• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.7
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• pp.337-343
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• 2015

This paper investigates the ventilation characteristics in a two-dimensional underground network junction composed of four main lines interconnected by eight ramps. Simple one-dimensional models cannot be applied to network junctions since there are interferences of traffic piston effects in the main lines and at the ramps. A numerical algorithm was developed to analyze the pressure and airflow distributions iteratively. The Darcy-Weisbach equation was used to calculate the piston effects by traffic flows, and a Hardy Cross iteration was conducted for network analysis at the interconnected junction. The results show interesting ventilation characteristics and CO concentration distributions depending on system parameters such as vehicle speed, tunnel diameter, and other junction configurations.

• International Journal of High-Rise Buildings
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• v.3 no.2
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• pp.121-145
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• 2014

The story shear force distributions of most seismic design codes generally reflect the influences of higher vibration modes based on the elastic deformations of structures. However, as the seismic design allows for the plastic behavior of a structure, the story shear force distribution shall be effective after it is yielded due to earthquake excitation. Hence this study conducted numerical analyses on the story shear force distributions of most seismic design codes to find out the characteristics of how a structure is damaged between stories. Analysis results show that the more forces are distributed onto high stories, the lower its concentration is and the more energy is absorbed. From the results, this study proposes the optimum story shear force distribution and its calculation formula that make the damages uniformly distributed onto whole stories. Consequently, the story damage distribution from the optimum calculation formula was considerably more stable than existing seismic design codes.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.648-653
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• 2001

This study represents the numerical analysis of natural convection of a microenvironments with a air permeability in the clothing air-layer. The clothing air layer of shoulder and arm was used for numerical analysis model. As a numerical analysis method, we adopted a finite volume method for two-dimensional laminar flow, and analyzed the flow and thermal characteristics of velocity, temperature and concentration in the air layer between body and clothing. As a temperature boundary conditions, we considered that a body skin has a high temperature with $34^{\circ}C$ the environmental temperatures are $5,\;15\;and\;25^{\circ}C$ for various permeability coefficients. The distributions of concentration, temperature and velocity were showed that two large cells were. formed at horizontal and vertical air layer, respectively. As the temperature difference between body skin and environment decrease, the heat transfer was decreased rapidly.

• Journal of Environmental Science International
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• v.27 no.6
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• pp.437-445
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• 2018

Laser induced-exciplex-fluorescence (EXCIPLEX) proposed by Melton is used to visualize fuel vapor in spray combustion. However, in the EXCIPLEX method based on TMPD/naphthalene system, the TMPD : naphthalene ratio is strictly restricted to 1 : 9. In addition, fluorescence intensity due to the vapor phase is extremely weak. To overcome these drawbacks, we propose a new laser-induced-excimer fluorescence (EXCIMER) method to visualize the liquid and vapor phases simultaneously. The spatial distributions of liquid and vapor in fuel spray suspended by ultrasonic waves are compared using the EXCIPLEX and EXCIMER methods. The correlation between fuel vapor concentration and fluorescence intensity is experimentally investigated by measuring the fluorescence intensity of saturated vapor formed over liquid fuel at a controlled temperature. These experimental results indicate that the EXCIMER method is effective for evaluating fuel vapor visualization in spray combustion. Furthermore, the quantitative distribution of fuel vapor concentration can be correctly estimated by the EXCIMER method.

• Journal of computational fluids engineering
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• v.6 no.4
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• pp.1-7
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• 2001

Wind flow perturbations, recirculations and turbulence generated by buildings often dominate air pollutant distributions around buildings. This paper describes dispersion of contaminants in the vicinity of a building by solving the concentration equation based on previously simulated wind flow field. Turbulence closure is achieved by using the standard k-ε two-equation model. The paper shows application of the CIP method for solving a species concentration equation of contaminant gas around a rectangular building for two different sources under conditions of neutral atmospheric stratification. Results have been compared to the experimental data and the previous numerical results by hybrid scheme. The computational results of concentration profiles by the CIP method agree well with experimental data.

• Journal of computational fluids engineering
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• v.3 no.1
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• pp.63-72
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• 1998

The numerical simulations of flowfield and pollutant dispersion over two-dimensional hills of various shapes are described. The Reynolds-averaged Wavier-Stokes equations and concentration diffusion equation based on the gradient diffusion theory have been applied to the atmospheric shear flow over the bell-shaped hills which are basic components of the complex terrain. The flow characteristics such as velocity profiles of the geophysical boundary layer, speed-up phenomena, mean pollutant concentration profiles are compared with experimental data to validate the present numerical procedure and it has been found that the present numerical results agree well with experiments and other numerical data. It has been also found that the distributions of ground level concentration are strongly influenced by the source location and height.

• 한국연소학회:학술대회논문집
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• 2001.06a
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• pp.133-138
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• 2001

In this study, quantitative nitric oxide concentration distributions are investigated in the laminar nonpremixed $H_2/N_2$ flames by laser-induced fluorescence (LIF). The measurements are taken in flames for different $N_2$ dilution ratios varying from 20${\sim}$80%, and fuel now rate is fixed as lslpm. The NO A-X (0,0) vibrational band around 226 nm is excited using a XeCl excimer-pumped dye laser. We applied same excitation line used in $CH_4$ premixed flame. Overall, NO concentration was rapidly decreased with $N_2$ addition and we could not measure the concentration any longer for $N_2$ dilution above 80%.

• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.49-55
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• 2007

The quality of chaotic mixing in three-dimensional micro channel flow has been numerically studied using Fractional-step method (FSM) and particle tracking techniques such as $Poincar{\acute{e}}$ section and Lyapunov exponents. The flow was driven by pressure distribution and the chaotic mixing was generated by applying alternating current to electrodes embedded on the bottom wall at a first half period and on the top wall at a second half period. The equations governing the velocity and concentration distributions were solved using FSM based on Finite Volume approach. Results showed that the mixing quality depended significantly on the modulation period. The modulation period for the best mixing performance was determined based on the mixing index for various initial conditions of concentration distribution. The optimal values of modulation period obtained by the particle tracking techniques were compared with those from the solution of concentration distribution equation using FSM and CFX software and the comparison showed their good match.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.156-161
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• 2000

In this study, quantitative nitric oxide concentration distributions are investigated in the post-flame zone of laminar premixed $CH_4/O_2/N_2$, flames by laser-induced fluorescence (LIF). The measurements are taken in flames for different equivalence ratios varying from $0.8{\sim}1.4$, and flow rate is fixed as 5slpm. The NO A-X (0,0) vibrational band around 226 nm is excited using a XeCl excimer-pumped dye laser. Selecting an appropriate NO transition minimizes interferences from Rayleigh scattering and $O_2$ fluorescence. NO concentration is rised when equivalence ratios increase at different vertical distances form nozzle tip. In any case, the maximum NO concentration reaches the maximum in reaction zone.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.141-144
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• 2004

An analysis procedure for the MCFC channel flow has been developed to predict the fuel cell performance. The channel formed by the uniformly distributed trapezoidal supports is approximated by the porous medium that yields the equivalent pressure drop. The Wavier-Stokes, energy, and species equations are solved to obtain the velocity, temperature and concentration fields for a local current density which is computed from electrochemical correlations. The fuel cell characteristics, such as the temperature, pressure, mole concentration, voltage and current density distributions, are presented and discussed.