• International Journal of Naval Architecture and Ocean Engineering
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• 제8권1호
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• pp.22-37
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• 2016

This article investigates numerical modeling of surface piercing propeller (SPP) in unsteady open water condition using boundary element method. The home code based on BEM has been developed for the prediction of propeller performance, unsteady ventilation pattern and cross flow effect on partially submerged propellers. To achieve accurate results and correct behavior extraction of the ventilation zone, finely mesh has generated around the propeller and especially in the situation intersection of propeller with the free surface. Hydrodynamic coefficients and ventilation pattern on key blade of SPP are calculated in the different advance coefficients. The values obtained from this numerical simulation are plotted and the results are compared with experiments data and ventilation observations. The predicted ventilated open water performances of the SPP as well as ventilation pattern are in good agreement with experimental data. Finally, the results of the BEM code/experiment comparisons are discussed.

• 대한조선학회논문집
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• 제47권2호
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• pp.188-195
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• 2010

Green water load is an important parameter to be considered in designing a modern ship or offshore structures like FPSO and FSRU. In this research, a numerical simulation method for green water phenomenon is introduced. The Navier-Stokes equations and the continuity equation are used as governing equations. The equations are calculated using Finite Difference Method(FDM) in rectangular staggered grid system. To increase the numerical accuracy near the body, the Cartesian cut cell method is employed. The nonlinear free-surface during green water incident is defined by Marker-density method. The green waters on a box in regular waves are simulated. The simulation results are compared with other experimental and computational results for verification. To check the applicability to moving ship, the green water of the ship which is towed by uniform force in regular wave, is simulated. The ship is set free to heave and to surge.

• Ocean Systems Engineering
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• 제3권3호
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• pp.181-201
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• 2013

The main objective of this work is to investigate the sloshing behavior in a baffled and unbaffled three dimensional annular-sectored water pool (i.e., tank) which is located at dome region of the primary containment. Initially two case studies were performed for validation. In these case studies, the theoretical and experimental results were compared with numerical results and good agreement was found. After the validation of present numerical procedure, an annular-sectored water pool has been taken for numerical investigation. One sector is taken for analysis from the eight sectored water pool. The free surface is captured by Volume of Fluid (VOF) technique and the fluid portion is solved by finite volume method while the structure portions are solved by finite element approach. Baffled and un-baffled cases were compared to show the reduction in wave height under excitation. The complex mechanical interaction between the fluid and pool wall deformation is simulated using a partitioned strong fluid-structure coupling.

• Structural Engineering and Mechanics
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• 제80권5호
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• pp.523-538
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• 2021

The mechanical behaviour and stability of coal mining engineering underground is significantly affected by ground water. In this study, nuclear magnetic resonance imaging (NMRI) technique was employed to determine the water distribution characteristics in coal specimens during saturation process, based on which the functional rule for water distribution was proposed. Then, using discrete element method (DEM), an innovative numerical modelling method was developed to simulate water-weakening effect on coal behaviour considering moisture content and water distribution. Three water distribution numerical models, namely surface-wetting model, core-wetting model and uniform-wetting model, were established to explore the water distribution influences. The feasibility and validity of the surface-wetting model were further demonstrated by comparing the simulation results with laboratory results. The investigation reveals that coal mechanical properties are affected by both water saturation coefficient and water distribution condition. For all water distribution models, micro-cracks always initiate and nucleate in the water-rich area and thus lead to distinct macro fracture characteristics. With the increase of water saturation coefficient, the failure of coal tends to be less violent with less cracks and ejected fragments. In addition, the core-wetting specimen is more sensitive to water than specimens with other water distribution models.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1418-1419
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• 2007

In order to check the electric field distribution of polymer line post insulator, we performed electric field simulation according to state of water drops. Sea water is used to the contaminant. Electric field analysis is performed with change of contact angle, number and distance of water drops.

• 한국농공학회논문집
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• 제60권5호
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• pp.41-54
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• 2018

A method to account a detention in a rice paddy field in hydrologic modeling was tested at plot and watershed scales. Hydrologic Simulation Program - Fortran (HSPF) and its one of surface runoff modeling method, i.e Surface-Ftable, were used to simulate a inundated condition in a rice paddy culture for a study plot and basins in Saemangeum watershed. Surface-Ftable in HSPF defines surface runoff ratio with respect to surface water depth in a pervious land segment, which can be implemented to the feature of water management in a rice paddy field. A Surface-Ftable for paddy fields in Saemangeum watershed was developed based on the study paddy field monitoring data from 2013 to 2014, and was applied to Jeonju-chun and Jeongeup-chun basins which comprise 12% and 22% of paddy fields in the basins, respectively. Four gaging stations were used to calibrate and validate the watershed models for the period of 2009 and 2013. Model performed 7.13% and 9.68% in PBIAS, and 0.94 and 0.90 in monthly NSE during model calibrations at Jeonju and Jeongeup stations, respectively, while the models were validated its applicability at Hyoja and Gongpyung stations. The comparison of results with and without considering detention effect of paddy fields confirmed the validity of the Surface-Ftable method in modeling watersheds containing rice paddy fields.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.352-364
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• 2017

A novel 3D mathematical model for water film runback and icing on a rotating surface is established in this work, where both inertial forces caused by the rotation and shear forces due to the air flow are taken into account. The mathematical model of the water film runback and energy conservation of phase transition process is established, with a cyclical average method applied to simulate the unsteady parameters variation at angles of attack. Ice accretion on a conical spinner surface is simulated and the results are compared with the experimental data to validate the presented model. Then Ice accretion on a cowling surface is numerically investigated. Results show that a higher temperature would correspond to a larger runback ice area and thinner ice layer for glaze ice. Rotation would enhance the icing process, while it would not significantly affect the droplet collection efficiency for an axi-symmetric surface. In the case at angle of attack, the effect of rotation on ice shape is appreciable, ice would present a symmetric shape, while in a stationary case the shape is asymmetric.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2020년도 학술발표회
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• pp.172-172
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• 2020

In recent years, soil erosion has come to be regarded as an essential environmental problem in human life. Soil erosion causes various on- and off-site problems such as ecosystem destruction, decreased agricultural productivity, increased riverbed deposition, and deterioration of water quality in streams. To solve these problems caused by soil erosion, it is necessary to quantify where, when, how much soil erosion occurs. Empirical erosion models such as the Universal Soil Loss Equation (USLE) family models have been widely used to make spatially distributed soil erosion vulnerability maps. Even if the models detect vulnerable sites relatively well by utilizing big data related to climate, geography, geology, land use, etc. within study domains, they do not adequately describe the physical process of soil erosion on the ground surface caused by rainfall or overland flow. In other words, such models remain powerful tools to distinguish erosion-prone areas at the macro scale but physics-based models are necessary to better analyze soil erosion and deposition and eroded particle transport. In this study, the physics-based Surface Soil Erosion Model (SSEM) was upgraded based on field survey information to produce sediment yield at the watershed scale. The modified model (hereafter MoSE) adopted new algorithms on rainfall kinematic energy and surface flow transport capacity to simulate soil erosion more reliably. For model validation, we applied the model to the Doam dam watershed in Gangwon-do and compared the simulation results with the USLE outputs. The results showed that the revised physics-based soil erosion model provided more improved and reliable simulation results than the USLE in terms of the spatial distribution of soil erosion and deposition.

• 한국컴퓨터그래픽스학회논문지
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• 제26권5호
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• pp.1-13
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• 2020

본 논문에서는 흐르는 물에 의해 빙결 시뮬레이션 되어 방향성이 있는 얼음 형태를 안정적으로 모델링 할 수 있는 새로운 방법을 제시한다. 제안하는 얼음 모델링 프레임워크는 빙결 시뮬레이션에서 중요한 얼음의 성장 방향에 점성이 있는 유체의 흐름을 고려한다. 물 시뮬레이션 해법은 암시적 비압축성 유체 시뮬레이션에 새로운 점성 기법을 적용한 방법을 이용하고, 얼음의 방향과 글레이즈(Glaze) 효과는 제안하는 비등방성한 빙결 해법을 이용한다. 물 입자가 얼음 입자로 상태변화하는 조건은 습도와 물의 흐름에 따른 새로운 에너지 함수에 따라 계산된다. 습도는 오브젝트 표면의 가상 수막(Virtual water film)으로 근사되며, 유체의 흐름은 얼음의 성장 방향을 가이드하기 위해 우리의 비등방성한 빙결 해법에 통합된다. 결과적으로 점성이 있는 물의 흐름 방향에 따라 글레이즈와 방향성 있는 빙결 시뮬레이션 결과를 안정적으로 보여준다.

• 한국물환경학회지
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• 제29권2호
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• pp.247-258
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• 2013

A grid-based configuration of Land Surface Models (LSMs) coupled with a climate model can be advantageous in impact assessment of climate change for a large scale area. We assessed the applicability of Common Land Model (CoLM) to runoff and land surface temperature (LST) simulations at the domain that encompasses the Nakdong river basin. To establish a high resolution model configuration of a $1km{\times}1km$ grid size, both surface boundary condition and atmospheric inputs from the observed weather data in 2009 were adjusted to the same resolution. The Leaf Area Index (LAI) was collected from MODerate esolution Imaging Spectroradiometer (MODIS) and the downward short wave flux was produced by a nonstationary multi-site weather state model. Compared with the observed runoffs at the stations on Nakdong river, simulated runoffs properly responded to rainfall. The spatial features and the seasonal variations of the domain fairly well were captured in the simulated LSTs as well. The monthly and seasonal trend of LST were described well compared to the observations, however, the monthly averaged simulated LST exceeded the observed up to $2^{\circ}C$ at the 24 stations. From the results of our study, it is shown that high resolution LSMs can be used to evaluate not only quantity but also quality of water resources as it can capture the geographical features of the area of interest and its rainfall-runoff response.