• Journal of Ship and Ocean Technology
• /
• v.4 no.2
• /
• pp.24-37
• /
• 2000

The purpose of this paper is to study the upstream waves in front of an advancing arbitrary hull shape in a restricted water channel. Conventionally, in a restricted water channel, shallow water effects are amplified because of the finite water depth and width. When the effects of shallow water and the restricted channel width are severe, upstream waves propagate forward from the fore-body of the advancing hull. In this study, numerical simulations are carried out for the relevant analysis of the flow phenomena by the draft variation of advancing hull in a restricted water channel. Numerical simulations are done with a finite-difference method based on the MAC scheme in a rectangular grid system.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.4
• /
• pp.2860-2867
• /
• 2015

Stable channel design is to determine the width, depth and slope for satisfying the condition that the upstream incoming sediment rate is equal to the sediment transport rate at the design channel. Therefore, the most sensitive variable when designing a stable channel is the selection of a sediment transport equation applied for the channel design. Especially if in the case of gravel beds the designer uses the equation developed by using the data of sand rivers, the calculation result of the stable channel section has large errors. In this study, the stable channel design has been applied to the gravel bed river using the previous stable channel design program with newly added the sediment transport equation for gravel beds; and the stable channel section considering design constraints has been produced by using the analytical method. As results, in the case of the application with the fixed width, the depth predicted by Ackers and White's equation was the shallowest and Meyer-Peter and $M\ddot{u}ller's$ equation was 0.8 m deeper than the current section of 2.4 m. In the case of the application with the fixed depth, the width predicted by Engelund and Hansen's equation was twice wider than the current section and by Meyer-Peter and $M\ddot{u}ller's$ equation was 20 m wider than the current section of 44 m.

• Ecology and Resilient Infrastructure
• /
• v.6 no.4
• /
• pp.314-327
• /
• 2019

This study investigates channel stabilities with groynes by developing the assessment of it and applying a 2-dimensional numerical model, which simulates flow and sediment transport with various flows in the channel. Evaluation inventories are composed of five items, which are width to depth ratio, sinuosity, bed slopes, velocities in the flow flied, Shields number with discharges and geomorphic characteristics in the study reach. The channel stability is evaluated by applying the evaluation indicators to the channel with and without groynes in the study reach between Dalseong-weir and Gangjeonggoryeong-weir in the Nakdong river. Width to depth ratio, sinuosity, and bed slopes, which are index of river characteristics, little affect the channel stability. However, velocities in the flow flied, and Shields number, which is dimensionless tractive, near the banks of the channel strongly affect the stability. The evaluation values of the stability in the channel on the left and right banks decrease as the number of groynes increase in both the left and right banks, which means that the bank stability increases with the groynes.

• Journal of Korea Water Resources Association
• /
• v.35 no.3
• /
• pp.241-250
• /
• 2002

In this study, the method of Cheema et al., which is used to decide stable width and depth of the small alluvial rivers, is improved to consider the stability of mass failure and shear failure of the bank effectively. This improved method is applied to the actual rivers, and this result is compared with the result of the method of Cheema et at.. While the method of Cheema et al. could be applied to the alluvial rivers with channel width below 50m, this improved method shows good results in estimating stable width and depth up to 200m. Therefore, this improved method can be suggested as an effective technique in the profile design of small alluvial rivers.

• 한국가시화정보학회:학술대회논문집
• /
• 2004.12a
• /
• pp.125-134
• /
• 2004

The improvement of artificial respiration method has brought about the decrease in mortality of pulmonary diseases patients. Various respiratory curative methods, inclusive of HFOV (High Frequency Oscillatory Ventilation), have been developed for more effectual and less harmful management of acute respiratory failure. However, the mechanism of gas transfer and diffusion in a bronchiole has not yet been clarified in detail. As a first approach to the problem, we measured oscillatory flows in a Y-shaped micro-channels as bronchiole model by micro Particle Image Velocimetry(micro PIV). In order to establish the fundamental technique of PIV measurements on oscillatory air flow in a micro-channel, we used about 500-nm-diameter incense smoke particles, a diode laser, a high speed camera including an objective lens, and a HFOV, which is effective technique for medical care of pulmonary disease patients, especially, infants. The bronchiole model size is that parent tube is $500\{mu}m$ width and $500\{mu}m$ depth, and daughter tubes are $450\{mu}m$ width and $500\{mu}m$ depth. From this study made on the phenomenon of fluid in micro size bronchus branch of a lung, we succeeded to get time series velocity distribution in a micro scale bronchial mode. The experimental results of velocity distribution changing with time obtained by micro PIV can give fundamental knowledge on oscillatory airflow in micro-channel.

• KCID journal
• /
• v.21 no.1
• /
• pp.118-126
• /
• 2014

In this study, the use of the spur of riverbank technique is being investigated. The spur of the riverbank typically reduces the velocity of flow and protects the embankments by increasing friction along the water and the banks. This also has an effect in the rise of water level upstream. It is also used for the rectification of riverside line and restoration of the waterway through sedimentation near the spur of the riverbank. In this study, physical-scaled experiments are conducted to investigate the process of creating a mild meandering channel using the spur of the riverbank with varying water flows and sedimentation functions. The hydraulics observations are taken with respect to the varying heights and length of the riverbank's spurs and the distance between each spur for the formation of the mild meandering channel. It is observed that for 1.06 times of the meander length, it requires 2 times of the interval with each spur of river width. Similarly, 1.25L times of the meander length, it requires 0.5 times of the interval with each spur of river width. The sand accumulation is induced by the spur of riverbank when the spur of riverbank's heights are more than 40% of water depth and the length of the spur of riverbank needs under than 20% of river width for avoid exaggerated sand accumulation in the center of channel.

• Journal of the Korea Concrete Institute
• /
• v.19 no.6
• /
• pp.707-715
• /
• 2007

The vulnerability of concrete to its environment is significantly dependent on the fact that concrete is a porous material. For well-consolidated and well-cured concrete, its service life is a very long and an entrance of aggressive substance might be only pores. However, for cracked concrete, cracks should be preferential channel for the penetration of aggressive substance such as chloride ions. The effect of crack on chloride penetration depends on its size for example, crack width and crack depth. The purpose of this study is examining the effect of crack width and crack depth on chloride penetration. In order to visualize chloride penetration via cracks, RCM (rapid chloride migration) testing is accomplished. Crack width is examined using an optical microscope and CMOD value is used to estimate average crack width. From the examination on the trend of chloride diffusion coefficients of concrete specimens with various crack widths, a critical crack width and a critical crack depth are found out.

• Proceedings of KOSOMES biannual meeting
• /
• 2018.06a
• /
• pp.45-45
• /
• 2018

• Journal of the Korean Institute of Landscape Architecture
• /
• v.25 no.4
• /
• pp.39-50
• /
• 1998

The object of this study was to examine and analyze the environmental deterioration of three major trails and around peak area of Moaksan Provincial park in 1996. Trails are mostly made up at ridgeline and the slope of them is gentle. Mean trail width is 3.6m, and total length of branch trails is 982m in survey area. The environmental deterioration is derived from trail extension. Maximum eroded depth and cross-section area loss are 89cm and 14,050cm2 respectively, and gully erosion type appears at many sites. The environmental deterioration of trails is very heavy at the sections from Khui to Moaksan peak and from Moakchong to ascent part around the peak. The entire width, branch trail, maximum depth, cross-sectional area loss and surface roughness, as the indexes of trail conditions, are significantly greater at the more heavily used trails. Amount of erosion is influenced by eroded depth, longitudinal slope, runoff influence and entire width in descending order as well as the amount of use. Safety and protection facilities on the trail such as stone and soil stairs, rope handrail, stone channel and soil ditch work are built, but they are very deficient. Bared lands about 4,900m2 and fill slopes are caused and formed by recreation activities and constructions around peak area. It is required to carry the recess system and to conserve and rehabilitate the destroyed trail sites and bare fill slopes as soon as possible, before the environmental deterioration becomes critical because of increased used amount in consequence of construction of recreation parks.

• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.911-913
• /
• 1999

Shallow Trench Isolation (STI) has become the most promising isolation scheme for ULSI applications. The stress of STI structure is one of several factors to degrade characteristics of a device. The stress contours or STI structure vary with the trench depth. Isolation characteristics of STI was analyzed as the depth of trench varied. And transistor characteristics was compared. Isolation punch-through voltage for n$^{＋}$ to pwell and p$^{＋}$ to nwell increased as trench depth increased. n$^{＋}$ to pwell leakage current had nothing to do with trench depth but n$^{＋}$ to pwell leakage current decreased as trench depth increased. In the case of transistor characteristics, short channel effect was independent on trench depth and inverse narrow width effect was greater for deeper trenches. Therefore in order to achieve stable device, it is important to minimize stress by optimizing trench depth.