• Journal of Ocean Engineering and Technology
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• v.32 no.6
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• pp.474-484
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• 2018

In this study, a new numerical modeling system was proposed to predict oil spills, which increasingly occur at sea as a result of abnormal weather conditions such as global warming. The hydrodynamic conditions such as the flow velocity needed to calculate oil dispersion were estimated using a three dimensional hydrodynamic model based on the Navier-Stokes equation, which considered all of the physical variations in the vertical direction. This improved the accuracy compared to those estimated by the conventional shallow water equation. The advection-diffusion model for the spilled oil was combined with the hydrodynamic model to predict the movement and fate of the oil. The effects of absorption, weathering, and wind were also considered in the calculation process. The combined model developed in this study was then applied to various test cases to identify the characteristics of oil dispersion over time. It is expected that the developed model will help to establish initial response and disaster prevention plans in the event of a nearshore oil spill.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.57-59
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• 2002

The dissolution process of NAPLs is significantly important in predicting the transport and/or fate of the contaminants and designing remedial systems. In this research, experimental observations on dissolution of TCE pool under various hydrodynamic conditions are done using an aquifer model. Hydrodynamic parameters such as linear pore velocity and dispersion coefficient are estimated from the results of preliminary tracer tests using bromide as conservative tracer before doing the TCE dissolution experiments. It is found that hydrodynamic parameters are distinctly affected by the clay lens imbeded in the aquifer model. Nonequilibrium and transient dissolution rates are observed from the results of TCE dissolution experiments.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.3
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• pp.100-109
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• 1995

A new Hydrodynamic model for the high energy tail electrons(Tail Electron Hydrodynamic Model : TEHD) is developed using the moment method. The Monte Carlo method is applied to a $n^{+}-n^{-}-n^{+}$ device to calibrate the TEHD equations. the discretization method and numerical procedures are explained. New models for the impact ionization and injection into the gate oxide using the tail electron density are proposed. The simulated results of the impact ionization rate for a $n^{+}-n^{-}-n^{+}$ device and MOSFET devices, and the gate injection experiment are shown to give good agreement with the Monte Carlo simulation and the measurements.

• Atmosphere
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• v.30 no.2
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• pp.155-167
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• 2020

In order to produce more detailed and accurate information of river discharge and freshwater discharge, global high-resolution hydrodynamic model (CaMa-Flood) is applied to an operational land surface model of global seasonal forecast system. In addition, bias correction to grid runoff for the hydrodynamic model is attempted. CaMa-Flood is a river routing model that distributes runoff forcing from a land surface model to oceans or inland seas along continentalscale rivers, which can represent flood stage and river discharge explicitly. The runoff data generated by the land surface model are bias-corrected by using composite runoff data from UNH-GRDC. The impact of bias-correction on the runoff, which is spatially resolved on 0.5° grid, has been evaluated for 1991~2010. It is shown that bias-correction increases runoff by 30% on average over all continents, which is closer to UNH-GRDC. Two experiments with coupled CaMa-Flood are carried out to produce river discharge: one using this bias correction and the other not using. It is found that the experiment adapting bias correction exhibits significant increase of both river discharge over major rivers around the world and continental freshwater discharge into oceans (40% globally), which is closer to GRDC. These preliminary results indicate that the application of CaMa-Flood as well as bias-corrected runoff to the operational global seasonal forecast system is feasible to attain information of surface water cycle from a coupled suite of atmospheric, land surface, and hydrodynamic model.

• International Journal of Naval Architecture and Ocean Engineering
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• v.2 no.1
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• pp.14-23
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• 2010

A numerical model was developed for simulating a three-dimensional multilayer hydrodynamic and thermodynamic model in domains with irregular bottom topography. The model was designed for examining the interactions between flow and topography. The model was based on the three-dimensional Navier-Stokes equations and was solved using the fractional step method, which combines the finite difference method in the horizontal plane and the finite element method in the vertical plane. The numerical techniques were described and the model test and application were presented. For the model application to the northern part of Ariake Sea, the hydrodynamic and thermodynamic results were predicted. The numerically predicted amplitudes and phase angles were well consistent with the field observations.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.122-131
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• 1993

In this paper, we have developed a submicron Si MOSFET simulator, which is physically based on the hydrodynamic energy transport mode. The simulator was used to investigate the nonstationary transport effects and the transient phenomena in submicron Si MOSFET's. It is found that the velocity overshoot and the carrier heating are dominant transport mechanism near the drain end of the channel and the transient phenomena is more retained in a long channel MOSFET.

• Journal of Environmental Science International
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• v.15 no.10
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• pp.951-960
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• 2006

The eco-hydrodynamic model was used to estimate the environmental capacity in Gamak Bay. It is composed of the three-dimensional hydrodynamic model for the simulation of water flow and ecosystem model for the simulation of phytoplankton. As the results of three-dimensional hydrodynamic simulation, the computed tidal currents are toward the inner part of bay through Yeosu Harbor and the southern mouth of the bay during the flood tide, and being in the opposite direction during the ebb tide. The computed residual currents were dominated southward flow at Yeosu Harbor and sea flow at mouth of bay, The comparison between the simulated and observed tidal ellipses at three station showed fairly good agreement. The distributions of COD in the Gamak bay were simulated and reproduced by an ecosystem model. The simulated results of COD were fairly good coincided with the observed values within relative error of 1.93%, correlation coefficient(r) of 0.88. In order to estimate the environmental capacity in Gamak bay, the simulations were performed by controlling quantitatively the pollution loads with an ecosystem model. In case the pollution loads including streams become 10 times as high as the present loads, the results showed the concentration of COD to be $1.33{\sim}4.74mg/{\ell}(mean\;2.28mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality In case the pollution loads including streams become 30 times as high as the present loads, the results showed the concentration of COD to be $1.38{\sim}7.87mg/{\ell}(mean\;2.97mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality. In case the pollution loads including streams become 50 times as high as the present loads, the results showed the concentration of COD to be $1.44{\sim}9.80mg/{\ell}(mean\;3.56mg/{\ell})$, which is the third class criterion of Korean standards for marine water quality.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.1-6
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• 2002

The integration of Geographic Information Systems (GIS) with the hydrodynamic model was conducted in order to revitalize the use of geographical information and to aid in the understanding of tidal circulation patterns. A 2D finite difference numerical model was used to simulate n tidal circulation in the Suyoung Bay in Busan, Korea. CIS, especially the ArcView S/W is used to input the data of the numerical model, and is also used for the visualization of model outputs on the ground in the loosely coupled method. In this paper, an electronic navigational chart (ENC), which provides more accurate information in the ocean and coastal areas than any other digital information, is used as a base map for this integration. With the help of GIS, the integration can support th understanding of oceanographic information.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.386-392
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• 2018

It is necessary to predict hydrodynamic derivatives when assessing the maneuverability of a submarine. The force and moment acting on the vehicle may affect its motion in various modes. Conventionally, the derivatives are determined by performing captive model tests in a towing tank or applying a system identification method to the free running model test. However, a computational fluid dynamics (CFD) method has also become a possible tool to predict the hydrodynamics. In this study, virtual captive model tests for a full-scale submarine were conducted by utilizing a Reynolds-averaged Navier-Stokes solver in ANSYS FLUENT version 18.2. The simulations were carried out at design speed for various modes of motion such as straight forward, drift, angle of attack, deflection of the rudder, circular, and combined motion. The hydrodynamic force and moment acting on the submarine appended rudders and stern stabilizers were then obtained. Finally, hydrodynamic derivatives were determined, and these could be used for evaluating the maneuvering characteristics of the submarine in a further study.

• Journal of Ship and Ocean Technology
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• v.7 no.4
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• pp.16-31
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• 2003

The finite volume based multi-block RANS code, WAVIS developed at KRISO, is used to simulate the turbulent flows around a submarine with the realizable $\textsc{k}-\varepsilon$ turbulence model. RANS methods are verified and validated at the level of validation uncertainty 1.54% of the stagnation pressure coefficient for the solution of the turbulent flows around SUBOFF submarine model without appendages. Another SUBOFF configuration, axisymmetric body with four identical stem appendages, is also computed and validated with the experimental data of the nominal wake and hydrodynamic coefficients. The hydrodynamic forces and moments for SUBOFF model and a practical submarine are predicted at several drift and pitch angles. The computed results are in extremely good agreement with experimental data. Furthermore, it is noteworthy that all the computations at the present study were carried out in a PC and the CPU time required for 2.8 million grids was about 20 hours to get fully converged solution. The current study shows that CFD can be a very useful and cost effective tool for the prediction of the hydrodynamic performance of a submarine in the basic design stage.