Radial Gas Flow Research Articles

Different behaviour of the gas-phase and stellar metallicity in the central part of MaNGA galaxies

We quantified the disparity between gas-phase and stellar metallicity in a large galaxy sample obtained from the MaNGA DR17 survey. We found that the gas metallicity is on average closely aligned with the stellar metallicity in the centers of intermediate-mass galaxies. Conversely, the difference is notably larger within the center of massive galaxies. It reaches about −0.18 dex on average for the most massive galaxies, while for low-mass galaxies, the gas metallicity exhibits a slightly lower value than the stellar metallicity. Moreover, the most prominent instances of a reduced gas-phase metallicity in relation to stellar metallicity were observed within the centers of massive red galaxies with low specific star formation rates. Because of the absence of a correlation between the integral mass fraction of neutral gas and the disparity between gas and stellar metallicity, we suggest that the diminished gas-phase metallicity in the centers of massive galaxies might be attributed to the replenishment of gas-depleted central regions through processes such as radial gas flows or accretion from the circumgalactic medium rather than gas infall from the intergalactic medium.

Morphology and Kinematics of the Gas in M51: How Interaction with NGC 5195 Has Molded the Structure of Its Arms

The Whirlpool Galaxy is a well-studied grand design galaxy with two major spiral arms, and a large satellite NGC 5195. The arms both show long uniform sections with perturbations (“kinks” or sharp turns) in specific regions. Comparing the two arms shows a small radial offset between the main kinked regions. We analyzed the morphology and also the velocity field in the disk of M51 using kinematic maps based on Hα and CO line emission. These sample complementary radial ranges, with the CO map covering the central zone and the Hα map extending to cover the outer zone. We looked for indicators of density wave resonance, zones where radial flows of gas in the disk plane reverse their sign. These were present in both velocity maps; their 2D localization placed them along or closely parallel to the spiral arms, at a set of well-defined galactocentric radii, and notably more concentrated along the southern, stronger arm. The results can be well interpreted quantitatively, using a numerical model of the interaction of M51 and NGC 5195 in which the satellite has made two relatively recent passes through the disk plane of M51. During the first pass the pair of dominant spiral arms was stimulated, and during the second pass the strong kinks in both arms were formed at about the same time. The second interaction is particularly well characterized, because the timescale corresponding to the production of the kinks and the recovery of the original pitch angle is identical for the two arms.

The ALMaQUEST Survey XIV: do radial molecular gas flows affect the star-forming ability of barred galaxies?

ABSTRACT We investigate whether barred galaxies are statistically more likely to harbour radial molecular gas flows and what effect those flows have on their global properties. Using 46 galaxies from the ALMA-MaNGA QUEnching and STar formation (ALMaQUEST) survey, we identify galaxies hosting optical bars using a combination of the morphological classifications in Galaxy Zoo 2 and HyperLEDA. In order to detect radial molecular gas flows, we employ full 3D kinematic modelling of the ALMaQUEST 12CO(1–0) data cubes. By combining our bar classifications with our radial bar-driven flow detections, we find that galaxies classed as barred are statistically more likely to host large-scale radial gas motions compared to their un-barred and edge-on galaxy counterparts. Moreover, the majority of barred galaxies require multicomponent surface brightness profiles in their best-fitting models, indicative of the presence of resonance systems. We find that galaxies classed as barred with radial bar-driven flows (‘barred + radial flow’ subset) have significantly suppressed global star-formation efficiencies compared to barred galaxies without radial bar-driven flows and galaxies in the other morphological sub-samples. Our ‘barred + radial flow’ subset galaxies also possess consistently centrally concentrated molecular gas distributions, with no indication of depleted gas mass fractions, suggesting that gas exhaustion is not the cause of their suppressed star formation. Furthermore, these objects have higher median gas mass surface densities in their central 1 kpc, implying that central gas enhancements do not fuel central starbursts in these objects. We propose that dynamical effects, such as shear caused by large-scale inflows of gas, act to gravitationally stabilize the inner gas reservoirs.

The interplay between feedback, accretion, transport, and winds in setting gas-phase metal distribution in galaxies

ABSTRACT The recent decade has seen an exponential growth in spatially resolved metallicity measurements in the interstellar medium (ISM) of galaxies. To first order, these measurements are characterized by the slope of the radial metallicity profile, known as the metallicity gradient. In this work, we model the relative role of star formation feedback, gas transport, cosmic gas accretion, and galactic winds in driving radial metallicity profiles and setting the mass–metallicity gradient relation (MZGR). We include a comprehensive treatment of these processes by including them as sources that supply mass, metals, and energy to marginally unstable galactic discs in pressure and energy balance. We show that both feedback and accretion that can drive turbulence and enhance metal-mixing via diffusion are crucial to reproduce the observed MZGR in local galaxies. Metal transport also contributes to setting metallicity profiles, but it is sensitive to the strength of radial gas flows in galaxies. While the mass loading of galactic winds is important to reproduce the mass–metallicity relation (MZR), we find that metal mass loading is more important to reproducing the MZGR. Specifically, our model predicts preferential metal enrichment of galactic winds in low-mass galaxies. This conclusion is robust against our adopted scaling of the wind mass-loading factor, uncertainties in measured wind metallicities, and systematics due to metallicity calibrations. Overall, we find that at z ∼ 0, galactic winds and metal transport are more important in setting metallicity gradients in low-mass galaxies whereas star formation feedback and gas accretion dominate setting metallicity gradients in massive galaxies.

Enhancing plasma arc penetration ability with radial gas flow

Enhancing plasma arc penetration ability with radial gas flow

The concept of axial movement of blast furnaces and temperature distribution on the horizon of air tuyeres

The purpose of the work is to clarify the data on temperature changes on the horizon of the air tuyeres of blast furnaces. The limitations associated with the implementation of the well-known concept of axial movement of blast furnaces in terms of temperature stabilization in the coke nozzle blast furnace are considered. Based on the comparison of the results of studies on the temperature distribution of coke and its fractional composition at level of air tuyeres, it is shown that on blast furnaces equipped with coneless filling devices and coal dust blowing units, the critical zone in the distribution of temperatures and their fluctuations in time is the intermediate zone between "bird's nest" and the center of the furnace. A temporary, but sufficiently long-term decrease in the temperature of coke to 1000 °C in the intermediate zone of modern blast furnaces is not accompanied by the danger of toterman formation, which is facilitated by the existence of an axial coke vent — a kind of heated core of the coke nozzle and sufficient thermal inertia of the furnace. It has been established that the increase in blowing costs affects distribution of coke temperatures on the horizon of air tuyeres in a similar way to the tendency of the hot strength of coke to deteriorate — the temperatures in the intermediate zone of the coke nozzle decrease. It is recommended to take into account the change in the quality of the loaded coke when choosing dimensions of the coke vent in the center of the furnace and the degree of forcing its course by blowing. In the conditions of using pulverized coal fuel, when working on coke of average quality, the most acceptable mode of organization of the radial gas flow is peripheral-axial with an advantage in the development of axial over peripheral. Despite some conventionality of the examples discussed in the article, it can be argued that a long axial stroke without stroke disturbances can be realized only if the intensity of the peripheral gas flow is maintained for specific conditions. That is, in an ideal form, axial movement of blast furnace melting is practically impossible.

Chemical evolution with radial mixing redux: a detailed model for formation and evolution of the Milky Way

ABSTRACT We present a multizone galactic chemical evolution (GCE) model for the Milky Way that takes the most recently updated yields of major nucleosynthesis channels into account. It incorporates physical processes commonly found in previous GCE models like gas feedback from supernovae and star formation, the radial flow of gas in the disc, and the infall of fresh gas, along with stellar scattering processes like radial migration. We individually analyse the effect of different physical processes present in our model on the observed properties of the Galaxy. The radial flow of gas in the disc plays an important role in establishing the radial gradient for [Fe/H] in the low-[α/Fe] sequence. Our model with one episode of smooth gas infall and constant star formation efficiency is capable of reproducing the observed ([Fe/H], [α/Fe]) distribution of stars at different (R, |z|) positions in the Milky Way. Our results point to the rapid evolution of [α/Fe] after the onset of Type Ia supernovae and a high star formation rate during the formation of the high-[α/Fe] sequence as the origin of dual peaks in [α/Fe]. A secondary infall is unnecessary to reproduce the [α/Fe] gap and chemical spread in the disc in our model. We additionally compare the median age for various mono-abundance populations and the age–metallicity relation at different (R, |z|) positions from our fiducial model to observations. We discuss our results in relation to other related work in detail.

3D Modeling of the Molecular Gas Kinematics in Optically Selected Jellyfish Galaxies

Cluster galaxies are subject to the ram pressure exerted by the intracluster medium, which can perturb or even strip away their gas while leaving the stars undisturbed. We model the distribution and kinematics of the stars and the molecular gas in four late-type cluster galaxies (JO201, JO204, JO206, and JW100), which show tails of atomic and ionized gas indicative of ongoing ram pressure stripping. We analyze MUSE@VLT data and CO data from the Atacama Large Millimeter Array searching for signatures of radial gas flows, ram pressure stripping, and other perturbations. We find that all galaxies, with the possible exception of JW100, host stellar bars. Signatures of ram pressure are found in JO201 and JO206, which also shows clear indications of ongoing stripping in the molecular disk outskirts. The stripping affects the whole molecular gas disk of JW100. The molecular gas kinematics in JO204 is instead dominated by rotation rather than ram pressure. We also find indications of enhanced turbulence of the molecular gas compared to field galaxies. Large-scale radial flows of molecular gas are present in JO204 and JW100, but more uncertain in JO201 and JO206. We show that our sample follows the molecular gas mass–size relation, confirming that it is essentially independent of environment even for the most extreme cases of stripping. Our findings are consistent with the molecular gas being affected by the ram pressure on different timescales and less severely than the atomic and ionized gas phases, likely because the molecular gas is denser and more gravitationally bound to the galaxy.

ALMA Band 6 high-resolution observations of the transitional disk around SY Chamaeleontis

Abstract In this study, we reported the results of high-resolution (${0{^{\prime \prime}_{.}}14}$) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 225 GHz dust continuum and CO molecular emission lines from the transitional disk around SY Cha. Our high-resolution observations clearly revealed the inner cavity and the central point source for the first time. The radial profile of the ring can be approximated by a bright narrow ring superimposed on a fainter wide ring. Furthermore, we found that there is a weak azimuthal asymmetry in dust continuum emission. For gas emissions, we detected 12CO(2–1), 13CO(2–1), and C18O(2–1), from which we estimated the total gas mass of the disk to be 2.2 × 10−4 M ⊙ , assuming a CO/H2 ratio of 10−4. The observations showed that the gas is present inside the dust cavity. The analysis of the velocity structure of the 12CO(2–1) emission line revealed that the velocity is distorted at the location of the dust inner disk, which may be owing to a warping of the disk or radial gas flow within the cavity of the dust disk. High-resolution observations of SY Cha showed that this system is composed of a ring and a distorted inner disk, which may be common, as indicated by the survey of transitional disk systems at a resolution of ${\sim}{0{^{\prime \prime}_{.}}1}$.

Similar Signatures of Coplanar Gas Inflow and Disk Warps in Galactic Gas Kinematic Maps

Hydrodynamic simulations suggest that galactic gas disks form when coplanar gas spirals into the inner regions of the disk. We recently presented a simple modified accretion disk model of viscous galactic disks in which star formation is fed by a radial flow of gas. However, little observational evidence has been presented for such inflows, which are expected to be only a few kilometers per second in the central regions of the disk, i.e., within four disk scale lengths, but could reach of order 50–100 km s−1 in the very outer disk. The effects of systematic inflow on the 2D velocity field are examined and it is shown that these are quite similar to those produced by geometric warps of the disks, with twist distortions of both the kinematic major and minor axes. This makes it potentially difficult to distinguish between these in practice. By comparing the handedness of the observed twisting of the kinematic axes and of the spiral arms for a sample of nearby galaxies, we find (assuming that the spiral arms are generally trailing) that the effects of warps are in fact likely to dominate over the effects of radial inflows. However, the common practice of treating these twist distortions of the kinematic major and minor axes as being due only to warps can lead, for galaxies of low-to-intermediate inclinations, to substantial underestimates of any systematic inflow.

Dust ring and gap formation by gas flow induced by low-mass planets embedded in protoplanetary disks

Context. Recent high-spatial-resolution observations have revealed dust substructures in protoplanetary disks such as rings and gaps, which do not always correlate with gas. Because radial gas flow induced by low-mass, non-gas-gap-opening planets could affect the radial drift of dust, it potentially forms these dust substructures in disks. Aims. We investigate the potential of gas flow induced by low-mass planets to sculpt the rings and gaps in the dust profiles. Methods. We first perform three-dimensional hydrodynamical simulations, which resolve the local gas flow past a planet. We then calculate the trajectories of dust influenced by the planet-induced gas flow. Finally, we compute the steady-state dust surface density by incorporating the influences of the planet-induced gas flow into a one-dimensional dust advection-diffusion model. Results. The outflow of the gas toward the outside of the planetary orbit inhibits the radial drift of dust, leading to dust accumulation (the dust ring). The outflow toward the inside of the planetary orbit enhances the inward drift of dust, causing dust depletion around the planetary orbit (the dust gap). Under weak turbulence (αdiff ≲ 10−4, where αdiff is the turbulence strength parameter), the gas flow induced by the planet with ≳1M⊕ (Earth mass) generates the dust ring and gap in the distribution of small dust grains (≲1 cm) with a radial extent of ~1–10 times the gas scale height around the planetary orbit without creating a gas gap and pressure bump. Conclusions. The gas flow induced by low-mass, non-gas-gap-opening planets can be considered a possible origin of the observed dust substructures in disks. Our results may be helpful in explaining the disks whose dust substructures were found not to correlate with those of the gas.

Effect of the Nozzle Radial Position and Gas Flow Rate on Mass Transfer During Bottom Gas Injection in Ladles with One Nozzle

Effect of the Nozzle Radial Position and Gas Flow Rate on Mass Transfer During Bottom Gas Injection in Ladles with One Nozzle

Radial Motions and Radial Gas Flows in Local Spiral Galaxies

Abstract We determine radial velocities and mass flow rates in a sample of 54 local spiral galaxies by modeling high-resolution and high-sensitivity data of the atomic hydrogen emission line. We found that, although radial inflow motions seem to be slightly preferred over outflow motions, their magnitude is generally small. Most galaxies show radial flows of only a few km s−1 throughout their H i disks, either inward or outward, without any clear increase in magnitude in the outermost regions, as we would expect for continuous radial accretion. Gas mass flow rates for most galaxies are less than 1 M ⊙ yr−1. Over the entire sample, we estimated an average inflow rate of 0.3 M ⊙ yr−1 outside the optical disk and of 0.1 M ⊙ yr−1 in the outskirts of the H i disks. These inflow rates are about 5–10 times smaller than the average star formation rate of 1.4 M ⊙ yr−1. Our study suggests that there is no clear evidence for systematic radial accretion inflows that alone could feed and sustain the star formation process in the inner regions of local spiral galaxies at its current rate.

A controllable and byproduct-free synthesis method of carbon-coated silicon nanoparticles by induction thermal plasma for lithium ion battery

Carbon coated silicon nanoparticle is regarded as a promising anode material for the next generation of lithium ion batteries, while the development of a cost-effective and environmental-friendly preparation method is still difficult and hinders the practical implementation. In this research, a controllable and byproduct-free synthesis method is proposed for the preparation of silicon nanoparticles with amorphous hydrogenated carbon coating. The current apparatus is operated based on the application of induction thermal plasma. Plasma properties are tunable by adjusting the ratio of tangential and radial gas flow rates (T/R), which compose the plasma sheath gas. Obtained results reveal the plasma shape is shrunk with higher T/R values, which will lead to a steeper temperature gradient and lower temperature distributions in reaction chamber. Consequently, the compositions and properties of synthesized particles can be modified with T/R values. The formation of SiC, which was an intractable issue before, can be vanished at higher tangential gas flow rates in current research and the capacity of silicon anode for batteries will be improved in predict. This research is significant for a deep understanding of plasma synthesis processing and design of batteries with excellent performance.

The parametrization of gas flows in discs in the Auriga simulations

ABSTRACT We study the radial motions of cold, star-forming gas in the secular evolution phase of a set of 14 magnetohydrodynamical cosmological zoom-in simulations of Milky Way-mass galaxies. We study the radial transport of material within the disc plane in a series of concentric rings. For the gas in each ring at a given time we compute two quantities as a function of time and radius: (1) the radial bulk flow of the gas and (2) the radial spread of the gas relative to the bulk flow. Averaging the data from all the haloes, we find that the radial spread increases with radius in the form of a power law with strong secondary dependencies on the fraction of accreted material and the local radial velocity dispersion of the gas. We find that the bulk motion of gas is well described in the inner disc regions by a radially independent mean inwards flow speed of $-2.4\, \rm {km\ s}^{-1}$. The spread around this value relates to the change in angular momentum of the gas and also the amount of accreted material. These scalings from fully cosmological, MHD simulations of galaxy formation can then be used in semi-analytic models to better parametrize the radial flow of gas in discs.

Chemical evolution of the Milky Way: constraints on the formation of the thick and thin discs

ABSTRACT We study the evolution of Milky Way thick and thin discs in the light of the most recent observational data. In particular, we analyse abundance gradients of O, N, Fe, and Mg along the thin disc as well as the [Mg/Fe] versus [Fe/H] relations and the metallicity distribution functions at different Galactocentric distances. We run several models starting from the two-infall paradigm, assuming that the thick and thin discs formed by means of two different infall episodes, and we explore several physical parameters, such as radial gas flows, variable efficiency of star formation, different times for the maximum infall on to the disc, different distributions of the total surface mass density of the thick disc, and enriched gas infall. Our best model suggests that radial gas flows and variable efficiency of star formation should be acting together with the inside-out mechanism for the thin disc formation. The time-scale for maximum infall on to the thin disc, which determines the gap between the formation of the two discs, should be tmax ≃ 3.25 Gyr. The thick disc should have an exponential, small-scale length density profile and gas infall on the inner thin disc should be enriched. We also compute the evolution of Gaia–Enceladus system and study the effects of possible interactions with the thick and thin discs. We conclude that the gas lost by Enceladus or even part of it could have been responsible for the formation of the thick disc but not the thin disc.

Study and application of dynamic inversion model of coal seam gas pressure with drilling

The determination of gas pressure is a prerequisite for preventing coal and gas outburst. The traditional measurement method has some shortcomings, such as few test points, long test time and complicated process. In this paper, after analyzing the gas emission law of coal particle and the radial gas flow rule of borehole wall, a real-time and fast method for calculating gas pressure with drilling is proposed to establish gas pressure dynamic inversion model based on gas emission quantity of borehole, which is applied to inversion calculation of gas pressure in the directional drilling process. The results show that: (1) Inversion of gas pressure shows that the physical properties of coal seam and the characteristics of gas adsorption affect the amount of gas emission, resulting in different calculation results of gas pressure, which proves the uneven distribution of gas pressure the in coal seam; (2) According to the comparison results, the error range between the theoretical value and the measured value of gas pressure is from 3.6% to 18.1%, which indicates the correctness and reliability of the new model. The error is mainly influenced by the gas emission quantity of coal particle and the permeability coefficient of coal seam after gas desorption; (3) Field application results show that there are many abnormal regions of gas pressure in the coal seam because of geological structure existence. The research results have important practical significance for the analysis of distribution law of coal seam gas and the identification of gas outburst risk.

Numerical thermofluid simulation on tandem type of induction thermal plasmas with and without current modulation in a lower coil

This paper describes numerical calculations on tandem-type induction thermal plasmas with and without current modulation of the lower coil. The tandem type of induction thermal plasma (tandem-ITP) has been developed with two independent rf coils in one plasma torch for stable operation and spatial control of temperature field in ITP. Furthermore, the coil current modulation for tandem-ITP, i.e. tandem type of pulse-modulated induction thermal plasma (tandem-PMITP), is expected to offer a temporo-spatially varying temperature field in the plasma torch. First, as described in this paper, a numerical thermofluid model was developed for tandem-ITP/PMITP with an upper coil and a lower coil to investigate unique temperature and gas flow fields. Secondly, the influence of gap length between the upper coil and the lower coil was studied in the tandem-ITP under steady state conditions. Results show that a shorter gap length between two coils of the tandem-ITP is favourable for materials processing because it suppresses unfavourable radial gas flow to the wall in the plasma torch. Thirdly, transient calculation was conducted for the tandem-PMITP with current modulation in the lower coil to investigate effects of an off-time modulation parameter on the temperature field. Results showed that coil current modulation provides unique temporo-spatially varying temperature and gas flow fields. Finally, calculation results for a tandem-PMITP were compared with those for a single-coil PMITP. Comparison revealed that tandem-PMITP has higher robustness in modulated induction thermal plasma by maintaining a higher-temperature region than that of the single-coil MITP. The tandem-PMITP can provide more controlled temperature and gas flow fields.

考虑气体加速效应的高压气井产能方程推导及其应用

Non-Darcy flow in a gas well cannot be expressed with traditional binomial equations or trinomial equations for ultra-deep high pressure gas reservoirs, which leads to large errors of open flow capacities for the neglect of gas acceleration effects. A new method was presented with gas acceleration effects. Under the assumption of high-pressure radial gas flow, through combination of the continuity equation, the Darcy-Forchheimer equation with acceleration and the isothermal state equation, the productivity equation was derived. The proposed equation is also able to replace traditional binomial equations, but has no analytical solution. It can be simplified by analogy, and the related coefficients can be solved by trial and error. The application of the proposed method in data process of ultra-deep high pressure gas well Xi35-1 in Sichuan Basin is effective, and the comparison with the real production data proves the precision of the calculated productivity. The proposed method avoids the disadvantages of the relative error increase with the differential pressure. The work enriches the productivity prediction methods, with accurate calculation of open flow capacities and reasonable determination of high pressure gas well productivities.

Model-Based Analysis of Factors Affecting the Burden Layer Structure in the Blast Furnace Shaft

The distribution of burden layers in an ironmaking blast furnace strongly influences the conditions in the upper part of the process. The bed permeability largely depends on the distribution of ore and coke in the lumpy zone, which affects the radial gas flow distribution in the shaft. Along with the continuous advancement of technology, more information about the internal conditions of the blast furnace can be obtained through advanced measurement equipment, including 2D profiles and 3D surface maps of the top burden surface. However, the change of layer structure along with the burden descent cannot be directly measured. A mathematical model predicting the burden distribution and the internal layer structure during the descending process is established in this paper. The accuracy of the burden distribution model is verified by a comparison with experimental results. A sensitivity study was undertaken to clarify the role of some factors on the arising layer distribution, including the descent-rate distribution, the initial burden surface profile, and the charging direction through the charging matrix. The findings can be used as a theoretical basis to guide plant operations for optimizing the charging.