• The KSFM Journal of Fluid Machinery
• /
• v.9 no.3 s.36
• /
• pp.14-21
• /
• 2006

Leakage reduction through annular type seals of turbomachinery is necessary for enhancing their efficiency and the precise prediction method of seal leakage is needed. The analysis based on Bulk-flow concept has been mainly used in predicting seal leakage. However, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved for improving the prediction of seal leakage. FLUENT 6 which is commercial CFD(Computational Fluid Dynamics) code based on FVM(Finite Volume Method) and SIMPLE algorism has been used to analyze leakage of various non-contact-type seals in this presentation. Comparing with the results of Bulk-flow model analysis and experiment, the result of CFD analysis shows good agreement with that of existing theoretical analysis for the incompressible grooved seal and compressive plain and staggered seal. The CFD analysis also shows improvement on the leakage prediction of the incompressible plain seal and compressive see-through-type labyrinth seal.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.54-57
• /
• 2011

In this paper we present an algorithm about how to simulate two dimensional dam breaking with lattice Boltzmann method (LBM). LBM considers a typical volume element of fluid to be composed of a collection of particles that represented by a particle velocity distribution function for each fluid component at each grid point. We use the modified Lattice Boltzmann Method for incompressible fluid. This paper will represent detailed information on single phase flow which considers only the water instead of both air and water. Interface treatment and conservation of mass are the most important things in simulating free surface where the Interface is treated by mass exchange with the water region. We consider the surface tension on the interface and also bounce back boundary condition for the treatment of solid obstacles. We will compare the results of the simulation with some methods and experimental results.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.4
• /
• pp.25-30
• /
• 2010

Flow analysis and performa nce evaluation have been performed for a ventilation axial-flow fan with different positions of the motor. Two different positions of motor have been tested; one is in front of the impeller and the other is behind the impeller. Flow analyses are performed by solving three-dimensional Reynolds-averaged Navier-Stokes equations through a finite-volume solver. Preliminary numerical calculations are carried out to test the performances of different turbulence models, i.e., SST model, k-$\omega$ model, and k-$\varepsilon$ model with and without using empirical wall function in the flow analysis. The validation of numerical analyses has been performed in comparison with the experimental data. The numerical results for the performance characteristics of the ventilation axial-flow fan with two different positions of the motor have been presented.

• Journal of Advanced Research in Ocean Engineering
• /
• v.3 no.2
• /
• pp.75-82
• /
• 2017

With the development of computational fluid dynamics (CFD), studies on shipbuilding and maritime issues including free-surface wave flow have been conducted. Although the volume of fluid (VOF) and level-set methods are widely used to study the free-surface wave flow, disadvantages exist. In particular, it takes a long time to obtain solutions. In this study, a free-surface capturing code is developed for ship and offshore structures. The developed code focuses on accuracy and computation time. Open source CFD libraries, termed OpenFOAM, are used to develop the code. The results obtained using the developed code are compared with those obtained using interFoam. The results show that the developed code could be used to capture the free-surface wave flow without numerical diffusion; moreover, the accuracy of the developed code is largely the same as that of interFoam.

• 한국전산유체공학회:학술대회논문집
• /
• 2011.05a
• /
• pp.291-293
• /
• 2011

In this paper, the problem of transonic aerodynamic characteristics of a NACA0012 airfoil is numerically investigated in the inviscid gas-droplet two-phase flow with the compressible two-fluid model. In the present study, the airfoil flight in the cloud is simulated by taking account of the viscous drag of the droplets, the heat transfer, the phase change, and the droplet fragmentation The two-fluid equation system is solved by the fractional-step method and the WAF-HIL scheme. The effects of size and volume fraction of the droplets on the flow characteristics of the airfoil in the cloud are elaborated and discussed.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.5
• /
• pp.17-21
• /
• 2010

A volumetric gear pump is often used in extensive industrial applications to provide both high pressure and sufficiently high flow rate by physical displacement of finite volume of fluid with each revolution. To better understand the unsteady flow characteristics within the pump, numerical simulations were conducted by using moving dynamic meshing (MDM) techniques in commercially available CFD software, FLUENT. The effects of rotor clearance size and rotational speed of rotor on the flow characteristics, specially the temporal variation of velocity and pressure field, which is a main source of flow noise, was investigated. The results showed that significant reverse flow is developed in the rotor clearance and that its size is one of the most important factors affecting flow characteristics and pressure pulsation.

• Journal of Korea Foundry Society
• /
• v.13 no.5
• /
• pp.424-431
• /
• 1993

A Numerical technique has been developed for the coupled heat transfer and fluid flow calculation during the casting process. In this method the SMAC technique was coupled with the concept of Volume of Fluid(VOF) to calculate melt free surface and velocity profiles within the melt, and the Energy Marker method coupled with the finite difference method was proposed for the convective and conductive heat transfer analysis in the casting. When comparing numerical calculations with experimental observations, a close correlation was evident. It has been shown that this technique is useful for proper gating and casting design, especially for thin-walled castings.

• Journal of Chest Surgery
• /
• v.47 no.3
• /
• pp.313-316
• /
• 2014

Airway obstruction after esophageal surgery is quite rare, and few such cases have been reported. A 57-year-old woman who underwent the Ivor Lewis procedure for esophageal carcinoma complained of a sudden onset of severe dyspnea on postoperative day 3. Chest computed tomography scan revealed that the collection of a large volume of mediastinal fluid caused marked luminal compression on the trachea and the gastric conduit. Explorative thoracotomy revealed a clear serous fluid in the space between the trachea and the gastric conduit, and all respiratory symptoms were relieved after the fluid was drained. The possibility of tracheal compression by loculated effusion, such as chyloma, should be considered in a patient who complains of respiratory deterioration after esophageal surgery.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.908-913
• /
• 2002

An analytical study is presented on the hydroelastic vibration of two rectangular identical plates coupled with a bounded fluid by using the finite Fourier series expansion method. It is observed that the two contrastive modes, the so called the out-of-phase and in-phase modes appear. The proposed analytical method is verified by observing a good agreement to three dimensional finite element analysis results. All natural frequency of the in-phase modes can be predicted well by the combination of the dry beam modes. The theoretical prediction for the out-of-phase mode can be improved by using the polynomial functions satisfying the plate boundary conditions and fluid volume conservation instead of using dry beam modes.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.2
• /
• pp.18-23
• /
• 2010

This paper presents a procedure for the aerodynamic and aeroacoustic characteristics of a sirocco fan. For the aerodynamic and aeroacoustic analyses of the sirocco fan, three-dimensional steady and unsteady Reynolds-averaged Navier-Stokes equations are solved with a shear stress transport turbulence model for turbulence closure. The flow analyses were performed on a hexahedral grid using a finite-volume solver. The validation of the numerical results is performed by comparing with experimental data for the pressure, efficiency and power. The internal flow analyses of the sirocco fan are performed to understand the unstable flow phenomenon on the casing for the wall pressure and internal flow characteristics at each position. It was found that fluctuation of pressure and locally concentrated noise source are observed near the cut-off and expansion regions of the casing.