• Ocean Systems Engineering
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• v.4 no.4
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• pp.263-278
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• 2014

The spudcan requires the suitable design considering the soil, platform, and environmental conditions. Its shape needs to be designed to secure sufficient reaction of soil so that it can prevent overturning accidents. Its shape also has to minimize the installation and extraction time. Even in the same soil condition, the reaction of soil may be different depending on the shape of spud can, mainly the slope of top and bottom plates. Therefore, in this study, the relation between the slope of plates and the reaction of soil with and without water jetting is analyzed to better understand their interactions and correlations. For the investigation, a wind turbine installation jack-up rig (WTIJ) is selected as the target platform and the Gulf of Mexico is considered as the target site. A multi layered (sand overlying two clays) soil profile is applied as the assumed soil condition and the soil-structure interaction (SSI) analysis is performed by using ANSYS to analyze the effect of the slope change of the bottom plate and water jetting on the reaction of soil. This kind of investigation and simulation is needed to develop optimal and smart spudcan with water-jetting control in the future.

• Journal of Korean Society of Water and Wastewater
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• v.24 no.2
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• pp.219-230
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• 2010

Computer simulation has been widely used to design and optimize the operation of wastewater treatment plants since 1980. For secondary clarifiers, the simulation has been a tool to optimize the performance by providing dimensions for flocculation well. However, there has been no attempt to find the optimized geometrical parameters in circular secondary clarifier using simulation tools. In this study, three SVIs (Sludge Volume Indexes), two well types (feed and flocculation wells), 8 SWDs (Side Water Depths) and 9 bottom slopes were variables for simulation. Diurnal inflow and associated MLSS (Mixed Liquor Suspended Solid) concentrations were used for input loadings. When flocculation well was installed, 48% less concentration at lowest ESS (Effluent Suspended Solid) concentrations was produced and the diurnal ESS concentration range had been reduced by 52%. From these results, flocculation well must be installed to produce lower and stable ESS from circular secondary clarifiers. Under same loading conditions with $300m{\ell}$/g of SVI, The lowest ESS was produced when SWD was 4.5m with 4% of bottom slope. Therefore, SWD and bottom slope must not be deeper than 4.5m and must be near 4%, respectively, in circular clarifier with flocculation well to produce the lowest ESS concentration.

• Water for future
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• v.20 no.3
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• pp.237-245
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• 1987

The behavior of negative buoyant flow into a reservoir with sloping bottom is analysed by numerical solution technique of the governing equations composed of continuty, momentum and constituent transport equation. The stable plunge point and maximum travel distance are found to be dependent on the bottom slope of reservoir as well as inflow densimetric Froude number, $Fr_e$. They are also related closely to a vortex formed just downstream from the plunge point and above the underflow. The plunge depth was shown to be a function of th bottom slope and $Fr_e$. The plunge depths obtained in this numerical study agree relatively well with published data and theoretical studies, and its predictive equation is derived.

• Ocean Systems Engineering
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• v.12 no.4
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• pp.385-402
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• 2022

This paper deals with the study of hydrodynamic pressure in reservoir adjacent to the concrete gravity dam subjected to dynamic excitation. Widely famous finite element method is used to discretize the reservoir domain for modelling purpose. Pressure is considered as nodal variable following Eulerian approach. A suitable nonreflecting boundary condition is applied at truncated face of reservoir to make the infinite reservoir to finite one for saving the computational cost. Thorough studies have been done on generation of hydrodynamic pressure in reservoir with variation of different geometrical properties. Velocity profile and hydrodynamic pressure are observed due to harmonic excitation for variation of inclination angle of dam reservoir interface. Effect of bottom slope angle and inclined length of reservoir bottom on hydrodynamic pressure coefficient of reservoir are also observed. There is significant increase in hydrodynamic pressure and distinct changes in velocity profile of reservoir are noticeable for change in inclination angle of dam reservoir interface. Change of bottom slope and inclined length of reservoir bottom are also governing factor for variation of hydrodynamic pressure in reservoir subjected to dynamic excitation.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.1
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• pp.99-109
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• 2015

In the construction industry, the interest for recycling aggregates is rising as more people demand for alternatives due to lack of supply of natural aggregates and environmental problems. However, in order for recycled aggregates to be used in infrastructures, stability and other factors need to be verified. Therefore, the objective of this study is to analyze the sensitivity of soil properties to secure slope safety according to various heights of embankment when bottom ash and dredged soil mixture is applied in the embankment. In most cases, all heights were safe for the slide for the embankment whether the water level is full or sudden draw down. The result of the sensitivity analysis revealed that the unit weight of embankments is highest among all factors to be considered. However, the sensitivity of the unit weight became smaller and the sensitivity of the friction angle of embankments increased with the height of embankments. The sensitivity of factors of core materials is very small because the core has weaker physical properties than those of the embankment. The effect of the height for each factor is different for each slope and water levels. The sensitivity of the unit weight of embankments is most affected when the height is 60m in the upstream slope. To conclude, bottom ash and dredged soil mixture can be applied in the embankment and different factors must be considered in different scale because the sensitivity depends highly on the height of embankments.

• Proceedings of the KIEE Conference
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• 2008.10a
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• pp.131-132
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• 2008

We describe a fabrication method of submicron glass trenches which have embedded metal lines for the future application of nano-scale RF MEMS devices. The glass wafer was etched using two different conditions to identify the relationship between the slope of glass trenches and the slope of photroresist. A self-aligned metal photomask and negative photroresist (PR) slope were used to insert metal lines inside the glass trenches. The PR slope patterned by backside photolithography was affected by the profile of preformed glass trenches. Gold was well fabricated in the $0.7{\mu}m$ wide trench thanks to the negative PR slope. Nano-scale glass trenches with embedded metal lines can be used as a bottom electrode in submicron beam resonators operating with a high resonant frequency.

• The Journal of the Korea Contents Association
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• v.12 no.3
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• pp.434-441
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• 2012

An analytic solution to the extended mild-slope equation was derived for waves propagating over an axi-symmetric pit. The water depth inside the pit was in proportion to a power of radial distance from the center of pit. The equation was transformed into the ordinary differential equation using the method of separation of variables. The coefficients of differential terms were expressed as an explicit form composing of the phase and group velocities. The bottom curvature and the square of bottom slope terms, which were added to the extended mild-slope equation, were expressed as power series. Finally, using the Frobenius series, the analytic solution to the extended mild-slope equation was derived. The present analytic solution was validated by comparing with the numerical solution obtained from FEM.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.209-212
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• 2002

Since Berkhoff proposed the mild-slope equation in 1972, it has widely been used for calculation of shallow water wave transformation. Recently, it was extended to give an extended mild-slope equation, which includes the bottom slope squared term and bottom curvature term so as to be capable of modeling wave transformation on rapidly varying topography. These equations were derived by integrating the Laplace equation vertically. In the present study, we develop a finite element model to solve the Laplace equation directly while keeping the same computational efficiency as the mild-slope equation. This model assumes the vertical variation of wave potential as a cosine hyperbolic function as done in the derivation of the mild-slope equation, and the Galerkin method is used to discretize . The computational domain was discretized with proper finite elements, while the radiation condition at infinity was treated by introducing the concept of an infinite element. The upper boundary condition can be either free surface or a solid structure. The applicability of the developed model was verified through example analyses of two-dimensional wave reflection and transmission. .

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.845-854
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• 1998

Following the approach of Ebersole (1985), water wave transformation is predicted using the eikonal equation and transport equation for wave energy which are reduced from the extended mild-slope equation of Massel (1993), and also the irrotationality of wave number vectors. The higher-order bottom effect terms, i.e., squared bottom slope and bottom curvature, are neglected in the study of Ebersole but are included in the present study. It was expected that, if these terms are included in this study, the approach would give more accurate solution in the case of rapidly varying topography. But, the expectation was frustrated. It is probably because, in the case of rapidly varying topography, the diffraction effect which is included in the eikonal equation does not work well and thus the solution is deteriorated.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.2
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• pp.173-182
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• 1994

A numerical experiment on the effective discharge of waste materials caused in recirculating aquaculture basins was performed. The numerical model used in this study was a 4-level hydrodynamic and advection-diffusion model. Flow structures and settling processes of ss in the various mathematical model basins are discussed. The calculated flow fields of the numerical basin corresponded well with the measured velocity in field basin. In the cases of steep bottom slopes in 4/30, the non-dimensional tractive force($U{\ast}/U{\ast}_c$) which is all important parameter for the deposition pattern of waste materials was stronger than with the mild slope one. The settling pattern of ss depended considerably on the degree of bottom slope of basin. To concentrate deposited waste materials into the center discharge pipe, it is useful to design a cylindrical basin with a steeply conical bottom. In addition, to prevent movement of the deposit area away from the center, it is necessary to locate the circulating ducts at diametrically opposed points on the basin sides.