term “internal structural stability” and quantify it by using the total number of bubbles and the coalescence rate. Furthermore, a probabilistic approach allows us to fit and extrapolate the number of bubbles as a function of holding time and to predict foam half-lives. Application of the two methods allows us to compare two established foamable alloys and to conclude that the internal structure of liquid AlSi8Mg4 foams is around 50% more stable than of AlSi9 foams.

Optimal Energy-Saving Device for Controlling Liquid (Foam) Processing of Fibrous Materials

The task was posed and solved to develop an optimal energy-saving device for controlling liquid (foam) processing of fibrous materials. The expected technical result is the processing of fibrous materials in a foam medium with specified physicochemical properties by intensifying foaming on the surface of the processed fibrous material. The effect of foam treatment on the deformation properties of the material is determined.

Trapping of swimming microalgae in foam.

Massive foam formation in aquatic environments is a seasonal event that has a significant impact on the stability of marine ecosystems. Liquid foams are known to filter passive solid particles, with large particles remaining trapped by confinement in the network of liquid channels and small particles being freely advected by the gravity-driven flow. By contrast, the potential role of a similar retention effect on biologically active particles such as phytoplankton cells is still relatively unknown. To assess if phytoplankton cells are passively advected through a foam, the model unicellular motile alga Chlamydomonas reinhardtii (CR) was incorporated in a bio-compatible foam, and the number of cells escaping the foam at the bottom was measured in time. Comparing the escape dynamics of living and dead CR cells, we found that dead cells are totally advected by the liquid flow towards the bottom of the foam, as expected since the diameter of CR remains smaller than the typical foam channel diameter. By contrast, living motile CR cells escape the foam at a significantly lower rate: after 2 hours, up to 60% of the injected cells may remain blocked in the foam, while 95% of the initial liquid volume in the foam has been drained out of the foam. Microscopic observation of the swimming CR cells in a chamber mimicking the cross-section of foam internal channels revealed that swimming CR cells accumulate near channels corners. A theoretical analysis based on the probability density measurements in the micro chambers has shown that this trapping at the microscopic scale contributes to explain the macroscopic retention of the microswimmers in the foam. At the crossroads of distinct fields including marine ecology of planktonic organisms, fluid dynamics of active particles in a confined environment and the physics of foam, this work represents a significant step in the fundamental understanding of the ecological consequences of aquatic foams in water bodies.

Formulation and Effectiveness Test of Eschericia coli Bacteria Organic Liquid Soap Preparations Aloe Vera Leaf (Aloe Vera Linn)

Research on organic liquid soap formulations and the effectiveness test of Echericia coli bacteria from Aloe vera (Aloe vera linn) have been conducted. This research aims to formulate and test the effectiveness of liquid soap preparations using natural ingredients. The formulation is made by aloe vera leaves, sodium chloride, suji leaf coloring, and the lime scent with concentrations of 10%, 25%, and 50%. The results of the research organoleptic test process were the results of soap preparations with liquid texture, the lime scent and the typical green color of suji leaves. The pH of the observations was 6 for various concentrations. High liquid soap foam with 10% concentration obtained an average of 89.27 mm, a concentration of 25%, 69.46 mm, and a concentration of 50% with an average of 52.05 mm. the result of liquid test specific soap obtained from 10% concentration is 1.037g / ml, 25% concentration is 1.048 g / ml and 50% concentration is 1.059 g / ml. the resultsof research obstacles zone on Echericia coli bacteria obtained an average of 16.7 mm for a concentration of 10%, 18.7 mm for a concentration of 25%, and a obstacles zone of 22.7 mm for a concentration of 50% and for irritation test 100% found no irritation.

Nanobubble-Assisted Nanopatterning Reveals the Existence of Liquid Quasi-Two-Dimensional Foams Pinned to a Water-Immersed Surface.

This paper reports on our observation of a quasi-two-dimensional (quasi-2D) liquid nanofoam spontaneously appearing on a submersed solid surface. Unlike common liquid foams existing on top of the liquid, the quasi-2D liquid nanofoam is pinned to a water-immersed solid surface. The foam imaging was performed by a nanobubble imprint technique, which allows recording the positions of the surface nanobubbles by their imprints in a polystyrene film, as described in our previous papers [Tarábková et al. Langmuir 2014, 30, 14522; Tarábková et al., Langmuir 2016, 32, 11221]. Nanobubble imprints are then examined by ex situ atomic force microscopy. Besides randomly distributed nanoprotrusions corresponding to solitary nanobubbles, quasi-periodic arrangements of a tight cellular structure and more spaced round-shaped patterns, corresponding to "dry" and "wet" quasi-2D micro- and nanofoams, respectively, are identified. Although randomly spread solitary nanobubbles can occupy up to 30% of an immersed solid surface, their self-organization in a quasi-2D nanofoam leads to surface gas coverage reaching up to 80%, which implies significantly lowered surface wetting. Existence of a submersed quasi-2D nanofoam thus opens the novel question on the impact of dense surface nanobubble assemblies on heterogeneous processes at the solid-liquid interface.

Formation and rupture of gas film of antibubble

The formation and rupture of gas film in the process of formation, rupture and coalescence of antibubbles were investigated by high-speed photography. It was found that a gas film will appear and wrap a droplet when the droplet hit a layer of liquid film or foam before impacting the gas-liquid interface. The gas film may survive the impact on the gas-liquid interface and act as the gas film of an antibubble. A multilayer droplet will be formed when the droplet hits through several layer of liquid films, and a multilayer antibubble will be formed when the multilayer droplet impact a gas-liquid interface or a single layer of foam on the liquid surface. The way to generate antibubbles by liquid films will undergo the formation and rupture of gas films. The coalescence of two antibubbles, which shows a similar merging process of soap bubbles, also undergo the rupture and formation of gas films. The rupture of gas film of antibubble caused by aging and impact is also discussed.

Foam sclerotherapy compared with liquid sclerotherapy for the treatment of lower extremity varicose veins: A protocol for systematic review and meta analysis.

There is a continued discussion on which is the best sclerosant to treat lower extremity varicose veins. Therefore, we did this meta-analysis to determine that foam sclerotherapy versus liquid sclerotherapy, which could perform better in the treatment of lower extremity varicose veins. We independently searched 5 databases from inception to February 1, 2019, for randomized controlled trials and prospective controlled trials for comparing foam sclerotherapy and liquid sclerotherapy for the treatment of lower extremity varicose veins. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of studies. The primary outcome and secondary outcomes were analyzed using stata 15.0. This meta-analysis was performed according to Cochrane Handbook. There were significant differences in effective rate (P < .001, odd ratios = 5.64, 95% confidence interval = 3.93-8.10) and incidence rate of pain (P = .030, odd ratios = 1.52, 95% confidence interval = 1.04-2.21) between foam sclerotherapy and liquid sclerotherapy. And there were no significant differences among local inflammation (P = .896, rate difference = 0.00, 95% confidence interval = -0.03 to 0.03), thrombophlebitis (P = .90, rate difference = 0.00, 95% confidence interval = -0.02 to 0.02) and hyperpigmentation (P = .336, rate difference = 0.05, 95% confidence interval = -0.05 to 0.14). Although foam sclerotherapy has a higher incidence rate of complications, it could achieve a more stable clinical efficacy in the treatment of lower extremity varicose veins than liquid sclerotherapy.

Modelling of foamed emulsion drainage

The drainage of foams created using emulsions has been investigated from both experimental and theoretical point of view. The drainage of emulsion foam is investigated using mixture of sodium dodecyl sulphate and oil, which were prepared using the double syringe method. For the preparation of each emulsion, SDS solution and oil are passed from one syringe into the other through a plastic tube leading to thorough mixing. In the course of drainage both the foam height and the thickness of the free liquid layer accumulated at the bottom of the foam were measured. A theoretical model was developed, taking into account both surface viscosity and non-Newtonian behaviour of the foamed emulsion to describe the time evolution of both the foam height and the thickness of the free liquid layer. The model is based on consideration of drainage of non-Newtonian liquid through the Plateau borders and the mobility of the gas/liquid interface is taken into account. Both experiments and theoretical predictions show no measurable change of the foam height while a free liquid layer starts to accumulate at the bottom boundary of the foam after an initial rapid increase of liquid volume fraction to the maximum value at the bottom of the foam. Theoretical predictions of rate of drainage, free liquid layer formation, foam height and liquid volume fraction for foamed emulsion systems of various oil volume fractions are compared with experimental observations. Comparison of the predicted and the experimentally measured time dependences showed a reasonable agreement.