• Journal of applied mathematics & informatics
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• v.26 no.5_6
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• pp.911-923
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• 2008

The neural networks (NNs) simulation has been designed to simulate and predict the vortex wavelength ${\lambda}_x^*$, lateral vortex spacing ${\lambda}_y^*$, and normalized maximum vorticity at the vortex center near the wake of square cylinders with different corner radii. The system was trained on the available data of the three cases, although this data is very little. Therefore, we designed the system to work in automatic way for finding the best network that has the ability to have the best test and prediction. The proposed system shows an excellent agreement with that of an experimental data in these cases. The technique has been also designed to simulate the other distributions not presented in the training set and predicted them with effective matching.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.402-407
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• 1995

The effects of room temperature and strain aging treatment are discussed on the critical condition for the onset of growth of non-propagating cracks on 0.15% C low carbon steel, with special emphasis on the length of the critical non-propagating crack and on the crack opening displacement(COD) at the crack tip. It is found from the experimental analysis that room temperature and strain aging of a fatigue pre-cracked specimen introduced the closure of a crack tip of the pre-crack and the reduction of crack opening displacement at the wake of crack, together with an improvement in crack growth resistance of the microstructure. This may cause an increase in the endurance limit of the specimen, through the enhancement of effective stress for the onset of growth of the critical non-propagating crack.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.431-434
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• 2002

The excessive wind-induced motion of tall buildings most frequently result from vortex shedding induced across-wind oscillations. This form of excitation is most pronounced far relatively flexible, lightweight and lightly damped structure, e.g. tall building. This paper discusses aerodynamic means for mitigating the across-wind vortex shedding induced in such situations. Emphasis is on the change of the building cross section to design the building with openings from side to side which provide pressure equalization and tend to reduced the effectiveness of across-wind forces by reducing their magnitudes and disrupting their spatial correlation. Wind tunnel test have been carried out on the Kumoh National University of Technology using rigid models with twenty-four kinds of opening shapes. Form these results, the effective opening shape, size and location for building to reducing wind-induced vortex shedding and responses are pointed out.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.3
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• pp.231-238
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• 2014

In this study, the self-propulsion tests are performed in INHA towing tank. And the effective wake characteristics of the KVLCC2 and the KCS models are compared by the experimental results. The form factor is independent of Reynolds number. To estimate the hydrodynamic performance of a full scale ship, the form factor is determined to consider attendant on Reynolds number. In this research, the power predictions are carried out considering the form factor difference of model and full scale ship. The results of this research could be used as one of the fundamental data to the powering performance prediction.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.185-188
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• 2008

In this study, we experimentally investigated that the optimization of pulsating jet to reduce the separated flow region behind the vertical fence. The vertical fence was submerged in the turbulent boundary layer in the circulating water channel and we applied phase averaged PIV method to measure the instantaneous velocity fields around the fence. One cycle of pulsating jet is divided into 20 phases and grabbed total 200 instantaneous velocity fields at each phase. The experiments were performed by varying the frequency, maximum jet velocity and the shape of pulsating jet wave. Pulsating jet was precisely made by piston-type pump controlled by the computer. The obtained results were compared with normal fence flow. From this study, we found there is the specific frequency which is effective in reducing the reattachment region.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.508-513
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• 2000

An experimental investigation has been carried out for two circular cylinders having different groove configurations(U and V-shape). The results were compared with those for the smooth circular cylinder. The drag force, mean velocity and turbulent intensity profiles of wake behind the cylinders were measured with varying the Reynolds number $Re=8000{\sim}14,000$ based on the cylinder diameter. As a results, the U-groove circular cylinder was found to be most effective riblet shape with reducing the drag up to 21%. As the Reynolds number increases, the vortex shedding frequency of the grooved cylinders becomes a little larger, compared to the smooth cylinder. The flow visualization using the smoke-wire technique was also carried out to see the flow structure qualitatively.

• The KSFM Journal of Fluid Machinery
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• v.8 no.6 s.33
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• pp.47-54
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• 2005

An oscillating foil can produce a driving force through the generation of a reversed $K\'{a}rm\'{a}n$ vortex street, and it can be expected to be a new highly effective propulsion system. A simple pitching foil model was made and it was operated within a water channel. The wake formation behind a pitching foil was visualized and unsteady fluid forces were measured using a 6-axis force sensor based on force and moment detectors. We have been examined various conditions such as reduced frequency, amplitude and pivot point in NACA 0010. The results showed that thrust coefficients increased with a reduced frequency. We also presented the experimental results on the characteristics of a pitching foil at various parameters.

• Journal of Physiology & Pathology in Korean Medicine
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• v.19 no.6
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• pp.1715-1719
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• 2005

Delirium is a set of symptoms that includes Disturbance of consciousness, attention, cognition, sleep-wake cycle. It usually appears as a disease progresses. Also it can be considered as one of byun-jo(煩躁)'s symptoms because it shows similar symptom and progress to byun-jo(煩躁). One patient was admitted who was suffering delirium, restlessness, chest discomfort, disorientation. The patient was diagnosed as delirium and byun-jo that was caused by heat in the heart and stomach, and was treated with Chungul-san(淸鬱散). In the course of treatment, symptoms improved gradually. Resu suggest that Chungul-san(淸鬱散) is effective on delirium, byun-jo caused by heat in stomach.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.04a
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• pp.365-372
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• 2001

This study is concerned with the application of an analytical model of cyclic crack growth that includes the effects of crack closure. The crack closure model is based on the Dugdale model and the strip model, considering the plasticity-induced closure which is caused by residual plastic deformation remaining in the wake of an advancing crack. This study is performed to get the relation between crack growth and crack opening stress with the constant stress ratio, and the relation between stress ratio and crack opening stress with the constant maximum stress under constant-amplitude loading. Under constant-amplitude loading, the crack opening stress is conversed the constant value as a crack grows and is proportion to both the stress ratio and the maximum stress. The crack closure effect, however, is decreased in the positive stress ratio and disappeared at about 0.7. The crack growth analysis using the crack closure model shows that the influence of stress ratio is minimized in the relation between crack growth ratio and effective stress intensity range specially at the negative stress ratio.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.27-30
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• 2002

An experimental study is performed to investigate the characteristics of near wake behind a circular cylinder with serrated fins using the constant temperature anemometer and through flow visualization. Previous report(Boo at al., 2001) shows that there are three different modes in vortex shedding behavior. This paper is focused on the identification of the physical reasons why the difference is occured in vortex shedding. The through flow velocity crossing fins decreases as increasing fin height and decreasing fin pitch mainly due to the flow resistence. Vortex shedding is affected strongly by velocity distribution around fin tube, especially by the velocity gradient. The velocity distribution at X/d=0.0 has lower gradient with increasing freestream velocity and fin height and decreasing fin pitch. Those differences in velocity gradients generate different vortex shedding mechanism.