• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.10 s.241
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• pp.1336-1343
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• 2005

The detection mechanism of the flaw for the nondestructive testing using eddy current is related to the interaction of the induced eddy currents in the test specimen with flaws and the coupling of these interaction effects with the moving test probe. In this study, the two-dimensional electromagnetic finite element analysis(FEM) fur the eddy current signals of the aluminum plate with different depth of surface cracks is described and the comparison is also made between experimental and predicted signals analyzed by FEM. In addition, the characteristics of attenuation of the eddy current density due to the variation of the depth of a conductor are evaluated. The effective parameters for the application of eddy current technique to evaluate surface cracks are discussed by analyzing the characteristics of the eddy current signals due to the variation of crack depths.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.10
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• pp.760-766
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• 2003

This paper is concerned with the eddy current damper which can be used to enhance the damping of the host structure. The operating principle of the eddy current damper is first explained in detail. The dynamic interaction between the magnets and the copper plate produces eddy current thus resulting in the damping force. By attaching the eddy current damper to the host structure, the damping of the total structure can be increased so that vibrations can be suppressed. The advantage of the eddy current damper is that it doesn't require any electronic devices and power supply The effect of the eddy current damper on the global dynamic characteristics of the structure is investigated by considering the cantilever with the eddy current damper. Experimental results show that the eddy current damper is an effective device for vibration suppression.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.136-141
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• 2003

This paper is concerned with the eddy current damper which can be used to enhance the damping of the host structure. The operating principle of the eddy current damper is first explained in detail. The dynamic interaction between the magnets and the copper plate produces eddy current thus resulting in the damping force. By attaching the eddy current damper to the host structure, the damping of the total structure can be increased so that vibrations can be suppressed. The advantage of the eddy current damper is that it doesn't require any electronic devices and power supply. The effect of the eddy current damper on the global dynamic characteristics of the structure is investigated by considering the cantilever with the eddy current damper. Experimental results show that the eddy current damper is an effective device for vibration suppression.

• Journal of the korean society of oceanography
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• v.37 no.1
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• pp.20-26
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• 2002

The offshore extension of the East Korean Warm Current (EKWC) mostly turns anti-cyclonically around the Ulleung Warm Eddy (UWE). This fact needs to be dynamically explained because a rectilinear stream past a circular cylinder is normally expected to have a flow pattern symmetric about the stream axis. For this purpose, a simple analytical model is presented in this paper. This model shows that the EKWC's tendency to be anti-cyclonic around the UWE is due to the anti cyclonic circulation generated around the UWE. This tendency results from the geostrophic adjustment between the UWE and the ambient EKWC water. As the strength of the UWE decreases, relative to the EKWC, this model shows that the flow pattern gradually changes from circular to rectilinear.

• Journal of the Korean Society for Nondestructive Testing
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• v.11 no.1
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• pp.7-12
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• 1991

The multi-frequency eddy current technique has been used for evaluation of various type of defects in tubings. However, this technique is not sufficient to detect and evaluate the defect in tubings if the defect is located in the geometrically complicated area(e. g. tube support plate, anti-vibration bar, tubesheet area) and mixing residue signal is significant to the defect signal. In order to improve the reliability of the multi-frequency eddy current technique, the effect of the interaction of mixing residue after frequency mixing with a function of distances between the defect and the tube support plate boundary has been analyzed theoretically. The experimental results have been discussed with the theoretical developments. The calculation shows the interaction between the two neighboring signal sources could be significant within the range of approximately 1.0mm with the experimental condition.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.389-392
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• 2020

In order to accurately predict the losses in the power cable, analysis of the eddy current losses in the metal sheath is required. The copper loss is easily calculated by the resistance and current of the conductor, but it is difficult to measure and predict the eddy current generated from the metal sheath. For this purpose, the previous study analyzed the eddy current loss in single phase cable, but there is a limit to apply it because three phase cables are used in real environment. Therefore, in this paper, the eddy current loss occurring in the metal sheath of three phase cable according to the cause was analyzed theoretically. In addition, the eddy current loss occurring in the triangular and horizontal array were predicted through electromagnetic numerical analysis.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.1
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• pp.10-17
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• 1988

The torsional resonance of the generator shaft system has the possibility of inducing voltages across the stator winding because it is a carrier with the field excitation. And these torsional induced stator currents inducs the eddy current in the rotor. This paper describes the eddy current based on the double Fourier series method. The forces generating during the torsional interaction are computed using the Maxwell's magnetic stress tensor for each of the Fouriercomponennts. And then, these forces of the Fourier components are evaluated by the Parseval's theorem.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.28-36
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• 1996

The influence of vertical eddy viscosity to the nonlinear interaction of tidal current and wind-induced current is examined using a point model. A zero-equation turbulence model is derived by simplifying the q$^2$-q$^2$1 turbulence model under the assumption that the generation of turbulence kinetic energy is balanced with its dissipation and is further modified to include the depth of frictional influence properly The zero-equation turbulence model is derived and the possibility of resonance in the presence of Coriolis effect is suggested. The amplitudes of tidal currents remain the same regardless of the applied wind stress, but the over-tide component is generated due to the nonlinear interaction of tidal current and wind-induced current. Significant changes in the vertical profile of wind-induced currents can occur according to tide-induced background turbulence. The turbulence model can give rise to misleading results when applied to the wind-driven circulation in the tide-dominated sea such as Yellow Sea unless the tide-induced background turbulence is adequately included in the parameterization of vertical eddy viscosity.

• Korean Journal of Remote Sensing
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• v.15 no.2
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• pp.175-181
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• 1999

A recurring eddy which located at the terminal end of the Korean East Warm Current was captured on ocean color and sea surface temperature imagery from satellite in spring and autumn. During late April, 1997 thermal infrared imagery from the NOAA AVHRR sensor and ocean color data from the Japanese ADEOS-I OCTS sensor, revealed this feature. The cold core had elevated chlorophyll concentrations, based on OCTS estimates, of greater than 3 mg/m$^3$ while the warmer surrounding waters had chlorophyll concentrations of 1 mg/m$^3$ or less. The elevated cholophyll accociated with this eddy has not been previously described. The eddy is also evident in SST images from autumn, but the SST in the core is warmer than in spring, and the warm jet flowing to the west of the eddy is also warmer is autumn compared to spring. A reccurring eddy and the high chlorophyll_a concentration area which surround around the eddy show on NOAA and SeaWiFS images in March 2, 1998. The eddy forms at the northern extent of the Korean East Warm Current as those waters collide with the cold, south-flowing Liman Current over a topographic shelf about 1500 m deep. This region of the eddy formation appears to have a strong connection with the dynamics of the western part of the polar front eddy field that dominates surface mesoscale structure in the central East (Japan) Sea. Interaction of the eddy with ARGOW tracked drifters, and evidence for its persistence are discussed.

• International Journal of Aeronautical and Space Sciences
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• v.16 no.4
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• pp.560-570
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• 2015

We present a simulation of a hybrid Reynolds-averaged Navier Stokes / Large Eddy Simulation (RANS/LES) based on detached eddy simulation (DES) for a Burrows and Kurkov supersonic planar mixing experiment. The preliminary simulation results are checked in order to validate the numerical computing capability of the current code. Mesh refinement studies are performed to identify the minimum grid size required to accurately capture the flow physics. A detailed investigation of the turbulence/chemistry interaction is carried out for a nine species 19-step hydrogen-air reaction mechanism. In contrast to the instantaneous value, the simulated time-averaged result inside the reactive shear layer underpredicts the maximum rise in $H_2O$ concentration and total temperature relative to the experimental data. The reason for the discrepancy is described in detail. Combustion parameters such as OH mass fraction, flame index, scalar dissipation rate, and mixture fraction are analyzed in order to study the flame structure.