• Journal of the Korean Society of Visualization
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• v.18 no.2
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• pp.35-38
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• 2020

Airfryer is used to heat a food up by convecting hot air upward around the food. In this study, we investigated the effect of the bottom-shape of the food container in airfryer on the upward convection velocity of hot air to find an optimal bottom-shape by computational fluid dynamics. Numerical experiments were performed by solving the incompressible Navier-Stokes equations with turbulence model. We found that the maximum upward velocity with concave flow-passage on the bottom was bigger than that with the flat bottom and that the maximum upward convection velocity was achieved when the number of concave flow-passage with fan-shape is around six. The pressure drop by the internal flow was found to increase as the number of the concave flow-passage on the bottom increased probably due to increase of the surface area of the bottom. Therefore, it can be said that the optimal number of the concave flow-passage is around six for the flow rate considered in this study.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.151-156
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• 2007

In December 2006, 2D surface streamer and Ocean Bottom Seismometer (OBS) data were acquired in the Ulleung basin in Korea where strong Bottom Simulating Reflectors (BSR) were shown as a result of 2D and 3D multichannel (MCS) reflection survey. The aim of this study is to provide another reliable source for estimating P wave velocity around BSR depth using OBS data in addition to velocity information from 2D surface seismic data. Four OBSs were deployed and four 20-km shot lines which pass two OBSs respectively were designed. To derive P wave velocity profile, interactive interval velocity analysis using ${\tau}$-p trajectory matching method (Kumar, 2005) was used for OBS data and semblance analysis was used for surface data. The seismic profiles cross the OBS instruments in two different directions yield recordings for four different azimuths. This raised the confidence for the results. All velocity profiles in the vicinity of BSR depth of four OBS sites show almost definite velocity changes which we could consider as upper BSR and free gas layer. Making comparison between velocity from OBS and that from 2D seismic semblance velocity analysis gives consistency in result.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.3
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• pp.58-71
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• 2022

Analytical solutions for two-dimensional velocities of regular waves generated by bottom wave makers in a flume were derived in this study. Triangular and rectangular bottom wave makers were adopted. The velocity potential was derived based on the linear wave theory with the bottom moving boundary condition, kinematic and dynamic free surface boundary conditions. Then, analytical solutions of two-dimensional particle velocities were derived from the velocity potential. The velocity potential and two-dimensional particle velocities which were derived as complex integral equations were numerically calculated. The solutions showed physically valid results as velocities of regular waves generated by bottom wave makers in a flume.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.46 no.4
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• pp.449-457
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• 2010

This study shows that the vertical migration speed of sound scattering layers (SSLs), which is distributed in near Funka Bay, were measured by 3D velocity components acquired from a bottom moorng ADCP. While the bottom mooring type has a problem to measure the velocity vectors of sound scattering layer distributed near to surface, both the continuous vertical migration patterns and variability of backscatterers were routinely investigated as well. In addition, the velocity vectors were compared with the vertical migration velocity estimated from echograms of Mean Volume Backscattering Strength, and estimated to produce observational bias due to SSLs which is composed of backscatterers such as euphausiids, nekton, and fishes have swimming ability.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.610-611
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• 2005

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1727-1734
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• 2008

After the final closure of sea dyke, seepage behaviour of embankment is highly changed by variation of water head different between tide wave and controlled water level at fresh lake. Especially, the seepage behaviour of bottom protection layer of final closure section is more important factor for structural and functional stability of sea dyke, because of the bottom protection layer of final closure section is penetrated sea side to fresh lake. Even though bottom protection layer was filled with dredged fine sand, it has a high permeability. In this paper, mainly described about the seepage velocity and borehole image of bottom protection layer filled with dredged sand after final closure. Various in-situ tests such as BIPS (Borehole Image Processing System) and ABI (Acoustic Borehole Imager) survey, wave velocity measuring, and color tracer survey were conducted to evaluate the seepage behavior of bottom protection layer. Based on the in-situ tests, the bottom protection layer of final closure section was almost filled with dredged sand which is slightly coarse grain sand and there have sea water flow by water head different between tide wave and controlled water level at fresh lake. Also, comply with tracer survey results, the sea water flow path was not exist or generated in the bottom protection layer. However, because of this result not only short term survey but also just one test borehole survey results, additional long term and other borehole tests are needed.

• Journal of Korean Society of Water and Wastewater
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• v.25 no.5
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• pp.627-634
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• 2011

In the present study, the flow behaviors of square jets surface discharged and submerged discharged into shallow water were each simulated using computational fluid dynamics, and the results were compared. As for the verification of the models, the results of the hydraulic experiment conducted by Sankar, et al. (2009) were used. According to the results of the verification, the present application of computational fluid dynamics to the flow analysis of square jets discharged into shallow water was valid. As for the wall jet, which is one form of submerged discharges, at the bottom wall boundary, the peak velocity of the jet rapidly moved from the center of the jet to the bottom wall boundary due to the restriction of jet entrainment and the no-slip condition of the bottom wall boundary, and, as for the surface discharge, because jet entrainment is limited on the free water surface, the peak velocity of the jet moved from the center of the jet to the free water surface. This is because jet entrainment is restricted at the bottom wall boundary and the surface so that the momentum of the central core of the jet is preserved for considerable time at the bottom wall boundary and the surface. In addition, due to the effect of the bottom wall boundary and the free water surface, the jet discharged into shallow water had a smaller velocity diminution rate near the discharge outlet than did the free jet; at a location where it was so distant from the discharge outlet that the vertical profile of the velocity was nearly equal (b/x =20~30), moreover, it had a far smaller velocity diminution rate than did the free jet due to the effect of the finite depth.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.66-71
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• 2000

This study was carried out to investigate the changes of tide velocity and sea bottom topology during the construction period of sea dike. The tide velocity and sea bottom depth were measured in Saemangeum area every year, and analyzed and compared to the initial data. The current and future changes of the tide velocity and direction according to the construction of Saemangeum sea dike were presented.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.596-603
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• 2020

In this paper, an experimental study was conducted to investigate the applications of bottom ash, which is an industrial by-product obtained from thermal power plants. Bottom ash was used as fine aggregate in this study, and an experiment was conducted to determine the characteristics of the bottom ash aggregate. In addition, 25, 50, 75, and 100% contents of crushed (natural) fine aggregate were replaced with bottom ash aggregate to produce concrete mixture including bottom ash. Thereafter, test results of the unit weight, ultrasonic velocity, compressive strength, and thermal conductivity of bottom ash concrete were obtained. Moreover, the effect of the curing ages of 28 and 91 days on the material characteristics of bottom ash concrete were identified. Test results showed that bottom ash used as fine aggregate had pozzolanic reaction. Finally, based on the extensive experimental results, relationships between thermal conductivity and unit weight, ultrasonic velocity, and compressive strength was suggested.

• Journal of the Korean Geosynthetics Society
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• v.5 no.1
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• pp.25-32
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• 2006

Sea dyke construction is simply defined as a cutting procedure of sea water flow. Sea dyke construction is more difficult than in-land construction because it is placed on deep seabed and exposed sea wave attack. Especially, the final closure of sea dyke is most dangerous due to the fast velocity of tidal flow. The final closure is consisted with vast rubble and heavy stone gabion, therefore the discharge velocity at land side of final close section is irregularly and sometime occur the fast discharge velocity. In this paper, the seepage model test performed to evaluate seepage behavior of final closure and continuous sea dyke section such as discharge velocity, hydraulic gradient, and phreatic line with installation of bottom protection filter mat. Based on the seepage model test results, the maximum discharge velocity of final closure section is 1.7m/sec and the discharge velocity is decreased maximum 23.7% with installation of bottom protection filter mat.