• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.51.2-51.2
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• 2021

Nuclear rings are sites of intense star formation at the center of barred spiral galaxies. A straightforward but unanswered question is what controls star formation rate (SFR) in nuclear rings. To understand how the ring SFR is related to mass inflow rate, gas content, and background gravitational field, we run a series of semi-global hydrodynamic simulations of nuclear rings, adopting the TIGRESS framework to handle radiative heating and cooling as well as star formation and supernova feedback. We find: 1) when the mass inflow rate is constant, star formation proceeds in a remarkably steady fashion, without showing any burst-quench behavior suggested in the literature; 2) the steady state SFR has a simple linear relationship with the inflow rate rather than the ring gas mass; 3) the midplane pressure balances the weight of the overlying gas and the SFR surface density is linearly correlated with the midplane pressure, consistent with the self-regulated star formation theory. We suggest that the ring SFR is controlled by the mass inflow rate in the first place, while the gas mass adjusts to the resulting feedback in the course of achieving the vertical dynamical equilibrium.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.63.4-64
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• 2016

We aim to investigate inflow history of matters that fall into the satellite systems around a dwarf galaxy in Lambda-Cold Dark Matter model. Each satellite system has unique properties because all satellite systems have different mass inflow history by environments and/or the events such as cosmic reionization and merging with other halos. To trace mass inflow history of the satellite systems, we perform three different cosmological zoom simulations whose galaxy mass is ${\sim}10^{10}M_{sun}$. Each initial zoom simulation covers a cubic box of $1Mpc/h^3$ with 17 million particles. Particle mass for dark matter (DM) and gas components is $M_{DM}=4.1{\times}10^3M_{sun}$ and $M_{gas}=7.9{\times}10^2M_{sun}$, respectively. Thus, each satellite system is resolved with more than hundreds - thousands of particles. We analyze the influence of the gravitational interaction with host galaxy, baryonic matter inflow by various cooling mechanisms, and merging events with other halos on the mass inflow history of satellite systems.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.341-344
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• 2008

Computational studies have been performed to analyze the particle loadings onto the filters according to the different inflow pattern of dusty gas and the flow uniformities on the filter surface of back-blown gas at different permeability of porous media setup at the filter outlet. This is preliminary study to find how we can reduce the regeneration time and improve the regeneration efficiency of filters with dust layer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.5
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• pp.425-434
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• 2007

An integrated adsorption/catalytic process has been considered to treat dioxin and $NO_x$ simultaneously. The process consists of a cyclone and a reactor with nine bag filters. In this study, numerical analysis has been performed to understand flow characteristics with inflow-duct types in the reactor. To consider flue gas and activated carbon particles simultaneously, Euler-Lagrangian model was employed. Fundamental flow patterns of flue gas and activated carbon particles, pressure distribution and distribution of activated carbon have been obtained from the numerical analysis. Also trace length and residence time of flue gas, residence time of activated carbon particles have been calculated directly. Flow patterns of flue gas and activated carbon particles in the reactor were very complicated and they moved along very various paths. Therefore, their residence time in the reactor was also various. The flow characteristics in the reactor were strongly influenced by inflow-duct types. The results obtained would be effectively used to estimate the removal efficiency in the reactor once the residence time is combined with the reaction equation.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.983-987
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• 2008

Computational simulation has been performed to design optimally the filtration system for IGCC pilot plant. It was analyzed how the different inflow pattern influences the flow field and the particle behavior in a filter vessel. The particle loading onto the filter surface lowers significantly and decreases dramatically with particle size when the dusty gas flows into the filter vessel with a shroud tube through a tangential inlet setup tangentially on the vessel outer wall. However, the particle loading is considerably high when the dusty gas enters the filter vessel through a normal inlet setup vertically on the vessel top wall, and the decrease of the particle loading with particle size is not steeper compared with the tangential inflow pattern.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1084-1087
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• 2017

When a liquid rocket engine is started the oxidizer and fuel must be flowed into combustion chamber and gas generator with time differences. The wrong time difference between propellants or malfunction of ignition device can occur the explosion of combustion chamber due to detonation by energized premixed-propellants. Therefore it is important to observe the transient characteristic of propellants or to measure the inflow time of propellants into combustion chamber and gas generator. The measurement of static pressure is not enough to observe the propellants inflow time into combustion chamber and gas generator. By measuring dynamic pressure of main flow passage of propellants the accurate propellants inflow time could be investigated.

• Journal of Environmental Science International
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• v.10 no.1
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• pp.59-64
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• 2001

The effect of major operating parameters in spray drying sorber(=SDS) for automatic control for the simultaneous removal of acidic and organic gaseous pollutants from solid waste incinerator was performed. The field experiment was carried out in pilot scale test for the quantification of major operating parameters of hydrophilic and the hydrophobic pollutants. The removal efficiencies of $SO_2$and HCI in the 5wt% slurry condition were being increased with the increase of the stoichiometric ration which is the molecular ratio of lime to the pollutant concentration, and with the decrease of inflow flue gas temperature in the pilot SDS reactor. The removal efficiency along the height of spray drying sorber was closely related to the temperature profile, and more than 90% of total removal efficiency was achieved in an absorption region. For the removal of acidic gas the optimum operating condition considering the economics and a stable operation is the 5wt% of slurry concentration, 1.2 of stoichiometric ratio and 25$0^{\circ}C$ of inflow flue gas temperature. For the organic gases of benzene and toluene the removal efficiencies were 20-60% which is much lower than that of acidic gas. The best removal efficiency was obtained at 1.5 of stoichiometric ratio and 25$0^{\circ}C$ of inflow flue gas temperature. The organic\`s removal efficiency along the height of spray drying sorber was quite different from that of acidic gas, that is, more than 60% of the total removal efficiency for benzene and 90% of the total removal for toluene were achieved in the dried adsorption region, which was formed at the lower or exit part of the reactor.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.56.1-56.1
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• 2011

We investigate the hydrodynamics of gas clouds in the central few hundred parsecs of the Galaxy. Non-axisymmetry (elongation) of the Galactic bulge can form a reservoir of dense molecular clouds at around two hundred parsecs from the center through the X1-X2 orbit transfer, and the star formation that has been sustained for the lifetime of the galaxy can build up a nuclear bulge there. If the nuclear bulge is elongated, this again can transport the gas there down to the central few parsecs region. We perform a series of 3-D hydrodynamic simulations that consider a potential for this "nested bar", cooling/heating, star formation and supernova feedback, and estimate the efficiency of the gas inflow down to the central parsec region.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.59.1-59.1
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• 2015

We present hydrodynamic simulations of gas clouds that inflowing from the disk to a few hundred parsec region of the Milky Way. Realistic Galactic structures are included in our simulations by thousands of multipole expansions that describe 6.4 million stellar particles of a self-consistent Galaxy simulation (Baba, Saitoh & Wada, in prep.). We find that a hybrid multipole expansion model with two different basis sets and a thick disk correction well reproduces the overall structures of the Milky Way. We find that the nuclear ring evolves into 240 pc at T~1500 Myr, regardless of the initial size. For most of simulation runs, gas inflow rate to the nuclear region is equilibrated as ~0.02 Msun/yr, and thus accumulated gas mass and star formation activity is stabilized as $6{\times}10^7Msun$ and ~0.02M/yr, respectively. These stabilized values are in a good agreement with estimations for the CMZ. The nuclear ring is off-centered to the Galactic center by the lopsided central mass distribution of the Galaxy model, and thus an asymmetric mass distribution is arose accordingly. The lopsidedness also leads the nuclear ring to be tilted to the Galactic plane and to precess along the Galaxy rotation. In early evolutionary stage when gas clouds start to inflow and form the nuclear ring, the z-directional oscillations of the gas clouds results in the twisted, infinity-shaped nuclear ring. Since the infinity-shaped feature is transient only for first 100 Myr, the current infinity-shape observed in the CMZ may indicate that the CMZ forms quite recently.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.134-134
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• 2010

Recently, the interest of the study about IGCC(Integrated Gasification Combined Cycle), one of New & Renewable Energy technologies, bas been increased due to the United Nations Framework Convention on Climate Change, the Low Carbon Green Growth policy, etc. Also, with this interest of IGCC, the study on the gas turbine utilizing the synthetic gas is performing actively. In the study of the gas turbine characteristic, the power performance and the combustion efficiency are mainly discussed and also the concern about the exhaust gas is being taken care of due to the increasing awareness of the environment. With this, we would like to go over the exhaust gas emission characteristic by the synthetic gas inflow in this test. In order to conduct such a test, we constructed a synthetic gas supplying system to supply the synthetic gases ($H_2$: hydrogen, $N_2$: nitrogen, CO: carbon monoxide, $CO_2$: carbon dioxide, and $H_2O$: steam) quantitatively and this combustion test was conducted by controlling the supplied synthetic gases artificially. The concentration of the exhaust gases appeared variously depending on the differences of the inflow nitrogen amount and the steam amount, whether or not the carbon dioxide flow in and so on. The results of the test can be able to be utilized for the IGCC study by understanding the exhaust gas emission characteristic of the coal gas turbine by synthetic gas composition.