• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1371-1376
• /
• 2004

Flow analysis of automobile front-end cooling fan are numerically investigated. The Navier-Stokes equations and the continuity equation are solved in the flow domain. The Reynolds stresses are modelled using the $k-{\varepsilon}$ turbulence model. Flow and pressure characteristics around the fan are investigated. The pressure sharply increases through the fan. Pressure variations on the pressure and suction sides of the fan are well represented in the calculations. The flow streamlines in the blade passage are nearly parallel to the blade.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.12
• /
• pp.3345-3356
• /
• 1994

A general purpose program, TURBO-3D, for the analysis of 3-D fluid flow in complex geometry has been developed, which employs a standard $k-\varepsilon$ turbulence model and a general nonorthogonal grid system. For the purpose of verification of the program and testing the applicability, turbulent flows in an S-shaped diffuser and turbulent flows over an backward facing step are solved and compared with the earlier results. Comparison with the results by the STAR-CD program has been also made for the same flow configuration and grid structure. The agreements are excellent and hence the program has been verified. Since the present program is applicable only on limited flow phenomena and lacks the pre-and post processor, further improvements toward these directions are being made.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.10
• /
• pp.1309-1316
• /
• 2000

A surface flow visualization of a MIRA notchback reference car was conducted using a 1/4 -scale model in the POSTECH wind tunnel. The flow separation and reattachment phenomen a around A-pillar, C-pillar, backlight, and trunk were discussed with the help of the distributions of singular points such as nodes, saddles, and spiral foci. The locations of the singular points on the trunk and the backlight from experimental results are compared with those of CFD results using the turbulence modeling of RNG k -${\varepsilon}$ and RSM.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.1 no.1
• /
• pp.1-13
• /
• 1993

The three-dimensional numerical analysis for in-cylinder flow of four-valve engine without intake port has been successfully computed. These computations have been performed using technique of the general coordinate transformation based on the finite-volume method and body-fitted non-orthogenal grids using staggered control volume and covariant variable as dependent one. Computations are started at intake valve opening and are carried through top-dead-center of compression. A k-$\varepsilon$model is used to represent turbulent transport of momentum. The principal study is the evolution of interaction between mean flow and turbulence and of the role of swirl and tumble in generating near TDC turbulence. Results for three different inlet flow configuration are presented. From these results, complex flow pattern may be effective for promoting combustion in spark-ignition engines and kinetic energy of mean flow near TDC is well converted into turbulent kinetic energy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.10 no.1
• /
• pp.108-117
• /
• 1998

This study was performed to analyze the fluid flow characteristics and the temperature distribution of the aquarium for fish breeding. In this study, the finite volume method and turbulence k-$\varepsilon$ model with the SIMPLE computational algorithm are used to study the water flow in the aquarium. The calculation parameters are the circulating flow rate and the basin depth, and the experiments were carried out for the water flow visualization This numerical analysis gives reasonable velocity distributions in good agreement with the experimental data. As the results of the three dimmentional simulations, the sectional mean velocity increased as the sectional mean temperature increases for constant basin depth, and the mean velocity increased more rapidly for small basin depth than that of large basin depth, The mean velocity and temperature can be expressed as the function of the circulating flow rates and the basin depth.

• Communications for Statistical Applications and Methods
• /
• v.5 no.3
• /
• pp.855-868
• /
• 1998

For a random sample of size n from general linear model, $Y_i= heta(X_i)+varepsilon_i,;let Y_{in}$ denote the ith oder statistics of the Y sample values. The X-value associated with $Y_{in}$ is denoted by $X_{[in]}$ and is called the concomitant of ith order statistics. The estimator of the location of a maximum of a regression function, $ heta$($\chi$), was proposed by (equation omitted) and was found the convergence rate of it under certain weak assumptions on $ heta$. We will discuss the asymptotic distributions of both $ heta(X_{〔n-r+1〕}$) and (equation omitted) when r is fixed as nolongrightarrow$\infty$(i.e. extreme case) on the basis of the theorem of the concomitants of order statistics. And the will investigate the asymptotic behavior of Max｛$\theta$( $X_{〔n-r+1:n〕/}$ ), . , $\theta$( $X_{〔n:n〕}$)｝as an estimator for the peak of a regression function.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.11a
• /
• pp.344-352
• /
• 2006

Evacuation performance, starting transient, and plume blowback at diffuser breakdown of a straight cylindrical supersonic exhaust diffuser with no externally supplied secondary flow are investigated. Pressure records in the transitional periods are measured by a small-scale cold-gas simulator. Flow-fields evolving in the diffuser-type ejector are solved by preconditioned Favre-averaged Navier-Stokes equations with a low-Reynolds number $k-{\varepsilon}$ turbulence model edited for turbulence compressibility effects. The present RANS method is properly validated with measured static wall pressure distributions and evacuation level at steady operation as well as the pressure records during the transition regime.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2003.10a
• /
• pp.108-113
• /
• 2003

The numerical research has been done for the transverse jet behind a rearward- facing step in turbulent supersonic flow without chemical reaction. The purpose of transverse jet is used to improve mixing of the fuel in the combustor. Two- dimensional unsteady flowfields generated by slot injection into supersonic flow are numerically simulated by the integration of Navier-Stokes equation with two-equation k - $\varepsilon$ turbulence model. Numerical methods are used high-order upwind TVD scheme. Eight cases are computed, comprising slot momentum flux ratios and slot position at downstream of the step. The flow is very similar to the cavity flow, because the jet is like an obstacle. Therefore, the numerical results show the periodic phenomenon.

• Journal of ILASS-Korea
• /
• v.8 no.1
• /
• pp.1-8
• /
• 2003

The flow analysis of the axial fan of rotary burner was performed by SIMPLE(Semi Implicit Method for Pressure Linked Equations) algorithm and finite volume mothod performed in the case of 3-D, incompressible, turbulent flow. In this study, the coordinate transformation was adapted for the complex geometry of axial fan, and the standard $k-{\varepsilon}$ model and wall function method were used for analysis of turbulent flow. Multi-block grid system was used for flow field and divided into four domains such as the inlet, outlet, flow field of rotating vane, and tip clearance. Fan rotation was simulated by rotational motion using MRF(Multiple Rotating Reference Frame) in steady, incompressible state flow.

• 한국전산유체공학회:학술대회논문집
• /
• 1998.11a
• /
• pp.133-140
• /
• 1998

A Navier-Stokes code based on a unstructured finite volume method is used to simulate the MIT flapping foil experiment. A low Reynolds number $k-{\varepsilon}$ turbulence model is used to close the Reynolds averaged Navier-Stokes equations. Computations are carried out for a domain involving two flapping foils and a downstream hydrofoil. The computational domain is meshed with unstructured quadrilateral elements, partly structured. Numerical solutions show good agreement with experiment. Unsteadiness inside boundary layer is entrained when a unsteady vortex impinge on the blade surface. It shoves that local peak value inside the boundary layer and also local minimum near the edge of boundary layer as it developes along the blade surface. The unsteadiness inside the boundary layer is almost isolated from the free stream unsteadiness and being convected at local boundary layer speed, less than the free stream value.