• 한국해양공학회지
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• 제5권1호
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• pp.55-63
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• 1991

This study is to predict accurately the wave induced current accuring by the radiation stress which acts as the driving force around Nearshore structure. For the wave induced current, the depth integrated and time averaged governing equation of an unsteady nonlinear form is derived from the continuity and momentum equation of an incompressible fluid. Numerical solutions are obtained by a finite difference method for the governing equation. In the vicinity of a structure, computed flow patterns show good agreement with the hydraulic experimental data. The numerical results obtained by neglecting the convective term show a large change of alongshore and offshore current.

• Nuclear Engineering and Technology
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• 제31권2호
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• pp.236-255
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• 1999

An improved mechanistic model was developed to predict a convective boiling critical heat flux (CHF) in the vertical round tubes with uniform heat fluxes. The CHF formula for subcooled and low quality boiling was derived from the local conservation equations of mass, energy and momentum, together with appropriate constitutive relations. The model is characterized by the momentum balance equation to determine the limiting transverse interchange of mass flux crossing the interface of wall bubbly layer and core by taking account of the convective shear effect due to the frictional drag on the wall-attached bubbles. Comparison between the present model predictions and experimental CHF data from several sources shows good agreement over a wide range of How conditions. The present model shows comparable prediction accuracy with the CHF look-up table of Groeneveld et al. Also the model correctly accounts for the effects of flow variables as well as geometry parameters.

• 한국지하수토양환경학회지:지하수토양환경
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• 제9권3호
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• pp.20-26
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• 2004

2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD)로 오염된 토양의 현장 광분해 정화 과정에서 가장 중요한 이동 메커니즘인 지표에서의 증발 및 광분해에 의한 유기 용매의 이류 상방향 이동에 대한 수식화와 모델 개발을 수행하였다. 각 유체 분포에 대한 다상 유동 효과, 구동력으로서의 중력, k-S-p 관계의 정확한 묘사를 위한 van Genutchen 방정식을 포함한 유한요소법 기반의 수치 모델을 제안하였다. 실험실 규모의 비포화 토양 컬럼 내 용매 이동에 중요한 영향을 미치는 인자들을 조사하기 위하여 수행한 계산의 결과들을 제시하였다. 중력은 고투수성 토양의 유체 분포와 증발에 상당한 영향을 미쳤다. 토양의 종류 또한 증발 과정 중 유체 포화도 분포에 큰 영향을 미친다. 용매의 이류 이동량은 증발량이 증가할수록 초기 물 포화도가 감소할수록 증가하였다. 본 연구에서 수행한 시뮬레이션은 개발된 모델이 토양 환경 내에서 유기 용매의 이류 이동에 영향을 미치는 다양한 인자들의 영향을 분석하는데 유용함을 보여준다.

• 한국군사과학기술학회지
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• 제21권1호
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• pp.74-85
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• 2018

This study has analyzed the convective heat transfer on the deck exposed to the high-temperature impingement exhausting from a VTOL vehicle. The heat flow of the impingement on the deck is modeled by the convection heat transfer. The convective heat flux generated by the hot impinging jet is investigated by using both convective heat transfer formulation and conjugate heat transfer formulation. Computational fluid dynamics(CFD) code was used to compute the heat flux distribution. The RANS equation and the k-e turbulence model were used to analyze the thermal flow of the impinging jet. The heat flux distribution near the stagnation zone obtained by the conjugate heat transfer analysis shows more reasonable than the convective heat transfer analysis.

• Kyungpook Mathematical Journal
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• 제61권4호
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• pp.831-843
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• 2021

In this paper we look at the three dimensional stagnation point flow problem over a rough rotating disk. We study the theoretical behaviour of the stagnation point flow, or forced flow, in the presence of a slip factor in which convective instability stationary modes appear. We make a numerical investigation of the effects of slip on the behaviour of the flow components of the stagnation point flow where the disk is rough. We provide, for the first time in the literature, a complete convective instability analysis and an energy analysis. Suitable similarity transformations are used to reduce the Navier-Stokes equations and the continuity equation into a system of highly non-linear coupled ordinary differential equations, and these are solved numerically subject to suitable boundary conditions using the bvp4c function of MATLAB. The convective instability analysis and the energy analysis are performed using the Chebyshev spectral method in order to obtain the neutral curves and the energy bars. We observe that the roughness of the disk has a destabilising effect on both Type-I and Type-II instability modes. The results obtained will be prominently treated as benchmarks for our future studies on stagnation flow.

• Journal of Advanced Marine Engineering and Technology
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• 제18권3호
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• pp.94-101
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• 1994

To develope the new simulator for the analysis of fluid flow information, the influence of various convective difference schemes were evaluated. General curvilinear coordinate system with nonorthogonal grids was adopted for the successful analysis of various complex geometries. Computation results show that if we can not obtain full grid numbers within available computational environment, we need to use higher order finite difference schemes to keep the prediction accuracy.

• 환경영향평가
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• 제11권3호
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• pp.173-187
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• 2002

토양 속에서 발생될 수 있는 용질과 용매의 복합 수송시스템을 대상으로 한 연구 중 회석상태로부터 포화상태에 이르기까지의 넓은 농도분포를 가지는 토양 용액에 적용될 수 있는 물리 화학적 이론에 입각한 지배방정식을 발표한 연구는 전무한 실정이다. 본 연구는 용매와 토양기체간 그리고 용질과 결정간의 상변화를 고려한 연립물질수지방정식을 제시하고, 여기에 타율적 대류를 포함하는 상호확산 분산수송방정식을 도입하여 대류와 확산에 관한 프럭스를 분리, 결정하는 것을 목적으로 한다. 대류 플럭스의 결정은 타율적으로 이루어지는 것이 이론적으로 타당하며, 이러한 타율적 대류 플럭스가 제공된다면 본 연구에서 제시된 지배방정식을 이용해서 토양용액의 복합수송 시스템을 범용적으로 해석, 예측할 수 있을 것으로 판단된다.

• 물과 미래
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• 제18권3호
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• pp.265-270
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• 1985

The prediction of a design-flood hydrograph at a particular site on a river may be based on the derivation of discharge or stage hydrograph at an upstream section, togeater with a method to route this hydrograph along the rest of river. On the other hand, flood routing methods provide a useful tool for the analysis of flooding in all but the smaller catchment, and these methods are largely stored into hydrological method and hydraulic method. Although the Muskingum Method as a hydrological method ignores dynamic effects on the flood wave, Muskingum-Cunge Method based on hydraulic method is possible to improve the method so that it gives a good approximation to the solution of the linear convective-diffusion equation. This is made on the basis of the finite diffeience equation for the Muskingum Method. In the study, the outflows predicted by Muskingum-Cunge Method are campared with the observed outflows of the Pyung Chang River.

• 한국환경과학회지
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• 제25권3호
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• pp.345-359
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• 2016

This study analyze the synoptic meteorological cause of rainfall, rainfall intensity, drop size distribution(DSD), fall velocity and oblateness measured by the 2D-Video distrometer(2DVD) by comparing two cases which are heavy rainfall event case and a case that is not classified as heavy rainfall but having more than $30mm\;h^{-1}$ rainrate in July, 2014 at Gimhae region. As a results; Over the high pressure edge area where strong upward motion exists, the convective rain type occurred and near the changma front, convective and frontal rainfall combined rain type occurred. Therefore, rainrate varies based on the synoptic meteorological condition. The most rain drop distribution appeared in the raindrops with diameters between 0.4 mm and 0.6 mm and large particles appeared for the convective rain type since strong upward motion provide favorable conditions for the drops to grow by colliding and merging so the drop size distribution varies based on the location or rainfall types. The rainfall phases is mainly rain and as the diameter of the raindrop increase the fall velocity increase and oblateness decrease. The equation proposed based on the 2DVD tends to underestimated both fall velocity and oblateness compared with observation. Since these varies based on the rainfall characteristics of the observation location, standard equation for fall velocity and oblateness fit for Gimhae area can be developed by continuous observation and data collection hereafter.

• Journal of Advanced Marine Engineering and Technology
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• 제29권7호
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• pp.779-784
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• 2005

This paper presents the theory of similarity transformations applied to the momentum and energy equations for laminar, forced, external boundary layer flow over a horizontal flat plate which leads to a set of non-linear, ordinary differential equations of phase change material slurry(PCM Slurry). The momentum and energy equation set numerically to obtain the non-dimensional velocity and temperature profiles in a laminar boundary layer are solved. The heat transfer characteristics of PCM slurry was numerically investigated with similar method. It is clarified that the similar solution method of Newtonian fluid can be used reasonably this type of PCM slurry which has low concentration. The data of local wall heat flux and convective heat transfer coefficient of PCM slurry are higher than those of water more than 150$\~$200$\%$, approximately.