Gas Core Research Articles

Leather dyeing using a new liposome-based process assisted by dense gas technology

Liposomes are spherical vesicles characterized by a double lipidic layer surrounding an inner aqueous core; they have been employed in several fields, such as pharmaceutical, cosmetic and nutraceutical. In this work another possible application is explored: the deposition of dyes on sheep leather is attempted, using liposomes as dye vehicles to obtain a better adhesion of dye on leather surface. A supercritical assisted method called SuperLip is proposed to load red aniline into liposomes, for leather coloration. Process parameters have been optimized such as dye and lipid concentration in the system, water flow rate for vesicles inner core production and Gas to Liquid Ratio of the Expanded Liquid to control size and particles distributions.Nanometric liposomes of about 150 nm diameter have been obtained, with a red aniline Encapsulation Efficiency (EE) of about 75%; micrometric vesicles of about 2 μm were also produced with EE up to 82%, in order to provide large dimensions for covering macroscopic surfaces. A conventional dyeing method and the new liposomal method were compared in terms of deposition time, and color resistance. Liposomes, produced in this work, speeded up dye deposition from 60 min to 30 min, and resulted in a higher resistance to heat exposure; indeed, a discoloration down to 2.3% was observed using the proposed method and 25.1% using conventional method.

Non-adiabatic annular flow experiments in a subchannel geometry with spacer grid

Boiling annular flow in a subchannel geometry with functional spacers is studied using X-Ray tomography in the Dryout Tomography Experiment (DoToX) facility at ETH Zürich. The liquid film distribution on the walls and the liquid holdup within the gas core of the annular flow in the subchannel, both under the influence of the spacer vanes, are extracted from tomographic images. The subchannel cross section consists of a main subchannel in the center surrounded by four heating flow sections representing fuel rods and connected to four partial subchannels with simplified geometry. This effectively removes unnatural no-slip boundary conditions at the narrow gap of the main subchannel.Chloroform is used as a working fluid because of its low enthalpy of evaporation and a low boiling point around 60 °C close to atmospheric pressure. A liquid heating system with water at slightly above 100 °C provides the heating power for the boiling process. This ensures continuous operation of the facility even in case of a dryout scenario, avoiding structural damages by imposing a maximum system temperature. The high thermal capacity of the water allows for an almost isothermal boundary condition. Although not identical to real BWR settings, this experiment is well suited to generate data for model validation.Originally designed for tomographic imaging with both cold neutrons and X-rays, this paper focuses on results obtained by X-rays. Since the X-ray contrast between the working fluid chloroform and the structural material of the channel, aluminum, is very small, differential imaging with adaptive centering of reconstructions with and without the liquid film were required. The measurement campaign consisted of three measurements with constant chloroform mass flows at 5.00, 4.05 and 3.25 kg/min and constant heating liquid temperature of 100–104 °C, in addition to the empty channel reference measurement. The thermal power transferred to the working fluid under these conditions was about 10 kW of heating power. The resulting liquid film thicknesses (LFT) upstream of the spacer decreased from 91 to 49 µm. The effect of the spacer vanes is visualized and quantified over an axial section of 10 hydraulic diameters. Reference samples of the film thickness and the liquid holdup were taken upstream of the spacer. Dryout was nearly reached in characteristic regions of reduced film thickness due to turbulent shear stresses, while other regions show a significant local increase of the liquid film thickness. The deposition of about 30% of the liquid holdup from the gas core contributes to the increase. The results are consistent with previous adiabatic experiments with similar geometries.

Multiscale Market Integration and Nonlinear Granger Causality between Natural Gas Futures and Physical Markets

This paper comprehensively analyzed the price integration of the U.S. natural gas futures market and its physical markets. The analyses were conducted in the form of graphics using the ensemble empirical mode decomposition (EEMD) method and minimum spanning trees with various horizons. Our findings indicated that the network structures of the minimum spanning trees of the gas futures and physical markets are the same on different time scales. The citygate returns were always the core of the physical gas markets. In addition, the gas futures and physical markets were highly integrated on different time scales. Moreover, our findings showed that at the original data level, unidirectional linear and nonlinear causalities from gas futures to physical returns exist. Specifically, the relationships between futures and physical gas returns were not constant across various time scales. In the long term, futures gas returns had only a linear causality with the citygate, commercial, and industry gas returns, and a unidirectional, nonlinear causality with residential gas returns.

Experimental study on flow patterns and transition criteria for vertical swirling gas-liquid flow

Swirling gas-liquid flow has a wide variety of engineering applications in petroleum, chemical, and nuclear industries. A fundamental understanding of swirling flow patterns and their transitions is essential for the proper modelling of pressure drop, mass transfer rate and interfacial area in swirling two-phase flow. Although the gas-liquid flows in straight pipes have been widely studied, little attention has been paid to characteristics at transition boundary of swirling gas-liquid flow. In this paper, based on high-speed camera method using back light source, flow patterns and transition criteria for swirling gas-liquid flow induced by a vane-type swirler were experimentally investigated in a vertical tube of 30 mm I.D., operating at ambient temperature and pressure. According to our observation, five typical flow patterns, i.e. swirling gas column flow, swirling intermittent flow, swirling annular flow, slug flow and churn flow, were identified and the detailed characteristics at the transition boundaries were discussed with flow-regime reconstruction technique. The spatial and temporal evolution of the gas core diameter in swirling flow regimes were also analyzed using image processing technique. Additionally, the flow-regime transition criteria were gained which reveal that the void fraction αg in swirling gas column flow is below 0.30∼0.32 and it attains values of 0.32 to 0.71 in the swirling intermittent flow. When αg is greater than 0.71∼0.74, the swirling intermittent flow transforms into swirling annular flow.

Response of chemically crosslinked microbubble clusters in an ultrasound field

The purpose of this study is to introduce a new concept of chemically cross-linked microbubble clusters (CCMCs), demonstrate a facile means of their production, and describe how they can potentially be used in biomedical applications. Currently, ultrasound contrast agents (UCAs- also known as microbubbles) are thought of as single gas bubbles stabilized by a biocompatible shell with sizes ranging from 1–10 μm. By tethering UCAs together into CCMCs, we propose that novel methods of ultrasound-mediated imaging and therapy can be developed through unique inter-bubble interactions in an ultrasound field. One of the major challenges in generating CCMCs is maintaining stability to Ostwald Ripening and coalescence. In this study, we demonstrate that chemically cross-linked microbubble clusters can produce small (<10 μm) quasi-stable complexes that slowly fuse into bubbles with individual gas cores. Furthermore, we demonstrate that this process can be driven with low-intensity ultrasound pulses, enabling a rapid fusion of clusters which could potentially be used to generate novel acoustics. The development of novel microbubble clusters here presents a simple yet robust process for generating novel UCAs with a design that could allow for more versatility in contrast-enhanced ultrasound (CEUS), molecular imaging, and drug delivery applications.The purpose of this study is to introduce a new concept of chemically cross-linked microbubble clusters (CCMCs), demonstrate a facile means of their production, and describe how they can potentially be used in biomedical applications. Currently, ultrasound contrast agents (UCAs- also known as microbubbles) are thought of as single gas bubbles stabilized by a biocompatible shell with sizes ranging from 1–10 μm. By tethering UCAs together into CCMCs, we propose that novel methods of ultrasound-mediated imaging and therapy can be developed through unique inter-bubble interactions in an ultrasound field. One of the major challenges in generating CCMCs is maintaining stability to Ostwald Ripening and coalescence. In this study, we demonstrate that chemically cross-linked microbubble clusters can produce small (<10 μm) quasi-stable complexes that slowly fuse into bubbles with individual gas cores. Furthermore, we demonstrate that this process can be driven with low-intensity ultrasound pulses, enabling a rapi...

Modeling lipid-encapsulated microbubbles using transient network theory

Encapsulated microbubbles (EMBs) are widely used to enhance contrast in ultrasound sonography and are finding increasing use in biomedical therapies such as drug/gene delivery and tissue ablation. EMBs consist of a gas core surrounded by a stabilizing shell made of various materials, including polymers, lipids, and proteins. Lipid-coated EMBs present a unique challenge for modeling due to their relatively large oscillations and nonlinear, viscoelastic properties. We propose a novel model for a lipid-coated, spherical EMB that utilizes a statistically based continuum theory based on transient networks to simulate the encapsulating material. The use of transient network theory permits the viscoelastic properties of the encapsulation—such as stress, elastic energy and entropy—to be calculated locally based on the configuration of lipid molecules. The model requires a minimum number of parameters that include the lipid concentration, and the rates of attachment and detachment of lipids to and from the network. The model closely reproduces the experimentally measured radial response of an ultrasonically driven, lipid-coated microbubble. The model also reproduces experimentally observed nonlinear behavior, such as compression and expansion-dominated oscillations. Furthermore, the model can be readily extended to large nonspherical EMB deformations, which are important in many biomedical applications.

Influence of leakage of air hole on flow and heat transfer in recuperator

ABSTRACT In this article, three-dimensional periodic numerical model for fully developed flow in a cross wavy primary surface recuperator for a micro-gas turbine system is built. Influence of leakage of air hole on flow and heat transfer of high temperature gas core and compressed air core was analyzed. The results of analysis show that with leakage of air hole considered, flow velocity of compressed air from air hole flowing into gas core is far greater than that of high temperature gas. In addition, the flow is opposite to each other. As a result, the flow resistance in gas channel increases. With leakage of air hole considered, heat convection between gas core and air core weakens. When the diameter of air hole increases by 50 μm, maximum temperature in gas core increases by 1 K in a period. The performance of heat recovery for regenerator is degraded. Thermal ratio decreases with the improvement the diameter of air hole. When the diameter of air hole increases by 50 μm, thermal ratio decreases by about 0.3%. The flow in the gas and air channel is anti-symmetry along the center of channel. The flow of fluid is fluctuant. The flow velocity of gas is much larger than that of air. The research results can be used to guide checking the performance of a recuperator.

Wave characteristics of vertical upward adiabatic annular flow in pipes

Annular flow exists in many engineering applications, such as refrigerators, oil extraction, nuclear reactors and so on, due to its high heat and mass transfer efficiencies. Annular flow is characterized by liquid film on the wall and gas core at the center of the flow duct. The interface between the gas and liquid is composed of many different waves that play important role in mass, momentum and energy transfers between gas and liquid phases. Here three important parameters regarding wave characteristics, namely, wave velocity, base film thickness and wave height have been studied. For wave velocity, correlation has been proposed by two methods which are derived from liquid interfacial velocity and interfacial shear stress, respectively. For correlations of base film thickness and wave height, they are proposed in similar forms as that of average film thickness previously developed by the authors. These newly proposed correlations are functions of gas and liquid Weber numbers, and are simpler and more straightforward to use as compared to the existing ones. The newly proposed wave velocity, base film thickness and wave height correlations, respectively, have mean absolute percentage errors of 9.56%, 14.6% and 12.1% compared to current databases. They have shown an improved prediction accuracy compared to the other correlations in the literature.

Experimental investigation of air–water turbulent swirling flow of relevance to phase separation equipment

Single and two-phase turbulent swirling flow inside a circular pipe in the presence of a conical bluff body is studied using high speed photography and laser-Doppler velocimetry. The geometrical configuration is relevant to liquid–gas separating equipment. Several flow regimes were identified and, in particular, the results show the presence of a spiral axial flow for low values of gas–liquid ratio (GLR). High speed photographs indicated that the flow consists of a gas core surrounded by a liquid annulus and forms a liquid–gas interface corrugations of capillary nature. The tip of the gas core becomes unstable and ejects gas bubbles in a spiraling stream. The velocity measurements indicated an increase of turbulent fluctuations in the liquid layer in the vicinity of the interface. The liquid layer maintained a Rankine vortex, while a weak forced vortex was obtained for higher GLR.

Air-Core–Liquid-Ring (ACLR) Atomization Part II: Influence of Process Parameters on the Stability of Internal Liquid Film Thickness and Resulting Spray Droplet Sizes

Air-core–liquid-ring (ACLR) atomization presents a specific type of internal mixing pneumatic atomization. It can be used for disintegration of high viscous feed liquids into small droplets at relatively low gas consumptions. However, the specific principle of ACLR atomization is still under research and no guidelines for process and atomizer design are available. Regarding literature on pre-filming atomizers, it can be hypothesized for ACLR atomization that the liquid film thickness inside the exit orifice of the atomizer, as well as the resulting spray droplet sizes decrease with increasing air-to-liquid ratio (ALR) and decreasing feed viscosity. In this study, the time dependent liquid film thickness inside the exit orifice of the atomizer was predicted by means of computational fluid dynamics (CFD) analysis. Results were compared to high speed video images and correlated to measured spray droplet sizes. In conclusion, the hypothesis could be validated by simulation and experimental data, however, at high viscosity and low ALR, periodic gas core breakups were detected in optical measurements. These breakups could not be predicted in CFD simulations, as the simplification of an incompressible gas phase was applied in order to reduce computational costs and time. Nevertheless, the presented methods show good potential for improvement of atomizer geometry and process design as well as for further investigation of the ACLR atomization principle.

Sloshing of Galaxy Cluster Core Plasma in the Presence of Self-interacting Dark Matter

Abstract The “sloshing” of the cold gas in the cores of relaxed clusters of galaxies is a widespread phenomenon evidenced by the presence of spiral-shaped “cold fronts” in X-ray observations of these systems. In simulations, these flows of cold gas readily form via interactions of the cluster core with small subclusters, due to a separation of the cold gas from the dark matter (DM), due to their markedly different collisionalities. In this work, we use numerical simulations to investigate the effects of increasing the DM collisionality on sloshing cold fronts in a cool-core cluster. For clusters in isolation, the formation of a flat DM core via self-interactions results in modest adiabatic expansion and cooling of the core gas. In merger simulations, cold fronts form in the same manner as in previous simulations, but the flattened potential in the core region enables the gas to expand to larger radii in the initial stages. Upon infall, the subclusters DM mass decreases via collisions, reducing its influence on the core. Thus, the sloshing gas moves slower, inhibiting the growth of fluid instabilities relative to simulations where the DM cross section is zero. This also inhibits turbulent mixing and the increase in entropy that would otherwise result. For values of the cross section σ/m ≳ 1, subclusters do not survive as self-gravitating structures for more than two core passages. Additionally, separations between the peaks in the X-ray emissivity and thermal Sunyaev–Zeldovich effect signals during sloshing may place constraints on DM self-interactions.

Local liquid film behavior of annular two-phase flow on rod-bundle geometry – II. Modeling and verification

Local liquid film behavior of annular flow on rod bundle geometry is vital for accurate prediction of dryout. This paper is the Part II of a two-part study devoting to modelling and prediction of local liquid film behavior of annular flow on rod bundle geometry based on the unique feature of experimental phenomenon in Part I of this work. In this paper, a mechanism model is developed to predict the local liquid film thickness of annular two-phase flow on rod bundle geometry, in which the spatial distribution of gas flow in the cross-section of rod bundle is specified, and the local velocity of liquid film is obtained by employing the triangular relationship that taking into account properly the momentum and mass balances for the liquid film and the gas core. Ordinary differential equation (ODE) for the liquid film thickness is developed according to the Navier-Stokes equations for momentum balance of film flow on a rod to analyze the spatial characteristic of film thickness, in which the droplet entrainment-deposition process and the effect of circumferential shear stress are considered as boundary conditions during mass transfer at the gas-liquid interface. The present model predicts the experimental local liquid film thickness with the maximum relative error of ±10%. Circumferential coherent wave structure is formed by the combination effect of transversal stress gradient in the wave, droplet redeposition and film flow by circumferential shear stress, and the circumferential shear stress reduces the relative importance of the droplet redeposition with respect to the transversal stress gradient making the peripheral distribution of film thickness more uniform.

Unsteady CHT analysis of a solid state, sensible heat storage for PHES system

Purpose The aim of this study is to identify key factors limiting efficiency of pumped heat energy storage systems and determine some general features of transient behavior of solid state, sensible heat storages. Moreover, it aimed at establishing a feasible approach to transient conjugate heat transfer (CHT) analyses for such applications. Design/methodology/approach A zero-dimensional analytical model is used to determine the system efficiency sensitivity to efficiency of its components. Analysis of argon gas flow in an exemplary configuration of layered bed thermal energy storage is presented. The analysis incorporates a unsteady reynolds averaged navier stokes model with conjugate heat transfer between gas and solid storage core. Findings It is established that exergetic efficiency of the heat storage is one of the key factors for the system’s overall performance. Three full cycles of storage charging and discharging having 17 h physical time in total are simulated, with calculation of exergetic efficiency for each of the cycles. From standpoint of the system efficiency, it is concluded that the presented heat storage kind has limited exergetic efficiency because of severe temperature drop at the solid–fluid interface in comparison to granular kind of heat storage devices. From the methodological standpoint, it is concluded that calculating the exergetic efficiency of the heat storage by direct computational fluid dynamics (CFD) analysis requires significant amount of walltime and computational resources. Originality/value The paper presents unconventional approach to using standard CFD tools by exploiting numerical diffusion to numerically suppress high-frequency solution oscillations. This strategy grants that the analysis, otherwise requiring impractically long computation walltime, is completed within a practical time.

Origin of natural gases and associated gas hydrates in the Shenhu area, northern South China Sea: Results from the China gas hydrate drilling expeditions

Geochemical data for hydrate gases acquired from the GMGS3 and GMGS4 gas hydrate drilling expeditions conducted by the Guangzhou Marine Geological Survey (GMGS) are used to explore the origin of hydrate gases and their relationship to deep hydrocarbon reservoirs, and to evaluate the contribution of different genetic types of gases to the formation and accumulation of gas hydrates in the Shenhu area of the northern part of the South China Sea (SCS). Compositionally, methane is the dominant gas (>90%) in the void gas and pressure core gas. In addition, as much as ~3% of the gas is composed of C2+ hydrocarbons, including ethane, propane, iso-butane, butane, iso-pentane, and n-pentane. The δ13C-CH4 and δD-CH4 values indicate a mixed biogenic-thermogenic origin for the hydrate-forming gas. The methane isotope correlation indicates that the source of the hydrate gas is closely related to the deep conventional gas reservoirs discovered in the Baiyun Sag-Panyu Low Uplift area. Both the hydrate gases and the deep reservoir gases are sourced from the hydrocarbon kitchens in the Baiyun Sag, revealing a paragenetic relationship within the same petroleum system. The composition of the hydrocarbons and the isotopic variation of methane with depth suggest that the thermogenic gas was likely affected by compositional and isotopic fractionation during the long-distance migration from the deep source rocks to the shallow gas hydrate stability zone (GHSZ). The impact of biodegradation on a solely thermogenic gas could also affect the final composition of the hydrate-forming gas. Analysis of the GHSZ based on gas hydrate compositions suggests that the occurrence of thermogenic gas could also indicate the coexistence of structure I (SI) and structure II (SII) gas hydrates in the Shenhu area, with the SII hydrates accumulating in or below the lower part of the SI GHSZ. The confirmed presence of SII hydrates in the Shenhu area relocated the base of the GHSZ deeper than was indicated by the bottom simulating reflector, which warrants further study in future explorations for gas hydrates in the Shenhu area.

Time and frequency analysis of Vostok ice core climate data

The periodicity of Vostok ice core climate temperature and gas concentration data indicate inherent long term past regularity of Earth’s climate, with a period of around 100,000 years, warming around 15,000 and cooling of around 85,000 years. At this point we are at the top of one of the warming periods. Vostok data cover around 430,000 years, ie 4 climate cycles (warming-cooling), of similar but not quite the same duration. In this paper we perform a detailed time and frequency analysis of these data for each of the cycles as well as their various combinations, including a full tested period of 430,000 years. Time correlation analysis allows for more accurate time lag estimate in each cycle already noted between temperature change and carbon dioxide content. We estimate these lags to lie between 1000-2500 years, longer than previously concluded. On the frequency side we perform Fast Fourier Analysis and identify full spectrum of harmonics for various cycles, and then perform energy analysis to identify which of the harmonics contributes the most. The idea is to reduce the computational load for further modeling and analysis using Kalman Filter based prediction method. Once the prediction model is defined (a follow up paper) data will be split into two segments, Learning and Testing, in preparation of a Machine Learning fine tunning methodology. We can use last three or last two or even just last cycle to learn on, and then the current on going cycle to test on. This will result in real time prediction of relevant climate data. Assuming causal time regularity, more of these cycles are employed in training, more the prediction error for the next cycle should be reduced. Hence it is critical to perform very detailed time and frequency analysis of Vostok data as a solid data base for the prediction model to follow.

Expanding the Sample of Radio Minihalos in Galaxy Clusters

Radio minihalos are diffuse synchrotron sources of unknown origin found in the cool cores of some galaxy clusters. We use GMRT and VLA data to expand the sample of minihalos by reporting three new minihalo detections (A 2667, A 907 and PSZ1 G139.61+24.20) and confirming minihalos in five clusters (MACS J0159.8-0849, MACS J0329.6-0211, RXC J2129.6+0005, AS 780 and A 3444). With these new detections and confirmations, the sample now stands at 23, the largest sample to date. For consistency, we also reanalyze archival VLA 1.4 GHz observations of 7 known minihalos. We revisit possible correlations between the non-thermal emission and the thermal properties of their cluster hosts. Consistently with our earlier findings from a smaller sample, we find no strong relation between the minihalo radio luminosity and the total cluster mass. Instead, we find a strong positive correlation between the minihalo radio power and X-ray bolometric luminosity of the cool core (r<70 kpc). This supplements our earlier result that most if not all cool cores in massive clusters contain a minihalo. Comparison of radio and Chandra X-ray images indicates that the minihalo emission is typically confined by concentric sloshing cold fronts in the cores of most of our clusters, supporting the hypothesis that minihalos arise from electron reacceleration by turbulence caused by core gas sloshing. Taken together, our findings suggest that the origin of minihalos should be closely related to the properties of thermal plasma in cluster cool cores.

Prediction of hydrate deposition in pipelines to improve gas transportation efficiency and safety

The significant amounts of hydrocarbon resources (oil, natural gas, and gas hydrates) present in subsea and cold regions represent one of the most pre-dominant resources in the future. However, the deposition of gas hydrates in the transportation pipeline significantly decreases the efficiency and the safety of energy recovery. In this study, a novel model for forecasting hydrate deposition in gas transportation pipelines was established by considering the hydrates generated from the condensate water on the cold wall and the condensate drops in the gas core. By using the proposed model, the location and severity of hydrate deposition in pipelines can be quantitatively forecasted and analyzed. Compared with the existing methods, the average relative error between the calculated pressure drop and the experimental data was reduced from 34.98% to 7.43%, and the mean relative error between the calculated thickness of deposited hydrates and the experimental results was within 9.17%. The calculated results indicate that the deposited hydrates are unevenly distributed along the pipeline, and the deposition of hydrates formed from the condensate drops in the gas core is essential during the calculation of hydrate deposition in gas pipelines. The proposed model exhibits its good reliability for the water-saturated gas flow systems, but its applicability for the flow pattern with the existence of free water remains to be analyzed. Thus, the proposed model provides an effective support for the high-efficiency and high-safety development of hydrocarbon energy in subsea and cold regions.

Formulation and Characterization of Chemically Cross-linked Microbubble Clusters.

The purpose of this study is to introduce a new concept of chemically cross-linked microbubble clusters (CCMCs), which are individual microbubble ultrasound contrast agents (UCAs) physically tethered together. We demonstrate a facile means of their production, characterize their size and stability, and describe how they can potentially be used in biomedical applications. By tethering UCAs together into CCMCs, we propose that novel methods of ultrasound mediated imaging and therapy can be developed through unique interbubble interactions in an ultrasound field. One of the major challenges in generating CCMCs is controlling aggregate sizes and maintaining stability against Ostwald ripening and coalescence. In this study, we demonstrate that chemically cross-linked microbubble clusters can produce small (<10 μm) quasi-stable complexes that slowly fuse into bubbles with individual gas cores. Furthermore, we demonstrate that this process can be driven with low-intensity ultrasound pulses, enabling a rapid fusion of clusters which could potentially be used to develop novel ultrasound contrast imaging and drug delivery strategies in future studies. The development of novel microbubble clusters presents a simple yet robust process for generating novel UCAs with a design that could allow for more versatility in contrast-enhanced ultrasound (CEUS), molecular imaging, and drug delivery applications. Additionally, microbubble clustering is a unique way to control size, shell, and gas compositions that can be used to study bubble ripening and coalescence in a highly controlled environment or study the behavior of mixed-microbubble populations.

Halo concentration, galaxy red fraction, and gas properties of optically defined merging clusters

Abstract We present multi-wavelength studies of optically defined merging clusters, based on the Hyper Suprime-Cam Subaru Strategic Program. Luminous red galaxies, tracing cluster mass distributions, enable us to identify cluster subhalos at various merging stages, and thus make a homogeneous sample of cluster mergers that is unbiased with respect to the merger boost of the intracluster medium (ICM). We define, using a peak-finding method, merging clusters with multiple peaks and single clusters with single peaks from the CAMIRA cluster catalog. Stacked weak-lensing analysis indicates that our sample of merging clusters is categorized into major mergers. The average halo concentration for the merging clusters is ∼70% smaller than that of the single-peak clusters, which agrees well with predictions of numerical simulations. The spatial distribution of subhalos is less centrally concentrated than the mass distribution of the main halo. The fractions of red galaxies in the merging clusters are not higher than those of the single-peak clusters. We find a signature of the merger boost of the ICM from the stacked Planck Sunyaev–Zel’dovich effect and ROSAT X-ray luminosity, but not in optical richness. The stacked X-ray surface brightness distribution, aligned with the main subhalo pairs of low-redshift and massive clusters, shows that the central gas core is elongated along the merger axis, and overall gas distribution is misaligned by ∼60°. The homogeneous, unbiased sample of cluster mergers and multi-wavelength follow-up studies provide a unique opportunity to make a complete picture of merger physics over the whole process.

Prediction of flow distribution of vertical upward co-current adiabatic annular flow in 8 × 8 rod bundle

Annular flow in rod bundle occurs frequently in boiling water reactor (BWR) under normal operation and in pressurized water reactor (PWR) under accident conditions. When annular flow occurs, rod film thickness is one of the most important parameters for safety concern. In order to calculate rod film thickness distribution inside rod bundle, both gas and liquid velocity distribution inside rod bundle is necessary. Also, flow distribution inside rod bundle is of importance for calculation of interfacial shear stress and other parameters in each sub-channel. However, entrained droplets in gas core can sharpen the gas velocity profile while existing rods can flatten the gas velocity profile, making it different from that of single phase flow. The liquid velocity distribution inside rod bundle is hard to obtain from experiment because of the complex structure of its geometry. Due to these reasons, this paper deducts gas and liquid velocity profiles from existing adiabatic rod film thickness data. Even the gas velocity profiles for different flow conditions are different, there exists a gas velocity profile that can be applied to all current flow conditions with minimum uncertainties. Based on that gas velocity profile, liquid velocity profile can be calculated. From these flow velocity profiles, film thickness on each rod and interfacial shear stress in each sub-channel can be calculated.