• The KSFM Journal of Fluid Machinery
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• v.7 no.6 s.27
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• pp.55-61
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• 2004

A numerical procedure for optimizing the shape of three-dimensional sedimentation tank is presented to maximize its sedimentation efficiency. The response surface based optimization is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis for multi-phase flow. Standard $k-{\epsilon}$ model is used as a turbulence closure. Three design variables such as, tank height to center feed wall diameter ratio, blockage ratio of center feed wall and angle of distributor are chosen as design variables. Sedimentation efficiency is defined as an objective function. Full-factorial method is used to determine the training points as a means of design of experiment. Sensitivity of each design variable on the objective function has been evaluated. And, optimal values of the design variables have been obtained.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.358-362
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• 2003

Numerical simulation is conducted to clarify the heat transfer and fluid flow characteristics of HVAC(Heating, Ventilating and Air-Conditioning} for double-deck train. The HVAC system is installed under the roof of carbody. In the lay-out of HVAC system, air duct must be installed to supply air to 1st and 2nd floor respectively. The standard k-epsilon turbulent models and SIMPLEC algorithm based on finite volume method are used to solve the physical HVAC model. To assure convergence, QUICK scheme for momentum equation and the first order upwind scheme for turbulent equations are used. From the results of simulation, the temperature and velocity magnitude are also distributed uniformly in the interior of passenger car.

• 유체기계공업학회:학술대회논문집
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• 1999.12a
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• pp.125-133
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• 1999

This paper reports the impeller performance of centrifugal pump, modified HES65-250. Developed CFD code uses SIMPLE algorithm, power-law scheme, standard k-$\epsilon$ turbulence model in curvilinear coordinate system. The calculations are conducted for 5 cases, from 0.6 to 1.4 of flow rate ratio with 0.2 increment. The flow characteristics inside of impeller are analysed. The results show that reversal flows exist at the inlet of impeller which have small rotary stagnation pressure. The obtained results are compared with the experimental data at impeller exit and shows good qualitative agreement.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.1
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• pp.35-44
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• 2017

Supercavitation is one of the most attractive technologies to achieve high speed for underwater vehicles. However, the multiphase flow with high-speed around the supercavitating vehicle (SCV) is difficult to simulate accurately. In this paper, we use modified the turbulent viscosity formula in the Standard K-Epsilon (SKE) turbulent model to simulate the supercavitating flow. The numerical results of flow over several typical cavitators are in agreement with the experimental data and theoretical prediction. In the last part, a flying SCV was studied by unsteady numerical simulation. The selected computation setup corresponds to an outdoor supercavitating experiment. Only very limited experimental data was recorded due to the difficulties under the circumstance of high-speed underwater condition. However, the numerical simulation recovers the whole scenario, the results are qualitatively reasonable by comparing to the experimental observations. The drag reduction capacity of supercavitation is evaluated by comparing with a moving vehicle launching at the same speed but without supercavitation. The results show that the supercavitation reduces the drag of the vehicle dramatically.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.3
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• pp.277-285
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• 2010

We examined the optimal shape of blades and efficiency of a self-power generator when the self-power generator using flow of the water in pipe as the power source was installed. Selected factors were the shape of blades, the number of blades, pitch angle, and the existence of separator. GAMBIT2.4 was used as a modeling program, FLUENT6.3, which is computational fluid dynamics simulation program, was used as an analytical model. In the case of a viscous model, k-epsilon standard model was chosen. As a result, when the number of blades was increased, the efficiency and maximum moment were enhanced slightly. The pitch of blades went up, and maximum moment was also increased. The optimal pitch of blade was 62.5 degree and the efficiency was increased by 30%. The efficiency was also increased when a separator was installed.

• Journal of Navigation and Port Research
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• v.41 no.2
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• pp.33-38
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• 2017

A marine flapped rudder is designed to improve the effective lift generated by the rudder; this also improves the maneuverability of the ship. The flap is a high lift device installed at the trailing edge of the rudder to augment lift. In this paper, the characteristics of a thick flapped rudder are analyzed at a low Reynolds number with various ratios of flap chord length to total chord length and various aspect ratios, based on the computational fluid dynamics technique. The performance of the rudder with respect to lift, drag, and center of pressure are investigated, and the efficient ratio of flap chord length to total chord length and improved aspect ratio are determined. Ed: highlight - or 'superior'. As a case study, the flow on the flapped rudder of an NACA0021 section shape in free stream condition is simulated. The standard k-epsilon turbulence model is used to model the flow around the flapped rudder. The results indicate that the efficient ratio of the flap chord length to total chord length and aspect ratio are 0.3 and 1.4, respectively.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.4
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• pp.170-176
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• 2020

In this study, the lift, drag and moments of the rudder that influences on the maneuvering ships directly has been investigated using CFD(Computational Fluid Dynamics). One of typical ship rudders effecting on the forces and moments is the bow rudders during maneuvering on the sea. Thus, the forces and moments should be investigated for the bow of ship rudder. Among the IFS bow rudder series, the balance IFS 54 BR 15 is used for study. As a turbulent model, standard k-epsilon is applied to this study. The hydrodynamic of the bow rudder, especially lift, drag and moment coefficients are calculated for the different angles of attack. The angles of attack between water flow and rudder are presented in cases including 0°, 5°, 10°, 15°, 20°, 25°, 30° and 35°. The results of calculation for those influences on maneuvering performance of ships are compared with the relevant results of the previous experimental studies.

• Journal of computational fluids engineering
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• v.17 no.4
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• pp.81-86
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• 2012

The objective of the present study is to investigate the effects of various turbulence models on the aerodynamic noise of an air-conditioner (AC) indoor unit. The results from URANS (unsteady Reynolds-averaged Navier-Stokes) simulations with the standard k-$\varepsilon$, k-$\omega$ shear stress transport (SST) and Spalart-Allmaras (S-A) turbulence models were analyzed and compared with the noise data from the experiments. The frequency spectra of the far-field acoustic pressure were computed using the Farrasat equation derived from the Ffowcs Williams-Hawkings (FW-H) equation based on the acoustic analogy model. Two fixed fan casings and the rotating cross-flow fan were used as the source surfaces of the dipole noise in the Farrasat equation. The result with the standard k-$\epsilon$ model showed a much better agreement with the experimental data compared to the k-w SST and S-A models. The differences in the pressure spectra from the different turbulence models were discussed based on the instantaneous vorticity fields. It was found that the over-estimated power spectra with the k-w SST and S-A models are related to the emphasized small-scale vortices produced with these models.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.144-151
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• 2003

Computations of the mean and turbulence flows over three-dimensional hill of conical shape have implemented. Beside the standard $\kappa-\epsilon$, two other modifications proposed by Detering & Etling and Duynkerke for atmospheric applications were also considered. These predictions were compared with the data of a wind tunnel experiment. From the comparison, it was concluded that all three models predict the mean flow velocities equally well while only the Duynkerke's model accurately predicts the turbulence data statistics. It also concluded that there are large discrepancies between model predictions and the measurements near the ground surface. The flow field, which was obtained by using the Duynkerke's modification, was used to simulate gas dispersion from an upwind source. The calculation results are verified based on the measurement data. Modifications of the turbulent Schmidt number were carried out in order to match the measured results. The code was used to investigate the influence of the recirculation zone behind a building of cubical shape on the transport and dispersion of pollutant. For a stack behind and near the obstacle, some conclusions about the effect of the stack height and stack location were derive

• Proceedings of the ESK Conference
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• 1997.04a
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• pp.165-175
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• 1997

Brain potential is described by using Euler Lagrange equation derived from Lagrangian based on SMNI(Statistical Mechanics of Neocortical Interaction). It is assumed that excitatory neuron firing is amplitude-modulated dominantly by the sum of two modes of frequency ${\omega}and 2 {\omega}$ . Time series of this neuron firing is numerically calculated. $I_{L}$related to low frequency distribution of power spectrum, $I_{H}$high frequency, and S(standard deviation) are introduced for the effective extraction of the dynamic property in this simulated brain potential. $I_{L}$,$I_{H}$, and S are obtained from EEG of 4 persons in rest state and are compared with thoretical results. It is of importance in various fields related to human well-being such as comfort-pursued industrial design, psychology, medicine to characterize human emotional states by EEG analysis. The pleasant and unpleasant sensation among various emotional states would be demonstrated to be determined in terms of ${\epsilon}$ and ${\gamma}$ parameters estimated by the simulated $I_{L}$-$I_{H}$-S relations.