• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.3
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• pp.249-262
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• 1989

We present a method of boundary extraction of moving objects. We propose four methods for detecting moving edge pixels which can be located on the boundaries of moving objects. We select the best one after we test the above four methods to real image sequences. The portion of the boundaries of moving objects which is marked as moving edge pixels is searched along the moving edge pixels with simple heuristics. And the end points of the resultant line segments are utilized as the start points of the secon stage heuristic search. This second stage search is performed for the boundaries of moving objects which is not marked as moving edge pixels due to various reasons. We test our algorithm for two real sequences and we find that this simple algorithm has good performance.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.539-546
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• 2003

The numerical model of the flow analysis by finite element technique is described. The Galerkin method is employed for spatial discretization Two step explicit finite element scheme is used to discretize the time function, which has advantage in problems treating large numbers of elements and unsteady state. Two dimensional hydrodynamic model considering moving boundary condition is developed. Also it applied flow model which develop on flow portion of ideal fluid in the model flume and verified, and the results of this study confirm the efficiency of moving boundary treatment in Jeju harbor. The computed results have shown the good adaptability of moving boundary condition From these studies, it can be concluded that the present method is a useful and effective tool in tidal flow analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.12
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• pp.924-930
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• 2008

Immersed boundary method (IBM) is the most effective method to overcome the disadvantage of LBM (Lattice Boltzmann Method) related to the limitation of the grid shape. IBM also make LBM possible to simulate flow over complex shape of obstacle without any treatment on the curved boundary. In the research, IBLBM was used to perform LBM simulation of a flow over a moving circular cylinder to determine the flow feature and aerodynamics characteristic of the cylinder. To ascertain the applicability of IBLBM on the moving obstacle near the wall, it was first simulated for the case of the flow over a fixed circular cylinder in a channel and the results were compared against the solution of moving cylinder in the channel using IBLBM. The simulations were performed in a moderate range of Reynolds number at each moving cylinder to identify the flow feature and aerodynamic characteristics of circular cylinder in a channel. The drag and lift coefficients of the cylinder were calculated from the simulation results. We have numerically confirmed that the critical Reynolds number for vortex shedding is Re=50 and the result is the same as the case of fixed cylinder. As the cylinder approaching to a wall (${\gamma}<2.5$), the 2nd vortex is developed by interacting with the wall boundary-layer vorticity. When the cylinder is very closed to the wall, ${\gamma}<0.6$, the cylinder acts like blockage to block the flow between the cylinder and wall so that the vortex developed on the upper cylinder elongated and time averaged lifting and drag coefficients abruptly increase.

• Journal of applied mathematics & informatics
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• v.25 no.1_2
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• pp.67-83
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• 2007

The characteristics of steady two-dimensional laminar boundary layer flow of a viscous and incompressible fluid past a moving wedge with suction or injection are theoretically investigated. The transformed boundary layer equations are solved numerically using an implicit finite-difference scheme known as the Keller-box method. The effects of Falkner-Skan power-law parameter (m), suction/injection parameter ($f_0$) and the ratio of free stream velocity to boundary velocity parameter (${\lambda}$) are discussed in detail. The numerical results for velocity distribution and skin friction coefficient are given for several values of these parameters. Comparisons with the existing results obtained by other researchers under certain conditions are made. The critical values of $f_0$, m and ${\lambda}$ are obtained numerically and their significance on the skin friction and velocity profiles is discussed. The numerical evidence would seem to indicate the onset of reverse flow as it has been found by Riley and Weidman in 1989 for the Falkner-Skan equation for flow past an impermeable stretching boundary.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.6
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• pp.415-423
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• 1990

In a laboratory model the response of the boundary layer flow over topography is studied in a rotating sliced cylinder by employing the source-sink analogy with Ekman layer dynamics. The boundary layer flow is produced by two different fluid. In the first experiment homogeneous fluid is used both for the source and the working fluid of the container. In the second experiment a denser fluid is used for the source with the same working fluid. For the homogeneous western boundary layer flow both the northward and the southward flow were affected by the topography(ridge) to produce a cyclonic motion near the ridge. When woughward moving heavy boundary flow of slower speed and the northward moving faster flow were present at the same time, the splitting of southward flow and the separating of the northward flow were observed with a cyclonic motion at the ridge. The most important factor that influence production of the cyclonic motion has been turned out to be the presence of the topography in the western boundary layer. In particular the role of the southward moving heavy flow over the interior flow pattern was found to be very significant.

• Journal of computational fluids engineering
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• v.10 no.1
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• pp.24-30
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• 2005

Unstructured grid system is suitable for flows of complex geometries. For problems with moving boundary walls, the grid system must be time-dependently changing and deforming according to the movement of the boundaries when we use a body fitted grid system. In this paper, a new moving-grid finite-volume method on unstructured grid system is proposed and developed for unsteady compressible flows with shock waves. To assure geometric conservation laws on moving grid system, a control volume on the space-time unified domain is adopted for estimating numerical flux. The method is described and applied for two-dimensional flows.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.7
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• pp.807-818
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• 1988

This paper proposes new algorithms for the estimation of displacement vector and moving object extraction using difference picture. First, the relations between the boundary of moving objects in two consecutive image and the boundary of difference picture regions are analyzed, then displacement vector estimation algorithm is proposed. Using the estimated displacement vector, moving objects are directly extracted from difference picture. Since the proposed algorithms do not process gray-valued image, they have a short processing time and are suitable to real time processing. From the experimental results, we observed that, if difference picture is wel extracted, the proposecd algorithms work well even in the circumstances of complex background, fast or slow motion, rotation etc., including occlusion where is not moving area.

• International Journal of Control, Automation, and Systems
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• v.3 no.4
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• pp.601-611
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• 2005

In this paper, an active vibration control of a tensioned, elastic, axially moving string is investigated. The dynamics of the translating string are described with a non-linear partial differential equation coupled with an ordinary differential equation. A right boundary control to suppress the transverse vibrations of the translating continuum is proposed. The control law is derived via the Lyapunov second method. The exponential stability of the closed-loop system is verified. The effectiveness of the proposed control law is simulated.

• Journal of Mechanical Science and Technology
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• v.14 no.3
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• pp.358-368
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• 2000

The hydrodynamic stability of the Karman boundary-layer flow due to a rotating disk has been numerically investigated for moving disturbance waves. The disturbed flow over a rotating disk can lead to transition at much lower Re than that of the well-known Type I instability mode. This early transition is due to the excitation of the Type II instability mode of moving disturbances. Presented are the neutral stability results concerning the two instability modes by solving new linear stability equations reformulated not only by considering whole convective terms but by correcting some errors in the previous stability equations. The reformulated stability equations are slightly different with the previous ones. However, the present neutral stability results are considerably different with the previously known ones. It is found that the flow is always stable for a disturbance whose dimensionless wave number k is greater than 0.75.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2260-2265
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• 2005

In this paper, an active vibration control of a tensioned elastic axially moving string is investigated. The dynamics of the translating string are described by a non-linear partial differential equation coupled with an ordinary differential equation. A time varying control in the form of right boundary transverse motions is proposed in stabilizing the transverse vibrations of the translating continuum. A control law based on Lyapunov's second method is derived. Exponential stability of the closed-loop system is verified. The effectiveness of the proposed controller is shown through simulations.