• Journal of ILASS-Korea
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• v.28 no.1
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• pp.32-42
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• 2023

In this study, spray characteristics of n-heptane and propane were investigated under different injection pressure using various imaging techniques such as Mie-scattering, DBI (diffuse back-illumination), and Schlieren imaging techniques. NI compact RIO system was used to control a test injector. Spray penetration length, length-to-width ratio and number of black pixels were calculated by using MATLAB software to compare spray characteristics of each fuel. Longer spray penetration length and higher length-to-width ratio were observed in propane spray because of flash boiling caused by high saturated vapor pressure. Spray collapse occurred in propane spray due to the high plume-to-plume interaction. Moreover, rapid evaporation occurred in propane spray, so that nozzle tip wetting could not be observed. Rapid evaporation of propane also caused fewer residual droplets compared to n-heptane spray. Therefore, propane is advantageous in reducing the generation of soot emission from large droplets that are not atomized. However, additional evaluation should be conducted considering combustion efficiency and the possibility of deposits by nozzle tip icing during fuel injection.

• Journal of the Korean Society of Visualization
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• v.21 no.1
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• pp.18-25
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• 2023

In these days, high dimensional data prediction technology based on neural network shows compelling results in many different kind of field including engineering. Especially, a lot of variants of convolution neural network are widely utilized to develop pixel level prediction model for high dimensional data such as picture, or physical field value from the sensors. In this study, velocity vector field of ideal flow on ship surface is estimated on pixel level by Unet. First, potential flow analysis was conducted for the set of hull form data which are generated by hull form transformation method. Thereafter, four different neural network with a U-shape structure were conFig.d to train velocity vectors at the node position of pre-processed hull form data. As a result, for the test hull forms, it was confirmed that the network with short skip-connection gives the most accurate prediction results of streamlines and velocity magnitude. And the results also have a good agreement with potential flow analysis results. However, in some cases which don't have nothing in common with training data in terms of speed or shape, the network has relatively high error at the region of large curvature.

• Journal of the Korean Society of Visualization
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• v.22 no.1
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• pp.49-60
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• 2024

The purpose of this study establishes the deep neural network (DNN) and Decoder models to predict the flow and thermal fields of three-dimensional wavy wings as a passive flow control. The wide ranges of the wavy geometric parameters of wave amplitude and wave number are considered for the various the angles of attack and the aspect ratios of a wing. The huge dataset for training and test of the deep learning models are generated using computational fluid dynamics (CFD). The DNN and Decoder models exhibit quantitatively accurate predictions for aerodynamic coefficients and Nusselt numbers, also qualitative pressure, limiting streamlines, and Nusselt number distributions on the surface. Particularly, Decoder model regenerates the important flow features of tiny vortices in the valleys, which makes a delay of the stall. Also, the spiral vortical formation is realized by the Decoder model, which enhances the lift.

• Korean Journal of Construction Engineering and Management
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• v.25 no.2
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• pp.69-80
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• 2024

Currently rebar spacing inspection is carried out by human inspectors who heavily rely on their individual experience, lacking a guarantee of objectivity and accuracy in the inspection process. In addition, if incorrectly placed rebars are identified, the inspector need to correct them. Recently, laser scanning and AR technologies have been widely used because of their merits of measurement accuracy and visualization. This study proposes a technology for rebar spacing inspection and fixing by combining laser scanning and AR technology. First, scan data acquisition of rebar layers is performed and the raw scan data is processed. Second, AR-based visualization and fixing are performed by comparing the design model with the model generated from the scan data. To verify the developed technique, performance comparison test is conducted by comparing with existing drawing-based method in terms of inspection time, error detection rate, cognitive load, and situational awareness ability. It is found from the result of the experiment that the AR-based rebar inspection and fixing technology is faster than the drawing-based method, but there was no significant difference between the two groups in error identification rate, cognitive load, and situational awareness ability. Based on the experimental results, the proposed AR-based rebar spacing inspection and fixing technology is expected to be highly useful throughout the construction industry.

• Journal of the Korean Society of Visualization
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• v.22 no.2
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• pp.55-62
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• 2024

Using an internal flow noise test bench, this study investigates the variation in internal flow noise at the inlet and outlet monitoring points of a DN100 T-junction pipe under different flow velocities. Results indicate that with increasing flow velocity, both the sound pressure level and total sound pressure level at the inlet and outlet monitoring points increase. The highest total sound pressure level is observed at the vertical outlet monitoring point B, followed by the horizontal inlet monitoring point A, with the lowest at the horizontal outlet monitoring point C. At a constant flow velocity, the sound pressure level at the inlet and outlet points initially increases and then decreases as frequency increases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1115-1119
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• 2005

The paper proposes the elastic modulus evaluation technique of a cantilever beam by vibration analysis based on time-average electronic speckle pattern interferometry (TA-ESPI) with non-contact and nondestructive and Euler-Bernoulli equation. General approaches for the measurement of elastic modulus of thin film are Nano indentation test, Bulge test and Micro-tensile test and so on. They each have strength and weakness in the preparation of test specimen and the analysis of experimental result. ESPI has been developed as a common measurement method for vibration mode visualization and surface displacement. Whole-field vibration mode shape (surface displacement distribution) at a resonance frequency can be visualized by ESPI. And the maximum surface displacement distribution from ESPI is a clue to find the resonance frequency at each vibration mode shape. And the elastic modules of test material can be easily estimated from the measured resonance frequency and Euler-Bernoulli equation. The TA-ESPI vibration analysis technique is able to give the elastic modulus of materials through the simple processing of preparation and analysis.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.46-51
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• 2007

The irregular fuel surface was observed by the visualization of hybrid rocket combustion. Even though the test condition maintained oxidizer rich environment, the irregular dark fuel surface was formed as the result of incomplete combustion. In order to investigate the correlation of the characteristics of oxidizer flow and the irregular fuel surface, various flow conditions were imposed such as swirl flow, induced swirl flow by helical fuel configuration and straight flow. Test results revealed no correlation was found between oxidizer flow condition and irregular fuel surface. And this can be a commonly observed phenomena in the tests with different fuel/oxidizer combination. Thus, the irregular fuel surface can be a result of the interaction of blowing flow of vaporized fuel and the boundary layer of oxidizer flow. A further study will be required to confirm the assumption for the formation of irregular fuel surface.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.1
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• pp.25-32
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• 2015

Dielectric barrier discharge (DBD) plasma actuator was designed to reduce aerodynamic drag in a cylindrical model and wind tunnel test was performed at various wind velocities. In addition, computational fluid dynamics (CFD) analysis and flow visualization were used to investigate the effect of the plasma on the flow stream in the cylinderical model. At low wind velocity, the plasma actuator had no effects because flow separation did not appear. The aerodynamic drag was reduced by 14% at 14 m/s and by 27% at 17 m/s, respectively. It was confirmed by CFD analysis and flow visualization that the DBD plasma actuator decreased in pressure difference around the cylindrical model, thus decreasing the magnitude of wake vortex.

• Journal of The Korean Association For Science Education
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• v.26 no.3
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• pp.367-375
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• 2006

This study investigated the effects of varying visuals in drawing and writing as methods to assist students in connecting and integrating multiple external representations provided in learning the particulate nature of matter. Seventh graders (N=233) at a coed middle school were assigned to control, static drawing (SO), dynamic drawing (DD), static writing (SW), and dynamic writing (DW) groups. The students were taught about "Boyle's Law" and "Charles's Law" for two class periods. Two-way ANCOVA results revealed that the scores of a conception test for the two drawing (SD, DD) groups and the two writing (SW, DW) groups were significantly higher than those for the control group. Within the writing groups, students of lower spatial visualization ability in the DW group scored significantly higher than those in the SW group. However, no significant differences were found in the scores of the conception test for the two drawing (SD, DD) groups regardless of students' visualization ability. Researchers also found that most students in both DD and DW groups had respectively positive perceptions of dynamic visuals in drawing or writing.

• Fire Science and Engineering
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• v.13 no.4
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• pp.30-37
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• 1999

In this study, reduced-scale experiments as the alternative to a real-scale fire test were conducted to understand fire properties in atrium space. The scaling laws were derived from $\pi$-parameters which were deduced by dimensional analysis of governing equations (continuity, conservation of momentum and conservation energy). The 1/50 scale experiment simulated the real-scale fire test in SIVANS atrium at Japan were conducted under the scaling laws. And this results were compared with real-scale experiment results. Furthermore these results were visualized by video recording system using laser light sheet.