• Journal of computational fluids engineering
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• v.16 no.4
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• pp.1-6
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• 2011

Aerodynamic characteristics depending on the shape of an internal motor in a small-size sirocco fan for residential ventilation have been investigated. For the aerodynamic analyses of the sirocco fan, three-dimensional Reynolds-averaged Navier-Stokes equations are solved with the shear stress transport model for turbulence closure. The flow analyses are performed on hexahedral grids using a finite-volume solver. The validation of the numerical results at steady-state is performed by comparing with experimental data for the pressure and efficiency. In order to investigate the aerodynamic characteristics depending on shape of an internal motor in a sirocco fan, the reference shape is analyzed compared to the case without internal motor. Additionally, two shape parameters, height and width of the internal motor in a sirocco fan, are tested to investigate their effects on the aerodynamic characteristics. The results show that the shape of the internal motor in a sirocco fan is an important factor to improve the aerodynamic performances.

• Journal of computational fluids engineering
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• v.16 no.1
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• pp.53-59
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• 2011

In this study, steady and unsteady aerodynamic analyses of a huge rocket configuration have been conducted in a transonic flow region. The launch vehicle structural response are coupled with the transonic flow state transitions at the nose of the payload fairing. Before performing the coupled fluid-structure transonic aeroealstic simulations transonic aerodynamic characteristics are investigated for the pitching motions of the rocket at finite angle-of-attack. An unsteady CFD analysis method with a moving grid technique based on the Reynolds-averaged Navier-Stokes equations with the k-w SST transition turbulence model is applied to accurately predict the transonic loads of the rocket at pitching motion. It is shown that the fluctuating amplitude of the lateral aerodynamic loads imposed on the rocket due to the pitching motion can be significantly increased in the transonic flow region.

• Journal of computational fluids engineering
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• v.17 no.2
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• pp.21-27
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• 2012

Reynolds-averaged Navier-Stokes equations solver based on a pressure-based cell-centered finite volume method was developed using OpenFOAM libraries, which was an open source and providing computational continuum mechanics libraries. For the reasonable development of the turbulent boundary layer on the bow of the ship, specified library was developed. Grid sensitivities, such as skewness and aspect ratio of a cell, were tested for the solution convergence. Pressure, turbulent kinetic energy, turbulent dissipation rate contours on the ship surface computed by the developed CFD code were compared with those computed by the commercial CFD code, Fluent.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.275-282
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• 2007

In this study, a fluid-structure interaction (FSI) analysis system has been developed in order to evaluate the turbine cascade performance with blade structural deformation effect. Relative movement of the rotor with respect to stator is reflected by modeling independent two computational domains. To consider the deformed position of rotor airfoil, dynamic moving grid method is applied. Reynolds-averaged Navier-Stokes equations with one equation Spalart-Allmaras and two-equation SST $k-{\varepsilon}$ turbulence models are solved to predict unsteady fluid dynamic loads. A fully implicit time marching scheme based on the Newmark direct integration method with high artificial damping is used to compute the fluid-structure interaction problem. Cascade performance evaluations for different elastic axis positions are presented and compared each other. It is importantly shown that the predicted aerodynamic performance considering structural deformation effect of blade can show some deviations compared to the data generally computed from rigid blade configurations and the position of elastic axis also tend to give sensitive effect.

• Wind and Structures
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• v.18 no.5
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• pp.549-566
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• 2014

In spite of progress in the numerical simulation of typhoon wind field in atmospheric boundary layer (ABL), using typhoon wind field model in conjunction with Monte Carlo simulation method can only accurately evaluate typhoon wind field over a general terrain. This method is not enough for a reliable evaluation of typhoon wind field over the actual complex terrain with surface roughness and topography variations. To predict typhoon wind field over the actual complex terrain in ABL, a hybrid numerical simulation method combined typhoon simulation used the typhoon wind field model proposed by Meng et al. (1995) and CFD simulation in which the Reynolds averaged Navier-Stokes (RANS) equations and k-${\varepsilon}$ turbulence model are used. Typhoon wind filed during typhoon Dujuan and Imbudo are simulated using the hybrid numerical simulation method, and compared with the results predicted by the typhoon wind field model and the wind field measurement data collected by Fugro Geotechnical Services (FGS) in Hong Kong at the bridge site from the field monitoring system of wind turbulence parameters (FMS-WTP) to validate the feasibility and accuracy of the hybrid numerical simulation method. The comparison demonstrates that the hybrid numerical simulation method gives more accurate prediction to typhoon wind speed and direction, because the effect of topography is taken into account in the hybrid numerical simulation method.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.1
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• pp.73-82
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• 2016

In order to extend the operational life of Underwater Moored Platforms (UMPs), a horizontal axis water turbine is designed to supply energy for the UMPs. The turbine, equipped with controllable blades, can be opened to generate power and charge the UMPs in moored state. Three-dimensional Computational Fluid Dynamics (CFD) simulations are performed to study the characteristics of power, thrust and the wake of the turbine. Particularly, the effect of the installation position of the turbine is considered. Simulations are based on the Reynolds Averaged Navier-Stokes (RANS) equations and the shear stress transport ${\kappa}-{\omega}$ turbulent model is utilized. The numerical method is validated using existing experimental data. The simulation results show that this turbine has a maximum power coefficient of 0.327 when the turbine is installed near the tail of the UMP. The flow structure near the blade and in the wake are also discussed.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.4
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• pp.502-512
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• 2013

Simulations of cavitation flow and hull pressure fluctuation for a marine propeller operating behind a hull using the unsteady Reynolds-Averaged Navier-Stokes equations (RANS) are presented. A full hull body submerged under the free surface is modeled in the computational domain to simulate directly the wake field of the ship at the propeller plane. Simulations are performed in design and ballast draught conditions to study the effect of cavitation number. And two propellers with slightly different geometry are simulated to validate the detectability of the numerical simulation. All simulations are performed using a commercial CFD software FLUENT. Cavitation patterns of the simulations show good agreement with the experimental results carried out in Samsung CAvitation Tunnel (SCAT). The simulation results for the hull pressure fluctuation induced by a propeller are also compared with the experimental results showing good agreement in the tendency and amplitude, especially, for the first blade frequency.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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• pp.480-488
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• 2020

This study was conducted to improve the flow uniformity inside the chip tester through changing the flow path formation according to the inlet and outlet position of chamber. The internal flow and velocity distributions of the modified chamber models (Cases 1-3) were compared with the reference chamber model through three-dimensional Reynolds-averaged Navier-Stokes equations with k-ε turbulence model. The modified chamber models showed the superior flow uniformity characteristics compared to the reference chamber model. To investigate the flow uniformity in the chip tester, the standard deviation of the velocity was defined and compared. Through the internal flow analysis and assesment of the standard deviation, Case 2 among the test cases including the reference model showed the best flow uniformity generally.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.297-301
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• 2008

The flight vehicles have cavities such as wheel wells and bomb bays. The flow around a cavity is characterized as unsteady flow because of the formation and dissipation of vortices due to the interaction between the freestream shear layer and cavity internal flow, the generation of shock and expansion waves. Resonance phenomena can damage the structures around the cavity and negatively affect aerodynamic performance and stability. The flow field is observed to oscillate in the "shear layer mode" with low aspect ratio. In the present study, numerical analysis was performed for cavity flows by the unsteady compressible three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with Wilcox's $\kappa$-$\omega$ turbulence model. The flow field is observed to oscillate in the shear layer mode" with large aspect ratio. Based on the SPL(Sound Pressure Level) analysis of the pressure variation at the cavity trailing edge, the dominant frequency was analyzed and compared with the results of Rossiter's formul. The aero-acoustic wave analyzed with CPD(Correlation of Pressure Distribution).

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.129-138
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• 2003

A 1 : 20 laboratory scale test rig of a 200 MW tangentially fired boiler is built up with completely simulated structures such as platen heaters and burners. Iso-thermal turbulent flow in the boiler is mapped by 3-D PDA (Particle Dynamic Analyzer). The 3-D numerical models for the same case are proposed based on the solution of к-$\varepsilon$ model closed RANS (Reynolds time-Averaged Navier-Stokes) equations, which are written in the framework of general coordinates and discretized in the corresponding body-fitted meshes. Not only are the grid lines arranged to fit the inner/outer boundaries. but also to align with the streamlines to the best possibility in order to reduce the NDE (numerical diffusion errors). Extensive comparisons of profiles of mean velocities are carried out between experiment and calculation. Predicted velocities in burner region were quantitatively similar with measured ones, while those in other area have same tendency with experimental counterpart.