• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.639-645
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• 2003

Design optimization of a transonic compressor rotor (NASA rotor 37) using response surface method and three-dimensional Navier-Stokes analysis has been carried out in this work. Baldwin-Lomax turbulence model was used in the flow analysis. Two design variables were selected to optimize the stacking line of the blade, and mass flow was used as a design variable, as well, to obtain new design point at peak efficiency. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, adiabatic efficiency was successfully improved, and new design mass flow that is appropriate to an improved blade was obtained. Also, it is found that the design process provides reliable design of a turbomachinery blade with reasonable computing time.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.5
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• pp.17-23
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• 1995

A numerical analysis on engine coolant is made by the use of FVM based general purpose 3 dimensional Navier-Stokes solver, TURB-3D. Numerical solutions are verified by comparison with the experimental data of Lotus model. The results show a good qualitative as well as quantitative comparison. Coolant flow rate control is attempted through adjusting the cross section area of passage base on the results of an original coolant passage. It is concluded from the results that the flow rate control is possible as attempted, and thus can be used in the real engine design.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.403-406
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• 2008

The performance of an entire pump system composed of an inducer, an impeller, a volute and seals has been computationally analyzed. A commercial three dimensional Reynolds Averaged Navier-Stokes method is used in this study. The axial thrust is predicted from the pump calculation in its entirety, which is necessary for such estimation. Moreover, the effects of each component on the pump performance are investigated at a design condition through the analysis of flow structures. The predicted performance is in good agreement with experimental data in terms of head rise, efficiency and volute wall pressure distributions despite of highly complex flow structures being present. The computational results also show that the axial and radial thrusts are within the design limit although corresponding experimental measurements were not taken.

• Ocean Systems Engineering
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• v.9 no.1
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• pp.43-77
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• 2019

A local-analytic-based Navier-Stokes solver has been employed in conjunction with a compound ocean structure motion analysis program for time-domain simulation of passing ship effects induced by multiple post-Panamax class ships in the exact condition of a real waterway. The exact seabed bathymetry was reproduced to the utmost precision attainable using the NOAA geophysical database for Virginia Beach, NOAA nautical charts for Hampton Roads and Norfolk harbor, and echo sounding data for the navigation channel and waterfront facilities. A parametric study consists of 112 simulation cases with various combinations of ship lanes, ship speeds, ship heading (inbound or outbound), channel depths, drift angles, and passing ship coupling (in head-on or overtaking encounters) were carried out for two waterfront facilities at NAVSTA Norfolk and Craney Island Fuel Terminal. The present paper provides detailed parametric study results at both locations to investigate the site-specific passing ship effects on the motion responses of ships moored at nearby piers.

• Advances in Computational Design
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• v.6 no.1
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• pp.43-53
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• 2021

Multi-stage pumps are the most popular pumps among various kinds of centrifugal pumps. Athorough review of different kinds of literature has led to the conclusion that there is a desperate need to increase the performance of the multi-stage centrifugal pump. Many investigators have put their efforts to increase the pump performance and also the work is being projected on various aspects of pump performance variables. To improve the multistage centrifugal pump performance by investigation, modification, and analysis many works of literature are available. For analysis, many researchers used the Navier-Stokes solver to create the three-dimensional unsteady turbulent flow numerical model with the standard k-ε turbulent equation. This paper mainly focuses on research related to the multi-stage centrifugal pump.

• Journal of Korean Port Research
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• v.10 no.1
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• pp.63-74
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• 1996

The flow analysis around the Bang-o-jin breakwater was carried out by the numerical simulation based on the package program NISA Ⅱ. The averaged Navier-Stokes equations are changed to a weak formulation, which is an application of finite element method. To get a better circulation of sea-water current, various types of breakwater modification were numerically tried for the purpose of comparisons. According to the numerical results, it proved to be very difficult to have the seawater circulate in every corner inside the breakwater. However, some cases give the promising feasibility provided that the waste water disposal plant should be additionally made.

• The Journal of the Acoustical Society of Korea
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• v.36 no.5
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• pp.314-320
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• 2017

A pressure relief valve is generally used to prevent piping systems from being broken due to high pressure gas flows. However, the sudden pressure drop caused by the pressure relief valve produces high acoustic energy which propagates in the form of compressible acoustic waves in the pipe and sometimes causes severe vibration of the pipe structure, thereby resulting in its failure. In this study, internal aerodynamic noise due to valve flow is estimated for a simple contraction-expansion pipe by combining the LES (Large-Eddy Simulation) technique with the wavenumber-frequency analysis, which allows the decomposition of fluctuating pressure into incompressible hydrodynamic pressure and compressible acoustic pressure. In order to increase the convergence, the steady Reynolds-Averaged Navier-Stokes equations are numerically solved. And then, for the unsteady flow analysis with high accuracy, the unsteady LES is performed with the steady result as the initial value. The wavenumber-frequency analysis is finally performed using the unsteady flow simulation results. The wavenumber-frequency analysis is shown to separate the compressible pressure fluctuation in the flow field from the incompressible one. This result can provide the accurate information for the source causing so-called acoustic-induced-vibration of a piping system.

• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.351-363
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• 2020

Launch vehicles are subject to airborne acoustic loads during atmospheric flight and these effects become pronounced especially in transonic region. As the vibration due to the acoustic loads can cause malfunction of payloads, it is essential to predict and reduce the acoustic loads. In this study, a complete process has been developed for predicting airborne vibro-acoustic environment inside the payload pairing and subsequent noise reduction procedure employing acoustic blankets and Helmholtz resonators. Acoustic loads were predicted by Reynolds-Averaged Navier-Stokes (RANS) analysis and a semi-empirical model for pressure fluctuation inside turbulent boundary layer. Coupled vibro-acoustic analysis was performed using VA One SEA's Finite Element Statistical Energy Analysis (FE-SEA) hybrid module and ANSYS APDL. The process has been applied to a hammerhead launch vehicle to evaluate the effect of acoustic load reduction and accordingly to verify the effectiveness of the process. The presently developed process enables to obtain quick analysis result with reasonable accuracy and thus is expected to be useful in the initial design phase of a launch vehicle.

• Transactions of the KSME C: Technology and Education
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• v.3 no.3
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• pp.233-240
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• 2015

Analysis of the aerodynamic performance of a bobsleigh has been performed for various types of bobsleigh body shape. To analyze the aerodynamic performance of the bobsleigh, three-dimensional Reynolds-averaged Navier-Stoke equations were used with the standard k-${\varepsilon}$ model as a turbulence closure. Grid structure was composed of unstructured tetrahedral grids. The radii of curvature of cowling, and height and length of front bumper at the tip on the drag coefficient were selected as geometric parameters. And, the effects of these parameters on the aerodynamic performance, i.e., the drag coefficient, were evaluated. The results shows that the aerodynamic performance is significantly affected by the height of front bumper and radius of curvature.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.3
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• pp.180-198
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• 2019

In recent years, countries like Europe and Japan have been involved in many researches on the Low-Crested Structure (LCS) which is the method to protect beach erosion and it is regarded as an alternative to the submerged breakwaters, and compiled its results and released the design manual. In the past, studies on LCS have focused on two-dimensional wave transmission and calculating required weight of armor units, and these were mainly examined and discussed based on experiments. In this study, three-dimensional numerical analysis is performed on permeable LCS. The open-source CFD code olaFlow based on the Navier-Stokes momentum equations is applied to the numerical analysis, which is a strongly nonlinear analysis method that enables breaking and turbulence analysis. As a result, the distribution characteristics of the LCS such as water level, water flow, and turbulent kinetic energy were examined and discussed, then they were carefully compared and examined in the case of submerged breakwaters. The study results indicate that there is a difference between the flow patterns of longshore current near the shoreline, the spatial distribution of longshore and on-offshore directions of mean turbulent kinetic energy in case of submerged breakwaters and LCS. It is predicted that the difference in these results leads to the difference in sand movement.