Sung Won Park
@inu.ac.kr
Incheon National University
RESEARCH, TEACHING, or OTHER INTERESTS
Water Science and Technology, Civil and Structural Engineering, Computer Science Applications
FUTURE PROJECTS
Hydraulic analysis of gated flow
Applications Invited
Prediction of local scour hole dimensions
Applications Invited
Analysis of field monitoring on bed erosion behind the weir gate
Applications Invited
Scopus Publications
Scopus Publications
Chang Geun Song, Sung Won Park, and Jaehyun Shin
MDPI AG
Hydraulic structures, such as movable weir gates, are widely installed in rivers and streams for various purposes. Among these is the rising sector gate, which is the focus of this study. This research investigated how different gate openings affect flow velocity and turbulence distributions at the gate mouth. A hydraulic analysis of flow and turbulence characteristics near the mouth of a rising sector gate model was conducted through laboratory experiments with various flow conditions and gate openings utilizing a Particle Image Velocimetry (PIV) system. Experimental tests were carried out with two gate-opening angles (30 and 45 degrees). The PIV measurements revealed significant variations in flow velocity and turbulence properties in response to the gate openings and flow conditions. Notably, in the vicinity of the gate mouth, where the flow regime changes rapidly between the upstream and downstream regions, the turbulence properties in the upstream part of the gate mouth were more than twice those in the downstream part. Additionally, the streamwise distribution of depth-averaged relative turbulence intensity was analyzed. The results showed that the depth-averaged relative turbulence intensity decreased by nearly half as the gate opening increased from 30 to 45 degrees, with the lowest values observed at the gate mouth, followed by an increase downstream. A functional relationship between the maximum flow velocity at the gate mouth during underflow operation and the Froude number was established to guide practical gate operation in the field.
Jungkyu Ahn, Chang Geun Song, and Sung Won Park
MDPI AG
In this study, a new empirical equation was established to predict the sedimentation volume resulting from the construction of a multi-purpose weir or low-head dam using experimental approaches. Applying the 1-D numerical model (STAFF), which is based on Exner’s equation, 2545 cases were simulated and laboratory experiments were conducted with various sediment particle sizes, channel slopes, inlet discharge, and outlet water elevation. Short-term predictions were conducted through laboratory experiments with movable bed, and the results indicated that dimensionless unit stream power and the Shields parameter exhibited the most significant correlation with dimensionless deposition volume. In particular, we analyzed the phenomenon in which the backwater effect and reservoir delta. Using a multiple regression approach, the developed empirical equation was validated for predicting sedimentation in the upstream reservoir of the weir.
Thi Hoang Thao Nguyen, Sungwon Park, Dongmin Jang, and Jungkyu Ahn
MDPI AG
The main goal of this study was comparing the performance of an open-source code OpenFOAM and a commercial software Ansys Fluent in simulating the turbulent flow through a scour hole developed in a sand bed channel, which helps to give a hint in choosing the appropriate calculating tool. Both models were set with the same mesh and as similar as possible numerical settings, with RANS turbulence modeling, applying the k-ωSST model, in transient simulations. The results of flow pattern, velocity, and turbulence properties were collected and compared with laboratory experimental data. The analyzed results showed that, although both of the two models cannot perfectly reproduce the values from a laboratory experiment, they can quite well capture the flow in scour hole near the wall, with a bit higher performance coming from the OpenFOAM model application.
Jungkyu Ahn, Seongil Yeom, Sungwon Park, and Thi Hoang Thao Nguyen
MDPI AG
Water scarcity can mean scarcity in availability due to physical shortage, or scarcity in access due to the failure of institutions to ensure a continuously regular supply or due to a lack of adequate infrastructure. Water scarcity will be exacerbated as rapidly growing urban areas place heavy pressure on water resources. To solve these problems, various solutions have been applied, but a fundamental solution has not been applied. Recently, a researched and developed infiltration rainwater drainage (IRD) system is being applied with consideration of its applicability. In this study, features of surface runoff and infiltration according to various flow patterns were analyzed using a three-dimensional CFD (Computational Fluid Dynamics) model for calculating water flow in the IRD system. To estimate the optimal setup, a permeability test and scaled model simulation were performed. The runoff characteristics of the IRD system with respect to rainfall intensity and duration were analyzed with dimensionless variables. With the prototype model, the drainage characteristics of the IRD system were analyzed over time using the hydrological curves. From the simulated results, it was found that the IRD system analyzed in this study was appropriate in the field by comparative analysis with the existing system based on peak runoff, internal storage, and lag time. Therefore, by applying the IRD system in the future, it is expected that the IRD has benefits, such as delayed lag time, surface runoff decrease, and an attenuation of the peak runoff.
Dongmin Jang, Wonkyun Joo, Chang-Hoo Jeong, Wonsu Kim, Sung Won Park, and Yoojin Song
MDPI AG
The authors wish to make the following corrections to this paper [...]
Jungkyu Ahn, Jaelyong Lee, and Sung Won Park
MDPI AG
Flow simulation over a dune requires the proper input of roughness coefficients. This study analyzed a numerical simulation of open-channel turbulent flow over two-dimensional fixed dunes to reveal the effect of roughness on the dune bottom, and to determine the optimized combination of the turbulence scheme and the roughness height formula. The most appropriate roughness values and turbulence models were applied using Reynolds-averaged Navier–Stokes models. Seven methods were chosen to estimate the bed roughness properties at the inlet boundary section. The results of all cases calculated with the OpenFOAM toolbox were compared with laboratory experimental data for model validation. The performances of all bed roughness variations were evaluated according to the stream-wise and depth-wise directions with nondimensional values. Consequently, it was revealed that the combination of bottom roughness length scale at the inlet boundary and the k-ω shear-stress transport (SST) model was the most suitable for the flow separation zone and turbulent properties near the channel bottom.
Thi Hoang Thao Nguyen, Sung Won Park, and Jungkyu Ahn
Coastal Education and Research Foundation
ABSTRACT Nguyen, T.H.T.; Park, S.W., and Ahn, J., 2020. Properties of rising multiple CO2 droplets under contamination of SO2: Understanding scenarios of leakage to seawater. Journal of Coastal Research, 36(4), 805–811. Coconut Creek (Florida), ISSN 0749-0208. Research on impacts of impurities on the rising of liquid droplets in other liquids is still quite limited, especially when it comes to the behavior of multiple particles. The properties of rising multiple CO2 droplets under contamination of SO2 are investigated in a scenario in which they may leak to the seawater from a pipeline or facility in a Carbon Capture and Storage (CCS) project. The interaction between droplets and their rising properties such as velocity were examined. The results of numerical simulation show that the presence of SO2 changes particles' shape and their rising velocities significantly compared with the single droplet case. This SO2 contamination also caused the repulsion of impure particles even when they were placed close to each other, which was observed as coalescence in the pure CO2 case. Results will help in understanding the impacts of contamination on the rise of multiple CO2 droplets such as that leaked by future CCS operations.
Jungkyu Ahn and Sung Won Park
Elsevier BV
Junkyu Ahn and Sung Won Park
Elsevier BV
Dongmin Jang, Wonkyun Joo, Chang-Hoo Jeong, Wonsu Kim, Sung Park, and Yoojin Song
MDPI AG
Typhoons can often cause inundation in lower coastal cities by inducing strong surges and waves. Being affected by typhoon annually, the coastal cities in South Korea are very vulnerable to typhoons. In 2016, a typhoon ‘CHABA’, with a maximum 10 min sustained wind speed of about 50 m/s and a minimum central pressure of 905 hPa, hit South Korea, suffering tremendous damage. In particular, ‘CHABA’-induced coastal inundation resulted in serious damage to the coastal area of Busan where a lot of high-rise buildings and residential areas are concentrated, and was caused by the combined effect of tide, surge, and wave. The typhoon-induced surge raised sea levels during high tide, and the strong wave with a long period of more than 10 s eventually led to the coastal inundation at the same time. The present research focuses a numerical downscaling considering the effects of tide, surge and wave for coastal inundation induced by Typhoon ‘CHABA’. This downscaling approach applied several numerical models, which are the Weather Research and Forecasting model (WRF) for typhoon simulation, the Finite Volume Community Ocean Model (FVCOM) for tide and surge simulation, and the Simulating WAve Nearshore (SWAN) for wave simulation. In a domain covering the Korean Peninsula, typhoon-induced surges and waves were simulated applying the results simulated by WRF as meteorological conditions. In the downscaled domain ranged near the coastal area of Busan, the coastal inundation was simulated blending a storm tide height and an irregular wave height obtained from the domain, in which each height has 1 s interval. The irregular wave height was calculated using the significant wave height and peak period. Through this downscaling study, the impact of storm tide and wave on coastal inundation was estimated.
Jungkyu Ahn, Yeji Na, and Sung Won Park
Springer Science and Business Media LLC
Sung Won Park, Jin Hwan Hwang, and Jungkyu Ahn
MDPI AG
Local scour at the downstream of the river bed protection is one of the most important parameters for the design criteria and sustainable management of the hydraulic structures. Previously, various researches on its process in the equilibrium state have been suggested with experimental and numerical approaches. In this study, relatively long-term laboratory experiments of local scouring at the downstream of fixed bed in an open channel were conducted with mono-granular sediment bed and analyzed about maximum scour depth and its temporal development. In particular, we conducted experiments with relatively low Froude number (less than 0.5) and their duration of tests was exceeded over 700 hours. We modified the relationship between the dimensionless time and length scales of the maximum scour depth of the local scour hole based on the turbulent shear layer thickness. A new functional relationship between dominant factors and the maximum scour depth in the equilibrium state were suggested and compared with previously suggested formula. Also, from the results by nonlinear regression, Froude number was founded as a dominant factor on the prediction of equilibrium maximum scour depth.
Thi Hoang Thao Nguyen, Sung Won Park, and Jungkyu Ahn
Coastal Education and Research Foundation
ABSTRACT Nguyen, T.H.T.; Park, S.W., and Ahn, J., 2020. Numerical method to determine upstream scour slope in relation to turbulence and particle movement. Journal of Coastal Research, 36(1), 189–195. Coconut Creek (Florida), ISSN 0749-0208. Several studies have been conducted to investigate the behavior of scour hole, which happens naturally at the end of the bed protections in the streams and rivers, because this phenomenon can result in the instability or destruction of man-made structures in the area. Some formulas or equations were introduced to calculate the upstream scour slope, one of the most important scour properties, but the application shows some difficulty because of the lack of data. This paper presents a simple but reasonable method to find upstream scour slope with the employing of a numerical simulation, in particular by considering the relationship between turbulence and particle movement.
Jungkyu Ahn, Yeji Na, and Sung Won Park
Korean Society of Environmental Engineering
Currently, the waterfront facility was constructed in New Songdo City, South Korea. It has the various water leisure areas and especially an artificial urban canal with filtered seawater by re-circulating flow system. However, due to excessive amount of nutrients from seawater combined with complicated geometry, it is highly vulnerable to deterioration of water quality. In this study, flow characteristics and pollutant transport were analyzed with comprehensive numerical models, MIKE 3 FM and ECO-lab. Based on these numerical results, notable sampling points were selected for field measurements and comparison between modeling and measured results were conducted. In addition, the integrated water quality evaluation index, Water Quality Index was applied to analyze various water quality issues. We also set up scenarios to control the two kinds of water quality factors, dissolved oxygen (DO), and total phosphorus (TP). As a result, the effect of 20% reduction of TP was less than 10% and it was almost ineffective for a year but it was reduced by up to 40% in case of scenario which DO is increased by 20%. Therefore, it was recommended to control the DO concentration, usually by applying re-aeration facility, rather than TP in artificial urban canal with seawater.
Thi Hoang Thao Nguyen, Jaelyong Lee, Sung Won Park, and Jungkyu Ahn
Springer Science and Business Media LLC
Thi Nguyen, Jungkyu Ahn, and Sung Park
MDPI AG
Local scour occurs around hydraulic structures such as piers, bed protections, and dikes. In this study, the turbulent flow around a scour hole downstream of a fixed bed protection was investigated. Numerical modeling with OpenFOAM was applied to compute the flow velocity and turbulent kinetic energy with respect to flow conditions by changing water depth. A proper computational grid size and time step for simulations are suggested. Three typical turbulent models, k − ε , k − ω , and k − ω S S T , were considered for simulating the flow around a scour hole. The performances of the three models were evaluated by comparing them with numerical and laboratory experimental results. Mean flow velocity profiles computed by the three turbulent schemes are generally in good agreement with laboratory measurements. However, k − ω has a limitation in simulating reversal flow in the scour hole, and the k − ε model does not predict turbulent kinetic energy well near the bottom. Thus, this study found that the most suitable turbulent model for simulating flow around a scour hole downstream of a fixed bed protection is the k − ω S S T model.