• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.162-181
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• 1990

The hydrodynamic model is used to analyse the sea surface elevations derived from the SEASAT altimetry over the Yellow Sea and the East China Sea. Periods of significant atmospheric disturbances during the SEASAT mission are selected for this study. These includes periods of July 28-August 2 and August 18-21. Meteoroloeical forcing functions, which are needed for the sea model, are derived by a 2-dimensional grid that is governed by a set of theoretical and empirical meteorological relations over the study area. Ocean tides in this area are known to be significant and introduce a large spatial and time variability in the sea surface elevation. Consequently major tidal constituents of M$_2$, S$_2$, $K_1$ and $O_1$ are included in the computation. With some knowledge of other known sea surface phenomena e.g.(body tide, loading tide), the time-dependent sea surface variation is predicted to com-pare statistically with the satellite altimetric measurements and to achieve the objective of ocean bottom friction study. From a total of 10 SEAST orbit tracks, a friction coefficeint was found ranging from 0.0023 to 0.0027.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.4
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• pp.439-451
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• 1994

A numerical model for harbour oscillation is presented by use of Galerkin finite element method. The governing equation is used by the modified mild slope equation derived from Chen (1986) in which bottom friction is incorporated. Since the existing absorbing boundary condition. however. is shown to be incorrect correct boundary condition and forcing term due to an incident plane wave are rederived. Computation results for a rectangular harbour are shown in comparison with both laboratory data and existing numerical results. After the values of friction factor (f) and reflection coefficient (K$_{r}$) are discussed, the set (K$_{r}$=0, 94, f=0) is found to be best fitted to the laboratory data of the rectangular harbour.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.700-707
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• 1997

In order to express exactly the total resistance of bottom trawl nets subjected simultaneously to the water flow and the bottom friction, the influence of frictional force was added to the formular for the flow resistance of trawl nets obtained by previous papev and the experimental data obtained by other investigators were analyzed by the formula. The analyzation produced the total resistance R (kg) expressed as $$R=4.5(\frac{S_n}{S_m})^{1.2}S\;v^{-1.8}+20(Bv)^{1.1}$$ where $S(m^2)$ was the wall area of nets, $S_m\;(m^2)$ the cross-sectional area of net mouths, $S_n\;(m^2)$ the area of nets projected to the plane perpendicular to the water flow, B (m) the made-up circumference at the fore edge of bag parts, and v(m/sec) the dragging velocity. From the viewpoint that expressing R in the form of $R=kSv^2$ was a usual practice, however, the resistant coefficient $k(kg{\cdot}sec^2/m^4)$ was compared with the factors influencing it by reusing the experimental data. The comparison gave that the coefficient k might be expressed approximately as a function of BL only and so the resistance R (kg) as $$R=18{\alpha}B^{0.5}L\;v^{1.5}$$ where L (m) was the made-up total length of nets and $\alpha=S/BL$. But the values of a in the nets did not deviate largely from their mean, 0.48, for all the nets and so the general expression of R (kg) for all the bottom trawl nets could be written as $$R=9\;B^{0.5}\;L\;v^{1.5}$$.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.17-23
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• 2000

Experimental investigations were conducted to study the forced convection of fully-developed turbulent flow in horizontal equilateral duct fabricated with the same length and equivalent diameter, but different surface roughness pitch ratio(P/e) of 4, 8 and 16 on the one side wall only. The experiments were performed with the hydraulic diameter based Reynolds number ranged from 70,000 to 10,000. The entire bottom wall of the duct was heated uniformly and the other surfaces were thermally insulated. To understand the mechanisms of the heat transfer enhancement, measurements of the heat transfer were done to investigate the contributive factor of heat transfer promotion, namely, the fin effect. And the results were compared with those of previous investigations for similarly configured channels, at which they were roughened by regularly spaced transverse ribs in the rectangular and circular channels.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.65-70
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• 2000

Experimental investigations were conducted to study the forced convection of fully-developed turbulent f)on· in horizontal equilateral duct fabricated with the same length and equivalent diameter, but different surface roughness Pitch ratio(P/e) of 4, 8 and 16 on the one side wall only The experiments were performed with the hydraulic diameter based Reynolds number ranged from 70.000 to 10,000 The entire bottom wall of the duct was heated uniformly and the other surfaces were thermally insulated. To understand the mechanisms of the heat transfer enhancement. measurements of the heat transfer were done to investigate the contributive factor of heat transfer promotion. namely the fin effect. And the results were compared with those of Previous investigations for similarly configured channels, at which they were roughened by regularly spaced transverse ribs in the rectangular and circular channels.

• Transactions of Materials Processing
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• v.29 no.6
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• pp.301-306
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• 2020

The parametric study of Steel-Al alloy SPR joint process is based on the FE simulation described by Kim et al. [10], which was validated by comparing experimental and simulation results for two kinds of steel-Al alloy combinations according to the lower sheet thickness. To analyze the SPR joint process, the friction coefficient, the lower sheet thickness, and the rivet length were selected as the main parameters. Based on FE simulations, the effect of main parameters was investigated by measuring the interlock and the bottom thickness at the cross-sectional shape of the SPR joint. The results of simulation facilitate the design of SPR joint process in various metal combinations.

• Journal of Industrial Technology
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• v.20 no.A
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• pp.139-148
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• 2000

A numerical model is represented to calculate the wave fields such as the reflected waves, the transmitted waves, and depth averaged velocities over submerged breakwaters for the normally incident wave trains of nonlinear monochromatic wave. The numerical model is correctly formulated by using both the finite amplitude shallow water equations with the effects of bottom friction and the explicit dissipative Lax-Wendroff finite difference scheme, also satisfactorily verified by comparison with the other results. The behaviors of reflected and transmitted waves with respect to geometric parameters of submerged breakwater such as the slope, crest depth, and crest width are numerically analyzed in this study. In particular, the reflection and transmission coefficients are quantitatively calculated as the function of geometric parameter of submerged breakwater. It is found that the crest depth among parameters related to practical design may be the most important parameter in designing the submerged breakwater. Therefore, the effective and economic performances of submerged breakwater should be depended on the determination of optimal crest depth.

• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.74-79
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• 2012

The present study aims at suggesting the systematic approach to analyze the local drag components as the resistance performance characterized by the flow of the ship. In order to identify the local areas, the hull surface is decomposed into SVM (Station-Vertical Section Map) which consists of 20 stations along the longitudinal direction and 20 sections along the vertical direction (from the bottom to the waterline). Successively, on the SVM, the friction and pressure drag coefficients as the components of total drag coefficient have been analyzed for two different hull forms of Wigley and KVLCC by using CFD.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.59-61
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• 2013

The purpose of this study was to present the necessary data concerning the selection and development of floor-coverings in view of slipperiness by comparing the relationship between CSR measured with O-Y·PSM and RCOF calculated from the result of gait analysis. CSR was calculated from maximum tensile load(Pmax) divided by perpendicular load(785N) when pulled 18 degrees upward the moment the bottom of the slip piece contacted the surface of the test piece. RCOF was calculated based on Fy/Fz from when horizontal load reached the maximum point within the sections from the moment the front of outsole touched the test piece to when pulled off the test piece. The results from the research were as follows: (1) Range of CSR was 0.15-1.02, which meant the differences of slipperiness of the test pieces definitely showed up. (2) RCOF are inadequate to express the characteristic about the slipperiness of the floors, since there were no differences between the test pieces.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.4
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• pp.313-325
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• 2011

Finite element grid system using h-refinement on the Yellow Sea was constructed based on previous study (Suh, 1999b) from 14 K to 210 K and special attention was concentrated on refining the coastal zone. In grid generation, depth change between adjacent points and non-dimensional tidal wave length ratio were considered. As a result approximately a quarter of the total nodes are located nearby 5 m of shallow area. Accurate bathymetry data using 30's and ETOPO1 with open boundary conditions of 8 major tidal constituents extracted automatically from FES2004 have been applied. In tidal simulation a 3-dimensional nonlinear harmonic model was setup and tidal amplification due to changes in vertical turbulent and bottom friction were simulated. In this study not only 8 major tidal constituents but also nonlinear shallow tides $M_4,$, $MS_4$ and long period $M_f,$, $M_{sf}$ were reproduced. It is found that implication of spatial variation of friction coefficient plays a very important role in reproduction of astronomical and shallow tides which are computed by iterative computation of nonlinear terms. Also it should be considered differently with respect to tidal periods. To understand the distribution of tidal asymmetry, amplitude ratio of $M_4/M_2$ and phase differences $2g(M_2)-g(M_4)$ were calculated. Tidal distortion ratio marks up to 0.2 on the west coast showing shallow coastal characteristics and somewhat wide range of ebb-dominances in front of Mokpo area are reproduced.