• Journal of the Society of Naval Architects of Korea
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• v.39 no.3
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• pp.8-17
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• 2002

In this paper, the computational analysis of open-water characteristics for three model propellers(P4119, P4842 and 3 podded propeller of KRISO) is done by using a viscous-flow method based on Reynolds-Averaged Navier-Stokes equations. The results are presented for open-water performances, blade-section pressures, and circumferentially-averaged velocity profiles for the all three propeller models. Overall close agreements with available experimental data are shown. However, some discrepancies are also found in the pressure near the leading edge of the propeller blade and the open-water performance of the podded propellers.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.188-192
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• 2004

A Numerical analysis method is developed in order to compute the flaw and wave field for 2-dimensional floating body in the free roll motion with 3 degrees of freedom. Navier-Stokes and continuity equations are gaverning equations in tire present study. Finite Difference method is introduced to discretize the governing equation. The free surface is traced by the interface tracking method and the grid system is fitted to boundaries including free surface and body surface, which is moving in the flow field. The numerical scheme is based on Maker and Cell method. For the sake of validation of the numerical method, the computed roll decay factors according to tire midship section shapes are compared with measured results. The numerical results are discussed in order to understand the effect of midship section shape on roll motion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1348-1358
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• 2004

The filling pattern and an adaptive grid refinement based on the finite element method and Eulerian mesh advancement approach have been developed to analyze incompressible transient viscous flow with free surfaces. The governing equation fur flow analysis is Navier-Stokes equation including inertia and gravity effects. The mixed FE formulation and predictor-corrector method are used effectively for unsteady numerical simulation. The flow front surface and the volume inflow rate are calculated using the filling pattern technique to select an adequate pattern among seven filling patterns at each tetrahedral control volume. By adaptive grid refinement, the new flow field that renders better prediction in flow surface shape is generated and the velocity field at the flow front part is calculated more exactly. In this domain the elements in the surface region are made finer than those in the remaining regions for more efficient computation. The collapse of a water dam and the filling of a fluidity spiral have been analyzed. The numerical results have been in good agreement with the experimental results and the efficiency of the adaptive grid refinement and filling pattern techniques have been verified.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.2
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• pp.136-147
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• 2009

The computational prediction method of speed performance for a ship with vortex generators is proposed. The Reynolds averaged Navier-Stokes equation has been solved together with the application of Reynolds stress turbulence model. The computations are carried out under identical conditions of the experimental method, i.e., towing and self-propulsion calculations without and with vortex generators. The speed performance in full scale is obtained through analyzing the computational results in model scale according to the revised model-ship performance analysis method of ITTC'78 with considering the vortex generators into account. The characteristics of resistance, self-propulsion and wake characteristics on the propeller plane are investigated. The proposed computational prediction clearly shows the effect of vortex generators and can be applicable to the design tool for vortex generators.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.1
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• pp.217-224
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• 2003

The frost and mist in the windshield disturb the sight of driver and passengers especially in winter. This possibly leads to safety problems. In order to export automobiles to the countries of North America, the safety regulation requires the frost of selected area should be completely melted in 30 minutes. The defrost pattern and time for melting of frost are fully dependent on the flow and temperature field near the windshield. Furthermore, the flow and temperature field near the windshield are dependent on the air discharged from defrost nozzle. The present work has been done for understanding the flow features of the discharged air and internal flow within the nozzle duct. The three dimensional Navier-Stokes code was used for performing the generic A/C duct flow analysis. The present results were nearly coincided with experimental data. To perform the parametric study of the effectiveness of the number of guide vanes, the discharge angle and the location of nozzle were changed. The ratio of volume flow rate through defrost nozzle and side exit were compared to investigate the influence of parameters on the effectiveness of defrost nozzle. The velocity profiles and flow patterns of the defrost nozzle duct were also analyzed.

• Journal of Hydrogen and New Energy
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• v.26 no.5
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• pp.438-444
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• 2015

This study describes the effect of T branch shape on internal flow characteristics inside itself. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equation have been used as governing equations for the numerical analysis. The T branch was modeled assuming that it is used for Alaska pipeline project which was planned to provide reliable transportation of natural gas from ANS to Alaska-Yukon border. Therefore the characteristics of T branch and operating condition of pipeline were from report of Alaska pipeline project. The nine T branch shapes were analyzed and the mass flow rate ratio between mainline and branch was assumed to be 0.95 : 0.05, 0.9 : 0.1, 0.85 : 0.15. The results shows that there are typical flow patterns in T branch and the shape of T branch makes some differences to the internal flow of branch rather than mainline.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.1971-1981
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• 2002

Two-dimensional solidification analysis during rheology forming process of semi-solid aluminum alloy has been studied. Two-phase flow model to investigate the velocity field and temperature distribution is proposed. The proposed mathematical model is applied to the die shape of the two types. To calculate the velocities and temperature fields during rheology forming process, the each governing equations correspondent to the liquid and solid region are adapted. Therefore, each numerical model considering the solid and liquid coexisting region within the semi-solid material have been developed to predict the defects of rheology forming parts. The Arbitrary Boundary Maker And Cell(ABMAC) method is employed to solve the two-Phase flow model of the Navier-Stokes equation. Theoretical model basis of the two-phase flow model is the mixture rule of solid and liquid phases. This approach is based on using the liquid and solid viscosity. The Liquid viscosity is pure liquid state value, however solid viscosity is considered as a function of the shear rate, solid fraction and power law curves.

• Computers and Concrete
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• v.20 no.6
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• pp.671-682
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• 2017

In this research, seismic response of pipes is examined by applying nanotechnology and piezoelectric materials. For this purpose, a pipe is considered which is reinforced by carbon nanotubes (CNTs) and covered with a piezoelectric layer. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via cylindrical shell element and Mindlin theory. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite and to consider the effect of the CNTs agglomeration on the scismic response of the structure. Moreover, the dynamic displacement of the structure is extracted using harmonic differential quadrature method (HDQM) and Newmark method. The main goal of this research is the analysis of the seismic response using piezoelectric layer and nanotechnology. The results indicate that reinforcing the pipeline by CNTs leads to a reduction in the displacement of the structure during an earthquake. Also the negative voltage applied to the piezoelectric layer reduces the dynamic displacement.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.2
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• pp.73-83
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• 2021

In this study, the numerical investigation of the flow around the SUBOFF submarine model is performed by using the Detached Eddy Simulation (DES) method which is developed based on the SST k-ω turbulence model. At the DES analysis level, complex vortical flows around the submarine model are caused mainly by the vortices due to the appendages and their interactions with the flows from the hull boundary layer and other appendages. The complexity and scale of the vortical flow obtained from the numerical simulations are highly dependent on the grid. The computed local flow properties of the submarine model are compared with the available experimental data showing a good agreement. The DES analysis more reasonably estimates the physical phenomena inherent in the experimental result in a low radius of the propeller plane where vortical flows smaller than the RANS scale are dominant.

• Particle and aerosol research
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• v.15 no.1
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• pp.27-36
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• 2019

Numerical analysis has been conducted on three-dimensional airflow distribution in the passenger cabin of a high-speed electric train. The types of air distribution systems investigated in the present study were those of TGV and Shinkansen. The Reynolds-averaged Navier-Stokes equations governing the mass and momentum conservations of the airflow in the cabin were solved by using a finite volume method, which are coupled with the standard $k-{\varepsilon}$ turbulence model equations. Predicted velocity distributions were presented on several selected planes in the passenger cabin. The present three-dimensional simulations were found to show the overall features of the airflow in the passenger cabin fairly well. In particular, it was shown that the type of air distribution for Shinkansen was more suitable for a non-smoking cabin than that for TGV.