• Wind and Structures
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• v.36 no.2
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• pp.75-90
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• 2023

Turbulent wind flow over hilly terrains has been extensively investigated in the scientific literature and main findings have been included in technical standards. In particular, turbulent wind flow over nominally two-dimensional hills is often adopted as a benchmark to investigate wind turbine siting, estimate wind loading, and dispersion of particles transported by the wind, such as atmospheric pollutants, wind-driven rain, windblown snow. Windblown sand transport affects human-built structures and natural ecosystems in sandy desert and coastal regions, such as transport infrastructures and coastal sand dunes. Windblown sand transport taking place around any kind of obstacle is rarely in equilibrium conditions. As a result, the modelling of windblown sand transport over complex orographies is fundamental, even if seldomly investigated. In this study, the authors present a wind-sand tunnel test campaign carried out on a nominally two-dimensional sinusoidal hill. A first test is carried out on a flat sand fetch without any obstacle to assess sand transport in open field conditions. Then, a second test is carried out on the hill model to assess the sand flux overcoming the hill and the morphodynamic evolution of the sand sedimenting over its upwind slope. Finally, obtained results are condensed into a dimensionless parameter describing its sedimentation capability and compared with values resulting from other nominally two-dimensional obstacles from the literature.

• Atmosphere
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• v.25 no.4
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• pp.685-692
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• 2015

In this study, the effects of trees on flow and scalar dispersion in an urban street canyon were investigated using a computational fluid dynamics (CFD) model. For this, we implemented the drag terms of trees to the CFD model, and compared the CFD-simulated results to the wind-tunnel results. For comparison, we considered the same building configuration as the wind-tunnel experiment. The trees were located at the center of street canyon with the aspect ratio (defined as the ratio of the street width to the building height) of 1. First, the flow characteristics were analyzed in the tree-free and high-density tree cases and the results showed that the CFD model reproduced well the flow pattern of the wind-tunnel experiment and reflected the drag effect of trees in the street canyon. Then, the dispersion characteristics of scalar pollutants were investigated for the tree-free, low-density tree and medium-density tree cases. In the tree-free case, the nondimensionalized concentration distribution simulated by the CFD model was quite similar to that in the wind-tunnel experiment in magnitude and pattern. The correlation coefficients between the measured and simulated concentrations are more than 0.9 in all the cases. As the tree density increased, nondimensionalized concentration increased (decreased) near the wall of the upwind (downwind) building, which resulted from the decrease in wind speed case by the drag effect of trees. However, the CFD model underestimated (overestimated) the concentration near the wall of upwind (downwind) building.

• Fire Science and Engineering
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• v.18 no.2
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• pp.49-56
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• 2004

Today's popular ventilation systems include the combined jet fans and electrostatic precipitation systems or the combined jet fans and vertical shaft system. Tunnels with these two ventilation systems applied have been designed and opened, more and more interest has been put in maintenance of a tunnel after opening. Therefore. it is to become more important to come up with the optimal operation mode and the method for the evaluation of ventilation system. In this study, to evaluate a tunnel ventilation and its economy, a dynamic simulation program was developed which can simulate the unsteady-state tunnel air velocity and concentration of pollutants according to the traffic flow variations and operation condition of a ventilation system. We clarified the effectiveness usage on tunnel ventilation by using it and also we could found the most economical ventilation operation mode by application in real exit tunnel. We obtained that combination of fan system and electrostatic precipitation system was more economical than jet fan priority operation mode.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.305-315
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• 2018

In this study, the ventilation characteristics and the relationships between the required ventilation flow rate and the ventilation system flow rate was investigated by numerical method for the optimum design of the transverse ventilation and semi-transverse ventilation system in road tunnels. The following results were obtained. In supply exhaust transverse ventilation system, the system supply-exhaust air flow rate is theoretically equal to the difference between the required ventilation flow rate and natural ventilation flow rate. However, it is shown that it increases by about 10% in the analysis results. And, in the case of the longitudinal air flow rate is increased by installed jet fans, ventilation system air flow rate is reduced. However, as the longitudinal air flow rate increases, the concentration of pollutants in the tunnel decreases, so the exhaust effect of pollutants decreases, and the effect of reducing the system air flow rate is decreased. In case of semi-transverse with only air supply, ventilation system air flow rate is equal to required ventilation air flow rate when tunnel inlet velocity is negative, but results is shown it is increased within about 13.3%. Also, it was found that ventilation effect can not be expected even if the jet fans are increased when the tunnel inlet velocity is negative.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.785-796
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• 2000

In this study, the possibility of application of TUNVEN model was investigated through the validation and calibration processes. In order to validate and calibrate the TUNVEN model developed in USA to obtain prediction of the quasi-steady state longitudinal air velocities and the pollutants concentrations by solving the coupled one-dimensional steady state tunnel aerodynamic and advection equations. The major input parameters such as the concentration data for CO and $NO_x$, meteorological data and traffic volume in Hawngryung tunnel were measured. Prior to preparing the input parameters, the sensitivity analysis was conducted to identify the input parameters which need to be most accurately estimated in TUNVEN program. In order to establish the relationships between the model values and the measured values, the linear regression analysis was applied. In linear regression analysis, the model values were taken as independent parameter(X) and the measured values were taken as dependent parameter(Y) for four cases of data sef. From the results of linear regression analysis, the correlation coefficient(r) for four cases were calculated more than 0.91 and the values of slope and interception were analyzed as 0.5~2.2 and 0.01~2.3 respectively. From the above results, we concluded that the suitability of TUNVEN model was identified in prediction the longitudinal pollutant concentrations in tunnel.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.2
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• pp.307-315
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• 2016

Many countries are trying to reduce a greenhouse gas to step up their fight against climate change. There are many studies related to building only for reducing a greenhouse gas in construction area but studies related to reducing a comprehensive environmental load including various pollutants that affects the global environment are lacking. This study aims to analyse the characteristics of environmental load by work type for tunnel projects. Analysis showed that seven work types, including lining concrete, shotcrete, tunnel portal and open-cut tunnel work, etc., are representative works generated environmental load. These seven works represent 89.22 percent of total environmental load. In addition, comparison results of environmental load per tunnel's length by work type showed that a major factor of environmental load is caused by a tunnel portal and open-cut tunnel work with relatively short length (excavation length). And lining concrete and shotcrete work are larger than any other environmental load with tunnel's total length. It is expected that the result of this study will be used to make a estimation model for environmental load using approximate quantity survey of representative work types in the early stage of tunnel design. And it will be play a considerable role in establishing of environment management plan for sustainable infrastructure construction.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.4
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• pp.343-353
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• 2002

In the past many tunnels have been built to lowest capital investment cost without adequate regard for the cost of operation. But according to increasing the capacity of a ventilation system and to becoming diverse, it is to become more important to come up with the optimal operation stage of ventilation system. In this study, the tunnel ventilation dynamic simulation program had been developed. it is used to calculate the unsteady-state tunnel air velocity and concentration of pollutants according to the assumed average day traffic profile and summarize the energy consumption for the operation of ventilation system. And the operation energy consumption for the electric precipitation system and vertical vent shaft system are evaluated and compared in various operation mode. As the results of this study, the optimal operation stage for these ventilation system are provided.

• Journal of Environmental Health Sciences
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• v.39 no.6
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• pp.541-549
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• 2013

Objectives: We analyzed the characteristics of hazardous air pollutants (HAPs) in road tunnels in Seoul. Methods: Particle matter ($PM_{10}$), elemental carbon (EC), organic carbon (OC), and 16 species of polycyclic aromatic hydrocarbons (PAHs) in two road tunnels (NS tunnel and HJ tunnel) were sampled and analyzed from 2007 to 2011. Results: Levels of $PM_{10}$ and carbon ingredients which were mainly emitted from diesel-fueled vehicles showed a declining tendency in both road tunnels. PAHs levels in HJ were declining slightly while PAHs levels in the NS tunnel fluctuated considerably and showed an increasing tendency. Conclusions: These results suggested that the abatement project of diesel vehicle emissions by the Seoul metropolitan government from 2007 has had an impact on the reduction of DVE into the air, though there exist many things to consider for analyses.

• Wind and Structures
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• v.24 no.1
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• pp.1-24
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• 2017

Wind environment in urban residential areas is an important index to consider when evaluating the living environment. However, due to the complexity of the flow field in residential areas, it is difficult to specify the correct inflow boundary conditions in the large eddy simulation (LES). In this paper, the weighted amplitude wave superposition (WAWS) is adopted to simulate the fluctuating velocity data, which satisfies the desired target wind field. The fluctuating velocity data are given to the inlet boundary of the LES by developing an UDF script, which is implemented into the FLUENT. Then, two numerical models - the empty numerical wind tunnel model and the numerical wind tunnel model with spires and roughness elements are established based on the wind tunnel experiment to verify the present method. Finally, the turbulence generation approach presented in this paper is used to carry out a numerical simulation on the wind environment in an urban residential area in Lisbon. The computational results are compared with the wind tunnel experimental data, showing that the numerical results in the LES have a good agreement with the experimental results, and the simulated flow field with the inlet fluctuations can generate a reasonable turbulent wind field. It also shows that strong wind velocities and turbulent kinetic energy occur at the passageways, which may affect the comfort of people in the residential neighborhood, and the small wind velocities and vortexes appear at the leeward corners of buildings, which may affect the spreading of the pollutants.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.3
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• pp.293-304
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• 2022

Recently, the frequency of installation of ventilation towers is increasing due to the planning and construction of underground roads and long tunnel. In this study, implications and points for improvement were considered through investigation and analysis of the installation standards related to ventilation towers in tunnels and analysis of ventilation tower installation cases in domestic and overseas tunnel case study. As a result of this study, when selecting the location and height of the ventilation tower, it is recommended to determine the final ventilation tower type through a consultation process with residents, considering the environmental impact caused by the emission of pollutants, the harmonious arrangement with the surrounding landscape, and the efficient use of the above-ground site nearby ventilation tower. In addition, from the design stage, it is judged that a detailed review of reducing the height of the ventilation tower through air quality simulation is necessary for natural harmony with the surrounding topography and to prevent civil complaints.