Oil spills continue to generate various issues and concerns regarding their effect and behavior in the marine environment,owing to the related potential for detrimental environmental,economic and social implications.I...Oil spills continue to generate various issues and concerns regarding their effect and behavior in the marine environment,owing to the related potential for detrimental environmental,economic and social implications.It is essential to have a solid understanding of the ways in which oil interacts with the water and the coastal ecosystems that are located nearby.This study proposes a simplified model for predicting the plume-like transport behavior of heavy Bunker C fuel oil discharging downward from an acutely-angled broken pipeline located on the water surface.The results show that the spill overall profile is articulated in three major flow areas.The first,is the source field,i.e.,a region near the origin of the initial jet,followed by the intermediate or transport field,namely,the region where the jet oil flow transitions into an underwater oil plume flow and starts to move horizontally,and finally,the far-field,where the oil re-surface and spreads onto the shore at a significant distance from the spill site.The behavior of the oil in the intermediate field is investigated using a simplified injection-type oil spill model capable of mimicking the undersea trapping and lateral migration of an oil plume originating from a negatively buoyant jet spill.A rectangular domain with proper boundary conditions is used to implement the model.The Projection approach is used to discretize a modified version of the Navier-Stokes equations in two dimensions.A benchmark fluid flow issue is used to verify the model and the results indicate a reasonable relationship between specific gravity and depth as well as agreement with the aerial data and a vertical temperature profile plot.展开更多
The turbulence mechanism plays an important part in the mixing process and momentum transfer of turbulence. A three-dimensional Prandtl mixing length tidal model has been developed to simulate tidal flows and water qu...The turbulence mechanism plays an important part in the mixing process and momentum transfer of turbulence. A three-dimensional Prandtl mixing length tidal model has been developed to simulate tidal flows and water quality. The eddy viscosities and diffusivities are computed from the Prandtl mixing length model. In order to model the water quality of an estuary or coastal area many interdependent processes need to be simulated. These may be conveniently separated into three main groups: transport and mixing processes, biochemical interaction of water quality variables and the utilization and re-cycling of nutrients by living matter. The model simulates full oxygen and nutrient balance, primary productivity and the transport, reaction mechanism and fate of pollutants over tidal time-scales. The model is applied to numerical simulation of tidal flows and water quality in Dalian Bay. The model has been calibrated against a limited data set of historical water quality observations and in general demonstrates excellent agreement with all available data.展开更多
In the southwestern Yellow Sea there is a low-salinity and turbid coastal water,the Subei Coastal Water（SCW）.The origins of freshwater contents and thus the dissolved terrigenous nutrients in the SCW have been debat...In the southwestern Yellow Sea there is a low-salinity and turbid coastal water,the Subei Coastal Water（SCW）.The origins of freshwater contents and thus the dissolved terrigenous nutrients in the SCW have been debated for decades.In this study,we used a well-validated numerical model to quantify the contributions of multiple rivers,i.e.,the Changjiang River in the south and the multiple Subei local rivers（SLRs） in the north,in forming this yearround low-salinity coastal water.It is found that the freshwater contents in the SCW is dominated by the Changjiang River south of 33.5°N,by the SLRs north of 34.5°N,and by both sources in 33.5°–34.5°N.Overall,the Changjiang River contributes ~70% in the dry season and ~80% in the wet season of the total freshwater contents in the SCW,respectively.Dynamics driving the Changjiang River Plume to flow northward is the tidal residual current,which can even overwhelm the wind effects in winter seasons.The residual currents turn offshore near the Old Yellow River Delta（OYRD） by the collision of the two tidal wave systems,which transport the freshwater from both sources into the interior Yellow Sea.Water age experiments show that it takes 50–150 d for the Changjiang River Plume to reach the SCW in the spring and summer seasons,thus there is a 2-month lag between the maximum freshwater content in SCW and the peak Changjiang River discharge.In the winter and autumn seasons,the low salinity in inner SCW is the remnant Changjiang River diluted water arrived in the previous seasons.展开更多
The hydrodynamics and water quality in Hakata Bay, Japan are strongly affected by the seasonal variations in both the gravitational circulation and the stratification in the bay. The three\|dimensional hydrodynamics ...The hydrodynamics and water quality in Hakata Bay, Japan are strongly affected by the seasonal variations in both the gravitational circulation and the stratification in the bay. The three\|dimensional hydrodynamics and water quality model has been developed to simulate the long\|term transport and fate of pollutants in the system. The model is unique in that it completely integrates the refined modelling of the hydrodynamics, biochemical reactions and the ecosystem in the coastal waters. It is a 3\|dimensional segmented model which is capable of resolving mean daily variations in all the parameters relevant to pollution control. It predicts daily fluctuations in the oxygen content at different depths in water throughout the year. It takes into account transport and settling of pollutant particles. It predicts light penetration from computed turbidity variations. It includes interactions between the ecosystem and water quality through nutrient cycling and photosynthesis. The model has been calibrated well against the data set of historical water quality observations in Hakata Bay.展开更多
A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sedimen...A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.展开更多
Surplus production models(SPMs)are among the simplest and most widely used fishery stock assessment models.The catch-effort data analysis(CEDA)and a surplus production model incorporating covariates(ASPIC)are software...Surplus production models(SPMs)are among the simplest and most widely used fishery stock assessment models.The catch-effort data analysis(CEDA)and a surplus production model incorporating covariates(ASPIC)are softwares for analyzing fishery catch and fishing effort data using nonequilibrium SPMs.In China Fishery Statistical Yearbook,annual fishery production and fishing effort data of the Yellow Sea,Bohai Sea,East China Sea,and South China Sea have been published from 1979 till present.Using its catch and fishing effort data from 1980 to 2018,we apply the CEDA and ASPIC to evaluate fishery resources in Chinese coastal waters.The results show that the total maximum sustainable yield(MSY)estimate of the four China seas is 10.05-10.83 million tons,approximately equal to the marine fishery catch(10.44 million tons)reported in 2018.It can be concluded that China’s coastal fishery resources are currently fully exploited and must be protected with a precautionary approach.Both softwares produced similar results;however,the CEDA had a much higher R2 value(above 0.9)than ASPIC(about 0.2),indicating that CEDA can better fit the data and therefore is more suitable for analyzing the fishery resources in the coastal waters of China.展开更多
The growth rate of the hyalid amphipod Hyale perieri was studied on the bases of Ikeda'sgrowth model which is based on the inter moult period (IP) and moult increament (△BL). To apply this approach, laboratory ex...The growth rate of the hyalid amphipod Hyale perieri was studied on the bases of Ikeda'sgrowth model which is based on the inter moult period (IP) and moult increament (△BL). To apply this approach, laboratory experiments were carried out at three temperatures regimes (15℃, 20℃, 25℃ ) to gain accurate data of IP and BL. The total number of specimens used in this study was 86 at 15℃ , 24 at 20℃ and 70 at 25℃. The number of flagellar segments of both antennae of the Hyale perieri could not be used as an index of growth (instar criterion). The obtained results indicated that, the predicted IP of the specimens was inversely related to temperature and in good agreement with the observed values at the experimental temperatures. IP data obtained from laboratory-reared specimes are combined with ABL data to establish a growth model for Hyale perieri from its release from the mar-supium (1.64 mm BL ) to the maximum size (12.67 mm BL) as a function of temperature. The maximum numbers of consecutive moults recorded during the experiment were 13 moults (14 instar) at 15℃, 14 moults (15 instar) at 20℃ and 12 moults (13 instar) at 25℃ . The predicted life span for BL = 12.67 mm (moult 13) was 203.82 d at 15t, for BL = 11.75 mm (moult 14) was 138.94 d at 20℃ and for BL = 8.65 mm (moult 12) was 75.40 d at 25℃ respectively, thus confirming that the life span of the species is inversely proportional to temperature. Within the experimental temperatures tested, the optimum temperature for the growth of the species was 20℃.展开更多
Seagrass meadows are generally diverse in China and have become important ecosystem with essential functions.However,the seagrass distribution across the seawaters of China has not been evaluated,and the magnitude and...Seagrass meadows are generally diverse in China and have become important ecosystem with essential functions.However,the seagrass distribution across the seawaters of China has not been evaluated,and the magnitude and direction of changes in seagrass meadows remain unclear.This study aimed to provide a nationwide seagrass distribution map and explore the dynamic changes in seagrass population under global climate change.Simulation studies were performed using the modeling software MaxEnt with 58961 occurrence records and 27 marine environmental variables to predict the potential distribution of seagrasses and calculate the area.Seven environmental variables were excluded from the modeling processes based on a correlation analysis to ensure predicted suitability.The predicted area was 790.09 km^(2),which is much larger than the known seagrass distribution in China(87.65 km^(2)).By 2100,the suitable habitat of seagrass will shift northwest and increase to 923.62 km2.Models of the sum of the individual family under-pre-dicted the national distribution of seagrasses and consistently showed a downward trend in the future.Out of all environmental vari-ables,physical parameters(e.g.,depth,land distance,and sea surface temperature)contributed the most in predicting seagrass distri-butions,and nutrients(e.g.,nitrate,phosphate)ranked among the key influential predictors for habitat suitability in our study area.This study is the first effort to fill a gap in understanding the distribution of seagrasses in China.Further studies using modeling and biological/ecological approaches are warranted.展开更多
A new model for the remote sensing of absorption coefficients of phytoplankton aph (λ) in oceanic and coastal waters is developed and tested with SeaWiFS and MODIS-Aqua data. The model is derived from a rela-tionship...A new model for the remote sensing of absorption coefficients of phytoplankton aph (λ) in oceanic and coastal waters is developed and tested with SeaWiFS and MODIS-Aqua data. The model is derived from a rela-tionship of the remote sensing reflectance ratio Rrs (670)/Rrs (490) and aph (490) and aph (670) (from large in-situ data sets). When compared with over 470 independent in-situ data sets, the model provides accurate retrievals of the aph (λ) across the visible spectrum, with mean relative error less than 8%, slope close to unity and R2 greater than 0.8. Further comparison of the SeaWiFS-derived aph (λ) with in-situ aph (λ) values gives similar and consistent results. The model when used for analysis of MODIS-Aqua imagery, provides more realistic values of the phytoplankton absorption coefficients capturing spatial structures of the massive algal blooms in surface waters of the Arabian Sea. These results demonstrate that the new algorithm works well for both the coastal and open ocean waters observed and suggest a potential of using remote sensing to provide knowledge on the shape of phytoplankton absorption spectra that are a requirement in many inverse models to estimate phytoplankton pigment concentrations and for input into bio-optical models that predict carbon fixation rates for the global ocean.展开更多
The prediction of water temperature and salinity in coastal areas is one of the essential tasks in water quality control and management. This paper takes a refined forecasting model of water temperature and salinity i...The prediction of water temperature and salinity in coastal areas is one of the essential tasks in water quality control and management. This paper takes a refined forecasting model of water temperature and salinity in coastal areas as a basic target. Based on the Navier-Stokes equation and k-epsilon turbulence model, taking the characteristics of coastal areas into account, a refined model for water temperature and salinity in coastal areas has been developed to simulate the seasonal variations of water temperature and salinity fields in the Hakata Bay, Japan. The model takes into account the effects of a variety of hydrodynamic and meteorological factors on water temperature and salinity. It predicts daily fluctuations in water temperature and salinity at different depths throughout the year. The model has been calibrated well against the data set of historical water temperature and salinity observations in the Hakata Bay, Japan.展开更多
Based on the evolution equation for water waves, a mathematical model for wave propaga tion in large mild - slope areas is derived. The model is solved by the finite difference method with the staggered grid system. ...Based on the evolution equation for water waves, a mathematical model for wave propaga tion in large mild - slope areas is derived. The model is solved by the finite difference method with the staggered grid system. The computational results are in good agreement with experimental data and show that the model can obtain better results with relatively coarser grids. The model can be used to simulate water wave propagation in large coastal areas and can be efficiently solved without much programming effort.展开更多
The water quality in Victoria Harbour.Hong Kong is dominated by strong seasonal effects resulting from the variation in freshwater discharge into the Pearl Estuary.The quasi-three-dimensional water quality model has b...The water quality in Victoria Harbour.Hong Kong is dominated by strong seasonal effects resulting from the variation in freshwater discharge into the Pearl Estuary.The quasi-three-dimensional water quality model has been developed to simulate the variations in water quality and the ecosystem in the harbour.The model is unique in that it completely integrates the refined modelling of the hydrodynamics,biochemical reactions and the ecosystem in the harbour.It is a quasi-three-dimensional segmented model which is capable of resolving mean daily variations in all the parameters relevant to pollution control.It predicts daily fluctuations in the oxygen content at different depths in water throughout the year.It takes into account transport and settling of pollutant particles.It predicts light penetration from computed turbidity variations.It includes interactions between the ecosystem and water quality,through nutrient cycling and photosynthesis.The model has been calibrated well against the data set of historical water quality observations.展开更多
The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author wi...The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author with his research group have been summarized. Water modeling was used to investigate the fluid flow and mixing characteristics in the bath of an 18 t AOD vessel, as well as the 'back attack' action of gas jets and its effects on the erosion and wear of the refractory lining, with sufficiently full kinematic similarity. The non rotating and rotating gas jets blown through two annular tuyeres, respectively of straight tube and spiral flat tube type, were employed in the experiments. The geometric similarity ratio between the model and its prototype (including the straight tube type tuyeres) was 1:3. The influences of the gas flow rate, the angle included between the two tuyeres and other operating parameters, and the suitability of the spiral tuyere as a practical application, were examined. These latest studies have clearly and successfully brought to light the fluid flow and mixing characteristics in the bath and the overall features of the back attack phenomena of gas jets during the blowing, and have offered a better understanding of the refining process. Besides, mathematical modeling for the refining process of stainless steel was carried out and a new mathematical model of the process was proposed and developed. The model performs the rate calculations of the refining and the mass and heat balances of the system. Also, the effects of the operating factors, including adding the slag materials, crop ends, and scrap, and alloy agents; the non isothermal conditions; the changes in the amounts of metal and slag during the refining; and other factors were all considered. The model was used to deal with and analyze the austenitic stainless steel making (including ultra low carbon steel) and was tested on data of 32 heats obtained in producing 304 grade steel in an 18 t AOD vessel. The changes in the bath composition and temperature during the refining process with time can be accurately predicted using this model. The model can provide some very useful information and a reliable basis for optimizing the process practice of the refining of stainless steel and control of the process in real time and online.展开更多
Tunnel water inrush is one of the common geological disasters in the underground engineering construction.In order to effectively evaluate and control the occurrence of water inrush,the risk assessment model of tunnel...Tunnel water inrush is one of the common geological disasters in the underground engineering construction.In order to effectively evaluate and control the occurrence of water inrush,the risk assessment model of tunnel water inrush was proposed based on improved attribute mathematical theory.The trigonometric functions were adopted to optimize the attribute mathematical theory,avoiding the influence of mutation points and linear variation zones in traditional linear measurement functions on the accuracy of the model.Based on comprehensive analysis of various factors,five parameters were selected as the evaluation indicators for the model,including tunnel head pressure,permeability coefficient of surrounding rock,crushing degree of surrounding rock,relative angle of joint plane and tunnel section size,under the principle of dimension rationality,independence,directness and quantification.The indicator classifications were determined.The links among measured data were analyzed in detail,and the objective weight of each indicator was determined by using similar weight method.Thereby the tunnel water inrush risk assessment model is established and applied in four target segments of two different tunnels in engineering.The evaluation results and the actual excavation data agree well,which indicates that the model is of high credibility and feasibility.展开更多
Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products （SMP） during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium...Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products （SMP） during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium were fed with different acetate loadings for the determination of SMP formation. Using numerically simulated and measured parameters, the theoretical model was developed according to the substrate and biomass balance. The results of this model matched the measured data better for higher SMP formation but did not fit well when SMP formation was lower. In order to better simulate the reality and overcome the difficulties of measuring the kinetic parameters, a simpler empirical model was also developed. In this model, SMP formation was expressed as a function of fed organic loadings and the depth of the medium, and a much better fit was obtained.展开更多
Groundwater resources occur in a multi aquifer system in the alluvial coastal plain near Beihai, China. The aquifers receive recharge from precipitation, canal and reservoir infiltration, and discharge through subter...Groundwater resources occur in a multi aquifer system in the alluvial coastal plain near Beihai, China. The aquifers receive recharge from precipitation, canal and reservoir infiltration, and discharge through subterranean drainage into the sea and through artificial pumping. A quasi three dimensional finite element model has been used to simulate the spatial and temporal distribution of groundwater levels in the aquifers. Various input parameters were considered in the simulation model. A linear optimization model has been developed for groundwater development within the coastal aquifers. The objective function of the model is to maximize the total groundwater pumpage from the confined aquifer. The control of sea water intrusion is examined by the restriction of the water levels at points along the coast and of the pumping rates in coastal management cells. The response matrix used in the optimization model was generated from the simulation model by forecasting drawdown produced by pumping at a unit impulse discharge. Groundwater development can be primarily optimized by the alteration of the pumping rates of the existing wells.展开更多
Secchi depth(SD,m)is a direct and intuitive measure of water's transparency,which is also an indicator of water quality.In 2015,a semi-analytical model was developed to derive SD from remote sensing reflectance,th...Secchi depth(SD,m)is a direct and intuitive measure of water's transparency,which is also an indicator of water quality.In 2015,a semi-analytical model was developed to derive SD from remote sensing reflectance,thus able to provide maps of water's transparency in satellite images.Here an in-situ dataset(338 stations)is used to evaluate its potential ability to monitor water quality in the coastal and estuarine waters,with measurements covering the Zhujiang(Pearl)River Estuary,the Yellow Sea and the East China Sea where measured SD values span a range of 0.2–21.0 m.As a preliminary validation result,according to the whole dataset,the unbiased percent difference(UPD)between estimated and measured SD is 23.3%(N=338,R^2=0.89),with about 60%of stations in the dataset having relative difference(RD)≤20%,over 80%of stations having RD≤40%.Furthermore,by excluding the field data which with relatively larger uncertainties,the semi-analytical model yielded the UPD of 17.7%(N=132,R^2=0.92)with SD range of 0.2–11.0 m.In addition,the semi-analytical model was applied to Landsat-8 images in the Zhujiang River Estuary,and retrieved high-quality mapping and reliable spatial-temporal patterns of water clarity.Taking into account the uncertainties associated with both field measurements and satellite data processing,and that there were no tuning of the semi-analytical model for these regions,these findings indicate highly robust retrieval of SD from spectral techniques for such turbid coastal and estuarine waters.The results suggest it is now possible to routinely monitor coastal water transparency or visibility at high-spatial resolutions from measurements,like Landsat-8 and Sentinel-2 and newly launched Gaofen-5.展开更多
Foam injection is a promising solution for control of mobility in oil and gas field exploration and development,including enhanced oil recovery,matrix-acidization treatments,contaminated-aquifer remediation and gas le...Foam injection is a promising solution for control of mobility in oil and gas field exploration and development,including enhanced oil recovery,matrix-acidization treatments,contaminated-aquifer remediation and gas leakage prevention.This study presents a numerical investigation of foam behavior in a porous medium.Fractional flow method is applied to describe steady-state foam displacement in the entrance region.In this model,foam flow for the cases of excluding and including capillary pressure and for two types of gas,nitrogen(N2)and carbon dioxide(CO2)are investigated.Effects of pertinent parameters are also verified.Results indicate that the foam texture strongly governs foam flow in porous media.Required entrance region may be quite different for foam texture to accede local equilibrium,depending on the case and physical properties that are used.According to the fact that the aim of foaming of injected gas is to reduce gas mobility,results show that CO2 is a more proper injecting gas than N2.There are also some ideas presented here on improvement in foam displacement process.This study will provide an insight into future laboratory research and development of full-field foam flow in a porous medium.展开更多
Based on the tensor analysis of water-sediment two-phase how, the basic model equations for clear water flow and sediment-laden flow are deduced in the general curve coordinates for natural water variable-density turb...Based on the tensor analysis of water-sediment two-phase how, the basic model equations for clear water flow and sediment-laden flow are deduced in the general curve coordinates for natural water variable-density turbulent how. Furthermore, corresponding boundary conditions are also presented in connection with the composition and movement of non-uniform bed material. The theoretical results are applied to the calculation of the float open caisson in the construction period and good results are obtained.展开更多
The geothermal waters of south hot spring, small hot spring and Qiaokouba in Chongqing, are all part of the south hot spring geothermal water system. Exploitation has caused a decline in the water levels of the south ...The geothermal waters of south hot spring, small hot spring and Qiaokouba in Chongqing, are all part of the south hot spring geothermal water system. Exploitation has caused a decline in the water levels of the south and small hot springs, which have not flowed naturally for 15 years. Now, bores pump geothermal water to the springs. If the water level drops below the elevation of the rivers, river-water will replenish the geothermal water, destroying this resource. It is therefore an urgent task to model the geothermal water system, to enable sustainable development and continued use of the geothermal water in Qiaokouba. A numerical simulation of the geothermal water system was adopted and a quantitative study on the planning scheme was carried out. A mathematical model was set up to simulate the whole geothermal water system, based on data from the research sites. The model determined the maximum sustainable water yield in Qiaokouba and the two hot springs, and the south hot spring and small hot spring sustainable yields are 1 100 m^3/d and 700 m^3/d from 2006 to 2010, 1 300 m^3/d and 1 000 m^3/d from 2011 to 2015, and 1 500 m^3/d and 1 200 m^3/d from 2016 to 2036. The maximum exploitable yield is 3 300 m^3/d from 2006 to 2036 in Qiaokouba. The model supplies a basis to adequately exploit and effectively protect the geothermal water resources, and to continue to develop the geothermal water as a tourist attraction in Chongqing.展开更多
文摘Oil spills continue to generate various issues and concerns regarding their effect and behavior in the marine environment,owing to the related potential for detrimental environmental,economic and social implications.It is essential to have a solid understanding of the ways in which oil interacts with the water and the coastal ecosystems that are located nearby.This study proposes a simplified model for predicting the plume-like transport behavior of heavy Bunker C fuel oil discharging downward from an acutely-angled broken pipeline located on the water surface.The results show that the spill overall profile is articulated in three major flow areas.The first,is the source field,i.e.,a region near the origin of the initial jet,followed by the intermediate or transport field,namely,the region where the jet oil flow transitions into an underwater oil plume flow and starts to move horizontally,and finally,the far-field,where the oil re-surface and spreads onto the shore at a significant distance from the spill site.The behavior of the oil in the intermediate field is investigated using a simplified injection-type oil spill model capable of mimicking the undersea trapping and lateral migration of an oil plume originating from a negatively buoyant jet spill.A rectangular domain with proper boundary conditions is used to implement the model.The Projection approach is used to discretize a modified version of the Navier-Stokes equations in two dimensions.A benchmark fluid flow issue is used to verify the model and the results indicate a reasonable relationship between specific gravity and depth as well as agreement with the aerial data and a vertical temperature profile plot.
基金The project is supported by The National Natural Science Foundation of China
文摘The turbulence mechanism plays an important part in the mixing process and momentum transfer of turbulence. A three-dimensional Prandtl mixing length tidal model has been developed to simulate tidal flows and water quality. The eddy viscosities and diffusivities are computed from the Prandtl mixing length model. In order to model the water quality of an estuary or coastal area many interdependent processes need to be simulated. These may be conveniently separated into three main groups: transport and mixing processes, biochemical interaction of water quality variables and the utilization and re-cycling of nutrients by living matter. The model simulates full oxygen and nutrient balance, primary productivity and the transport, reaction mechanism and fate of pollutants over tidal time-scales. The model is applied to numerical simulation of tidal flows and water quality in Dalian Bay. The model has been calibrated against a limited data set of historical water quality observations and in general demonstrates excellent agreement with all available data.
基金The National Natural Science Foundation of China under contract No.41576088the National Key Research and Development Program of China under contract No.2016YFC1402202the research foundation of State Key Laboratory of Estuarine and Coastal Research under contract No.2015KYYW04
文摘In the southwestern Yellow Sea there is a low-salinity and turbid coastal water,the Subei Coastal Water（SCW）.The origins of freshwater contents and thus the dissolved terrigenous nutrients in the SCW have been debated for decades.In this study,we used a well-validated numerical model to quantify the contributions of multiple rivers,i.e.,the Changjiang River in the south and the multiple Subei local rivers（SLRs） in the north,in forming this yearround low-salinity coastal water.It is found that the freshwater contents in the SCW is dominated by the Changjiang River south of 33.5°N,by the SLRs north of 34.5°N,and by both sources in 33.5°–34.5°N.Overall,the Changjiang River contributes ~70% in the dry season and ~80% in the wet season of the total freshwater contents in the SCW,respectively.Dynamics driving the Changjiang River Plume to flow northward is the tidal residual current,which can even overwhelm the wind effects in winter seasons.The residual currents turn offshore near the Old Yellow River Delta（OYRD） by the collision of the two tidal wave systems,which transport the freshwater from both sources into the interior Yellow Sea.Water age experiments show that it takes 50–150 d for the Changjiang River Plume to reach the SCW in the spring and summer seasons,thus there is a 2-month lag between the maximum freshwater content in SCW and the peak Changjiang River discharge.In the winter and autumn seasons,the low salinity in inner SCW is the remnant Changjiang River diluted water arrived in the previous seasons.
文摘The hydrodynamics and water quality in Hakata Bay, Japan are strongly affected by the seasonal variations in both the gravitational circulation and the stratification in the bay. The three\|dimensional hydrodynamics and water quality model has been developed to simulate the long\|term transport and fate of pollutants in the system. The model is unique in that it completely integrates the refined modelling of the hydrodynamics, biochemical reactions and the ecosystem in the coastal waters. It is a 3\|dimensional segmented model which is capable of resolving mean daily variations in all the parameters relevant to pollution control. It predicts daily fluctuations in the oxygen content at different depths in water throughout the year. It takes into account transport and settling of pollutant particles. It predicts light penetration from computed turbidity variations. It includes interactions between the ecosystem and water quality through nutrient cycling and photosynthesis. The model has been calibrated well against the data set of historical water quality observations in Hakata Bay.
基金financially supported by the Science Foundation of China University of Petroleum,Beijing(Grant Nos.2462015YQ0213 and 2462017BJB02)
文摘A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.
基金This study is supported by the project from the Food and Agriculture Organization of the United Nations(FAO)(No.GF.FIRFD.RA20403020400).
文摘Surplus production models(SPMs)are among the simplest and most widely used fishery stock assessment models.The catch-effort data analysis(CEDA)and a surplus production model incorporating covariates(ASPIC)are softwares for analyzing fishery catch and fishing effort data using nonequilibrium SPMs.In China Fishery Statistical Yearbook,annual fishery production and fishing effort data of the Yellow Sea,Bohai Sea,East China Sea,and South China Sea have been published from 1979 till present.Using its catch and fishing effort data from 1980 to 2018,we apply the CEDA and ASPIC to evaluate fishery resources in Chinese coastal waters.The results show that the total maximum sustainable yield(MSY)estimate of the four China seas is 10.05-10.83 million tons,approximately equal to the marine fishery catch(10.44 million tons)reported in 2018.It can be concluded that China’s coastal fishery resources are currently fully exploited and must be protected with a precautionary approach.Both softwares produced similar results;however,the CEDA had a much higher R2 value(above 0.9)than ASPIC(about 0.2),indicating that CEDA can better fit the data and therefore is more suitable for analyzing the fishery resources in the coastal waters of China.
文摘The growth rate of the hyalid amphipod Hyale perieri was studied on the bases of Ikeda'sgrowth model which is based on the inter moult period (IP) and moult increament (△BL). To apply this approach, laboratory experiments were carried out at three temperatures regimes (15℃, 20℃, 25℃ ) to gain accurate data of IP and BL. The total number of specimens used in this study was 86 at 15℃ , 24 at 20℃ and 70 at 25℃. The number of flagellar segments of both antennae of the Hyale perieri could not be used as an index of growth (instar criterion). The obtained results indicated that, the predicted IP of the specimens was inversely related to temperature and in good agreement with the observed values at the experimental temperatures. IP data obtained from laboratory-reared specimes are combined with ABL data to establish a growth model for Hyale perieri from its release from the mar-supium (1.64 mm BL ) to the maximum size (12.67 mm BL) as a function of temperature. The maximum numbers of consecutive moults recorded during the experiment were 13 moults (14 instar) at 15℃, 14 moults (15 instar) at 20℃ and 12 moults (13 instar) at 25℃ . The predicted life span for BL = 12.67 mm (moult 13) was 203.82 d at 15t, for BL = 11.75 mm (moult 14) was 138.94 d at 20℃ and for BL = 8.65 mm (moult 12) was 75.40 d at 25℃ respectively, thus confirming that the life span of the species is inversely proportional to temperature. Within the experimental temperatures tested, the optimum temperature for the growth of the species was 20℃.
基金supported by the National Key R&D Program of China(No.2019YFC1408405-02)the National Natural Science Foundation of China(No.6207070555)the Youth Foundation of the Shandong Academy of Sciences(No.2019QN0026).
文摘Seagrass meadows are generally diverse in China and have become important ecosystem with essential functions.However,the seagrass distribution across the seawaters of China has not been evaluated,and the magnitude and direction of changes in seagrass meadows remain unclear.This study aimed to provide a nationwide seagrass distribution map and explore the dynamic changes in seagrass population under global climate change.Simulation studies were performed using the modeling software MaxEnt with 58961 occurrence records and 27 marine environmental variables to predict the potential distribution of seagrasses and calculate the area.Seven environmental variables were excluded from the modeling processes based on a correlation analysis to ensure predicted suitability.The predicted area was 790.09 km^(2),which is much larger than the known seagrass distribution in China(87.65 km^(2)).By 2100,the suitable habitat of seagrass will shift northwest and increase to 923.62 km2.Models of the sum of the individual family under-pre-dicted the national distribution of seagrasses and consistently showed a downward trend in the future.Out of all environmental vari-ables,physical parameters(e.g.,depth,land distance,and sea surface temperature)contributed the most in predicting seagrass distri-butions,and nutrients(e.g.,nitrate,phosphate)ranked among the key influential predictors for habitat suitability in our study area.This study is the first effort to fill a gap in understanding the distribution of seagrasses in China.Further studies using modeling and biological/ecological approaches are warranted.
文摘A new model for the remote sensing of absorption coefficients of phytoplankton aph (λ) in oceanic and coastal waters is developed and tested with SeaWiFS and MODIS-Aqua data. The model is derived from a rela-tionship of the remote sensing reflectance ratio Rrs (670)/Rrs (490) and aph (490) and aph (670) (from large in-situ data sets). When compared with over 470 independent in-situ data sets, the model provides accurate retrievals of the aph (λ) across the visible spectrum, with mean relative error less than 8%, slope close to unity and R2 greater than 0.8. Further comparison of the SeaWiFS-derived aph (λ) with in-situ aph (λ) values gives similar and consistent results. The model when used for analysis of MODIS-Aqua imagery, provides more realistic values of the phytoplankton absorption coefficients capturing spatial structures of the massive algal blooms in surface waters of the Arabian Sea. These results demonstrate that the new algorithm works well for both the coastal and open ocean waters observed and suggest a potential of using remote sensing to provide knowledge on the shape of phytoplankton absorption spectra that are a requirement in many inverse models to estimate phytoplankton pigment concentrations and for input into bio-optical models that predict carbon fixation rates for the global ocean.
基金The project was financially supported by the National Natural Science Foundation of China(Grant No.59779023,No.59839330)
文摘The prediction of water temperature and salinity in coastal areas is one of the essential tasks in water quality control and management. This paper takes a refined forecasting model of water temperature and salinity in coastal areas as a basic target. Based on the Navier-Stokes equation and k-epsilon turbulence model, taking the characteristics of coastal areas into account, a refined model for water temperature and salinity in coastal areas has been developed to simulate the seasonal variations of water temperature and salinity fields in the Hakata Bay, Japan. The model takes into account the effects of a variety of hydrodynamic and meteorological factors on water temperature and salinity. It predicts daily fluctuations in water temperature and salinity at different depths throughout the year. The model has been calibrated well against the data set of historical water temperature and salinity observations in the Hakata Bay, Japan.
基金National Natural Science Foundation of China under contract No.59839330by ChinaPostdoctoral Science Foundation.
文摘Based on the evolution equation for water waves, a mathematical model for wave propaga tion in large mild - slope areas is derived. The model is solved by the finite difference method with the staggered grid system. The computational results are in good agreement with experimental data and show that the model can obtain better results with relatively coarser grids. The model can be used to simulate water wave propagation in large coastal areas and can be efficiently solved without much programming effort.
基金Project supported by the National Natural Science Foundation of China.
文摘The water quality in Victoria Harbour.Hong Kong is dominated by strong seasonal effects resulting from the variation in freshwater discharge into the Pearl Estuary.The quasi-three-dimensional water quality model has been developed to simulate the variations in water quality and the ecosystem in the harbour.The model is unique in that it completely integrates the refined modelling of the hydrodynamics,biochemical reactions and the ecosystem in the harbour.It is a quasi-three-dimensional segmented model which is capable of resolving mean daily variations in all the parameters relevant to pollution control.It predicts daily fluctuations in the oxygen content at different depths in water throughout the year.It takes into account transport and settling of pollutant particles.It predicts light penetration from computed turbidity variations.It includes interactions between the ecosystem and water quality,through nutrient cycling and photosynthesis.The model has been calibrated well against the data set of historical water quality observations.
文摘The available studies in the literature on physical and mathematical modeling of the argon oxygen decarburization (AOD) process of stainless steel have briefly been reviewed. The latest advances made by the author with his research group have been summarized. Water modeling was used to investigate the fluid flow and mixing characteristics in the bath of an 18 t AOD vessel, as well as the 'back attack' action of gas jets and its effects on the erosion and wear of the refractory lining, with sufficiently full kinematic similarity. The non rotating and rotating gas jets blown through two annular tuyeres, respectively of straight tube and spiral flat tube type, were employed in the experiments. The geometric similarity ratio between the model and its prototype (including the straight tube type tuyeres) was 1:3. The influences of the gas flow rate, the angle included between the two tuyeres and other operating parameters, and the suitability of the spiral tuyere as a practical application, were examined. These latest studies have clearly and successfully brought to light the fluid flow and mixing characteristics in the bath and the overall features of the back attack phenomena of gas jets during the blowing, and have offered a better understanding of the refining process. Besides, mathematical modeling for the refining process of stainless steel was carried out and a new mathematical model of the process was proposed and developed. The model performs the rate calculations of the refining and the mass and heat balances of the system. Also, the effects of the operating factors, including adding the slag materials, crop ends, and scrap, and alloy agents; the non isothermal conditions; the changes in the amounts of metal and slag during the refining; and other factors were all considered. The model was used to deal with and analyze the austenitic stainless steel making (including ultra low carbon steel) and was tested on data of 32 heats obtained in producing 304 grade steel in an 18 t AOD vessel. The changes in the bath composition and temperature during the refining process with time can be accurately predicted using this model. The model can provide some very useful information and a reliable basis for optimizing the process practice of the refining of stainless steel and control of the process in real time and online.
基金Project(2013CB036004) supported by National Basic Research Program(973)of ChinaProject(51378510) supported by National Natural Science Foundation of China
文摘Tunnel water inrush is one of the common geological disasters in the underground engineering construction.In order to effectively evaluate and control the occurrence of water inrush,the risk assessment model of tunnel water inrush was proposed based on improved attribute mathematical theory.The trigonometric functions were adopted to optimize the attribute mathematical theory,avoiding the influence of mutation points and linear variation zones in traditional linear measurement functions on the accuracy of the model.Based on comprehensive analysis of various factors,five parameters were selected as the evaluation indicators for the model,including tunnel head pressure,permeability coefficient of surrounding rock,crushing degree of surrounding rock,relative angle of joint plane and tunnel section size,under the principle of dimension rationality,independence,directness and quantification.The indicator classifications were determined.The links among measured data were analyzed in detail,and the objective weight of each indicator was determined by using similar weight method.Thereby the tunnel water inrush risk assessment model is established and applied in four target segments of two different tunnels in engineering.The evaluation results and the actual excavation data agree well,which indicates that the model is of high credibility and feasibility.
基金supported by the National Natural Science Foundation of China (Grant No. 50408026)
文摘Both a theoretical and an empirical model were developed for predicting the formation of soluble microbial products （SMP） during drinking water biofiltration. Four pilot-scale biofilters with ceramsite as the medium were fed with different acetate loadings for the determination of SMP formation. Using numerically simulated and measured parameters, the theoretical model was developed according to the substrate and biomass balance. The results of this model matched the measured data better for higher SMP formation but did not fit well when SMP formation was lower. In order to better simulate the reality and overcome the difficulties of measuring the kinetic parameters, a simpler empirical model was also developed. In this model, SMP formation was expressed as a function of fed organic loadings and the depth of the medium, and a much better fit was obtained.
基金This paper is partially supported by the Fund for Young Geologists in the Ministry of Geology and Mineral Resources of China(
文摘Groundwater resources occur in a multi aquifer system in the alluvial coastal plain near Beihai, China. The aquifers receive recharge from precipitation, canal and reservoir infiltration, and discharge through subterranean drainage into the sea and through artificial pumping. A quasi three dimensional finite element model has been used to simulate the spatial and temporal distribution of groundwater levels in the aquifers. Various input parameters were considered in the simulation model. A linear optimization model has been developed for groundwater development within the coastal aquifers. The objective function of the model is to maximize the total groundwater pumpage from the confined aquifer. The control of sea water intrusion is examined by the restriction of the water levels at points along the coast and of the pumping rates in coastal management cells. The response matrix used in the optimization model was generated from the simulation model by forecasting drawdown produced by pumping at a unit impulse discharge. Groundwater development can be primarily optimized by the alteration of the pumping rates of the existing wells.
基金The National Natural Science Foundation of China under contract No.61527810the Marine Science and Technology Fund from Director of South China Sea Branch+1 种基金State Oceanic Administration of China under contract No.180101the Key Laboratory Open Project Fund of Technology and Application for Safeguarding of Marine Rights and Interests,State Oceanic Administration of China under contract No.1720。
文摘Secchi depth(SD,m)is a direct and intuitive measure of water's transparency,which is also an indicator of water quality.In 2015,a semi-analytical model was developed to derive SD from remote sensing reflectance,thus able to provide maps of water's transparency in satellite images.Here an in-situ dataset(338 stations)is used to evaluate its potential ability to monitor water quality in the coastal and estuarine waters,with measurements covering the Zhujiang(Pearl)River Estuary,the Yellow Sea and the East China Sea where measured SD values span a range of 0.2–21.0 m.As a preliminary validation result,according to the whole dataset,the unbiased percent difference(UPD)between estimated and measured SD is 23.3%(N=338,R^2=0.89),with about 60%of stations in the dataset having relative difference(RD)≤20%,over 80%of stations having RD≤40%.Furthermore,by excluding the field data which with relatively larger uncertainties,the semi-analytical model yielded the UPD of 17.7%(N=132,R^2=0.92)with SD range of 0.2–11.0 m.In addition,the semi-analytical model was applied to Landsat-8 images in the Zhujiang River Estuary,and retrieved high-quality mapping and reliable spatial-temporal patterns of water clarity.Taking into account the uncertainties associated with both field measurements and satellite data processing,and that there were no tuning of the semi-analytical model for these regions,these findings indicate highly robust retrieval of SD from spectral techniques for such turbid coastal and estuarine waters.The results suggest it is now possible to routinely monitor coastal water transparency or visibility at high-spatial resolutions from measurements,like Landsat-8 and Sentinel-2 and newly launched Gaofen-5.
文摘Foam injection is a promising solution for control of mobility in oil and gas field exploration and development,including enhanced oil recovery,matrix-acidization treatments,contaminated-aquifer remediation and gas leakage prevention.This study presents a numerical investigation of foam behavior in a porous medium.Fractional flow method is applied to describe steady-state foam displacement in the entrance region.In this model,foam flow for the cases of excluding and including capillary pressure and for two types of gas,nitrogen(N2)and carbon dioxide(CO2)are investigated.Effects of pertinent parameters are also verified.Results indicate that the foam texture strongly governs foam flow in porous media.Required entrance region may be quite different for foam texture to accede local equilibrium,depending on the case and physical properties that are used.According to the fact that the aim of foaming of injected gas is to reduce gas mobility,results show that CO2 is a more proper injecting gas than N2.There are also some ideas presented here on improvement in foam displacement process.This study will provide an insight into future laboratory research and development of full-field foam flow in a porous medium.
文摘Based on the tensor analysis of water-sediment two-phase how, the basic model equations for clear water flow and sediment-laden flow are deduced in the general curve coordinates for natural water variable-density turbulent how. Furthermore, corresponding boundary conditions are also presented in connection with the composition and movement of non-uniform bed material. The theoretical results are applied to the calculation of the float open caisson in the construction period and good results are obtained.
文摘The geothermal waters of south hot spring, small hot spring and Qiaokouba in Chongqing, are all part of the south hot spring geothermal water system. Exploitation has caused a decline in the water levels of the south and small hot springs, which have not flowed naturally for 15 years. Now, bores pump geothermal water to the springs. If the water level drops below the elevation of the rivers, river-water will replenish the geothermal water, destroying this resource. It is therefore an urgent task to model the geothermal water system, to enable sustainable development and continued use of the geothermal water in Qiaokouba. A numerical simulation of the geothermal water system was adopted and a quantitative study on the planning scheme was carried out. A mathematical model was set up to simulate the whole geothermal water system, based on data from the research sites. The model determined the maximum sustainable water yield in Qiaokouba and the two hot springs, and the south hot spring and small hot spring sustainable yields are 1 100 m^3/d and 700 m^3/d from 2006 to 2010, 1 300 m^3/d and 1 000 m^3/d from 2011 to 2015, and 1 500 m^3/d and 1 200 m^3/d from 2016 to 2036. The maximum exploitable yield is 3 300 m^3/d from 2006 to 2036 in Qiaokouba. The model supplies a basis to adequately exploit and effectively protect the geothermal water resources, and to continue to develop the geothermal water as a tourist attraction in Chongqing.
