• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.152-155
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• 2008

The blood flow characteristics have been closely related to various cardiovascular diseases, it is very important to predict them accurate enough in an efficient way. Thus, this paper proposes a one-dimensional spectral element model for the blood flow through blood vessels. The spectral element model is formulated by using the variational method. The nonlinear terms in spectral element model are all treated as the pseudo-force and an iterative solution method is applied in the frequency domain.

• International Journal of Fluid Machinery and Systems
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• v.4 no.4
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• pp.375-386
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• 2011

The turbo-type blood pump studied in this paper has an impeller that is magnetically suspended in a double volute casing. The impeller rotates with minimal fluctuations caused by fluid and magnetic forces. In order to improve stability of the rotating impeller and to facilitate long-term use, a careful investigation of the pressure fluctuations and of the fluid force acting on the impeller is necessary. For this purpose, two models of the pump with different volute cross-sectional area are designed and studied with computational fluid dynamics software. The results show that the fluid force varies with the flow rate and shape of the volute, that the fluctuations of fluid force decrease with increasing flow rate and that the vibratory movement of the impeller is more efficiently suppressed in a narrow volute.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.2 s.152
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• pp.93-100
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• 2007

Post swirl stator is an energy saving device to recover rotational energy of the propeller. To optimize the performance of post swirl stator in container vessels, computational fluid dynamics using body force method was introduced. A commercial code Fluent was used in conjunction with body force distributed on the surface of actuator disk which is located in the propeller plane to optimize pitch angle of the post swirl stator blade. This study showed that CFD is an important tool to simulate flow behind ship with propeller, rudder and post swirl stator.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.193-200
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• 1999

Since Broms and Bennermark(1967) suggested the face stability criterion based on laboratory extrusion tests and field observations, the face stability of a tunnel driven in cohesive material has been studied by several authors. And recently, more general solution for the tunnel front is given by Leca and Panet(1988). They adopted a limit state design concept to evaluate the face stability of a shallow tunnel driven into cohesionless material and showed that the calculated upper bound solution represented the actual behavior reasonably well. In this study, two factors are simultaneously considered for assessing tunnel face stability: One is the effective stress acting on the tunnel front calculated by upper bound solution; and the other is the seepage force calculated by numerical analysis under the condition of steady state ground water flow. The model tests were performed to evaluate the seepage force acting on the tunnel front and these results were compared with results of numerical analysis. Consequently, the methodology to evaluate the stability of a tunnel face including limit analysis and seepage analysis is suggested under the condition of steady state ground water flow.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.4
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• pp.511-519
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• 2003

A stratified flow is simulated using the finite difference lattice Boltzmann method (FDLBM). The effect of body force (gravity) in a simple one-dimensional model with the lattice BGK 9 velocity is examined. The effect of body force in the compressible fluid is greatly different from that of the incompressible fluid In a compressible fluid under gravitational force, the density stratification is not sufficient and the entropy stratification is essential. The numerical simulation of a line sink compressible stratified flow in two-dimensional channel is also carried out. The results show that selective withdrawal is established when the entropy of the upper part increases. and the simulated results using FDLB method are satisfactory compared with the theoretical one.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.680-683
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• 2002

In this paper, it has been investigated that the design and simulation of vacuum pump driven by linear motor. Vacuum pump consists of unified plunger and piston part, coils, inlet valve and outlet valve. Operating principal of vacuum pump show that air is to flow to go inside through the inlet valve when the magnetic force (16N) is exerted, whereas, air is to flow to go outside through outlet valve when spring farce (14.8N) is exerted. The results of simulation. it was turned out that reached vacuum pressure was about -0.55 bar at 150 seconds, magnetic force was loaded with 16 Newton, displacement of actuator was about 8mm.

• Wind and Structures
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• v.30 no.3
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• pp.245-260
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• 2020

Wind load and responses are the major factors which govern the design norms of tall buildings. Corner modification is one of the most commonly used minor shape modification measure which significantly reduces the wind load and responses. This study presents a comparison of wind load and pressure distribution on different corner modified (chamfered and rounded) Y plan shaped buildings. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and Shear Stress Transport (SST), are used in the simulation of the building and the data are compared with the previous experimental results in a similar flow condition. The variation of the flow patterns, distribution of pressure over the surfaces, force and moment coefficients are evaluated and the results are represented graphically to understand the extent of nonconformities due to corner modifications. Rounded corner shape is proving out to be more efficient in comparing to chamfered corner for wind load reduction. The maximum reduction in the maximum force and moment coefficient is about 21.1% and 19.2% for 50% rounded corner cut.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.44-48
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• 2002

In lateral ground flow, slope stability, and land slide problems, H-piles have often been used, on a horizontally deforming ground, to prevent the failure of mass of soil in a downward and outward movement of a slope. Here, theoretical equations are derived to estimate the lateral force, assuming that the Mohr-Coulomb's plastic states occur in the ground, just around H-piles. In this study, some model experiments were performed to check the lateral forces determined from theoretical equations, using several pile widths, heights and various interval ratios between H-piles for sand specimens. The solution of the theoretical equation, derived from previous studies, showed reasonable characteristics for constants of soil, as well as for the interval, widths, and heights of H-Pile.

• Atmosphere
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• v.23 no.4
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• pp.513-517
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• 2013

In this study, it is first intended to simulate the vertical profile of atmospheric flow in a short wind tunnel. In order to accomplish it, proper devices are designed properly to reduce freestream flow momentum and it is confirmed from the measured velocity profile using hot-wire anemometer that momentum flux of the tunnel free stream can be reduced and desired atmospheric boundary can be created. Second, experiments are performed to identify influences of a surrounding structure measuring correct wind velocity by an anemometer, which are located nearby due to area limitation in actual airport and correction factors are proposed from experimental results. One of findings is that in order to limit the velocity attenuation due to a nearby structure under 10%, wind velocity measuring equipment should be installed at least 6 times of the structure height away from the structure of concern.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.635-638
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• 2000

It is necessary to work on a vertical plane of workpiece in order to produce a large structure like a ship. These works can be automated by using the robot with permanent magnet wheels. We developed the permanent magnet wheel which can be used by a mobile robot and easily detached. We enhanced an adhesive power by restricting the occurrence direction of magnetic flow. And we also developed a method which weakens adhesive magnetic force by changing magnetic flow with metal pins. We used the load cell and the gaussmeter to measure the characteristics of the adhesive force and magnetic force. We obtained the result that the adhesive power is reduced to 1/3 of normal state by using 4 inducing pins.