• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2983-2988
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• 2007

In the present study, the numerical investigation on the effects of water-mist characteristics has been carried out for the fire suppression mechanism. The FDS are used to simulate the interaction of fire plume and water mists, and program describes the fire-driven flows using LES turbulence model, the mixture fraction combustion model, the finite volume method of radiation transport for a non-scattering gray gas, and conjugate heat transfer between wall and gas flow. The numerical model is consisted of a rectangular enclosure of $L{\times}W{\times}H=1.5{\times}1.5{\times}2.0m$ and a water mist nozzle that be installed 1.8m from fire pool. In the study, the parameters of nozzle for simulation are the droplet size and the spray velocity. Finally, the droplet size influences to fire flume on fire suppression than spray velocity because of the effect of terminal velocity, and the optimal condition for fire suppression is that the droplet size and the spray velocity are $100{\mu}m$ and 20m/s, respectively.

• Water Engineering Research
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• v.3 no.2
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• pp.93-111
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• 2002

In this paper, mixing characteristics and dilution of the merging buoyant discharges from array of multiple jets has been extensively studied in the hydraulic model experiments. New equations for dilution, which include the merging effects correctly, were derived. Experiments were constructed in a 20-m long, 4.9-m wide and 0.6-m deep flume, and the model diffuser was manufactured to indicate the typical characteristics of the existing ocean wastewater outfall in South Korea. Buoyant discharge from the diffuser was reproduced using heated water. Water temperature was measured using CC-Type thermocouple sensors, which were connected to a 40-channel data logger. Experimental results show that merging between ports in a particular riser is dependent upon the discharge densimetric Froude number, whereas merging between two ports which are facing each other at 90$\circ$ at the adjacent risers is dependent upon the discharge densimetric Froude number and distance from the port and port spacing. Centerline dilution increase with distance from the port outlet until two plumes has merged. However, after merging occurs, increase of the centerline dilution almost stops. Further distance from the position where merging occurs, centerline dilution increases again.

• Journal of computational fluids engineering
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• v.20 no.2
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• pp.96-102
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• 2015

In this study, the green water phenomena on rectangular shaped structure is numerically simulated by STAR-CCM+ to investigate the flow pattern including the velocity profiles in bubbly water flow. 5 phases of the formation of green water in front of and over the rectangular shaped structure is simulated at the design condition which is scaled down by 1:125 from FPSO operating in GOM. All numerical results are compared with the experimental results performed in a two dimensional wave flume. The water deformation due to the green water are obtained by the high speed CCD camera with employing the shadow graphy technique, which is allowed to take the bubbly water flow into images. A series of image taken by shadow graphy technique is analyzed with MQD method to calculate the velocity in bubbly water flow.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.4
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• pp.52-61
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• 2003

This study was carried out to analyze the effects of stormwater retention and infiltration pond on reduction of flood peak and volume in a experimentally developed ecological pond. The experimental site has 542$m^2$ watershed area, 1,310mm yearly-averaged rainfall. And the area of the retention pond is 60$m^2$, the maximum water depth is 0.5m, the maximum and average storage is 15$m^3$and 9.3$m^3$d. And the area of infiltration pond is 58$m^2$, and the water depth varies 0.2m~0.5m. The monitoring system consists of one rainfall gage, one Parshall flume and acoustic water level gage, two rectangular weirs and acoustic water level gage for discharge gaging, and one data recording unit. Data from ten storm events in total, three storm events in year 2000 and seven storm events in year 2001, were collected. From the data the evaporation rate was achieved with the water balance equation, and the result shows 5.0mm/day in average. The result from the analysis of the effects on reduction of flood peak and volume, is that 14% reduction of flood volume and 15% reduction of flood peak in retention pond and 49% reduction of flood volume in infiltration pond.

• Journal of the Korean Geotechnical Society
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• v.36 no.11
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• pp.135-148
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• 2020

In this study, to investigate the effect of the array of cylindrical baffles on debris flow impact load, a series of small-scale tests were conducted according to varying row numbers of installed baffles in the flume. After the test, the behavior of debris flow interacting with baffles during the flow process was investigated. Based on the results, the influence varying velocity and flow depth on Froude number and dynamic pressure coefficient were analyzed. Test results showed that the greatest peak impact load occurred at the second row of baffle arrays. The dynamic pressure coefficient was also estimated by suggested equation and compared with previous studies.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.5
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• pp.651-659
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• 2018

A multi-level overtopping wave energy converter was designed according to the large tidal range and small wave heights in China. It consists of two reservoirs with sloping walls at different levels. The reservoirs share a common outflow duct and a low-head axial turbine. The experimental study was carried out in a laboratory wave-flume to investigate the overtopping performance of the device. The depth-gauges were used to measure the variation of the water level in the reservoirs. The data was processed to derive the time-averaged overtopping discharges. It was found that the lower reservoir can store wave waters at the low water level and break the waves which try to climb up to the upper reservoir. The upper sloping angle and the opening width of the lower reservoir both have significant effects on the overtopping discharges, which can provide more information to the design and optimization of this type of device.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.5
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• pp.572-582
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• 2018

In this paper, we have calculated a formular for sabot-trajectory of shipboard projectile including ship motion and generated trajectory-range function for analysing interference with structure of naval ship. We make formula to approximate the ship motion data of naval ship using optimization technique. Through this formula, we calculate the velocities and accelerations of sabot caused by ship motion(surge, sway, heave, roll, pitch, yaw) and then, we produce the formula about the trajectory of sabot including effects of ship motion in addition to previous study which had considered the effects of the pressure of flume, friction force, etc. To investigate interference with ship structures, we make the trajectory-range functions and then extract the nearest or farthest trajectory to ship structure. Through these data, we can conform whether the interference is happened or not.

• Journal of Ocean Engineering and Technology
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• v.32 no.2
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• pp.77-83
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• 2018

In this study, a series of experiments were performed to investigate the variations in the behavior of green water generation and the flow kinematics of bubbly flow on deck with various flare angles. The experiments were conducted in a 2-D wave flume using a simplified model of a BW Pioneer FPSO operating in the Gulf of Mexico, with a 100-year return period wave condition. The green water phenomena were captured with a high speed CCD camera. The variations in the behavior of the green water generation were investigated with various flare angles, and the horizontal mean velocity profiles of bubbly flow on deck obtained using bubble image velocimetry (BIV) were provided. The differences in flow kinematics of bubbly flow on deck were analyzed with various flare angles.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.5
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• pp.485-496
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• 2020

Submerged structures such as low-crested breakwaters and artificial reefs have been commonly used for coastal protection. In this study, two-dimensional laboratory experiments were conducted in a wave flume to investigate the wave transmission phenomena of permeable type submerged structures armored by Tetrapods. Different cases of the experimental conditions were included by relative crest depth, relative freeboard, relative crest width, wave steepness and so on. An empirical formula from the experimental data was proposed to predict the wave transmission coefficients over various specifications and structural designs of the permeable type submerged structure. The proposed formula successfully predicted the wave transmission coefficients. In this study, the proposed empirical formula of the wave transmission over the submerged structure was improved from the existing formula.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.5
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• pp.497-507
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• 2020

Two-dimensional laboratory experiments were conducted in a wave flume to investigate the wave transmission phenomena of rubble-mound type submerged structures armored with Tetrapods. Different experimental conditions were included by considering relative crest depth, relative freeboard, relative crest width, wave steepness, and so on. An empirical formula was proposed to predict the wave transmission coefficients over various specifications and structural designs of the partial perforated (rubble-mound) type submerged structure from the experimental results. The proposed formula successfully predicted the wave transmission coefficients. In this study, the proposed empirical formula of the wave transmission over the rubble-mound type submerged structure was improved from the existing formula.