• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.133-139
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• 2011

In this paper, Based on Two-dimensional Flow Theory, adopting quasi-orthogonal method and point-by-point integration method to design the impeller of the low specific speed centrifugal pump by code, and using RANS (Reynolds Averaged N-S) Equation with a standard k-${\varepsilon}$ two-equation turbulence model and log-law wall function to solve 3D turbulent flow field in the impeller of the low specific speed pump. An analysis of the influences of the blade profile on velocity distributions, pressure distributions and pump performance and the investigation of the flow regulation pattern in the impeller of the centrifugal pump are presented. And the result shows that this method can be used as a new way in low speed centrifugal pump impeller design.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.97-103
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• 2011

With the aim to increase blade loadings and stable operating range in highly loaded compressors, this article has been conducted to explore, through a numerical parametric study, the potential of passive control using slotted bladings in cascade configurations. The objective of this numerical investigation is to analyze the influence of location, width and slope of the slots and therefore identify the optimal configuration. The approach is based on two dimensional cascade geometry, low speed regime, steady state and turbulent RANS model. The results show the efficiency of this passive technique to delay separation and enhance aerodynamic performances of the compressor cascade. A maximum of 28.3% reduction in loss coefficient have been reached, the flow turning is increased with approximately $5^0$ and high loading over a wide range of angle of attack have been obtained for the optimized control parameter.

• 한국전산유체공학회:학술대회논문집
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• 1999.05a
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• pp.58-65
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• 1999

The two different approaches for solving the nonlinear ship wave problem are disscussed in the present paper. The first one is based on a panel method which neglects the viscous effects. Another one is based on a finite volume method which solves RANS equations. The present paper has been focused on the advantages/disadvantages of the above two methods. The developed methods are applied to calculating the flow around Wigley hull & Series 60 hull to validate the performance of the present nonlinear method, Although the two methods employ quite different numerical approaches, the calculated wave patterns from the both methods show good agreements with the experiments.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.79-87
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• 2002

The present work analyzed the effect of mixing vane shape on the flow structure and heat transfer downstream of mixing vane in a subchannel of fuel assembly, by obtaining velocity and pressure fields, turbulent intensity, flow-mixing factors, heat transfer coefficient and friction factor using three-dimensional RANS analysis. NJl5, NJ25, NJ35, NJ45, which were designed by the authors, were tested to evaluate the performances in enhancing the heat transfer. Standard $\kappa-\epsilon$ model is used as a turbulence closure model, and, periodic and symmetry conditions are set as boundary conditions. The flow blockage ratio is kept constant, but the twist angle of mixing vane is changed. The results with three turbulence models( $\kappa-\epsilon$, $\kappa-\omega$, RSM) were compared with experimental data.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2440-2443
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• 2008

This paper presents a three dimensional shape optimization procedure for a low-speed axial flow fan blade with a weighted average surrogate model. Reynolds-averaged Navier-Stokes equations with shear stress transport turbulence model are discretized by finite volume approximations. Six variables from airfoil profile and lean are selected as design variables. 3D RANS solver is used to evaluate the objective functions of total pressure efficiency. Surrogate approximation models for optimization have been employed to find the optimal design of fan blade. A search algorithm is used to find the optimal design in the design space from the constructed surrogate models for the objective function. The total pressure efficiency is increased by 0.31% with the weighted average surrogate model.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2810-2815
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• 2008

Flow pulsation in the gap connecting with two parallel channels is investigated by RANS and URANS approaches. The two parallel channels are connected by a small channel called for a gap. The parallel channels are designed to have different cross section area with its ratio of 0.5. Computations are conducted using a CFX 11.0 code. The bulk Reynolds number is 60,000. Predicted results are compared with the previous experimental result. Mean velocity profile at the center of gap region are compared with experiments for its validation. Spectral analysis on the lateral velocity in the center of the gap is presented. Auto and cross correlation for the axial-flow velocity pattern are presented. The unsteady structure of the flow pulsation was visualized in the region of the gap in the parallel channel.

• Journal of Ship and Ocean Technology
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• v.6 no.2
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• pp.37-50
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• 2002

In the present numerical simulation of viscous free surface flow around a ship, two-fluids in-compressible Reynolds-averaged Navier-Stokes equations with the standard $\textsc{k}-\varepsilon$turbulence model are discretized on a regular grid by using a finite volume method. A local level-set method is introduced for capturing the free surface movement and the influence of the viscous layer and dynamic boundary condition of the free surface are implicitly considered. Partial differential equations in the level-set method are discretized with second order ENO scheme and explicit Euler scheme in the space and time integration, respectively. The computational results for the Series-60 model with $C_B=0.6$ show a good agreement with the experimental data, but more validation studies for commercial complicated hull forms are necessary.

• Journal of Hydrospace Technology
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• v.2 no.2
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• pp.1-13
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• 1996

This paper presents the result of a computational study on the wake characteristics of two tanker models, i.e. HSVA and Mystery hull forms. The focus of the study is on the distributions of axial, radial and tangential velocities of the two hull forms in way of the propeller, especially over the propeller disk. The effect of bilge vortices on the velocity distribution is also concerned. For the computation of stern and wake flows of the two hull farms, the incompressible Reynolds-Averaged Wavier-Stokes(RANS) equations are numerically solved by the second order finite difference method, which employs a four stage Runge-Kutta scheme with a residual averaging technique and the Baldwin-Lomax model. The calculated pressure distributions on the hull surface and the axial, radial and tangential velocity distributions over the propeller disk are presented for the two hull forms. Finally, the result of wake analysis for the computed wake distribution over the propeller disk is given in comparison with those for the experimental wake distribution fur the both hull forms.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.336-340
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• 2017

When supersonic flow is through an internal duct, there forms a flow structure called pseudo-shock. Pseudo-shock is a result of shockwave-boundary layer interaction(SBLI) and to simulate pseudo-shock correctly, one needs to correctly anticipate not only the strength of the shock but also the boundary layer behavior as well. In this study, pseud-shockwave structure at a rectangular duct will be numerically simulated using dedicated inlet boundary conditions to obtain accurate solution in terms of its structure and pressure rise pattern.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.2
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• pp.149-159
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• 2017

In this study, the numerical investigation of ship motions and added resistance at constant forward velocity of KVLCC2 model is presented. Finite volume CFD code is used to calculate three dimensional, incompressible, unsteady RANS equations. Numerical computations show that reliable numerical results can be obtained in head waves. In the numerical analyses, body attached mesh method is used to simulate the ship motions. Free surface is simulated by using VOF method. The relationship between the turbulence viscosity and the velocities are obtained through the standard ${\kappa}-{\varepsilon}$ turbulence model. The numerical results are examined in terms of ship resistance, ship motions and added resistance. The validation studies are carried out by comparing the present results obtained for the KVLCC2 hull from the literature. It is shown that, ship resistance, pitch and heave motions in regular head waves can be estimated accurately, although, added resistance can be predicted with some error.