DEVELOPMENT OF TWO-PHASE FLOW ANALYSIS MODEL FOR ANALYSIS OF RAINWATER STORAGE AND DRAINAGE TUNNEL Proceedings of the IAHR World Congress, 2025
An Experimental Study of Flow and Turbulence Properties near the Rising Sector Gate Mouth Considering the Gate Opening with a PIV Measuring System Chang Geun Song, Sung Won Park, Jaehyun Shin Water Switzerland, 2024 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.
Integrated Prediction Model for Upstream Reservoir Sedimentation in a Weir: A Comprehensive Analysis Using Numerical and Experimental Approaches Jungkyu Ahn, Chang Geun Song, Sung Won Park Water Switzerland, 2024 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.
Evaluation of Three-Dimensional Environmental Hydraulic Modeling in Scour Hole Thi Hoang Thao Nguyen, Sungwon Park, Dongmin Jang, Jungkyu Ahn Applied Sciences Switzerland, 2022 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.
Evaluation of infiltration rainwater drainage (Ird) system with fully 3-d numerical simulation approach Jungkyu Ahn, Seongil Yeom, Sungwon Park, Thi Hoang Thao Nguyen Applied Sciences Switzerland, 2021 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.
Optimal strategy to tackle a 2D numerical analysis of non-uniform flow over artificial dune regions: A comparison with bibliography experimental results Jungkyu Ahn, Jaelyong Lee, Sung Won Park Water Switzerland, 2020 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.
Properties of Rising Multiple CO2 Droplets under Contamination of SO2: Understanding Scenarios of Leakage to Seawater Thi Hoang Thao Nguyen, Sung Won Park, Jungkyu Ahn Journal of Coastal Research, 2020 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.
Longitudinal distribution of bed shear stress in stabilized scoured hole at the downstream of the river bed protection River Flow 2016 Iowa City Usa July 11 14 2016, 2016
Numerical simulation of heterogeneous mixing in meandering channels 34th IAHR Congress 2011 Balance and Uncertainty Water in A Changing World Incorporating the 33rd Hydrology and Water Resources Symposium and the 10th Conference on Hydraulics in Water Engineering, 2011
Two dimensional experimental and numerical analyses of flow and pollutant transport in meandering channel Environmental Hydraulics Theoretical Experimental and Computational Solutions Proceedings of the International Workshop on Environmental Hydraulics Iweh 2009, 2010
