• 한국해양공학회지
• /
• 제14권3호
• /
• pp.46-54
• /
• 2000

Three dimensional numerical experiments that included the land-use transformation by the large scale reclamation were used to investigate the mesoscale air flow over the coastal regions. In this paper the surface temperature of the inland was determined through the surface heat budget consideration with inclusion of a layer of vegetation. The vertical diffusion coefficients of momentum, heat and specific humidity in the constant flux layer were taken from the Mellor and Yamada(1975). It has shown that the resulting model is able to reproduce the air circulation in coastal regions, and the simulated characteristics agree with the known properties of this circulation. A series of numerical experiments were then carried out to investigate the diurnal response of the air flow to various types of surface inhomogeneities.

• 한국해양공학회지
• /
• 제7권2호
• /
• pp.68-78
• /
• 1993

Fatigue crack shape variation by a residual stress during crack growth and life predition are studied. An analytical method is presented to predict the influence of a residual stress due to heattreatment on crack shape variations. Computer simulation results using this me thod are graphically shown that crack growth rate to surface direction are decreased due to compressive residual stress exisiting in surface area. These results are commpared with experimental results. The fatigue life is also predicted by computer simulation of crack aspect ratio variation which is based on the surface crack length increment per unit cycle calculated from a-N diagram. Predited life is about 12 percent lower than experimental life.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.237-239
• /
• 2003

The present study investigates on design optimization of rib-roughened two-dimensional channel to enhance turbulent heat transfer. Response surface method with Reynolds-averaged Navier-Stokes analysis is used as an optimization technique. Standard $k-{\varepsilon}$model with wall functions is adopted as a turbulence closure. The objective function is defined as a linear combination of heat transfer and friction drag coefficients with weighting factor. Computational results for overall heat transfer rate show good agreements with experimental data. Four design variables are optimized for weighting factor of 0.02.

• Ocean and Polar Research
• /
• 제24권2호
• /
• pp.135-146
• /
• 2002

The upper ocean in the western equatorial Pacific warm pool during TOGA-COARE IMET IOP was simulated using a one-dimensional turbulence closure ocean mixed-layer model, which considered recent observations, such as the remarkable enhancement of turbulent kinetic energy near the ocean surface. The shoaling/deepening of the mixed layer and warming/cooling subsurface water in the model were in reasonable agreement with the observations. There was a significant improvement in simulating the cooling trend of the sea surface temperature under a westerly wind burst with heavy rainfall over previous simulations using bulk mixed-layer models. By contrast the simulated sea surface salinity (SSS) departed significantly from the observed SSS, especially during a westerly burst and the subsequent restratification period, which might be due to 3-D control processes, such as downwelling/upwelling or advection.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2005년도 연구개발 발표회 논문집
• /
• pp.240-243
• /
• 2005

This study deals with the shape optimization of a wire spacer fuel assembly of Liquid Metal Reactors (LMRs). The Response Surface based optimization Method is used as an optimization technique with the Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer using Shear Stress Transport (SST) turbulence model as a turbulence closure. Two design variables namely, pitch to fuel rod diameter ratio and lead length to fuel rod diameter ratio are selected. The objective function is defined as a combination of the heat transfer rate and the inverse of friction loss with a weighting factor. Three level full-factorial method is used to determine the training points. In total, nine experiments have been performed numerically and the resulting datas have been analysed for optimization study. Also, a comparison has been made between the optimized surface and the reference one in this study.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2005년도 연구개발 발표회 논문집
• /
• pp.185-190
• /
• 2005

This work presents a numerical procedure to optimize the elliptic-shaped pin fin arrays to enhance turbulent heat transfer. The response surface method is used as an optimization technique with Reynolds-averaged Navier Stokes analysis of flow and heat transfer. Shear stress transport (SST) turbulence model is used as a turbulence closure. Computational results for average heat transfer rate show a reasonable agreement with the experimental data. Four variables including major axis length, minor axis length, pitch and the pin fin length nondimensionalized by duct height are chosen as design variables. The objective function is defined as a linear combination of heat transfer and friction-loss related terms with weighting factor. D-optimal design is used to reduce the data points, and, with only 28 points, reliable response surface is obtained. Optimum shapes of the pin-fin arrays have been obtained in the range from 0.0 to 0.1 of weighting factor.

• 환경위생공학
• /
• 제11권3호
• /
• pp.29-35
• /
• 1996

Numerical solutions were obtained to the model equations for various parameters characterizing the pore structure, effective internal diffusion and the chemical reaction constant. The conversion was decreased with the cause of pore closure at the surface of reacting particles, reduction of porosity, surface area of reaction and effective diffusion coefficient in the solid with the progress of reaction. Total conversion was strongly depend on the local conversion at surface. According to the decreasing of impregnated concentration of the copper oxide and the increase of the flue gases concentration, total conversion was increased. And the conversion were affected by gas flow rate and pore size distribution of the reacting solid.

• 한국유체기계학회 논문집
• /
• 제7권6호
• /
• pp.55-61
• /
• 2004

A numerical procedure for optimizing the shape of three-dimensional sedimentation tank is presented to maximize its sedimentation efficiency. The response surface based optimization is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis for multi-phase flow. Standard $k-{\epsilon}$ model is used as a turbulence closure. Three design variables such as, tank height to center feed wall diameter ratio, blockage ratio of center feed wall and angle of distributor are chosen as design variables. Sedimentation efficiency is defined as an objective function. Full-factorial method is used to determine the training points as a means of design of experiment. Sensitivity of each design variable on the objective function has been evaluated. And, optimal values of the design variables have been obtained.

• Structural Engineering and Mechanics
• /
• 제37권3호
• /
• pp.285-296
• /
• 2011

The plane crack-contact problem for an infinite elastic layer with two symmetric rectangular rigid stamps on its upper and lower surfaces is considered. The elastic layer having an internal crack parallel to its surfaces is subjected to two concentrated loads p on its upper and lower surfaces trough the rigid rectangular stamps and a pair of uniform compressive stress $p_0$ along the crack surface. It is assumed that the contact between the elastic layer and the rigid stamps is frictionless and the effect of the gravity force is neglected. The problem is reduced to a system of singular integral equations in which the derivative of the crack surface displacement and the contact pressures are unknown functions. The system of singular integral equations is solved numerically by making use of an appropriate Gauss-Chebyshev integration formula. Numerical results for stress-intensity factor, critical load factor, $\mathcal{Q}_c$, causing initial closure of the crack tip, the crack surface displacements and the contact stress distribution are presented and shown graphically for various dimensionless quantities.

• 오토저널
• /
• 제12권2호
• /
• pp.43-50
• /
• 1990

The fatigue growth behavior of surface cracks cannot be adequately predicted solely by stress intensity factor analysis. This is caused by different plastic deformation due to variations in the stress field triaxiality along the crack tip. Therefore, a new model which accounts for the crack closure phenomenon is proposed in this paper to predict the fatigue crack growth patterns for surface cracks. Fatigue tests were performed to develop the new model for the prediction and to assess the accuracy of the analysis. The predicted crack growth behavior for PMMA and Aluminum alloy 7075-T6 materials agreed well with the experimental data.