• Journal of Wetlands Research
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• v.15 no.1
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• pp.51-58
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• 2013

In this study, the hydraulic experiments were conducted for the dredging efficiency of the cutter head type, which includes the open type and the close type cutter head. The dredging experimental instrument was installed in the large water tank which has the dimension of $4.9m(L){\times}2.2m(W){\times}1.5m(H)$. The dredging experiments were performed for the various conditions of dredging depth, rotating speed, and suction speed of the cutter head. As the results, the dredging efficiency of the close-type cutter head is much higher than that of the open-type cutter head. The dredging efficiency of the same cutter head type was mainly influenced by the rotating speed of cutter head. Also the adequate suction speed of the cutter head is needed for more effective dredging.

• Journal of Aquaculture
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• v.17 no.4
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• pp.240-245
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• 2004

Two experiments were conducted to study the effect of temperature on growth and survival of yearling sea bass, Lateolabrax japonicus reared from 3$^{\circ}C$ to 33$^{\circ}C$. In the I st experiment, we used yearlings fish averaging 19.2$\pm$0.2 cm/fish (Mean$\pm$S.E.M.) of total length (TL) and 67.0$\pm$1.8 g/fish (Mean$\pm$S.E.M.) of body weight (BW), and we cultured the fish at 3, 6, 9, 12 and 17$^{\circ}C$ for 90 days. In the 2nd experiment, the experimental fish averaging 24.9$\pm$0.1 cm/fish (Mean$\pm$S.E.M) of TL and I 46.4$\pm$3.0 g/fish (Mean$\pm$S.E.M) of BW were reared at 21,24,27,30 and 33$^{\circ}C$ for 90 days. During these experiments, we measured food intake, feed efficiency, survival and growth (TL and BW) in the both experiments. Although food intake of the yearling increased with the temperature, the feed efficiency was only enhanced within the temperature range, from 21 to 27$^{\circ}C$. Growth of yearling was normal within the temperature range from 17 to 3$0^{\circ}C$, but it was stoped or reduced in other temperatures. Survival rate was significantly reduced in 3$^{\circ}C$ from the 1st experiment and in 30 and 33$^{\circ}C$ from the 2nd experiment, but there was no significant difference among other groups.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.12
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• pp.1305-1310
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• 2005

As a way to the optimum design of the collector well lateral in riverbed filtration, experiments were performed using sand tanks which were connected to form a model lateral system. Measured were the residual hydraulic heads along the laterals, the discharge rates at each sand tank and the production rates at the collector well while the model laterals were operated with various scenarios of changing parameters including water level of the collector well, the lateral diameter and length, and the hydraulic conductivity of the sand. Results showed that riverbed filtration could be more efficient when the resistance in the lateral was weak compared with the resistance in the sand, which was indicated by the more flattened distribution of the residual hydraulic heads along the lateral. Results also showed that the discharge rate increased exponentially with the approach to the collector well, and that the exponent increased as the lateral diameter decreased and/or the hydraulic conductivity of the sand increased. It was also seen that the well production increased with the increase in the lateral length and diameter although the marginal productivity decreased. It could be concluded that the axial flow velocity in the lateral was an important factor governing the efficiency of a lateral in riverbed filtration and that the maximum entrance velocity to the collector well, over which the efficiency decreased drastically, was about 1 m/sec under the conditions of this study.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.385-392
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• 2017

This research presents the results of a study on the trajectory characteristics of barges with different configurations. A towing experiment was carried out in a water tank with three types of barges in two cases: with and without skegs. The effects of towline length on trajectory were also observed. This study analyzed and compared the length and amplitude of trajectory shapes for each barge in various combinations. It revealed that the trajectory of a barge is influenced not only by skegs but also by the length of the towline. As a result of this work, it can be clearly seen that skegs significantly improve the course stability of a towed barge regardless of differences in bow shape or towline length. Water tank test results also indicated that the length of a towline plays a key role in affecting the trajectory characteristics of a barge-towing system. The length and amplitude of the slewing motion of a barge increased with an increase in the length of the towline connected to the barge. Validation of the present research results should be carried out by further experiments and computational comparisons in the near future.

• Journal of the Korean earth science society
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• v.33 no.6
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• pp.544-553
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• 2012

A simple experimental method was developed to help students understand the effect of the Coriolis force on typhoon genesis and movement. It consists of rotating tanks with and without a sloping bottom, and a small stirrer to produce cyclonic typhoon-like vortices by locally stirring the water. Vortices were able to last for more than 3 minutes without dissipation in the rotating tank. However, vortices were hardly maintained without rotation, and would rather disappear as soon as the stirrer stopped mixing. Since the dynamical properties of the rotating water are similar to those of the atmosphere influenced by the Coriolis force, the experiments show that the Coriolis force is indispensable to the typhoon genesis. When the tank had both the sloping bottom and rotation, vortices would move in a particular direction. Considering the topographical beta effect, this result indicates that typhoons are drifted not only by the steering wind but also by the meridional gradient of the Coriolis force. The methodology developed in this study, would be useful for both students and teachers to better the relationship between the Coriolis force and the typhoon genesis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.3
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• pp.289-295
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• 2004

The heat transfer coefficient and pressure drop during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments were conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flowmeter, an evaporator, and a gas cooler(test section). The main components of the water loop consist of a variable-speed pump, an isothermal tank, and a flowmeter. The gas cooler is a counterflow heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The test section consists of smooth, horizontal stainless steel tube of the outer diameter of 9.53mm and of the inner diameter of 7.75mm. The length of the test section is 6m. The refrigerant mass fluxes were 200∼300kg/(m2$.$s) and the inlet pressure of the gas cooler varied from 7.5㎫ to 8.5㎫. The main results were summarized as follows : Pressure drop of CO2 increases with increasing gas cooler pressure. The friction factors of CO2 in a horizontal tube show a relatively good agreement with the correlation by Blasius. The heat transfer coefficient of CO2 in transcritical region increases with decreasing gas cooler pressure and decreasing mass flux of CO2. Most of correlations proposed in a transcritical region showed significant deviations with experimental data except for those predicted by Gnielinski.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.4
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• pp.3-13
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• 1989

In recent towing tank experiments, it has been observed that a ship moving near the critical speed $\sqrt{gh}$(g=gravitational acceleration, h=water depth) radiates solitons upstream in an almost periodic manner. As a ,consequence, the ship experiences considerable changes in resistance, trim and sinkage, or better known as squat. Mei and Choi(1987) developed a nonlinear theory for a slender ship by using the method of matched asymptotic expansions. For a certain class of channel width and ship slenderness, they found that the waves generated can be described by an inhomogeneous Korteweg-de Vries(KdV) equation. The leading-order solution properly predicts solitons propagating upstream, but it fails to render three-dimensional waves in the wake. In this paper a new approach has been made by choosing a different class of channel width and ship slenderness. The wave equation in the farfield turns out to be a homogeneous Kadomtsev-Petviashvili(KP) equation, which predicts solitons upstream and three-dimensional waves in the wake. Numerical results for the wave resistance, sinkage and trim reflect the experimentally identified phenomena.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.41 no.4
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• pp.43-51
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• 2009

Paper mill sludges are discharged around 870,000 M/T annually. Only 30% of the paper mill sludge have been recycled and the rest has been disposed by land fill, incineration, ocean abandonment and other ways. Because of overall prohibition of sludge disposal by London Dumping Convention in 2012, a urgent counter measure for paper mill sludge must be provided. In this paper, some basic experiments were carried out to develop a tray cell pot using paper mill sludge for increasing the recycling potential of the wasted sludge. To establish the manufacturing parameters, the tray cell pots were made with three types of materials including virgin pulp, old news paper and corrugated board mixed in a blend tank of a molding machine. The bending force and moisture content of the produced tray cell pots was measured to confirm the application capability. The tray cell pot could be manufactured under the condition of over 20% of virgin pulp, 40% of old news paper added. However, the corrugated board could not be used because of the glutinous substance included. The produced tray cell pot absorbed water very easily and the bending force decreased rapidly. The waterproof material must be used to applicate the produced tray cell pot in plant growing fields.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.500-508
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• 2004

The heat transfer coefficients during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments are conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater, and a gas cooler(test section). The water loop consists of a variable-speed pump, an isothermal tank, and a flow meter. The gas cooler is a counterflow heat exchanger by cooled water flowing in the annulus. The $CO_2$ flows in the horizontal stainless steel tube. which is 9.53mm in O.D. and 7.75mm in I.D. The gas cooler is 6 [m] in length. which is divided into 12 subsections, respectively. The experimental conditions considered in the study are following range of variables : refrigerant temperature is between 20 and $100^{\circ}C$. mass fluxes ranged from 200 to 400kg/($m^2$.s), average pressure varied from 7.5 to 10.0MPa. The main results were summarized as follows : The friction factors of $CO_2$ in the gas cooler show a relatively good agreement with those predicted by Blasius' correlation. The local heat transfer coefficient in the gas cooler has compared with most of correlations, which are the famous ones for forced convection heat transfer of turbulent flow. The results show that the local heat transfer coefficient of gas cooler agrees well with the correlation by Bringer-Smith except that at the region near pseudo critical temperature. while that at the near pseudo critical temperature is higher than the correlation.

• The Journal of the Acoustical Society of Korea
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• v.23 no.5
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• pp.362-369
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• 2004

The High-frequency (30 ∼ 120 ㎑) bottom reflection loss at rough water-sediment interface is affected by the gram size distribution of the sediments. The roughness of the bottom surface is represented by "acoustical roughness. g/sub R/" The grain size of sandy sediments is g/sub R/∼O(1) and the dependence as a function of frequency. We suggest the modified bottom reflection loss model (HYBRL model , HanYang university Bottom Reflection Loss model) that include in the deviation of the reflection loss as a function of the grain size distribution and frequency dependence. And bottom reflection loss model of frequency dependence and deviation of bottom properties is verified by water tank and field experiments.