• Journal of the Korean Society of Visualization
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• v.7 no.1
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• pp.14-20
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• 2009

In comparison with previous researches fur swirling flow, the spiral flow self-generated in the spiral flow nozzle has some different characteristics. It is not needed a compulsive tangential momentum to get its velocity component and has long potential core, relatively low swirl ratio, and high focusing ability. In this study, the self-generated mechanism of the spiral flow was clarified and the effect on the width of annular slit on spiral flow characteristics was investigated experimentally and numerically. As a result, the existence of tangential velocity component regardless of a compulsive angular momentum is clarified and the results obtained by experiment have a satisfactory agreement with those by numerical method, quantitatively and qualitatively.

• Journal of the Korean Society of Visualization
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• v.13 no.1
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• pp.21-25
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• 2015

Three-dimensional vortex structures in the corner region of translating normal plates are visualized experimentally with defocusing digital particle image velocimetry. Vortex formation processes for three plates with corner angle $60^{\circ}$, $90^{\circ}$, and $120^{\circ}$ are compared in order to study the effect of corner shape on vortex formation. In all cases, the self-induction of the starting vortex and its interaction with the potential flow induced by the moving plate cause the vortex to change its form dynamically after the plate starts to translate. While the vortex near a corner follows the plate in the low corner angle of $60^{\circ}$, the vortex separates early from the plate and its forward motion becomes slow in the high corner angle of $120^{\circ}$. It is also found that the starting vortex can transport inward at the corner, which depends on the corner angle.

• Journal of the Korean Society of Visualization
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• v.10 no.1
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• pp.9-14
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• 2012

In this study, a piezoelectric inkjet nozzle with a rectangular shaped channel has been developed, and the characteristics of droplet formation have been investigated according to the variation of pulse widths in bipolar waveform. The channel of the nozzle was fabricated transparently by a precision machining technique. A tantalum membrane which was attached to a piezoelectric material covers the channel. By applying two types of bipolar waveforms to the piezoelectric actuators, droplet formation through the nozzle was monitored by a CCD camera. For the variety of the first and second pulse widths in the bipolar waveforms, the regimes of single and double droplet formations are presented. The change of droplet velocity which depends on the pulse width and the type of waveform is also discussed.

• Journal of the Korean Society of Visualization
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• v.13 no.2
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• pp.28-32
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• 2015

Blood flow simulations in an realistic carotid bifurcation model with considering wall compliance were carried out to investigate the effect of wall elasticity on the wall shear stress and wall solid stress. Canonical waveforms of flow rates and pressure in carotid arteries were imposed for boundary conditions. Compared to a rigid wall model, we found an increased recirculation region at the carotid bulb and an overall reduction of wall shear stress in a compliant model. Additionally, there was appreciable change of flow rate and pressure wave in longitudinal direction. Both solid and wall shear stress concentration occur at the bifurcation apex.

• Journal of the Korean Society of Visualization
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• v.5 no.2
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• pp.9-13
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• 2007

Typhoon simulation based on dynamical forecasting results is demonstrated by utilizing geodesic model GME (operational global numerical weather prediction model of German Weather Service). It is based on uniform icosahedral-hexagonal grid. The GME gridpoint approach avoids the disadvantages of spectral technique as well as the pole problem in latitude-longitude grids and provides a data structure extremely well suited to high efficiency on distributed memory parallel computers. In this study we made an attempt to simulate typhoon 'NARI' that passed over the Korean Peninsula in 2007. GME has attributes of numerical weather prediction model and its high resolution can provide details on fine scale. High resolution of GME can play key role in the study of severe weather phenomenon such as typhoons. Simulation of future typhoon that is assumed to occur under the global warming situation shows that the life time of that typhoon will last for a longer time and the intensity will be extremely stronger.

• Journal of Welding and Joining
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• v.20 no.5
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• pp.113-119
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• 2002

To prevent problems caused by welding deformation, preparation in the design stage is necessary. Countermeasures in the design stage is also the most cost-effective method. In this study, to give designers information on the welding deformation, a system to visualize the welding deformation is developed. The model to visualize the deformation is the stiffened plate common in steel structures. To increase computational efficiency, theoretical solutions to calculate the deformation of plate and stiffener are used instead of numerical analysis. Also, to secure accuracy, experiments to estimate bending moment causing welding deformations are performed. A computer program written with Visual C++ is developed for interactive data input, calculation of welding deformation and display of deformed shape. Designers can change the design in the early stage after checking the deformed shape by this system.

• Journal of Korea Multimedia Society
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• v.7 no.5
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• pp.755-765
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• 2004

Recently, the Internet-based distributed/parallel computing using many of idle hosts has been demonstrated its usefulness for processings of a large-scale task and involving several important issues. While executing a large-scale task, the realtime monitoring is required for adaptive strategy of the performance and state change of host. This paper provides the realtime monitoring and visualization on global computing infrastructure called PDP(Parallel Distributed Processing) which is a parallel computing framework implemented with Jana for parallel computing on the Internet.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1088-1091
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• 2015

프로젝트 수행에 우리는 괸리를 목적으로 다양한 산출물을 작성하고 생성한다. 미국 PMI의 PMBOK은 다양한 산출물을 표준화하고 있고 ISO21500 역시 다양한 종류의 산출물 생성을 표준화하고 있다. 그러나 산출물의 상세한 내용에 대해서는 PMBOK이나 ISO21500에서도 규정하지 않고 있다. 프로젝트 관리 산출물은 프로젝트 성공을 위한 산출물로 각종 관리계획, 중요 마일스톤 일정, 각종 이슈, 변경, 위기관련 다양한 지표 등을 중심으로 구성되어야 한다. 본 연구는 프로젝트 관리 산출물들에 프로젝트를 기준정보 6가지(Requirement, Work, Activity, Change, Issue, Risk)가 프로젝트 관리 산출물에 표기되어 추적기능을 가지고 있고 가시화를 할 수 있는지에 대하여 프로젝트 관리 산출물 template를 가지고 분석하였다. 이러한 분석 결과를 바탕으로 프로젝트 관리 산출물에 기준 정보를 추가하여 프로젝트 기준정보를 통합하고 가시화 하여 정보의 추적기능이 강화되기를 기대한다.

• Journal of the Korean Society of Visualization
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• v.17 no.2
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• pp.39-47
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• 2019

Impingement cooling utilizing synthetic jets is emerging as a popular cooling technique because of its high local cooling efficiency. The interaction between the vortex structure of the synthetic jet and the surface is crucial in understanding the mechanism of this technique. In this study, the impinging vortex structure and its advection are investigated by experiments with jet-to-surface spacing $2{\leq}H/D{\leq}7$, and synthetic jet Reynolds number $5120{\leq}Re{\leq}9050$. Using phase-locked particle image velocimetry, ensemble averaged (phase averaged) flow fields are obtained, and vortex identification and quantification techniques are applied. The shape, trajectory, and intensity change of the vortex are assessed. A sharp decline in the vortex intensity and the occurrence of a counter-rotating vortex at the impingement point are observed.

• Journal of the Korean Society of Visualization
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• v.19 no.2
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• pp.63-73
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• 2021

It is essential to accurately predict the change in water level, velocity, and flow rate for each passage of the grit chamber according to the operating conditions of the pump. In this study, VOF multiphase flow analysis was performed, and the flow characteristics of the grit chamber were predicted. As a result of simulations, the sedimentation phenomenon after the entrance of the grit chamber channel is expected to occur on the side walls. When 6 channels are used, the average speed of the channels is about 52% of the design standard, and when 4 channels are used, the value increases to 74% of the design standard. The average water level in the channels tends to decrease as the flow velocity increases, and the water level in the absorption well with a larger flow rate is maintained lower than that in the absorption well with a smaller flow rate.