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Mass transfer and phase transition have an important effect on the velocity of bubble migration in deepwater wellbores, and accurate prediction of bubble migration velocity is crucial for calculating the safe shut-in period of deepwater oil and gas wells. Therefore, the effect of bubble dissolution mass transfer and hydrate phase transition on bubble migration behavior in the deepwater environment have attracted extensive attention from researchers in the fields of energy, marine chemistry, and marine engineering safety. In this work, a new model of bubble migration velocity in deepwater is developed, which considers the effect of hydrate phase transition and gas-water bidirectional cross-shell mass transfer during bubble migration. Based on the observation data of bubble migration in deepwater, the reliability of the model in predicting bubble migration velocity is verified. Then, the model is used to calculate and analyze the bubble migration velocity and bubble migration cycle under different initial bubble size, different annular fluid viscosity, and density. The results show that the initial size of bubble and the viscosity of annulus fluid are the main factors affecting the migration velocity of the bubble, but the density of annulus fluid has little effect on the migration velocity of the hydrated bubble and clean bubble. In addition, the migration velocity of the clean bubble gradually increases during the migration process from the bottom to the wellhead, while the migration velocity of the hydrated bubble is divided into a gradually decreasing stage and a slowly increasing stage. The gas consumption and the thickening of hydrate shell in the gradually decreasing stage play a dominant role, and the increase of bubble volume caused by the decrease of pressure in the slowly increasing stage is the most important factor. The formation of the hydrated bubble can significantly reduce the migration velocity of the bubble and effectively prolong the safe shut-in period. This study provides a reference for quantitative description and characterization of complex bubble migration behavior with phase change and mass transfer in deepwater environment.

Abstract The stresses existing in power transformers lead to the generation of bubbles. They are the primary source that worsens and leads to insulation failure. Due to the complexity of bubble dynamics, it is challenging to figure out bubble mechanisms. However, creation, migration, and accumulation mechanisms require further explanation. A set of experiments has been conducted to provide a scientific overview of bubbles. The results revealed that buoyancy is dominant in low electric fields, while high electric fields affect bubbles' rise. Bubbles stretch and oscillate while moving. When the electric field is not strong, the AC field reduces the duration and volume of bubble detachment. Vibration stress on the other side is leading the bubble motion including detachment frequency and migration speed. Under the combination of AC and vibration stresses, the bubble distortion degree aggravates and bubble gathering formation is easy. This research can provide a deeper acumen of the bubble's actions beneath a power transformer under a combination of vibration and electric fields. It provides essential technique parameters to deal with while investigating bubble's problems and related engineering research areas.

The main objective of the study is to investigate the bubble migration between foreign exchange and housing markets in Iran using seasonal data of 1966-1396. In this regard, bubble dating is discovered by using of Phillips et al (2015) method; then, bubble migration from the foreign exchange market to the housing market and from the housing market to the foreign exchange market is examined, using the Gomez-Gonzales et al. (2016) method. The results show that there are 7 bubble periods in the foreign exchange market; and 7 bubble periods in the Housing market. four hypotheses were defined for examine the bubble migration, according to the bubble dates (from the foreign exchange to housing market and vice versa). The results of the hypothesis testes showed that the first house bubble (2007Q2-2008Q3) led to the creation of the first bubble of the foreign exchange market (2007Q4-2008Q3). It seems that in the currency restriction conditions, the probability of creating a foreign exchange bubble and its migration to the housing market is rather high and vice versa.

The main purpose of this study is to investigate the migration of bubbles from the oil market to the stock exchange. First, using the method of Phillips et al. (2015), bubbles were discovered and dated in the Iranian heavy oil market in the monthly period 1980-2020 and the Tehran Stock Exchange in the period 2008-2020. Then, using the method presented by Gomez-Gonzales et al. (2018), the migration of bubbles from the oil market to the Tehran Stock Exchange in the period 2020-2008 was investigated. The results showed that Iranian heavy oil has 9 bubble cycles in the period under study. Also, six bubbles were observed in the period under review for the Tehran Stock Exchange. The findings indicate the closeness of the ninth bubble in the oil market and the fourth bubble in the Tehran Stock Exchange. The hypothesis of bubble migration from the oil market to the Tehran Stock Exchange was tested in this period. The results of the hypothesis test indicate the acceptance of bubble migration from the oil market to the Tehran Stock Exchange.

The bubble migration in liquid titanium melt during vertical centrifugal casting process has been investigated by hydraulic experiments. Results show that the gas bubble in the simple cavity ultimately migrates like a line parallel to the wall in the opposite direction to the rotational casting mould. The deviation distance of the bubble in the simple geometry cavity tends to increase with the increment of the mould rotational speed during the migration process. And the gas bubble is much easier to migrate like a line when its initial position is nearer to the casting mould wall which is opposite to the mould rotational direction. The migration trajectories of bubbles located at different position in the complex cavity are more complicated than that in the simple cavity. The casting mould in the complex cavity can hamper both the radial movement and the circular movement of the bubble. And gas bubbles will gather, re-nucleate and form new bigger bubbles beside the casting mould wall. The re-formed gas bubbles in the complex cavity become bigger than which escape from bubble generation chamber.

In order to resist bubble loading, anisotropic composite materials are the development direction of the future. The objective of this paper was to experimentally investigate the hydrodynamic performance of anisotropic laminate composite plates, with a focus on the effect of its anisotropic characteristics on single bubble migration. In these experiments, the bubble was generated in a transparent water tank filled with sufficiently degassed water by Joule heating at the connecting point of the electrodes through the discharge of a 6600 μF charge to 800 V, and a high-speed camera system with a recording speed of 40,000 frames per second was used to record the temporal evolution of bubble patterns and the dynamic responses of the laminated composite plates. The results are presented for two anisotropic cantilever composite beams with different ply angles, namely, 0° and 30°. Several variables, such as the shapes of the bubble, the curved trail of motion of the bubble center, bubble collapse time, and bubble initial standoff distances were extracted from the photographic images. The results showed that bubble migration near the 30° plate presents a curved bubble trail with an evident tilted angle during the collapse and rebound stages, which is very different from bubbles that all move vertically above the 0° plate. Furthermore, a characterization method for bubble migration was proposed to quantitatively describe the curved bubble trails and the deformation of the composite beams in temporal and spatial scales. This method shows that the curved bubble trails near the 30° plate are closely related to the dynamic response of composite beams, with a focus on the bending-twisting coupling effect.

A dynamic shut-in procedure is commonly adopted after a kick incident in order to build up the wellbore pressure, obtain reservoir information, and thereby handle the gas kick. In deep-water scenarios, the hydrate growth behaviors have a significant effect on gas migration and interphase mass transfer, which has not been quantitatively analyzed during the well shut-in process. In this study, a comprehensive mechanistic model of wellbore dynamics is developed considering gas migration and phase transitions. The simulation results show that the wellbore pressure field can be built up in different trends during different well shut-in periods, governed by gas seepage from the reservoir and gas migration along the wellbore, respectively. Masking the migration of free gas, the phase transition phenomena have a significant influence on the wellbore dynamics and bottomhole pressure. This work adds further insights into quantitatively characterizing the hydrate growth behaviors and interphase mass transfer rules of gas bubbles during a dynamic well shut-in procedure.

Due to various engineering applications, spontaneous bubble movement on the heated surface has brought huge attention. This work numerically studied the bubble migration driven by the thermo-capillary force under the temperature gradients perpendicular to the gravity direction. This problem is constructed in a two-dimensional domain, and the volume of fluid (VOF) method is adopted to capture the properties of the bubble interface between the vapor and the liquid. One still vapor bubble is initially positioned at the center of the liquid domain, and the temperature gradient is applied to two side walls. The results show that the bubble with a size greater than the capillary length can only oscillate near the initial position even with a larger temperature gradient. The deformation of the bubble such as spheroid and spherical cap can be found around this regime. However, the movement of the bubble with a size smaller than the capillary length is significant under a higher temperature gradient, and it remains a spherical shape. The coefficient of thermo-capillary force (CTh) is defined within this work, and it is found that a larger Weber number (We) accomplishes a larger CTh. This work may provide more precise guidance for smart bubble manipulation and critical heat flux estimation for future nuclear reactor design.

The stresses existing in power transformers lead to the generation of bubbles. They are the primary source that worsens and leads to insulation failure. Due to the complexity of bubble dynamics, it is challenging to figure out bubble mechanisms. However, creation, migration, and accumulation mechanisms require further explanation. A set of experiments has been conducted to provide a scientific overview of bubbles. The results revealed that buoyancy is dominant in low electric fields, while high electric fields affect bubbles' rise. Bubbles stretch and oscillate while moving. When the electric field is not strong, the AC field reduces the duration and volume of bubble detachment. Vibration stress on the other side is leading the bubble motion including detachment frequency and migration speed. Under the combination of AC and vibration stresses, the bubble distortion degree aggravates and bubble gathering formation is easy. This research can provide a deeper acumen of the bubble's actions beneath a power transformer under a combination of vibration and electric fields. It provides essential technique parameters to deal with while investigating bubble's problems and related engineering research areas. [ABSTRACT FROM AUTHOR]

Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to resist bubble loading, anisotropic composite materials are the development direction of the future. The objective of this paper was to experimentally investigate the hydrodynamic performance of anisotropic laminate composite plates, with a focus on the effect of its anisotropic characteristics on single bubble migration. In these experiments, the bubble was generated in a transparent water tank filled with sufficiently degassed water by Joule heating at the connecting point of the electrodes through the discharge of a 6600 μF charge to 800 V, and a high-speed camera system with a recording speed of 40,000 frames per second was used to record the temporal evolution of bubble patterns and the dynamic responses of the laminated composite plates. The results are presented for two anisotropic cantilever composite beams with different ply angles, namely, 0° and 30°. Several variables, such as the shapes of the bubble, the curved trail of motion of the bubble center, bubble collapse time, and bubble initial standoff distances were extracted from the photographic images. The results showed that bubble migration near the 30° plate presents a curved bubble trail with an evident tilted angle during the collapse and rebound stages, which is very different from bubbles that all move vertically above the 0° plate. Furthermore, a characterization method for bubble migration was proposed to quantitatively describe the curved bubble trails and the deformation of the composite beams in temporal and spatial scales. This method shows that the curved bubble trails near the 30° plate are closely related to the dynamic response of composite beams, with a focus on the bending-twisting coupling effect.

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)