• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2060-2065
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• 2003

Aeolian tone generation from a two dimensional circular cylinder is numerically investigated via direct numerical simulation and hydrodynamic-acoustic splitting method. All governing equation are spatially discretized with the sixth-order compact scheme and fourth-order Runge-Kutta method to avoid excessive numerical dissipations and dispersions of acoustic quantities. Comparisons of two results show that the previous splitting method can not accurately predict the aeroacoustic noise of wall bounded shear flow. In this study, a perturbation viscous term and a new energy equation have been developed. This modified splitting method accurately predicts aeroacoustic noise from wall-bounded shear flow. The present results agree very well with the direct numerical simulation solution.

• Journal of computational fluids engineering
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• v.5 no.2
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• pp.9-19
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• 2000

Transient aerodynamic response of an airfoil to a moving plane-flap is numerically investigated using the two-dimensional Euler equations with conservative Chimera grid method. A body moving relative to a stationary grid is treated by an overset grid bounded by a 'Dynamic Domain Dividing Line' which has an advantage for constructing a well-defined hole-cutting boundary. A conservative Chimera grid method with the dynamic domain-dividing line technique is applied and validated by solving the flowfield around a circular cylinder moving supersonic speed. The unsteady and transient characteristics of the flow solver are also examined by computations of an oscillating airfoil and a ramp pitching airfoil respectively. The transient aerodynamic behavior of an airfoil with a moving plane-flap is analyzed for various flow conditions such as deflecting rate of flap and free stream Mach number.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.916-925
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• 1988

The Navier-Stokes equations of the vorticity-stream-function form are solved numerically for the flow past a semicircular arc for Reynolds numbers in the range 0.1

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.345-348
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• 2002

The Flow patterns around two cylinders in various arrangements were studied by a discrete vortex method. The flow for the surface of each cylinder was represented by arranging bound vortices at adequate intervals. The viscous diffusion of fluid was represented by the random walk method. The vortex distributions, streaklines, timelines and velocity vectors around two cylinders were calculated for centre-to-centre pitch ratios of $P/D=1.5 and 2.5$, attack angles of ${\alpha}=0^{\circ},\;30^{\circ},\;60^{\circ}\;and\;90^{\circ}$, and Reynolds number of Re=1200. The results of simulation correspond to the photographs by flow visualization and the flow intereference between two cylinders in various arrangements was clearly visualized by a numerical simulation.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.807-810
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• 2002

The suitability of high-order accurate, central and upwind-biased compact difference schemes is evaluated for the large-eddy simulations of flows in complex geometry. Two flow geometries are considered: channel and circular cylinder. The effects of numerical dissipation and aliasing error on the evaluation of subgrid scale stress are investigated by extending the analysis by Ghosal (1) to centered and upwind compact schemes. It is shown that the failure of upwind schemes mainly comes from the aliasing error.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.1
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• pp.11-19
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• 2010

An approach to reduce cancellation errors of the temperature preconditioned Navier-Stokes equations is proposed. This approach is also applied to the conventional preconditioning methods. Adiabatic laminar viscous flows around a circular cylinder are calculated at different Mach numbers. It is shown that a redefinition of total enthalpy for reducing magnitude of the enthalpy remarkably alleviates cancellation problems of the temperature preconditioning.

• Structural Engineering and Mechanics
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• v.16 no.2
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• pp.115-126
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• 2003

A novel finite element model based on the incremental endochronic theory with the effect of temperature was developed in this study to explore the deformed behaviors of a flexible pavement material. Three mesh systems and two loading steps were used in the calculation process for a specimen of three-dimensional circular cylinder. Computational results in the case of an uni-axial compression test for temperatures at $20^{\circ}C$ and at $40^{\circ}C$ were compared with available experimental measurements to verify the ability of developing numerical scheme. The isotropic response and the deviatoric response due to the thermal effect were presented from deformations in different profiles and displacement plots for the entire specimen. The characteristics of changing asphalt concrete material under a specified loading condition might be seen clearly from the numerical results, and might provide an useful information in the field of road engineering.

• Ocean Systems Engineering
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• v.1 no.3
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• pp.207-222
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• 2011

A stabilized incompressible smoothed particles hydrodynamics (ISPH) method is utilized to simulate free falling rigid body into water domain. Both of rigid body and fluid domain are modeled by SPH formulation. The proposed source term in the pressure Poisson equation contains two terms; divergence of velocity and density invariance. The density invariance term is multiplied by a relaxed parameter for stabilization. In addition, large eddy simulation with Smagorinsky model has been introduced to include the eddy viscosity effect. The improved method is applied to simulate both of free falling vessels with different materials and water entry-exit of horizontal circular cylinder. The applicability and efficiency of improved method is tested by the comparisons with reference experimental results.

• Journal of the Society of Naval Architects of Korea
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• v.32 no.3
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• pp.51-61
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• 1995

A numerical method was developed to solve the Navies-Stokes equations for unsteady laminar flow around a hydrofoil. The present method used the finite-difference scheme in the collocated grid system and the pressure-Poisson method was employed to obtain divergence-free velocity field each time step. The numerical method was applied at first to laminar flow around a circular cylinder to confirm capability of the code. In the next, calculations were carried out for a hydrofoil in an unbounded fluid at the Reynolds number of $10^4$ in order to investigate unsteady phenomena with vortex shedding. The calculate results showed reasonable features about laminar vortex shedding around a streamlined body.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.3
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• pp.277-300
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• 2016

The motion of a floating body and the free surface flow are the most important design considerations for ships and offshore platforms. In the present research, a numerical method is developed to simulate the motion of a floating body and the free surface using a fixed rectilinear grid system. The governing equations are the continuity equation and Naviere-Stokes equations. The boundary of a moving body is defined by the interaction points of the body surface and the centerline of a grid. To simulate the free surface the Modified Marker-Density method is implemented. Ships advancing in regular waves, the interaction of waves by a fixed circular cylinder array and the response amplitude operators of an offshore platform are simulated and the results are compared with published research data to check the applicability. The numerical method developed in this research gives results good enough for application to the initial design stage.