Bubble Type Research Articles

Non-Spherical Cavitation Bubbles: A Review

Cavitation is a phase-change phenomenon from the liquid to the gas phase due to an increased flow velocity. As it causes severe erosion and noise, it is harmful to hydraulic machinery such as pumps, valves, and screw propellers. However, it can be utilized for water treatment, in chemical reactors, and as a mechanical surface treatment, as radicals and impacts at the point of cavitation bubble collapse can be utilized. Mechanical surface treatment using cavitation impacts is called “cavitation peening”. Cavitation peening causes less pollution because it uses water to treat the mechanical surface. In addition, cavitation peening improves on traditional methods in terms of fatigue strength and the working life of parts in the automobile, aerospace, and medical fields. As cavitation bubbles are utilized in cavitation peening, the study of cavitation bubbles has significant value in improving this new technique. To achieve this, many numerical analyses combined with field experiments have been carried out to measure the stress caused by bubble collapse and rebound, especially when collapse occurs near a solid boundary. Understanding the mechanics of bubble collapse can help to avoid unnecessary surface damage, enabling more accurate surface preparation, and improving the stability of cavitation peening. The present study introduces three cavitation bubble types: single, cloud, and vortex cavitation bubbles. In addition, the critical parameters, governing equations, and high-speed camera images of these three cavitation bubble types are introduced to support a broader understanding of the collapse mechanism and characteristics of cavitation bubbles. Then, the results of the numerical and experimental analyses of non-spherical cavitation bubbles are summarized.

Exploring the impact of bubble type on sensory stimulation in drinks

This study explores the impact of various types of carbonation on sensory stimulation in the mouth, salivary secretion and the neurotransmitter substance P (SP), as well as body responses such as heart rate (HR) and Galvanic Skin Response (GSR). Three types of carbonation (one made using a soda machine, another carbonated with a gasifier, and the last commercial sparkling water) were used to produce different bubbles resulting in distinct sensory characteristics assessed by a trained panel. The impact of carbonation was measured by recording changes in salivary flow rate, SP levels, salivary secretory immunoglobulin A (SIgA), HR, and GSR in fifteen healthy participants. The results showed that the bubble type only affected the sensory perception of carbonation. Regardless of bubble type, carbonation increased salivary flow rate and SP values, SigA and HR. These characteristics are being sought to improve treatments for dysphagia or dry mouth. Therefore, these findings highlight the potential therapeutic application of carbonation in these situations.

Bitcoin’s bubbly behaviors: does it resemble other financial bubbles of the past?

A number of financial bubbles have occurred throughout history. The objective of this study was to identify the main similarities between Bitcoin price behavior during bubble periods and a number of historical bubbles. Once this had been carried out, we aimed to determine whether the solutions adopted in the past would be effective in the present to reduce investors’ risk in this digital asset. This study brings a new approach, as studies have previously been conducted analyzing the similarity of Bitcoin bubbles to other bubbles individually, but these were not conducted in such a broad manner, addressing different types of bubbles, and over such a broad time period. Starting from a dataset with 9967 records, a combined methodology was used. This consisted of an analysis of the standard deviations, the growth rates of the prices of the assets involved, the percentage increase in asset prices from the origin of the bubble to its peak and its fundamental value, and, finally, the bubble index. Lastly, correlation statistical analysis was performed. The results obtained from the combination of the above methods reveal the existence of certain similarities between the Bitcoin bubbles (2011, 2013, 2017, and 2021) and the tulip bubble (1634–1637) and the Mississippi bubble (1719–1720). We find that the vast majority of the measures taken to avoid past bubbles will not be effective now; this is due to the digital and decentralized nature of Bitcoin. A limitation of the study is the difficulty in making a comparison between bubbles that occurred at different historical points in time. However, the results obtained shed light and provide guidance on the actions to be taken by regulators to ensure the protection of investors in this digital asset.

Investigation of damage in vascular endothelial cells caused by lipid bubbles under ultrasound irradiation to verify the protective effect on cells

We investigated the viability of vascular endothelial cells engrafted on the basement membrane of a flow channel to verify the protective effect from cell damage under ultrasound exposure with a frequency of 3 MHz and a maximum sound pressure of 400 kPa-pp. We used two types of lipid bubbles (LBs), namely LBs (+) attached to the cells and LBs (–) not attached to the cells. We confirmed that the engrafted cells on the basement remained after ultrasound exposure and were resistant to flow. We found significant cell damage using LBs (–) regardless of the flow condition, whereas cell damage was not observed with LBs (+). A difference in irradiation direction of ultrasound was not detected. By making use of the adhesion of LBs (+) on the cells, since there was a significant increase in cell survival rate, we prove the potential for the adhesion of LBs (+) to protect cells from cell damage.

Stock market bubbles and the realized volatility of oil price returns

Using monthly data for the G7 countries from 1973 to 2020, we study whether stock market bubbles help to forecast out-of-sample the realized volatility of oil price returns. We use the Multi-Scale Log-Periodic Power Law Singularity Confidence Indicator (MS-LPPLS-CI) approach to identify both positive and negative bubbles in the short-, medium, and long-term. First, we successfully detect major crashes and rallies using the MS-LPPLS-CIs. Having established the relevance of the bubbles indicators, and given the large number of them, we use widely-studied shrinkage (Lasso, elastic net, ridge regression) approaches to estimate our forecasting models. We find that stock market bubbles have predictive value for realized volatility at a short to intermediate forecast horizon. The number of bubble predictors included in the penalized forecasting models tend to increase in the forecast horizon. We obtain our main finding for the various types of stock market bubbles, and for good and bad realized volatilities.

Monitoring underwater volcano degassing using fiber-optic sensing

Continuous monitoring of volcanic gas emissions is crucial for understanding volcanic activity and potential eruptions. However, emissions of volcanic gases underwater are infrequently studied or quantified. This study explores the potential of Distributed Acoustic Sensing (DAS) technology to monitor underwater volcanic degassing. DAS converts fiber-optic cables into high-resolution vibration recording arrays, providing measurements at unprecedented spatio-temporal resolution. We conducted an experiment at Laacher See volcano in Germany, immersing a fiber-optic cable in the lake and interrogating it with a DAS system. We detected and analyzed numerous acoustic signals that we associated with bubble emissions in different lake areas. Three types of text-book bubbles exhibiting characteristic waveforms are all found from our detections, indicating different nucleation processes and bubble sizes. Using clustering algorithms, we classified bubble events into four distinct clusters based on their temporal and spectral characteristics. The temporal distribution of the events provided insights into the evolution of gas seepage patterns. This technology has the potential to revolutionize underwater degassing monitoring and provide valuable information for studying volcanic processes and estimating gas emissions. Furthermore, DAS can be applied to other applications, such as monitoring underwater carbon capture and storage operations or methane leaks associated with climate change.

Optimized Kalinnikov-Dinh technology for effective pre-Descemet's endothelial keratoplasty (PDEK) graft preparation and preservation.

We report an optimized Kalinnikov-Dinh technology for pre-Descemet's endothelial keratoplasty (PDEK) that involves the use of a ring fixator, base, 30G needle connected to a 5-ml syringe with a spring-loaded plunger, and storage media. Our method allows to minimize graft preparation failure and preserves the PDEK graft efficiently, by reducing complications associated with the formation of type 1 big bubbles, including bubble rupture, perforation of Descemet's membrane and endothelium, and formation of type 2 or mixed type of big bubbles, and may contribute to increasing the number of surgeons performing PDEK around the globe.

Optimal monetary policy responses to carbon and green bubbles:A two-sector DSGE analysis

This paper investigates the emergence of carbon and green bubbles and their impacts on macroeconomic performance and the environment, with a particular focus on identifying the optimal monetary policy responses. We construct a two-sector dynamic stochastic general equilibrium (DSGE) model that incorporates monetary policy and allows carbon and green rational bubbles to emerge. We find that while supply-side shocks drive bubble formation in both sectors, demand-side shocks have a disproportionate impact on these sectors. The paper also shows that contractionary monetary policies are effective in reducing both carbon emissions and asset bubbles. Optimal monetary policy response to the emergence of asset bubbles is calculated, emphasizing the crucial role of central banks in designing monetary policy rules that account for the emergence of bubbles. Social welfare can be optimized by reducing annual interest rates by 0.0612% and 0.0512% when green and brown bubble sizes increase by 1%, respectively. Furthermore, the most effective strategy to achieve a significant improvement in social welfare in both the short-run and the long-run is to implement policies where nominal interest rates react negatively to both types of asset bubbles simultaneously. The impacts of carbon taxation and green credit policies on asset bubbles are also studied.

Industrial wastewater treatment using venture injector type Micro-bubble aeration as a reduction of dissolved Iron (Fe2+) levels

Water quality problems that are often encountered, especially by-product wastewater resulting from industrial processes that do not meet the requirements for wastewater quality standards. Iron levels in wastewater can cause the water to turn brownish yellow and produce an unpleasant odor, which of course has a big impact on the environment. Therefore, it is necessary to implement a treatment process to reduce the iron level in the water, ensuring that the water is safe when discharged into the environment. The purpose of this research is to analyze the initial parameters of temperature, pH, TDS, TSS, dissolved oxygen (DO) and dissolved iron (Fe2+) in industrial waste water and then wanted to know whether the venture injector type micro bubble aeration process was able to increase the value of dissolved oxygen (DO) and decrease the dissolved iron content (Fe2+) in wastewater and to know the micro bubble type aeration process Venture injectors are the best to use. The research was conducted with an experimental design using a completely randomized design (RAL) with two factors: air flow (2 LPM, 4 LPM, and 6 LPM) and aeration time (0 minutes, 15 minutes, 30 minutes, 45 minutes, and 60 minutes), each with two repetitions. In the results of the initial parameter analysis, the pH value was 8.02 (alkaline), the temperature value was 28°C, the TDS value was 1548.3 mg/L, the TSS value was 291 mg/L, the DO value was 0.1 mg/L and dissolved iron (Fe2+) of 7.453 mg/L. After conducting research, it was found that the venture injector type micro bubble aeration process was able to increase the value of dissolved oxygen (DO) and reduce dissolved iron (Fe2+) in industrial waste water, the best increase in dissolved oxygen (DO) at 6 LPM air flow for 60 minutes was able to increase oxygen dissolved (DO) to 2.40 mg/L. The most efficient and effective reduction in the value of dissolved iron (Fe2+) at 6 LPM air flow with a time of 15 minutes was able to reduce the value of dissolved iron by 84.42%.

A Wall Effects and Means of Controlling the Evolution of Swirling Flows with Vortex Breakdown

This paper investigates numerically the bubble-type vortex breakdown apparition in the case of closed rotating flows of a viscous, axisymmetric, and incompressible fluid. First, a truncated conical/cylindrical cavity of spherical end disks is used to simulate and analyze the vortex structure under rigid surface conditions. The geometric effects of the enclosure are also studied. Vortex breakdown is demonstrated beyond the lower disk rotation rate threshold by introducing the no-slip condition imposed on the upper wall. The objective is to explore ways of controlling the evolution of this physical event by modifying the confinement conditions upstream of the vortex rupture. Particular attention is also paid to the effective kinematic viscosity, thermal diffusivity and geometric control of recirculation zones on the axis of rotation (axial bubble type). The second geometry consists of a spherical annulus formed by two concentric hemispheres in differential rotation under plat-free surface conditions. The results show that rotation of the inner hemisphere induces a vortex bubble on the polar axis. In contrast, the outer hemisphere rotation induces a toroidal vortex on the equator.

Atomistic insight into the shock-induced bubble collapse in water

Atomistic simulations are employed to investigate the dynamics of shock-induced bubble collapse in water. Two types of bubbles (an empty bubble and a bubble filled with N2 gas) in water are considered in this study. Apart from the manifestation of a rise in temperature and pressure due to implosion energy released upon bubble collapse; distinct differences in response could be observed for the case of empty bubble to that of the case of the bubble with N2 gas. It is observed that the mechanism of the bubble associated with bubble dissociation as well as the time taken for collapse are changed with the introduction of N2 gas within the bubble. Numerous new chemical species are also observed as the N2 within the bubble reacts with water molecules upon shock compression which can be correlated with the differences in observation between an empty bubble system and a system containing N2 gas. This study is anticipated to lead to further improvements in continuum theories for cavitation bubble collapse in which the effects of chemical reactions need to be incorporated.

A New Type of Oxidation Air Bubble Breaking and Detention Device with Wing Span Baffle Structure Numerical simulation research

Taking the limestone gypsum wet desulfurization oxidation air duct of a 660 MW coal-fired unit in a power generation enterprise as the research object, a new type of oxidation air bubble crushing and retention device with a wing span baffle structure was simulated and optimized using CFD numerical simulation technology. The results showed that the retention time of bubbles in the slurry in the final design scheme was about 10.4 seconds, significantly better than the initial scheme’s 8.5 seconds and the comparison scheme 1’s 6.5 seconds. The new oxidation air bubble crushing and retention device significantly increases the retention time of oxidation air bubbles in the slurry, reduces the size of oxidation air bubbles, and improves the distribution uniformity of oxidation air in the slurry pool.

Observation of hybrid magnetic skyrmion bubbles in Fe3Sn2 nanodisks

It has been widely established that there exist two types of magnetic bubbles. Here, the authors present the theory and experiment of a novel three-dimensional bubble state, referred to as the type-III bubble, which is composed of N\'eel-twisted skyrmions with topological charge $Q$ = -1 in the near-surface layers and type-II bubbles with $Q$ = 0 in the interior layers. Furthermore, the authors demonstrate a method for creating the type-III bubble and the topological magnetic transformation among the three types of bubbles.

A New Immersed Finite Element Method for Two-Phase Stokes Problems Having Discontinuous Pressure

Abstract In this paper, we develop a new immersed finite element method (IFEM) for two-phase incompressible Stokes flows. We allow the interface to cut the finite elements. On the noninterface element, the standard Crouzeix–Raviart element and the P 0 {P_{0}} element pair is used. On the interface element, the basis functions developed for scalar interface problems (Kwak et al., An analysis of a broken P 1 {P_{1}} -nonconforming finite element method for interface problems, SIAM J. Numer. Anal. (2010)) are modified in such a way that the coupling between the velocity and pressure variable is different. There are two kinds of basis functions. The first kind of basis satisfies the Laplace–Young condition under the assumption of the continuity of the pressure variable. In the second kind, the velocity is of bubble type and is coupled with the discontinuous pressure, still satisfying the Laplace–Young condition. We remark that in the second kind the pressure variable has two degrees of freedom on each interface element. Therefore, our methods can handle the discontinuous pressure case. Numerical results including the case of the discontinuous pressure variable are provided. We see optimal convergence orders for all examples.

Developing an in vitro elicitation strategy for specialized secondary metabolites production in adventitious root cultures of Primula veris subsp. veris

The demand for new sources of bioactive plant secondary metabolites (SMs) with importance as pharmaceutical and food additives, cosmetics and flavors, have emerged as rising scientific topic in parallel to the protection of natural habitats due to overexploitation and decreasing of biodiversity. Cowslip (Primula veris L. subsp. veris) is a perennial medicinal plant in which pharmaceutically important SMs such as phenolic acids glycosides (primulaverin, primeverin) and triterpene saponins (primulic acid I and II) are produced in the roots and aerial parts. These metabolites serve as quality markers for the evaluation of raw materials used for the production of expectorant and diuretic drugs. Alternatively to traditional soil-cultivation of whole plants, in vitro adventitious root production systems have the potential for elevated and stable production of plant SMs through elicitation processes. Additionally, these systems have an advantageous perspective from ecological and economical aspect comparing with conventional method for mass production of valuable compounds. In the present study eight abiotic elicitors [salicylic acid (SA), cazeine hydrolysate (CH), L-proline, silver nitrate (AgNO3), cobalt chloride (CoCl2), sucrose, jasmonic acid (JA) and putrescine], under a 60-day culture period into 250 mL flasks were tested. Afterwards, the following three elicitors applied in single (100 mg/L CH, 100 mg/L L-proline, 25 μM JA) or combinations (JA + CH, JA + L-proline), under two exposure times (30 and 60 days). The results showed that primeverin [35.7 mg/g dry weight (DW)], and cumulative phenolic acids glycosides (52.9 mg/g) content, yield index (YI) of primeverin (97.4 mg of pure dry extract), cumulative phenolic acids glycosides (144.4 mg), primulic acid I (37.2 mg), primulic acid II (9.1 mg) and cumulative saponins (45.4 mg), as well as root fresh biomass growth rate (× 10.2-fold), and root DW (2.7 g) were promoted after elicitation with 100 mg/L L-proline for 60 days. Primulaverin (23.6 mg/g), primeverin (14.4 mg/g) and the cumulative phenolic acids glycosides (38.1 mg/g) content was considerably maximized after treatment with 25 μM JA for 30 days. Combined elicitation of roots with 25 μM JA + 100 mg/L L-proline for 30 days, indicated the highest content in primulic acid II (5.9 mg/g), cumulative saponins (22 mg/g), while primulic acid I represented the highest content under 100 μM JA for 60 days (27 mg/g). Among the eight elicitors tested, L-proline, JA, and L-proline + JA proved to be the most beneficial treatments for SMs production. Following that, root fresh biomass growth rate (× 8.1), content, and YI of primulaverin (14.3 mg/g, 149.1 mg), primeverin (0.3 mg/g, 3.2 mg), cumulative phenolic acids glycosides (14.6 mg/g, 152.3 mg), primulic acid I (10.3 mg/g, 93.3 mg), primulic acid II (2.5 mg/g, 19.2 mg), and cumulative saponins (12.8 mg/g, 112.5 mg) were considerably higher after 90 days of culture in a 2 L balloon bubble type bioreactor system than after 60 days. Elicitor type, elicitor concentration, and elicitation exposure duration are factors that play a key role in the production of SMs. In the present study, the importance of abiotic elicitation strategies, and bioreactor systems which are novel in the scale-up process, on adventitious root in vitro cultures of P. veris subsp. veris have been discussed in detail and are highlighted for the first time. The production systems applied herein lay the possibilities for the large-scale manufacturing of specialized plant-derived SMs including triterpene saponins and phenolic acid glycosides, presenting commercial applications due to higher root biomass and bioactive compounds productivity obtained.

Experimental Study on the Effects of New Foam on the Improvement of Sandy Soil for Earth Pressure Balance Shield

In this paper, starting from the foaming amount, half-life and other indicators, the surfactant with excellent performance is optimized, and the optimal compound ratio and appropriate foam stabilizer, viscosity enhancer, and additives are studied. A new type of foam agent formula for the EPB shield is developed. The performance of the new foam agent is compared with that of domestic foam and imported foam from the aspects of foaming rate, stability, micromorphology and temperature resistance, which verifies that it meets the parameter requirements and advantages of a foam agent for shield tunneling. Then, by means of laboratory tests, such as the mixing test, friction coefficient test, adhesion resistance test, slump test and direct shear test, the improvement effect of the new foam agent is compared with existing foam agent products at home and abroad, and the improvement effect of the new foam agent on soil is evaluated. The formulation of the new foam agent is as follows: 1.6% sodium dodecyl sulfate (SDS) + 8% dodecyl dimethyl betaine (BS-12) + 7% dodecanol + 0.06% guar gum + 0.6% ammonium chloride. The foaming rate, stability, microstructure and temperature resistance of new foam meet the requirements of shield construction. New foam, imported foam and domestic foam have advantages in sand and soil improvement experiments, but from an economic point of view, the new type of bubble is better than the other two. A new type of shield foam agent is prepared to meet the needs of construction. There is a big advantage in terms of price.

Numerical simulation of the interaction and coalescence of inline hydrogen bubbles in biohydrogen production by photofermentation with corncob

The escape rate of hydrogen in photobiological hydrogen production plays an important role in the biochemical reaction process, and the interaction of hydrogen bubbles in bio-hydrogen production material liquid affects the escape rate of hydrogen. In this paper, the Eulerian-Eulerian-Multifluid VOF method is used to simulate the interactions of three types of hydrogen bubbles: coalescence of equal-sized inline hydrogen bubbles, a small leading hydrogen bubble is chased by a large trailing hydrogen bubble and a large leading hydrogen bubble is chased by a small trailing hydrogen bubble. The results show that the interaction strength between hydrogen bubbles is influenced by the initial interval and initial diameter of the hydrogen bubbles and the flow index of the hydrogen-producing material liquid. The hydrogen bubbles exhibit three types of aggregation. In the pre-merger period, the velocity of the trailing hydrogen bubble also shows four stage changes, which are acceleration to the maximum velocity - deceleration - small increase in velocity - deceleration to the merging velocity. There is also a brief acceleration of the leading hydrogen bubble. For the interaction between Type II and Type III hydrogen bubbles of the same size, there is no significant difference in the rise rate of large hydrogen bubbles after the coalescence.

Characteristics of geometry-and pressure-induced laminar separation bubbles at an enhanced level of free-stream turbulence

Responses of a geometry-induced separation bubble (GISB) and a pressure-induced separation bubble (PISB) at enhanced levels of free-stream turbulence (FST) have experimentally been investigated for a comparative study using the particle image velocimetry (PIV) technique. The outlines of separation bubbles based on the dividing streamlines are self-similar for different levels of FST and Reynolds numbers. The spectral analyses of the time-resolved PIV data show that the vortex shedding frequency of a separated shear layer remains unchanged for the GISB cases even with an enhanced level of FST. In contrast, it is different for the PISB cases. We propose a criterion that determines whether the frequency will remain the same even for the cases with FST. Linear stability analyses reveal that the inviscid-inflectional instability dominates the transition process, and the linear stages of transition are not completely bypassed even at an enhanced level of FST. The most amplified frequencies, while scaling with the displacement thickness and the boundary layer edge velocity, collapse in a single curve for all the cases. Furthermore, measurements in the spanwise plane show that the streamwise velocity streak/Klebanof mode at an enhanced level of FST is not a general flow feature for all types of separation bubbles. However, at an enhanced level of FST for the PISB case, the boundary layer streaks are found to distort the two-dimensional vortex structure associated with the Kelvin–Helmholtz instability, eventually leading to a three-dimensional $\varLambda$ -like structure in the spanwise plane.

함정의 평판형 방향타 캐비테이션 침식에 대한 모형 시험 연구

In the present study, a method of performing cavitation erosion test directly on the anodized surface of the rudder model is proposed, not applying ink or paint on its surface. An image processing technique is newly developed to quantitatively evaluate the erosion damages on the rudder model surface after erosion test. The preprocessing saturation image, image smoothing, adaptive hysteresis thresholding and eroded area detection algorithms are in the image processing program. The rudder cavitation erosion tests are conducted in the rudder deflection angle range of 0SUPo/SUP to -4SUPo/SUP, which is used to maintain a straight course at the highest speed of the targeted navy ship. In the case of the conventional flat-type full-spade rudder currently being used in the target ship, surface erosion can occur on the model rudder surface in the above rudder deflection angle range. The bubble type of cavitation occurs on rudder surface, which is estimated to be the main reason of erosion damage on the rudder surface.

Evolution of tornado-like vortices in three-dimensional compressible rectangular cavity flows

The spatial structure and time evolution of tornado-like vortices in a three-dimensional cavity are studied by topological analysis and numerical simulation. The topology theory of the unsteady vortex in the rectangular coordinate system (Zhang, Zhang & Shu, J. Fluid Mech., vol. 639, 2009, pp. 343–372) is generalized to the curvilinear coordinate system. Two functions $\lambda (q_1,t)$ and $q(q_1,t)$ are obtained to determine the topology structure of the sectional streamline pattern in the cross-section perpendicular to the vortex axis and the meridional plane, respectively. The spiral direction of the sectional streamlines in the cross-section perpendicular to the vortex axis depends on the sign of $\lambda (q_1,t)$ . The types of critical points in the meridional plane depend on the sign of $q(q_1,t)$ . The relation between the critical points of the streamline pattern in the meridional plane and that in the cross-section perpendicular to the vortex axis is set up. The flow in a three-dimensional rectangular cavity is numerically simulated by solving the three-dimensional Navier–Stokes equations using high-order numerical methods. The spatial structures and the time evolutions of the tornado-like vortices in the cavity are analysed with our topology theory. Both the bubble type and spiral type of vortex breakdown are observed. They have a close relationship with the vortex structure in the cross-section perpendicular to the vortex axis. The bubble-type breakdown has a conical core and the core is non-axisymmetric in the sense of topology. A criterion for the bubble type and the spiral type based on the spatial structure characteristic of the two breakdown types is provided.