Modeling of Motion of Particle Clouds Formed by Dumping Dredged Material

The motion of particle clouds formed by dumping dredged material into quiescent waters is experimentally and numerically studied. In the numerical model, the particle phase is modeled by the dispersion model, and turbulence is calculated by the large eddy simulation. The governing equations, including the filtered Navier-Stokes equations and mass transport equation, are solved based on the operator-splitting algorithm and an implicit cubic spline interpolation scheme. The eddy viscosity is evaluated by the modified Smagorinsky model including the buoyancy term. Comparisons of main flow characteristics, including shape, size, average density excess, moving speed and the amount of particles deposited on the bed, between experimental and computational results show that the numerical model well predicts the motion of the cloud from the falling to spreading stage. The effects of silt-fence on the motion of the particle cloud are also investigated.     

Estimation of Water Particle Velocities by Empirical Transfer Function

-In previous and this studies it appears that the linear and nonlinear wave theory can notaccurately and easily predict the water particle velocities.Therefore,different from the theoretical consider-ations,in this study we have attempted to determine the transfer function empirically.Laboratory experi-ments were performed under various wave conditions.The empirical formulas of the transfer function ofthe wave height,angular frequency and water particle velocity were obtained on the basis of these test databy dimensional analysis and regression analysis.In intermediate and deep water depth conditions,thetransfer function was only a function of a nondimensional parameter which is composed of the angular fre-quency,the depth of the velocity gauge under the still water level,water depth and the acceleration of grav-ity.Finally,the empirical formulas were compared with experimental data and observational data formpresent and Cavaleri's(1978)studies.The empirical formulas were found to be in sufficient correl     

Numerical Study on Instantaneous Discharge of Unsorted Particle Cloud in Cross Flow

The mixing characteristics of particles such as dredged sediment of variable size discharged into cross flow are studied by a 3D numerical model, which is developed to model the particle-fluid two-phase flow. The Eulerian method with the modified k-ε parameterization of turbulence for the fluid phase is used to solve fluid phase, while a Lagrangian method for the solid phase (particles), both the processes are coupled through the momentum sources. In the model the wake turbulence induced by particles has been included as additional source term in the k-ε model; and the variable drift velocities of the particles are treated efficiently by the Lagrangian method in which the particles are tracked explicitly and the diffusion process is approximated by a random walk model. The hydrodynamic behavior of dumping a cloud of particles is governed by the total buoyancy of the cloud, the drag force on each particle and the velocity of cross-flow. The computed results show a roughly linear relationship between the displacement of the frontal position and the longitudinal width of the particle cloud. The particle size in the cloud and the velocity of cross flow dominate the flow behavior. The computed results are compared with the results of laboratory experiments and satisfactory agreement is obtained.     

Particle size effect on the saturation of methane hydrate in sediments – Constrained from experimental results

Except for those occurring at seafloor, most of natural gas hydrate form in sediments and are subject to the influence of sediment. Among these factors, the particle size effect on hydrate saturation level in sediment have been studied with a series of silica sands with various sizes, and the results obtained clearly indicate that particle size does play an important role in affecting the saturation level of hydrate in sediments. The proton relaxation times of water confined in the same series of silica sands, which were determined with NMR measurement, show logarithmic relationship with particle size. By comprehensive consideration of the results of hydrate saturation and water proton relaxation times, the particle size effect observed is tentatively explained by the water availability for hydrate formation in sediments.     

Particle flux through the Huanghai Sea cold water mass

Settling particulate matter （SPM） was collected by using sediment traps at four stations in a survey section from Qingdao to Cheju-do, across the Huanghai Sea cold water mass （HSCWM）, in August 2002. The sediment traps were planted in three layers： the upper layer of the thermocline （ULT） above the HSCWM, the lower layer of the thermocline （LLT）, and the bottom layer of water column （BL）. To determine the particle flux, the contents of organic carbon （POC）, organic nitrogen （PON）, total carbon （PC）, and total phosphorous （PP） in SPM were analyzed, and two flux models （Ⅰ and Ⅱ） were improved to calculate the resuspension ratio, with an assumption in Model Ⅰ that the vertical flux of SPM in the LLT equals the net vertical flux of SPM in the whole water column. An X value, i.e., the fraction of the resuspension flux originating from the surficial sediments nearby the sampling station, was deduced from Model Ⅰ to estimate the contribution of lateral currents to the total resuspension flux. The results showed that inorganic particles, fecal pellets, and miscellaneous aggregates were the major types of SPM in the HSCWM, and the contents of POC, PON, PC, and PP all decreased with water depth. A great deal of fecal pellets found in the LLT indicates that the main space producing biogenic SPM is the thermocline, and especially the LLT, where the C/N ratio is lower than that in the ULT. The resuspension ratios, 90%-96% among stations, imply strong impact ofresuspension on particle flux in the BL. These values were not significantly different between the two flux models, suggesting that the hypothesis in Model Ⅰ that the flux in the LLT equaling the net flux to the bottom is acceptable for shallow waters with stratification like the HSCWM. The POC export ratio from the HSCWM ranges from 35% to 68%. It benefits from the short sinking distance in shallow water. The upwelling in the HSCWM enhanced the POC flux through the water mass, and the lateral currents provides up to being greater than 50% ofresuspension flux in the BL according to evaluation of the X value.     

Particle Swarm-Based Translation Control for Immersed Tunnel Element in the Hong Kong–Zhuhai–Macao Bridge Project

Immersed tunnel is an important part of the Hong Kong–Zhuhai–Macao Bridge(HZMB) project. In immersed tunnel floating, translation which includes straight and transverse movements is the main working mode. To decide the magnitude and direction of the towing force for each tug, a particle swarm-based translation control method is presented for non-power immersed tunnel element. A sort of linear weighted logarithmic function is exploited to avoid weak subgoals. In simulation, the particle swarm-based control method is evaluated and compared with traditional empirical method in the case of the HZMB project. Simulation results show that the presented method delivers performance improvement in terms of the enhanced surplus towing force.     

Calculation of electric conductivity of water of the Aral Sea and correction of the sound salinity of 2002–2009

The Aral Sea is an important water area both for monitoring and oceanological studies, because its salinity and salt composition strongly differ from the oceanic. We offer a semiempiric calculation method of electric conductivity and the coefficient of its temperature dependence k judging from the ionic composition of water. The properties of the solution are considered as the sum of properties of seven binary salts taken based on the ionic composition of the solution. The MgSO₄ concentration is thought to be the highest possible, which makes the salt concentration nearly unambiguous. In a salinity range of 46–120‰ and temperature range of 5–25°C (2002–2009), the standard deviation of the calculated and measured electric conductivity was 2.9%. To refine the calculation of salinity from electric conductivity measurements using the “oceanic” formula, we suggest its preliminary reduction to a constant temperature (20°C) using the measured or calculated coefficient k.     

Determination of Partial Factors of Breast Wall on Top of Sloping Breakwater

- By applying the theory of structural reliability, reliability analyses for the stability of a breast wall on the top of a sloping breakwater are carried out. Based on the analyses, the method for determining partial action / load factors and partial resistance factors of breast walls is expounded, and the design expressions with partial factors are given. The values of partial action / load factors and partial resistance factors are recommended preliminarily according to the computation for breast walls with typical cross-sections.     

Study of evolution forecast of the area of the Huanghe River mouth

From 1979 to 1989, the current Qingshuigou course of the Huanghe River formed a sub - delta which resembles a beak extending into the Laizhou Bay. It covers 618 km2 in area. To meet the needs of developing and constructing the Huanghe River Delta and under the presupposition of keeping the current course for 15-20 a, we forecast mainly by using the OM (1, 1) model that the front border of the sub-delta will be close to 119°30'E and its area will become 923 km2by the end of the year 2000. The Huanghe River will make land 760 km2 in area.     

Characteristics of satellite cloud maps of typhoon movement in midsummer of 1985

There were 8 typhoons over the northwestern Pacific Ocean in August of 1985. Their movement characteristics were mainly northward or recurvature northward. At the same time, a complex movement of 3 typhoons clustering was observed. In this paper, the typhoon movement tendency is studied by using satellite cloud maps. The westward and northward tendencies can be distinguished clearly. Based on this rule, typhoon movement can be forecasted 12-48 h before. Some characteristics models of the typhoon moving northward or recurving northward on the satellite cloud maps are also given in this paper.     

Analysis of state of the carbonate system of waters and variations of the content of organic carbon in bottom sediments of the Sevastopol bay in 1998–2005

On the basis of the experimental data accumulated in 1998–2005, we analyzed the space and time variations of the carbonate system of waters and the content of organic carbon in bottom sediments of the Sevastopol Bay. The intensity of gas exchange through the water-atmosphere interface was quantitatively estimated. It was shown that the partial pressure of carbon dioxide pCO₂ in waters of the bay became much higher for the period of observations. The maximum changes were observed in summer. They were especially pronounced for the bottom layer of waters. For the entire period of observations, the invasion of carbon dioxide CO₂ was predominant in the major part of the bay, and the content of organic carbon in the bottom sediments increased. The ability of waters in the bay to absorb CO₂ is explained by the synthesis of organic substances, which becomes possible due to the presence of the equivalent load of nutrients. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 2, pp. 57–67, March–April, 2008.     

Suppression of Wave-Excited Vibration of Offshore Platform by Use of Tuned Liquid Dampers

This paper describes experimenlal and theoretical investigations of Tuned Liquid Damper (TLD) characteristics tor suppressing the wave-excited structural vibration. The structural model lor the experiments is scaled according to a full size offshore platform by matching their dynamic properties. Rectangular TLDs of different sizes with partially filled liquid are examined. By observing the performance and behavior of TLDs through laboratory experiments, the study investigates the influence of a number of parameters, including container size, container shape, frequency ratio, and incident wave characteristics. In an analytical study, a mathematical model that describes the nonlinear behavior of liquid in TLD and the interaction of TLD and structure is prerequisite. The validity of the model is evaluated and simulating results can reasonably match the corresponding experimental results.     

Analysis of characteristics and mechanism of current system on the west coast of Guangdong of China in summer

On the basis of data of drifting bottles＇ tracks and the current measured in anchored stations, as well as temperature and salinity observed in cruise investigations and coastal stations, ADCP current data and AVHRR surface sea temperature （SST） data on the western coast of Guangdong, synthetic results of analysis showed that the coastal currents in the west of the mouth of the Zhujiang River were mainly westward in summer, which constituted the north branch of cyclonic gyre in the east of the Qiongzhou Straits. Part of its water flowed westward into the Beibu Gulf through the Qiongzhou Straits. The coastal current pattern was not identical with the traditional current system which flowed westward in the Qiongzhou Straits in winter and eastward in summer. The summertime＇s coastal current was always westward, maybe temporarily turning northeast only when the southwest wind was strong. The important characteristics of coastal current on the western coast of Guangdong, in the Qiongzhou Straits and in the north of the Beibu Gulf were analyzed and their mechanisms also were explained.     

The computation of maximum wind speeds of typhoon

-At present, it is still difficult to obtain an accurate maximum wind speed of typhoon with modern means,such as satellite survey , radar tracing and airplane reconnaissance. The performance of statistical equation established with observational maximum wind speed and the central pressure of typhoon is unstable ,and it is unreliable in operational use. Therefore a general pressure field model of typhoon is introduced in this paper based on atmospheric motion equations and formulas are derived for computing the maximum wind speed around typhoon center over sea surface . The theoretical curves derived from these formulas are in good agreement with those using the statistic empirical curves of typhoon pressure-wind relations over the western Pacific. Tests were conducted for typhoons which occurred in 1973 and in 1983 and the strongest typhoons selected each year during 1970 and 1978,the results were satisfactory. Meanwhile the analyses of computing results showed that the effect of Coriolis force could be     

Measurement of nuclides of uranium and thorium series of disequilibrium using γ-spectroscopy

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒａｄｉｏｎｕｃｌｉｄｅｓｏｆｎａｔｕｒａｌｕｒａｎｉｕｍａｎｄｔｈｏｒｉｕｍｓｅｒｉｅｓｃａｎｂｅｕｓｅｄｔｏｔｒａｃｅｍａｒｉｎｅｐｒｏ ｃｅｓｓｏｆｖａｒｉｏｕｓｔｅｍｐｏｒａｌａｎｄｓｐａｔｉａｌｓｃａｌｅａｎｄｐｒｏｐｅｒｔｉｅｓｔｈａｔｐｒｏｖｉｄｅｐｌｅｎｔｉｆｕｌｉｎｆｏｒｍａｔｉｏｎａｂｏｕｔｐｈｙｓｉｃｓ,ｃｈｅｍｉｓｔｒｙ ,ｇｅｏｓｃｉｅｎｃｅａｎｄｂｉｏｌｏｇｙｏｆｏｃｅａｎｂｅｃａｕｓｅｔｈｅｙｈａｖｅｄｉｆｆｅｒｅｎｔｃｈｅｍｉｃａｌｐｒｏ…     

Simulation model of SAR remote sensing of turbulent wake of semi-elliptical submerged body

1 IntroductionThe study of SAR remote sensing of surface wake of a semi-elliptical submerged body is of great importance actually in the ocean. The dynamics and the SAR remote sensing mechanism of this wake are very complicated. Numerous researches (Bergmann et al., 1958; Miles, 1968a,b; Huppert and Miles, 1969; Bon-neton et al., 1993) indicate that in the ocean the imagery and dynamics of this wake are quite different when a semi-elliptical submerged body moves horizontally at high speed …     

Regional geomorphology of the continental slope of NW India: Delineation of the signatures of deep‐seated structures

Geomorphological features (derived from 16,000 lkm of echo‐sounding and bathymetric data) and deep‐seated tectonic structures of the continental margin off NW India are presented. The shelf break over the entire region occurs between 80 to 154 m water depth, and adjacent to Saurashtra and Bombay High the depth and orientation of the shelf edge show marked variations. The boundary of the slope is shallower in the northern portion (about 1450 m in the vicinity of the Indus) than in the southern region (2900 m off Bombay).

The steep slope off the Gulf of Kachchh has relatively smooth physiography due to higher input of fluvial sediment and burial of structures. The gentler slope off Saurashtra and the Bombay High area has numerous complex features, the most prominent among them being benches at depths of 180–230 m (width 2–10 km) and 650–780 m and a series of bathymetric highs and lows. Slope breaks are also observed between 400 and 600 m off Bombay and between 560 and 960 m off Saurashtra. These features are surface manifestations of the anticlinal features extending along the shelf in this region. Unevenness (order of 100–300 m) due to slumping is also observed at the base of the slope.

Based on the correlation between tectonic structures of this area and these subphysiographic features, extension of the Saurashtra Anticline onto the slope, a new strike slip fault (the southern boundary fault of Narmada graben) and an along‐shelf anticlinal structure off Saurashtra are delineated.     

Beta Distribution of Surface Elevation of Random Waves

A probability density function (PDF) is derived of beta distribution with both λ3 (skewness) and λ4 (kurtosis) as parameters for weakly nonlinear wave surface elevation by use of a method recently proposed by Srokosz. This PDF not only has a simpler form than the well-known Gram-Charlier Series PDF derived by Longuet-Higgins. but also overcomes an obvious shortcoming of the latter that when the series is unsuitably truncated, the resulting PDF is locally negative. To test the derived beta PDF, laboratorial experiments of wind waves are conducted. The experimental data indicate that the theoretical requirements of the parameters in the beta PDF are fulfilled. The experimental results show that the present PDF is in better agreement with the measured data than the beta PDF only including parameter λ3, and also than the Gram-Charlier Series PDF truncated up to the term of H6.