• Environmental Engineering Research
• /
• v.11 no.3
• /
• pp.164-171
• /
• 2006

Numerical modeling of the flow velocity fields for the near corona wire electrohydrodynamic (EHD) flow was conducted. The steady, two-dimensional momentum equations have been computed for a wire-plate type electrostatic precipitator (ESP). The equations were solved in the conservative finite-difference form on a fine uniform rectilinear grid of sufficient resolution to accurately capture the momentum boundary layers. The numerical procedure for the differential equations was used by SIMPLEST algorithm. The Phoenics (Version 3.5.1) CFD code, coupled with Poisson's electric field, ion transport equations and the momentum equation with electric body force were used for the numerical simulation and the Chen-Kim ${\kappa}-{\varepsilon}$ turbulent model numerical results that an EHD secondary flow was clearly visible in the downstream regions of the corona wire despite the low Reynolds number for the electrode ($Re_{cw}=12.4$). Secondary flow vortices caused by the EHD increases with increasing discharge current or EHD number, hence pressure drop of ESP increases.

• Journal of Korean Society on Water Environment
• /
• v.36 no.4
• /
• pp.300-313
• /
• 2020

The Bayesian approach can be used to estimate hydrologic model parameters from the prior expert knowledge about the parameter values and the observed data. The purpose of this study was to compare the performance of the two Bayesian methods, the Metropolis-Hastings (MH) algorithm and the Generalized Likelihood Uncertainty Estimation (GLUE) method. These two methods were applied to the TANK model, a hydrological model comprising 13 parameters, to examine the uncertainty of the parameters of the model. The TANK model comprises a combination of multiple reservoir-type virtual vessels with orifice-type outlets and implements a common major hydrological process using the runoff calculations that convert the rainfall to the flow. As a result of the application to the Nam River A watershed, the two Bayesian methods yielded similar flow simulation results even though the parameter estimates obtained by the two methods were of somewhat different values. Both methods ensure the model's prediction accuracy even when the observed flow data available for parameter estimation is limited. However, the prediction accuracy of the model using the MH algorithm yielded slightly better results than that of the GLUE method. The flow duration curve calculated using the limited observed flow data showed that the marginal reliability is secured from the perspective of practical application.

• Environmental Engineering Research
• /
• v.24 no.1
• /
• pp.107-116
• /
• 2019

Nitrogen removal, nitrous oxide ($N_2O$) emission and microbial community in sequencing batch and continuous-flow intermittent aeration processes were investigated. Two sequencing batch reactors (SBRs) and two continuous-flow multiple anoxic and aerobic reactors (CMRs) were operated under high dissolved oxygen (DO) (SBR-H and CMR-H) and low DO (SBR-L and CMR-L) concentrations, respectively. Nitrogen removal was enhanced under CMR and low DO conditions (CMR-L). The highest total inorganic nitrogen removal efficiency of 91.5% was achieved. Higher nitrifying and denitrifying activities in SBRs were observed. CMRs possessed higher $N_2O$ emission factors during nitrification in the presence of organics, with the highest $N_2O$ emission factor of 60.7% in CMR-L. SBR and low DO conditions promoted $N_2O$ emission during denitrification. CMR systems had higher microbial diversity. Candidatus Accumulibacter, Nitrosomonadaceae and putative denitrifiers ($N_2O$ reducers and producers) were responsible for $N_2O$ emission.

• Journal of Environmental Science International
• /
• v.9 no.5
• /
• pp.397-402
• /
• 2000

Numerical simulation model using nesting method and considering topographic features was developed to predict atmospheric environments atmospheric flow temperature and diffusion of air pollutants in Kwangyang bay where having complex areas of point sources Korea. In addition developed simulation model was used tracing of spreading range of pollutants when a gas leaks suddenly from Yeo-cheon industrial complex. by comparing the measured and calculated data on atmospheric flow temperature and diffusion of air pollutants the results showed that this model can be well applied and complicated topography affected the diffusion of air pollutants.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2003.05b
• /
• pp.277-278
• /
• 2003

Cyclone separators are widely used for cleaning gas streams or for catalyst recovery. For many years, the complexity of the gas flow pattern in cyclones has been a matter of many experimental and theoretical work. At present, precise flow measurements have been performed by means of LDA and hot-wire anemometry (Patterson and Munz, 1996; Hoekstra et al., 1999; Peng et al., 2002). In the theoretical work, Computational fluid dynamics (CFD) codes are frequently employed for simulating cyclone gas-particle flows(Hoekstra et al., 1999). (omitted)

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.2B
• /
• pp.147-154
• /
• 2011

Physical habitat assessment models based on Instream Flow Incremental Methodology have been developed as a decision making tool to estimate appropriate discharge for environmental flow and water use management. These models, however, require extensive knowledge on various academic disciplines, complicated input data, and empirical data. We propose a Simplified Habitat (SIMHAB) simulation model for the estimation of physical structure of fish habitat and environmental flow at the planning stage. SIMHAB is applied to a river system for which physical and ecological data are available, and its applicability is investigated. Simulated results appeared to be similar to field survey data and those of such models as PHABSIM and River2D. However, SIMHAB requires much less input data. As such, the proposed model, SIMHAB can easily be applicable to river restoration projects including designing of physical habitat, estimation of environmental flow, and water resource management.

• Journal of Environmental Science International
• /
• v.21 no.1
• /
• pp.31-39
• /
• 2012

The objective of this study is to provide pollutant loads delivery ratio for flow duration in Oenam-cheon watershed, which is upstream watershed of Juam Lake. To calculate the delivery ratio by flow duration, rating curves and discharge-loads curves using measured data were established, then Flow Duration Curve(FDC) and pollutant loads delivery ratio curves were constructed. The results show that the delivery ratios for $BOD_5$ for abundant flow($Q_{95}$), ordinary flow($Q_{185}$), low flow($Q_{275}$), and drought flow($Q_{355}$) were 23.9, 12.7, 7.1, and 2.9%, respectively. The delivery ratios of same flow regime for T-N were 58.4, 31.2, 17.2 and 7.1%, respectively. While, the delivery ratios T-P were 17.3, 7.5, 3.4, and 1.1% respectively. In general, delivery ratio of high flow condition showed higher value due to the influence of nonpoint source pollution. Based on the study results, generalized equations were developed for delivery ratio and discharge per unit area, which could be used for ungaged watershed with similar pollution sources.

• Journal of Korean Society of Environmental Engineers
• /
• v.39 no.4
• /
• pp.180-185
• /
• 2017

For the management of mercury-containing products, the products were selected to do material flow analysis in preference of not having selected in previous studies. Domestically mercury have been added to pigment for prevention of bacterial growth. So, in this study paint containing pigment was selected as a target. 71 samples of paint products collected in 2014 and data of 38 samples of wastes (dust, sludge, paint) analyzed in 2010 were used in material flow analysis. The result shows that mercury was 0~0.25 mg/kg in products and 0.23~0.69 mg/kg in the wastes. In the material flow analysis, the amount of flow in the process of distribution was 10.06 kg/year, but the amount of flow in disposal like a landfill, incineration and recycling was much than distribution as 25.27 kg/year. It was caused by different sampling period between collecting products and data of wastes. Therefore, It could be possible to be affected from regulation by RoHS like decreasing usage of mercury in paint products or eradicated in the industry. Mercury contents in current paint products are very low to affect discharging to the environment.

• Journal of Environmental Science International
• /
• v.20 no.1
• /
• pp.107-118
• /
• 2011

While the assessment of mean flow field is very important to characterize the hydrodynamic aspect of the flow regime in river, the conventional methodologies have required very time-consuming efforts and cost to obtain the mean flow field. The paper provides an efficient technique to quickly assess mean flow field by developing and applying spatial averaging method utilizing repeatedly surveyed acoustic Doppler current profiler(ADCP)'s cross-sectional measurements. ADCP has been widely used in measuring the detailed velocity and discharge in the last two decades. In order to validate the proposed spatial averaging method, the averaged velocity filed using the spatial averaging was compared with the bench-mark data computed by the time-averaging of the consistent fix-point ADCP measurement, which has been known as a valid but a bit inefficient way to obtain mean velocity field. The comparison showed a good agreement between two methods, which indicates that the spatial averaging method is able to be used as a surrogate way to assess the mean flow field. Bed shear stress distribution, which is a derived hydrodynamic quantity from the mean velocity field, was additionally computed by using both spatial and time-averaging methods, and they were compared each other so as to validate the spatial averaging method. This comparison also gave a good agreement. Therefore, such comparisons proved the validity of the spatial averaging to quickly assess mean flow field. The mean velocity field and its derived riverine quantities can be actively used for characterizing the flow dynamics as well as potentially applicable for validating numerical simulations.

• Journal of Environmental Science International
• /
• v.26 no.9
• /
• pp.1031-1043
• /
• 2017

Recently severe drought caused the water shortage around the western parts of Chungcheongnamdo province, South Korea. A Diversion tunnel from the Geum river to the Boryong dam, which is the water supply dam for these areas has been proposed to solve this problem. This study examined hydraulic impacts on the Geum river associated with the diversion plan assuming the severe drought condition of 2015 would persist for the simulation period of 2016. The hydraulic simulation model was verified using hydrologic and hydraulic data including hourly discharges of the Geum river and its 8 tributaries, fluctuation of tidal level at the mouth of the river, withdrawals and return flows and operation records of the Geum river barrage since Feb. 1, 2015 through May 31, 2015. For the upstream boundary condition of the Geum river predicted inflow series using the nonlinear regression equation for 2015 discharge data was used. In order to estimate the effects of uncertainty in inflow prediction to the results total four inflow series consisting of upper limit flow, expected flow, lower limit flow and instream flow were used to examine hydraulic impacts of the diversion plan. The simulation showed that in cases of upper limit and expected flows there would be no problem in taking water from the Geum river mouth with a minimum water surface level of EL(+) 1.44 m. Meanwhile, the simulation also showed that in cases of lower limit flow and instream flow there would be some problems not only in taking water for water supply from the mouth of the Geum river but also operating the diversion facility itself with minimum water surface levels of EL(+) 0.94, 0.72, 0.43, and 0.14 m for the lower limit flow without/with diversion and the instream flow without/with diversion, respectively.