• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.295-304
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• 2001

The hydrodynamic impact problem was studied from 1929 to recent. Especially, Impact pressure is important for the design of the ships and offshore structure and spacecrafts, and under weapons. A ship traveling at high speed or in heavy sea has its bow and bottom damaged by high pressure caused by impact with and detachment from the water surface. Considerable impact may also occur when large waves hit the cross member or deck plate of an offshore structure within the splash zone. Many engineering cases require consideration of impact pressure, the movement of objects and change of the flow field. This study was obtained the pressure distribution of a falling body that is deadrise angle $0^{\circ}$ and deadrise angle $5^{\circ}$ upon a water surface by the experiment with the impact machine. The theoretical equation was obtained the air region and the interface and the water region which devide 3 parties between the body and the water surface for an investigation of the complete phenomena. Pressure distributions and histories compare favorably with available experimental data. The numerical results are similar to the experimental results for the impact force type with Fo(1+$cos{\pi}t/tc$).

• Geomechanics and Engineering
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• v.14 no.5
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• pp.407-419
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• 2018

In order to investigate flow characteristics after water inrush from the working face in process of karst tunnel construction, numerical calculation for two class case studies of water inrush is carried out by using the FLUENT software on the background of Qiyueshan tunnel. For each class water inrush from the tunnel face, five cases under different water-inrush velocity are simulated and researched. Three probing lines are selected respectively in the left tunnel, cross passage, right tunnel and in the height direction of the tunnel centerline. The variation characteristics of velocity and pressure on each probing line under the five water-inrush velocities are analyzed. As for the selected four groups probing lines in the tunnels, the change rules of velocity and pressure on each group probing lines under the same water-inrush velocity are discussed. Finally, the water flow characteristics after inrush from the tunnel face are summarized by comparing the case studies. The results indicate that: (1) The velocity and pressure change greatly at the intersection area of the cross passage and the tunnels. (2) The velocity nearby the tunnel side wall is the minimum, while it is the maximum in the middle position. (3) The pressure value of every cross section in the tunnels is basically fixed. (4) As water-inrush velocity increases, the flow velocity and pressure in the tunnels also increase. The former is approximately proportional to their respective water-inrush velocity, while the latter is not. The research results provide a theoretical basis for making scientific and rational escape routes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3287-3295
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• 2009

This present study implemented a rainfall simulation system, and performed simulation and numerical analysis according to rainfall and slope conditions using a model slope built with weathered granite soil. Extensive analysis were conducted on the characteristics of changes in volumetric water content and pore water pressure measured in the simulation, and compared them with the results of numerical analysis. It took longer for the volumetric water content to reach the limit when rainfall intensity was high and the slope was steep and shorter when rainfall intensity was low and the slope was gentle. When rainfall intensity was low and the duration of rainfall was short, negative pore water pressure was higher and the time for restoration was shorter. On the contrary, when rainfall intensity was high and the duration of rainfall was long, it took a longer time to restore negative pore water pressure. In the results of rainfall simulation and numerical analysis, the distribution of volumetric water content and pore water pressure was similar between the two. However, the volumetric water content was different by up to 5%, and pore water pressure by up to 3kPa.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.4
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• pp.343-351
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• 2019

Green water impact may sometimes cause some structure damages on ship's bow deck. Prediction of proper design pressure against the green water impact is an essential task to prevent the possible damages on bow deck. This paper presents a computational method of the bow deck's design pressure against the green water impact. Large heave and pitch motions of ship are calculated by the time domain nonlinear strip method. Green water flow and pressure on bow deck are simulated by the predictor-corrector second kind upstream finite difference method. This green water simulation method is based on the shallow water wave equations expanded for moving bottom conditions. For various kind of ships such as container ship, VLCC, oil tanker and bulk carrier, the green water design pressures on bow deck are computed and discussed. Also, the obtained results of design pressure on bow deck are compared with those of the classification society rules and discussed.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.1-11
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• 2014

The water distribution system should be invariably operated on continuous pattern for 24 hours a day. Occasionally, it is not practically possible to operate for 24 hours due to water shortage or financial constraints. Therefore an intermittent water supply is unavoidable in water shortage area and developing countries. But the intermittent water supply can introduce large pressure forces and rapid fluid accelerations into a water supply network. These disturbances may result in new pipe failure, leakage and secondary contamination. This paper proposed an improvement methodology to prevent the disturbances by intermittent water supply. For the study, the hydraulic variation of intermittent flow in water distribution system was measured and analyzed in the field by comparing with simulation of hydraulic model. Installations of control valves such as, pressure reducing and sustaining and air valves were employed for pressure and flow control. The effectiveness of the methods are presented by comparing hydraulic conditions before and after introducing the proposed solutions.

• Journal of the Korean Geotechnical Society
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• v.18 no.3
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• pp.105-112
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• 2002

Increases in excess pore water pressure without change of surcharge load were reported in clay underneath embankment at Berthierville and Olga sites after the end of construction. These abnormal phenomena could not be explained by classical consolidation theory. This paper presents a nonlinear viscoplastic model to interpret an increase in pore water pressure on natural clay, The proposed model can consider the combined processes of pore water pressure dissipation according to Darcy's law and pore water pressure generation due to viscoplastic strain, as well as time-dependent viscoplastic behaviour and strain rate dependency of preconsolidation pressure. The calculated results using numerical analysis are compared with measured ones under embankments built on soft clay at Berthierville and Olga in Quebec, Canada. It may be possible to explain the phenomenon of excess pore water pressure increase after the end of construction using the proposed nonlinear viscoplastic model.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.25-30
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• 2011

A fresh water generation system is designed for converting brackish water or seawater into fresh water. In this paper fresh water generation by distillation process that evaporates feed water and subsequently condenses vapor as evaporation product to get fresh water was studied and city water was employed as feed water. The system uses the ejector to create a vacuum, under which liquid can be evaporated at lower temperature than it at normal or atmospheric condition, hence less energy consumption. The effect of various operating conditions i.e. temperature of feed water and different orifice diameters were studied experimentally to investigate the characteristic of the system. It was found that these parameters have significant effect in the performance of fresh water generation system with low pressure evaporation.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.6
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• pp.63-73
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• 2014

In this study, the large scale test was performed to investigate the behavior of failure on the embankment and spillway transitional zone by overtopping. The pore water pressure, earth pressure, settlement and failure behaviors according to several reinforcing method were compared and analyzed. The pore water pressure showed a small change in the spillway transition zone and core, indicating that the riprap and geotextile efficiently reinforced the embankment, but non-reinforcement showed a largely change in pore water pressure. The earth pressure by riprap and geotextile at upstream slope and bottom core increased rapidly with the infiltration of the pore water by overtopping. And the earth pressure at crest showed a smally change due to effect of the inclined core. A settlement by riprap showed a small change and the geotextile decreased a rapidly due to failure of crest. The width of failure by riprap at intermediate stage (50 min) showed a largely due to sliding of crest. But, the width and depth of the seepage erosion after the intermediate overtopping period (100 min) were very small due to the effect of riprap than geotextile and non-reinforcement which delayed failure. It has the effect that protect reservoir embankment from erosion in the central part. The pore water pressure at the spillway transition zone due to overtopping increased a rapidly in the case of non-reinforcement, but the reinforced methods by geotextile and riprap showed a smally change. Therefore, the reinforced method by riprap and geotextile was a very effective method to protect permanently and the emergency an embankment due to overtopping, respectively.

• Journal of Korea Water Resources Association
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• v.46 no.11
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• pp.1103-1113
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• 2013

In this study, determination methods of the pressure monitoring location in water distribution system were introduced and applied to sample pipe network. The best determination method of the pressure monitoring location was suggested and applied to the real city pipe network. Three kinds of determination methods of pressure monitoring locations are categorized such as the sensitivity analysis according to changing roughness coefficient, pressure contribution analysis, and sensitivity analysis according to changing demand. Further-more, pressure contribution analysis and sensitivity analysis from the results of unsteady analysis were conducted and compared each other. From the results, the most accurate and simplest method was selected in this study. Therefore, the best method can be applied for the pressure management or leakage detection as a determination method of pressure monitoring location in water distribution system.

• Korean Journal of Hydrosciences
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• v.6
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• pp.99-105
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• 1995

External forecs acting on a pipe bend change when a transient pressure wave propagates through the bend. Analytical expressions are derived to compute the changes of these forces which depend mainly on static pressure rather than fluid momentum. This analysis reveals that the change of the vertical component of the force acting on a pipe bend with an angle larger than 90 may reverse in direction during the passage of a pressure wave through the bend.