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The dynamics of bubbles have garnered extensive interest among researchers both domestically and internationally due to their applications in engineering and military fields. The exploration of the mechanisms behind bubble loading, cavitation damage, and impact destruction has always been a focal point of study. However, in practical applications, bubbles often do not occur in isolation, and the interactions between multiple bubbles are highly complex. Therefore, this study investigates the pulsation characteristics of bubbles near rigid boundaries with multiple air bubbles attached in different spatial arrangements, focusing on the coupled pulsation phenomenon between cavitation clusters and bubbles. The research indicates that this coupled pulsation phenomenon is primarily influenced by the dimensionless distance parameter γs from the bubble to the boundary, the spacing γL between the air bubbles, and the spatial arrangement. Compared to Layout II, the bubble exhibits off-axis migration and jet direction only under Layout I conditions; for spatial Layout I, when the air bubble spacing γL is fixed, the displacement of the air bubble directly above the bubble is proportional to the distance parameter γs. This research underscores the potential for mitigating cavitation-induced damage through the strategic adhesion of multiple air bubbles.

This study aims to experimentally investigate the impact of air bubbles injection on the combined energetic, exergetic, and economic performance characteristics of a plate heat exchanger (P-HEX) with a parallel fluid flow configuration. Cold water, with a fixed volume flow rate of 290 LPH, is mixed with air bubbles (flow rates ranging from 150 to 840 LPH) before entering the P-HEX. The hot water was studied in seven different volume flow rates (280 to 880 LPH) and kept at 50 °C. The results show remarkable increments in the enhancement factors of the number of transfer units and effectiveness, up to 33.17 and 5.5%, respectively, compared to single-phase flow. Furthermore, cold-water side injection boosts the maximum enhancement in the number of transfer units by 2.68 folds, compared to hot water side injection. The maximum entropy generation rate is dampened by 2.45 folds when injecting the cold-water stream instead of the hot one, and the maximum system efficiency is increased from 96.9 to 97.6%. The thermo-economic assessment further highlights the potential of air injection as one of the promising techniques for P-HEXs’ performance, where a maximum specific net profit of 0.45 USD kJ −1 is estimated.

The stability of air bubbles is a critical factor in determining the performance of concrete. This study investigated the influence of various supplementary cementing materials (SCMs), with a 20% replacement of cement by weight, on the stability of foam in solutions and air bubbles in fresh mortars. Air bubble size distributions were measured using an air void analyzer and X-ray computed tomography at two intervals: from 5 to 60 min and from 60 to 180 min after the mixture was prepared. The results demonstrated that the number of small bubbles decreased while the number of large bubbles increased over time, with the most significant changes occurring within the initial 60 min. The results of the wettability tests were combined with those from the X-ray diffraction (XRD) analysis to identify a correlation between the stability of air bubbles and the wetting angle of the SCMs. It was observed that the contact angle of the SCMs approached 90° in cases where the air bubbles exhibited increased stability. The XRD patterns revealed significant differences in the mineral compositions between the bubble shells and the screened pastes from fresh mortar. The presence of a higher concentration of SCMs and hydration products on the bubble shells, compared to the paste, was identified as a potential reason for the observed differences in bubble stability. The utilization of specific SCMs has the potential to enhance bubble stability, in addition to the use of chemical admixtures.

The properties of honey are studied experimentally. It is shown that honey becomes less viscous as with an increase in its moisture content or temperature. Close results are obtained when measuring the surface tension coefficient of white honey using several methods: the drop weight method, the capillary rise method, and the air bubble detachment method. A formula is derived that allows one to estimate the dynamic viscosity of the fluid using the known surface tension coefficient and the known air bubble shape recovery rate in a fluid after the stretching the bubble twice its size at the same measurement temperature.

The rise of an air bubble enclosed in a magnetic fluid shell inside an external homogeneous magnetic field directed horizontally is investigated experimentally. It is shown that the magnetic field acting on the magnetic fluid shell alters the shape of the bubble, which is reflected in the quantitative characteristics of rising. Oscillations in the shape of the air bubble are observed as it rises. Results demonstrate the possibility of controlling small volumes of gas that can have practical applications.

Double pipe heat exchangers (DPHEs) are normally utilized in various manufacturing uses owing to their simple design and low maintenance requirements. For that, performance enhancement by improved heat transfer is ongoing. Air injections are a good strategy for enhancing the thermal performance of the DPHE. In the present work, the influence of air bubble injection in a DPHE was experimentally investigated, and the system’s hydrothermal performance improvement parameters were evaluated. Two modes were designed, manufactured, and used to conduct the experiments. The first mode was conducted with no air injection, named a single phase mode, while in the second mode, air was injected into the annulus of DPHE throughout different perforated rings on the side of the annular. Three different ring types were used and coded as R-1, R-2, and R-3, with an added case of insertion of the three rings inside the annulus. The airflow rate was fixed at 1.5 LPM with a 25°C inlet temperature. Also, the hot water rate in the inner pipe was maintained continuously at 3 LPM with a controlled 70°C temperature at the inlet. Five different cold water flow rates, 3, 3.5, 4, 4.5, and 5 LPM, in the annulus, were considered with a controlled inlet temperature at 17°C. Additionally, the effectiveness of the heat exchanger, the number of transfer units (NTU), and the overall heat transfer were predicted and considered for performance evaluation and comparison. The outcomes proved that the injection of air and the bubbly flow creation in the heat exchanger’s hot side is an effective method to strengthen the DPHE performance. Moreover, the total heat transfer coefficient was enhanced by 41% in R-1, 58.8% in R-2, and 40.1% in R-3 at 4 LPM of cold water. The optimal ring, which yielded the most improvement, was R-2, achieving a 65% improvement in NTU, with a maximum enhancement in effectiveness of 56%.

Ships sailing through cold regions frequently encounter floe ice fields. An air-bubble system that reduces friction between the hull and ice floes is thus considered useful for the reduction of ice-induced resistance. In this study, a numerical analysis procedure based on coupled finite volume method (FVM) and discrete element method (DEM) is proposed to simulate complicated hull-water-gas-ice interactions for ice-going ships installed with air-bubble systems. The simulations reveal that after turning on the air-bubble system ice floes in contact with the hull side wall are pushed away from the hull by the gas-water mixture, resulting in an ice-free zone close to the side hull. It is found that the drag reduction rate increases with the increase of ventilation, while the bow ventilation plays a deciding role in the overall ice-resistance reduction. The proposed procedure is expected to facilitate design of new generations of ice-going ships.

The flotation process allows particles and oil to separate from wastewater with high efficiency. Therefore, it is widely used in engineering and is a multidisciplinary field of study. In this study, a new generation flotation method is developed as an alternative to conventional flotation methods. Some experiments are conducted to determine the performance of this new system. It is known that the air-demand rate in the flotation process directly improves flotation performance. For this purpose, maximum aeration efficiency and bubble properties in the flotation cell supported by the newly developed head gated conduit are examined. A pilot-scale flotation system is installed for the experimental study. With the help of high resolution and high-speed cameras, parameters such as air bubble density, air bubble size, dead zone volume and penetration depth are determined. In addition, the images recorded during the flotation process are examined with professional image processing techniques. Experimental results showed that the Froude number, jet plunge angle and cell water levels have a significant impact on air-demand in the new system.

The most limiting aspect in liquid composite molding processes is the porosity issue. A successful manufacturing design depends mainly on the accurate prediction of the dynamics of air bubbles while processing composite structures. Especially, while simulating with a constant injection flow rate, where the part is supposed to exhibit a uniform porosity distribution according to the capillary number theory as proposed in the literature, it is not true in real practice. With this motivation, we present here a new approach, based on intra and intertow flows competition, to quantify the porosity of resin transfer molded composite parts. Combining the numerical modeling of the resin transfer molding (RTM) process based on the control volume finite element and volume of fluid methods on one hand, and the pore doublet model (PDM) on the other hand, air bubble contents at dual scale of pores are modeled in the case of constant pressure and constant injection flow rate. The results of the developed modeling permit a detailed spatiotemporal description of the created compressed and transported micro and macro air bubbles, besides fibrous fabric saturation. Consequently, taking into account the compression and transport phenomena, the porosity distribution is no longer uniform in the part, but higher in the downstream than in the upstream. Furthermore, the void transport phenomenon is also considered using the PDM concept. To validate the proposed approach, the numerical and experimental data are compared.

The authors study dynamics of heavy particle attached to the surface of free air bubble in liquid. The bubble with its surface vibrations and the particle are considered as a single mechanical system with geometric constraint. It is assumed that the main forces to govern interaction of these objects are the inertia force due to surface vibration of the bubble and the capillary adhesion force. The stability conditions of particle–bubble flotation aggregate at various initial surface vibrations of the bubble and at different masses of the particle are described. The velocities of the surface vibration modes are governed by the energy of turbulent pulsations in liquid.