• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.23 no.3
• /
• pp.157-178
• /
• 2019

The present correspondence is conveyed on to consider the fascinating and novel characteristics of radiative hydromagnetic convective flow of a chemically reacting fluid over an exponentially accelerated inclined porous plate. Exact solutions for the fluid velocity, temperature and species concentration, under Boussinesq approximation, are obtained in closed form by the two term perturbation technique. The interesting parts of thermal dispersing outcomes are accounted in this correspondence. Graphical evaluation is appeared to depict the trademark direct of introduced parameters on non dimensional velocity, temperature and concentration profiles. Also, the numerical assortment for skin friction coefficient, Nusselt number and Sherwood number is examined through tables. The certification of current examination is confirmed by making an examination with past revelations available in composing, which sets a benchmark for utilization of computational approach.

• Journal of Advanced Marine Engineering and Technology
• /
• v.14 no.2
• /
• pp.48-65
• /
• 1990

Numerical solutions of the Navier-Stokes equations, governing 2-dimensional, time-dependent, viscous, incompressible fluid flow past a square cylinde in an infinite region, are presented for Reynolds numbers $10^2$, $10^3$and $10^4$. Finite-difference scheme, based on SOLA-VOF is adopted and a discretization of the convection term for irregular grid is newly suggested by altering the original nonconservation form into conservation one. Distribution of finer grids around the body reveals fairly reasonable consistency with the experimental variables : drag coefficient, lift coefficient, Strouhal number, fluctuating pressure coefficient, etc.

• Korea-Australia Rheology Journal
• /
• v.12 no.3_4
• /
• pp.165-173
• /
• 2000

Three-dimensional numerical simulation of isothermal/nonisothermal coextrusion process of two immiscible polymers through a rectangular channel has been done using the finite element method. The encapsulation phenomenon with the less viscous layer encapsulating the more viscous layer was investigated with the generalized Newtonian fluids. The interface position around the symmetric plane obtained by numerical simulation nearly coincided with the one observed in experiments, but the degree of encapsulation was less than the one observed experimentally. Open boundary condition method was found to be applied to the simulation of nonisothermal coextrusion process, however, the results are not far from those using the fully developed boundary condition, because the temperature development along the downstream direction is very slow in the case of convection dominated flow. When the inlet velocity is increased, the interface profile does not change in isothermal flow, while it moves upward in nonisothermal situation. The degree of encapsulation decreases along the downstream direction in nonisothermal flow. When the inlet temperature increases compared to the wall temperature, the outlet interface moves downward and the degree of encapsulation increases. The difference of degree of encapsulation between the simulation and the experiments seems to arise from the viscoelastic effect of the materials. It was concluded that the nonisothermal effect alone does not explain the complex coextrusion process and the viscoelastic effect needs to be considered.

• 유체기계공업학회:학술대회논문집
• /
• 1998.12a
• /
• pp.42-48
• /
• 1998

Numerical study is presented for the analysis of three-dimensional incompressible turbulent flows in multiblade centrifugal fan. Reynolds-averaged Navier-Stokes equations with standard k - $\epsilon$ turbulence model are transformed to non-orthogonal curvilinear coordinates, and are discretized with finite volume approximations. Linear Upwind Differencing Scheme(LUDS) is used to approximate the convection terms in the governing equations. SIMPLEC algorithm is used as a velocity-pressure correction procedure. The computational area is divided into three blocks; core, impeller and scroll, which are linked by multi-block method. The flow inside of the fan is regarded as steady flow, and mathematical formula established from the cascade theory and empirical coefficient are employed to simulate tile flow through the impeller. From comparisons between the computational results and the experimental data, the validity of the mathematical formula for the blade forces was examined and good results were obtained qualitatively. Hence, we can get the flow characteristics of multi-blade centrifugal fan and it will be a corner stone of the development of the multiblade centrifugal fan.

• Journal of Power System Engineering
• /
• v.20 no.6
• /
• pp.51-57
• /
• 2016

Experiment is carried out to investigate the mixed convective flow in three-dimensional horizontal rectangular channels filled with high viscous fluid. The particle image velocimetry(PIV) with thermo-sensitive liquid crystal tracers is used for visualizing and analysis. Quantitative data of temperature and velocity are obtained by applying the color-image processing to a visualized image, and neural network is applied to the color-to-temperature calibration. In this study, the fluid used is silicon oil(Pr=909), the aspect ratio(channel width to heigh) is 4 and Reynolds number is $2{\times}10^{-2}$. From the present study, we can visualize the quantitative temperature and velocity of mixed convective flow in three-dimensional horizontal rectangular channels simultaneously.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.18 no.3
• /
• pp.245-256
• /
• 2014

This work is focused on the boundary layer and heat transfer characteristics of hydromagnetic flow over a stretching sheet with variable thickness. Steady, two dimensional, nonlinear, laminar flow of an incompressible, viscous and electrically conducting fluid over a stretching sheet with variable thickness and power law velocity in the presence of variable magnetic field and variable temperature is considered. Governing equations of the problem are converted into ordinary differential equations utilizing similarity transformations. The resulting non-linear differential equations are solved numerically by utilizing Nachtsheim-Swigert shooting iterative scheme for satisfaction of asymptotic boundary conditions along with fourth order Runge-Kutta integration method. Numerical computations are carried out for various values of the physical parameters and the effects over the velocity and temperature are analyzed. Numerical values of dimensionless skin friction coefficient and non-dimensional rate of heat transfer are also obtained.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.2
• /
• pp.39-47
• /
• 1997

In the present paper, viscous flow fields around a wigley hull with appendages are analysed to study interactions between the hull and appendages. Navier-Stokes and continuity equations are solved by a finite volume method in a body-fitted coordinate system which conforms three dimensional ship geometries with appendages. A Sub-Grid Scale(SGS) turbulent model is used for a calculation of high Reynolds number flow. Numerical computations has been done for a Wigley hull form at $Rn=1.0{\times}10^6$. The results show that the present approach can predict, at least in qualitative sense, the influence of the appendages upon the flow field around a ship.

• 한국가시화정보학회:학술대회논문집
• /
• 2002.11a
• /
• pp.59-62
• /
• 2002

A study of three-dimensional unsteady incompressible flow past elliptic disk with aspect ratio 3 is presented. Numerical visualization using the vortex filament method was performed at Reynolds number of 20,000 on the basis of the minor diameter, the random walk method was used to calculate viscous diffusion effect. We suggest 3 stages about the wake development according to its structures, stability and motions and described the characteristics of each stages. The structure of the elliptic wake is more complicate and unstable than the wake behind a circular disk.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.7
• /
• pp.911-918
• /
• 1997

The turbulent viscous wake flows behind a single airfoil, two-dimensional stationary blade row and three-dimensional rotating blade row were calculated, and the numerical results were compared with experimental ones. The numerical technique was based on the SIMPLE algorithm using three turbulent closure models, standard k-.epsilon. model(WFM), low Reynolds number k-.epsilon. model(LRN) and Reynolds stress model (RSM). In the case of a single airfoil, WFM, LRN and RSM presented fairly good velocity distributions in the wake compared with experimental data. In the case of the stationary blade row, LRN and RSM presented better results than WFM for wake velocity distribution, and especially LRN showed best results among these three turbulent models. In the case of the rotating blade row, WFM and LRN showed fairly good agreement with experimental data of the three-dimensional velocity component distributions in the range from hub to mid span region. LRN was also superior to WFM in accuracy of prediction for the wake velocity distribution as same with the cases of a airfoil and the stationary blade row.

• 한국전산유체공학회:학술대회논문집
• /
• 2004.10a
• /
• pp.25-28
• /
• 2004

The purpose of this paper is to present essential numerical data of FCV(Flow rate Control Valve) which is used in a projectile ejection system for a underwater vehicle. A commercial CFD code is applied to analyze the 3 dimensional viscous compressible flow field within the FCV as four cases of opening rate, 25, 50, 75, and $100\%$. The flow coefficient of each cases are mainly calculated. And other characteristics such as the location of shock wave and total temperature distribution are also determined.