• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1140-1145
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• 2003

In this paper, some dominant aeroacoustic characteristics of fans used in appliances are reviewed. The numerical attempts to analyze tile aeroacoustic noise of fans are briefly reviewed for various fans. Axial fans for refrigerator, cross flow fans fer air-conditioner, sirocco fans and turbo fans are anal: zed. The unsteady flow field, which is essential data for aeroacoustic analysis, is calculated by commercial CFD code. Acoustic pressure is calculated by Ffowcs Williams and Hawkings equation and Lowson's equation. During the analysis, dominant noise sources are identified.

• The KSFM Journal of Fluid Machinery
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• v.9 no.5 s.38
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• pp.36-41
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• 2006

In the present study, a transient incompressible viscous turbulent flow is simulated for the automotive torque converter with moving mesh technique. For the analysis, entire torque converter flow passages are modeled. Computed torque ratio, capacity factor and efficiency show a good agreement with the experiment data. The flow instabilities characterized by back-flow and wake etc. appeared in some cascade passages are shown to be propagating along tangential direction. These flow patterns are mainly influenced by the pump and turbine blade passing and can't be predicted through conventional steady simulation with a mixing plane approach. The understanding of the unsteady flow characteristics in a torque converter achieved in the present study may lead to the optimal design of a torque converter.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.47-52
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• 2007

Missile staging and airframe separation simulation were performed by using a numerical technique for simulating the dynamics of multiple moving bodies. A 6DOF model is fully integrated into the CFD solution procedure to determine the body dynamics. Chimera grid technique offered efficient CFD simulation of multiple moving bodies. Through this simulation the safety of deployed staging and airframe separation mechanism was verified.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.137-143
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• 1999

The unsteady transonic viscous flow has been analyzed over an oscillatory airfoil. The CSCM(Conservative Supra Characteristic Method) upwind flux difference splitting method and the iterative time marching scheme having first order accuracy in time and second to third order accuracy in space was applied on dynamic meshes. A steady flow field of Mach number 0.7 has been calculated for the verification of unsteady algorithm. The time-accurate unsteady calculations have been done for NACA 0012 airfoil oscillating around quarter chord about freestream Mach number 0.6 on dynamic meshes. The results have been compared with the AGARD Case 3 experimental data. The periodic characteristics have been compared with the experimental results.

• Journal of computational fluids engineering
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• v.7 no.1
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• pp.20-27
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• 2002

Flow over a circular cylinder is studied numerically using a turbulence model. Based on the κ-ε-f/sub μ/ model of Park and Sung[6], a new damping function is used. The efficiency of the strain dependent damping function is addressed for vortex-shedding flows past a circular cylinder. The mean velocity and Reynolds stresses are compared with available experimental data at Re/sub D/= 3900. Also, the computational results for the Strouhal number are evaluated at several Reynolds number. The predictions by κ-ε-f/sub μ/ model are in good agreement with the experiments.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.23-28
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• 2002

TNumerical simulations of the supersonic impinging jet flows are carried out using the 3D Navier-Stokes code. This paper is focuses on the unsteady flow features associated with stagnation bubbles and other oscillatory behavior. The 3D code was validated by reproducing the results of Lamont's experiments. Computation is carried out for the cases in which the unsteadiness of the plate shock has been observed experimentally. The computational results confirm the oscillatory feature in several kHz. Unsteady calculation with algebraic turbulence model is also performed. It is found that the laminar and turbulent results have some discrepancy in the transient period. However, both of them reveal the oscillatory behavior with similar frequency.

• Journal of computational fluids engineering
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• v.14 no.4
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• pp.1-6
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• 2009

In the present study, numerical simulations were performed in a stirred solid/liquid system by using Eulerian multi-phase model. The transient flow field of liquid and distribution of solid particles were predicted in the stirred tank with pitched paddle impeller and baffles. The Frozen rotor method is adopted to consider the rotating motion of the impeller. The effects of number and width of baffles on the mixing time and the quality of solid suspension in the stirred tank are presented numerically. The result shows that the mixing time decreases as the width and number of baffles increase. The present numerical methodology can be applied to optimizing mixing condition of industrial mixer.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.652-659
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• 2000

The purpose of this study is to present the most effective numerical scheme to calculate the unsteady flows. In order to calculate the flow quantities of flow past a circular cylinder, Three-time level and five convective schemes are applied to unsteady and convective terms, respectively. The values obtained are compared with those from the existing experimental and numerical studies. At Reynolds numbers up to 160, time intervals can be expanded 10 times of Implicit Euler scheme using Three-time level method, and it is found that QUICK and CUI schemes work much stable than others even if less grid density conditions. The combination of Three-time level and QUICK scheme gives high resolutions for laminar unsteady problems with PC level.

• Journal of Ocean Engineering and Technology
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• v.26 no.5
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• pp.40-46
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• 2012

This paper considers a two-dimensional hydrofoil that is fully submerged and oscillating with forward speed. The flow field is assumed to be a propagating vertical velocity field. Using the perturbation theory, the problem is linearized, and the leading-order lift force is surveyed. The thrust force is analytically derived as the second-order horizontal force. As an example, the lift and thrust for a flapping flat plate in heaving and pitching modes are analyzed. The parameters affecting the thrust are listed. The thrust is expressed in terms of the quadratic transfer functions in relation to the disturbances. The quadratic transfer functions are studied parametrically to assess the most favorable thrust.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.927-932
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• 2006

A simulation and experimental study for energy flow dynamics of floor radiant heating system were performed. The study was done under both environmental chamber and a house with several rooms. The unsteady energy analysis method using equivalent R-C circuit and radiation heat transfer analysis of enclosure analysis method with simple structured rooms were used for computer simulation. Also, first order dynamics with time delay in analyzing the return water was considered. The results of temperature changes of the simulation study are good fit with the ones of experimental one.