• 태양에너지
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• 제8권1호
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• pp.82-94
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• 1988

The hydrodynamic stability equations for natural convection flows adjacent to a vertical isothermal surface in cold or warm water (Boussinesq or non-Boussinesq situation for density relation), constitute a two-point-boundary-value (eigenvalue) problem, which was solved numerically using the simple shooting and the orthogonal collocation method. This is the first instance in which these stability equations have been solved using a computer code COLSYS, that is based on the orthogonal collocation method, designed to solve accurately two-point-boundary-value problem. Use of the orthogonal collocation method significantly reduces the error propagation which occurs in solving the initial value problem and avoids the inaccuracy of superposition of asymptotic solutions using the conventional technique of simple shooting.

• 대한조선학회논문집
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• 제41권2호
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• pp.55-60
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• 2004

This paper describes the estimation method of hull girder response of ships due to springing. To this aim, nonlinear springing effect on the hull girder is evaluated including vertical, horizontal, and torsional deformation of the hull. The Timoshenko beam model is used to calculate the stress distribution on the hull girder. The quadratic strip method is employed to calculate the hydrodynamic forces and moments on the hull. In order to remove the irregular frequencies, 'rigid lid'is adopted on the hull free surface level and hydrodynamic coefficients are interpolated for asymptotic values. The results of example calculation show a reasonable agreement with previous results for both symmetric and anti-symmetric responses.

• Ocean Systems Engineering
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• 제5권2호
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• pp.91-107
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• 2015

Ship hull optimization is categorized as a bound, multi variable, multi objective problem with nonlinear constraints. In such analysis, where the objective function representing the performance of the ship generally requires computationally involved hydrodynamic interaction evaluation methods, the objective functions are not smooth. Hence, the evolutionary techniques to attain the optimum hull forms is considered as the most practical strategy. In this study, a parametric ship hull form represented by B-Spline curves is optimized for multiple performance criteria using Genetic Algorithm. The methodology applied to automate the hull form generation, selection of optimization solvers and hydrodynamic parameter calculation for objective function and constraint definition are discussed here.

• Membrane and Water Treatment
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• 제12권1호
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• pp.37-41
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• 2021

This paper presents the multiscale calculation results of the very fast volume transport in micro/nano cylindrical tubes with the wall slippage. There simultaneously occurs the adsorbed layer flow and the intermediate continuum fluid flow which are respectively on different scales. The modeled fluid is water and the tube wall is somewhat hydrophobic. The calculation shows that the power loss on the tube no more than 1.0 Watt/m can generate the wall slippage even if the fluid-tube wall interfacial shear strength is 1 MPa; The power loss on the scale 104 Watt/m produces the volume flow rate through the tube more than one hundred times higher than the classical hydrodynamic theory calculation even if the fluid-tube wall interfacial shear strength is 1 MPa. When the wall slippage occurs, the volume flow rate through the tube is in direct proportion to the power loss on the tube but in inverse proportion to the fluid-tube wall interfacial shear strength. For low interfacial shear strengths such as no more than 1 kPa, the transport in the tube appears very fast with the magnitude more than 4 orders higher than the classical calculation if the power loss on the tube is on the scale 104 Watt/m.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.759-762
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• 2008

연안지역에 위치하는 하수처리장은 배제된 우수와 처리수를 해양에 방류하는 것을 고려한다. 현재 인천 학익하수처리장은 해안에 인접한 수면에 처리수를 직접 방류하는 표층방류 방법으로 설계되었다. 이러한 표층방류 방법은 조차(Tidal Range)가 큰 해안에서 방류수위가 조위(Tidal Level)보다 낮을 경우 방류관거로 해수가 유입하여 하수처리장내에서의 수리적인 문제를 유발할 수 있다. 본 연구에서는 하수처리장 방류관거로의 해수유입 방지를 위하여 방류맨홀에 Weir를 설치하는 방안을 제시하였다. 그리고 Weir의 설치에 따른 수리계산을 수행함으로써 그 적정성을 검토하였다. 수리계산 결과 방류맨홀에서 해수의 유입이 발생되지 않는 것으로 분석되었으며, 이로 인해 인천 연안의 기왕 고극조위 발생시에도 처리수의 원활한 배출이 이루어질 것으로 판단된다.

• 전기의세계
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• 제22권3호
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• pp.63-71
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• 1973

When ions move in the air under an electric field, momentum is transferred from ions to neighboring particles. The wind is raised therefore, if the ion-flow is dominant in one direction. Using this mechanism, authors developed a fan which has no moving parts, and named it EHD AIR MOVER. This paper describes its theory with experimental results. Air velocity of 450ft/min is obtained by the ion current of 5*10$\^$-6/A/cm$\^$2/. Comparison of the theoretical calculation with the experimental data shows satisfactory agreement.

• 유변학
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• 제7권2호
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• pp.101-109
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• 1995

아주작은 Reynolds수 조건하의 나선형 미세입자가 갖는 저항 및 이동계수를 계산하 는 일반적인 방법을 논하였다. 이러한 문제의 해를 구하기 위해서는 입자의 중심선을 따라 분포되어 있는 stokeslet으로 수식화된 유동장을 필요로 한다. 입자에 작용하는 수동력학적 힘과 토오크는 이러한 stokeslet의 적분에 의하여 구할 수 있는데 유동특성에 따라 2계 이상 의 텐서에 비례한다. Johnson에 의하여 유도된 적분방정식은 LU-분해법을 사용하여 해를 구하였다. 해석 결과의 정확성은 침상체를 모델로 하여 Brenner의 엄밀해와 비교하였으며, 일치된 결과를 얻었다.

• 천문학회보
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• 제46권1호
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• pp.47.1-47.1
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• 2021

Cosmic Dawn III (CoDa III) is the last of the series of simulations of the reionization of the Local Group, the galaxy cluster including the Milky Way and the M31. The simulation is based on the constrained initial condition, N-body and hydrodynamic simulation of structure formation, modelling of galaxy formation, calculation of radiation transfer, and calibration against the observed high-redshift galaxy luminosity function. We present various physical properties we observed and important lessons that could stimulate future observations.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.684-689
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• 2005

Parametric calculation were conducted to estimate performance of variable geometry of hydrogen recirculation blower for fuel cell vehicle. The pressure rise and efficiency are effected by change of the geometric parameter of impeller and casing, and stripper clearance under various mass flow. Hydrodynamic performance were evaluated, and also the inner flow fields were investigated by CFD. Calculated results show good coincidence with experimental test results of total pressure performance. Performance of model designed by parametric calculations satisfied experimental data of verification model.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권5호
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• pp.920-938
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• 2015

In the present study, a numerical prediction method on the hydrodynamic interaction force and moment between two ships in shallow and restricted waterway is presented. Especially, the present study proposes a methodology to overcome the limitation of the two dimensional perturbation method which is related to the moored-passing ship interaction. The validation study was performed and compared with the experiment, firstly. Afterward, in order to propose a methodology in terms with the moored-passing ship interaction, further studies were performed for the moored-passing ship case with a Reynolds Averaged Navier-Stokes (RANS) calculation which is using OpenFOAM with Arbitrary Coupled Mesh Interface (ACMI) technique and compared with the experiment result. Finally, the present study proposes a guide to apply the two dimensional perturbation method to the moored-passing ship interaction. In addition, it presents a possibility that the RANS calculation with ACMI can applied to the ship-ship interaction without using a overset moving grid technique.