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11 pages, 9181 KiB

Open AccessArticle

Extraplanar [C II] and Hα in the Edge-On Galaxy NGC 5775

by William T. Reach, Dario Fadda, Richard J. Rand and Gordon J. Stacey

Universe 2025, 11(4), 127; https://doi.org/10.3390/universe11040127 - 9 Apr 2025

Viewed by 355

Spiral galaxies are thin and susceptible to being disrupted vertically. The largest star clusters, and nuclear starbursts, generate enough energy from winds and supernovae to send disk material to the halo. Observations of edge-on galaxies allow for the clearest view of vertical disruptions. [...] Read more.

157.7 μ

m and archival images from Hubble in H

α

to search for extraplanar gas. The extraplanar [C II] extends 2 kpc from the midplane over much of the star-forming disk. The extraplanar [C II] at 2 kpc from the midplane approximately follows the rotation of the disk, with a lag of approximately 40 km

s^{- 1}

; this lag is similar to what has been previously reported in H

α

. Significant vertical extensions (to 3 kpc) are seen on the northeast side of the galaxy, potentially due to super star clusters in the NGC 5775 disk combined with gravitational interaction with the companion galaxy NGC 5774. The H

α

narrow-band image reveals a narrow plume that extends 7 kpc from the nucleus and is almost exactly perpendicular to the disk. The plume shape is similar to that seen from the comparable galaxy NGC 3628 and may arise from the nuclear starburst. Alternatively, the H

α

plume could be a relic of past activity. Full article

(This article belongs to the Special Issue Universe: Feature Papers 2024—"Galaxies and Clusters")

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18 pages, 7491 KiB

Open AccessArticle

Numerical Simulation of Membrane Separation Characteristics of Supercritical Carbon Dioxide and Water

by Zongliang Qiao, Yue Pan, Youfei Tang, Yue Cao and Fengqi Si

Membranes 2023, 13(12), 892; https://doi.org/10.3390/membranes13120892 - 29 Nov 2023

Viewed by 2093

Abstract

To solve the problem of water carryover in the supercritical CO₂ separation and mining process in the CO₂ plume geothermal system, a three-dimensional shell-tube hollow fiber membrane absorption separator is designed in this study. A coupled species transport model, a porous medium model, and an absorption mathematical model are established, and the flow field and separation characteristics in the circular and flat tubes are analyzed using numerical simulation. The results show that the membrane separation efficiency increases with an increase in the flatness and membrane tube length. When the inlet velocity of the mixture is 0.1 m/s, the separation efficiency can reach 75.92%. Selecting a smaller flow Reynolds number and a more significant membrane tube flatness will reduce the water mass fraction at the outlet. When adding baffles of different shapes to the membrane tube, the mixture fluid in the membrane tube meanders forward and flows in the shape of “Z” under the blocking effect of the arcuate baffles. With an increase in the number of arcuate baffles in the membrane tube, the membrane separation efficiency of the separator increases continuously. The mixture fluid flows in the membrane tube with the built-in torsional baffles in a spiral manner, and the separation efficiency of the membrane separator increases with a torsion ratio reduction in the membrane tube. Full article

(This article belongs to the Special Issue Research Progress of Membrane Technology in Gas Separation Processes)

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11 pages, 3035 KiB

Open AccessArticle

Spiral Thermal Plumes in Water under Conventional Heating: Numerical Results on the Effect of Rotation

by María Cruz Navarro, Damián Castaño and Henar Herrero

Mathematics 2022, 10(7), 1052; https://doi.org/10.3390/math10071052 - 25 Mar 2022

Viewed by 1754

Abstract

In this paper, we study numerically the effect of rotation within a sample of water in a cylindrical container subject to rotation which is heated with a constant temperature at the bottom and lateral wall. We analyze the temporal behavior of temperature and flow velocity of the solvent. The thermal plumes developed at lower levels, already observed in the case without rotation, begin to spiral spreading outwards by the effect of rotation, increasing the azimuthal velocity of the fluid. No significant increases in the radial and vertical velocity components are observed which do not favor the mixture of hotter and colder flows in the sample and a faster heating of the solvent. In the rotation range studied, the state loses the axisymmetry and becomes fully 3D earlier in time as the rotation rate increases. To perform simulations, we use a 3D temporal model that couples momentum and heat equations and is based on spectral element methods. Full article

(This article belongs to the Section E: Applied Mathematics)

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17 pages, 13799 KiB

Open AccessArticle

Study of the Effect of a Plug with Torsion Channels on the Mixing Time in a Continuous Casting Ladle Water Model

by Gerardo Aguilar, Gildardo Solorio-Diaz, Alicia Aguilar-Corona, José Angel Ramos-Banderas, Constantin A. Hernández and Fernando Saldaña

Metals 2021, 11(12), 1942; https://doi.org/10.3390/met11121942 - 1 Dec 2021

Cited by 3 | Viewed by 1979

Abstract

The use of porous plugs in injecting gas through the bottom of a ladle forms vertical plumes in a very similar way to a truncated cone. The gas plume when exiting the plug has a smaller diameter compared to that formed in the upper zone of the ladle because inertial forces predominate over buoyancy forces in this zone. In addition, the magnitude of the plume velocity is concentrated in an upward direction, which increases the likelihood of low velocity zones forming near the bottom of the ladle, especially in lower corners. In this work, a plug with spiral-shaped channels with different torsion angles is proposed, with the objective that the gas, when passing through them, has a tangential velocity gain or that the velocity magnitude is distributed in the three axes and does not just focus on the upward direction, helping to decrease low velocity zones near the bottom of the ladle for better mixing times. For the experimentation, we worked in a continuous casting ladle water model with two configuration injections, which in previous works were reported as the most efficient in mixing the steel in this ladle. The results obtained using the PIV technique (particle image velocimetry) and conductimetry technique indicate that the plugs with the torsion channels at angles of 60° and 120° improve the mixing times for the two injection configurations. Full article

(This article belongs to the Special Issue Numerical and Physical Modeling in Steel Refining and Casting)

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19 pages, 24576 KiB

Open AccessArticle

Numerical Study on Flow, Temperature, and Concentration Distribution Features of Combined Gas and Bottom-Electromagnetic Stirring in a Ladle

by Yang Li, Anyuan Deng, Huan Li, Bin Yang and Engang Wang

Metals 2018, 8(1), 76; https://doi.org/10.3390/met8010076 - 19 Jan 2018

Cited by 19 | Viewed by 5092

Abstract

A novel method of combined argon gas stirring and bottom-rotating electromagnetic stirring in a ladle refining process is presented in this report. A three-dimensional numerical model was adopted to investigate its effect on improving flow field, eliminating temperature stratification, and homogenizing concentration distribution. The results show that the electromagnetic force has a tendency to spiral by spinning clockwise on the horizontal section and straight up along the vertical section, respectively. When the electromagnetic force is applied to the gas-liquid two phase flow, the gas-liquid plume is shifted and the gas-liquid two phase region is extended. The rotated flow driven by the electromagnetic force promotes the scatter of bubbles. The temperature stratification tends to be alleviated due to the effect of heat compensation and the improved flow. The temperature stratification tends to disappear when the current reaches 1200 A. The improved flow field has a positive influence on decreasing concentration stratification and shortening the mixing time when the combined method is imposed. However, the alloy depositing site needs to be optimized according to the whole circulatory flow and the region of bubbles to escape. Full article

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27 pages, 774 KiB

Open AccessArticle

Adapting an Ant Colony Metaphor for Multi-Robot Chemical Plume Tracing

by Qing-Hao Meng, Wei-Xing Yang, Yang Wang, Fei Li and Ming Zeng

Sensors 2012, 12(4), 4737-4763; https://doi.org/10.3390/s120404737 - 12 Apr 2012

Cited by 49 | Viewed by 8780

Abstract

We consider chemical plume tracing (CPT) in time-varying airflow environments using multiple mobile robots. The purpose of CPT is to approach a gas source with a previously unknown location in a given area. Therefore, the CPT could be considered as a dynamic optimization problem in continuous domains. The traditional ant colony optimization (ACO) algorithm has been successfully used for combinatorial optimization problems in discrete domains. To adapt the ant colony metaphor to the multi-robot CPT problem, the two-dimension continuous search area is discretized into grids and the virtual pheromone is updated according to both the gas concentration and wind information. To prevent the adapted ACO algorithm from being prematurely trapped in a local optimum, the upwind surge behavior is adopted by the robots with relatively higher gas concentration in order to explore more areas. The spiral surge (SS) algorithm is also examined for comparison. Experimental results using multiple real robots in two indoor natural ventilated airflow environments show that the proposed CPT method performs better than the SS algorithm. The simulation results for large-scale advection-diffusion plume environments show that the proposed method could also work in outdoor meandering plume environments. Full article

(This article belongs to the Section Physical Sensors)

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