• 한국전산유체공학회:학술대회논문집
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• 2000.05a
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• pp.51-59
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• 2000

The Interactions of shock wave with turbulent boundary layers in high-speed flows cause complex flowfields which result in increased adverse pressure gradients, skin friction and temperature. Accurate and reliable prediction of such phenomena is needed in designing high-speed propulsion systems. Such analyses of the complex flowfields require sophisticated numerical scheme that can resolve interactions between shock wave and boundary layers accurately. Therefore the purpose of the present. article is to introduce an accurate and efficient mixed explicit-implicit generalized Galerkin finite element method. To demonstrate the validity of the theory and numerical procedure, several benchmark cases are investigated.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1972_1973
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• 2009

한의학에서는 사상체질(태양인, 태음인, 소양인, 소음인) 구분을 위해 손등피부의 특징 중 하나인 거침/미끄러움을 이용하여 한의사의 주관적인 판단으로 사상체질을 구분해 왔다. 한의사의 손등피부 거칠기의 주관적인 촉진을 정량적 및 객관적으로 진단하기 위하여 피부마찰력진단기기를 개발하였다. 피부마찰력진단기기는 3축 로드셀 센서를 이용하여 한의사가 손등피부를 만지는 것과 같은 움직임으로 측정하며, 측정된 물리량 중 피부의 거침/미끄러움으로 계산되는 운동마찰계수 값을 이용하여 손등피부의 특성을 나타내었다. 본 연구에서는 피부마찰력 진단기기를 이용하여 객관적으로 손등피부의 특성을 측정해 보고 사상체질 진단의 객관적인 지표를 찾는 것을 목표로 한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.11
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• pp.1418-1425
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• 1999

Flow over a protruding surface is investigated using numerical simulation. We consider flow between two parallel plates with a cube mounted on one side of the channel. As the flow approaches the cube, the adverse pressure gradient produces three-dimensional boundary-layer separation, resulting In the formation of horseshoe vortices. The objective of our study is to clarify both the steady and the unsteady characteristics of the vortex system. As the Reynolds number increases, the structure of the vortices near the cube becomes complex and the number of vortices increases. The distribution of skin friction on the cube-mounted wall reflects the effect of the horseshoe vortices. All these results are consistent with the experimental findings currently available.

• Journal of the Korean Society of Visualization
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• v.14 no.1
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• pp.27-32
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• 2016

The reduction of $CO_2$ emissions has been a key target in the Marine Industry since the IMO's Marine Environment Protection Committee published its findings in 2009. The representative emission index is termed as the EEDI (Energy Efficiency Design Index) for the new ships. Among various flow control techniques ever proposed, the air lubrication method is the one of most promising one in terms of practical applicability. The present study examines the basic characteristics of the flat plate test with intention of applying the air lubrication technology to the reduction of the resistance of a ship. Image analysis technique is proposed as a tool to quantify the effectiveness of the air lubrication method.

• International Journal of Aeronautical and Space Sciences
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• v.1 no.1
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• pp.36-47
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• 2000

Three-dimensional compressible turbulent flow fields within the passage of a diffusing S-duct have been simulated by solving the Navier-Stokes equations with SIMPLE scheme. The average inlet Mach number is 0.6 and the Reynolds number based on the inlet diameter is $1.76{\times}10^6$ The extended $k-{\varepsilon}$ turbulence model is applied to modeling the Reynolds stresses. Computed results of the flow in a circular diffusing S-duct provide an understanding of the flow structure within a typical engine inlet system. These are compared with experimental wall static-pressure, total-pressure fields, and secondary velocity profiles. Additionally, boundary layer thickness, skin friction values, and streamlines in the symmetric plane are presented. The computed results depict the interaction between the low energy flow by the flow separation and the high energy flow by the reversed duct curvature. The computed results obtained using the extended $k-{\varepsilon}$ turbulence model.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.1
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• pp.83-102
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• 2015

The present paper analyses the radiation effects of mass transfer on steady nonlinear MHD boundary layer flow of a viscous incompressible fluid over a nonlinear porous stretching surface in a porous medium in presence of heat generation. The liquid metal is assumed to be gray, emitting, and absorbing but non-scattering medium. Governing nonlinear partial differential equations are transformed to nonlinear ordinary differential equations by utilizing suitable similarity transformation. The resulting nonlinear ordinary differential equations are solved numerically using Runge-Kutta fourth order method along with shooting technique. Comparison with previously published work is obtained and good agreement is found. The effects of various governing parameters on the liquid metal fluid dimensionless velocity, dimensionless temperature, dimensionless concentration, skin-friction coefficient, Nusselt number and Sherwood number are discussed with the aid of graphs.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.18 no.3
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• pp.245-256
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• 2014

This work is focused on the boundary layer and heat transfer characteristics of hydromagnetic flow over a stretching sheet with variable thickness. Steady, two dimensional, nonlinear, laminar flow of an incompressible, viscous and electrically conducting fluid over a stretching sheet with variable thickness and power law velocity in the presence of variable magnetic field and variable temperature is considered. Governing equations of the problem are converted into ordinary differential equations utilizing similarity transformations. The resulting non-linear differential equations are solved numerically by utilizing Nachtsheim-Swigert shooting iterative scheme for satisfaction of asymptotic boundary conditions along with fourth order Runge-Kutta integration method. Numerical computations are carried out for various values of the physical parameters and the effects over the velocity and temperature are analyzed. Numerical values of dimensionless skin friction coefficient and non-dimensional rate of heat transfer are also obtained.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.15-23
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• 1999

K-$\omega$ model is used for simulation of flowfield around the cylinderical afterbody. In addition to two-equation turbulence model, modification terms for the compressibility effects are applied to the simulation. Although the estimations of the skin friction and the surface pressure distribution at hypersonic ramp flowfield were satisfactory, the result of the simulation with the modifications for this flowfield is worse than that of the original K-$\omega$ model. The compressiblility modification terms do negative effects on the estimation. The basic research on the turbulence model for the compressible flowfield has to be further conducted.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05b
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• pp.63-66
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• 2011

The aim of this study is to estimate the field applicability of PBFM to replace in-site soil with pile backfill used to replace the existing cement paste. As results, the flowability, segregation and bleeding, and bond strength of PBFM was a good performance than that of the existing cement paste. But the skin friction of pile by Pile Driving Analyzer (PDA) and compressive strength was slightly decreased than that of the existing cement paste. However, as pile backfill materials, and in terms of economics and environment, the applicability of PBFM is considered very effective.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.1-6
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• 1998

From surface flow visualization on a MIRA notchback reference model using oil flow technique, the topology of the singular points of the skin friction lines are delineated. Separation and reattachment lines at the front screen, at the A-pillar, at the C-pillar and on the rear side of the car including the trunk have been identified. It is worth to mention that two vortices emerging from the top of the trunk coil in the opposite direction as that vortices starting from the C-pillar edge. The positions of the singular points and the separation and reattachment lines and the foci of the vortices provide a sensitive database for validation of CFD-codes