• The KSFM Journal of Fluid Machinery
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• v.10 no.1 s.40
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• pp.26-33
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• 2007

Four design candidates for a partial admission turbine have been chosen from a preliminary design process. Their performance were estimated through the 3-D numerical analyses using a frozen rotor method. In order to select the optimum design, each flow analysis result was compared with others. Flow characteristics in the passages and some types of losses induced by shocks and wakes were found from calculation results. Based on these calculations, a new rotor blade was redesigned and compared with previous one through flow analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.10 s.241
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• pp.1083-1091
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• 2005

Turbulent flow around a rotating circular cylinder is investigated by Direct Numerical Simulation. The calculation is performed at three cases of low Reynolds number, Re=161, 348 and 623, based on the cylinder radius and friction velocity. Statistically strong similarities with fully developed channel flow are observed. Instantaneous flow visualization reveals that the turbulence length scale typically decreases as Reynolds number increases. Some insight into the spacial characteristics in conjunction with wave number is provided by wavelet analysis. The budget of dissipation rate as well as turbulent kinetic energy is computed and particular attention is given to the comparison with plane channel flow.

• 한국전산유체공학회:학술대회논문집
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• 2004.03a
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• pp.172-177
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• 2004

In the present work, we have interests on the modification of parallel implemented with MPI(Message Passing Interface) programming method, 3-Dimensional, unsteady, incompressible Navier-Stokes equation solver to analyze the low-Reynolds number flow In order to accurate calculation aerodynamic coefficients in low-Reynolds number flow field, we modified the two-equation turbulence model. This paper describes the development and validation of a new two-equation model for the prediction of flow transition. It is based on Mentor's low Reynolds $\kappa-\omega$ model with modifications to include Total Stresses Limitation (TSL) and Separation Transition Trigger (STT)

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1288-1300
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• 1994

Mathematical modeling and numerical calculation on the flow and thermal characteristics induced by fire in a partial enclosure are performed. The solution procedures include the Shvab-Zeldovich approximation for the physical transport equations, low Reynolds number k-.epsilon. model for the turbulent fluid flow and Discrete Ordinate method(DOM) to calculate the radiative heat transfer. PMMA(Polymethylmethacrylate) is adopted as a solid fuel. Two different cases are considered : combustions with and without gas radiation occuring in a open cavity for variable pyrolyzing location of PMMA. When the fire source is located at the left-wall, the flow region of flame gas is limited at the left-wall and ceiling and recirculation region of inlet gas is formulated at neat the floor. In case of neglecting the radiative heat transfer, more large flame size and higher temperature is predicted. It is essential to consider the radiative heat transfer for analysis of fire phenomenon.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.3
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• pp.371-380
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• 1998

The flow patterns and dynamic properties of ship's propulsion mechanism of two-stage Weis-Fogh type are studied by the discrete vortex method. In order to study the effects of the interaction of the two wings two cases of the phase differences of the wing's motion are considered the same phase and the reverse phase. The flow patterns by simulations correspond to the photographs obtained by flow visualization and flowfield of the propulsion mechanism which is unsteady and complex is clearly visualized by numerical simulations. The time histories of the thrust an the drag coefficients on the wings are also calculated and the effects of the interaction of the two wings are numerically clarified.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.331-338
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• 2004

We present a three-dimensional average flow model considering elastic deformation of pad asperities for chemical mechanical planarization. To consider the contact deformation of pad asperities in the calculation of the flow factor, three-dimensional contact analysis of a semi-infinite solid based on the use of influence functions is conducted from computer generated three dimensional roughness data. The average Reynolds equation and the boundary condition of both force and momentum balance are used to investigate the effect of pad roughness and external pressure conditions on film thickness and wafer position angle.

• Journal of Mechanical Science and Technology
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• v.14 no.11
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• pp.1257-1266
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• 2000

The flow field if a ship's propulsion mechanism of Weis-Fogh type is studied by the discrete vertex method. The wing in a channel is approximated by a finite number of bound vortices, and free vortices representing the separated flow are introduced from the trailing edge if the wing. The time histories of the thrust, the drag, and the moment acting on the wing are calculated, including the unsteady force due to the change of strength of the bound vortices. These calculated values agree well with the experimental values. The flow field of this propulsion mechanism is numerically clarified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.75-80
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• 1998

Statistical Energy Analysis(SEA) has been considered as a possible method for predicting responses of complex structures, especially at higher frequencies. In this paper, an SEA model of vehicle was built using 138 energy storing subsystems connected together using 1019 junctions. SEAM software program was used to build and calculate the model. To demonstrate the accuracy of the SEA model, predicted response levels were compared with measured levels. The source input levels were measured at the engine mounting parts. For the vibration levels, the agreement between the calculation results and the experimental ones was found to be good. The energy flow between connected subsystems can be presented, because the analysis method is based on the estimation of the power flow between subsystems. This paper also identifies some dominant energy flow paths from sources. It is finally presented that the SEA model can optimize the design parameters of vehicles using model parameters and energy flow paths.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.24 no.4
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• pp.20-25
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• 2016

A primary benefit of flight at high angle-of-attack conditions is to be able to reduce the speed of flight and maneuvers, which can enhance the capability of sensing and obstacle avoidance for a small UAV. The flight at high angle-of-attack conditions, however, is easy to be beyond stall which is characterized by substantial flow separation over an airfoil. Current numerical analysis was conducted on the capabilities of three representative turbulence models to predict the aerodynamic characteristics of a typical airfoil at angle-of-attack conditions. The investigation shows that these turbulence models provide good comparison with experimental data for attached flow at moderate angle-of-attack conditions. Calculation by current turbulence models are, however, not appropriate at high angle-of-attack conditions with flow separation.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.507-509
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• 2000

This study developed the window based power flow analysis software for distribution system. This system was developed by using Visual C++ 6.0 in Microsoft Windows 98 environment; therefore, it utilized many advantages of window based programming for providing user-friendly interface. The backward/forward sweep algorithm is implemented in this software for power flow analysis. Especially, this software includes the newly developed classes of complex function, matrix function, and power flow calculation procedure, so it has high flexibility for enhancement and modifications.