• Journal of Korean Society of Coastal and Ocean Engineers
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• v.7 no.3
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• pp.257-264
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• 1995

Various factors are investigated on the bed load transport driven by waves and current, and proper forms of bed load transport formulas mainly used in river hydraulics are chosen for the estimation of combined flow bed load transport after considering the additional factors. The BYO Model is employed for the computation of maximum bed shear stress and mean bed shear stress of the combined flow. The friction factor of uni-directional flow is estimated by using modified Keulegan equation, and equivalent roughness height is determined by obtaining correct answer for the bed shear stress of uni-directional flow. Empirical constant in each bed load formula is determined by applying it to Bijker's laboratory data of bed load transport by waves and current and the formulas obtained are discussed on their final forms with the values of empirical constants.

• Water for future
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• v.26 no.1
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• pp.103-114
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• 1993

Migration characteristics with forms of channels and bed conditions are studied by constant-radius curve (CRC), sine-generated curve (SGC) and small-wave theory (SWT) method. For channels which are meandering and of which bed conditions are of coarse materials, transverse bed slope, depth and velocity distributions are predicted by CRC and SGC method, and the results are compared with measured field data, And for fine bed-materials of the sinuous channels, lateral and downvalley migration rates are computed by SWT method. It is confirmed from this investigation that transverse mass-flux factor plays significant roles in determining of magnitude and direction of meander migration.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.378-378
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• 2005

• Journal of the Korean Geophysical Society
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• v.6 no.2
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• pp.49-56
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• 2003

Under the attack of storm waves, there are many destructions of coastal structures in the forms of sinking and sliding. There types of destructions will be in close relation to the dynamic behavior of sand bed around the structures. Form this point of view, in this pear, we investigate the characteristics of the pore water pressure and effective stresses in the highly saturated sand bed under oscillating water pressure theoretically. The results indicate that the oscillating water pressure induce the notable drop of strength of and bed around the structure under certain condition.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.226-233
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• 1990

Fixed bed is known to be an effective heat transfer augmentation device which could be applied to heat exchangers. In this study, pressure drop in vertical cylindrical and annular fixed beds with air flowing through was experimentally investigated. Based on the experimental data and some analytical considerations, the demensionless correlation of pressure drop has been determined and shown in empirical forms. In particular, the experimental equation for the pressure drop was derived using the particle diameter and the bed diameter as variables, which would be more practical and useful in the design of heat transfer devices, instead of void fraction which had been used previously as the major variables by others. The present empirical equation obtained for the cylindrical fixed bed were found to be applicable also to an annular fixed bed when the concept of effective diameter was introduced.

• Korean Journal of Environmental Agriculture
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• v.27 no.1
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• pp.18-26
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• 2008

Behavior and decomposition velocity of pollutants on various forms from domestic sewage in sewage treatment plant were investigated in order to obtain the basic data for improving the removal efficiency of pollutants and to reduce the area in constructed wetland by natural purification method. The removal amounts of BODs and CODs in aerobic bed were significantly higher than those of the other beds. In aerobic bed, the removal amounts of IBOD and ICOD were more than those for SBOD and SCOD, respectively, whereas the removal amounts of BODs and CODs in anoxic and anaerobic beds were little different. The removal amounts of SSs in aerobic bed were also higher than those for the other beds, and the removal amounts of VSS in all beds were more than those for FSS. The removal amounts of DTN and DTP in all beds were more than those for STN and STP, respectively. In addition, the decomposition velocities of TBOD, TCOD and TSS in aerobic bed were 30.79, 17.15 and 29.96 $day^{-1}$. Moreover, the decomposition velocities of BODs, CODs and SSs in aerobic bed were very rapid than those in the other beds. On the other hand, the decomposition velocities of BODs, CODs and SSs in anoxic and anaerobic beds were a little different regardless of the forms of pollutant. The decomposition velocities constants of T-N in aerobic, anoxic and anaerobic beds were 4.78, 0.12 and 0.10 $day^{-1}$, respectively. Moreover, the decomposition velocities constants of T-P in aerobic, anoxic and anaerobic beds were 13.09, 0.12 and 0.13 $day^{-1}$ respectively. The decomposition velocity of T-Ns and T-Ps in aerobic bed were slightly rapid than those in the other beds, whereas the decomposition velocities of T-Ns and T-Ps in anoxic and anaerobic beds were slightly different regardless of the forms of pollutant.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.234-242
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• 1990

In this study, heat transfer characteristics of vertical fixed bed with air flowing through were experimentally investigated. The experiments were conducted for cases where heat was transfer steady state conditions from an immersed cylindrical heated to the surrounding fixed ved of steel balls. Based on the experimental data, the optimum conditions for heat transfer augmentation have been determined and shows in empirical forms. For the same power loss, comparison of heat transfer effect between the fixed bed and single phase forced convection device indicates that both miniaturization of heat exchange device and heat transfer augmentation at low flow velocity are possible by application of the fixed bed to heat exchangers. The present results could provide a useful design information for the heat exchangers where fixed beds are used.

• Proceedings of the Korea Water Resources Association Conference
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• 1994.02a
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• pp.107-112
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• 1994

• Journal of The Geomorphological Association of Korea
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• v.25 no.2
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• pp.15-29
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• 2018

The sediment transport process in a river reflects the process of geomorphological change in the watershed, influencesthe river bed variation and the river channel migration, and is a parametric phenomenon that exhibits a dynamic self-adjusting process. Sediment load is divided into bedload and suspended load depending on the dominant mechanism. Quantitative sediment load is important information for solving river problems. Because it is difficult and time consuming to measure bedload, compared to that ofsuspended load, data on the sediment transport load and the research required for the gravel-bed rivers are insufficient. This study is to analyze the ratio of the bedload to the total sediment load in gravel-bed rivers. The sediment load ratio in gravel-bed rivers increases with the flow rate per unit width, and the rate of the bedload varies more rapidly than the suspended load. The sediment transport efficiency coefficient has been affected by the ratio of the flow depth to the mean diameter of particles and has been dependent on the shear velocity Reynolds number. So $A^{\ast}$ and $B^{\ast}$ are introduced to compensate for the uncertainties such as bed materials, sediment transport, and flow velocity distribution, and the coefficient of bedload ratio has been presented. For the sediment load data in experimental channels and rivers, A* was 3.1. The dominant variables of $B^{\ast}$ were $u_*d_m/{\nu}$ in the gravel-bed and h/dm in the sand-bed. When $B^{\ast}$ the is the same, in the experimental channels the coefficient of bedload ratio was affected by the bed forms, but in the rivers it was of little difference between the gravel-bed and sand-bed.

• Journal of Korea Water Resources Association
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• v.39 no.9 s.170
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• pp.737-744
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• 2006

The velocity of the inner region of turbulent flow on a smooth bed has complex profile which can not be described with a simple formula. Though there have been a couple of formulas describing the profile, most of them have very complex forms, i.e., with many terms, with integration form, or with implicit forms. It means that it is hard to use them or it is difficult to estimate their parameters. A new single formula that describes the velocity profile of the inner region of the turbulent flow on a smooth bed was proposed. This formula has a form of the traditional log-law multiplied by a damping function. Introducing only one additional parameter, it can describe the whole inner range nicely. It approximates the law-of-the-wall in the vicinity of the bed and approaches to the log-law in the overlap region. The added parameter, damping factor, can be estimated very easily. It is not sensitive to the Reynolds number change and the velocity profile calculated by the formula does not change much due to the change of the parameter.