Hydrodynamic interactions and relative motions of two floating platforms with mooring lines in side-by-side offloading operation     

B.J. Koo  M.H. Kim   《Applied Ocean Research》2005,27(6):292-310

The hydrodynamic interaction and mechanical coupling effects of two floating platforms connected by elastic lines are investigated by using a time-domain multi-hull/mooring/riser coupled dynamics analysis program. Particular attention is paid to the contribution of off-diagonal hydrodynamic interaction terms on the relative motions during side-by-side offloading operation. In this regard, the exact method (CMM: combined matrix method) including all the vessel and line dynamics, and the 12×12 hydrodynamic coefficients in a combined matrix is developed. The performance of two typical approximation methods (NHI/No Hydrodynamic Interaction: iteration method between two vessels without considering hydrodynamic interaction effects; SMM/Separated Matrix Method: iteration method between two vessels with partially considering hydrodynamic interaction effects, i.e. ignoring off-diagonal cross-coupling terms in the 12×12 hydrodynamic coefficient matrix) is also tested for the same side-by-side offloading operation in two different environmental conditions. The numerical examples show that there exists significant discrepancy at sway and roll modes between the exact and the approximation methods, which means that the cross-coupling (off-diagonal block) terms of the full hydrodynamic coefficient matrix play an important role in the case of side-by-side offloading operation. Therefore, such approximation methods should be used with care. The fender reaction forces, which exhibit large force with contact but no force without contact, are also numerically modeled in the present time-domain simulation study.  相似文献   

Fully nonlinear wave-body interactions with surface-piercing bodies   总被引：1，自引：0，他引：1  

W.C. Koo  M.H. Kim   《Ocean Engineering》2007,34(7):1000-1012

Fully nonlinear wave-body interactions for stationary surface-piercing single and double bodies are studied by a potential-theory-based fully nonlinear 2D numerical wave tank (NWT). The NWT was developed in time domain by using boundary element method (BEM) with constant panels. MEL free surface treatment and Runge–Kutta fourth-order time integration with smoothing scheme was used for free-surface time simulation. The acceleration-potential scheme is employed to obtain accurate time derivative of velocity potential. Using the steady part of nonlinear force time histories, mean and a series of higher-harmonic force components are calculated and compared with the experimental and numerical results of other researchers. The slow-decaying second-harmonic vertical forces are investigated with particle velocities and corresponding body pressure. Typical patterns of two-body interactions, shielding effect, and the pumping/sloshing modes of water column in various gap distances are investigated. The pumping mode in low frequencies is demonstrated by the comparison of velocity magnitudes.  相似文献   

Effect of environmental conditions on variation in the sediment-water interface created by complex macrofaunal burrows on a tidal flat   总被引：1，自引：0，他引：1  

Bon Joo Koo  Kae Kyoung Kwon  Jung-Ho Hyun 《Journal of Sea Research》2007,58(4):302-312

We quantified the increase in the sediment-water interface created by the burrowing activities of the resident macrofaunal community and its variation with respect to the physical conditions of the habitat on a tidal fat. We investigated environmental factors and dimensions of macrofaunal burrows with respect to tidal height and vegetation during spring and summer at three sites. A resin-casting method was used to quantify the dimensions of all burrows at each site. The dimensions of macrofaunal burrows varied both temporally and spatially and the increase in the sediment-water interface reached a maximum of 311%, ranging from 20 to 255% under different habitat conditions. The sediment-water interface depended on the duration of exposure resulting from tidal height, increased temperatures resulting from seasonality, and marsh plant density. Burrows were deeper and more expansive at both higher tidal levels and higher temperatures in summer. Burrow dimensions were sharply reduced with the disappearance of adult macrofauna in areas where the roots of the marsh plant Suaeda japonica were dense. The significance of this study lies in quantifying the burrow dimensions of the entire macrofaunal community, rather than just a single population, and confirming their spatial and temporal variation with respect to physical conditions of the habitat. Environmental factors responsible for variation in burrow dimensions are discussed.  相似文献   

Geology, Mineralogy and Geochemistry of Carbonate Replacement-Type Lead-Zinc-Silver Deposits in Janggun Mine, Republic of Korea     

Lee Hyun Koo Lee Chan Hee Yoo Bong Cheal Lee Jong Chang Department of Geology  Chungnam National University  Taejon  Korea 《中国地质大学学报(英文版)》2000,11(2)

INTRODUCTIONThe Janggun mine,Republic of Korea,is located in thesoutheast of the Seoul,about latitude36°5 1′N and longitude12 9°0 4′E. In this mine area is situated the Bonghwa m ineral-ized zone of the Taebaegsan mining district,Korea.The geo-logic setting of the region was described as the Samgeum riQuadrangle(Kim et al.,196 2 ) .The general and local geolo-gy near the mine area have been studied by L ee (196 7) ,Hwang and Reedman(1975 ) .This mine consists of four min-eral de…  相似文献   

Galactic HCO<Superscript>+</Superscript> absorption toward compact extragalactic radio sources     

Geumsook Park  Bon-Chul Koo  Kee-Tae Kim  Do-Young Byun  Carl E. Heiles 《Astrophysics and Space Science》2018,363(7):150

As part of the search for the “dark molecular gas (DMG),” we report on the results of HCO⁺\(J=1\mbox{--}0\) absorption observations toward nine bright extragalactic millimeter wave continuum sources. The extragalactic sources are at high Galactic latitudes (\(|b| > 10^{\circ} \)) and seen at small extinction (\(E(B - V)\lesssim 0.1\) mag). We have detected the HCO⁺ absorption lines toward two sources, B0838+133 and B2251+158. The absorption toward B2251+158 was previously reported, while the absorption toward B0838+133 is a new detection. We derive hydrogen column densities or their upper limits toward the nine sources from our observations and compare them to those expected from CO line emission and far-infrared dust continuum emission. Toward the seven sources with no HCO⁺ detection, CO emission has not been detected, either. Thus the sight lines are likely to be filled with almost pure atomic gas. Toward the two sources with HCO⁺ detection, CO emission has been also detected. Comparison of the H₂ column densities from HCO⁺ absorption and CO emission suggests a non-negligible amount of DMG toward B0838+133.  相似文献   

Does the restoration of an inner-city stream in Seoul affect local thermal environment?     

Y.-H. Kim  S.-B. Ryoo  J.-J. Baik  I.-S. Park  H.-J. Koo  J.-C. Nam 《Theoretical and Applied Climatology》2008,92(3-4):239-248

Summary Changes in local thermal environment associated with the restoration of an inner-city stream in Seoul, Korea, are investigated using observational data. The stream, called the Cheonggye stream, which had been hidden and covered with cement/asphalt for 46 years, runs 5.8 km eastward through a central region of Seoul. Intensive observations were made in the stream area for a number of summertime periods before, during, and after the stream restoration to detect the effects of the stream on local environment and to quantify them. It is estimated that after the stream restoration the near-surface temperature averaged over the stream area dropped by 0.4 °C, with the largest local temperature drop being 0.9 °C. However, it cannot be stated that this 0.4 °C temperature drop is due entirely to the stream effect only, because synoptic-scale and local-scale weather conditions during the two periods were inevitably not identical. The stream effect on air temperature is also evident in the temperature distribution along a street traversing the stream. In the daytime after the stream restoration, the sensible heat flux was greatly reduced and the ratio of sensible heat flux to net radiative flux dramatically decreased. These first-time results of the restored-stream effects on urban thermal environment could contribute to the scientific basis of urban planning which aims to make a large city comfortable to live in and nature- and environment-friendly. Authors’ addresses: Yeon-Hee Kim, Il-Soo Park, Hae-Jung Koo, and Jae-Cheol Nam, Meteorological Research Institute, Korea Meteorological Administration, Seoul 156-720, Korea; Sang-Boom Ryoo, Suwon Meteorological Office, Korea Meteorological Administration, Suwon 441-856, Korea; Jong-Jin Baik, School of Earth and Environmental Sciences, Seoul National University, Seoul 151-742, Korea  相似文献   

Keck spectroscopy and imaging of faint galaxies identified as microjansky radio sources     

Nathan D.Roche  James D.Lowenthal  David C.Koo 《Monthly notices of the Royal Astronomical Society》2002,330(2):307-328

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The DEEP2 Galaxy Redshift Survey: the relationship between galaxy properties and environment at z∼ 1     

Michael C. Cooper  Jeffrey A. Newman †  Darren J. Croton  Benjamin J. Weiner  Christopher N. A. Willmer  Brian F. Gerke  Darren S. Madgwick †  S. M. Faber  Marc Davis  Alison L. Coil †  Douglas P. Finkbeiner  Puragra Guhathakurta  David C. Koo 《Monthly notices of the Royal Astronomical Society》2006,370(1):198-212

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Pattern and origin of spherulites in a rhyolite dike swarm,northeastern Cheongsong, Korea     

Sang Koo Hwang  Chang Oh Choo 《世界地质(英文版)》2006,9(1)

Several NNW-trending Cretaceous rhyolite dikes in the northeastern Cheongsong area of southern Korea contain spherulitic fabrics and are locally quarried as an ornamental stone. The dikes, part of the Cheongsong dike swarm, contain a variety of spherulites which are characterized by radial array of acicular intergrowths from fibrous quartz and alkali feldspars. They are classified as some simple, multiple and compound spherulite types from flower-like patterns, and the types are different each other in spatial distribution within the dikes. The various radial fabrics suggest that they crystallized under the different cooling mechanisms and processes in rapidly cooling dikes. Spheroids lacking a flower-like pattern may be precipitated after compositional segregation in a supercooled magma. Simple acicular spherulites could be crystallized by devitrification of true glass which cooled rapidly below the transformation temperature, whereas layered multiple spherulites could result from a crystallization of supercooled magma at relatively rapid cooling rates above the transformation temperature. Acicular multiple spherulites could be produced from a combination of the above three mechanisms operating at slower cooling rates.  相似文献   

A numerical model for estimating groundwater flux from subsurface temperature profiles     

Ashok K. Keshari  Min-Ho Koo 《水文研究》2007,21(25):3440-3448

A simple numerical model is presented for estimating vertical groundwater flux from transient subsurface temperature profiles obtained from field measurements. The model developed utilizes the MacCormack scheme, which is based on the Finite Difference Method (FDM), for solving the governing partial differential equation of convection–diffusion heat transport with appropriate initial and boundary conditions within the subsurface. In order to validate the model, numerical solutions obtained for the study area located in the Nagoka plain, Japan are compared with the published measured data and results obtained by others. Results obtained show good agreement and fit the observed data with a correlation coefficient, R², of 0·88. The estimated groundwater flux is 1·85 × 10⁻⁷ m s⁻¹. Sensitivity analyses were also carried out to investigate the effect of variations in groundwater fluxes, thermal properties and the annual thermal variability due to climatic changes on the transient subsurface temperature profiles and to have a better understanding of the subsurface thermal dynamics. A substantial effect of annual climatic variability is observed on the temporal distributions of temperature depth profiles, and a better estimate of thermal parameters is required to estimate vertical groundwater flux. The largest change in subsurface temperature depth profiles due to groundwater flux over a year is within ± 4 °C. The influence of groundwater flux on subsurface temperature distributions in space and time may be more pronounced in areas where the top of the saturated layer fluctuates considerably. Variation in thermal diffusivity results in temperature change up to ± 1·5% and may cause change in groundwater flux estimate by ± 18%. The model presented has merits over analytical solutions (type curve matching techniques) in terms of suitability and applicability to real field problems, and can be a good asset to hydrological models as quantifying groundwater recharge or deducing it from other quantities, such as rainfall, evapotranspiration and runoff, is often complicated. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献