• Journal of Navigation and Port Research
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• v.26 no.5
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• pp.563-569
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• 2002

To overcome the weaknesses of conventional finite difference model in pollutant dispersion modelling, the particle tracking method is used. In this study, a three dimensional particle tracking model which can be used in Princeton Ocean Model was developed and verified through the various numerical tests. Usability of the model was also confirmed through the ocean outfall modelling in Tampa Bay, Florida. As it is expected, random walk model showed the less dispersion in a range compared to the conventional finite difference model and its reason is estimated due to an error from numerical diffusion which the conventional model holds. This newly developed model is expected to be used in various ocean dispersion modelling.

• Steel and Composite Structures
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• v.12 no.3
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• pp.249-260
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• 2012

In this study, stress and deflection behaviours of T-type welding joint applied to HE200M steel beam and column were investigated in finite element method (FEM) under different distributed loads. In the 3D-FEM modelling, glue option was used to contact between steel materials and weld nuggets. Geometrical model was designed as 3-dimensional solid in ANSYS software program. After that, homogeneous, linear and isotropic properties were used to design to materials of model. Solid-92 having 3-dimensional, 4 faced and 10-noded was selected as element type. In consequence of mesh operation, elements of 13285 and nodes of 28086 were occurred. Load distribution was applied to top surface of steel beam to determine behaviours of stress and deflection. As a result of FEM analysis applied with the loads of 55,000 N, 110,000 N and 220,000 N, maximum values were obtained as 116 N/$mm^2$, 232 N/$mm^2$ and 465 N/$mm^2$ for stress and obtainedas 1,083 mm, 2,166 mm and 4.332 mm for deflection, respectively. When modelling results and classical calculation values were compared, it was obtained difference of 10 % for stress values and 2.5% for deflection values.

• Journal of Korean Society of Steel Construction
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• v.12 no.3 s.46
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• pp.303-315
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• 2000

The main object of this study is to analyze mechanical behaviors as anisotropic three-dimensional body under various static loads. This paper presents the applicability of the finite difference method to three dimensional problem of anisotropic body. The finite difference method as applied here is generalized to anisotropic three-dimensional problem of elastic body where the governing differential equations of equilibrium of such bodies are expressed in terms of the displacement u, v, and w in the coordinates axes x, y and z, care being taken to modify the finite difference expressions to satisfy the appropriate boundary conditions. By adopting a new three dimensional finite difference modelling including elimination of pivotal difference points in the case of free boundary condition, the three dimensional problem of anisotropic body was successfully completed. Several numerical results show quick convergence and numerical validity of finite difference technique in three dimensional problem.

• Geomechanics and Engineering
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• v.23 no.4
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• pp.365-379
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• 2020

One of the leading causes for the damage of various underground structures during an earthquake is soil liquefaction, and among this liquefaction-induced uplift of these structures is a major concern. In this study, finite-difference modelling is carried out to study the liquefaction-induced uplift of an underground structure of 5 m diameter (D) with and without the replacement of the in-situ fine sand around the structure with the coarse sand. Soil replacements are carried out by three methods: replacement of soil above the structure, around the structure, and below the structure. The soil behaviour is represented using the elastic-perfectly plastic Mohr-Coulomb model, where the pore pressures were computed using Finn-Byrne formulation. The predicted pore pressure and uplift of the structure due to sinusoidal input motion were validated with the centrifuge tests reported in the literature. Based on numerical studies, an empirical equation is developed for the determination of liquefaction-induced maximum uplift of the underground structure without replacement of the in-situ sand. It is found that the replacement of soil around the structure with 2D width and spacing of D can reduce the maximum uplift by 50%.

• Tribology and Lubricants
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• v.18 no.6
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• pp.402-410
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• 2002

In this study, a hydrodynamic analysis of the reciprocating compressor crankshaft considering a finite bearing modelling of the journal bearings used in small refrigeration compressors is performed. In the problem formulation of the compression mechanism dynamics, all corresponding hydrodynamic forces and moments are considered using the finite bearing analysis in order to determine the crankshaft trajectory at each step. The solution of the Reynolds' equation is determined numerically using a finite difference method and a Newton-Raphson procedure was employed in solving the dynamic equations of the crankshaft. The crankshaft orbits fur the finite bearing model and short bearing theory were used to compare the effect of the hydrodynamic farces of the journal bearings on the dynamic and lubrication characteristics of the crankshaft-journal bearing system. Results show that the finite bearing model for the journal bearings must be considered in calculating for the accurate dynamic characteristics of the reciprocating compressor crankshaft.

• Computers and Concrete
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• v.2 no.2
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• pp.97-110
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• 2005

Rheological behaviour of fresh concrete is an important factor in controlling concrete quality. It is recognized that the measurement of the slump is not a sufficient test method to adequately characterize the rheology of fresh concrete. To further understand the slump measurement and its relationship to the rheological properties, an elasto-viscoplastic, 2-D axisymmetric finite element (FE) model is developed. The FE model employs the Bingham material model to simulate the flow of a slump test. An experimental program is carried out using the Slump Rate Machine (SLRM_II) to evaluate the finite element simulation results. The simulated slump-versus-time curves are found to be in good agreement with the measured data. A sensitivity study is performed to evaluate the effects of yield stress, plastic viscosity and cone withdrawal rate on the measured flow curve using the FE model. The results demonstrate that the computed yield stress compares well with reported experimental data. The flow behaviour is shown to be influenced by the yield stress, plastic viscosity and the cone withdrawal rate. Further, it is found that the value of the apparent plastic viscosity is different from the true viscosity, with the difference depending on the cone withdrawal rate. It is also confirmed that the value of the final slump is most influenced by the yield stress.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.315-322
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• 2009

This paper presents a novel numerical method based on the extended moving least squares finite difference method(MLS FDM) for solving 1-D Stefan problem. The MLS FDM is employed for easy numerical modelling of the moving boundary and Taylor polynomial is extended using wedge function for accurate capturing of interfacial singularity. Difference equations for the governing equations are constructed by implicit method which makes the numerical method stable. Numerical experiments prove that the extended MLS FDM show high accuracy and efficiency in solving semi-infinite melting, cylindrical solidification problems with moving interfacial boundary.

• Steel and Composite Structures
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• v.49 no.5
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• pp.587-602
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• 2023

This article presents the numerical modelling of transient heat transfer in highly heterogeneous composite materials where the thermal conductivity, specific heat and density are assumed to be directional-dependent. This article uses a coupled finite element-finite difference scheme to perform the transient heat transfer analysis of unidirectional (1D) and multidirectional (2D/3D) functionally graded composite panels. Here, 1D/2D/3D functionally graded structures are subjected to nonuniform heat source and inhomogeneous boundary conditions. Here, the multidirectional functionally graded materials are modelled by varying material properties in individual or in-combination of spatial directions. Here, fully spatial-dependent material properties are evaluated using Voigt's micromechanics scheme via multivariable power-law functions. The weak form is obtained through the Galerkin method and solved further via the element-space and time-step discretisation through the 2D-isoparametric finite element and the implicit backward finite difference schemes, respectively. The present model is verified by comparing it with the previously reported results and the commercially available finite element tool. The numerous illustrations confirm the significance of boundary conditions and material heterogeneity on the transient temperature responses of 1D/2D/3D functionally graded panels.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.2
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• pp.54-64
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• 1992

During combustion process in a diesel engine radiation heat transfer is the same order of magnitude as the convection heat transfer. An approximation of heat and momentum source distributions is applied at a level consistent with those used in modelling the soot distribution and the turbulence instead of modelling the fuel spray and the chemical kinetics. This paper illustrates a use of the third order spherical harmonics approximation to the radiative transfer equation and delta-Eddington approximation to the scattering phase function for droplets in the flow. Results are obtained numerically by a time marching finite difference scheme. This study aims to compare heat transfer with convection heat transfer and to investigate the importance of scattering by fuel droplets and of accounting for spatial variations in the extinction coefficient on the radiative heat flux distributions at the walls of a disc shaped diesel engine.

• Geotechnical Engineering
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• v.13 no.2
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• pp.29-38
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• 1997

Strain softening is observed for geomaterials such as rocks when they are sheared. The proper computational modelling for strain softening is very important because this behavior is closely related to failure in geotechnical problems. In this paper, we have investigated the proper FEM techniques for modelling strain softening in order to simulate failure behavior numerically. In showing numerical examples, the effects of element shape, mesh pattern and of imperfection and the difference between small and large deformation theories, of displacement control and pressure control after peak have been discussed.