Large Number Of Bubbles Research Articles

3D detection and tracking of deformable bubbles in swarms with the aid of deep learning models

A 3D tracking of individual bubbles in bubble swarms is essential for revealing and understanding bubble interactions and clustering mechanisms in bubbly flows. In this work, we address this issue and present a new method for tracking deformable bubbles in 3D based on deep learning models. We also present a new dataset of artificial bubbly flow sequences to test the tracker, which could also be used to train future detection or tracking models. Although the developed tracker had difficulties in cases with a large number of bubbles, it showed an overall good performance on the complete dataset and demonstrates the potential of deep learning models for this task. We hope that this work fosters further developments as well as applications of 3D bubble tracking that at the end lead to a deeper understanding of how deformable bubbles interact.

Experimental study on the upward annular two-phase flow of nitrogen and ethanol aqueous solutions with different concentrations

Vertical upward annular flow experiments of nitrogen gas and ethanol aqueous solutions with volume fractions of 30 %, 60 %, and 95 % under 0.2 MPa were conducted. The characteristics of the liquid film including base, average, and maximum film thickness and height, velocity, and frequency of disturbance waves were obtained and studied based on the constant electric current method in a 5 mm inner diameter polycarbonate tube. The flow behavior was observed using a high-speed camera simultaneously. It is found that a large number of bubbles in the liquid film is critical to these characteristics. A connection between ethanol concentration and bubbles in the liquid film is found and interpreted by considering bubble stability which arises from the dynamic rise in surface tension. Our experimental investigation suggests that the effect of bubbles in the liquid film on the flow characteristics is not negligible in such annular flows under high liquid flow rates and bubble stability should be considered for annular flows employing solutions consisting of two or more components with large differences in surface tension.

Turbulence induced by a swarm of rising bubbles from coarse-grained simulations

We performed numerical simulations of a homogeneous swarm of bubbles rising at large Reynolds number, $Re=760$ , with volume fractions ranging from 1 % to 10 %. We consider a simplified model in which the interfaces are not resolved, but which allows us to simulate flows with a large number of bubbles and to emphasize the interactions between bubble wakes. The liquid phase is described by solving, on an Eulerian grid, the Navier–Stokes equations, including sources of momentum which model the effect of the bubbles. The dynamics of each bubble is determined within the Lagrangian framework by solving an equation of motion involving the hydrodynamic forces exerted by the fluid accounting for the correction of the fictitious self-interaction of a bubble with its own wake. The comparison with experiments shows that this coarse-grained simulations approach can reliably describe the dynamics of the resolved flow scales. We use conditional averaging to characterize the mean bubble wakes and obtain in particular the typical shear imposed by the rising bubbles. On the basis of the spectral decomposition of the energy budget, we observe that the flow is dominated by production at large scales and by dissipation at small scales and we rule out the presence of an intermediate range in which the production and dissipation are locally in balance. We propose that the $k^{-3}$ subrange of the energy spectra results from the mean shear rate imposed by the bubbles, which controls the rate of return to isotropy.

Artificial cavernosa-like tissue based on multibubble Matrigel and a human corpus cavernous fibroblast scaffold.

Ex vivo tissue culture of the human corpus cavernosum (CC) can be used to explore the tissue structural changes and complex signaling networks. At present, artificial CC-like tissues based on acellular or three-dimensional (3D)-printed scaffolds are used to solve the scarcity of primary penis tissue samples. However, inconvenience and high costs limit the wide application of such methods. Here, we describe a simple, fast, and economical method of constructing artificial CC-like tissue. Human CC fibroblasts (FBs), endothelial cells (ECs), and smooth muscle cells (SMCs) were expanded in vitro and mixed with Matrigel in specific proportions. A large number of bubbles were formed in the mixture by vortexing combined with pipette blowing, creating a porous, spongy, and spatial structure. The CC FBs produced a variety of signaling factors, showed multidirectional differentiation potential, and grew in a 3D grid in Matrigel, which is necessary for CC-like tissue to maintain a porous structure as a cell scaffold. Within the CC-like tissue, ECs covered the surface of the lumen, and SMCs were located inside the trabeculae, similar to the structure of the primary CC. Various cell components remained stable for 3 days in vitro , but the EC content decreased on the 7 th day. Wingless/integrated (WNT) signaling activation led to lumen atrophy and increased tissue fibrosis in CC-like tissue, inducing the same changes in characteristics as in the primary CC. This study describes a preparation method for human artificial CC-like tissue that may provide an improved experimental platform for exploring the function and structure of the CC and conducting drug screening for erectile dysfunction therapy.

Experimental research on the explosion boiling mechanism of superheated liquids containing short chain alcohol impurities with different boiling points

This article investigates the mechanism of the influence of impurities in n-propanol and ethylene glycol on the explosion boiling of superheated liquids. The experimental results of studying short chain alcohol impurities showed that after the addition of short chain alcohol impurities, there were significant changes in the pressure response, temperature response, and dynamic evolution of bubble nucleation in the storage tank. Short chain alcohol impurities cause significant changes in the two-phase flow evolution behavior during superheated boiling, thereby promoting the explosive boiling of the superheated liquid. Under pure water conditions, only a small amount of bubbles are generated during the initial boiling stage, and a large number of bubbles are generated in the two-phase flow after the addition of short chain alcohol impurities. The increase in bubble density increases the porosity of the two-phase flow, which in turn affects the pressure response and temperature response inside the tank during the release process.

Coarsening of Foams Driven by Concentration Gradients of Gases of Different Solubilities.

The evolution of a foam driven by the transfer of two gases of different solubilities across the soap films is studied. A bamboo foam, or a train of films, is used as a model system; it is made of a poorly soluble gas and put into contact with a reservoir of a soluble gas at an initial time. The measurement of the time evolution of the volume of each bubble shows that the foam swells as it progressively incorporates the soluble gas. The dynamics is modeled from the gas fluxes across each film. The continuous limit of this model at a large number of bubbles is studied in detail: it gives an effective nonlinear diffusion equation, which fits the data very well. The corresponding diffusion constant, given by the product of the permeability of the soluble gas and the initial size of the bubbles, is shown to be the key parameter governing the coarsening dynamics of the foam.

Analysis of compressible bubbly flows. Part II: Derivation of a macroscopic model

This paper is the second of the series of two papers, which focuses on the derivation of an averaged 1D model for compressible bubbly flows. For this, we start from a microscopic description of the interactions between a large but finite number of small bubbles with a surrounding compressible fluid. This microscopic model has been derived and analysed in the first paper. In the present one, provided physical parameters scale according to the number of bubbles, we prove that solutions to the microscopic model exist on a timespan independent of the number of bubbles. Considering then that we have a large number of bubbles, we propose a construction of the macroscopic variables and derive the averaged system satisfied by these quantities. Our method is based on a compactness approach in a strong-solution setting. In the last section, we propose the derivation of the Williams–Boltzmann equation corresponding to our setting.

The “tornado” effect induced by magnetohydrodynamic convection in an electrolytic cell with a wire-electrode

High energy consumption is the key problem to be solved in water electrolysis for hydrogen production. Imposing magnetic field during electrolysis is proved to be a research-worthy method to reduce the required electrical energy, since the magnetohydrodynamic convection can be induced without additional energy input. Considering the structure of commercial electrolyzers, the magnetic field perpendicular to the electrode surface is most likely to be applied in practical engineering. But there is still a lack of research on the gas-liquid two-phase flow in the electrolytic cell under this condition. To avoid mutual blocking between a large number of bubbles and obtain clear two-phase flow images of the electrolysis process, a wire electrode is used as cathode to generate hydrogen bubbles in this work. The cell voltage is obviously reduced by external magnetic field, and an interesting “bubble tornado” is formed under the action of induced magnetohydrodynamic convection. The numerical simulation results and theoretical analysis indicate that: (1) the formation of the bubble chain is caused by low-pressure region along the vertical axis; (2) the unstable low-pressure region is the key factor leading to the formation of continuously deformed bubble chain; (3) the bubble dispersion may be related to Kelvin-Helmholtz flow instability. We anticipate our work being a starting point for the application of magnetic field in practical engineering.

Tube length optimization of titania nanotube array for efficient photoelectrochemical water splitting

Anodic TiO2 nanotube arrays (TNTAs) have attracted much attention due to their excellent photoelectrochemical (PEC) properties. In this work, the tube length of TNTAs was optimized for efficient PEC water splitting under two different conditions, in which very few or a massive amount of gas bubbles were generated on the electrodes. As a result, relatively longer TNTAs were found to be preferable for higher PEC performance when a larger number of bubbles were generated. This suggests that the mass transport in the electrolyte is assisted by the generated bubbles, so that the electrode surfaces are more easily exposed to the fresh electrolyte, leading to the higher PEC performance.

Corrosion electrochemical behavior of arc sprayed Al coatings

The Al coating was prepared on the surface of steel samples by arc spraying. The corrosion behavior of Al coating was analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM), electromotive potential polarization and electrochemical impedance spectroscopy (EIS). The impedance data were fitted into an appropriate equivalent circuit to explain the electrochemical corrosion behavior of the coating in different stages. The micro morphology of arc sprayed Al coating surface was observed by SEM. It was found that the Al coating surface was in tentacle and layered structure, and the coating was porous and rough, which was related to the process of thermal spraying coating. XRD results showed that the oxide content in the coating was very small, and Al was the main component. The corrosion resistance of the coating was tested by EIS. The results showed that the Al coating had high corrosion resistance at the initial stage of corrosion, and a large number of bubbles were generated on the surface of the coating when it was immersed. Because there were many pores in the coating, which facilitated the penetration of Cl- . However, with the extension of corrosion time, the coating first appeared pitting behavior. At this time, the outer surface of the corrosion hole formed an oxygen-rich area and became a cathode, and the concentration cell was formed outside the corrosion hole due to the decrease of oxygen concentration in the corrosion hole, which promoted the activation and dissolution of aluminum. The corrosion products of the coating will block the pores in the coatings, and the corrosion rate will decrease.

Study on Protein Based Adhesives Blending-Modified by Isocyanate

The price of cotton by-product cottonseed meal has been relatively stable and significantly lower than that of soybean meal, which has greater advantages for industrial raw materials. Cottonseed meal after cottonseed oil extraction accounts for 30% of the total content of plant meal, and the protein contained in cottonseed meal is not lower than soybean protein in terms of quality and quantity. At present, cottonseed meal, as a by-product of cottonseed oil extraction, is mainly used in animal feed, and cottonseed protein is not fully utilized. In this study, cottonseed meal was used as raw material. By studying the effects of modifier addition and reaction conditions on the bonding properties of cottonseed adhesive, the best process parameters for preparing the best cottonseed adhesive were explored, and the modification mechanism of cottonseed protein adhesive was revealed by analyzing the adhesives prepared under different conditions. The results showed that the solid content increased with the increase of isocyanate addition ratio, and the application period of the adhesive shortened with the increase of isocyanate addition ratio. When the addition amount was 40%, a large number of bubbles were produced in 30 minutes. The water resistance of blended modified cottonseed adhesive was tested. When the proportion of isocyanate was less than 10%, the water resistance bonding strength could not meet the requirements of national standard. Adding more than 10% isocyanate cottonseed protein adhesive to bond plywood can well meet the standard of class II plate, and the maximum bonding strength can reach 1.68mpa. The research results can not only provide a certain theoretical basis and practical guidance for the preparation of new low-cost green adhesive, but also open up a new way for the effective utilization of agricultural and forestry waste cottonseed meal.

Experimental investigation of bubble formation and motion mechanism near the moonpool

When a research ship sails at a high speed, there is relative motion between the ship and fluid. The ship is slammed by the fluid. To reduce the direct impact of the fluid, sonar is installed in the moonpool, and acoustic detection equipment is installed along the research ship bottom behind the moonpool. However, during high-speed sailing, a large number of bubbles form in the moonpool. Some bubbles escape from the moonpool and flow backward along the bottom of the ship. When a large number of bubbles are around the sonar and acoustic detection equipment, the equipment malfunctions. However, there have been few studies on bubble formation in the moonpool with sonar and distribution along the ship bottom behind the moonpool. Therefore, a related model was developed and prototype tests were carried out in this study. The appropriate similarity criteria were selected and verified to ensure the reliability of the experiment. Considering the influences of speed, sonar, moonpool shape, and draft, the reason and mechanism of bubble formation in a sonar moonpool were studied. An artificial ventilation method was used to simulate a real navigation environment. Because the bubbles are in a bright state under laser irradiation, the bubbles can be used as tracer particles. A high-speed camera captured illuminated bubbles. The distribution mechanism of bubbles along the ship bottom behind the moonpool was investigated using particle image velocimetry under the influence of the moonpool shape and sailing speed. The model experimental results agreed well with those of the prototype test. The air sucked into the water was the dominant factor in bubble formation in the moonpool. The bubbles were distributed in a W shape under the ship bottom.

Bubble bag end: a bubbly resolution of curvature singularity

We construct a family of smooth charged bubbling solitons in mathbbm{M} 4×T2, four-dimensional Minkowski with a two-torus. The solitons are characterized by a degeneration pattern of the torus along a line in mathbbm{M} 4 defining a chain of topological cycles. They live in the same parameter regime as non-BPS non-extremal four-dimensional black holes, and are ultracompact with sizes ranging from miscroscopic to macroscopic scales. The six-dimensional framework can be embedded in type IIB supergravity where the solitons are identified with geometric transitions of non-BPS D1-D5-KKm bound states. Interestingly, the geometries admit a minimal surface that smoothly opens up to a bubbly end of space. Away from the solitons, the solutions are indistinguishable from a new class of singular geometries. By taking a limit of large number of bubbles, the soliton geometries can be matched arbitrarily close to the singular spacetimes. This provides the first classical resolution of a curvature singularity beyond the framework of supersymmetry and supergravity by blowing up topological cycles wrapped by fluxes at the vicinity of the singularity.

Comparative analysis of the diagnostic value of several methods for the diagnosis of patent foramen ovale.

The aim of this research was to compare the sensitivity and positivepredictive value of contrast transcranial Doppler (c-TCD), contrast transthoracic echocardiography (c-TTE), and contrast transesophageal echocardiography (c-TEE), to determine the best method for diagnosing patent foramen ovale (PFO) and to provide a reference for the further improvement of clinical practice. We investigated 161 patients who suffered from migraines, cryptogenic stroke, TIA, and cerebral infarction of unknown cause. All patients underwent transcatheter examination, and the results of the right heart catheterization(RHC) were considered the gold standard for PFO diagnosis. The present study revealed that c-TTE with the Valsalva maneuver had a higher sensitivity in detecting PFO related right-to-left shunt (PFO-RLS), c-TCD performed similarly to c-TEE but maybe produce more false positives. Moreover, when we observed color shunt from the slit-like channel between the septum primum and the septum secundum on TEE, the positivepredictive value was the highest. Patients with suspectedPFO should be examined with c-TTE and c-TEE for confirmation. When there were a large numberof bubbles in the left heart, especially in the presence of color shunt, the positivepredictive value was the highest. The positive results of c-TCD only point out the presence of right-to-left shunt and cannot exclude extracardiac shunt, so c-TCD should not be used as a screen for PFO, additional measures such as c-TTE and c-TEE should be used.

Reconciling bubble nucleation in explosive eruptions with geospeedometers

Magma from Plinian volcanic eruptions contains an extraordinarily large numbers of bubbles. Nucleation of those bubbles occurs because pressure decreases as magma rises to the surface. As a consequence, dissolved magmatic volatiles, such as water, become supersaturated and cause bubbles to nucleate. At the same time, diffusion of volatiles into existing bubbles reduces supersaturation, resulting in a dynamical feedback between rates of nucleation due to magma decompression and volatile diffusion. Because nucleation rate increases with supersaturation, bubble number density (BND) provides a proxy record of decompression rate, and hence the intensity of eruption dynamics. Using numerical modeling of bubble nucleation, we reconcile a long-standing discrepancy in decompression rate estimated from BND and independent geospeedometers. We demonstrate that BND provides a record of the time-averaged decompression rate that is consistent with independent geospeedometers, if bubble nucleation is heterogeneous and facilitated by magnetite crystals.

Machine-vision-based acquisition, pointing, and tracking system for underwater wireless optical communications

Due to the proliferation of underwater vehicles and sensors, underwater wireless optical communication (UWOC) is a key enabler for ocean exploration with a strong reliance on short-range bandwidth-intensive communications. A stable optical link is of primary importance for UWOC. A compact, low-power, and low-cost acquisition, pointing, and tracking (APT) system is proposed and experimentally demonstrated to realign the optical link within 0.04 s, even when the UWOC transmitter and receiver are in relative motion. The system successfully achieves rapid auto-alignment through a 4 m tap water channel with a relatively large number of bubbles. Furthermore, the required minimum illumination value is measured to be as low as 7.1 lx, implying that the proposed APT scheme is robust to dim underwater environments. Meanwhile, mobility experiments are performed to verify the performance of the APT system. The proposed system can rapidly and automatically align moving targets in complex and unstable underwater environments, which can potentially boost the practical applications of UWOC.

Statistical Method of Bubble Distribution in Ship Wake Based on Digital Image

A large number of bubbles are formed in the wake of a ship when it is sailing. Statistical analysis of the wake bubbles can infer the important information of the ship such as draft, ship width and speed, which is of great significance in the military field. The experimental device is used to simulate the actual wake bubbles in this paper, and the detection method combining the sobel operator and the regionprop function is used to make effective statistics on the wake distribution. Experiments show that this paper can perform distribution statistics of wake bubbles in different situations and obtain better statistical results.

High Pressure Conduit: A Good Alternative to the Air Compressors Used in the Flotation Process

Flotation is used in various fields ranging from wastewater treatment to ore processing in mining. Flotation is largely based on aeration and oxygen transfer. By using water engineering principles, a significant amount of air bubbles can be transferred to the water in a short time. Today, conduits are the most important hydraulic structures used in aeration. The air taken from the atmosphere with the help of the air hole opening into the conduit is given to the water in bubbles. A large number of bubbles in the form of air flow accelerates the transfer of oxygen. As a result of these processes, flotation efficiency increases parallel to the aeration efficiency. In this study, a pressurized conduit integrated into the flotation cell and air bubbles are introduced into the system. In the pilot scale flotation system, the effect of various physical parameters such as conduit opening ratio, air intake hole length and diameter on flotation efficiency are investigated. Results indicate that this new system provides a very high amount of air bubbles to the flotation cell and the physical properties of the air intake hole has a significant effect on the amount of air entering the column (cell).

Effect of dissolved-gas concentration on bulk nanobubbles generation using ultrasonication

In this study, the effects of dissolved-gas concentration in liquid water on the nucleation and growth of bubbles and nanobubble (NB) generation were investigated by measuring the concentration and size distribution of NBs. Three types of liquids with different dissolved-gas concentrations—undersaturated, saturated, and supersaturated deionized (DI) water—were prepared, and NBs were generated via ultrasonic irradiation. As the dissolved-gas concentration increased, a large number of bubbles with relatively large diameters (several tens of micrometers or more) were generated, but the NB concentration decreased. The surface tension decreased with an increase in the dissolved gas concentration, and thus, the tensile strength which required for bubble growth became lower. Therefore, there were barely any NBs in supersaturated conditions because of the accelerated nucleation and bubble growth.

Large Eddy Simulation of Bubbles on the Ocean Surface under High-Speed Winds

Wan, Z.; Luo, S.; Huang, S.; Sun, Z.; Zou, Z., and Lu, X., 2021. Large eddy simulation of bubbles on the ocean surface under high-speed winds. Journal of Coastal Research, 37(1), 82–91. Coconut Creek (Florida), ISSN 0749-0208.Waves break under high-speed wind conditions, and a large number of bubbles are generated. These bubbles have an important influence on the magnitude of air–sea exchanges, including but not limited to the transfer of momentum, mass, and heat. Because of current technical limitations, it is still difficult to observe the motion and distribution of bubbles in the ocean under high-speed wind conditions. In this study, the large eddy simulation technique is used to simulate the motions and distributions of 15 bubbles with different radii at high wind speeds under Langmuir circulation. The simulation results show that under high wind speeds, the bubble radius is an important factor affecting the movement of bubbles in the ocean. Large-radius bubbles quickly escape from the seawater because of buoyancy or break into smaller-radius bubbles. At the same time, the results also show that the bubbles are mainly distributed in the near-surface layer and are concentrated in the downflow region of the Langmuir circulation.