WorldWideScience

Sample records for model solids sediments

  1. Fluid-solid coupling model for studying wellbore instability in drilling of gas hydrate bearing sediments

    Institute of Scientific and Technical Information of China (English)

    程远方; 李令东; 崔青

    2013-01-01

    As the oil or gas exploration and development activities in deep and ultra-deep waters become more and more, encountering gas hydrate bearing sediments (HBS) is almost inevitable. The variation in temperature and pressure can destabilize gas hydrate in nearby formation around the borehole, which may reduce the strength of the formation and result in wellbore instability. A non-isothermal, transient, two-phase, and fluid-solid coupling mathematical model is proposed to simulate the complex stability performance of a wellbore drilled in HBS. In the model, the phase transition of hydrate dissociation, the heat exchange between drilling fluid and formation, the change of mechanical and petrophysical properties, the gas-water two-phase seepage, and its interaction with rock deformation are considered. A finite element simulator is developed, and the impact of drilling mud on wellbore instability in HBS is simulated. Results indicate that the re-duction in pressure and the increase in temperature of the drilling fluid can accelerate hydrate decomposition and lead to mechanical properties getting worse tremendously. The cohesion decreases by 25% when the hydrate totally dissociates in HBS. This easily causes the wellbore instability accordingly. In the first two hours after the formation is drilled, the regions of hydrate dissociation and wellbore instability extend quickly. Then, with the soaking time of drilling fluid increasing, the regions enlarge little. Choosing the low temperature drilling fluid and increasing the drilling mud pressure appropriately can benefit the wellbore stability of HBS. The established model turns out to be an efficient tool in numerical studies of the hydrate dissociation behavior and wellbore stability of HBS.

  2. FINAL REPORT - Mechanisms of CCl4 Retention and Slow Release in Model Porous Solids and Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Reid C. Miller; Dr. Brent M. Peyton

    2006-12-11

    connected by smaller openings. Except for peculiar behavior in the very early part of desorption experiments for one type of particles, the carbon tetrachloride desorption curves could be fit by a two-part model, employing a diffusion model for the bulk of the desorption, followed by a deactivation model as the mass adsorbed approached residual values. Simultaneous microbalance and gas chromatograph measurements were used to determine carbon tetrachloride and water desorption rates from silica particles initially containing both volatile components. Varying water to carbon tetrachloride ratios were loaded on two types of particles with different pore sizes, with water always loaded first. With water on the particles, pore volumes were significantly reduced. When compared at the same mass adsorbed values, total desorption rates consistently decreased with increasing water content. Total residual mass was found to be a strong function of initial water content, increasing nonlinearly from as initial water content increased from 0 % to 100 %. As expected, during the first few hours of all desorption rate experiments, the rates of carbon tetrachloride desorption were larger than for water. At low initial water contents, total desorption rates were controlled throughout by the carbon tetrachloride rates. For higher water contents, the water rates became larger than the carbon tetrachloride rates for at least some period of intermediate times, after the bulk of the carbon tetrachloride had been desorbed. Although the compositions of the residual mass have not been independently measured, there is evidence that both components were retained, but that water was the major component when there was significant initial water on the particles.

  3. Surface complexation modeling for predicting solid phase arsenic concentrations in the sediments of the Mississippi River Valley alluvial aquifer, Arkansas, USA

    Science.gov (United States)

    Sharif, M.S.U.; Davis, R.K.; Steele, K.F.; Kim, B.; Hays, P.D.; Kresse, T.M.; Fazio, J.A.

    2011-01-01

    The potential health impact of As in drinking water supply systems in the Mississippi River Valley alluvial aquifer in the state of Arkansas, USA is significant. In this context it is important to understand the occurrence, distribution and mobilization of As in the Mississippi River Valley alluvial aquifer. Application of surface complexation models (SCMs) to predict the sorption behavior of As and hydrous Fe oxides (HFO) in the laboratory has increased in the last decade. However, the application of SCMs to predict the sorption of As in natural sediments has not often been reported, and such applications are greatly constrained by the lack of site-specific model parameters. Attempts have been made to use SCMs considering a component additivity (CA) approach which accounts for relative abundances of pure phases in natural sediments, followed by the addition of SCM parameters individually for each phase. Although few reliable and internally consistent sorption databases related to HFO exist, the use of SCMs using laboratory-derived sorption databases to predict the mobility of As in natural sediments has increased. This study is an attempt to evaluate the ability of the SCMs using the geochemical code PHREEQC to predict solid phase As in the sediments of the Mississippi River Valley alluvial aquifer in Arkansas. The SCM option of the double-layer model (DLM) was simulated using ferrihydrite and goethite as sorbents quantified from chemical extractions, calculated surface-site densities, published surface properties, and published laboratory-derived sorption constants for the sorbents. The model results are satisfactory for shallow wells (10.6. m below ground surface), where the redox condition is relatively oxic or mildly suboxic. However, for the deep alluvial aquifer (21-36.6. m below ground surface) where the redox condition is suboxic to anoxic, the model results are unsatisfactory. ?? 2011 Elsevier Ltd.

  4. Community Sediment Transport Model

    Science.gov (United States)

    2007-01-01

    are used to determine that model results are consistent across compilers, platforms, and computer architectures , and to ensure that changes in code do...Mississippi State University: Bhate During the early months of this project, the focus was on understanding ROMS-CSTM model, architecture , and...Marchesiello, J.C. McWilliams, & K.D. Stolzenbach, 2007: Sediment transport modeling on Southern Californian shelves: A ROMS case study. Continental

  5. Solid sediment load history of the Zambezi Delta [rapid communication

    Science.gov (United States)

    Walford, H. L.; White, N. J.; Sydow, J. C.

    2005-09-01

    We calculate the solid sediment load history of the Zambezi River for the last 120 Ma (i.e. Middle Cretaceous-Recent times). Our starting point is a detailed grid of two-dimensional seismic reflection profiles, calibrated by well-log information. After conversion from two-way travel time to depth, we made simple assumptions about the compaction history in order to construct isochore maps of solid sediment load and yield as a function of geological time. Our results show that solid sediment load has varied by ˜1 order of magnitude over the last 120 Ma. There have been three periods of elevated flux. The first period occurred in Late Cretaceous times (90-65 Ma) and was synchronous with the rapid denudation of southern Africa recognised by, for example, apatite fission track modelling. The second period occurred in Oligocene times (34-24 Ma) during proposed rapid regional uplift of Southern Africa. The youngest phase of elevated flux started in Late Miocene times (10 Ma) and has continued to increase rapidly through to the present day. A large proportion of this increase can be attributed to a doubling of the size of the Zambezi catchment during the Pliocene. At other times, we suggest that load variations can be used to bound the uplift history of the region, which encompasses the catchment. Finally, changes in the shape of the Zambezi Delta through time suggest that the Mozambique current, which sweeps through the Mozambique Channel from northeast to southwest, initiated at the start of the Miocene.

  6. Determining the solid phases hosting arsenic in Mekong Delta sediments

    Science.gov (United States)

    Wucher, M.; Stuckey, J. W.; McCurdy, S.; Fendorf, S.

    2011-12-01

    The major river systems originating from the Himalaya deposit arsenic bearing sediment into the deltas of South and Southeast Asia. High rates of sediment and organic carbon deposition combined with frequent flooding leads to anaerobic processes that release arsenic into the pore-water. Arsenic concentrations in the groundwater of these sedimentary basins are often above the World Health Organization drinking water standard of 10 μg As L-1. As a result, 150 million people are at risk of chronic arsenic poisoning through water and rice consumption. The composition of the iron bearing phases hosting the arsenic in these deltaic sediments is poorly understood. Here we implemented a suite of selective chemical extractions to help constrain the types of arsenic bearing solid phases, which were complimented with synchrotron-based X-ray absorption spectroscopy and X-ray diffraction analyses to define the arsenic and iron mineralogy of the system. Sediment cores were collected in triplicate from a seasonally-inundated wetland in Cambodia at depths of 10, 50, 100, and 150 centimeters. We hypothesize that (i) arsenic will be predominantly associated with iron oxides, and (ii) the ratio of crystalline to amorphous iron oxides will increase with sediment depth (and age). We performed four selective extractions in parallel to quantify the various pools of arsenic. First, 1 M MgCl2 was used to extract electrostatically-bound arsenic (labile forms) from the sediment. Second, 1 M NaH2PO4 targeted strongly adsorbed arsenic. Third, 1 M HCl was used to liberated arsenic coprecipitated with amorphous Fe/Mn oxides, carbonates, and acid-volatile sulfides. Finally, a dithionite extraction was used to account for arsenic associated with reducible Fe/Mn oxides. Through this work, we identified the composition of the phases hosting arsenic at various depths through the soil profile, improving our understanding of how arsenic persists in the aquifer. In addition, defining the arsenic and

  7. Modeling microalgal flocculation and sedimentation

    NARCIS (Netherlands)

    Salim, S.; Gilissen, L.J.W.J.; Rinzema, A.; Vermuë, M.H.; Wijffels, R.H.

    2013-01-01

    In this study, a combined flocculation and sedimentation model is developed. The model predicts the time needed to reach a desired concentration of microalgal suspension in a sedimentation tank. The concentration of the particles as function of the time and the position in the tank is described. The

  8. Integrated Model for the Acoustics of Sediments

    Science.gov (United States)

    2013-09-30

    ocean sediments. HFEVA is based on the model found in the APL-UW handbook number 9407 [12]. Progress was achieved through the representation of the frame...This is the "swiss cheese " approximation, in which the frame bulk and shear moduli are essentially that of the solid material but diluted by the pores...High-Frequency Ocean Environmental Acoustic Models Handbook ," Applied Physics Laboratory, University of Washington, U.S. APL-UW 9407, (1994). 13. N. P

  9. The effects of solid-liquid interfacial tension on the settlement of sediment flocs

    CERN Document Server

    Jianglin, Z

    2006-01-01

    In this paper, the effects of interfacial tension between the sediment solid particle and liquid on the settlement of sediment flocs are investigated. After a discussion of mechanical and physical chemistry, we give a settling velocity expression including such dynamical information of the floc growth as interfacial tension and primary particle size \\textit{etc.}. The resulting expression indicates the average settling velocity of sediment flocs increases with increasing solid-liquid interfacial tension in a form of power law and deceases with the primary particle size. We report on a general method for analyzing settling behaviors of sediment flocs under different flocculation conditions and verify the rationality of the assumption of tension-induced flocculation by fitting typical experimental data to the electrolyte concentration-dependent sedimentation model which can follow from the relationship between interfacial tension and electrolyte concentration.

  10. Solid model design simplification

    Energy Technology Data Exchange (ETDEWEB)

    Ames, A.L.; Rivera, J.J.; Webb, A.J.; Hensinger, D.M.

    1997-12-01

    This paper documents an investigation of approaches to improving the quality of Pro/Engineer-created solid model data for use by downstream applications. The investigation identified a number of sources of problems caused by deficiencies in Pro/Engineer`s geometric engine, and developed prototype software capable of detecting many of these problems and guiding users towards simplified, useable models. The prototype software was tested using Sandia production solid models, and provided significant leverage in attacking the simplification problem.

  11. Modeling microalgal flocculation and sedimentation.

    Science.gov (United States)

    Salim, S; Gilissen, L; Rinzema, A; Vermuë, M H; Wijffels, R H

    2013-09-01

    In this study, a combined flocculation and sedimentation model is developed. The model predicts the time needed to reach a desired concentration of microalgal suspension in a sedimentation tank. The concentration of the particles as function of the time and the position in the tank is described. The model was validated with experimental data for Ettlia texensis. The concentration changes measured in time at different heights in the sedimentation vessel corresponded well with model predictions. The model predicts that it takes 25 h to reach a final concentration of 5.2 gDW L(-1), when the initial concentration is 0.26 gDW L(-1) and the tank height is 1m. This example illustrates the use of this model for the design of the settling tank needed for pre-concentration of microalgal biomass before further dewatering.

  12. Isolation of enteroviruses from water, suspended solids, and sediments from Galveston Bay: survival of poliovirus and rotavirus adsorbed to sediments.

    OpenAIRE

    Rao, V. C.; Seidel, K M; Goyal, S M; Metcalf, T. G.; Melnick, J L

    1984-01-01

    The distribution and quantitation of enteroviruses among water, suspended solids, and compact sediments in a polluted estuary are described. Samples were collected sequentially from water, suspended solids, fluffy sediments (uppermost layer of bottom sediments), and compact sediment. A total of 103 samples were examined of which 27 (26%) were positive for virus. Polioviruses were recovered most often, followed by coxsackie B viruses and echoviruses 7 and 29. Virus was found most often attache...

  13. Modelling of Suspended Sediment Discharge for Masinga ...

    African Journals Online (AJOL)

    Sedimentation models however, require suspended load as the basic input data. ... at the two mouths of the reservoir, at the confluence, and near the dam wall. ... Dredging out fine sediments, construction of sedimentation basins at the two ...

  14. Transport model of underground sediment in soils.

    Science.gov (United States)

    Jichao, Sun; Guangqian, Wang

    2013-01-01

    Studies about sediment erosion were mainly concentrated on the river channel sediment, the terrestrial sediment, and the underground sediment. The transport process of underground sediment is studied in the paper. The concept of the flush potential sediment is founded. The transport equation with stable saturated seepage is set up, and the relations between the flush potential sediment and water sediment are discussed. Flushing of underground sediment begins with small particles, and large particles will be taken away later. The pore ratio of the soil increases gradually. The flow ultimately becomes direct water seepage, and the sediment concentration at the same position in the water decreases over time. The concentration of maximal flushing potential sediment decreases along the path. The underground sediment flushing model reflects the flushing mechanism of underground sediment.

  15. Machine learning in sedimentation modelling.

    Science.gov (United States)

    Bhattacharya, B; Solomatine, D P

    2006-03-01

    The paper presents machine learning (ML) models that predict sedimentation in the harbour basin of the Port of Rotterdam. The important factors affecting the sedimentation process such as waves, wind, tides, surge, river discharge, etc. are studied, the corresponding time series data is analysed, missing values are estimated and the most important variables behind the process are chosen as the inputs. Two ML methods are used: MLP ANN and M5 model tree. The latter is a collection of piece-wise linear regression models, each being an expert for a particular region of the input space. The models are trained on the data collected during 1992-1998 and tested by the data of 1999-2000. The predictive accuracy of the models is found to be adequate for the potential use in the operational decision making.

  16. Numerical modeling method on the movement of water flow and suspended solids in two-dimensional sedimentation tanks in the wastewater treatment plant

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Taking the distributing calculation of velocity and concentration as an example, the paper established a series of governing equations by the vorticity-stream function method, and dispersed the equations by the finite differencing method. After figuring out the distribution field of velocity, the paper also calculated the concentration distribution in sedimentation tank by using the two-dimensional concentration transport equation. The validity and feasibility of the numerical method was verified through comparing with experimental data. Furthermore, the paper carried out a tentative exploration into the application of numerical simulation of sedimentation tanks.

  17. Modeling Transport of Flushed Reservoir Sediment

    Science.gov (United States)

    Dubinski, I. M.

    2014-12-01

    Drawdown flushing of a reservoir is often part of a reservoir sediment management program. Flushing can deliver higher than normal sediment loads to the river channel located downstream of a reservoir. The flushed sediment may contain a higher proportion of finer sediment than what was delivered to a channel prior to the presence of the reservoir. The extent of long-term impacts caused by the flushed sediment on the channel morphology and habitat will in part depend on the residence time of the sediment within the channel. In this study we used MIKE 21C to model the fate of flushed sediment through a river channel where the bed material consists of an armoring layer of gravels overlying finer sediment. MIKE 21C is a two-dimensional curvilinear morphological model for rivers developed by DHI. Curvilinear means that the model grid may curve to better follow the channel and flow direction, for example in a meandering channel. Multiple bed material layers are included in the model to represent the armoring and underlying layers existing in the bed separately from the overlying flushed sediment. These layers may also mix. The nature of the interactions between these two layers helps regulate transport and deposition of the flushed sediment, thus are critical to assessing the fate of the flushed sediment and associated potential impacts.

  18. Uncertainty in tsunami sediment transport modeling

    Science.gov (United States)

    Jaffe, Bruce E.; Goto, Kazuhisa; Sugawara, Daisuke; Gelfenbaum, Guy R.; La Selle, SeanPaul M.

    2016-01-01

    Erosion and deposition from tsunamis record information about tsunami hydrodynamics and size that can be interpreted to improve tsunami hazard assessment. We explore sources and methods for quantifying uncertainty in tsunami sediment transport modeling. Uncertainty varies with tsunami, study site, available input data, sediment grain size, and model. Although uncertainty has the potential to be large, published case studies indicate that both forward and inverse tsunami sediment transport models perform well enough to be useful for deciphering tsunami characteristics, including size, from deposits. New techniques for quantifying uncertainty, such as Ensemble Kalman Filtering inversion, and more rigorous reporting of uncertainties will advance the science of tsunami sediment transport modeling. Uncertainty may be decreased with additional laboratory studies that increase our understanding of the semi-empirical parameters and physics of tsunami sediment transport, standardized benchmark tests to assess model performance, and development of hybrid modeling approaches to exploit the strengths of forward and inverse models.

  19. Sediment flux modeling: Simulating nitrogen, phosphorus, and silica cycles

    Science.gov (United States)

    Testa, Jeremy M.; Brady, Damian C.; Di Toro, Dominic M.; Boynton, Walter R.; Cornwell, Jeffrey C.; Kemp, W. Michael

    2013-10-01

    Sediment-water exchanges of nutrients and oxygen play an important role in the biogeochemistry of shallow coastal environments. Sediments process, store, and release particulate and dissolved forms of carbon and nutrients and sediment-water solute fluxes are significant components of nutrient, carbon, and oxygen cycles. Consequently, sediment biogeochemical models of varying complexity have been developed to understand the processes regulating porewater profiles and sediment-water exchanges. We have calibrated and validated a two-layer sediment biogeochemical model (aerobic and anaerobic) that is suitable for application as a stand-alone tool or coupled to water-column biogeochemical models. We calibrated and tested a stand-alone version of the model against observations of sediment-water flux, porewater concentrations, and process rates at 12 stations in Chesapeake Bay during a 4-17 year period. The model successfully reproduced sediment-water fluxes of ammonium (NH4+), nitrate (NO3-), phosphate (PO43-), and dissolved silica (Si(OH)4 or DSi) for diverse chemical and physical environments. A root mean square error (RMSE)-minimizing optimization routine was used to identify best-fit values for many kinetic parameters. The resulting simulations improved the performance of the model in Chesapeake Bay and revealed (1) the need for an aerobic-layer denitrification formulation to account for NO3- reduction in this zone, (2) regional variability in denitrification that depends on oxygen levels in the overlying water, (3) a regionally-dependent solid-solute PO43- partitioning that accounts for patterns in Fe availability, and (4) a simplified model formulation for DSi, including limited sorption of DSi onto iron oxyhydroxides. This new calibration balances the need for a universal set of parameters that remain true to biogeochemical processes with site-specificity that represents differences in physical conditions. This stand-alone model can be rapidly executed on a

  20. Theoretical Evaluation of the Sediment/Water Exchange Description in Generic Compartment Models (SimpleBox)

    DEFF Research Database (Denmark)

    Sørensen, P. B.; Fauser, P.; Carlsen, L.

    It is shown how diffusion and deposition of solids drive the flux of substance between the water column and the sediment. The generic compartment models (Mackay type) use a one box model for the sediment in order to keep the calculations simple. However, when diffusion needs to be included...

  1. Multi-Fraction Bayesian Sediment Transport Model

    Directory of Open Access Journals (Sweden)

    Mark L. Schmelter

    2015-09-01

    Full Text Available A Bayesian approach to sediment transport modeling can provide a strong basis for evaluating and propagating model uncertainty, which can be useful in transport applications. Previous work in developing and applying Bayesian sediment transport models used a single grain size fraction or characterized the transport of mixed-size sediment with a single characteristic grain size. Although this approach is common in sediment transport modeling, it precludes the possibility of capturing processes that cause mixed-size sediments to sort and, thereby, alter the grain size available for transport and the transport rates themselves. This paper extends development of a Bayesian transport model from one to k fractional dimensions. The model uses an existing transport function as its deterministic core and is applied to the dataset used to originally develop the function. The Bayesian multi-fraction model is able to infer the posterior distributions for essential model parameters and replicates predictive distributions of both bulk and fractional transport. Further, the inferred posterior distributions are used to evaluate parametric and other sources of variability in relations representing mixed-size interactions in the original model. Successful OPEN ACCESS J. Mar. Sci. Eng. 2015, 3 1067 development of the model demonstrates that Bayesian methods can be used to provide a robust and rigorous basis for quantifying uncertainty in mixed-size sediment transport. Such a method has heretofore been unavailable and allows for the propagation of uncertainty in sediment transport applications.

  2. A Sediment Transport Model for Sewers

    DEFF Research Database (Denmark)

    Mark, Ole; Larsson, Johan; Larsen, Torben

    1993-01-01

    This paper describes a mathematical model for transport processes in sewers. The model consists of three sub models, a surface model for the description of the buildup and the washoff of sediment particles from the surface area, a morphological model and an advection-dispersion model. The model...

  3. A MATHEMATICAL MODEL OF RESERVOIR SEDIMENTATION

    Institute of Scientific and Technical Information of China (English)

    HUANG Jinchi

    2001-01-01

    Reliable quantitative estimation of bed aggradation or degradation is important for river-training and water management projects. With the development of water resources, sediment problems associated with a dam are becoming more severe. This paper describes some special problems in mathematical model for calculation of degradation and aggradation in a reservoir. The main efforts of this study are on the treatment of some physical processes of fine sediment transport (<0.05 mm). Problems in a reservoir are obviously different from a natural stream, such as the turbid current flow, orifice sediment flushing;and the initiation and consolidation of cohesive sediment deposition. The case of Liujiaxia Reservoir,which is located in the upper reaches of the Yellow River, is employed to verify the model. The results show that the model is applicable in the evaluation of an engineering planing with plenty of fine sediment movement.

  4. Modeling Sediment Bypassing around Rocky Headlands

    Science.gov (United States)

    George, D. A.; Largier, J. L.; Pasternack, G. B.; Erikson, L. H.; Storlazzi, C. D.; Barnard, P.

    2016-12-01

    Sediment bypassing rocky headlands remains understudied despite the importance of characterizing littoral processes and sediment budgets for erosion abatement, climate change adaptation, and beach management. This study was developed to identify controlling factors on and the mechanisms supporting sediment bypassing. Sediment flux around four idealized rocky headlands was investigated using the hydrodynamic model Delft3D and spectral wave model SWAN. The experimental design involved 120 simulations to explore the influence of headland morphology, substrate composition, sediment grain size, and oceanographic forcing. Headlands represented sizes and shapes found in natural settings, grain sizes ranged from fine to medium sand, and substrates from sandy beds to offshore bedrock reefs. The oceanography included a constructed representative tide, an alongshore background current, and four wave conditions derived from observational records in the eastern Pacific Ocean. A bypassing ratio was developed for alongshore flux between upstream and downstream cross-shore transects to determine the degree of blockage by a headland. Results showed that northwesterly oblique large waves (Hs = 7 m, Tp = 16 s) generated the most flux around headlands, whereas directly incident waves blocked flux across a headland apex. The headland shape heavily influenced the sediment fate by changing the relative angle between the shoreline and the incident waves. The bypassing ratio characterized each headland's capacity to allow alongshore flux under different wave conditions. All headlands may allow flux, although larger ones block sediment more effectively, promoting their ability to be littoral cell boundaries compared to smaller headlands. The controlling factors on sediment bypassing were determined to be wave angle, shape and size of the headland, and sediment grain size. This novel numerical modeling study advances headland modeling from the generic realm to broadly applicable classes of

  5. Modeling sediment transport in river networks

    Science.gov (United States)

    Wang, Xu-Ming; Hao, Rui; Huo, Jie; Zhang, Jin-Feng

    2008-11-01

    A dynamical model is proposed to study sediment transport in river networks. A river can be divided into segments by the injection of branch streams of higher rank. The model is based on the fact that in a real river, the sediment-carrying capability of the stream in the ith segment may be modulated by the undergone state, which may be erosion or sedimentation, of the i-1th and ith segments, and also influenced by that of the ith injecting branch of higher rank. We select a database about the upper-middle reach of the Yellow River in the lower-water season to test the model. The result shows that the data, produced by averaging the erosion or sedimentation over the preceding transient process, are in good agreement with the observed average in a month. With this model, the steady state after transience can be predicted, and it indicates a scaling law that the quantity of erosion or sedimentation exponentially depends on the number of the segments along the reach of the channel. Our investigation suggests that fluctuation of the stream flow due to random rainfall will prevent this steady state from occurring. This is owing to the phenomenon that the varying trend of the quantity of erosion or sedimentation is opposite to that of sediment-carrying capability of the stream.

  6. Solid and aqueous mercury in remote river sediments (Litany River, French Guyana, South America)

    Science.gov (United States)

    Charlet, L.; Roman-Ross, G.; Spadini, L.; Rumbach, G.

    2003-05-01

    Mercury content in river sediments was investigated, in the Haut Maroni river basin (French Guyana, South America), around Antecume-Pata, a village where Wayanas Amerindians are contaminated with mercury. Solid sediment particulate total mercury content indicate a 100 to 150 ng/g Hg geochemical background level. Sediments act as an environmental archive: gold mining contaminated sediments have up to 400 ng/g total mercury. Pore waters from contaminated sediments are enriched in Fe(II) and Hg(II) by a factor 40 compared to uncontaminated sediment pore waters, due to more acute anoxie conditions. They act therefore as a major source of dissolved mercury in remote tropical aquatic ecosystems. Keywords: Mercury, sediment, DGT and DET techniques, pore water, gold mining.

  7. Modeling solid-state precipitation

    CERN Document Server

    Nebylov, AlexanderKozeschnik, Ernst

    2012-01-01

    Over recent decades, modeling and simulation of solid-state precipitation has attracted increased attention in academia and industry due to their important contributions in designing properties of advanced structural materials and in increasing productivity and decreasing costs for expensive alloying. In particular, precipitation of second phases is an important means for controlling the mechanical-technological properties of structural materials. However, profound physical modeling of precipitation is not a trivial task. This book introduces you to the classical methods of precipitation model

  8. Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling

    Science.gov (United States)

    Helgerud, M.B.; Dvorkin, J.; Nur, A.; Sakai, A.; Collett, T.

    1999-01-01

    We offer a first-principle-based effective medium model for elastic-wave velocity in unconsolidated, high porosity, ocean bottom sediments containing gas hydrate. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from those of the dry frame using Gassmann's equation. To model the effect of gas hydrate on sediment elastic moduli we use two separate assumptions: (a) hydrate modifies the pore fluid elastic properties without affecting the frame; (b) hydrate becomes a component of the solid phase, modifying the elasticity of the frame. The goal of the modeling is to predict the amount of hydrate in sediments from sonic or seismic velocity data. We apply the model to sonic and VSP data from ODP Hole 995 and obtain hydrate concentration estimates from assumption (b) consistent with estimates obtained from resistivity, chlorinity and evolved gas data. Copyright 1999 by the American Geophysical Union.

  9. EXPERIMENTAL STUDIES AND SIMULATIONS ON GRAVITATIONAL SEDIMENTATION OF THE SOLID POLUTANTS IN SUSPENSION

    Directory of Open Access Journals (Sweden)

    Sorin Anghel

    2010-01-01

    Full Text Available Sedimentation of suspensions process is important, especially in pollution and biologic studies. Unlike usual methods,as those using pipettes, aerometer or balances, the optical ones are nondestructive and more accurate. During thesedimentation produced by the braked fall off the solid particles in suspension, fluctuations induced by an oppositevertical diffusion occur. We used a scattering method, based on the attenuation of a laser beam, which allows plottingsedimentation curves (the dependence on time of the suspended solid particles concentration of the process. Weobtained an empirical relation describing sedimentation curves as a function of some main parameters (related toinitial concentration, height in suspension, dimensions of suspended solid particles and we performed a simulation ofthe experimental sedimentation curves using the obtained relation and Mathcad software facilities. We notice that theresults of these studies allow using a fast method in order to determine the sedimentation time, which often can be verylong.

  10. Sediment contamination assessment in urban areas based on total suspended solids.

    Science.gov (United States)

    Rossi, Luca; Chèvre, Nathalie; Fankhauser, Rolf; Margot, Jonas; Curdy, Romuald; Babut, Marc; Barry, D Andrew

    2013-01-01

    Sediment represents an important compartment in surface waters. It constitutes a habitat or spawning site for many organisms and is an essential trophic resource for higher level organisms. It can be impacted by anthropogenic activities, particularly through urban wet-weather discharges like stormwater and combined sewer overflows. An approach was presented for assessing the risks caused by urban wet-weather discharges to the sediment compartment based on total suspended solids (TSS). TSS is routinely measured in field surveys and can be considered as a tracer for urban wet-weather contamination. Three assessment endpoints linked with TSS were proposed: a) siltation of the riverbed, b) oxygen demand due to organic matter degradation and c) accumulation of ecotoxic contaminants on the riverbed (heavy metals, PAHs). These criteria were translated in terms of the maximal TSS accumulation load and exposure time (percentage of time exceeding the accumulation criteria) to account for sediment accumulation dynamics and resuspension in streams impacted by urban wet-weather discharges. These assessment endpoints were implemented in a stochastic model that calculates TSS behavior in receiving waters and allows therefore an assessment of potential impacts. The approach was applied to three Swiss case studies. For each, good agreement was found between the risk predictions and the field measurements confirming the reliability of the approach. Copyright © 2012 Elsevier Ltd. All rights reserved.

  11. RATIONAL BASIS FOR SUSPENDED SEDIMENT MODELING

    Institute of Scientific and Technical Information of China (English)

    Jianjun ZHOU; Binliang LIN; Bingnan LIN

    2003-01-01

    This paper presents a rational basis to model the transport of suspended sediment. The looseboundary condition for 3D models and the adjustment coefficients for both the depth-integrated 2D and laterally integrated 1D models are treated comprehensively. A combination of Dirichlet and Neumann conditions is proposed as the loose-boundary condition. The adjustment coefficient for 2D models is obtained on the basis of the proposed boundary condition and analytical solutions developed for some simple cases of non-equilibrium transport of sediment in uniform flows. The adjustment coefficient for 1D models for natural rivers is further obtained from lateral integration. Comparisons with analytical solutions and a considerable amount of laboratory and prototype data show that mathematical models developed along the proposed line of attack would well simulate the transport of suspended sediment in practical problems.

  12. Mathematical modelling in solid mechanics

    CERN Document Server

    Sofonea, Mircea; Steigmann, David

    2017-01-01

    This book presents new research results in multidisciplinary fields of mathematical and numerical modelling in mechanics. The chapters treat the topics: mathematical modelling in solid, fluid and contact mechanics nonconvex variational analysis with emphasis to nonlinear solid and structural mechanics numerical modelling of problems with non-smooth constitutive laws, approximation of variational and hemivariational inequalities, numerical analysis of discrete schemes, numerical methods and the corresponding algorithms, applications to mechanical engineering numerical aspects of non-smooth mechanics, with emphasis on developing accurate and reliable computational tools mechanics of fibre-reinforced materials behaviour of elasto-plastic materials accounting for the microstructural defects definition of structural defects based on the differential geometry concepts or on the atomistic basis interaction between phase transformation and dislocations at nano-scale energetic arguments bifurcation and post-buckling a...

  13. Modeling transportation of suspended solids in Zhujiang River estuary, South China

    Institute of Scientific and Technical Information of China (English)

    CHEN Xiaohong; CHEN Yongqin; LAI Guoyou

    2005-01-01

    A three-dimensional transportation model for suspended solids (SS) in Zhujiang (Pearl) River estuary, South China, was developed by coupling with a three-dimensional hydrodynamic model. The model was validated using hourly measured data of sediment contents during 25-26, July 1999. The results showed that modeled contents matched well with measured ones and that the modeled top layer distribution agreed with the remotely sensed image of suspended solids in summer. The modeled results showed clearly the layers of suspended solids in depth, with larger sediment contents in lower layers though in the interface between salt water and freshwater the lowest contents appeared in middle layer. In overall, the suspended solids inflow from 8 rivers, transport southwestward, and carried by strong coastal flow in Zhujiang River estuary. Contours of sediment contents in the estuary spread further to the open sea during ebb tide rather than flood tide which reflects that the suspended solids in the estuary are land sourced.

  14. Water-sediment flow models for river reaches sediment related pollution control.

    Science.gov (United States)

    Sil, Briti Sundar; Choudhury, Parthasarathi

    2012-07-01

    Hybrid water-sediment flow models for river reaches have been for predicting sediment and sediment related pollutions in water courses. The models are developed by combining sediment rating model and the Muskingum model applicable for a reach. The models incorporate sediment concentration and water discharge variables for a river reach; allow defining downstream sediment rating curve in terms of upstream water discharges. The model is useful in generating sediment concentration graph for a station having no water discharge records. The hybrid models provide forecasting forms that can be used to forecast downstream sediment concentration/water discharges 2kx time unit ahead. The forecasting models are useful for applications in real time namely, in the real time management of sediment related pollution in water courses and in issuing flood warning. Integration of sediment rating model and the Muskingum model increases model parameters and nonlinearity requiring efficient estimation technique for parameter identification. To identify parameters in the hybrid models genetic algorithm (GA) based optimization technique can be used. The new model relies on the Muskingum model, obey continuity requirement and the parameters can be used in the Muskingum model with water discharges to estimate/predict downstream water discharge values. The proposed model formulations are demonstrated for simulating and forecasting sediment concentration and water discharges in the Mississippi River Basin, USA. Model parameters are estimated using non-dominated sorting Genetic Algorithm II (NSGA-II). Model results show satisfactory model performances.

  15. Sediment-copper distributions in hyper-concentrated turbulent solid-liquid system

    Institute of Scientific and Technical Information of China (English)

    YANG Jun; NI Jin-ren

    2007-01-01

    This study presents a special problem on vertical distribution for sediment and copper in hyper-concentrated turbulent solid-liquid system that is essentially different from the ordinary low-concentrated turbulent system. A resonance type turbulent simulation equipment is used for the experimental study in which a vertically uniform turbulent field of the mixture of loess and water is produced in a testing cylinder with a grille stirrer that moves up and down harmoniously with varying vibration frequencies. In order to compare the variations of the vertical profiles of sediment and copper in low- and hyper-concentrated solid-liquid system, different scenarios for input sediment content ranging from 5 to 800 kg/m3 was considered in the experimental studies. It was found that solids copper content increases with input sediment content, S0, and reaches its peak as S0 goes to 10 kg/m3 and then decreases rapidly with increasing input sediment content. Such a behavior is possibly resulted from the joint effect of the specific adsorption of copper on loess, precipitation of carbonate and hydroxide of copper due to high carbonate content in the loess and the so-called "particulate concentration effect" due to the present of the sediment variation in water. The vertical sediment concentration distribution resulted from the uniform turbulence is generally uniform, but slight non-uniformity does occur as sediment concentration exceeds certain value. However, the vertical concentration distributions of soluble copper seem not affected much by the variation of sediment concentrations.

  16. Discrete element modeling of subglacial sediment deformation

    DEFF Research Database (Denmark)

    Damsgaard, Anders; Egholm, David L.; Piotrowski, Jan A.

    2013-01-01

    -shear experiments on simple granular materials are compared to results from similar numerical experiments. The simulated DEM material and all tested laboratory materials deform by an elasto-plastic rheology under the applied effective normal stress. These results demonstrate that the DEM is a viable alternative...... on the level of normal (overburden) stress, and we show how high normal stress can mobilize material to great depths. The particle rotational axes tend to align with progressive shear strain, with rotations both along and reverse to the shear direction. The results from successive laboratory ring...... to continuum models for small-scale analysis of sediment deformation. It can be used to simulate the macromechanical behavior of simple granular sediments, and it provides an opportunity to study how microstructures in subglacial sediments are formed during progressive shear strain....

  17. Calibration suspended sediment model Markermeer

    NARCIS (Netherlands)

    Boderie, P.; Van Kessel, T.; De Boer, G.

    2009-01-01

    In deze studie is een computermodel voor het Markermeer opgezet, ingeregeld en gevalideerd. Het model beschrijft dynamsch de stroming van water, waterpeilen, golven en slib in het water en in de bodem. Het model is gecalibreerd voorde periode augustus 2007 - april 2008 en gevalideerd voor de periode

  18. A biogeochemical model of contaminant fate and transport in river waters and sediments.

    Science.gov (United States)

    Massoudieh, Arash; Bombardelli, Fabián A; Ginn, Timothy R

    2010-03-01

    A quasi-two-dimensional model is presented for simulating transport and transformation of contaminant species in river waters and sediments, taking into account the effect of both biotic and abiotic geochemical reactions on the contaminant fate and mobility. The model considers the downstream transport of dissolved and sediment-associated species, and the mass transfer with bed sediments due to erosion and resuspension, using linked advection-dispersion-reaction equations. The model also couples both equations to the reactive transport within bed sediment phases. This is done by the use of a set of vertical one-dimensional columns representing sediment layers that take into account the reactive transport of chemicals, burial, sorption/desorption to/from the solid phase, and the diffusive transport of aqueous species. Kinetically-controlled reversible solid-water mass exchange models are adopted to simulate interactions between suspended sediments and bulk water, as well as the mass exchange between bed sediments and pore water. An innovative multi-time step approach is used to model the fully kinetic nonlinear reaction terms using a non-iterative explicit method. This approach enables the model to handle fast and near-equilibrium reactions without a significant increase in computational burden. At the end, two demonstration cases are simulated using the model, including transport of a sorbing, non-reactive trace metal and nitrogen cycling, both in the Colusa Basin Drain in the Central Valley of California.

  19. Modeling solid-state precipitation

    CERN Document Server

    Nebylov, AlexanderKozeschnik, Ernst

    2012-01-01

    Over recent decades, modeling and simulation of solid-state precipitation has attracted increased attention in academia and industry due to their important contributions in designing properties of advanced structural materials and in increasing productivity and decreasing costs for expensive alloying. In particular, precipitation of second phases is an important means for controlling the mechanical-technological properties of structural materials. However, profound physical modeling of precipitation is not a trivial task. This book introduces you to the classical methods of precipitation modeling and to recently-developed advanced, computationally-efficient techniques. If you're a research professional, academic, or student, you'll learn: nucleation theory, precipitate growth, calculation of interfacial energies. advanced techniques for technologically relevant multicomponent systems and complex thermo-mechanical treatments. numerical approaches using evolution equations and discrete particle size distribu...

  20. Confirmatory sediment analyses and solid and suspended particulate phase bioassays on sediment from Oakland Inner Harbor, San Francisco, California

    Energy Technology Data Exchange (ETDEWEB)

    Word, J.Q.; Ward, J.A.; Apts, C.W.; Woodruff, D.L.; Barrows, M.E.; Cullinan, V.I.; Hyland, J.L.; Campbell, J.F.

    1988-12-01

    The US Army Corps of Engineers (USACE), San Francisco District, was authorized by the US Congress to deepen the navigation channels of Inner and Outer Oakland Harbor, California. During review of the environmental impact statement required for this dredging and disposal project, a panel of national experts approved the open-water disposal of dredged sediment from selected areas within the Inner Harbor, subject to results of confirmatory solid phase bioassays. The San Francisco District of the Corps requested the Battle/Marine Sciences Laboratory (MSL) to conduct these confirmatory studies. The studies provided technical data for an evaluation of the potential environmental impact of this project. Within extremely narrow time constraints, these studies provided chemical and biological information required by ocean dumping regulations to determine suitability of the Oakland Inner Harbor and turning basin sediment for ocean disposal. 23 refs., 18 figs., 45 tabs.

  1. Modelling sediment export, retention and reservoir sedimentation in drylands with the WASA-SED model

    Directory of Open Access Journals (Sweden)

    E. N. Mueller

    2010-04-01

    Full Text Available Current soil erosion and reservoir sedimentation modelling at the meso-scale is still faced with intrinsic problems with regard to open scaling questions, data demand, computational efficiency and deficient implementations of retention and re-mobilisation processes for the river and reservoir networks. To overcome some limitations of current modelling approaches, the semi-process-based, spatially semi-distributed modelling framework WASA-SED (Vers. 1 was developed for water and sediment transport in large dryland catchments. The WASA-SED model simulates the runoff and erosion processes at the hillslope scale, the transport and retention processes of suspended and bedload fluxes in the river reaches and the retention and remobilisation processes of sediments in reservoirs. The modelling tool enables the evaluation of management options both for sustainable land-use change scenarios to reduce erosion in the headwater catchments as well as adequate reservoir management options to lessen sedimentation in large reservoirs and reservoir networks. The model concept, its spatial discretisation scheme and the numerical components of the hillslope, river and reservoir processes are described and a model application for the meso-scale dryland catchment Isábena in the Spanish Pre-Pyrenees (445 km2 is presented to demonstrate the capabilities, strengths and limits of the model framework. The example application showed that the model was able to reproduce runoff and sediment transport dynamics of highly erodible headwater badlands, the transient storage of sediments in the dryland river system, the bed elevation changes of the 93 hm3 Barasona reservoir due to sedimentation as well as the life expectancy of the reservoir under different management options.

  2. A probabilistic sediment cascade model of sediment transfer in the Illgraben

    Science.gov (United States)

    Bennett, G. L.; Molnar, P.; McArdell, B. W.; Burlando, P.

    2014-02-01

    We present a probabilistic sediment cascade model to simulate sediment transfer in a mountain basin (Illgraben, Switzerland) where sediment is produced by hillslope landslides and rockfalls and exported out of the basin by debris flows and floods. The model conceptualizes the fluvial system as a spatially lumped cascade of connected reservoirs representing hillslope and channel storages where sediment goes through cycles of storage and remobilization by surface runoff. The model includes all relevant hydrological processes that lead to runoff formation in an Alpine basin, such as precipitation, snow accumulation, snowmelt, evapotranspiration, and soil water storage. Although the processes of sediment transfer and debris flow generation are described in a simplified manner, the model produces complex sediment discharge behavior which is driven by the availability of sediment and antecedent wetness conditions (system memory) as well as the triggering potential (climatic forcing). The observed probability distribution of debris flow volumes and their seasonality in 2000-2009 are reproduced. The stochasticity of hillslope sediment input is important for reproducing realistic sediment storage variability, although many details of the hillslope landslide triggering procedures are filtered out by the sediment transfer system. The model allows us to explicitly quantify the division into transport and supply-limited sediment discharge events. We show that debris flows may be generated for a wide range of rainfall intensities because of variable antecedent basin wetness and snowmelt contribution to runoff, which helps to understand the limitations of methods based on a single rainfall threshold for debris flow initiation in Alpine basins.

  3. Protocol evaluation of the total suspended solids and suspended sediment concentration methods: solid recovery efficiency and application for stormwater analysis.

    Science.gov (United States)

    Chan, Licheng; Li, Yingxia; Stenstrom, Michael K

    2008-09-01

    Total suspended solids (TSS) is routinely measured in water and wastewater treatment plants, and protocols are well-known. The TSS measurement in stormwater is more difficult, because the particle size and density can be much greater, biasing the sample if it is collected from a poorly mixed location or allowed to settle in a quiescent collection container. An alternative method, called suspended sediment concentration (SSC), uses a different protocol, which analyzes the entire contents of the sample collection container. The SSC method is not compatible with many monitoring programs, which require several constituents to be analyzed from a single sample container, such as from a flow-weighted composite sample. This paper addresses TSS protocol using glass beads and samples with known particle size distribution and shows that proper mixing, combined with appropriate pipettes, can largely avoid sampling error for typical sediments as large as 250 microm with specific gravity of 2.6.

  4. Accounting for Long Term Sediment Storage in a Watershed Scale Numerical Model for Suspended Sediment Routing

    Science.gov (United States)

    Keeler, J. J.; Pizzuto, J. E.; Skalak, K.; Karwan, D. L.; Benthem, A.; Ackerman, T. R.

    2015-12-01

    Quantifying the delivery of suspended sediment from upland sources to downstream receiving waters is important for watershed management, but current routing models fail to accurately represent lag times in delivery resulting from sediment storage. In this study, we route suspended sediment tagged by a characteristic tracer using a 1-dimensional model that implicitly includes storage and remobilization processes and timescales. From an input location where tagged sediment is added, the model advects suspended sediment downstream at the velocity of the stream (adjusted for the intermittency of transport events). Deposition rates are specified by the fraction of the suspended load stored per kilometer of downstream transport (presumably available from a sediment budget). Tagged sediment leaving storage is evaluated from a convolution equation based on the probability distribution function (pdf) of sediment storage waiting times; this approach avoids the difficulty of accurately representing complex processes of sediment remobilization from floodplain and other deposits. To illustrate the role of storage on sediment delivery, we compare exponential and bounded power-law waiting time pdfs with identical means of 94 years. In both cases, the median travel time for sediment to reach the depocenter in fluvial systems less than 40km long is governed by in-channel transport and is unaffected by sediment storage. As the channel length increases, however, the median sediment travel time reflects storage rather than in-channel transport; travel times do not vary significantly between the two different waiting time functions. At distances of 50, 100, and 200 km, the median travel time for suspended sediment is 36, 136, and 325 years, orders of magnitude slower than travel times associated with in-channel transport. These computations demonstrate that storage can be neglected for short rivers, but for longer systems, storage controls the delivery of suspended sediment.

  5. Sediment mathematical model for sand ridges and sand waves

    Institute of Scientific and Technical Information of China (English)

    LI Daming; WANG Xiao; WANG Xin; LI Yangyang

    2016-01-01

    A new theoretical model is formulated to describe internal movement mechanisms of the sand ridges and sand waves based on the momentum equation of a solid-liquid two-phase flow under a shear flow. Coupling this equation with two-dimensional shallow water equations and wave reflection-diffraction equation of mild slope, a two-dimensional coupling model is established and a validation is carried out by observed hydrogeology, tides, waves and sediment. The numerical results are compared with available observations. Satisfactory agreements are achieved. This coupling model is then applied to the Dongfang 1-1 Gas Field area to quantitatively predict the movement and evolution of submarine sand ridges and sand waves. As a result, it is found that the sand ridges and sand waves movement distance increases year by year, but the development trend is stable.

  6. MODELING AND SIMULATION OF SOLID FLUIDIZATION IN A RESIN COLUMN

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S.

    2014-06-24

    The objective of the present work is to model the resin particles within the column during fluidization and sedimentation processes using computation fluid dynamics (CFD) approach. The calculated results will help interpret experimental results, and they will assist in providing guidance on specific details of testing design and establishing a basic understanding of particle’s hydraulic characteristics within the column. The model is benchmarked against the literature data and the test data (2003) conducted at Savannah River Site (SRS). The paper presents the benchmarking results and the modeling predictions of the SRS resin column using the improved literature correlations applicable for liquid-solid granular flow.

  7. MODELING SIMULATION OF SEDIMENT ANALYSIS FOR MALAPRABHA RIVER IN KARNATAKA STATE, INDIA

    Directory of Open Access Journals (Sweden)

    Vinayak Krishnamurty Naik

    2008-01-01

    Full Text Available Transport, settling and quantity of solutes in rivers, streams, lakes and reservoirs are the important aspects in water-quality modeling. This has been the major concern for the researchers, scientists and engineers for the last 50 years who actively involved in water quality modeling. Consequently, characterization of hydrodynamics and water budgets has been an essential component in the water-quality modeling. This paper presents on the simulation model for sediment transport, solids budget, bottom sediment as a distributed system under steady-state condition, and resuspension of solids due to currents etc. The solids considered for the study was mainly allochthonous as these are inorganic in nature and the rate of decomposition is negligible. The data collected refers to the part of the research work on Malaprabha River, near Belgaum - a district headquarters in the State of Karnataka, India. This river is a non-perennial one, and the flow is very less during the pre-monsoon period, which is favorable for application of these sediment models. The results obtained for the resuspension and burial velocities showed marked variations during the different seasons of the year. Resuspension velocities predominated during the monsoon period resulting in the nonsettlement of the solids and the burial velocity during the non-monsoon period. As the river receives raw sewage from an adjoining town - Khanapur, and also the agricultural discharges, it is worth to quantify the sediment deposition in the stream.

  8. MODELING SIMULATION OF SEDIMENT ANALYSIS FOR MALAPRABHA RIVER IN KARNATAKA STATE, INDIA

    Directory of Open Access Journals (Sweden)

    Vinayak Krishnamurty Naik

    2008-06-01

    Full Text Available Transport, settling and quantity of solutes in rivers, streams, lakes and reservoirs are the important aspects in water-quality modeling. This has been the major concern for the researchers, scientists and engineers for the last 50 years who actively involved in water quality modeling. Consequently, characterization of hydrodynamics and water budgets has been an essential component in the water–quality modeling. This paper presents on the simulation model for sediment transport, solids budget, bottom sediment as a distributed system under steady-state condition, and resuspension of solids due to currents etc. The solids considered for the study was mainly allochthonous as these are inorganic in nature and the rate of decomposition is negligible. The data collected refers to the part of the research work on Malaprabha River, near Belgaum – a district headquarters in the State of Karnataka, India. This river is a non-perennial one, and the flow is very less during the pre-monsoon period, which is favorable for application of these sediment models. The results obtained for the resuspension and burial velocities showed marked variations during the different seasons of the year. Resuspension velocities predominated during the monsoon period resulting in the nonsettlement of the solids and the burial velocity during the non-monsoon period. As the river receives raw sewage from an adjoining town – Khanapur, and also the agricultural discharges, it is worth to quantify the sediment deposition in the stream.

  9. Integrated Model for the Acoustics of Sediments

    Science.gov (United States)

    2014-09-30

    the solid material. This model has been associated with seismic wave propagation in essentially dry soil. A second loss mechanism in fluid-saturated...multiple scattering (MS). [The left panel shows wave attenuations as functions of frequency with measured and modeled data points. The right panels...acoustic interaction with the ocean floor including penetration, reflection and scattering in support of MCM and ASW needs. OBJECTIVES The

  10. Modeling Hydrodynamics, Water Temperature, and Suspended Sediment in Detroit Lake, Oregon

    Science.gov (United States)

    Sullivan, Annett B.; Rounds, Stewart A.; Sobieszczyk, Steven; Bragg, Heather M.

    2007-01-01

    Detroit Lake is a large reservoir on the North Santiam River in west-central Oregon. Water temperature and suspended sediment are issues of concern in the river downstream of the reservoir. A CE-QUAL-W2 model was constructed to simulate hydrodynamics, water temperature, total dissolved solids, and suspended sediment in Detroit Lake. The model was calibrated for calendar years 2002 and 2003, and for a period of storm runoff from December 1, 2005, to February 1, 2006. Input data included lake bathymetry, meteorology, reservoir outflows, and tributary inflows, water temperatures, total dissolved solids, and suspended sediment concentrations. Two suspended sediment size groups were modeled: one for suspended sand and silt with particle diameters larger than 2 micrometers, and another for suspended clay with particle diameters less than or equal to 2 micrometers. The model was calibrated using lake stage data, lake profile data, and data from a continuous water-quality monitor on the North Santiam River near Niagara, about 6 kilometers downstream of Detroit Dam. The calibrated model was used to estimate sediment deposition in the reservoir, examine the sources of suspended sediment exiting the reservoir, and examine the effect of the reservoir on downstream water temperatures.

  11. A process-based model for aeolian sediment transport and spatiotemporal varying sediment availability

    Science.gov (United States)

    Hoonhout, Bas M.; Vries, Sierd de

    2016-08-01

    Aeolian sediment transport is influenced by a variety of bed surface properties, like moisture, shells, vegetation, and nonerodible elements. The bed surface properties influence aeolian sediment transport by changing the sediment transport capacity and/or the sediment availability. The effect of bed surface properties on the transport capacity and sediment availability is typically incorporated through the velocity threshold. This approach appears to be a critical limitation in existing aeolian sediment transport models for simulation of real-world cases with spatiotemporal variations in bed surface properties. This paper presents a new model approach for multifraction aeolian sediment transport in which sediment availability is simulated rather than parameterized through the velocity threshold. The model can cope with arbitrary spatiotemporal configurations of bed surface properties that either limit or enhance the sediment availability or sediment transport capacity. The performance of the model is illustrated using four prototype cases, the simulation of two wind tunnel experiments from literature and a sensitivity analysis of newly introduced parameters.

  12. Discrete element modeling of subglacial sediment deformation

    Science.gov (United States)

    Damsgaard, Anders; Egholm, David L.; Piotrowski, Jan A.; Tulaczyk, Slawek; Larsen, Nicolaj K.; Tylmann, Karol

    2013-12-01

    The Discrete Element Method (DEM) is used in this study to explore the highly nonlinear dynamics of a granular bed when exposed to stress conditions comparable to those at the bed of warm-based glaciers. Complementary to analog experiments, the numerical approach allows a detailed analysis of the material dynamics and the shear zone development during progressive shear strain. The geometry of the heterogeneous stress network is visible in the form of force-carrying grain bridges and adjacent, volumetrically dominant, inactive zones. We demonstrate how the shear zone thickness and dilation depend on the level of normal (overburden) stress, and we show how high normal stress can mobilize material to great depths. The particle rotational axes tend to align with progressive shear strain, with rotations both along and reverse to the shear direction. The results from successive laboratory ring-shear experiments on simple granular materials are compared to results from similar numerical experiments. The simulated DEM material and all tested laboratory materials deform by an elastoplastic rheology under the applied effective normal stress. These results demonstrate that the DEM is a viable alternative to continuum models for small-scale analysis of sediment deformation. It can be used to simulate the macromechanical behavior of simple granular sediments, and it provides an opportunity to study how microstructures in subglacial sediments are formed during progressive shear strain.

  13. Discrete element modelling of sediment falling in water.

    Science.gov (United States)

    Wang, Dong; Ho-Minh, Dao; Tan, Danielle S

    2016-11-01

    The Discrete Element Method (DEM) is a discrete, particle-based method commonly used in studies involving granular media, e.g. sediment transport, and geomechanics. It is heavily dependent on particle properties, and one important component is the force model, which relates the relative positions and velocities of the simulated particles to the forces they experience. In this paper we model a collection of lightly compacted granular material, released at a short distance above a flat base in a quiescent fluid --similar to the process whereby sediment tailings are released back into the sea during nodule harvesting. We employ different typical force models, and consider how their varying components affect the simulated outcome. The results are compared with a physical experiment of similar dimensions. We find that a realistic simulation is achieved when the force model considers the local solid fraction in the drag force, and incorporates the hydrodynamic effect of neighbouring particles. The added mass effect increases the accuracy of the outcome, but does not contribute significantly in a qualitative sense.

  14. Building Mathematical Models Of Solid Objects

    Science.gov (United States)

    Randall, Donald P.; Jones, Kennie H.; Von Ofenheim, William H.; Gates, Raymond L.; Matthews, Christine G.

    1989-01-01

    Solid Modeling Program (SMP) version 2.0 provides capability to model complex solid objects mathematically through aggregation of geometric primitives (parts). System provides designer with basic set of primitive parts and capability to define new primitives. Six primitives included in present version: boxes, cones, spheres, paraboloids, tori, and trusses. Written in VAX/VMS FORTRAN 77.

  15. A probabilistic sediment cascade model of sediment transfer through a mountain basin

    Science.gov (United States)

    Bennett, G. L.; Molnar, P.; McArdell, B. W.; Lane, S. N.; Burlando, P.

    2013-12-01

    Mountain basin sediment discharge poses a significant hazard to the downstream population, particularly in the form of debris flows. The importance and sensitivity of snow and ice melt processes in mountain basins along with their rapid rainfall-runoff response makes mountain basin sediment discharge particularly responsive to climate change. It is important to understand and model sediment transfer through mountain basins to be able to predict sediment discharge under a changing climate. We developed a probabilistic sediment cascade model, SedCas, to simulate sediment transfer in a mountain basin (Illgraben, Switzerland) where sediment is produced by hillslope landslides and exported out of the basin by debris flows and floods. We present the model setup, the calibration of the model for the period 2000 - 2009 and the application of SedCas to model sediment discharge in the Illgraben over the 19th and 20th centuries. SedCas conceptualizes the fluvial system as a spatially lumped cascade of connected reservoirs representing hillslope and channel storages where sediment goes through multiple cycles of storage and remobilization by surface runoff. Sediment input is drawn from a probability distribution of slope failures produced for the basin from a time series of DEMs and the model is driven by observed climate. The model includes all relevant hydrological processes that lead to runoff in an Alpine basin, such as snow cover accumulation, snowmelt, evapotranspiration, and soil water storage. Although the processes of sediment transfer and debris flow generation are described in a simplified manner, SedCas produces highly complex sediment discharge behavior which is driven by the availability of sediment and antecedent moisture (system memory) as well as triggering potential (climate). The model reproduces the first order properties of observed debris flows over the period 2000-2009 including their probability distribution, seasonal timing and probability of

  16. Mathematical modeling of sediment transport jn estuaries and coastal regions

    Institute of Scientific and Technical Information of China (English)

    窦国仁; 董凤舞; 窦希萍; 李禔来

    1995-01-01

    Based on the suspended sediment transport equation and transport capacity formula under the action of tidal currents and wind waves, a horizontal 2-D mathematical model of suspended sediment transport for estuaries and coastal regions is established. The verification of calculations shows that the sediment concentration distribution and sea bed deformation in the estuaries and coastal regions can be successfully simulated. Therefore, a new method for studying and solving the sediment problems in the estuarine and coastal engineering is presented.

  17. Sensing dissolved sediment porewater concentrations of persistent and bioaccumulative poolutants using disposable solid-phase microextraction fibers

    NARCIS (Netherlands)

    Mayer, P.; Vaes, W.H.J.; Wijnker, F.; Legierse, K.C.H.M.; Kraaij, R.H.; Tolls, J.; Hermens, J.L.M.

    2000-01-01

    Polymer coated glass fibers were applied as disposable samplers to measure dissolved concentrations of persistent and bioaccumulative pollutants (PBPs) in sediment porewater. The method is called matrix solid-phase microextraction (matrix-SPME), because it utilizes the entire sediment matrix as a re

  18. Spatial Modelling of Sediment Transport over the Upper Citarum Catchment

    Directory of Open Access Journals (Sweden)

    Poerbandono

    2006-05-01

    Full Text Available This paper discusses set up of a spatial model applied in Geographic Information System (GIS environment for predicting annual erosion rate and sediment yield of a watershed. The study area is situated in the Upper Citarum Catchment of West Java. Annual sediment yield is considered as product of erosion rate and sediment delivery ratio to be modelled under similar modeling tool. Sediment delivery ratio is estimated on the basis of sediment resident time. The modeling concept is based on the calculation of water flow velocity through sub-catchment surface, which is controlled by topography, rainfall, soil characteristics and various types of land use. Relating velocity to known distance across digital elevation model, sediment resident time can be estimated. Data from relevance authorities are used. Bearing in mind limited knowledge of some governing factors due to lack of observation, the result has shown the potential of GIS for spatially modeling regional sediment transport. Validation of model result is carried out by evaluating measured and computed total sediment yield at the main outlet. Computed total sediment yields for 1994 and 2001 are found to be 1.96×106 and 2.10×106tons/year. They deviate roughly 54 and 8% with respect to those measured in the field. Model response due to land use change observed in 2001 and 1994 is also recognised. Under presumably constant rainfall depth, an increase of overall average annual erosion rate of 11% resulted in an increase of overall average sediment yield of 7%.

  19. Numerical Modelling of Sediment Transport in Combined Sewer Systems

    DEFF Research Database (Denmark)

    Schlütter, Flemming

    A conceptual sediment transport model has been developed. Through a case study a comparison with other numerical models is performed.......A conceptual sediment transport model has been developed. Through a case study a comparison with other numerical models is performed....

  20. Molecular Modeling of Solid Fluid Phase Behavior

    Energy Technology Data Exchange (ETDEWEB)

    Peter A. Monson

    2007-12-20

    This report gives a summary of the achievements under DOE contract No. DOE/ER/14150 during the period September 1, 1990 to December 31, 2007. This project was concerned with the molecular modeling of solid-fluid equilibrium. The focus was on understanding how solid-fluid and solid-solid phase behavior are related to molecular structure, and the research program made a seminal contribution in this area. The project led to 34 journal articles, including a comprehensive review article published in Advances in Chemical Physics. The DOE funding supported the work of 5 Ph.D. students, 2 M.S. students and 5 postdoctoral researchers.

  1. Incorporation of Fine-Grained Sediment Erodibility Measurements into Sediment Transport Modeling, Capitol Lake, Washington

    Science.gov (United States)

    Stevens, Andrew W.; Gelfenbaum, Guy; Elias, Edwin; Jones, Craig

    2008-01-01

    Capitol Lake was created in 1951 with the construction of a concrete dam and control gate that prevented salt-water intrusion into the newly formed lake and regulated flow of the Deschutes River into southern Puget Sound. Physical processes associated with the former tidally dominated estuary were altered, and the dam structure itself likely caused an increase in retention of sediment flowing into the lake from the Deschutes River. Several efforts to manage sediment accumulation in the lake, including dredging and the construction of sediment traps upriver, failed to stop the lake from filling with sediment. The Deschutes Estuary Feasibility Study (DEFS) was carried out to evaluate the possibility of removing the dam and restoring estuarine processes as an alternative ongoing lake management. An important component of DEFS was the creation of a hydrodynamic and sediment transport model of the restored Deschutes Estuary. Results from model simulations indicated that estuarine processes would be restored under each of four restoration alternatives, and that over time, the restored estuary would have morphological features similar to the predam estuary. The model also predicted that after dam-removal, a large portion of the sediment eroded from the lake bottom would be deposited near the Port of Olympia and a marina located in lower Budd Inlet seaward of the present dam. The volume of sediment transported downstream was a critical piece of information that managers needed to estimate the total cost of the proposed restoration project. However, the ability of the model to predict the magnitude of sediment transport in general and, in particular, the volume of sediment deposition in the port and marina was limited by a lack of information on the erodibility of fine-grained sediments in Capitol Lake. Cores at several sites throughout Capitol Lake were collected between October 31 and November 1, 2007. The erodibility of sediments in the cores was later determined in the

  2. GEOCHEMICAL RECOGNITION OF SPILLED SEDIMENTS USED IN NUMERICAL MODEL VALIDATION

    Institute of Scientific and Technical Information of China (English)

    Jens R.VALEUR; Steen LOMHOLT; Christian KNUDSEN

    2004-01-01

    A fixed link (tunnel and bridge,in total 16 km) was constructed between Sweden and Denmark during 1995-2000.As part of the work,approximately 16 million tonnes of seabed materials (limestone and clay till) were dredged,and about 0.6 million tonnes of these were spilled in the water.Modelling of the spreading and sedimentation of the spilled sediments took place as part of the environmental monitoring of the construction activities.In order to verify the results of the numerical modelling of sediment spreading and sedimentation,a new method with the purpose of distinguishing between the spilled sediments and the naturally occurring sediments was developed.Because the spilled sediments tend to accumulate at the seabed in areas with natural sediments of the same size,it is difficult to separate these based purely on the physical properties.The new method is based on the geo-chemical differences between the natural sediment in the area and the spill.The basic properties used are the higher content of calcium carbonate material in the spill as compared to the natural sediments and the higher Ca/Sr ratio in the spill compared to shell fragments dominating the natural calcium carbonate deposition in the area.The reason for these differences is that carbonate derived from recent shell debris can be discriminated from Danien limestone,which is the material in which the majority of the dredging took place,on the basis of the Ca/Sr ratio being 488 in Danien Limestone and 237 in shell debris.The geochemical recognition of the origin of the sediments proved useful in separating the spilled from the naturally occurring sediments.Without this separation,validation of the modelling of accumulation of spilled sediments would not have been possible.The method has general validity and can be used in many situations where the origin ora given sediment is sought.

  3. Numerical Modelling Approaches for Sediment Transport in Sewer Systems

    DEFF Research Database (Denmark)

    Mark, Ole

    A study of the sediment transport processes in sewers has been carried out. Based on this study a mathematical modelling system has been developed to describe the transport processes of sediments and dissolved matter in sewer systems. The modelling system consists of three sub-models which...... constitute the basic modelling system necessary to give a discription of the most dominant physical transport processes concerning particles and dissolved matter in sewer systems: A surface model. An advection-dispersion model. A sediment transport model....

  4. Cellular Automata Model for Elastic Solid Material

    Institute of Scientific and Technical Information of China (English)

    DONG Yin-Feng; ZHANG Guang-Cai; XU Ai-Guo; GAN Yan-Biao

    2013-01-01

    The Cellular Automaton (CA) modeling and simulation of solid dynamics is a long-standing difficult problem.In this paper we present a new two-dimensional CA model for solid dynamics.In this model the solid body is represented by a set of white and black particles alternatively positioned in the x-and y-directions.The force acting on each particle is represented by the linear summation of relative displacements of the nearest-neighboring particles.The key technique in this new model is the construction of eight coefficient matrices.Theoretical and numerical analyses show that the present model can be mathematically described by a conservative system.So,it works for elastic material.In the continuum limit the CA model recovers the well-known Navier equation.The coefficient matrices are related to the shear module and Poisson ratio of the material body.Compared with previous CA model for solid body,this model realizes the natural coupling of deformations in the x-and y-directions.Consequently,the wave phenomena related to the Poisson ratio effects are successfully recovered.This work advances significantly the CA modeling and simulation in the field of computational solid dynamics.

  5. Total Suspended Solid Content And Sediment On The Bottom Surface Of Panimbang Water

    Directory of Open Access Journals (Sweden)

    Helfinalis

    2005-11-01

    Full Text Available The study of dynamics oceanography have been executed on June 2004 in the East season. Distribution of total suspended solid on the surface and bottom waters at the Estuary of Ciliman River is lower than Estuary of Cibungur River. Generally mud and silty mud of sediment on the bottom surface waters covered the western part of Panimbang beach. Gravel, silty sand and muddy sand with forams, fraction of mollust and corals found at the Southwest of the study area. In that area is also found many floating of Bagan Apung which is assumed as rich with fishes.

  6. Numerical modelling of erosion and sedimentation around offshore pipelines

    NARCIS (Netherlands)

    Beek, van F.A.; Wind, H.G.

    1990-01-01

    In this paper a numerical model is presented for the description of the erosion and sedimentation near pipelines on the sea bottom. The model is based on the Navier-Stokes equations and the equation of motion and continuity of sediment. The results of the simulations have been compared with the res

  7. Flow Through a Laboratory Sediment Sample by Computer Simulation Modeling

    Science.gov (United States)

    2006-09-07

    Flow through a laboratory sediment sample by computer simulation modeling R.B. Pandeya’b*, Allen H. Reeda, Edward Braithwaitea, Ray Seyfarth0, J.F...through a laboratory sediment sample by computer simulation modeling 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

  8. Modelling end-pumped solid state lasers

    NARCIS (Netherlands)

    Bernhardi, E.H.; Bollig, C.; Forbes, A.; Esser, M.J.D.; Wörhoff, K.; Agazzi, L.; Ismail, N.; Leijtens, X.

    2008-01-01

    The operation dynamics of end-pumped solid-state lasers are investigated by means of a spatially resolved numerical rate-equation model and a time-dependent analytical thermal model. The rate-equation model allows the optimization of parameters such as the output coupler transmission and gain medium

  9. Modeling sediment mobilization using a distributed hydrological model coupled with a bank stability model

    Science.gov (United States)

    Stryker, J.; Wemple, B.; Bomblies, A.

    2017-03-01

    In addition to surface erosion, stream bank erosion and failure contributes significant sediment and sediment-bound nutrients to receiving waters during high flow events. However, distributed and mechanistic simulation of stream bank sediment contribution to sediment loads in a watershed has not been achieved. Here we present a full coupling of existing distributed watershed and bank stability models and apply the resulting model to the Mad River in central Vermont. We fully coupled the Bank Stability and Toe Erosion Model (BSTEM) with the Distributed Hydrology Soil Vegetation Model (DHSVM) to allow the simulation of stream bank erosion and potential failure in a spatially explicit environment. We demonstrate the model's ability to simulate the impacts of unstable streams on sediment mobilization and transport within a watershed and discuss the model's capability to simulate watershed sediment loading under climate change. The calibrated model simulates total suspended sediment loads and reproduces variability in suspended sediment concentrations at watershed and subbasin outlets. In addition, characteristics such as land use and road-to-stream ratio of subbasins are shown to impact the relative proportions of sediment mobilized by overland erosion, erosion of roads, and stream bank erosion and failure in the subbasins and watershed. This coupled model will advance mechanistic simulation of suspended sediment mobilization and transport from watersheds, which will be particularly valuable for investigating the potential impacts of climate and land use changes, as well as extreme events.

  10. CFD modelling of solid propellant ignition

    OpenAIRE

    Lowe, C

    1996-01-01

    Solid propellant is the highly energetic fuel burnt in the combustion chamber of ballistic weapons. It is manufactured, for this purpose, in either granular or stick form. Internal ballistics describes the behavior within the combustion chamber throughout the ballistic cycle upto projectile exit from the muzzle of the gun barrel. Over the last twenty years this has been achieved by modelling the process using two-phase flow equations. The solid granules or sticks constitute ...

  11. A constitutive mechanical model for gas hydrate bearing sediments incorporating inelastic mechanisms

    KAUST Repository

    Sánchez, Marcelo

    2016-11-30

    Gas hydrate bearing sediments (HBS) are natural soils formed in permafrost and sub-marine settings where the temperature and pressure conditions are such that gas hydrates are stable. If these conditions shift from the hydrate stability zone, hydrates dissociate and move from the solid to the gas phase. Hydrate dissociation is accompanied by significant changes in sediment structure and strongly affects its mechanical behavior (e.g., sediment stiffenss, strength and dilatancy). The mechanical behavior of HBS is very complex and its modeling poses great challenges. This paper presents a new geomechanical model for hydrate bearing sediments. The model incorporates the concept of partition stress, plus a number of inelastic mechanisms proposed to capture the complex behavior of this type of soil. This constitutive model is especially well suited to simulate the behavior of HBS upon dissociation. The model was applied and validated against experimental data from triaxial and oedometric tests conducted on manufactured and natural specimens involving different hydrate saturation, hydrate morphology, and confinement conditions. Particular attention was paid to model the HBS behavior during hydrate dissociation under loading. The model performance was highly satisfactory in all the cases studied. It managed to properly capture the main features of HBS mechanical behavior and it also assisted to interpret the behavior of this type of sediment under different loading and hydrate conditions.

  12. Ratios of total suspended solids to suspended sediment concentrations by particle size

    Science.gov (United States)

    Selbig, W.R.; Bannerman, R.T.

    2011-01-01

    Wet-sieving sand-sized particles from a whole storm-water sample before splitting the sample into laboratory-prepared containers can reduce bias and improve the precision of suspended-sediment concentrations (SSC). Wet-sieving, however, may alter concentrations of total suspended solids (TSS) because the analytical method used to determine TSS may not have included the sediment retained on the sieves. Measuring TSS is still commonly used by environmental managers as a regulatory metric for solids in storm water. For this reason, a new method of correlating concentrations of TSS and SSC by particle size was used to develop a series of correction factors for SSC as a means to estimate TSS. In general, differences between TSS and SSC increased with greater particle size and higher sand content. Median correction factors to SSC ranged from 0.29 for particles larger than 500m to 0.85 for particles measuring from 32 to 63m. Great variability was observed in each fraction-a result of varying amounts of organic matter in the samples. Wide variability in organic content could reduce the transferability of the correction factors. ?? 2011 American Society of Civil Engineers.

  13. Theoretical Evaluation of the Sediment/Water Exchange Description in Generic Compartment Models (SimpleBox)

    DEFF Research Database (Denmark)

    Sørensen, P. B.; Fauser, P.; Carlsen, L.;

    It is shown how diffusion and deposition of solids drive the flux of substance between the water column and the sediment. The generic compartment models (Mackay type) use a one box model for the sediment in order to keep the calculations simple. However, when diffusion needs to be included...... in the calculations, the one box model needs to be evaluated in relation to a more complete solution of the differential equations for diffusion. General guidelines that are based on the system parameters are set up in order to establish the importance of diffusion and deposition respectively. These define the range...... where diffusion or deposition is negligible or where both processes must be included in order to describe the sediment-water substance exchange most appropriately....

  14. Two-phase modelling of equiaxed crystal sedimentation and thermomechanic stress development in the sedimented packed bed

    Science.gov (United States)

    Ludwig, A.; Vakhrushev, A.; Holzmann, T.; Wu, M.; Kharicha, A.

    2015-06-01

    During many industrial solidification processes equiaxed crystals form, grow and move. When those crystals are small they are carried by the melt, whereas when getting larger they sediment. As long as the volume fraction of crystals is below the packing limit, they are able to move relatively free. Crystals being backed in a so called packed bed form a semi-solid slurry, which may behave like a visco-plastic material. In addition, cooling-induced density increase of both, liquid and solid phases might lead to shrinkage of the whole casting domain. So deformation happens and gaps between casting and mold occur. In the present work, a two-phase Eulerian-Eulerian volume averaging model for describing the motion of equiaxed crystals in the melt is combined with a similar two-phase model for describing the dynamic of the packed bed. As constitutive equation for the solid skeleton in the packed bed Norton-Hoff law is applied. Shrinkage induced by density changes in the liquid or the solid phase is explicitly taken into account and handled by remeshing the calculation domain accordantly.

  15. Combustion response modeling for composite solid propellants

    Science.gov (United States)

    1977-01-01

    A computerized mathematical model of the combustion response function of composite solid propellants was developed with particular attention to the contributions of the solid phase heterogeneity. The one-dimensional model treats the solid phase as alternating layers of ammonium perchlorate and binder, with an exothermic melt layer at the surface. Solution of the Fourier heat equation in the solid provides temperature and heat flux distributions with space and time. The problem is solved by conserving the heat flux at the surface from that produced by a suitable model of the gas phase. An approximation of the BDP flame model is utilized to represent the gas phase. By the use of several reasonable assumptions, it is found that a significant portion of the problem can be solved in closed form. A method is presented by which the model can be applied to tetramodal particle size distributions. A computerized steady-state version of the model was completed, which served to validate the various approximations and lay a foundation for the combustion response modeling. The combustion response modeling was completed in a form which does not require an iterative solution, and some preliminary results were acquired.

  16. A general mixture model for sediment laden flows

    Science.gov (United States)

    Liang, Lixin; Yu, Xiping; Bombardelli, Fabián

    2017-09-01

    A mixture model for general description of sediment-laden flows is developed based on an Eulerian-Eulerian two-phase flow theory, with the aim at gaining computational speed in the prediction, but preserving the accuracy of the complete two-fluid model. The basic equations of the model include the mass and momentum conservation equations for the sediment-water mixture, and the mass conservation equation for sediment. However, a newly-obtained expression for the slip velocity between phases allows for the computation of the sediment motion, without the need of solving the momentum equation for sediment. The turbulent motion is represented for both the fluid and the particulate phases. A modified k-ε model is used to describe the fluid turbulence while an algebraic model is adopted for turbulent motion of particles. A two-dimensional finite difference method based on the SMAC scheme was used to numerically solve the mathematical model. The model is validated through simulations of fluid and suspended sediment motion in steady open-channel flows, both in equilibrium and non-equilibrium states, as well as in oscillatory flows. The computed sediment concentrations, horizontal velocity and turbulent kinetic energy of the mixture are all shown to be in good agreement with available experimental data, and importantly, this is done at a fraction of the computational efforts required by the complete two-fluid model.

  17. Solid-state NMR of the Yersinia pestis outer membrane protein Ail in lipid bilayer nanodiscs sedimented by ultracentrifugation

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Yi; Fujimoto, L. Miya; Yao, Yong; Marassi, Francesca M., E-mail: fmarassi@sbmri.org [Sanford-Burnham Medical Research Institute (United States)

    2015-04-15

    Solid-state NMR studies of sedimented soluble proteins has been developed recently as an attractive approach for overcoming the size limitations of solution NMR spectroscopy while bypassing the need for sample crystallization or precipitation (Bertini et al. Proc Natl Acad Sci USA 108(26):10396–10399, 2011). Inspired by the potential benefits of this method, we have investigated the ability to sediment lipid bilayer nanodiscs reconstituted with a membrane protein. In this study, we show that nanodiscs containing the outer membrane protein Ail from Yersinia pestis can be sedimented for solid-state NMR structural studies, without the need for precipitation or lyophilization. Optimized preparations of Ail in phospholipid nanodiscs support both the structure and the fibronectin binding activity of the protein. The same sample can be used for solution NMR, solid-state NMR and activity assays, facilitating structure–activity correlation experiments across a wide range of timescales.

  18. A model for microbial phosphorus cycling in bioturbated marine sediments

    DEFF Research Database (Denmark)

    Dale, Andrew W.; Boyle, R. A.; Lenton, Timothy M.

    2016-01-01

    A diagenetic model is used to simulate the diagenesis and burial of particulate organic carbon (Corg) and phosphorus (P) in marine sediments underlying anoxic versus oxic bottom waters. The latter are physically mixed by animals moving through the surface sediment (bioturbation) and ventilated by...

  19. Haptics-based dynamic implicit solid modeling.

    Science.gov (United States)

    Hua, Jing; Qin, Hong

    2004-01-01

    This paper systematically presents a novel, interactive solid modeling framework, Haptics-based Dynamic Implicit Solid Modeling, which is founded upon volumetric implicit functions and powerful physics-based modeling. In particular, we augment our modeling framework with a haptic mechanism in order to take advantage of additional realism associated with a 3D haptic interface. Our dynamic implicit solids are semi-algebraic sets of volumetric implicit functions and are governed by the principles of dynamics, hence responding to sculpting forces in a natural and predictable manner. In order to directly manipulate existing volumetric data sets as well as point clouds, we develop a hierarchical fitting algorithm to reconstruct and represent discrete data sets using our continuous implicit functions, which permit users to further design and edit those existing 3D models in real-time using a large variety of haptic and geometric toolkits, and visualize their interactive deformation at arbitrary resolution. The additional geometric and physical constraints afford more sophisticated control of the dynamic implicit solids. The versatility of our dynamic implicit modeling enables the user to easily modify both the geometry and the topology of modeled objects, while the inherent physical properties can offer an intuitive haptic interface for direct manipulation with force feedback.

  20. Flower solid modeling based on sketches

    Institute of Scientific and Technical Information of China (English)

    Zhan DING; Shu-chang XU; Xiu-zi YE; Yin ZHANG; San-yuan ZHANG

    2008-01-01

    In this paper we propose a method to model flowers of solid shape. Based on (Ijiri et al., 2005)'s method, we separate individual flower modeling and inflorescence modeling procedures into structure and geometry modeling. We incorporate interactive editing gestures to allow the user to edit structure parameters freely onto structure diagram. Furthermore, we use free-hand sketching techniques to allow users to create and edit 3D geometrical elements freely and easily. The final step is to automatically merge all independent 3D geometrical elements into a single waterproof mesh. Our experiments show that this solid modeling approach is promising. Using our approach, novice users can create vivid flower models easily and freely. The generated flower model is waterproof. It can have applications in visualization, animation, gaming, and toys and decorations if printed out on 3D rapid prototyping devices.

  1. Testing modelled hillslope sediment production using a low cost sediment trap

    Science.gov (United States)

    Borombovits, Daniel; Brooks, Andrew; Spencer, John; Pietsch, Tim; Olley, Jon

    2014-05-01

    This presentation seeks to describe the design and evaluation of a simple, low cost Hillslope Sediment Trap (HST) suitable for deployment in remote arid and semi-arid environments as detailed in a paired submission by Brooks et al. (currently under review, Catena S-13-00775 and S-13-00776). The HSTs consist of a robust, fenced enclosure from which a geofabric barrier is hung and attached to the ground, forming a wall and apron section, which is extended upslope in a U or V shape, depending on slope angle. Key considerations of the HST design include cost, ease of field transportation and construction, and low maintenance during deployment, as well as hydraulic considerations such as conductivity, effective filtration threshold for single and consecutive events, and overall sediment retention within the traps. The sediment trapping efficiency of the HSTs was tested through a series of laboratory flume experiments which showed that the traps will accurately sample the full particle size distribution of sediment mobilised on a given hillslope, with a suspended sediment (streams which drain into the Great Barrier Reef Lagoon. Using the empirical sediment yield data collected by the HSTs allowed the development of a locally calibrated hillslope erosion model, providing far more realistic predictions of erosion than have previously been employed. Total sediment yield was measured in 11 plots ranging in size from 0.1 to 1.9 ha across four main geologies in the Normanby catchment, with results ranging between 0.03 - 256 kg/ha/yr across two distinctly different wet seasons. When compared to the RUSLE modelled sediment yields determined for the same sites, plot scale metrics together provided values ranging from 1550 - 331730 kg/ha/yr. Depending on which modelled data is used, this represents an average ratio of over prediction by the RUSLE model (cf the measured rates for the same period) of between 12 to 13333 times. Reasons for the over-prediction are discussed in Brooks

  2. Sediment isotope tomography (SIT) model version 1

    Energy Technology Data Exchange (ETDEWEB)

    Carroll, J.; Abraham, J.D.

    1996-03-08

    Geochronology using {sup 210}Pb is the principal method used to quantify sediment accumulation in rapidly depositing aquatic environments such as lakes, estuaries, continental shelves, and submarine canyons. This method is based on the radioactive decay of {sup 210}Pb with depth in a column of sediment. The decay through time of {sup 210}Pb P(t) is governed by the exponential law P(t) = P{sub 0} exp( -{lambda}t) where P{sub 0} is the surficial concentration at time t = 0, and {lambda} is the decay constant (3.114 {sm_bullet} 10{sup -2} year [yr]{sup -1} for {sup 210}Pb). If the sedimentation rate is constant, then elapsed time t is connected to burial depth x, through x = Vt where V is the sedimentation velocity. Accordingly, P(x) = P{sub 0}exp( -{lambda}x/V). The sedimentation velocity is obtained from an exponential fit to the measured {sup 210}Pb data P(x), with depth x.

  3. Environmental modeling and exposure assessment of sediment-associated pyrethroids in an agricultural watershed.

    Directory of Open Access Journals (Sweden)

    Yuzhou Luo

    Full Text Available Synthetic pyrethroid insecticides have generated public concerns due to their increasing use and potential effects on aquatic ecosystems. A modeling system was developed in this study for simulating the transport processes and associated sediment toxicity of pyrethroids at coupled field/watershed scales. The model was tested in the Orestimba Creek watershed, an agriculturally intensive area in California' Central Valley. Model predictions were satisfactory when compared with measured suspended solid concentration (R(2 = 0.536, pyrethroid toxic unit (0.576, and cumulative mortality of Hyalella azteca (0.570. The results indicated that sediment toxicity in the study area was strongly related to the concentration of pyrethroids in bed sediment. Bifenthrin was identified as the dominant contributor to the sediment toxicity in recent years, accounting for 50-85% of predicted toxicity units. In addition, more than 90% of the variation on the annual maximum toxic unit of pyrethroids was attributed to precipitation and prior application of bifenthrin in the late irrigation season. As one of the first studies simulating the dynamics and spatial variability of pyrethroids in fields and instreams, the modeling results provided useful information on new policies to be considered with respect to pyrethroid regulation. This study suggested two potential measures to efficiently reduce sediment toxicity by pyrethroids in the study area: [1] limiting bifenthrin use immediately before rainfall season; and [2] implementing conservation practices to retain soil on cropland.

  4. Modeling long-term, large-scale sediment storage using a simple sediment budget approach

    Science.gov (United States)

    Naipal, Victoria; Reick, Christian; Van Oost, Kristof; Hoffmann, Thomas; Pongratz, Julia

    2016-05-01

    Currently, the anthropogenic perturbation of the biogeochemical cycles remains unquantified due to the poor representation of lateral fluxes of carbon and nutrients in Earth system models (ESMs). This lateral transport of carbon and nutrients between terrestrial ecosystems is strongly affected by accelerated soil erosion rates. However, the quantification of global soil erosion by rainfall and runoff, and the resulting redistribution is missing. This study aims at developing new tools and methods to estimate global soil erosion and redistribution by presenting and evaluating a new large-scale coarse-resolution sediment budget model that is compatible with ESMs. This model can simulate spatial patterns and long-term trends of soil redistribution in floodplains and on hillslopes, resulting from external forces such as climate and land use change. We applied the model to the Rhine catchment using climate and land cover data from the Max Planck Institute Earth System Model (MPI-ESM) for the last millennium (here AD 850-2005). Validation is done using observed Holocene sediment storage data and observed scaling between sediment storage and catchment area. We find that the model reproduces the spatial distribution of floodplain sediment storage and the scaling behavior for floodplains and hillslopes as found in observations. After analyzing the dependence of the scaling behavior on the main parameters of the model, we argue that the scaling is an emergent feature of the model and mainly dependent on the underlying topography. Furthermore, we find that land use change is the main contributor to the change in sediment storage in the Rhine catchment during the last millennium. Land use change also explains most of the temporal variability in sediment storage in floodplains and on hillslopes.

  5. Analytical model for flux saturation in sediment transport.

    Science.gov (United States)

    Pähtz, Thomas; Parteli, Eric J R; Kok, Jasper F; Herrmann, Hans J

    2014-05-01

    The transport of sediment by a fluid along the surface is responsible for dune formation, dust entrainment, and a rich diversity of patterns on the bottom of oceans, rivers, and planetary surfaces. Most previous models of sediment transport have focused on the equilibrium (or saturated) particle flux. However, the morphodynamics of sediment landscapes emerging due to surface transport of sediment is controlled by situations out of equilibrium. In particular, it is controlled by the saturation length characterizing the distance it takes for the particle flux to reach a new equilibrium after a change in flow conditions. The saturation of mass density of particles entrained into transport and the relaxation of particle and fluid velocities constitute the main relevant relaxation mechanisms leading to saturation of the sediment flux. Here we present a theoretical model for sediment transport which, for the first time, accounts for both these relaxation mechanisms and for the different types of sediment entrainment prevailing under different environmental conditions. Our analytical treatment allows us to derive a closed expression for the saturation length of sediment flux, which is general and thus can be applied under different physical conditions.

  6. Sediment Yield Modeling in a Large Scale Drainage Basin

    Science.gov (United States)

    Ali, K.; de Boer, D. H.

    2009-05-01

    This paper presents the findings of spatially distributed sediment yield modeling in the upper Indus River basin. Spatial erosion rates calculated by using the Thornes model at 1-kilometre spatial resolution and monthly time scale indicate that 87 % of the annual gross erosion takes place in the three summer months. The model predicts a total annual erosion rate of 868 million tons, which is approximately 4.5 times the long- term observed annual sediment yield of the basin. Sediment delivery ratios (SDR) are hypothesized to be a function of the travel time of surface runoff from catchment cells to the nearest downstream channel. Model results indicate that higher delivery ratios (SDR > 0.6) are found in 18 % of the basin area, mostly located in the high-relief sub-basins and in the areas around the Nanga Parbat Massif. The sediment delivery ratio is lower than 0.2 in 70 % of the basin area, predominantly in the low-relief sub-basins like the Shyok on the Tibetan Plateau. The predicted annual basin sediment yield is 244 million tons which compares reasonably to the measured value of 192.5 million tons. The average annual specific sediment yield in the basin is predicted as 1110 tons per square kilometre. Model evaluation based on accuracy statistics shows very good to satisfactory performance ratings for predicted monthly basin sediment yields and for mean annual sediment yields of 17 sub-basins. This modeling framework mainly requires global datasets, and hence can be used to predict erosion and sediment yield in other ungauged drainage basins.

  7. Sediment cascade modelling for stochastic torrential sediment transfers forecasting in a changing alpine climate

    Science.gov (United States)

    Rudaz, Benjamin; Bardou, Eric; Jaboyedoff, Michel

    2015-04-01

    Alpine ephemeral streams act as links between high altitude erosional processes, slope movements and valley-floor fluvial systems or fan storage. Anticipating future mass wasting from these systems is crucial for hazard mitigation measures. Torrential activity is highly stochastic, with punctual transfers separating long periods of calm, during which the system evolves internally and recharges. Changes can originate from diffuse (rock faces, sheet erosion of bared moraines), concentrated external sources (rock glacier front, slope instabilities) or internal transfers (bed incision or aggradation). The proposed sediment cascade model takes into account those different processes and calculates sediment transfer from the slope to the channel reaches, and then propagates sediments downstream. The two controlling parameters are precipitation series (generated from existing rain gauge data using Gumbel and Extreme Probability Distribution functions) and temperature (generated from local meteorological stations data and IPCC scenarios). Snow accumulation and melting, and thus runoff can then be determined for each subsystem, to account for different altitudes and expositions. External stocks and sediment sources have each a specific response to temperature and precipitation. For instance, production from rock faces is dependent on frost-thaw cycles, in addition to precipitations. On the other hand, landslide velocity, and thus sediment production is linked to precipitations over longer periods of time. Finally, rock glaciers react to long-term temperature trends, but are also prone to sudden release of material during extreme rain events. All those modules feed the main sediment cascade model, constructed around homogeneous torrent reaches, to and from which sediments are transported by debris flows and bedload transport events. These events are determined using a runoff/erosion curve, with a threshold determining the occurrence of debris flows in the system. If a debris

  8. Modeling the electrified solid-liquid interface

    DEFF Research Database (Denmark)

    Rossmeisl, Jan; Skulason, Egill; Björketun, Mårten;

    2008-01-01

    A detailed atomistic model based on density functional theory calculations is presented of the charged solid-electrolyte interface. Having protons solvated in a water bilayer outside a Pt(111) slab with excess electrons, we show how the interface capacitance is well described and how the work...

  9. Underflows in Lake Constance - Numerical Modeling, Instrumental Observations and Sediment Data

    Science.gov (United States)

    Eder, Magdalena; Wessels, Martin; Dare, Julian

    2014-05-01

    A torrential rain event in the western Alps in August 2005 caused high flood flows in the rivers Alpine Rhine and Bregenzer Ache which are the main tributaries into Lake Constance. The discharge of the Alpine Rhine reached 2200 m³/s, which is little below a centennial flood event. Discharge of the Bregenzer Ache was estimated to 1350 m³/s which statistically occurs every 100 yr but with a 1000 yr frequency in selected smaller tributaries. The high concentration of suspended solids in the fluvial water increased its density and created an underflow with considerable influence on the lake's hydrodynamics and water quality. Consequences within the lake were directly registered by a mooring (equipped with thermistor chain, sediment trap, current meter, oxygen sensor). Spatial data of the path and form of suspended matter cloud within the lake were gathered using echo sounder and probe measurements (turbidity, temperature, salinity). An underflow with a temperature of 14°C flew with 1.4 km/h some 20 km into the lake. Several days after the event, the fluvial sediments were detected as increased turbidity at the drinking water outtakes around the lake. Sediment cores recovered from the lake bottom show the distribution pattern of the sediments while sidescan data give a picture from proximal sediment structures originating from this event. Further, we modelled this underflow using the three dimensional hydrodynamic and water quality model ELCOM-CAEDYM. The suspended solids module of the model accounts for the impact of the sediment load on water density. Settling is considered using Stokes Law, and resuspension can also be included. The simulation of the August 2005 flood event and comparison with measured data impressively showed the ability to reproduce the most important effects of the flood flow on the lake. Comparative simulations with and without consideration of the coriolis effect indicate an influence of the coriolis force on the flow path of the density

  10. MODELING OF SEDIMENT AND NONPOINT SOURCE POLLUTANT YIELD

    Institute of Scientific and Technical Information of China (English)

    Huai'en LI; Xiaokang Hong; Bing SHEN

    2001-01-01

    For water and soil conservation and water pollution control, it is very important to simulate and predict the load of sediment and pollutant during storm-runoff. On the basis of analyzing the simultaneous measurements of flow, sediment and pollutants observed at watershed outlet, a practical sediment yield model is developed by standardizing the load rate. The results show that the standardized pollutant yield equals effective rainfall and the process of effective load yield is the same as effective rainfall hyetograph. Comparison with measured data show that this model is applicable to various pollutants.

  11. Benchmarking an unstructured grid sediment model in an energetic estuary

    Science.gov (United States)

    Lopez, Jesse E.; Baptista, António M.

    2017-02-01

    A sediment model coupled to the hydrodynamic model SELFE is validated against a benchmark combining a set of idealized tests and an application to a field-data rich energetic estuary. After sensitivity studies, model results for the idealized tests largely agree with previously reported results from other models in addition to analytical, semi-analytical, or laboratory results. Results of suspended sediment in an open channel test with fixed bottom are sensitive to turbulence closure and treatment for hydrodynamic bottom boundary. Results for the migration of a trench are very sensitive to critical stress and erosion rate, but largely insensitive to turbulence closure. The model is able to qualitatively represent sediment dynamics associated with estuarine turbidity maxima in an idealized estuary. Applied to the Columbia River estuary, the model qualitatively captures sediment dynamics observed by fixed stations and shipborne profiles. Representation of the vertical structure of suspended sediment degrades when stratification is underpredicted. Across all tests, skill metrics of suspended sediments lag those of hydrodynamics even when qualitatively representing dynamics. The benchmark is fully documented in an openly available repository to encourage unambiguous comparisons against other models.

  12. A parameter model for dredge plume sediment source terms

    Science.gov (United States)

    Decrop, Boudewijn; De Mulder, Tom; Toorman, Erik; Sas, Marc

    2017-01-01

    The presented model allows for fast simulations of the near-field behaviour of overflow dredging plumes. Overflow dredging plumes occur when dredging vessels employ a dropshaft release system to discharge the excess sea water, which is pumped into the trailing suction hopper dredger (TSHD) along with the dredged sediments. The fine sediment fraction in the loaded water-sediment mixture does not fully settle before it reaches the overflow shaft. By consequence, the released water contains a fine sediment fraction of time-varying concentration. The sediment grain size is in the range of clays, silt and fine sand; the sediment concentration varies roughly between 10 and 200 g/l in most cases, peaking at even higher value with short duration. In order to assess the environmental impact of the increased turbidity caused by this release, plume dispersion predictions are often carried out. These predictions are usually executed with a large-scale model covering a complete coastal zone, bay, or estuary. A source term of fine sediments is implemented in the hydrodynamic model to simulate the fine sediment dispersion. The large-scale model mesh resolution and governing equations, however, do not allow to simulate the near-field plume behaviour in the vicinity of the ship hull and propellers. Moreover, in the near-field, these plumes are under influence of buoyancy forces and air bubbles. The initial distribution of sediments is therefore unknown and has to be based on crude assumptions at present. The initial (vertical) distribution of the sediment source is indeed of great influence on the final far-field plume dispersion results. In order to study this near-field behaviour, a highly-detailed computationally fluid dynamics (CFD) model was developed. This model contains a realistic geometry of a dredging vessel, buoyancy effects, air bubbles and propeller action, and was validated earlier by comparing with field measurements. A CFD model requires significant simulation times

  13. Modelling of sediment movement in the surf and swash zones

    Institute of Scientific and Technical Information of China (English)

    TOKPOHOZIN N B; KOUNOUHEWA B; AVOSSEVOU G Y H; HOUEKPOHEHAM A; AWANOU C N

    2015-01-01

    Under the action of marine currents, non-cohesive sediments evolve by bed-load, by saltation or suspension depending on their granulometry. Several authors have considered that the movement of sediment is bidimensional and modelized the effects of swell by a constant velocitynear the seabed. Here we have studied the velocity profile of fluctuating currents near the seabed and studied the movement of sediment in 3D. The results show that in the areas of study (surf and swash) the movement of sediment occurs in a volume, and the evolution of sediment varies from an areato another. The obtained theoretical profiles of the position and velocity vectors confirm the observations of several authors.

  14. Modelling of Sediment Transport in Beris Fishery Port

    Directory of Open Access Journals (Sweden)

    Samira Ardani

    2015-06-01

    Full Text Available In this paper, the large amount of sedimentation and the resultant shoreline advancements at the breakwaters of Beris Fishery Port are studied. A series of numerical modeling of waves, sediment transport, and shoreline changes were conducted to predict the complicated equilibrium shoreline. The outputs show that the nearshore directions of wave components are not perpendicular to the coast which reveals the existence of longshore currents and consequently sediment transport along the bay. Considering the dynamic equilibrium condition of the bay, the effect of the existing sediment resources in the studied area is also investigated. The study also shows that in spite of the change of the diffraction point of Beris Bay after the construction of the fishery port, the bay is approaching its dynamic equilibrium condition, and the shoreline advancement behind secondary breakwater will stop before blocking the entrance of the port. The probable solutions to overcome the sedimentation problem at the main breakwater are also discussed.

  15. Non-Equilibrium Sediment Transport Modeling - Extensions and Applications

    Science.gov (United States)

    2013-01-01

    non-cohesive and cohesive sediment mixtures has been rarely studied, but have gained more and more attention recently ( Ziegler and Nisbet, 1995; Lin...the mud dry density, organic material, temperature, pH value, the Sodium Absorption Ratio (SAR), etc. Partheniades (1965) found n to be 1. In the...ASCE, 133(9), 1000–1009. Gailani, J., Ziegler , C.K., Lick , W., (1991). Transport of suspended solids in the Lower Fox River. Journal of Great

  16. Comparing Sediment Yield Predictions from Different Hydrologic Modeling Schemes

    Science.gov (United States)

    Dahl, T. A.; Kendall, A. D.; Hyndman, D. W.

    2015-12-01

    Sediment yield, or the delivery of sediment from the landscape to a river, is a difficult process to accurately model. It is primarily a function of hydrology and climate, but influenced by landcover and the underlying soils. These additional factors make it much more difficult to accurately model than water flow alone. It is not intuitive what impact different hydrologic modeling schemes may have on the prediction of sediment yield. Here, two implementations of the Modified Universal Soil Loss Equation (MUSLE) are compared to examine the effects of hydrologic model choice. Both the Soil and Water Assessment Tool (SWAT) and the Landscape Hydrology Model (LHM) utilize the MUSLE for calculating sediment yield. SWAT is a lumped parameter hydrologic model developed by the USDA, which is commonly used for predicting sediment yield. LHM is a fully distributed hydrologic model developed primarily for integrated surface and groundwater studies at the watershed to regional scale. SWAT and LHM models were developed and tested for two large, adjacent watersheds in the Great Lakes region; the Maumee River and the St. Joseph River. The models were run using a variety of single model and ensemble downscaled climate change scenarios from the Coupled Model Intercomparison Project 5 (CMIP5). The initial results of this comparison are discussed here.

  17. Solid partitioning and solid-liquid distribution of {sup 210}Po and {sup 210}Pb in marine anoxic sediments: roads of Cherbourg at the northwestern France

    Energy Technology Data Exchange (ETDEWEB)

    Connan, O. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France)], E-mail: olivier.connan@irsn.fr; Boust, D. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France); Billon, G. [Laboratoire de Chimie Analytique et Marine, Universite des sciences et technologies de Lille, 59655 Villeneuve d' Ascq Cedex (France); Solier, L.; Rozet, M.; Bouderbala, S. [Laboratoire de Radioecologie de Cherbourg-Octeville, Institut de Radioprotection et de Surete nucleaire (IRSN), Service d' Etudes et du Comportement des Radionucleides dans l' Environnement (SECRE), rue Max Pol Fouchet, 50130 Cherbourg-Octeville (France)

    2009-10-15

    A sequential extraction protocol has been used to determine the solid-phase partition of {sup 210}Po and {sup 210}Pb in anoxic marine sediment from the roads of Cherbourg (France) in the central English Channel. Measurements were also obtained in pore waters, in which {sup 210}Po activities range between 1 and 20 mBq L{sup -1} and {sup 210}Pb activities between 2.4 and 3.8 mBq L{sup -1}, with highest activities in the topmost layer. These activities are higher than in seawater, suggesting that sediment act as a source of both {sup 210}Po and {sup 210}Pb for overlying water. The {sup 210}Po profile in the pore waters is apparently correlated with those obtained for Fe, Mn and SO{sub 4}{sup 2-}, suggesting an influence of early diagenetic processes on the {sup 210}Po solid-liquid distribution. In the sediment, {sup 210}Po is predominantly bound to organic matter or chromium reducible sulphides, and residuals (clay minerals and refractory oxides). Our results indicate that {sup 210}Po is not significantly bound to AVS, i.e. acid volatile sulphides: bioturbation could play a role by the early redistribution of {sup 210}Po bound to acid volatile sulphides in the sediment. {sup 210}Po, {sup 210}Pb and Pb exhibit differences in terms of distribution, probably due to a different mode of penetration in the sediment. This work provides information on solid and liquid distribution of {sup 210}Po and {sup 210}Pb in marine sediment. These data are very scarce in the litterature.

  18. Spontaneous concentrations of solids through two-way drag forces between gas and sedimenting particles

    CERN Document Server

    Lambrechts, Michiel; Capelo, Holly L; Blum, Jürgen; Bodenschatz, Eberhard

    2016-01-01

    The behaviour of sedimenting particles depends on the dust-to-gas ratio of the fluid. Linear stability analysis shows that solids settling in the Epstein drag regime would remain homogeneously distributed in non-rotating incompressible fluids, even when dust-to-gas ratios reach unity. However, the non-linear evolution has not been probed before. Here, we present numerical calculations indicating that in a particle-dense mixture solids spontaneously mix out of the fluid and form swarms overdense in particles by at least a factor 10. The instability is caused by mass-loaded regions locally breaking the equilibrium background stratification. The driving mechanism depends on non-linear perturbations of the background flow and shares some similarity to the streaming instability in accretion discs. The resulting particle-rich swarms may stimulate particle growth by coagulation. In the context of protoplanetary discs, the instability could be relevant for aiding small particles to settle to the midplane in the outer...

  19. Spatial variability in floodplain sedimentation: the use of generalized linear mixed-effects models

    Directory of Open Access Journals (Sweden)

    A. Cabezas

    2010-02-01

    Full Text Available Sediment, Total Organic Carbon (TOC and total nitrogen (TN accumulation during one overbank flood (1.15 y were examined at one reach of the Middle Ebro River (NE Spain for elucidating spatial patterns. To achieve this goal, four areas with different geomorphological features and located within the study reach were examined by using artificial grass mats. Within each area, 1 m2 study plots consisting on three pseudo-replicates were placed in a semi-regular grid oriented perpendicular to the main channel. TOC, TN and Particle-Size composition of deposited sediments were examined and accumulation rates estimated. Generalized linear mixed-effects models were used to analyze sedimentation patterns in order to handle clustered sampling units, specific-site effects and spatial self-correlation between observations. Our results confirm the importance of channel-floodplain morphology and site micro-topography in explaining sediment, TOC and TN deposition patterns, although the importance of another factors as vegetation morphology should be included in further studies to explain small scale variability. Generalized linear mixed-effect models provide a good framework to deal with the high spatial heterogeneity of this phenomenon at different spatial scales, and should be further investigated in order to explore its validity when examining the importance of factors such as flood magnitude or suspended sediment solid concentration.

  20. Use of hydrochloric acid for determinining solid-phase arsenic partitioning in sulfidic sediments.

    Science.gov (United States)

    Wilkin, Richard T; Ford, Robert G

    2002-11-15

    We examined the use of room-temperature hydrochloric acid (1-6 M) and salt solutions of magnesium chloride, sodium carbonate, and sodium sulfide for the removal of arsenic from synthetic iron monosulfides and contaminated sediments containing acid-volatile sulfides (AVS). Results indicate that acid-soluble arsenic reacts with H2S released from AVS phases and precipitates at low pH as disordered orpiment or alacranite. Arsenic sulfide precipitation is consistent with geochemical modeling in that conditions during acid extraction are predicted to be oversaturated with respect to orpiment, realgar, or both. Binding of arsenic with sulfide at low pH is sufficiently strong that 6 M HCl will not keep spiked arsenic in the dissolved fraction. Over a wide range of AVS concentrations and molar [As]/[AVS] ratios, acid extraction of arsenic from sulfide-bearing sediments will give biased results that overestimate the stability or underestimate the bioavailability of sediment-bound arsenic. Alkaline solutions of sodium sulfide and sodium carbonate are efficient in removing arsenic from arsenic sulfides and mixed iron-arsenic sulfides because of the high solubility of arsenic at alkaline pH, the formation of stable arsenic complexes with sulfide or carbonate, or both.

  1. Numerical Modelling of Arctic Coastal Hydrodynamics and Sediment Transport

    OpenAIRE

    Borgersen, Benedicte T

    2016-01-01

    Coastal areas are experiencing an increase in human population and activities, both in temperate and in Arctic areas. This change in the coastal areas requires that the areas are safe and reliable in order to not put human lives and economical values in danger. To be about to protect the coastal areas it is important to know the hydrodynamics and sediment transport and their effect on coastal areas. Numerical modeling of coastal hydrodynamics and sediment transport is a normal approach to...

  2. Modelling the initial structure dynamics of soil and sediment exemplified for a constructed hydrological catchment

    Science.gov (United States)

    Maurer, Thomas; Schneider, Anna; Gerke, Horst H.

    2016-04-01

    The structure of a hydrological catchment is determined by the geometry of the boundaries and the spatial distribution of soil and sediment properties. Models of the 3D subsurface structure and the soil heterogeneity have often been built based on geostatistical approaches and conditional simulations for spatial interpolation between measurements. Here, an alternative model was proposed that generated 3D subsurface structures by imitating basic structures resulting from mass distribution processes. Instead of directly assuming stochastic variations of the subsurface structure, the present approach assumed stochastic variations in parameters of the process-based algorithms of the generator models. The constructed hydrological catchment "Hühnerwasser" located in the Lower Lusatia region of Brandenburg, Germany, was used as an example for the development of such a 3D structure generator model. Boundary geometries and changes in the surface topography due to erosion and sedimentation processes were quantified on the basis of digital elevation models (DEMs) derived from aerial photographs and terrestrial laser scanning information. Basic sediment properties came i) from a geological model of the parent material at the outcrop site, ii) from actual soil sample measurements on-site, and iii) based on stochastic texture variations. Sediment distributions were generated according to construction processes such as sediment dumping, particle segregation, and soil compaction. The resulting internal structures reflect the formation of spoil cones and surface compaction by machinery. The simulated 3D model scenarios of soil texture and bulk density distributions were incorporated in a gridded 3D volume model using the 3D software tool GoCAD (Paradigm Ltd.). This 3D distributed solid phase structure of the catchment allowed for a more direct comparison with observations using minimal invasive methods. By including structural changes over time (e.g., derived from DEM

  3. A DIAGENETIC MODEL FOR SEDIMENT-SEAGRASS INTERACTIONS

    Science.gov (United States)

    The objective of this modeling effort was to better understand the dynamic relationship between seagrass beds and their sedimentary environment using a diagenetic model. The model was developed and optimized for sediments in the Laguna Madre, TX, which is one of the world's larg...

  4. Modelling sediment transport processes in macro-tidal estuary

    Institute of Scientific and Technical Information of China (English)

    Rauen; William; B.

    2009-01-01

    This paper outlines a numerical modeling study to predict the sediment transport processes in a macro-tidal estuary, namely the Mersey Estuary, UK. An integrated numerical model study is conducted to investigate the interaction between the hydrodynamic, morphological and sediment transport processes occurring in the estuary. The numerical model widely used in environmental sediment transport studies worldwide, namely ECOMSED is used to simulate flow and sediment transport in estuary. A wetting and drying scheme is proposed and applied to the model, which defines "dry" cells as regions with a thin film of fluid O (cm). The primitive equations are solved in the thin film as well as in other regular wet cells. A model for the bed load transport is included in the code to account for the dynamics of the mobile bed boundary. The bed evolution due to bed load transport which is calculated according to van Rijn (1984a) is obtained by solving the sediment mass-balance equation. An estuary-related laboratory flume experiment is used to verify the model. Six sets of field measured hydrodynamic data are used to verify the corresponding predictions of the model, with the model-predicted water elevations and salinity levels generally agreeing well with the field measurements. The numerical model results show that in the Mersey Estuary both the tidal level and river discharge affect significantly the sediment transport. Reasonable agreement between the model results and field data has been obtained, indicating that the model can be used as computer-based tool for the environment management of estuarine system.

  5. SEDIMENT YIELD MODELING FOR SINGLE STORM EVENTS BASED ON HEAVY-DISCHARGE STAGE CHARACTERIZED BY STABLE SEDIMENT CONCENTRATION

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The relation between runoff volume and sediment yield for individual events in a given watershed receives little attention compared to the relation between water discharge and sediment yield, though it may underlie the event-based sediment-yield model for large-size watershed. The data observed at 12 experimental subwatersheds in the Dalihe river watershed in hilly areas of Loess Plateau, North China,was selected to develop and validate the relation. The peak flow is often considered as an important factor affecting event sediment yield. However, in the study areas, sediment concentration remains relatively constant when water discharge exceeds a certain critical value, implying that the heavier flow is not accompanied with the higher sediment transport capacity. Hence, only the runoff volume factor was considered in the sediment-yield model. As both the total sediment and runoff discharge were largely produced during the heavy-discharge stage, and the sediment concentration was negligibly variable during this stage, a proportional function can be used to model the relation between event runoff volume and sediment yield for a given subwatershed. The applicability of this model at larger spatial scales was also discussed, and it was found that for the Yaoxinzhuang station at the Puhe River basin, which controls a drainage area of 2264km2, a directly proportional relation between event runoff volume and sediment yield may also exist.

  6. Occurrence and persistence of fungicides in bed sediments and suspended solids from three targeted use areas in the United States.

    Science.gov (United States)

    Smalling, Kelly L; Reilly, Timothy J; Sandstrom, Mark W; Kuivila, Kathryn M

    2013-03-01

    To document the environmental occurrence and persistence of fungicides, a robust and sensitive analytical method was used to measure 34 fungicides and an additional 57 current-use pesticides in bed sediments and suspended solids collected from areas of intense fungicide use within three geographic areas across the United States. Sampling sites were selected near or within agricultural research farms using prophylactic fungicides at rates and types typical of their geographic location. At least two fungicides were detected in 55% of the bed and 83% of the suspended solid samples and were detected in conjunction with herbicides and insecticides. Six fungicides were detected in all samples including pyraclostrobin (75%), boscalid (53%), chlorothalonil (41%) and zoxamide (22%). Pyraclostrobin, a strobilurin fungicide, used frequently in the United States on a variety of crops, was detected more frequently than p,p'-DDE, the primary degradate of p,p'-DDT, which is typically one of the most frequently occurring pesticides in sediments collected within highly agricultural areas. Maximum fungicide concentrations in bed sediments and suspended solids were 198 and 56.7 μg/kg dry weight, respectively. There is limited information on the occurrence, fate, and persistence of many fungicides in sediment and the environmental impacts are largely unknown. The results of this study indicate the importance of documenting the persistence of fungicides in the environment and the need for a better understanding of off-site transport mechanisms, particularly in areas where crops are grown that require frequent treatments to prevent fungal diseases.

  7. Effect of sediment turbidity and color on light output measurement for Microtox Basic Solid-Phase Test.

    Science.gov (United States)

    Campisi, T; Abbondanzi, F; Casado-Martinez, C; DelValls, T A; Guerra, R; Iacondini, A

    2005-06-01

    In this work, sediment samples collected from several Spanish harbours were tested with two toxicity procedures, designed for solid samples: the Microtox Basic Solid-Phase Test (BSPT) and a modified procedure of the previous test protocol (mBSPT). According to the BSPT procedure, after initial light readings, pure bacteria were exposed to sediment suspension dilutions and light production was directly measured on suspended sediments without any further manipulation. As measurements are likely to be affected by sediment turbidity and color, a variation in initial light measurement has been here suggested, in order to consider the sample effect at all time readings during the test. Firstly, when sediment suspensions at different concentrations were added to bacteria suspension, immediately the initial light output drastically decayed by more than 50% in signal difference, resulting in a false inhibition, as effect of sample turbidity/color. This effect was more evident at high EC50 values, when slightly or not toxic samples were assessed. Secondly, the comparison of the EC50 obtained with both procedures, demonstrated that the mBSPT produced higher EC50 values (less toxic) than those obtained with the standard procedure. The mBSPT procedure resulted rapid and effective and it could be applied simultaneously with BSPT, in order to better evaluate the toxicity.

  8. Resuspended contaminated sediments cause sublethal stress to oysters: A biomarker differentiates total suspended solids and contaminant effects.

    Science.gov (United States)

    Edge, Katelyn J; Dafforn, Katherine A; Simpson, Stuart L; Ringwood, Amy H; Johnston, Emma L

    2015-06-01

    Resuspended contaminated sediments represent an important route of contaminant exposure for aquatic organisms. During resuspension events, filter-feeding organisms are exposed to contaminants, in both the dissolved form (at the gills) and the particulate form (in the digestive system). In addition, these organisms must manage the physical stress associated with an increase in total suspended solids (TSS). To date, few studies have experimentally compared the contributions to biological stress of contaminated and clean suspended solids. The authors mixed field-collected sediments (<63 μm) from clean and contaminated field sites to create 4 treatments of increasing metal concentrations. Sydney rock oysters were then exposed to sediment treatments at different TSS concentrations for 4 d, and cellular biomarkers (lysosomal membrane stability, lipid peroxidation, and glutathione) were measured to evaluate sublethal toxicity. Lysosomal membrane stability was the most sensitive biomarker for distinguishing effects from resuspended contaminated sediments, as increasing amounts of contaminated TSS increased lysosomal membrane destabilization. The authors' results illustrate the importance of considering contaminant exposures from resuspended sediments when assessing the toxicity of contaminants to aquatic organisms. © 2015 SETAC.

  9. Confirmatory chemical analyses and solid phase bioassays on sediment from the Columbia River Estuary at Tongue Point, Oregon

    Energy Technology Data Exchange (ETDEWEB)

    Young, J.S.; Word, J.Q.; Apts, C.W.; Barrows, M.E.; Cullinan, V.I.; Kohn, N.P.

    1988-12-01

    The Department of Economic Development, Ports Division, of the state of Oregon plans to develop a former ship supply and storage site near Tongue Point, Oregon, for commercial shipping. The development would require dredging the adjacent waterway to the Columbia River 40-foot channel to admit commercials vessels. The Portland District of the US Army Corps of Engineers requested the Battelle/Marine Sciences Laboratory (MSL) to conduct confirmatory solid-phase bioassays that would provide technical data for an evaluation of the potential environmental impact of ocean disposal of the dredged material. These confirmatory studies provided chemical and biological information required by ocean dumping regulations to determine suitability of Tongue Point sediments for ocean disposal. Sediment core samples were collected from Cathlamet Bay at Tongue Point in the upper Columbia River estuary. Sediment surface grab samples were collected at reference/control sites offshore from the mouth of the Columbia River (Disposal Site F) and at West Beach, Whidbey Island, Washington. The Tongue Point sediments were mixed into two composited batches. The MSL conducted solid-phase bioassays with these composites and reference sediments on four species of organisms.

  10. Sediment Transport Dynamics in River Networks: A Model for Higher-Water Seasons

    Science.gov (United States)

    Huo, Jie; Wang, Xu-Ming; Hao, Rui; Zhang, Jin-Feng

    A dynamical model is proposed to study sediment transport in river networks in higher-water seasons. The model emphasizes the difference between the sediment-carrying capability of the stream in higher-water seasons and that in lower-water seasons. The dynamics of sediment transport shows some complexities such as the complex dependence of the sediment-carrying capability on sediment concentration, the response of the channel(via erosion or sedimentation) to the changes of discharge.

  11. Particle tracking modeling of sediment-laden jets

    Science.gov (United States)

    Chan, S. N.; Lee, J. H. W.

    2014-06-01

    This paper presents a general model to predict the particulate transport and deposition from a sediment-laden horizontal momentum jet. A three-dimensional (3-D) stochastic particle tracking model is developed based on the governing equation of particle motion. The turbulent velocity fluctuations are modelled by a Lagrangian velocity autocorrelation function that captures the trapping of sediment particles in turbulent eddies, which result in the reduction of settling velocity. Using classical solutions of mean jet velocity, and turbulent fluctuation and dissipation rate profiles derived from computational fluid dynamics calculations of a pure jet, the equation of motion is solved numerically to track the particle movement in the jet flow field. The 3-D particle tracking model predictions of sediment deposition and concentration profiles are in excellent agreement with measured data. The computationally demanding Basset history force is shown to be negligible in the prediction of bottom deposition profiles.

  12. Two-dimensional sediment transport modeling for reservoir sediment management: Reventazón River, Costa Rica

    Science.gov (United States)

    Dubinski, I. M.

    2012-12-01

    Sedimentation is an ongoing concern for reservoirs that may be addressed using a variety of sediment management options. Sedimentation in reservoirs reduces reservoir storage and alters the sediment supply downstream. The objective of this study is to estimate the spatial and temporal distribution of deposited sediment in a proposed reservoir in the Reventazón River, Costa Rica over long-term operation (40 years) under different sediment management scenarios. The two-dimensional sediment transport model MIKE 21C by DHI is used to simulate sediment deposition for the base case (i.e., no sediment management) and assess the anticipated effectiveness of two sediment management strategies (i.e., full drawdown flushing and partial drawdown flushing). Incoming total sediment load is estimated using measured and estimated suspended sediment load combined with bed load estimated using the BAGS model with the Wilcock and Crowe (2003) equation. The base case simulation indicates that the anticipated storage loss in the absence of sediment management would amount to about 35% of the total and 33% of the active storage volume over a 40-year period. The predicted storage losses are significantly less when the performance of full drawdown flushing and partial drawdown flushing was simulated. In the case of full drawdown flushing the total anticipated storage loss is about 22%, while the loss in active storage is only 7%. In the case of partial drawdown flushing the predicted loss in total storage is 26%, while the anticipated loss in active storage is 8% after 40 years of operation. The simulations indicate that flushing is a viable and sustainable sediment management option for maintaining active storage in the proposed reservoir and passing through sediment.

  13. Sensitivity analysis of fine sediment models using heterogeneous data

    Science.gov (United States)

    Kamel, A. M. Yousif; Bhattacharya, B.; El Serafy, G. Y.; van Kessel, T.; Solomatine, D. P.

    2012-04-01

    Sediments play an important role in many aquatic systems. Their transportation and deposition has significant implication on morphology, navigability and water quality. Understanding the dynamics of sediment transportation in time and space is therefore important in drawing interventions and making management decisions. This research is related to the fine sediment dynamics in the Dutch coastal zone, which is subject to human interference through constructions, fishing, navigation, sand mining, etc. These activities do affect the natural flow of sediments and sometimes lead to environmental concerns or affect the siltation rates in harbours and fairways. Numerical models are widely used in studying fine sediment processes. Accuracy of numerical models depends upon the estimation of model parameters through calibration. Studying the model uncertainty related to these parameters is important in improving the spatio-temporal prediction of suspended particulate matter (SPM) concentrations, and determining the limits of their accuracy. This research deals with the analysis of a 3D numerical model of North Sea covering the Dutch coast using the Delft3D modelling tool (developed at Deltares, The Netherlands). The methodology in this research was divided into three main phases. The first phase focused on analysing the performance of the numerical model in simulating SPM concentrations near the Dutch coast by comparing the model predictions with SPM concentrations estimated from NASA's MODIS sensors at different time scales. The second phase focused on carrying out a sensitivity analysis of model parameters. Four model parameters were identified for the uncertainty and sensitivity analysis: the sedimentation velocity, the critical shear stress above which re-suspension occurs, the shields shear stress for re-suspension pick-up, and the re-suspension pick-up factor. By adopting different values of these parameters the numerical model was run and a comparison between the

  14. Evaluation of 10 cross-shore sediment transport morphological models

    CSIR Research Space (South Africa)

    Schoonees, JS

    1995-05-01

    Full Text Available Cross-shore sediment transport models are used to model beach profile changes in order to determine, for example, coastal set-back lines, behaviour of beach fill and beach profile variations adjacent to coastal structures. A study was undertaken...

  15. Polonium content in sediments and other solid tailings generated by mining industry

    Energy Technology Data Exchange (ETDEWEB)

    Chmielewska, Izabela; Michalik, Boguslaw [Silesian Centre for Environmental Radioactivity, Central Mining Institute, 40-166 Katowice, Pl. Gwarkow 1 (Poland)

    2014-07-01

    All legal limits or recommendations concerning NORM include only primordial radionuclides and secular equilibrium state among all decay products is assumed. This is not valid for a majority of residues from NORM industry where activity concentration of progenies can substantially differ each other. Upper Silesia Coal Basin is a unique region where mining activity is continuously done over longer period of time and this include discharging of radium-bearing water to environment and creating huge amount of solid wastes where at the beginning radium is the most dominant radionuclide. With time other daughter products start to build up and actual exposure to radiation is changing. One of them is polonium that with regard to its chemical properties can be easily accumulated in non-human biota resulting in the increase of radiation exposure. In our work we focused attention on sediments where content of {sup 210}Po was determined by chemical separation followed by alpha spectrometry. Chemical preparation involves organic matter destruction and dissolution of the sample itself (if possible). In our research we employed wet digestion by means of mixture of concentrated acids: HNO{sub 3}, HClO{sub 4}, HCl. Later on polonium was spontaneously deposited onto silver disc and measured with use of alpha spectrometry. In this article we want to show results of our study and as well to present some conclusions concerning changes in radiation risk assessment when actual concentration of polonium is taken into consideration. (authors)

  16. Solid mechanics theory, modeling, and problems

    CERN Document Server

    Bertram, Albrecht

    2015-01-01

    This textbook offers an introduction to modeling the mechanical behavior of solids within continuum mechanics and thermodynamics. To illustrate the fundamental principles, the book starts with an overview of the most important models in one dimension. Tensor calculus, which is called for in three-dimensional modeling, is concisely presented in the second part of the book. Once the reader is equipped with these essential mathematical tools, the third part of the book develops the foundations of continuum mechanics right from the beginning. Lastly, the book’s fourth part focuses on modeling the mechanics of materials and in particular elasticity, viscoelasticity and plasticity. Intended as an introductory textbook for students and for professionals interested in self-study, it also features numerous worked-out examples to aid in understanding.

  17. Inference-based procedural modeling of solids

    KAUST Repository

    Biggers, Keith

    2011-11-01

    As virtual environments become larger and more complex, there is an increasing need for more automated construction algorithms to support the development process. We present an approach for modeling solids by combining prior examples with a simple sketch. Our algorithm uses an inference-based approach to incrementally fit patches together in a consistent fashion to define the boundary of an object. This algorithm samples and extracts surface patches from input models, and develops a Petri net structure that describes the relationship between patches along an imposed parameterization. Then, given a new parameterized line or curve, we use the Petri net to logically fit patches together in a manner consistent with the input model. This allows us to easily construct objects of varying sizes and configurations using arbitrary articulation, repetition, and interchanging of parts. The result of our process is a solid model representation of the constructed object that can be integrated into a simulation-based environment. © 2011 Elsevier Ltd. All rights reserved.

  18. Numerical Model of Turbulence, Sediment Transport, and Sediment Cover in a Large Canyon-Bound River

    Science.gov (United States)

    Alvarez, L. V.; Schmeeckle, M. W.

    2013-12-01

    The Colorado River in Grand Canyon is confined by bedrock and coarse-grained sediments. Finer grain sizes are supply limited, and sandbars primarily occur in lateral separation eddies downstream of coarse-grained tributary debris fans. These sandbars are important resources for native fish, recreational boaters, and as a source of aeolian transport preventing the erosion of archaeological resources by gully extension. Relatively accurate prediction of deposition and, especially, erosion of these sandbar beaches has proven difficult using two- and three-dimensional, time-averaged morphodynamic models. We present a parallelized, three-dimensional, turbulence-resolving model using the Detached-Eddy Simulation (DES) technique. DES is a hybrid large eddy simulation (LES) and Reynolds-averaged Navier Stokes (RANS). RANS is applied to the near-bed grid cells, where grid resolution is not sufficient to fully resolve wall turbulence. LES is applied further from the bed and banks. We utilize the Spalart-Allmaras one equation turbulence closure with a rough wall extension. The model resolves large-scale turbulence using DES and simultaneously integrates the suspended sediment advection-diffusion equation. The Smith and McLean suspended sediment boundary condition is used to calculate the upward and downward settling of sediment fluxes in the grid cells attached to the bed. The model calculates the entrainment of five grain sizes at every time step using a mixing layer model. Where the mixing layer depth becomes zero, the net entrainment is zero or negative. As such, the model is able to predict the exposure and burial of bedrock and coarse-grained surfaces by fine-grained sediments. A separate program was written to automatically construct the computational domain between the water surface and a triangulated surface of a digital elevation model of the given river reach. Model results compare favorably with ADCP measurements of flow taken on the Colorado River in Grand Canyon

  19. The Chameleon Solid Rocket Propulsion Model

    Science.gov (United States)

    Robertson, Glen A.

    2010-01-01

    The Khoury and Weltman (2004a and 2004b) Chameleon Model presents an addition to the gravitation force and was shown by the author (Robertson, 2009a and 2009b) to present a new means by which one can view other forces in the Universe. The Chameleon Model is basically a density-dependent model and while the idea is not new, this model is novel in that densities in the Universe to include the vacuum of space are viewed as scalar fields. Such an analogy gives the Chameleon scalar field, dark energy/dark matter like characteristics; fitting well within cosmological expansion theories. In respect to this forum, in this paper, it is shown how the Chameleon Model can be used to derive the thrust of a solid rocket motor. This presents a first step toward the development of new propulsion models using density variations verse mass ejection as the mechanism for thrust. Further, through the Chameleon Model connection, these new propulsion models can be tied to dark energy/dark matter toward new space propulsion systems utilizing the vacuum scalar field in a way understandable by engineers, the key toward the development of such systems. This paper provides corrections to the Chameleon rocket model in Robertson (2009b).

  20. Wax Precipitation Modeled with Many Mixed Solid Phases

    DEFF Research Database (Denmark)

    Heidemann, Robert A.; Madsen, Jesper; Stenby, Erling Halfdan

    2005-01-01

    The behavior of the Coutinho UNIQUAC model for solid wax phases has been examined. The model can produce as many mixed solid phases as the number of waxy components. In binary mixtures, the solid rich in the lighter component contains little of the heavier component but the second phase shows sub...

  1. Numerical modelling of sediment transport in the Adriatic Sea

    Directory of Open Access Journals (Sweden)

    A. Guarnieri

    2014-06-01

    Full Text Available A new sediment transport model, considering currents, tides and waves is presented for the Adriatic Sea basin. The simulations concentrate on the winter of 2002–2003 because of field data availability and interesting intermittent processes occurrence. A process oriented analysis is performed to investigate the impact that Sirocco and Bora wind regimes have on sediment transport. The comparisons of the simulations with the observed data show that the model is capable to capture the main dynamics of sediment transport along the Italian coasts and the sediment concentration within the water column. This latter can reach values up to several g L−1, especially within the first centimetres above the bottom. The sediments are transported mainly southwards along the Italian coasts, consistently with the known literature results, except during Sirocco wind events, which can be responsible for reversing the coastal circulation in the northern area of the basin, and consequently the sediment transport. The resuspension of sediments is also related to the specific wave regimes induced by Bora and Sirocco, the former inducing resuspension events near the coasts while the latter causing a more diffused resuspension regime in the Northern Adriatic basin. Beside the realistic representation of short timescales resuspension/deposition events due to storms, the model was also used to investigate persistent erosion or deposition areas in the Adriatic Sea. Two main depocenters were identified: one, very pronounced, in the surroundings of the Po river delta, and another one a few kilometres off the coast in front of the Ancona promontory. A third region of accumulation, even if less intense, was found to be offshore the southernmost limit of the Gargano region. On the contrary the whole western coast within a distance of a few kilometres from the shore was found to be subject to prevailing erosion. The comparison with observed accumulation and erosion data shows

  2. Modelling transport of graded sediment under partial transport conditions

    NARCIS (Netherlands)

    Tuijnder, Arjan; Ribberink, Jan S.; Hulscher, Suzanne J.M.H.; Weerts, H.J.T.; Ritsema, I.L; van Os, A.G.

    2006-01-01

    Tentative plans are presented for research on the modelling of i) selective sediment transport in suspension and as bed-load, and ii) large-scale morphology in mixed sand-gravel bed rivers. Since the planning of the research is still in its early stages, the plans are flexible. Please feel free to

  3. Solid/liquid partition coefficients (Kd) for selected soils and sediments at Forsmark and Laxemar-Simpevarp

    Energy Technology Data Exchange (ETDEWEB)

    Sheppard, Steve; Long, Jeff; Sanipelli, Barb (ECOMatters Inc., Pinawa (Canada)); Sohlenius, Gustav (Geological Survey of Sweden (SGU), Uppsala (Sweden))

    2009-03-15

    Soil and sediment solid/liquid partition coefficients (Kd) are used to indicate the relative mobility of radionuclides and elements of concern from nuclear fuel waste, as well as from other sources. The Kd data are inherently extremely variable, but also vary systematically with key environmental attributes. For soil Kd, the key variables are pH, clay content and organic carbon content. For sediment Kd, water type (freshwater versus marine) and sediment type (benthic versus suspended) are important. This report summarized Kd data for soils and sediments computed from indigenous stable element concentrations measured at the Forsmark and Laxemar-Simpevarp sites. These were then compared to several literature sources of Kd data for Ce, Cl, Co, Cr, Cs, Fe, Ho, I, La, Mn, Mo, Nb, Nd, Ni, Np, Pa, Pb, Pu, Ra, Sb, Se, Sm, Sn, Sr, Tc, Th, Tm, U and Yb. The Kd data computed from indigenous stable element concentrations may be especially relevant for assessment of long-lived radionuclides from deep disposal of waste, because the long time frame for the potential releases is more consistent with the steady state measured using indigenous stable elements. For almost every one of these elements in soils, a statistically meaningful regression equation was developed to allow estimation of Kd for any soil given a modest amount of information about the soil. Nonetheless, the median residual geometric standard deviation (GSD) was 4.3-fold, implying confidence bounds of about 18-fold above and below the best estimate Kd. For sediment, the values are categorised simply by water type and sediment type. The median GSD for sediment Kd as measured at the Forsmark and Laxemar-Simpevarp sites was 2.5-fold, but the median GSD among literature values was as high as 8.6-fold. Clearly, there remains considerable uncertainty in Kd values, and it is important to account for this in assessment applications

  4. Complexities in coastal sediment transport studies by numerical modelling

    Digital Repository Service at National Institute of Oceanography (India)

    Ilangovan, D.; ManiMurali, R.

    stream_size 10748 stream_content_type text/plain stream_name Proc_Int_Conf_APAC_2013_364.pdf.txt stream_source_info Proc_Int_Conf_APAC_2013_364.pdf.txt Content-Encoding UTF-8 Content-Type text/plain; charset=UTF-8 Procee... could under estimate or over estimate the quantity of sediment transport and the result may not help to predict either erosion or accrction over a coastal region. CONCLUSIONS The authors conclude that sediment transport modelers need a thorough and long...

  5. Modelling of Heat Transfer at the Solid to Solid Interface

    Directory of Open Access Journals (Sweden)

    Rywotycki M.

    2016-03-01

    Full Text Available In technological process of steel industry heat transfer is a very important factor. Heat transfer plays an essential role especially in rolling and forging processes. Heat flux between a tool and work piece is a function of temperature, pressure and time. A methodology for the determination of the heat transfer at solid to solid interface has been developed. It involves physical experiment and numerical methods. The first one requires measurements of the temperature variations at specified points in the two samples brought into contact. Samples made of C45 and NC6 steels have been employed in physical experiment. One of the samples was heated to an initial temperature of: 800°C, 1000°C and 1100°C. The second sample has been kept at room temperature. The numerical part makes use of the inverse method for calculating the heat flux and at the interface. The method involves the temperature field simulation in the axially symmetrical samples. The objective function is bulled up as a dimensionless error norm between measured and computed temperatures. The variable metric method is employed in the objective function minimization. The heat transfer coefficient variation in time at the boundary surface is approximated by cubic spline functions.

  6. Assessing past and present P Retention in Sediments in Lake Ontario (Bay of Quinte) by Reaction-Transport Diagenetic Modeling

    Science.gov (United States)

    Doan, Phuong; Berry, Sandra; Markovic, Stefan; Watson, Sue; Mugalingam, Shan; Dittrich, Maria

    2016-04-01

    Phosphorus (P) is an important macronutrient that can limit aquatic primary production and the risk of harmful algal blooms. Although there is considerable evidence that P release from sediments can represent a significant source of P and burial in sediments returns P to the geological sink; these processes have been poorly characterised. In this study, we applied a non-steady state reactive transport diagenetic model to gain insights into the dynamics of phosphorus binding forms in sediments and the phosphorus cycling of the Bay of Quinte, an embayment of Lake Ontario, Canada. The three basins of the bay (Belleville, Hay Bay and Napanee) that we investigated had differences in their phosphorus binding forms and phosphorus release, reflecting the distinct spatial temporal patterns of land use and urbanization levels in the watershed. Sediment cores from the three stations were collected during summer and under ice cover in 2013-14. Oxygen, pH and redox potential were monitored by microsensors; porewater and sediment solid matter were analyzed for P content, and a sequential extraction was used to analyze P binding forms. In the reaction-transport model, total phosphorus was divided into adsorbed phosphorus, phosphorus bound with aluminium, organic phosphorus, redox sensitive and apatite phosphorus. Using the fluxes of organic and inorganic matter as dynamic boundary conditions, we simulated the depth profiles of solute and solid components. The model closely reproduced the fractionation data of phosphorus binding forms and soluble reactive phosphorus. The past and present P fluxes were calculated and estimated; they related to geochemical conditions, and P binding forms in sediments. Our results show that P release from sediments is dominated by the redox-sentive P fraction accounting for higher percentage at Napanee station. The main P binding form that can be immobilized through diagenesis is apatite P contributing highest P retention at HayBay station. The mass

  7. Modeling and sediment study in the watershed Medjerda, Tunisia

    Science.gov (United States)

    Kotti, Fatma; Mahé, Gil; Habaieb, Hamadi; Dieulin, Claudine; Hermassi, Taoufik

    2015-04-01

    series than should be about one century. The cores' analysis results show a succession of sedimentary layers that likely correspond to different flood deposits that succeeded on this site, and especially the datation of the cores shows that the selected area is a very important deposition area. This sedimentary study will help estimate the sediment dynamics to major estuaries, which is poorly known for most of the rivers of Maghreb. The reduction of the sediment supply to the sea is tipped as a major factor to be taken into account for a better understanding of the dynamics of coastal areas in the context of global climate change and sea level rise. Keywords: sediment core, Medjerda watershed, dam, hydrology, modeling, Tunisia

  8. A model of the sediment transport on a river network

    Science.gov (United States)

    Wang, Xu-Ming; Hao, Rui; Zhang, Jin-Feng; Huo, Jie

    2007-03-01

    A dynamical model is proposed to mimic the sediment transport on a river network. A river can be divided into some segments. For the ith segment the schlepping sediment ability of the flow may be scouring or depositing, which is influenced by that of the (i- 1)th segment. In order to compare our model simulation results with the empirical data obtained in Yellow River, the model is equipped with an experiential relation between the flow rate and the depositing rate of the Yellow River. After this, the simulation results show an excellent agreement with the empirical conclusions obtained with the upper and middle parts of Yellow River when it is in the low-water periods (for instance, in Dec., Jan. and Feb.). This indicates that our model may successfully describe the scouring-depositing of river networks.

  9. Comparison of estuarine sediment record with modelled rates of sediment supply from a western European catchment since 1500

    Science.gov (United States)

    Poirier, Clément; Poitevin, Cyril; Chaumillon, Éric

    2016-09-01

    Marine and estuarine sediment records reporting impacts of historical land use changes exist worldwide, but they are rarely supported by direct quantified evidence of changes in denudation rates on the related catchments. Here we implement a spatially-resolved RUSLE soil erosion model on the 10 000 km2 Charente catchment (France), supplied with realistic scenarios of land-cover and climate changes since 1500, and compare the results to a 14C-dated estuarine sediment record. Despite approximations, the model correctly predicts present-day Charente river sediment load. Back-cast modelling suggests that the Charente catchment is an interesting case where the sediment supply did not change despite increase in soil erosion resulting from 18th-century deforestation because it was mitigated by drier climate during the same period. Silt-sand alternations evidenced in the sediment record were correlated with sub-decadal rainfall variability.

  10. Elliptic solid-on-solid model's partition function as a single determinant

    CERN Document Server

    Galleas, W

    2016-01-01

    In this work we express the partition function of the integrable elliptic solid-on-solid model with domain-wall boundary conditions as a single determinant. This representation appears naturally as the solution of a system of functional equations governing the model's partition function.

  11. Instabilities on crystal surfaces: The two-component body-centered solid-on-solid model

    NARCIS (Netherlands)

    Carlon, E.; van Beijeren, H.; Mazzeo, G.

    1996-01-01

    The free energy of crystal surfaces that can be described by the two-component body-centered solid-on-solid model has been calculated in a mean-field approximation. The system may model ionic crystals with a bcc lattice structure (for instance CsCl). Crossings between steps are energetically favored

  12. Modeling Degradation in Solid Oxide Electrolysis Cells

    Energy Technology Data Exchange (ETDEWEB)

    Manohar S. Sohal; Anil V. Virkar; Sergey N. Rashkeev; Michael V. Glazoff

    2010-09-01

    Idaho National Laboratory has an ongoing project to generate hydrogen from steam using solid oxide electrolysis cells (SOECs). To accomplish this, technical and degradation issues associated with the SOECs will need to be addressed. This report covers various approaches being pursued to model degradation issues in SOECs. An electrochemical model for degradation of SOECs is presented. The model is based on concepts in local thermodynamic equilibrium in systems otherwise in global thermodynamic no equilibrium. It is shown that electronic conduction through the electrolyte, however small, must be taken into account for determining local oxygen chemical potential, , within the electrolyte. The within the electrolyte may lie out of bounds in relation to values at the electrodes in the electrolyzer mode. Under certain conditions, high pressures can develop in the electrolyte just near the oxygen electrode/electrolyte interface, leading to oxygen electrode delamination. These predictions are in accordance with the reported literature on the subject. Development of high pressures may be avoided by introducing some electronic conduction in the electrolyte. By combining equilibrium thermodynamics, no equilibrium (diffusion) modeling, and first-principles, atomic scale calculations were performed to understand the degradation mechanisms and provide practical recommendations on how to inhibit and/or completely mitigate them.

  13. Sediment carbon fate in phreatic karst (Part 2): Numerical model development and application

    Science.gov (United States)

    Husic, A.; Fox, J.; Ford, W.; Agouridis, C.; Currens, J.; Taylor, C.

    2017-06-01

    The authors develop a numerical model to elucidate time-distributed processes controlling sediment carbon fate in phreatic karst. Sediment carbon processes simulated in the new numerical model include in-conduit erosion and deposition, sediment carbon transport, surficial fine grained laminae evolution, carbon pool mixing, microbial oxidation, and the understudied process of sediment carbon exchange during equilibrium transport. The authors perform a model evaluation procedure that includes generalized likelihood uncertainty estimation to quantify uncertainty of the model results. Modeling results suggest that phreatic karst conduits sustain sediment transport activity long after surface storm events cease. The sustained sediment transport has the potential to shift the baseflow sediment yield of the phreatic karst to be on par with stormflow sediment yield. The sustained activity is suggested to promote the exchange of sediment carbon between the water column and subsurface karst deposits during equilibrium sediment transport conditions. In turn, the sediment carbon exchange impacts the mixing of new and old carbon pools and the flux of carbon from phreatic karst. Integrated numerical model results from this study support the concept that phreatic karst act as a biologically active conveyor of sediment carbon that temporarily stores sediment, turns over carbon at higher rates than surface streams, and recharges degraded carbon back to the fluvial system. The numerical modeling method adopted in this paper shows the efficacy of coupling carbon isotope fingerprinting with water quality modeling to study sediment carbon in phreatic karst.

  14. Settlement prediction model of slurry suspension based on sedimentation rate attenuation

    Directory of Open Access Journals (Sweden)

    Shuai-jie GUO

    2012-03-01

    Full Text Available This paper introduces a slurry suspension settlement prediction model for cohesive sediment in a still water environment. With no sediment input and a still water environment condition, control forces between settling particles are significantly different in the process of sedimentation rate attenuation, and the settlement process includes the free sedimentation stage, the log-linear attenuation stage, and the stable consolidation stage according to sedimentation rate attenuation. Settlement equations for sedimentation height and time were established based on sedimentation rate attenuation properties of different sedimentation stages. Finally, a slurry suspension settlement prediction model based on slurry parameters was set up with a foundation being that the model parameters were determined by the basic parameters of slurry. The results of the settlement prediction model show good agreement with those of the settlement column experiment and reflect the main characteristics of cohesive sediment. The model can be applied to the prediction of cohesive soil settlement in still water environments.

  15. Modeling Sediment Transport to the Ganga-Brahmaputra-Meghna Delta

    Science.gov (United States)

    Silvestre, J.; Higgins, S.; Jennings, K. S.

    2016-12-01

    India's National River Linking Project (NRLP) will transfer approximately 174 Bm3/y of water from the mountainous, water-rich north to the water-scarce south and west. Although there are many short-term benefits of the NRLP, such as decreased flooding during the monsoon season and increased water resources for irrigation, long-term consequences may include decreased sedimentation to the Ganga-Brahmaputra-Meghna Delta (GBM). Currently the GBM has a vertical aggradation rate of approximately 1-2 cm/y and is able to compensate for a global mean sea level rise of 3.3 ± 0.4 mm/y. However, Bangladesh and the GBM stand to be geomorphically impacted should the aggradation rate fall below sea level rise. This study better constrains influences of anthropogenic activities and sediment transport to the GBM. We employ HydroTrend, a climate-driven hydrological and sediment transport model, to simulate daily sediment and water fluxes for the period 1982 - 2012. Simulations are calibrated and validated against water discharge data from the Farakka Barrage, and different ways of delineating the Ganga Basin into sub-catchments are explored. Preliminary results show a 47% difference between simulated and observed mean annual water discharge when using basin-averaged input values and only a 1% difference for the base-case scenario, where proposed dams and canals are not included. Comparisons between the canals simulation (proposed NRLP included) and validation data suggest a 60% reduction in sediment load. However, comparison between the base-case simulation and the canals simulation suggests that India's water transfer project could decrease sediment delivery to the GBM by 9%. Further work should investigate improvements in the agreement between base-case simulation and validation data.

  16. NOAA ESRI Grid - sediment size predictions model in New York offshore planning area from Biogeography Branch

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset represents sediment size predictions from a sediment spatial model developed for the New York offshore spatial planning area. The model also includes...

  17. Numerical Modeling of Subglacial Sediment Deformation

    DEFF Research Database (Denmark)

    Damsgaard, Anders

    2015-01-01

    incompatible with commonly accepted till rheology models. Variation in pore-water pressure proves to cause reorganization in the internal stress network and leads to slow creeping deformation. The rate of creep is non-linearly dependent on the applied stresses. Granular creep can explain slow glacial...

  18. SPATIAL MODELING OF SOLID-STATE REGULAR POLYHEDRA (SOLIDS OF PLATON IN AUTOCAD SYSTEM

    Directory of Open Access Journals (Sweden)

    P. V. Bezditko

    2009-03-01

    Full Text Available This article describes the technology of modeling regular polyhedra by graphic methods. The authors came to the conclusion that in order to create solid models of regular polyhedra the method of extrusion is best to use.

  19. Modelling the initial structure dynamics of soil and sediment exemplified for a constructed hydrological catchment

    Science.gov (United States)

    Maurer, Thomas; Schneider, Anna; Gerke, Horst H.

    2014-05-01

    Knowledge about spatial heterogeneity is of essential for the analysis of the hydrological catchment behavior. Heterogeneity is directly related to the distribution of the solid phase, and in initial hydrological systems, the solid phase is mainly composed of mineral particles. In artificial catchments, such sediment structures relate to the applied construction technology. It is supposed that the development of catchment ecosystems is strongly influenced by such specific initial spatial distributions of the solid phase. Moreover, during the initial development period, the primary structures in a catchment are altered rapidly by translocation processes, thereby subdividing the initial system in different compartments. Questions are: How does initial sediment distribution affect further structural development? How is catchment hydrology influenced by the initial structural development? What structures have a relevant impact on catchment-scale hydrological behavior? We present results from a structural modelling approach using a process-based structure generator program. The constructed hydrological catchment 'Hühnerwasser' (Lower Lusatia, Brandenburg, Germany) served exemplarily for the model development. A set of scenarios was created describing possible initial heterogeneities of the catchment. Both the outcrop site from where the parent material was excavated and the specific excavation procedures were considered in the modelling approach. Generated distributions are incorporated in a gridded 3D volume model constructed with the GOCAD software. Results were evaluated by semivariogram analysis and by quantifying point-to-point deviations. We also introduce a modelling conception for simulating the highly dynamic initial structural change, based on the generated initial distributions. We present a strategy on how to develop the initial structure generator into an integrative tool in order to (i) simulate and analyse the spatio-temporal development dynamics

  20. Estimation of suspended-sediment concentration from total suspended solids and turbidity data for Kentucky, 1978-1995

    Science.gov (United States)

    Williamson, Tanja N.; Crawford, Charles G.

    2011-01-01

    Suspended sediment is a constituent of water quality that is monitored because of concerns about accelerated erosion, nonpoint contamination of water resources, and degradation of aquatic environments. In order to quantify the relationship among different sediment parameters for Kentucky streams, long-term records were obtained from the National Water Information System of the U.S. Geological Survey. Suspended-sediment concentration (SSC), the parameter traditionally measured and reported by the U.S. Geological Survey, was statistically compared to turbidity and total suspended solids (TSS), two parameters that are considered surrogate data. A linear regression of log-transformed observations was used to estimate SSC from TSS; 72% of TSS observations were less than coincident SSC observations; however, the estimated SSC values were almost as likely to be overestimated as underestimated. The SSC-turbidity relationship also used log-transformed observations, but required a nonlinear, breakpoint regression that separated turbidity observations ???6nephelometric turbidity units. The slope for these low turbidity values was not significantly different than zero, indicating that low turbidity observations provide no real information about SSC; in the case of the Kentucky sediment record, this accounts for 30% of the turbidity observations. ?? 2011 American Water Resources Association. This article is a U.S. Government work and is in the public domain in the USA.

  1. A Discrete Approach to Meshless Lagrangian Solid Modeling

    Directory of Open Access Journals (Sweden)

    Matthew Marko

    2017-07-01

    Full Text Available The author demonstrates a stable Lagrangian solid modeling method, tracking the interactions of solid mass particles rather than using a meshed grid. This numerical method avoids the problem of tensile instability often seen with smooth particle applied mechanics by having the solid particles apply stresses expected with Hooke’s law, as opposed to using a smoothing function for neighboring solid particles. This method has been tested successfully with a bar in tension, compression, and shear, as well as a disk compressed into a flat plate, and the numerical model consistently matched the analytical Hooke’s law as well as Hertz contact theory for all examples. The solid modeling numerical method was then built into a 2-D model of a pressure vessel, which was tested with liquid water particles under pressure and simulated with smoothed particle hydrodynamics. This simulation was stable, and demonstrated the feasibility of Lagrangian specification modeling for fluid–solid interactions.

  2. Glider observations and modeling of sediment transport in Hurricane Sandy

    Science.gov (United States)

    Miles, Travis; Seroka, Greg; Kohut, Josh; Schofield, Oscar; Glenn, Scott

    2015-03-01

    Regional sediment resuspension and transport are examined as Hurricane Sandy made landfall on the Mid-Atlantic Bight (MAB) in October 2012. A Teledyne-Webb Slocum glider, equipped with a Nortek Aquadopp current profiler, was deployed on the continental shelf ahead of the storm, and is used to validate sediment transport routines coupled to the Regional Ocean Modeling System (ROMS). The glider was deployed on 25 October, 5 days before Sandy made landfall in southern New Jersey (NJ) and flew along the 40 m isobath south of the Hudson Shelf Valley. We used optical and acoustic backscatter to compare with two modeled size classes along the glider track, 0.1 and 0.4 mm sand, respectively. Observations and modeling revealed full water column resuspension for both size classes for over 24 h during peak waves and currents, with transport oriented along-shelf toward the southwest. Regional model predictions showed over 3 cm of sediment eroded on the northern portion of the NJ shelf where waves and currents were the highest. As the storm passed and winds reversed from onshore to offshore on the southern portion of the domain waves and subsequently orbital velocities necessary for resuspension were reduced leading to over 3 cm of deposition across the entire shelf, just north of Delaware Bay. This study highlights the utility of gliders as a new asset in support of the development and verification of regional sediment resuspension and transport models, particularly during large tropical and extratropical cyclones when in situ data sets are not readily available.

  3. Discrete element modeling of subglacial sediment deformation

    DEFF Research Database (Denmark)

    Damsgaard, Anders; Egholm, David L.; Piotrowski, Jan A.

    . The numerical approach allows for a detailed analysis of the material dynamics and shear zone development during progressive shear strain. We demonstrate how the shear zone thickness and dilation increase with the magnitude of the normal stress. The stresses are distributed heterogeneously through the granular...... of the inter-particle contacts parameterizes the model. For validating the numerical approach, the macromechanical behavior of the numerical material is compared to the results from successive laboratory ring-shear experiments. Overall, there is a good agreement between the geotechnical behavior of the real...... granular materials and the numerical results. The materials deform by an elasto-plastic rheology under the applied effective normal stress and horizontal shearing. The peak and ultimate shear strengths depend linearly on the magnitude of the normal stress by the Mohr-Coulomb constitutive relationship...

  4. A 2-D process-based model for suspended sediment dynamics: a first step towards ecological modeling

    OpenAIRE

    2015-01-01

    In estuaries most of the sediment load is carried in suspension. Sediment dynamics differ depending on sediment supply and hydrodynamic forcing conditions that vary over space and over time. Suspended sediment concentration (SSC) is one of the most important contributors to turbidity, which influences habitat conditions and ecological functions of the system. A robust sediment model is the first step towards a chain of model including contaminants and phytoplankton dy...

  5. A GUIDED SWAT MODEL APPLICATION ON SEDIMENT YIELD MODELING IN PANGANI RIVER BASIN: LESSONS LEARNT

    Directory of Open Access Journals (Sweden)

    Preksedis Marco Ndomba

    2008-12-01

    Full Text Available The overall objective of this paper is to report on the lessons learnt from applying Soil and Water Assessment Tool (SWAT in a well guided sediment yield modelling study. The study area is the upstream of Pangani River Basin (PRB, the Nyumba Ya Mungu (NYM reservoir catchment, located in the North Eastern part of Tanzania. It should be noted that, previous modeling exercises in the region applied SWAT with preassumption that inter-rill or sheet erosion was the dominant erosion type. In contrast, in this study SWAT model application was guided by results of analysis of high temporal resolution of sediment flow data and hydro-meteorological data. The runoff component of the SWAT model was calibrated from six-years (i.e. 1977–1982 of historical daily streamflow data. The sediment component of the model was calibrated using one-year (1977–1988 daily sediment loads estimated from one hydrological year sampling programme (between March and November, 2005 rating curve. A long-term period over 37 years (i.e. 1969–2005 simulation results of the SWAT model was validated to downstream NYM reservoir sediment accumulation information. The SWAT model captured 56 percent of the variance (CE and underestimated the observed daily sediment loads by 0.9 percent according to Total Mass Control (TMC performance indices during a normal wet hydrological year, i.e., between November 1, 1977 and October 31, 1978, as the calibration period. SWAT model predicted satisfactorily the long-term sediment catchment yield with a relative error of 2.6 percent. Also, the model has identified erosion sources spatially and has replicated some erosion processes as determined in other studies and field observations in the PRB. This result suggests that for catchments where sheet erosion is dominant SWAT model may substitute the sediment-rating curve. However, the SWAT model could not capture the dynamics of sediment load delivery in some seasons to the catchment outlet.

  6. A GUIDED SWAT MODEL APPLICATION ON SEDIMENT YIELD MODELING IN PANGANI RIVER BASIN: LESSONS LEARNT

    Directory of Open Access Journals (Sweden)

    Preksedis M. Ndomba

    2008-01-01

    Full Text Available The overall objective of this paper is to report on the lessons learnt from applying Soil and Water Assessment Tool (SWAT in a well guided sediment yield modelling study. The study area is the upstream of Pangani River Basin (PRB, the Nyumba Ya Mungu (NYM reservoir catchment, located in the North Eastern part of Tanzania. It should be noted that, previous modeling exercises in the region applied SWAT with preassumption that inter-rill or sheet erosion was the dominant erosion type. In contrast, in this study SWAT model application was guided by results of analysis of high temporal resolution of sediment flow data and hydro-meteorological data. The runoff component of the SWAT model was calibrated from six-years (i.e. 1977¿1982 of historical daily streamflow data. The sediment component of the model was calibrated using one-year (1977-1988 daily sediment loads estimated from one hydrological year sampling programme (between March and November, 2005 rating curve. A long-term period over 37 years (i.e. 1969-2005 simulation results of the SWAT model was validated to downstream NYM reservoir sediment accumulation information. The SWAT model captured 56 percent of the variance (CE and underestimated the observed daily sediment loads by 0.9 percent according to Total Mass Control (TMC performance indices during a normal wet hydrological year, i.e., between November 1, 1977 and October 31, 1978, as the calibration period. SWAT model predicted satisfactorily the long-term sediment catchment yield with a relative error of 2.6 percent. Also, the model has identified erosion sources spatially and has replicated some erosion processes as determined in other studies and field observations in the PRB. This result suggests that for catchments where sheet erosion is dominant SWAT model may substitute the sediment-rating curve. However, the SWAT model could not capture the dynamics of sediment load delivery in some seasons to the catchment outlet.

  7. Occurrence of tributyltin (TBT)-resistant bacteria is not related to TBT pollution in Mekong River and coastal sediment: with a hypothesis of selective pressure from suspended solid.

    Science.gov (United States)

    Suehiro, Fujiyo; Mochizuki, Hiroko; Nakamura, Shinji; Iwata, Hisato; Kobayashi, Takeshi; Tanabe, Shinsuke; Fujimori, Yoshifumi; Nishimura, Fumitake; Tuyen, Bui Cach; Tana, Touch Seang; Suzuki, Satoru

    2007-07-01

    Tributyltin (TBT) is organotin compound that is toxic to aquatic life ranging from bacteria to mammals. This study examined the concentration of TBT in sediment from and near the Mekong River and the distribution of TBT-resistant bacteria. TBT concentrations ranged from TBT-resistant bacteria ranged TBT-resistant bacteria ranged from TBT in the sediment and of TBT-resistant bacteria were unrelated, and chemicals other than TBT might induce TBT resistance. TBT-resistant bacteria were more abundant in the dry season than in the rainy season. Differences in the selection process of TBT-resistant bacteria between dry and rainy seasons were examined using an advection-diffusion model of a suspended solid (SS) that conveys chemicals. The estimated dilution-diffusion time over a distance of 120 km downstream from a release site was 20 days during dry season and 5 days during rainy season, suggesting that bacteria at the sediment surface could be exposed to SS for longer periods during dry season.

  8. Discontinuous finite volume element discretization for coupled flow-transport problems arising in models of sedimentation

    Science.gov (United States)

    Bürger, Raimund; Kumar, Sarvesh; Ruiz-Baier, Ricardo

    2015-10-01

    The sedimentation-consolidation and flow processes of a mixture of small particles dispersed in a viscous fluid at low Reynolds numbers can be described by a nonlinear transport equation for the solids concentration coupled with the Stokes problem written in terms of the mixture flow velocity and the pressure field. Here both the viscosity and the forcing term depend on the local solids concentration. A semi-discrete discontinuous finite volume element (DFVE) scheme is proposed for this model. The numerical method is constructed on a baseline finite element family of linear discontinuous elements for the approximation of velocity components and concentration field, whereas the pressure is approximated by piecewise constant elements. The unique solvability of both the nonlinear continuous problem and the semi-discrete DFVE scheme is discussed, and optimal convergence estimates in several spatial norms are derived. Properties of the model and the predicted space accuracy of the proposed formulation are illustrated by detailed numerical examples, including flows under gravity with changing direction, a secondary settling tank in an axisymmetric setting, and batch sedimentation in a tilted cylindrical vessel.

  9. Aeolian Sediment Transport Integration in General Stratigraphic Forward Modeling

    Directory of Open Access Journals (Sweden)

    T. Salles

    2011-01-01

    Full Text Available A large number of numerical models have been developed to simulate the physical processes involved in saltation, and, recently to investigate the interaction between soil vegetation cover and aeolian transport. These models are generally constrained to saltation of monodisperse particles while natural saltation occurs over mixed soils. We present a three-dimensional numerical model of steady-state saltation that can simulate aeolian erosion, transport and deposition for unvegetated mixed soils. Our model simulates the motion of saltating particles using a cellular automata algorithm. A simple set of rules is used and takes into account an erosion formula, a transport model, a wind exposition function, and an avalanching process. The model is coupled to the stratigraphic forward model Sedsim that accounts for a larger number of geological processes. The numerical model predicts a wide range of typical dune shapes, which have qualitative correspondence to real systems. The model reproduces the internal structure and composition of the resulting aeolian deposits. It shows the complex formation of dune systems with cross-bedding strata development, bounding surfaces overlaid by fine sediment and inverse grading deposits. We aim to use it to simulate the complex interactions between different sediment transport processes and their resulting geological morphologies.

  10. Muskingum equation based downstream sediment flow simulation models for a river system

    Institute of Scientific and Technical Information of China (English)

    Briti Sundar Sil; Parthasarathi Choudhury

    2016-01-01

    Applications of sediment transport and water flow characteristics based sediment transport simulation models for a river system are presented in this study. An existing water–sediment model and a new sediment–water model are used to formulate the simulation models representing water and sediment movement in a river system. The sediment–water model parameters account for water flow characteristics embodying sediment transport properties of a section. The models are revised formulations of the multiple water inflows model describing water movement through a river system as given by the Muskingum principle. The models are applied to a river system in Mississippi River basin to estimate downstream sediment concentration, sediment discharge, and water discharge. River system and the river section parameters are estimated using a revised and the original multiple water inflows models by applying the genetic algorithm. The models estimate downstream sediment transport rates on the basis of upstream sediment/water flow rates to a system. Model performance is evaluated by using standard statistical criteria;downstream water discharge resulting from the original multiple water inflows model using the estimated river system parameters indicate that the revised models satisfactorily describe water movement through a river system. Results obtained in the study demonstrate the applicability of the sediment transport and water flow characteristics-based simulation models in predicting downstream sediment transport and water flow rates in a river system.

  11. Improving Sediment Transport Prediction by Assimilating Satellite Images in a Tidal Bay Model of Hong Kong

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2014-03-01

    Full Text Available Numerical models being one of the major tools for sediment dynamic studies in complex coastal waters are now benefitting from remote sensing images that are easily available for model inputs. The present study explored various methods of integrating remote sensing ocean color data into a numerical model to improve sediment transport prediction in a tide-dominated bay in Hong Kong, Deep Bay. Two sea surface sediment datasets delineated from satellite images from the Moderate Resolution Imaging Spectra-radiometer (MODIS were assimilated into a coastal ocean model of the bay for one tidal cycle. It was found that remote sensing sediment information enhanced the sediment transport model ability by validating the model results with in situ measurements. Model results showed that root mean square errors of forecast sediment both at the surface layer and the vertical layers from the model with satellite sediment assimilation are reduced by at least 36% over the model without assimilation.

  12. Macroscopic modelling of solid-state fermentation

    NARCIS (Netherlands)

    Hoogschagen, M.J.

    2007-01-01

    Solid-state fermentation is different from the more well known process of liquid fermentation because no free flowing water is present. The technique is primarily used in Asia. Well-known products are the foods tempe, soy sauce and saké. In industrial solid-state fermentation, the substrate usually

  13. Separation of inerts by differential sedimentation as previous stage to anaerobic digestion of organic fraction from municipal solid waste

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, C.; Martinez, V.; Esplugas, P.

    2009-07-01

    Municipal solid waste (MSW) treatment plants have as main function the valuation of municipal waste by means of materials recovery and valuation of organic fraction. In this type of facilities, the anaerobic digestion is a biological treatment of the organic matter collected in origin or mechanically separated from the mixed MSM. The objective is its valuation under the form of biogas and organic compost. Anaerobic digestion has high energy efficiency and a good range or organic matter elimination. Nevertheless, treatment of organic matter recovered from mixed MSW presents serious operation problems due to sedimentation of heavy improper materials (sands, glasses, metals) and flotation of light materials inside the digestors and piping. (Author)

  14. Use of solid-state 13C NMR in structural studies of humic acids and humin from Holocene sediments

    Science.gov (United States)

    Hatcher, P.G.; VanderHart, D.L.; Earl, W.L.

    1980-01-01

    13C NMR spectra of solid humic substances in Holocene sediments have been obtained using cross polarization with magic-angle sample spinning techniques. The results demonstrate that this technique holds great promise for structural characterizations of complex macromolecular substances such as humin and humic acids. Quantifiable distinctions can be made between structural features of aquatic and terrestrial humic substances. The aliphatic carbons of the humic substances are dominant components suggestive of input from lipid-like materials. An interesting resemblance is also noted between terrestrial humic acid and humin spectra. ?? 1980.

  15. Modeling chemical accumulation in sediment of small waterbodies accounting for sediment transport and water-sediment exchange processes over long periods.

    Science.gov (United States)

    Patterson, David Albert; Strehmel, Alexander; Erzgräber, Beate; Hammel, Klaus

    2017-07-20

    In a recent scientific opinion of the European Food Safety Authority it is argued that the accumulation of plant protection products in sediments over long time periods may be an environmentally significant process. Therefore, the European Food Safety Authority proposed a calculation to account for plant protection product accumulation. This calculation, however, considers plant protection product degradation within sediment as the only dissipation route, and does not account for sediment dynamics or back-diffusion into the water column. The hydraulic model Hydrologic Engineering Center-River Analysis System (HEC-RAS; US Army Corps of Engineers) was parameterized to assess sediment transport and deposition dynamics within the FOrum for Co-ordination of pesticide fate models and their USe (FOCUS) scenarios in simulations spanning 20 yr. The results show that only 10 to 50% of incoming sediment would be deposited. The remaining portion of sediment particles is transported across the downstream boundary. For a generic plant protection product substance this resulted in deposition of only 20 to 50% of incoming plant protection product substance. In a separate analysis, the FOCUS TOXSWA model was utilized to examine the relative importance of degradation versus back-diffusion as loss processes from the sediment compartment for a diverse range of generic plant protection products. In simulations spanning 20 yr, it was shown that back-diffusion was generally the dominant dissipation process. The results of the present study show that sediment dynamics and back-diffusion should be considered when calculating long-term plant protection product accumulation in sediment. Neglecting these may lead to a systematic overestimation of accumulation. Environ Toxicol Chem 2017;9999:1-9. © 2017 SETAC. © 2017 SETAC.

  16. Using a Parametric Solid Modeler as an Instructional Tool

    Science.gov (United States)

    Devine, Kevin L.

    2008-01-01

    This paper presents the results of a quasi-experimental study that brought 3D constraint-based parametric solid modeling technology into the high school mathematics classroom. This study used two intact groups; a control group and an experimental group, to measure the extent to which using a parametric solid modeler during instruction affects…

  17. Development of Mathematical Model on Preparation of Functionally Graded Material by Co-sedimentation

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    From the process of sedimentation the mathematical relationshipsamong deposition volume and powder properties as well as sedimentation parameters were deduced. Based on the formula a mathematical model was set up and simulated through the computer. At last the validity of mathematical model was supported by the representative experiment on Ti-Mo system FGM prepared by co-sedimentation.

  18. SEAGRASS STRESS RESPONSE MODEL: THE IMPORTANCE OF LIGHT, TEMPERATURE, SEDIMENTATION AND GEOCHEMISTRY

    Science.gov (United States)

    Our objective is to define interactions between seagrass and water-column and sediment stressors. The model was developed and optimized for sediments in Thalassia testudinum seagrass beds of Lower Laguna Madre, Texas, USA and is composed of a plant sub-model and a sediment diagen...

  19. How to bridge the gap between "unresolved" model and "resolved" model in CFD-DEM coupled method for sediment transport?

    Science.gov (United States)

    Liu, D.; Fu, X.; Liu, X.

    2016-12-01

    In nature, granular materials exist widely in water bodies. Understanding the fundamentals of solid-liquid two-phase flow, such as turbulent sediment-laden flow, is of importance for a wide range of applications. A coupling method combining computational fluid dynamics (CFD) and discrete element method (DEM) is now widely used for modeling such flows. In this method, when particles are significantly larger than the CFD cells, the fluid field around each particle should be fully resolved. On the other hand, the "unresolved" model is designed for the situation where particles are significantly smaller than the mesh cells. Using "unresolved" model, large amount of particles can be simulated simultaneously. However, there is a gap between these two situations when the size of DEM particles and CFD cell is in the same order of magnitude. In this work, the most commonly used void fraction models are tested with numerical sedimentation experiments. The range of applicability for each model is presented. Based on this, a new void fraction model, i.e., a modified version of "tri-linear" model, is proposed. Particular attention is paid to the smooth function of void fraction in order to avoid numerical instability. The results show good agreement with the experimental data and analytical solution for both single-particle motion and also group-particle motion, indicating great potential of the new void fraction model.

  20. Modelling the landslide area and sediment discharge in landslide-dominated region, Taiwan

    Science.gov (United States)

    Teng, Tse-Yang; Huang, -Chuan, Jr.; Lee, Tsung-Yu; Chen, Yi-Chin; Jan, Ming-Young; Liu, Cheng-Chien

    2016-04-01

    Many studies have indicated the magnified increase of rainfall intensification, landsliding and subsequent sediment discharge due to the global warming effect. However, a few works synthesized the "chain reaction" from rainfall, landsliding to sediment discharge at the same time because of the limited observations of landslide area and sediment discharge during episodes. Besides, the sediment transport strongly depends on the sediment supply and stream power which interact conditionally. In this study, our goal is to build a model that can simulate time-series landslide area and subsequent sediment discharge. The synthesized model would be applied onto Tsengwen Reservoir watershed in southern Taiwan, where lots of landslides occur every year. Unlike other studies, our landslide model considers not only rainfall effect but also previous landslide status, which may be applied to landslide-dominated regions and explains the irrelevant relationship between typhoon rainfall and landslide area. Furthermore, our sediment transport model considers the sediment budget which couples transport- and supply-limited of sediment. The result shows that the simulated time-series landslide area and the sediment transport agree with the observation and the R2 are 0.88 and 0.56, respectively. Reactivated ratio of previous landslide area is 72.7% which indicates the high reoccurrence of historical landslide in landslide-dominated regions. We divided nine historical typhoons into three periods to demonstrate the effect of sediment supply/supply-limited condition upon sediment transport. For instance, the rainfall is smaller in period 3 than in period 1 but the sediment transport is higher in period 3 due to the catastrophic landslide (typhoon Morakot) during period 2. We argue that quantifying sediment transport should couple not only with water discharge but sediment budget, which is rarely considered in calculating sediment transport. Moreover, the parameterization of the controlling

  1. Modeling for CVD of Solid Oxide Electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Starr, T.L.

    2002-09-18

    Because of its low thermal conductivity, high thermal expansion and high oxygen ion conductivity yttria-stabilized zirconia (YSZ) is the material of choice for high temperature electrolyte applications. Current coating fabrication methods have their drawbacks, however. Air plasma spray (APS) is a relatively low-cost process and is suitable for large and relatively complex shapes. it is difficult to produce uniform, relatively thin coatings with this process, however, and the coatings do not exhibit the columnar microstructure that is needed for reliable, long-term performance. The electron-beam physical vapor deposition (EB-PVD) process does produce the desirable microstructure, however, the capital cost of these systems is very high and the line-of-sight nature of the process limits coating uniformity and the ability to coat large and complex shapes. The chemical vapor deposition (CVD) process also produces the desirable columnar microstructure and--under proper conditions--can produce uniform coatings over complex shapes. CVD has been used for many materials but is relatively undeveloped for oxides, in general, and for zirconia, in particular. The overall goal of this project--a joint effort of the University of Louisville and Oak Ridge National Laboratory (ORNL)--is to develop the YSZ CVD process for high temperature electrolyte applications. This report describes the modeling effort at the University of Louisville, which supports the experimental work at ORNL. Early work on CVD of zirconia and yttria used metal chlorides, which react with water vapor to form solid oxide. Because of this rapid gas-phase reaction the water generally is formed in-situ using the reverse water-gas-shift reaction or a microwave plasma. Even with these arrangements gas-phase nucleation and powder formation are problems when using these precursors. Recent efforts on CVD of zirconia and YSZ have focused on use of metal-organic precursors (MOCVD). These are more stable in the gas

  2. Stochastic Flocculation Model for Cohesive Sediment Suspended in Water

    Directory of Open Access Journals (Sweden)

    Hyun Jung Shin

    2015-05-01

    Full Text Available Existing flocculation models for cohesive sediments are classified into two groups: population balance equation models (PBE and floc growth models. An FGM ensures mass conservation in a closed system. However, an FGM determines only the average size of flocs, whereas a PBE has the capability to calculate a size distribution of flocs. A new stochastic approach to model the flocculation process is theoretically developed and incorporated into a deterministic FGM in this study in order to calculate a size distribution of flocs as well as the average size. A log-normal distribution is used to generate random numbers based on previous laboratory experiments. The new stochastic flocculation model is tested with three laboratory experiment results. It was found and validated with measured data that the new stochastic flocculation model has the capability to replicate a size distribution of flocs reasonably well under different sediment and carrier flow conditions. Three more distributions (normal; Pearson type 3; and generalized extreme value distributions were also tested. From the comparison with results of different distribution functions, it is shown that a stochastic FGM using a log-normal distribution has a comparative advantage in terms of simplicity and accuracy.

  3. Motion of cells sedimenting on a solid surface in a laminar shear flow.

    Science.gov (United States)

    Tissot, O; Pierres, A; Foa, C; Delaage, M; Bongrand, P

    1992-01-01

    Cell adhesion often occurs under dynamic conditions, as in flowing blood. A quantitative understanding of this process requires accurate knowledge of the topographical relationships between the cell membrane and potentially adhesive surfaces. This report describes an experimental study made on both the translational and rotational velocities of leukocytes sedimenting of a flat surface under laminar shear flow. The main conclusions are as follows: (a) Cells move close to the wall with constant velocity for several tens of seconds. (b) The numerical values of translational and rotational velocities are inconsistent with Goldman's model of a neutrally buoyant sphere in a laminar shear flow, unless a drag force corresponding to contact friction between cells and the chamber floor is added. The phenomenological friction coefficient was 7.4 millinewton.s/m. (c) Using a modified Goldman's theory, the width of the gap separating cells (6 microns radius) from the chamber floor was estimated at 1.4 micron. (d) It is shown that a high value of the cell-to-substrate gap may be accounted for by the presence of cell surface protrusions of a few micrometer length, in accordance with electron microscope observations performed on the same cell population. (e) In association with previously reported data (Tissot, O., C. Foa, C. Capo, H. Brailly, M. Delaage, and P. Bongrand. 1991. Biocolloids and Biosurfaces. In press), these results are consistent with the possibility that cell-substrate attachment be initiated by the formation of a single molecular bond, which might be considered as the rate limiting step.

  4. Use of spatially distributed time-integrated sediment sampling networks and distributed fine sediment modelling to inform catchment management.

    Science.gov (United States)

    Perks, M T; Warburton, J; Bracken, L J; Reaney, S M; Emery, S B; Hirst, S

    2017-11-01

    Under the EU Water Framework Directive, suspended sediment is omitted from environmental quality standards and compliance targets. This omission is partly explained by difficulties in assessing the complex dose-response of ecological communities. But equally, it is hindered by a lack of spatially distributed estimates of suspended sediment variability across catchments. In this paper, we demonstrate the inability of traditional, discrete sampling campaigns for assessing exposure to fine sediment. Sampling frequencies based on Environmental Quality Standard protocols, whilst reflecting typical manual sampling constraints, are unable to determine the magnitude of sediment exposure with an acceptable level of precision. Deviations from actual concentrations range between -35 and +20% based on the interquartile range of simulations. As an alternative, we assess the value of low-cost, suspended sediment sampling networks for quantifying suspended sediment transfer (SST). In this study of the 362 km(2) upland Esk catchment we observe that spatial patterns of sediment flux are consistent over the two year monitoring period across a network of 17 monitoring sites. This enables the key contributing sub-catchments of Butter Beck (SST: 1141 t km(2) yr(-1)) and Glaisdale Beck (SST: 841 t km(2) yr(-1)) to be identified. The time-integrated samplers offer a feasible alternative to traditional infrequent and discrete sampling approaches for assessing spatio-temporal changes in contamination. In conjunction with a spatially distributed diffuse pollution model (SCIMAP), time-integrated sediment sampling is an effective means of identifying critical sediment source areas in the catchment, which can better inform sediment management strategies for pollution prevention and control. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Procedures for Geometric Data Reduction in Solid Log Modelling

    Science.gov (United States)

    Luis G. Occeña; Wenzhen Chen; Daniel L. Schmoldt

    1995-01-01

    One of the difficulties in solid log modelling is working with huge data sets, such as those that come from computed axial tomographic imaging. Algorithmic procedures are described in this paper that have successfully reduced data without sacrificing modelling integrity.

  6. Treatment of a sloping fluid-solid interface and sediment layering with the seismo-acoustic parabolic equation.

    Science.gov (United States)

    Collins, Michael D; Siegmann, William L

    2015-01-01

    The parabolic equation method is extended to handle problems in seismo-acoustics that have multiple fluid and solid layers, continuous depth dependence within layers, and sloping interfaces between layers. The medium is approximated in terms of a series of range-independent regions, and a single-scattering approximation is used to compute transmitted fields across the vertical interfaces between regions. The approach is implemented in terms of a set of dependent variables that is well suited to piecewise continuous depth dependence in the elastic parameters, but one of the fluid-solid interface conditions in that formulation involves a second derivative that complicates the treatment of sloping interfaces. This issue is resolved by using a non-centered, four-point difference formula for the second derivative. The approach is implemented using a matrix decomposition that is efficient when the parameters of the medium have a general dependence within the upper layers of the sediment but only depend on depth in the water column and deep within the sediment.

  7. Comparison of polycyclic aromatic hydrocarbons level between suspended solid and sediment samples of Pengkalan Chepa River, Kelantan state, Malaysia

    Science.gov (United States)

    Muslim, Noor Zuhartini Md; Babaheidari, Seyedreza Hashemi; Zakaria, Mohamad Pauzi

    2015-09-01

    Sixteen type of common Polycyclic Aromatic Hydrocarbons (PAHs) which consist of naphthalene, acenaphthene, acenaphthylene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghi]-perylene, indeno[1,2,3-cd]-pyrene and dibenz[a,h]-anthracene in suspended solid and sediment samples of Pengkalan Chepa River, Kelantan state, Malaysia were investigated. The analysis samples were taken from six different sites of Pengkalan Chepa River during sunny day. The samples were subjected to a series of pre-treatment before the level of PAHs can be determined. A Gas Chromatography-Mass Spectrometry (GC-MS) was the prime method for the analysis of PAHs level. A total of 16 PAHs concentration in suspended solid of the whole Pengkalan Chepa River was found to be 2144.6 ng/g dry weights. This concentration was about eight times more than 16 PAHs concentration in sediment which found to be 266.5 ng/g dry weights.

  8. Burn Rate Modelling of Solid Rocket Propellants (Short Communication

    Directory of Open Access Journals (Sweden)

    A.R. Kulkarni

    1998-01-01

    Full Text Available A generalised model of burning of a solid rocket propellant based on kinetics of propellant hasbeen developed. A complete set of variables has been formed after examining the existing models.Buckingham theorem provides the functional form of the model, such that the existing models are thesubcases of this generalised model. This proposed model has been validated by an experimental data.

  9. A network model for simulating sediment dynamics within a small watershed (Invited)

    Science.gov (United States)

    Patil, S.; Ye, S.; Xu, X.; Harman, C. J.; Sivapalan, M.; Hassan, M. A.

    2010-12-01

    Although sediment transport is extensively studied at the scale of a river reach, sediment dynamics at the watershed scale are still poorly understood. Sediment dynamics at this scale are largely determined by the propagation of sediment pulses through the river network which are driven mostly by the variability in flow conditions. Here, we develop a model which simulates sediment export from small to medium size basins in two stages: (1) delivery of sediments from hillslope and bank erosion into the river channel, and (2) propagation of the sediments in the channel through the river network towards watershed outlet. The model conceptualizes a watershed as a collection of reaches or representative elementary watersheds (REW) that are connected to each other through the river network structure, and each REW comprises a lumped representation of a hillslope and channel component. The flow of water along the stream network is modeled through mass and momentum balance equations applied in all the REWs and sediment transport within each REW is simulated through sediment balance equations. Every reach receives inputs of sediments from upstream REWs and also from the erosion of adjacent hillslopes, banks and the channel bed. We tested the model using data from Goodwin Creek, a small (21.3 sq. km) watershed in Mississippi, USA. The model yields good estimates of the timing and magnitude of sediment events as well as event-scale hysteresis in the sediment concentration-discharge relationship. The model also captures reach scale degradation/aggradation dynamics at different locations within the watershed, which are useful in identifying primary erosion/deposition zones and the spatio-temporal patterns of sediment supply and depletion. As a next step, we will use this model to assess the impacts of changing land-use/climate scenarios on sediment dynamics, and also facilitate in modeling the transport of nutrients (e.g., Phosphorus) that propagate along the river system through

  10. Numerical simulation of sediment erosion by submerged jets using an Eulerian model

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The erosion of loose beds by submerged circular impinging vertical turbulent jets is simulated using an Eulerian two-phase model which implements Euler-Euler coupled governing equations for fluid and solid phases, and a modified k-ε turbulence closure for the fluid phase. Both flow-particle and particle-particle interactions are considered in this model. The predictions of eroded bed profiles agree well with previous laboratory measurements and self-designed experiments. Analysis of the simulated results reveals that the velocity field of the jet water varies with various scouring intensities, that the scour depth and shape are mainly influenced by the driving force of the water when the density, diameter and porosity of the sand are the same, and that the porosity is an important contributor to sediment erosion. In this study, the scour depth, the height of dune and the velocity of the pore water increase with increasing porosity.

  11. Solid-phase arsenic speciation in aquifer sediments: A micro-X-ray absorption spectroscopy approach for quantifying trace-level speciation

    Science.gov (United States)

    Nicholas, Sarah L.; Erickson, Melinda L.; Woodruff, Laurel G.; Knaeble, Alan R.; Marcus, Matthew A.; Lynch, Joshua K.; Toner, Brandy M.

    2017-08-01

    Arsenic (As) is a geogenic contaminant affecting groundwater in geologically diverse systems globally. Arsenic release from aquifer sediments to groundwater is favored when biogeochemical conditions, especially oxidation-reduction (redox) potential, in aquifers fluctuate. The specific objective of this research is to identify the solid-phase sources and geochemical mechanisms of release of As in aquifers of the Des Moines Lobe glacial advance. The overarching concept is that conditions present at the aquifer-aquitard interfaces promote a suite of geochemical reactions leading to mineral alteration and release of As to groundwater. A microprobe X-ray absorption spectroscopy (μXAS) approach is developed and applied to rotosonic drill core samples to identify the solid-phase speciation of As in aquifer, aquitard, and aquifer-aquitard interface sediments. This approach addresses the low solid-phase As concentrations, as well as the fine-scale physical and chemical heterogeneity of the sediments. The spectroscopy data are analyzed using novel cosine-distance and correlation-distance hierarchical clustering for Fe 1s and As 1s μXAS datasets. The solid-phase Fe and As speciation is then interpreted using sediment and well-water chemical data to propose solid-phase As reservoirs and release mechanisms. The results confirm that in two of the three locations studied, the glacial sediment forming the aquitard is the source of As to the aquifer sediments. The results are consistent with three different As release mechanisms: (1) desorption from Fe (oxyhydr)oxides, (2) reductive dissolution of Fe (oxyhydr)oxides, and (3) oxidative dissolution of Fe sulfides. The findings confirm that glacial sediments at the interface between aquifer and aquitard are geochemically active zones for As. The diversity of As release mechanisms is consistent with the geographic heterogeneity observed in the distribution of elevated-As wells.

  12. Determination of refractory organic matter in marine sediments by chemical oxidation, analytical pyrolysis and solid-state 13C nuclear magnetic resonance spectroscopy

    OpenAIRE

    Rosa Arranz, José M. de la; González-Pérez, José Antonio; Hatcher, Patrick G.; Knicker, Heike; González-Vila, Francisco Javier

    2008-01-01

    Seeking to quantify the amount of refractory organic matter (ROM), which includes black carbon-like material (BC), in marine sediments, we have applied a two-step procedure that consists of a chemical oxidation with sodium chlorite of the demineralized sediments followed by integration of the aromatic C region in the remaining residues by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The efficacy for lignin removal was tested by analytical pyrolysis in the presence of tetrame...

  13. Modelling metallothionein induction in the liver of Sparus aurata exposed to metal-contaminated sediments.

    Science.gov (United States)

    Costa, P M; Repolho, T; Caeiro, S; Diniz, M E; Moura, I; Costa, M H

    2008-09-01

    Metallothionein (MT) in the liver of gilthead seabreams (Sparus aurata L., 1758) exposed to Sado estuary (Portugal) sediments was quantified to assess the MT induction potential as a biomarker of sediment-based contamination by copper (Cu), cadmium (Cd), lead (Pb) and arsenic (As). Sediments were collected from two control sites and four sites with different levels of contamination. Sediment Cu, Cd, Pb, As, total organic matter (TOM) and fine fraction (FF) levels were determined. Generalized linear models (GLM) allowed integration of sediment parameters with liver Cu, Cd, Pb, As and MT concentrations. Although sediment metal levels were lower than expected, we relate MT with liver Cd and also with interactions between liver and sediment Cu and between liver Cu and TOM. We suggest integrating biomarkers and environmental parameters using statistical models such as GLM as a more sensitive and reliable technique for sediment risk assessment than traditional isolated biomarker approaches.

  14. Multiphase CFD modeling of nearfield fate of sediment plumes

    DEFF Research Database (Denmark)

    Saremi, Sina; Hjelmager Jensen, Jacob

    2014-01-01

    Disposal of dredged material and the overflow discharge during the dredging activities is a matter of concern due to the potential risks imposed by the plumes on surrounding marine environment. This gives rise to accurately prediction of the fate of the sediment plumes released in ambient waters....... The two-phase mixture solution based on the drift-flux method is evaluated for 3D simulation of material disposal and overflow discharge from the hoppers. The model takes into account the hindrance and resistance mechanisms in the mixture and is capable of describing the flow details within the plumes...... and gives excellent results when compared to experimental data....

  15. Deschutes estuary feasibility study: hydrodynamics and sediment transport modeling

    Science.gov (United States)

    George, Douglas A.; Gelfenbaum, Guy; Lesser, Giles; Stevens, Andrew W.

    2006-01-01

    Continual sediment accumulation in Capitol Lake since the damming of the Deschutes River in 1951 has altered the initial morphology of the basin. As part of the Deschutes River Estuary Feasibility Study (DEFS), the United States Geological Survey (USGS) was tasked to model how tidal and storm processes will influence the river, lake and lower Budd Inlet should estuary restoration occur. Understanding these mechanisms will assist in developing a scientifically sound assessment on the feasibility of restoring the estuary. The goals of the DEFS are as follows. - Increase understanding of the estuary alternative to the same level as managing the lake environment.

  16. ONE-DIMENSIONAL HYDRODYNAMIC/SEDIMENT TRANSPORT MODEL FOR STREAM NETWORKS: TECHNICAL REPORT

    Science.gov (United States)

    This technical report describes a new sediment transport model and the supporting post-processor, and sampling procedures for sediments in streams. Specifically, the following items are described herein: EFDC1D - This is a new one-dimensional hydrodynamic and sediment tr...

  17. Sediment yield computation of the sandy and gritty area based on the digital watershed model

    Institute of Scientific and Technical Information of China (English)

    LIU; Jiahong; WANG; Guangqian; LI; Tiejian; XUE; Hai

    2006-01-01

    The Yellow River is well known as a sediment-laden river, which is the main reason that it cannot be controlled as easily as other rivers. Many researchers, such as Qian Ning et al., have found that the sediment load of the Yellow River comes mainly from the sandy and gritty area of the Loess Plateau. Therefore, it is very important to simulate the sediment yield in this area. This paper proposes a method to compute the sediment production in the sandy and gritty area based on the digital watershed model. The suggested model is calibrated and validated in the Chabagou basin, which is a small catchment in the study area. Finally, the model simulates the sediment yield of the sandy and gritty area in 1967, 1978, 1983, 1994 and 1997, which represents a high water and high sediment year, a mean water and mean sediment year, a high water and low sediment year, a low water and high sediment year, and a low water and low sediment year separately. The simulation results, including the runoff depth and erosion modulus, can well explain the "low water and high sediment" phenomena in the Yellow River basin. The total amount of the sediment production and its distribution generated by the model is very useful for water and soil conservation in the sandy and gritty area of the Loess Plateau.

  18. Viscoelastic Modelling of Solid Rocket Propellants using Maxwell Fluid Model

    Directory of Open Access Journals (Sweden)

    Himanshu Shekhar

    2010-07-01

    Full Text Available Maxwell fluid model consisting of a spring and a dashpot in series is applied for viscoelastic characterisation of solid rocket propellants. Suitable values of spring constant and damping coefficient wereemployed by least square variation of errors for generation of complete stress-strain curve in uniaxial tensile mode for case-bonded solid propellant formulations. Propellants from the same lot were tested at different strain rates. It was observed that change in spring constant, representing elastic part was very small with strain rate but damping constant varies significantly with variation in strain rate. For a typical propellant formulation, when strain rate was raised from 0.00037/s to 0.185/s, spring constant K changed from 5.5 MPato 7.9 MPa, but damping coefficient D was reduced from 1400 MPa-s to 4 MPa-s. For all strain rates, stress-strain curve was generated using Maxwell model and close matching with actual test curve was observed.This indicates validity of Maxwell fluid model for uniaxial tensile testing curves of case-bonded solid propellant formulations. It was established that at higher strain rate, damping coefficient becomes negligible as compared to spring constant. It was also observed that variation of spring constant is logarithmic with strain rate and that of damping coefficient follows power law. The correlation coefficients were introduced to ascertain spring constants and damping coefficients at any strain rate from that at a reference strain rate. Correlationfor spring constant needs a coefficient H, which is function of propellant formulation alone and not of test conditions and the equation developeds K2 = K1 + H ´ ln{(de2/dt/(de1/dt}. Similarly for damping coefficient D also another constant S is introduced and prediction formula is given by D2 = D1 ´ {(de2/dt/(de1/dt}S.Evaluating constants H and S at different strain rates validate this mathematical formulation for differentpropellant formulations

  19. Modelling the influence of total suspended solids on E. coli removal in river water.

    Science.gov (United States)

    Qian, Jueying; Walters, Evelyn; Rutschmann, Peter; Wagner, Michael; Horn, Harald

    2016-01-01

    Following sewer overflows, fecal indicator bacteria enter surface waters and may experience different lysis or growth processes. A 1D mathematical model was developed to predict total suspended solids (TSS) and Escherichia coli concentrations based on field measurements in a large-scale flume system simulating a combined sewer overflow. The removal mechanisms of natural inactivation, UV inactivation, and sedimentation were modelled. For the sedimentation process, one, two or three particle size classes were incorporated separately into the model. Moreover, the UV sensitivity coefficient α and natural inactivation coefficient kd were both formulated as functions of TSS concentration. It was observed that the E. coli removal was predicted more accurately by incorporating two particle size classes. However, addition of a third particle size class only improved the model slightly. When α and kd were allowed to vary with the TSS concentration, the model was able to predict E. coli fate and transport at different TSS concentrations accurately and flexibly. A sensitivity analysis revealed that the mechanisms of UV and natural inactivation were more influential at low TSS concentrations, whereas the sedimentation process became more important at elevated TSS concentrations.

  20. A Local Composition Model for Paraffinic Solid Solutions

    DEFF Research Database (Denmark)

    Coutinho, A.P. João; Knudsen, Kim; Andersen, Simon Ivar

    1996-01-01

    The description of the solid-phase non-ideality remains the main obstacle in modelling the solid-liquid equilibrium of hydrocarbons. A theoretical model, based on the local composition concept, is developed for the orthorhombic phase of n-alkanes and tested against experimental data for binary sy...... systems. It is shown that it can adequately predict the experimental phase behaviour of paraffinic mixtures. This work extends the applicability of local composition models to the solid phase. Copyright (C) 1996 Elsevier Science Ltd....

  1. Process-based distributed modeling approach for analysis of sediment dynamics in a river basin

    Directory of Open Access Journals (Sweden)

    M. A. Kabir

    2010-08-01

    Full Text Available Modeling of sediment dynamics for developing best management practices of reducing soil erosion and of sediment control has become essential for sustainable management of watersheds. Precise estimation of sediment dynamics is very important since soils are a major component of enormous environmental processes and sediment transport controls lake and river pollution extensively. Different hydrological processes govern sediment dynamics in a river basin, which are highly variable in spatial and temporal scales. This paper presents a process-based distributed modeling approach for analysis of sediment dynamics at river basin scale by integrating sediment processes (soil erosion, sediment transport and deposition with an existing process-based distributed hydrological model. In this modeling approach, the watershed is divided into an array of homogeneous grids to capture the catchment spatial heterogeneity. Hillslope and river sediment dynamic processes have been modeled separately and linked to each other consistently. Water flow and sediment transport at different surface grids and river nodes are modeled using one-dimensional kinematic wave approximation of Saint-Venant equations. The mechanics of sediment dynamics are integrated into the model using representative physical equations after a comprehensive review. The model has been tested on river basins in two different hydro climatic areas, the Abukuma River Basin, Japan and Latrobe River Basin, Australia. Sediment transport and deposition are modeled using Govers transport capacity equation. All spatial datasets, such as, Digital Elevation Model (DEM, land use and soil classification data, etc., have been prepared using raster "Geographic Information System (GIS" tools. The results of relevant statistical checks (Nash-Sutcliffe efficiency and R-squared value indicate that the model simulates basin hydrology and its associated sediment dynamics reasonably well. This paper presents the

  2. Process-based distributed modeling approach for analysis of sediment dynamics in a river basin

    Directory of Open Access Journals (Sweden)

    M. A. Kabir

    2011-04-01

    Full Text Available Modeling of sediment dynamics for developing best management practices of reducing soil erosion and of sediment control has become essential for sustainable management of watersheds. Precise estimation of sediment dynamics is very important since soils are a major component of enormous environmental processes and sediment transport controls lake and river pollution extensively. Different hydrological processes govern sediment dynamics in a river basin, which are highly variable in spatial and temporal scales. This paper presents a process-based distributed modeling approach for analysis of sediment dynamics at river basin scale by integrating sediment processes (soil erosion, sediment transport and deposition with an existing process-based distributed hydrological model. In this modeling approach, the watershed is divided into an array of homogeneous grids to capture the catchment spatial heterogeneity. Hillslope and river sediment dynamic processes have been modeled separately and linked to each other consistently. Water flow and sediment transport at different land grids and river nodes are modeled using one dimensional kinematic wave approximation of Saint-Venant equations. The mechanics of sediment dynamics are integrated into the model using representative physical equations after a comprehensive review. The model has been tested on river basins in two different hydro climatic areas, the Abukuma River Basin, Japan and Latrobe River Basin, Australia. Sediment transport and deposition are modeled using Govers transport capacity equation. All spatial datasets, such as, Digital Elevation Model (DEM, land use and soil classification data, etc., have been prepared using raster "Geographic Information System (GIS" tools. The results of relevant statistical checks (Nash-Sutcliffe efficiency and R–squared value indicate that the model simulates basin hydrology and its associated sediment dynamics reasonably well. This paper presents the

  3. Past, present and prospect of an Artificial Intelligence (AI) based model for sediment transport prediction

    Science.gov (United States)

    Afan, Haitham Abdulmohsin; El-shafie, Ahmed; Mohtar, Wan Hanna Melini Wan; Yaseen, Zaher Mundher

    2016-10-01

    An accurate model for sediment prediction is a priority for all hydrological researchers. Many conventional methods have shown an inability to achieve an accurate prediction of suspended sediment. These methods are unable to understand the behaviour of sediment transport in rivers due to the complexity, noise, non-stationarity, and dynamism of the sediment pattern. In the past two decades, Artificial Intelligence (AI) and computational approaches have become a remarkable tool for developing an accurate model. These approaches are considered a powerful tool for solving any non-linear model, as they can deal easily with a large number of data and sophisticated models. This paper is a review of all AI approaches that have been applied in sediment modelling. The current research focuses on the development of AI application in sediment transport. In addition, the review identifies major challenges and opportunities for prospective research. Throughout the literature, complementary models superior to classical modelling.

  4. Rheological and solid-state NMR assessments of copovidone/clotrimazole model solid dispersions.

    Science.gov (United States)

    Yang, Fengyuan; Su, Yongchao; Zhu, Lei; Brown, Chad D; Rosen, Lawrence A; Rosenberg, Kenneth J

    2016-03-16

    This study aims to assess several model solid dispersions by using dynamic oscillatory rheology, solid-state NMR and other solid phase characterization techniques, and correlate their viscoelastic responses with processing methods and microstructures. A model active pharmaceutical ingredient (API), clotrimazole, was compounded with copovidone to form solid dispersions via various techniques with different mixing capabilities. Physicochemical characterizations of the resulting solid dispersions demonstrated that simple physical mixing led to a poorly mixed blend manifested by existence of large API crystalline content and heterogeneous distribution. Cryogenic milling significantly improved mixing of two components as a result of reduced particle size and increased contact surface area, but produced limited amorphous content. In contrast, hot melt extrusion (HME) processing resulted in a homogenous amorphous solid dispersion because of its inherent mixing efficiency. Storage modulus and viscosities versus frequency of different solid dispersions indicated that the incorporation of API into the polymer matrix resulted in a plasticizing effect which reduced the viscosity. The crystalline/aggregated forms of API also exhibited more elastic response than its amorphous/dispersed counterpart. Temperature ramps of the physical mixture with high API concentration captured a critical temperature, at which a bump was observed in damping factor. This bump was attributed to the dissolution of crystalline API into the polymer. In addition, heating-cooling cycles of various solid dispersions suggested that cryomilling and HME processing could form a homogeneous solid dispersion at low API content, whereas high drug concentration led to a relatively unstable dispersion due to supersaturation of API in the polymer.

  5. Assessment of Seasonal Sedimentation in Rain-fed Irrigation Reservoirs by a Hillslope Erosion Modeling Approach

    Institute of Scientific and Technical Information of China (English)

    Weerakoon S. B.

    2005-01-01

    A distributed hillslope model is presented for the computation of seasonal sediment loads flowing into the rain-fed irrigation reservoirs (tanks)from the mountainous catchments in Sri Lanka. The model is based on the subdivision of the catchment into hillslopes and application of a sediment transport capacity equation at hillslope scale and computation of sediment loads transported to the tanks. Coarse and fine Sediment loads due to hourly excess rainfall during a season are separately estimated. The model depends on fewer parameters and can be easily calibrated for a tank. The model calibration only requires measurements of coarse and fine sediment loads transported into the tank due to several rainfalls of different intensities from a representative subcatchment of the tank. Coarse sediment loads are measured by using a sediment trap installed across an ephemeral stream draining the subcatchment. Fine sediment loads are obtained by measuring the discharge and accompanied sediment concentrations over the sediment trap. The model is calibrated,verified and applied for an irrigation tank in Sri Lanka to estimate the seasonal sedimentation loads.

  6. Sediment management modelling in the Blue Nile Basin using SWAT model

    Directory of Open Access Journals (Sweden)

    G. D. Betrie

    2011-03-01

    Full Text Available Soil erosion/sedimentation is an immense problem that has threatened water resources development in the Nile river basin, particularly in the Eastern Nile (Ethiopia, Sudan and Egypt. An insight into soil erosion/sedimentation mechanisms and mitigation methods plays an imperative role for the sustainable water resources development in the region. This paper presents daily sediment yield simulations in the Upper Blue Nile under different Best Management Practice (BMP scenarios. Scenarios applied in this paper are (i maintaining existing conditions, (ii introducing filter strips, (iii applying stone bunds (parallel terraces, and (iv reforestation. The Soil and Water Assessment Tool (SWAT was used to model soil erosion, identify soil erosion prone areas and assess the impact of BMPs on sediment reduction. For the existing conditions scenario, the model results showed a satisfactory agreement between daily observed and simulated sediment concentrations as indicated by Nash-Sutcliffe efficiency greater than 0.83. The simulation results showed that applying filter strips, stone bunds and reforestation scenarios reduced the current sediment yields both at the subbasins and the basin outlets. However, a precise interpretation of the quantitative results may not be appropriate because some physical processes are not well represented in the SWAT model.

  7. Modeling supercritical fluid extraction process involving solute-solid interaction

    Energy Technology Data Exchange (ETDEWEB)

    Goto, M.; Roy, B. Kodama, A.; Hirose, T. [Kumamoto Univ., Kumamoto (Japan)

    1998-04-01

    Extraction or leaching of solute from natural solid material is a mass transfer process involving dissolution or release of solutes from a solid matrix. Interaction between the solute and solid matrix often influences the supercritical fluid extraction process. A model accounting for the solute-solid interaction as well as mass transfer is developed. The BET equation is used to incorporate the interaction and the solubility of solutes into the local equilibrium in the model. Experimental data for the supercritical extraction of essential oil and cuticular wax from peppermint leaves are successfully analyzed by the model. The effects of parameters on the extraction behavior are demonstrated to illustrate the concept of the model. 18 refs., 5 figs., 1 tab.

  8. Modeling of sediment transport along Mangalore coast using mike 21

    Digital Repository Service at National Institute of Oceanography (India)

    Babu, K.S.; Dwarakish, G.S.; Jayakumar, S.

    The objective of the present study is to understand the sediment transport along Mangalore Coast and to quantify the sediment transport rates. The data used in the present study includes Wave, Wind, Tide, Naval Hydrographic Chart (Bathymetry Chart...

  9. Longshore sediment transport model for the Indian west coast

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    Longshore sediment transport rates for the Indian west coast from Cochin to Porbandar are estimated from ship observed wave data (1968 to 1986). The sediment transport rate is relatively high during the southwest monsoon period from June...

  10. Vertical distribution of denitrification in an estuarine sediment: integrating sediment flowthrough reactor experiments and microprofiling via reactive transport modeling.

    Science.gov (United States)

    Laverman, Anniet M; Meile, Christof; Van Cappellen, Philippe; Wieringa, Elze B A

    2007-01-01

    Denitrifying activity in a sediment from the freshwater part of a polluted estuary in northwest Europe was quantified using two independent approaches. High-resolution N(2)O microprofiles were recorded in sediment cores to which acetylene was added to the overlying water and injected laterally into the sediment. The vertical distribution of the rate of denitrification supported by nitrate uptake from the overlying water was then derived from the time series N(2)O concentration profiles. The rates obtained for the core incubations were compared to the rates predicted by a forward reactive transport model, which included rate expression for denitrification calibrated with potential rate measurements obtained in flowthrough reactors containing undisturbed, 1-cm-thick sediment slices. The two approaches yielded comparable rate profiles, with a near-surface, 2- to 3-mm narrow zone of denitrification and maximum in situ rates on the order of 200 to 300 nmol cm(-3) h(-1). The maximum in situ rates were about twofold lower than the maximum potential rate for the 0- to 1-cm depth interval of the sediment, indicating that in situ denitrification was nitrate limited. The experimentally and model-derived rates of denitrification implied that there was nitrate uptake by the sediment at a rate that was on the order of 50 (+/- 10) nmol cm(-2) h(-1), which agreed well with direct nitrate flux measurements for core incubations. Reactive transport model calculations showed that benthic uptake of nitrate at the site is particularly sensitive to the nitrate concentration in the overlying water and the maximum potential rate of denitrification in the sediment.

  11. New cold-fiber headspace solid-phase microextraction device for quantitative extraction of polycyclic aromatic hydrocarbons in sediment.

    Science.gov (United States)

    Ghiasvand, Ali Reza; Hosseinzadeh, Shokouh; Pawliszyn, Janusz

    2006-08-18

    A new automated headspace solid-phase microextraction (HS-SPME) sampling device was developed, with the capability of heating the sample matrix and simultaneously cooling the fiber coating. The device was evaluated for the quantitative extraction of polycyclic aromatic hydrocarbons (PAHs) from solid matrices. The proposed device improves the efficiency of the release of analytes from the matrix, facilitates the mass transfer into the headspace and significantly increases the partition coefficients of the analytes, by creating a temperature gap between the cold-fiber (CF) coating and the hot headspace. The reliability and applicability of previously reported cold-fiber devices are significantly enhanced by this improvement. In addition, it can be easily adopted for full automation of extraction, enrichment and introduction of different samples using commercially available autosampling devices. Sand samples spiked with PAHs were used as solid matrices and the effect of different experimental parameters were studied, including the extraction temperature, extraction time, moisture content, and the effect of sonication and modifier under optimal experimental conditions, linear calibration curves were obtained in the range of 0.0009-1000 ng/g, with regression coefficients higher than 0.99 and detection limits that ranged from 0.3 to 3 pg/g. Reproducible, precise and high throughput extraction, monitoring and quantification of PAHs were achieved with the automated cold-fiber headspace solid-phase microextraction (CF-HS-SPME) device coupled to GC-flame ionization detection. Determination of PAHs in certified reference sediments using the proposed approach exhibited acceptable agreement with the standard values.

  12. Calculation of statistical entropic measures in a model of solids

    CERN Document Server

    Sanudo, Jaime

    2012-01-01

    In this work, a one-dimensional model of crystalline solids based on the Dirac comb limit of the Kronig-Penney model is considered. From the wave functions of the valence electrons, we calculate a statistical measure of complexity and the Fisher-Shannon information for the lower energy electronic bands appearing in the system. All these magnitudes present an extremal value for the case of solids having half-filled bands, a configuration where in general a high conductivity is attained in real solids, such as it happens with the monovalent metals.

  13. An Integrated Experimental and Modeling Approach to Predict Sediment Mixing from Benthic Burrowing Behavior.

    Science.gov (United States)

    Roche, Kevin R; Aubeneau, Antoine F; Xie, Minwei; Aquino, Tomás; Bolster, Diogo; Packman, Aaron I

    2016-09-20

    Bioturbation is the dominant mode of sediment transport in many aquatic environments and strongly influences both sediment biogeochemistry and contaminant fate. Available bioturbation models rely on highly simplified biodiffusion formulations that inadequately capture the behavior of many benthic organisms. We present a novel experimental and modeling approach that uses time-lapse imagery to directly relate burrow formation to resulting sediment mixing. We paired white-light imaging of burrow formation with fluorescence imaging of tracer particle redistribution by the oligochaete Lumbriculus variegatus. We used the observed burrow formation statistics and organism density to parametrize a parsimonious model for sediment mixing based on fundamental random walk theory. Worms burrowed over a range of times and depths, resulting in homogenization of sediments near the sediment-water interface, rapid nonlocal transport of tracer particles to deep sediments, and large areas of unperturbed sediments. Our fundamental, parsimonious random walk model captures the central features of this highly heterogeneous sediment bioturbation, including evolution of the sediment-water interface coupled with rapid near-surface mixing and anomalous late-time mixing resulting from infrequent, deep burrowing events. This approach provides a general, transferable framework for explicitly linking sediment transport to governing biophysical processes.

  14. Sulfide and methane production in sewer sediments: Field survey and model evaluation.

    Science.gov (United States)

    Liu, Yiwen; Tugtas, A Evren; Sharma, Keshab R; Ni, Bing-Jie; Yuan, Zhiguo

    2016-02-01

    Sewer sediment processes have been reported to significantly contribute to overall sulfide and methane production in sewers, at a scale comparable to that of sewer biofilms. The physiochemical and biological characteristics of sewer sediments are heterogeneous; however, the variability of in-sediments sulfide and methane production rates among sewers has not been assessed to date. In this study, five sewer sediment samples were collected from two cities in Australia with different climatic conditions. Batch assays were conducted to determine the rates of sulfate reduction and methane production under different flow velocity (shear stress) conditions as well as under completely mixed conditions. The tests showed substantial and variable sulfate reduction and methane production activities among different sediments. Sulfate reduction and methane production from sewer sediments were confirmed to be areal processes, and were dependent on flow velocity/shear stress. Despite of the varying characteristics and reactions kinetics, the sulfate reduction and methane production processes in all sediments could be well described by a one-dimensional sewer sediment model recently developed based on results obtained from a laboratory sewer sediment reactor. Model simulations indicated that the in-situ contribution of sewer sediment emissions could be estimated without the requirement of measuring the specific sediment characteristics or the sediment depths.

  15. Measuring and modeling suspended sediment concentration profiles in the surf zone

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Time-averaged suspended sediment concentration profiles across the surf zone were measured in a large-scale three-dimensional movable bed laboratory facility (LSTF:Large-scale Sediment Transport Facility). Sediment suspension under two different types of breaking waves, spilling and plunging breakers, was investigated. The magnitudes and shapes of the concentration profiles varied substantially at different locations across the surf zone, reflecting the different intensities of breaking-induced turbulence. Sediment sus- pension at the energetic plunging breaker-line was much more active, resulting in nearly homogeneous concentration profiles throughout most of the water column, as compared to the reminder of the surf zone and at the spilling breaker-line. Four suspended sediment concentration models were examined based on the LSTF data, including the mixing turbulence length approach, segment eddy viscosity model, breaking-induced wave-energy dissipation approach, and a combined breaking and turbulence length model developed by this study. Neglecting the breaking-induced turbulence and subsequent sediment mixing, suspended sediment concentration models failed to predict the across-shore variations of the sediment suspension, especially at the plunging breaker-line. Wave-energy dissipation rate provided an accurate method for estimating the intensity of turbulence generated by wave breaking. By incorporating the breaking-induced turbulence, the combined breaking and turbulence length model reproduced the across-shore variation of sediment suspension in the surf zone. The combined model reproduced the measured time-averaged suspended sediment concentration profiles reasonably well across the surf zone.

  16. A network model for prediction and diagnosis of sediment dynamics at the watershed scale

    Science.gov (United States)

    Patil, Sopan; Sivapalan, Murugesu; Hassan, Marwan A.; Ye, Sheng; Harman, Ciaran J.; Xu, Xiangyu

    2012-12-01

    We present a semi-distributed model that simulates suspended sediment export from a watershed in two stages: (1) delivery of sediments from hillslope and bank erosion into the river channel, and (2) propagation of the channel sediments through the river network toward the watershed outlet. The model conceptualizes a watershed as the collection of reaches, or representative elementary watersheds (REW), that are connected to each other through the river network, and each REW comprises a lumped representation of a hillslope and channel component. The flow of water along the stream network is modeled through coupled mass and momentum balance equations applied in all REWs and sediment transport within each REW is simulated through the sediment balance equations. Every reach receives sediment inputs from upstream REWs (if present) and from the erosion of adjacent hillslopes, banks and channel bed. We tested this model using 12 years (1982-1993) of high temporal resolution data from Goodwin Creek, a 21.3 km2 watershed in Mississippi, USA. The model yields good estimates of sediment export patterns at the watershed outlet, with Pearson correlation coefficient (R value) of 0.85, 0.87, and 0.95 at daily, monthly, and annual resolution, respectively. Furthermore, the model shows that the dynamics of sediment transport are controlled to a large extent by the differences in the behavior of coarse and fine sediment particles, temporary channel storage, and the spatial variability in climatic forcing. These processes have a bearing on the patterns of sediment delivery with increasing scale.

  17. Formation of natural gas hydrates in marine sediments 1. Conceptual model of gas hydrate growth conditioned by host sediment properties

    Science.gov (United States)

    Clennell, M.B.; Hovland, M.; Booth, J.S.; Henry, P.; Winters, W.J.

    1999-01-01

    The stability of submarine gas hydrates is largely dictated by pressure and temperature, gas composition, and pore water salinity. However, the physical properties and surface chemistry of deep marine sediments may also affect the thermodynamic state, growth kinetics, spatial distributions, and growth forms of clathrates. Our conceptual model presumes that gas hydrate behaves in a way analogous to ice in a freezing soil. Hydrate growth is inhibited within fine-grained sediments by a combination of reduced pore water activity in the vicinity of hydrophilic mineral surfaces, and the excess internal energy of small crystals confined in pores. The excess energy can be thought of as a "capillary pressure" in the hydrate crystal, related to the pore size distribution and the state of stress in the sediment framework. The base of gas hydrate stability in a sequence of fine sediments is predicted by our model to occur at a lower temperature (nearer to the seabed) than would be calculated from bulk thermodynamic equilibrium. Capillary effects or a build up of salt in the system can expand the phase boundary between hydrate and free gas into a divariant field extending over a finite depth range dictated by total methane content and pore-size distribution. Hysteresis between the temperatures of crystallization and dissociation of the clathrate is also predicted. Growth forms commonly observed in hydrate samples recovered from marine sediments (nodules, and lenses in muds; cements in sands) can largely be explained by capillary effects, but kinetics of nucleation and growth are also important. The formation of concentrated gas hydrates in a partially closed system with respect to material transport, or where gas can flush through the system, may lead to water depletion in the host sediment. This "freeze-drying" may be detectable through physical changes to the sediment (low water content and overconsolidation) and/or chemical anomalies in the pore waters and metastable

  18. Streamflow and water-quality properties in the West Fork San Jacinto River Basin and regression models to estimate real-time suspended-sediment and total suspended-solids concentrations and loads in the West Fork San Jacinto River in the vicinity of Conroe, Texas, July 2008-August 2009

    Science.gov (United States)

    Bodkin, Lee J.; Oden, Jeannette H.

    2010-01-01

    To better understand the hydrology (streamflow and water quality) of the West Fork San Jacinto River Basin downstream from Lake Conroe near Conroe, Texas, including spatial and temporal variation in suspended-sediment (SS) and total suspended-solids (TSS) concentrations and loads, the U.S. Geological Survey, in cooperation with the Houston-Galveston Area Council and the Texas Commission on Environmental Quality, measured streamflow and collected continuous and discrete water-quality data during July 2008-August 2009 in the West Fork San Jacinto River Basin downstream from Lake Conroe. During July 2008-August 2009, discrete samples were collected and streamflow measurements were made over the range of flow conditions at two streamflow-gaging stations on the West Fork San Jacinto River: West Fork San Jacinto River below Lake Conroe near Conroe, Texas (station 08067650) and West Fork San Jacinto River near Conroe, Texas (station 08068000). In addition to samples collected at these two main monitoring sites, discrete sediment samples were also collected at five additional monitoring sites to help characterize water quality in the West Fork San Jacinto River Basin. Discrete samples were collected semimonthly, regardless of flow conditions, and during periods of high flow resulting from storms or releases from Lake Conroe. Because the period of data collection was relatively short (14 months) and low flow was prevalent during much of the study, relatively few samples collected were representative of the middle and upper ranges of historical daily mean streamflows. The largest streamflows tended to occur in response to large rainfall events and generally were associated with the largest SS and TSS concentrations. The maximum SS and TSS concentrations at station 08067650 (180 and 133 milligrams per liter [mg/L], respectively) were on April 19, 2009, when the instantaneous streamflow was the third largest associated with a discrete sample at the station. SS concentrations

  19. On the elliptic $\\mathfrak{gl}_2$ solid-on-solid model: functional relations and determinants

    CERN Document Server

    Galleas, W

    2016-01-01

    In this work we study an elliptic solid-on-solid model with domain-wall boundaries having the elliptic quantum group $\\mathcal{E}_{p, \\gamma}[\\widehat{\\mathfrak{gl}_2}]$ as its underlying symmetry algebra. We elaborate on results previously presented by the author and extend our analysis to include continuous families of single determinantal representations for the model's partition function. Interestingly, our families of representations are parameterized by two continuous complex variables which can be arbitrarily chosen without affecting the partition function.

  20. Solid-on-solid model for surface growth in 2+1 dimensions

    Science.gov (United States)

    Hosseinabadi, S.; Masoudi, A. A.; Sadegh Movahed, M.

    2010-04-01

    We analyze in detail the solid-on-solid (SOS) model for growth processes on a square substrate in 2+1 dimensions. By using the Markovian surface properties, we introduce an alternative approach for determining the roughness exponent of a special type of SOS model-the restricted-solid-on-solid (RSOS) model-in 2+1 dimensions. This model is the SOS model with the additional restriction that the height difference must be S=1. Our numerical results show that the behavior of the SOS model in 2+1 dimensions for approximately S≥S×∼8 belongs to the two different universality classes: during the initial time stage, tChein and Pang (2004) [8]. Using the structure function, we compute the roughness exponent. In contrast to the growth exponent, the roughness exponent does not show crossover for different values of S. The scaling exponents of the structure function for fixed values of separation distance versus S in one and two space dimensions are ξ=0.92±0.05 and ξ=0.86±0.05 at 1σ confidence level, respectively.

  1. Theoretical, experimental and field studies concerning molecular diffusion of radioisotopes in sediments and suspended solid particles of the sea Part A: Theories and mathematical calculations

    NARCIS (Netherlands)

    Duursma, E.K.; Hoede, C.

    1967-01-01

    The best way to describe the kinetics of the uptake of radioisotopes from sea water by bottom sediments and suspended solid matter is by molecular diffusion. The basic diffusion laws can be applied for finding the important parameter of the diffusion, the diffusion coefficient, which will characteri

  2. Geographic information system-coupling sediment delivery distributed modeling based on observed data.

    Science.gov (United States)

    Lee, S E; Kang, S H

    2014-01-01

    Spatially distributed sediment delivery (SEDD) models are of great interest in estimating the expected effect of changes on soil erosion and sediment yield. However, they can only be applied if the model can be calibrated using observed data. This paper presents a geographic information system (GIS)-based method to calculate the sediment discharge from basins to coastal areas. For this, an SEDD model, with a sediment rating curve method based on observed data, is proposed and validated. The model proposed here has been developed using the combined application of the revised universal soil loss equation (RUSLE) and a spatially distributed sediment delivery ratio, within Model Builder of ArcGIS's software. The model focuses on spatial variability and is useful for estimating the spatial patterns of soil loss and sediment discharge. The model consists of two modules, a soil erosion prediction component and a sediment delivery model. The integrated approach allows for relatively practical and cost-effective estimation of spatially distributed soil erosion and sediment delivery, for gauged or ungauged basins. This paper provides the first attempt at estimating sediment delivery ratio based on observed data in the monsoon region of Korea.

  3. A new settling velocity model to describe secondary sedimentation

    DEFF Research Database (Denmark)

    Ramin, Elham; Wágner, Dorottya Sarolta; Yde, Lars

    2014-01-01

    Secondary settling tanks (SSTs) are the most hydraulically sensitive unit operations in biological wastewater treatment plants. The maximum permissible inflow to the plant depends on the efficiency of SSTs in separating and thickening the activated sludge. The flow conditions and solids distribut......Secondary settling tanks (SSTs) are the most hydraulically sensitive unit operations in biological wastewater treatment plants. The maximum permissible inflow to the plant depends on the efficiency of SSTs in separating and thickening the activated sludge. The flow conditions and solids...... associated with their calibration. In this study, we developed a new settling velocity model, including hindered, transient and compression settling, and showed that it can be calibrated to data from a simple, novel settling column experimental set-up using the Bayesian optimization method DREAM......(ZS). In addition, correlations between the Herschel-Bulkley rheological model parameters and sludge concentration were identified with data from batch rheological experiments. A 2-D axisymmetric CFD model of a circular SST containing the new settling velocity and rheological model was validated with full...

  4. MODELLING OF SEDIMENTS CONCENTRATION DISTRIBUTION IN DREDGED CANALS OF THE NIGER DELTA ESTUARINE REGION, NIGERIA

    Directory of Open Access Journals (Sweden)

    Charles Chizom Dike

    2013-01-01

    Full Text Available Previous sediments concentration distributi on models used in the study of sediment characteristics of the dredged canals in the Niger-Delta estuarine region, Nigeria; did not take into consideration the lateral in flow due to tidal effects, which affects tremendously, the sediment intake into the estuarine waters. In the current research, existing models are modified by incorpora ting the missing lateral inflow parameters, which are peculiar to the Niger Delta environment, to obtain more accurate model results. Details are given herein, of the deve lopment and application of a 3-dimensional numerical model (EKU 2.8 Models to predict sediment concentration distribution (total suspended sediment & bed sediment load s in the Niger Delta estuarine canals, with Ekulama well 19 access canal as a case study. The approach in this paper involved coupling a sediment transport equation (w ith the inclusion of lateral inflow parameters, with an estuarine hydro-dy namics equation to generate a generic 3- dimensional sediment concentration distribu tion model, using deterministic approach. Predicted results using this model compar ed favorably with measured field results. Average sediment concentration of 29mg/l was obtained compared with 31mg/l measured in the field for bed sediment loads. Finally, the predicted sediment concentration distribution (TSS, when comp ared with field results, gave average correlation coefficient of 0.9.; hence, the present model will assist in generating adequate information /data on sediment ch aracteristics and transport mechanism, required for effective design of canals to redu ce rate of siltation. The application of the above knowledge/parameters generated from this model to effectively design canals to reduce siltation will be treated in subsequent articles.

  5. Sediment and phosphorus fluxes - monitoring and modelling from field to regional scale - connectivity implications

    Science.gov (United States)

    Bauer, Miroslav; Zumr, David; Krása, Josef; Dostál, Tomáš; Jáchymová, Barbora; Rosendorf, Pavel

    2015-04-01

    Sediment and phosphorus fluxes - monitoring and modelling from field to regional scale - connectivity implications Miroslav Bauer1), David Zumr1), Josef Krása1), Tomáš Dostal1), Barbora Jáchymová1), Pavel Rosendorf2) Czech Technical University in Prague1, Water Research Institute of T.G.M. 2, Agricultural landscape management has a strong influences on sediment and nutrients flow paths from field to streams and reservoirs. According to many studies water erosion driven phosphorus can play important role in total phosphorous budgets in catchments and accelerate eutrophication process in vulnerable reservoirs. Research team of CTU Prague focuses on research of sediment transport processes from a small plot scale to regional scale. Using field rainfall simulator the data are collected to assess the fluxes in the scale from one to several square meters and to analyze the plot size effect on the runoff, solid particles and phosphorous transport processes (see corresponding posters of Jachymova et al., Kavka et al., Laburda et al., Zumr et al.). Running fully agricultural experimental catchment of 49 ha (Nucice, Czech Republic) and experimental soil erosion plots (Bykovice, Czech Republic) we analyze runoff and soil erosion with the aim to upscale the results from single plot studies to the catchment scale. Soil erosion is also monitored by means of spatially distributed soil sampling and photogrammetry analyses. The water flow pathways via subsurface and surface runoff and the temporary variable catchment connectivity are studied here. Finally the research team produced unique large extent study, performed by WATEM/SEDEM model adopted for erosion driven phosphorus fluxes modelling, for the area of 1/3 of the Czech Republic (ca 31500 km2) in the resolution (pixel size) of 10 by 10 meters, with estimated connectivity from single field to outlet reservoirs of large catchments, including stream topology, sediment trapping efficiencies of all ponds and reservoirs within

  6. Modeling suspended sediment transport and assessing the impacts of climate change in a karstic Mediterranean watershed.

    Science.gov (United States)

    Nerantzaki, S D; Giannakis, G V; Efstathiou, D; Nikolaidis, N P; Sibetheros, I Α; Karatzas, G P; Zacharias, I

    2015-12-15

    Mediterranean semi-arid watersheds are characterized by a climate type with long periods of drought and infrequent but high-intensity rainfalls. These factors lead to the formation of temporary flow tributaries which present flashy hydrographs with response times ranging from minutes to hours and high erosion rates with significant sediment transport. Modeling of suspended sediment concentration in such watersheds is of utmost importance due to flash flood phenomena, during which, large quantities of sediments and pollutants are carried downstream. The aim of this study is to develop a modeling framework for suspended sediment transport in a karstic watershed and assess the impact of climate change on flow, soil erosion and sediment transport in a hydrologically complex and intensively managed Mediterranean watershed. The Soil and Water Assessment Tool (SWAT) model was coupled with a karstic flow and suspended sediment model in order to simulate the hydrology and sediment yield of the karstic springs and the whole watershed. Both daily flow data (2005-2014) and monthly sediment concentration data (2011-2014) were used for model calibration. The results showed good agreement between observed and modeled values for both flow and sediment concentration. Flash flood events account for 63-70% of the annual sediment export depending on a wet or dry year. Simulation results for a set of IPCC "A1B" climate change scenarios suggested that major decreases in surface flow (69.6%) and in the flow of the springs (76.5%) take place between the 2010-2049 and 2050-2090 time periods. An assessment of the future ecological flows revealed that the frequency of minimum flow events increases over the years. The trend of surface sediment export during these periods is also decreasing (54.5%) but the difference is not statistically significant due to the variability of the sediment. On the other hand, sediment originating from the springs is not affected significantly by climate change.

  7. Adsorption and desorption of arsenate on sandy sediments from contaminated and uncontaminated saturated zones: Kinetic and equilibrium modeling.

    Science.gov (United States)

    Hafeznezami, Saeedreza; Zimmer-Faust, Amity G; Dunne, Aislinn; Tran, Tiffany; Yang, Chao; Lam, Jacquelyn R; Reynolds, Matthew D; Davis, James A; Jay, Jennifer A

    2016-08-01

    Application of empirical models to adsorption of contaminants on natural heterogeneous sorbents is often challenging due to the uncertainty associated with fitting experimental data and determining adjustable parameters. Sediment samples from contaminated and uncontaminated portions of a study site in Maine, USA were collected and investigated for adsorption of arsenate [As(V)]. Two kinetic models were used to describe the results of single solute batch adsorption experiments. Piecewise linear regression of data linearized to fit pseudo-first order kinetic model resulted in two distinct rates and a cutoff time point of 14-19 h delineating the biphasic behavior of solute adsorption. During the initial rapid adsorption stage, an average of 60-80% of the total adsorption took place. Pseudo-second order kinetic models provided the best fit to the experimental data (R(2) > 0.99) and were capable of describing the adsorption over the entire range of experiments. Both Langmuir and Freundlich isotherms provided reasonable fits to the adsorption data at equilibrium. Langmuir-derived maximum adsorption capacity (St) of the studied sediments ranged between 29 and 97 mg/kg increasing from contaminated to uncontaminated sites. Solid phase As content of the sediments ranged from 3.8 to 10 mg/kg and the As/Fe ratios were highest in the amorphous phase. High-pH desorption experiments resulted in a greater percentage of solid phase As released into solution from experimentally-loaded sediments than from the unaltered samples suggesting that As(V) adsorption takes place on different reversible and irreversible surface sites.

  8. Advanced methods of solid oxide fuel cell modeling

    CERN Document Server

    Milewski, Jaroslaw; Santarelli, Massimo; Leone, Pierluigi

    2011-01-01

    Fuel cells are widely regarded as the future of the power and transportation industries. Intensive research in this area now requires new methods of fuel cell operation modeling and cell design. Typical mathematical models are based on the physical process description of fuel cells and require a detailed knowledge of the microscopic properties that govern both chemical and electrochemical reactions. ""Advanced Methods of Solid Oxide Fuel Cell Modeling"" proposes the alternative methodology of generalized artificial neural networks (ANN) solid oxide fuel cell (SOFC) modeling. ""Advanced Methods

  9. A GIS approach to model sediment reduction susceptibility of mixed sand and gravel beaches.

    Science.gov (United States)

    Eikaas, Hans S; Hemmingsen, Maree A

    2006-06-01

    The morphological form of mixed sand and gravel beaches is distinct, and the process/response system and complex dynamics of these beaches are not well understood. Process response models developed for pure sand or gravel beaches cannot be directly applied to these beaches. The Canterbury Bight coastline is apparently abundantly supplied with sediments from large rivers and coastal alluvial cliffs, but a large part of this coastline is experiencing long-term erosion. Sediment budget models provide little evidence to suggest sediments are stored within this system. Current sediment budget models inadequately quantify and account for the processes responsible for the patterns of erosion and accretion of this coastline. We outline a new method to extrapolate from laboratory experiments to the field using a geographical information system approach to model sediment reduction susceptibility for the Canterbury Bight. Sediment samples from ten representative sites were tumbled in a concrete mixer for an equivalent distance of 40 km. From the textural mixture and weight loss over 40 km tumbling, we applied regression techniques to generate a predictive equation for Sediment Reduction Susceptibility (SRS). We used Inverse Distance Weighting (IDW) to extrapolate the results from fifty-five sites with data on textural sediment composition to field locations with no data along the Canterbury Bight, creating a continuous sediment reductions susceptibility surface. Isolines of regular SRS intervals were then derived from the continuous surface to create a contour map of sediment reductions susceptibility for the Canterbury Bight. Results highlighted the variability in SRS along this coastline.

  10. The use of heavy metal top soil concentrations for the validation of overbank floodplain sedimentation models

    Science.gov (United States)

    Büttner, Olaf; Rode, Michael; Schulz, Marcus

    2010-05-01

    In floodplains of lowland rivers, the transport, sedimentation, and remobilization of fine sediments is highly variable in space and time. Therefore, it is often difficult to validate sediment transport models due to the lack of appropriate data. The objective of this study is to show that heavy metal concentrations in the top soil (upper 15 cm) of a highly polluted floodplain are related to the deposition of fine sediments and thus can be used to assess the plausibility of a two-dimensional (2D) hydraulic and sediment transport model. In a floodplain, heavy metals are bonded to fine sediments, and the deposition of heavy metals originates from a long history of floods. Heavy metal concentrations can be used as a time-integrated indicator of sedimentation, if during a defined period of heavy metal contamination the total deposition of fine sediments is less than a defined topsoil sampling depth. We provided evidence for this hypothesis studying a 45km²-floodplain of River Mulde (Germany). For the assessment of heavy metal top soil concentrations, 126 samples were available. Hydraulics, sedimentation patterns, and concentrations of particle-bonded pollutants were calculated with a 2D computational fluid dynamics (CFD) model (TELEMAC 2D). The calibration of critical velocities of sedimentation and erosion of the model was based on sediment trap exposures during a flood event with a ten-year recurrence interval (Schulz et al. 2009). The calculated sedimentation of the calibrated model was subdivided into three classes: low sedimentation ( 1mm). Heavy metal concentrations of the floodplain soil were classified according to these simulated spatially distributed sedimentation classes. The analysis of the measured and modelled values clearly showed that the mean values of the classified concentrations of arsenic (As), lead (Pb), cadmium (Cd), and zinc (Zn) were increasing with increasing simulated sedimentation rates. Cd and Zn showed the clearest correlation between top

  11. Sediment Transport Model For Storm Sewer Networks Towards The Operational Risks

    Directory of Open Access Journals (Sweden)

    I. RÁTKY

    2016-11-01

    Full Text Available Sediment transport in sewer networks can be critical in economical and safety point of view. To improve the operation of the sewer networks we are presenting a model, which is capable of numerical simulations of the sediment transport in storm water network. The developed model is calculating the change of the particle distribution of the sediment fractions including the effects of settling and mixing up processes. The results of the model calculations in a simplified network are also presented. We are also planning to apply the developed sediment transport module by coupling to a hydrodynamic simulation for practical tasks supporting the design and operation of sewers networks.

  12. MODELING A SOLID BOUNDARY AS A FLUID OF INFINITE VISCOSITY

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new approach to model viscosity in the conservation of momentum equations is presented and discussed. Coefficient of viscosity is modeled in such a way that it reaches asymptotically to infinity at the solid boundary but still yields a finite value for the shear stress at the solid wall. Basic objective of this research is to show that certain combinations of higher order normal velocity gradients become zero at the solid boundary.Modified solutions for the Couette flow and Poiseuille flow between two parallel plates are obtained by modeling the coefficient of viscosity in a novel way. Also,viscous drag computed by our model is expected to yield higher values than the values predicted by the existing models, which matches closely to the experimental data.

  13. THCM Coupled Model for Hydrate-Bearing Sediments: Data Analysis and Design of New Field Experiments (Marine and Permafrost Settings)

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Marcelo J. [Texas A & M Univ., College Station, TX (United States); Santamarina, J. Carlos [King Abdullah Univ. of Science and Technology (Saudi Arabia)

    2017-02-14

    Gas hydrates are solid compounds made of water molecules clustered around low molecular weight gas molecules such as methane, hydrogen, and carbon dioxide. Methane hydrates form under pressure (P) and temperature (T) conditions that are common in sub-permafrost layers and in deep marine sediments. Stability conditions constrain the occurrence of gas hydrates to submarine sediments and permafrost regions. The amount of technically recoverable methane trapped in gas hydrate may exceed 104tcf. Gas hydrates are a potential energy resource, can contribute to climate change, and can cause large-scale seafloor instabilities. In addition, hydrate formation can be used for CO2 sequestration (also through CO2-CH4 replacement), and efficient geological storage seals. The experimental study of hydrate bearing sediments has been hindered by the very low solubility of methane in water (lab testing), and inherent sampling difficulties associated with depressurization and thermal changes during core extraction. This situation has prompted more decisive developments in numerical modeling in order to advance the current understanding of hydrate bearing sediments, and to investigate/optimize production strategies and implications. The goals of this research has been to addresses the complex thermo-hydro-chemo-mechanical THCM coupled phenomena in hydrate-bearing sediments, using a truly coupled numerical model that incorporates sound and proven constitutive relations, satisfies fundamental conservation principles. Analytical solutions aimed at verifying the proposed code have been proposed as well. These tools will allow to better analyze available data and to further enhance the current understanding of hydrate bearing sediments in view of future field experiments and the development of production technology.

  14. Energy recovery from solid waste. [production engineering model

    Science.gov (United States)

    Dalton, C.; Huang, C. J.

    1974-01-01

    A recent group study on the problem of solid waste disposal provided a decision making model for a community to use in determining the future for its solid waste. The model is a combination of the following factors: technology, legal, social, political, economic and environmental. An assessment of local or community needs determines what form of energy recovery is desirable. A market for low pressure steam or hot water would direct a community to recover energy from solid waste by incineration to generate steam. A fuel gas could be produced by a process known as pyrolysis if there is a local market for a low heating value gaseous fuel. Solid waste can also be used directly as a fuel supplemental to coal in a steam generator. An evaluation of these various processes is made.

  15. Energy recovery from solid waste. [production engineering model

    Science.gov (United States)

    Dalton, C.; Huang, C. J.

    1974-01-01

    A recent group study on the problem of solid waste disposal provided a decision making model for a community to use in determining the future for its solid waste. The model is a combination of the following factors: technology, legal, social, political, economic and environmental. An assessment of local or community needs determines what form of energy recovery is desirable. A market for low pressure steam or hot water would direct a community to recover energy from solid waste by incineration to generate steam. A fuel gas could be produced by a process known as pyrolysis if there is a local market for a low heating value gaseous fuel. Solid waste can also be used directly as a fuel supplemental to coal in a steam generator. An evaluation of these various processes is made.

  16. Estimating reservoir sedimentation using bathymetric differencing and hydrologic modeling in data scarce Koga watershed, Upper Blue Nile

    OpenAIRE

    Demesew Alemaw Mhiret; Ayana, Essayas K.; Elias S. Legesse; Michael M. Moges; Seifu A. Tilahun; Moges, Mamaru A.

    2016-01-01

    ABSTRACT Modeling sediment accumulation in constructed reservoirs is hampered by lack of historic sediment concentration data in developing countries. Existing models simulate sediment concentration using data generated from sediment rating curves usually defined as a power function of the form S = aQb This often results in residual errors that are not identically distributed throughout the range of stream flow values adding to uncertainty in sediment modeling practices. This researc...

  17. Numerical model for sedimentation in the access channel and harbor basin of Belawan Port

    Institute of Scientific and Technical Information of China (English)

    Hang Tuah. Salim

    2010-01-01

    Belawan is the largest port serving North Sumatra for the import and export.Port has facilities for handling container, CPO liquid bulk cargo,Oil,and other agriculture products.Its location is at the fiver mouth which is subjected to the heavy sedimentation especially after many deforestation activities in its catchment area. The numerical modeling was developed for predicting the rate of sediment caused by erosion in the catchment area for several scenarios.This predicted rate of sediment was applied as input to model of sedimentation in the ocean.Present condition of sedimentation data was used as calibrated data.This integrated model was used to simulate the sedimentation in Belawan access channel and harbor basin for several development plans.

  18. WATEQ3 geochemical model: thermodynamic data for several additional solids

    Energy Technology Data Exchange (ETDEWEB)

    Krupka, K.M.; Jenne, E.A.

    1982-09-01

    Geochemical models such as WATEQ3 can be used to model the concentrations of water-soluble pollutants that may result from the disposal of nuclear waste and retorted oil shale. However, for a model to competently deal with these water-soluble pollutants, an adequate thermodynamic data base must be provided that includes elements identified as important in modeling these pollutants. To this end, several minerals and related solid phases were identified that were absent from the thermodynamic data base of WATEQ3. In this study, the thermodynamic data for the identified solids were compiled and selected from several published tabulations of thermodynamic data. For these solids, an accepted Gibbs free energy of formation, ..delta..G/sup 0//sub f,298/, was selected for each solid phase based on the recentness of the tabulated data and on considerations of internal consistency with respect to both the published tabulations and the existing data in WATEQ3. For those solids not included in these published tabulations, Gibbs free energies of formation were calculated from published solubility data (e.g., lepidocrocite), or were estimated (e.g., nontronite) using a free-energy summation method described by Mattigod and Sposito (1978). The accepted or estimated free energies were then combined with internally consistent, ancillary thermodynamic data to calculate equilibrium constants for the hydrolysis reactions of these minerals and related solid phases. Including these values in the WATEQ3 data base increased the competency of this geochemical model in applications associated with the disposal of nuclear waste and retorted oil shale. Additional minerals and related solid phases that need to be added to the solubility submodel will be identified as modeling applications continue in these two programs.

  19. Applicative limitations of sediment transport on predictive modeling in geomorphology

    Institute of Scientific and Technical Information of China (English)

    WEIXiang; LIZhanbin

    2004-01-01

    Sources of uncertainty or error that arise in attempting to scale up the results of laboratory-scale sediment transport studies for predictive modeling of geomorphic systems include: (i) model imperfection, (ii) omission of important processes, (iii) lack of knowledge of initial conditions, (iv) sensitivity to initial conditions, (v) unresolved heterogeneity, (vi) occurrence of external forcing, and (vii) inapplicability of the factor of safety concept. Sources of uncertainty that are unimportant or that can be controlled at small scales and over short time scales become important in large-scale applications and over long time scales. Control and repeatability, hallmarks of laboratory-scale experiments, are usually lacking at the large scales characteristic of geomorphology. Heterogeneity is an important concomitant of size, and tends to make large systems unique. Uniqueness implies that prediction cannot be based upon first-principles quantitative modeling alone, but must be a function of system history as well. Periodic data collection, feedback, and model updating are essential where site-specific prediction is required.

  20. A solid-fluid mixture model allowing for solid dilatation under external pressure

    CERN Document Server

    Sciarra, Giulio; Hutter, Kolumban

    2010-01-01

    A sponge subjected to an increase of the outside fluid pressure expands its volume but nearly mantains its true density and thus gives way to an increase of the interstitial volume. This behaviour, not yet properly described by solid-fluid mixture theories, is studied here by using the Principle of Virtual Power with the most simple dependence of the free energy as a function of the partial apparent densities of the solid and the fluid. The model is capable of accounting for the above mentioned dilatational behaviour, but in order to isolate its essential features more clearly we compromise on the other aspects of deformation.

  1. Biomass torrefaction: modeling of volatile and solid product evolution kinetics.

    Science.gov (United States)

    Bates, Richard B; Ghoniem, Ahmed F

    2012-11-01

    The aim of this work is the development of a kinetics model for the evolution of the volatile and solid product composition during torrefaction conditions between 200 and 300°C. Coupled to an existing two step solid mass loss kinetics mechanism, this model describes the volatile release kinetics in terms of a set of identifiable chemical components, permitting the solid product composition to be estimated by mass conservation. Results show that most of the volatiles released during the first stage include highly oxygenated species such as water, acetic acid, and carbon dioxide, while volatiles released during the second step are composed primarily of lactic acid, methanol, and acetic acid. This kinetics model will be used in the development of a model to describe reaction energy balance and heat release dynamics.

  2. Geoacoustic model of surface sediments in the southwestern Ulleung basin, the East Sea of Korea

    Science.gov (United States)

    Kim, S. H.; Kim, D. C.; Lee, G. S.; Kim, S. P.; Bae, S. H.

    2012-04-01

    To realization of geoacoustic model in the southwestern Ulleung basin, the East Sea of Korea, eighty-two piston core samples and sixty-six box core samples were collected. Sediment texture (mean grain size and sand, silt, and clay contents), physical properties (porosity, water content, bulk density, and grain density), and acoustic properties (compressional wave velocity and attenuation) were measured using surface sediments below 40 cm from the surface. As the results, the study area is divided into five sub-areas based on acoustic property of sediments: (1) Area I is composed of muddy sediments that affected directly by the Nakdong River discharge. The velocity is almost 1490 m/s. (2) Area II is generally characterized by hemi-pelagic muds and partially mixed with intermittent sandy sediments originated from the outer shelf and upper slope. The velocity approximately ranges from 1490 to 1500 m/s. (3) Area III is comprised of muddy sand sediments that are corresponds to the boundary between recent sediments and relict sediments. The velocity ranges from 1500 to 1600 m/s. (4) Area IV is dominated by coarse-grained relict sediments. The velocity ranges from 1600 to 1700 m/s. And (5) Area V consists of very coarser sediments. The velocity is higher than 1700 m/s. The sediment velocity generally decreases with increasing porosity or decreasing mean grain size and bulk density.

  3. A new settling velocity model to describe secondary sedimentation.

    Science.gov (United States)

    Ramin, Elham; Wágner, Dorottya S; Yde, Lars; Binning, Philip J; Rasmussen, Michael R; Mikkelsen, Peter Steen; Plósz, Benedek Gy

    2014-12-01

    Secondary settling tanks (SSTs) are the most hydraulically sensitive unit operations in biological wastewater treatment plants. The maximum permissible inflow to the plant depends on the efficiency of SSTs in separating and thickening the activated sludge. The flow conditions and solids distribution in SSTs can be predicted using computational fluid dynamics (CFD) tools. Despite extensive studies on the compression settling behaviour of activated sludge and the development of advanced settling velocity models for use in SST simulations, these models are not often used, due to the challenges associated with their calibration. In this study, we developed a new settling velocity model, including hindered, transient and compression settling, and showed that it can be calibrated to data from a simple, novel settling column experimental set-up using the Bayesian optimization method DREAM(ZS). In addition, correlations between the Herschel-Bulkley rheological model parameters and sludge concentration were identified with data from batch rheological experiments. A 2-D axisymmetric CFD model of a circular SST containing the new settling velocity and rheological model was validated with full-scale measurements. Finally, it was shown that the representation of compression settling in the CFD model can significantly influence the prediction of sludge distribution in the SSTs under dry- and wet-weather flow conditions.

  4. Cross-shore sediment transport; analysis of Delta Flume data and mathematical modelling

    NARCIS (Netherlands)

    Zhang, C.

    1994-01-01

    In the last decade, several mathematical models for cross-shore sediment transport have been developed under the assumption that the instantaneous sediment transport is directly related to the instantaneous horizontal velocity just above the boundary layer. Although some models took beach slopes

  5. Cross-shore sediment transport; analysis of Delta Flume data and mathematical modelling

    NARCIS (Netherlands)

    Zhang, C.

    1994-01-01

    In the last decade, several mathematical models for cross-shore sediment transport have been developed under the assumption that the instantaneous sediment transport is directly related to the instantaneous horizontal velocity just above the boundary layer. Although some models took beach slopes int

  6. A Thermodynamic Mixed-Solid Asphaltene Precipitation Model

    DEFF Research Database (Denmark)

    Lindeloff, Niels; Heidemann, R.A.; Andersen, Simon Ivar

    1998-01-01

    A simple model for the prediction of asphaltene precipitation is proposed. The model is based on an equation of state and uses standard thermodynamics, thus assuming that the precipitation phenomenon is a reversible process. The solid phase is treated as an ideal multicomponent mixture. An activity...

  7. Principles and approaches for numerical modelling of sediment transport in sewers

    DEFF Research Database (Denmark)

    Mark, Ole; Larsen, Torben; Appelgren, Cecilia

    1994-01-01

    A study has been carried out at the University of Aalborg, Denmark and VBB VIAK, Sweden with the objectives to describe the effect of sediment deposits on the hydraulic capacity of sewer systems and to investigate the sediment transport in sewer systems. A results of the study is a mathematical...... model MOUSE ST which describes the sediment transport in sewers. This paper discusses the applicability and the limitations of various modelling approaches and sediment transport formulations in MOUSE ST. The study was founded by the Swedish Water and Waste Works Association and the Nordic Industrial...

  8. Principles and Approaches for Numerical Modelling of Sediment Transport in Sewers

    DEFF Research Database (Denmark)

    Mark, Ole; Appelgren, Cecilia; Larsen, Torben

    1995-01-01

    A study has been carried out with the objectives of describing the effect of sediment deposits on the hydraulic capacity of sewer systems and to investigate the sediment transport in sewer systems. A result of the study is a mathematical model MOUSE ST which describes sediment transport in sewers....... This paper discusses the applicability and the limitations of various modelling approaches and sediment transport formulations in in MOUSE ST. Further, the paper presents a simple application of MOUSE ST to the Rya catchment in Gothenburg, Sweden....

  9. Mathematical model for interactions and transport of phosphorus and sediment in the Three Gorges Reservoir.

    Science.gov (United States)

    Huang, Lei; Fang, Hongwei; Reible, Danny

    2015-11-15

    Phosphorus fate and transport in natural waters plays a crucial role in the ecology of rivers and reservoirs. In this paper, a coupled model of hydrodynamics, sediment transport, and phosphorus transport is established, in which the effects of sediment on phosphorus transport are considered in detail. Phosphorus adsorption is estimated using a mechanistic surface complexation model which is capable of simulating the adsorption characteristics under various aquatic chemistry conditions. The sediment dynamics are analyzed to evaluate the deposition and release of phosphorus at the bed surface. In addition, the aerobic layer and anaerobic layer of the sediments are distinguished to study the distribution of phosphorus between dissolved and particulate phases in the active sediment layer. The proposed model is applied to evaluate the effects of various operating rules on sediment and phosphorus retention in the Three Gorges Reservoir (TGR). Results show that the proposed model can reasonably reflect the phosphorus transport with sediment, and management scenarios that influence sediment retention will also influence the phosphorus balance in the TGR. However, modest operational changes which have only minor effects on sediment retention also have limited influence on the phosphorous balance. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. An effective Euler-Lagrange model for suspended sediment transport by open channel flows

    Institute of Scientific and Technical Information of China (English)

    Huabin Shi; Xiping Yu n

    2015-01-01

    An Euler–Lagrange two-phase flow model is developed to study suspended sediment transport by open-channel flows with an Eddy Interaction Model (EIM) applied to consider the effect of fluid turbulence on sediment diffusion. For the continuous phase, the mean fluid velocity, the turbulent kinetic energy and its dissipation rate are directly estimated by well-established empirical formulas. For the dispersed phase, sediment particles are tracked by solving the equation of motion. The EIM is applied to compute the particle fluctuation velocity. Neglecting the effect of particles on flow turbulence as usually suggested for dilute cases in the literature, the Euler–Lagrange model is applied to simulate suspended sediment transport in open channels. Although the numerical results agree well with those by the well-known random walk particle tracking model (RWM) and with the laboratory data for fine sediment cases, it is clearly shown that such an Euler–Lagrange model underestimates the sediment concentration for the medium-sized and coarse sediment cases. To improve the model, a formula is proposed to consider the local fluid turbulence enhancement around a particle due to vortex shedding in the wake. Numerical results of the modified model then agree very well with laboratory data for not only the fine but also the coarse sediment cases.

  11. Geometric data transfer between CAD systems: solid models

    DEFF Research Database (Denmark)

    Kroszynski, Uri; Palstroem, Bjarne; Trostmann, Erik

    1989-01-01

    The first phase of the ESPRIT project CAD*I resulted in a specification for the exchange of solid models as well as in some pilot implementations of processors based on this specification. The authors summarize the CAD*I approach, addressing the structure of neutral files for solids, entities......, and attributes supporting three kinds of representations: facilities for the transfer of parametric designs; referencing library components; and other general mechanisms. They also describe the current state of the specification and processor implementations and include an example of a CAD*I neutral file....... Results from cycle and intersystem solid model transfer tests are presented, showing the practicality of the CAD*I proposal. B-rep model transfer results are discussed in some detail. The relationship of this work to standardization efforts is outlined...

  12. Modeling and Design of Semi-Solid Flow Batteries

    Science.gov (United States)

    Brunini, Victor Eric

    A three-dimensional dynamic model of the recently introduced semi-solid flow battery system is developed and applied to address issues with important design and operation implications. Because of the high viscosity of semi-solid flow battery suspensions, alternative modes of operation not typically used in conventional redox flow battery systems must be explored to reduce pumping energy losses. Modeling results are presented .and compared to experimental observations to address important considerations for both stoichiometric and intermittent flow operation. The importance of active material selection, and its impact on efficient stoichiometric flow operation is discussed. Electrochemically active zone considerations relevant to intermittent flow operation of semi-solid flow batteries (or other potential electronically conductive flow battery systems) are addressed. Finally, the use of the model as a design tool for optimizing flow channel design to improve system level performance is demonstrated.(Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs@mit.edu)

  13. New modeling paradigms for the sorption of hydrophobic organic chemicals to heterogeneous carbonaceous matter in soils, sediments, and rocks

    Science.gov (United States)

    Allen-King, Richelle M.; Grathwohl, Peter; Ball, William P.

    Heterogeneity in naturally occurring carbonaceous materials (CMs) causes sorbed hydrophobic organic compound (HOC) concentrations in soils, sediments, and rocks to occur as a combination of surface adsorption and phase partitioning, with the latter typically more linearly dependent on aqueous concentration. In this manuscript, we describe a model to simulate HOC sorption as the combined effect of adsorption to thermally altered CM and a more linear solvation-driven absorption into gel-like CM (organic matter). We describe different forms of thermally altered CM (such as soots, chars, coals, and kerogen), the manner in which these materials can serve as especially strong adsorbents, and the conditions under which they can control solid-aqueous distribution. Specific examples of model fits to soil, sediment and rock samples with identified thermally altered CM components provide a linkage between sorption components and sorbent material properties. Because both the adsorption and partition components are scalable by compound solubility, it may often be possible to estimate nonlinear isotherms for a wide range of chemicals based on comparatively few experimental measurements. Thermally altered CM is widespread in the environment and can serve as an important sorbent even when present in small quantities (especially at low concentrations of adsorbates). In this context, the sorption modeling refinements described in this work are expected to have wide applicability. Given that solid/water distribution is a central process affecting contaminant fate, such refined models are an essential element for better estimates of risk and improved remediation design.

  14. In search of a better sediment mixing coefficient model

    NARCIS (Netherlands)

    Voorendt, M.; Van de Graaf, J.

    1994-01-01

    Results of sediment transport calculations are often necessary in solving practical coastal engineering problems. (Sediment transport due to waves and currents). Many transport formulae have been proposed in literature in the past. Selection of the proper one while solving a particular problem, is a

  15. Waves, Hydrodynamics and Sediment Transport Modeling at Grays Harbor, WA

    Science.gov (United States)

    2010-12-01

    flocculation of cohesive sediment. IAHR J. Hydraul . Res. 36 (3), 309-326. Winterwerp, J. C., and W. G. M. van Kesteren. 2004. Introduction to the...Coastal and Hydraulics Laboratory U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199 David R. Michalsen...93  Sediment processes during dredged material placement operations

  16. Sediment yield model implementation based on check dam infill stratigraphy in a semiarid Mediterranean catchment

    Directory of Open Access Journals (Sweden)

    G. Bussi

    2013-08-01

    Full Text Available Soil loss and sediment transport in Mediterranean areas are driven by complex non-linear processes which have been only partially understood. Distributed models can be very helpful tools for understanding the catchment-scale phenomena which lead to soil erosion and sediment transport. In this study, a modelling approach is proposed to reproduce and evaluate erosion and sediment yield processes in a Mediterranean catchment (Rambla del Poyo, Valencia, Spain. Due to the lack of sediment transport records for model calibration and validation, a detailed description of the alluvial stratigraphy infilling a check dam that drains a 12.9 km2 sub-catchment was used as indirect information of sediment yield data. These dam infill sediments showed evidences of at least 15 depositional events (floods over the time period 1990–2009. The TETIS model, a distributed conceptual hydrological and sediment model, was coupled to the Sediment Trap Efficiency for Small Ponds (STEP model for reproducing reservoir retention, and it was calibrated and validated using the sedimentation volume estimated for the depositional units associated with discrete runoff events. The results show relatively low net erosion rates compared to other Mediterranean catchments (0.136 Mg ha−1 yr−1, probably due to the extensive outcrops of limestone bedrock, thin soils and rather homogeneous vegetation cover. The simulated sediment production and transport rates offer model satisfactory results, further supported by in-site palaeohydrological evidences and spatial validation using additional check dams, showing the great potential of the presented data assimilation methodology for the quantitative analysis of sediment dynamics in ungauged Mediterranean basins.

  17. Regional Sediment Management (RSM) Modeling Tools: Integration of Advanced Sediment Transport Tools into HEC-RAS

    Science.gov (United States)

    2014-06-01

    Regional Sediment Management (RSM) Point of Contact, Dr. Paul M. Boyd (Paul.M.Boyd@ usace.army.mil), or to Dr. Standford A. Gibson (Stanford.Gibson...Parker. 2004. Experiments on upstream-migrating erosional narrowing and widening of an incisional channel caused by dam removal. Water Resources

  18. Suspended-sediment concentrations, yields, total suspended solids, turbidity, and particle-size fractions for selected rivers in Minnesota, 2007 through 2011

    Science.gov (United States)

    Ellison, Christopher A.; Savage, Brett E.; Johnson, Gregory D.

    2015-01-01

    Excessive sediment transport in rivers causes problems for flood control, soil conservation, irrigation, aquatic health, and navigation, as well as transporting harmful contaminants like organic chemicals and eutrophication-causing nutrients. In Minnesota, more than 5,800 miles of streams are identified as impaired by the Minnesota Pollution Control Agency (MPCA) due to elevated levels of suspended sediment. The U.S. Geological Survey, in cooperation with the MPCA, established a sediment monitoring network in 2007 and began systematic sampling of suspended-sediment concentration (SSC), total suspended solids (TSS), and turbidity in rivers across Minnesota to improve the understanding of fluvial sediment transport relations. Suspended-sediment samples were collected from 14 sites from 2007 through 2011. Analyses of these data indicated that the Zumbro River at Kellogg in southeast Minnesota had the highest mean SSC of 226 milligrams per liter (mg/L) followed by the Minnesota River at Mankato with a mean SSC of 193 mg/L. The single highest SSC of 1,250 mg/L was measured at the Zumbro River during the 2011 spring runoff. The lowest mean SSC of 21 mg/L was measured at Rice Creek in the northern Minneapolis-St. Paul metropolitan area. Total suspended solids (TSS) have been used as a measure of fluvial sediment by the MPCA since the early 1970s; however, TSS concentrations have been known to underrepresent the amount of suspended sediment. For this study, comparisons between concurrently sampled SSC and TSS indicated significant differences at every site, with SSC on average two times larger than TSS concentrations. Regression analysis indicated that 7 out of 14 sites had poor or no relation between SSC and streamflow. Only two sites, the Knife River and the Wild Rice River at Twin Valley, had strong correlations between SSC and streamflow, with coefficient of determination (R2) values of 0.82 and 0.80, respectively. In contrast, turbidity had moderate to strong

  19. Multivariate Statistical Models for Predicting Sediment Yields from Southern California Watersheds

    Science.gov (United States)

    Gartner, Joseph E.; Cannon, Susan H.; Helsel, Dennis R.; Bandurraga, Mark

    2009-01-01

    Debris-retention basins in Southern California are frequently used to protect communities and infrastructure from the hazards of flooding and debris flow. Empirical models that predict sediment yields are used to determine the size of the basins. Such models have been developed using analyses of records of the amount of material removed from debris retention basins, associated rainfall amounts, measures of watershed characteristics, and wildfire extent and history. In this study we used multiple linear regression methods to develop two updated empirical models to predict sediment yields for watersheds located in Southern California. The models are based on both new and existing measures of volume of sediment removed from debris retention basins, measures of watershed morphology, and characterization of burn severity distributions for watersheds located in Ventura, Los Angeles, and San Bernardino Counties. The first model presented reflects conditions in watersheds located throughout the Transverse Ranges of Southern California and is based on volumes of sediment measured following single storm events with known rainfall conditions. The second model presented is specific to conditions in Ventura County watersheds and was developed using volumes of sediment measured following multiple storm events. To relate sediment volumes to triggering storm rainfall, a rainfall threshold was developed to identify storms likely to have caused sediment deposition. A measured volume of sediment deposited by numerous storms was parsed among the threshold-exceeding storms based on relative storm rainfall totals. The predictive strength of the two models developed here, and of previously-published models, was evaluated using a test dataset consisting of 65 volumes of sediment yields measured in Southern California. The evaluation indicated that the model developed using information from single storm events in the Transverse Ranges best predicted sediment yields for watersheds in San

  20. Solid-on-solid model for surface growth in 2+1 dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinabadi, S. [Department of Physics, Alzahra University, P.O. Box 19938, Tehran 91167 (Iran, Islamic Republic of); Masoudi, A.A., E-mail: amasoudi@math.uwaterloo.c [Department of Physics, Alzahra University, P.O. Box 19938, Tehran 91167 (Iran, Islamic Republic of); Department of Applied Mathematics, University of Waterloo, Waterloo, ON, N2L 3G1 (Canada); Sadegh Movahed, M. [Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of)

    2010-04-15

    We analyze in detail the solid-on-solid (SOS) model for growth processes on a square substrate in 2+1 dimensions. By using the Markovian surface properties, we introduce an alternative approach for determining the roughness exponent of a special type of SOS model-the restricted-solid-on-solid (RSOS) model-in 2+1 dimensions. This model is the SOS model with the additional restriction that the height difference must be S=1. Our numerical results show that the behavior of the SOS model in 2+1 dimensions for approximately S>=S{sub x}approx8 belongs to the two different universality classes: during the initial time stage, t

  1. Two types of glitches in a solid quark star model

    CERN Document Server

    Lu, Jiguang

    2015-01-01

    The glitch of anomalous X-ray pulsars \\& soft gamma repeaters (AXP/SGRs) usually accompanied with detectable energy releases manifesting as X-ray bursts or outbursts, while the glitch of some pulsars like Vela release negligible energy. We find that these two types of glitch can naturally correspond to two types of starquake of solid stars. So far only quark star and quark cluster star model develop a solid star model. Then the two types of glitch may be an implication that the pulsar is composed by quark matter or quark cluster matter.

  2. A user-friendly modified pore-solid fractal model

    OpenAIRE

    Dian-yuan Ding; Ying Zhao; Hao Feng; Bing-cheng Si; Robert Lee Hill

    2016-01-01

    The primary objective of this study was to evaluate a range of calculation points on water retention curves (WRC) instead of the singularity point at air-entry suction in the pore-solid fractal (PSF) model, which additionally considered the hysteresis effect based on the PSF theory. The modified pore-solid fractal (M-PSF) model was tested using 26 soil samples from Yangling on the Loess Plateau in China and 54 soil samples from the Unsaturated Soil Hydraulic Database. The derivation results s...

  3. A Sedimentation-Dispersion Model for both Non-attached and Attached Particles in Three-Phase Batchwise Fluidized Beds

    Institute of Scientific and Technical Information of China (English)

    张济宇; 林诚; 林春深

    2002-01-01

    The axial concentration distribution of both particles with better wetting (forming non-attached system)and poorer wetting (forming attached system) was investigated in a vertical gas-liquid-solid fluidized bed of 4.2 cm indiameter and 130 cm in height with the solids holdup less than 0.05. The one-dimensional sedimentation-dispersionmodel could be used satisfactorily to describe the axial distribution of solids holdup by modifying only a modelparameter, i.e. by means of the terminal settling velocity minus a certain value, which is a function of gas velocityand considers the effect of an additional drag force resulted from attached rising bubbles. The axial profiles of solidconcentration predicted are in good agreement with experimental results. This model also explains reasonably thedifferent axial distributions of solid concentration, i.e. the solids holdup decreases as the axial height increases innon-attached system, but increases with the axial height in attached system at a given gas velocity.

  4. A three-dimensional k-ε-k_p model in curvilinear coordinates for sediment movement and bed evolution

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    To aim at the substitution of the magnitude and direction of water flow movement near bed for those of bed load transport in solid-liquid two-phase one-fluid model, and to simulate the effect of secondary flow on transverse bed load transport in channel bends and the effect of bed slope on bed load trans- port in a better way, a three-dimensional k-ε-kp solid-liquid two-phase two-fluid model in curvilinear coordinates is solved numerically with a finite-volume method on an adaptive grid for studying wa- ter-sediment movements and bed evolution in a 120° channel bend. Numerical results show that the trajectories of solid-phase deviate from those of liquid-phase in the channel bend, and the deviation increases with the increase of the particle diameters. The calculated bed deformation by the k-ε-kp model is in better agreement with measured bed deformation than those by one-fluid model. It is proved that the k-ε-kp model can simulate the effect of secondary flow on lateral bed load transport with the higher accuracy than the one-fluid model.

  5. Hypolyminetic Oxygen Depletion And Dynamics of P Binding Forms: Insights From Modeling Sediment Early Diagenesis Coupled With Automatic Parameter Estimation

    Science.gov (United States)

    Shafei, Babak; Schmid, Martin; Müller, Beat; Chwalek, Thomas

    2014-05-01

    the present and past deposited OM. The results revealed the transient nature of sediment oxygen uptake and existence of temporal lag associated with benthic oxygen consumption for the aerated versus non-aerated scenarios. The model closely reproduced phosphate partitioning among OM and various redox-sensitive inorganic minerals. The results showed that P associated with OM is the dominant pool as inorganic binding P such as apatite, vivinite and adsorbed P contain a minor fraction of solid phase P. The calculated flux of dissolved P through the SWI under seasonal and decadal variations suggest that oxygen concentration at the SWI and the flux of settling OM along with its composition expressed as the ratio of degradable to inert OM are the major factors that control P release to the overlying water under dynamic forcing. References [1] Couture, R., et al. (2009). "Non steady-stae modeling of arsenic diagenesis in lake sediments." Environmental Science and Technology 44 (1): 197-203. [2] Shafei, B., et al. (2010). "Arsenic sorption in aquatic sediments: equilibrium, kinetic and mixed modeling approaches." Geochimica et cosmochimica acta 74 (12): A938-A938. [3] Torres, N. T., et al. (2013). "Sediment porewater extraction and analysis combining filter tube samplers and capillary electrophoresis." Environmental Science-Processes & Impacts 15(4): 715-720.

  6. Phase field modeling of flexoelectricity in solid dielectrics

    Science.gov (United States)

    Chen, H. T.; Zhang, S. D.; Soh, A. K.; Yin, W. Y.

    2015-07-01

    A phase field model is developed to study the flexoelectricity in nanoscale solid dielectrics, which exhibit both structural and elastic inhomogeneity. The model is established for an elastic homogeneous system by taking into consideration all the important non-local interactions, such as electrostatic, elastic, polarization gradient, as well as flexoelectric terms. The model is then extended to simulate a two-phase system with strong elastic inhomogeneity. Both the microscopic domain structures and the macroscopic effective piezoelectricity are thoroughly studied using the proposed model. The results obtained show that the largest flexoelectric induced polarization exists at the interface between the matrix and the inclusion. The effective piezoelectricity is greatly influenced by the inclusion size, volume fraction, elastic stiffness, and the applied stress. The established model in the present study can provide a fundamental framework for computational study of flexoelectricity in nanoscale solid dielectrics, since various boundary conditions can be easily incorporated into the phase field model.

  7. Empirical model for estimating vertical concentration profiles of re-suspended, sediment-associated contaminants

    Science.gov (United States)

    Zhu, H. W.; Cheng, P. D.; Li, W.; Chen, J. H.; Pang, Y.; Wang, D. Z.

    2017-03-01

    Vertical distribution processes of sediment contaminants in water were studied by flume experiments. Experimental results show that settling velocity of sediment particles and turbulence characteristics are the major hydrodynamic factors impacting distribution of pollutants, especially near the bottom where particle diameter is similar in size to vortex structure. Sediment distribution was uniform along the distance, while contaminant distribution slightly lagged behind the sediment. The smaller the initial sediment concentration was, the more time it took to achieve a uniform concentration distribution for suspended sediment. A contaminants transportation equation was established depending on mass conservation equations. Two mathematical estimation models of pollutant distribution in the overlying water considering adsorption and desorption were devised based on vertical distribution of suspended sediment: equilibrium partition model and dynamic micro-diffusion model. The ratio of time scale between the sediment movement and sorption can be used as the index of the models. When this ratio was large, the equilibrium assumption was reasonable, but when it was small, it might require dynamic micro-diffusion model.

  8. Developing and modelling of ohmic heating for solid food products

    DEFF Research Database (Denmark)

    Feyissa, Aberham Hailu; Frosch, Stina

    such as meat and seafood is not industrially utilized yet. Therefore, the aim of the current work is to model and develop the ohmic heating technology for heating of solid meat and seafood. A 3D mathematical model of coupled heat transfer and electric field during ohmic heating of meat products has been......Heating of solid foods using the conventional technologies is time-consuming due to the fact that heat transfer is limited by internal conduction within the product. This is a big challenge to food manufactures who wish to heat the product faster to the desired core temperature and to ensure more...... uniform quality across the product. Ohmic heating is one of the novel technologies potentially solving this problem by allowing volumetric heating of the product and thereby reducing or eliminating temperature gradients within the product. However, the application of ohmic heating for solid food products...

  9. Mineral Features of Surface Sediments and Analysis of Solid-State Mineral Resources in Southeastern China Sea

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    With the development of modern industry and the increase of human demand, it is increasingly important to prospect and exploit marine mineral resources. Based on the oceanic geological investigation references obtained from the regional geological surveying and mapping of China Sea (“Shantoufu, F-50” 1: 1 000 000) and on the data (“Marine Engineering Geological Investigation Project in the Pearl River Mouth basin in the South China Sea” 1: 200 000), the authors elaborate the grain size composition, mineral composition, mineral features and distribution pattern of the surface sediments in the sea at 114°- 120°E and 20°-24°N. Moreover, the analysis of the regional solid-state mineral resources in the coast of iFujian, Guangdong and the west of Taiwan, shows that the main resources include littoral/neritic placers, littoral/neritic sandy gravel and ferromanganese nodule (crust). In addition, the future focus should be on the placers and sandy gravels in this littoral area.

  10. Explicit Modeling of Solid Ocean Floor in Shallow Underwater Explosions

    Directory of Open Access Journals (Sweden)

    A.P. Walters

    2013-01-01

    Full Text Available Current practices for modeling the ocean floor in underwater explosion simulations call for application of an inviscid fluid with soil properties. A method for modeling the ocean floor as a Lagrangian solid, vice an Eulerian fluid, was developed in order to determine its effects on underwater explosions in shallow water using the DYSMAS solver. The Lagrangian solid bottom model utilized transmitting boundary segments, exterior nodal forces acting as constraints, and the application of prestress to minimize any distortions into the fluid domain. For simplicity, elastic materials were used in this current effort, though multiple constitutive soil models can be applied to improve the overall accuracy of the model. Even though this method is unable to account for soil cratering effects, it does however provide the distinct advantage of modeling contoured ocean floors such as dredged channels and sloped bottoms absent in Eulerian formulations. The study conducted here showed significant differences among the initial bottom reflections for the different solid bottom contours that were modeled. The most important bottom contour effect was the distortion to the gas bubble and its associated first pulse timing. In addition to its utility in bottom modeling, implementation of the non-reflecting boundary along with realistic material models can be used to drastically reduce the size of current fluid domains.

  11. Modelling the erosive effects of sewer flushing using different sediment transport formulae.

    Science.gov (United States)

    Shirazi, R H S M; Campisano, A; Modica, C; Willems, P

    2014-01-01

    A numerical investigation to simulate the cleaning effects of successive flushes over sediment beds in prismatic channels is presented in this paper. The 1D De Saint Venant-Exner equations were used to describe the temporal evolution of the sediment bed after each flush. The predictive capacity of two sediment transport formulae was explored against experimental results from laboratory tests. Results show that the adopted model can successfully describe the evolution of the sediment bed due to the flushes exerted during the experiments, with differences between the used transport formulae depending on the channel invert slope and on the flush energy.

  12. Coupled incompressible Smoothed Particle Hydrodynamics model for continuum-based modelling sediment transport

    Science.gov (United States)

    Pahar, Gourabananda; Dhar, Anirban

    2017-04-01

    A coupled solenoidal Incompressible Smoothed Particle Hydrodynamics (ISPH) model is presented for simulation of sediment displacement in erodible bed. The coupled framework consists of two separate incompressible modules: (a) granular module, (b) fluid module. The granular module considers a friction based rheology model to calculate deviatoric stress components from pressure. The module is validated for Bagnold flow profile and two standardized test cases of sediment avalanching. The fluid module resolves fluid flow inside and outside porous domain. An interaction force pair containing fluid pressure, viscous term and drag force acts as a bridge between two different flow modules. The coupled model is validated against three dambreak flow cases with different initial conditions of movable bed. The simulated results are in good agreement with experimental data. A demonstrative case considering effect of granular column failure under full/partial submergence highlights the capability of the coupled model for application in generalized scenario.

  13. Vertical Distribution of Suspended Sediment under Steady Flow: Existing Theories and Fractional Derivative Model

    Directory of Open Access Journals (Sweden)

    Shiqian Nie

    2017-01-01

    Full Text Available The fractional advection-diffusion equation (fADE model is a new approach to describe the vertical distribution of suspended sediment concentration in steady turbulent flow. However, the advantages and parameter definition of the fADE model in describing the sediment suspension distribution are still unclear. To address this knowledge gap, this study first reviews seven models, including the fADE model, for the vertical distribution of suspended sediment concentration in steady turbulent flow. The fADE model, among others, describes both Fickian and non-Fickian diffusive characteristics of suspended sediment, while the other six models assume that the vertical diffusion of suspended sediment follows Fick’s first law. Second, this study explores the sensitivity of the fractional index of the fADE model to the variation of particle sizes and sediment settling velocities, based on experimental data collected from the literatures. Finally, empirical formulas are developed to relate the fractional derivative order to particle size and sediment settling velocity. These formulas offer river engineers a substitutive way to estimate the fractional derivative order in the fADE model.

  14. Multiple effects of sediment transport and geomorphic processes within flood events:Modelling and understanding

    Institute of Scientific and Technical Information of China (English)

    Mingfu Guan n; NigeLG. Wright; P. AndreWSleigh

    2015-01-01

    Flood events can induce considerable sediment transport which in turn influences flow dynamics. This study investigates the multiple effects of sediment transport in floods through modelling a series of hydraulic scenarios, including small-scale experimental cases and a full-scale glacial outburst flood. A non-uniform, layer-based morphodynamic model is presented which is composed of a combination of three modules: a hydrodynamic model governed by the two-dimensional shallow water equations involving sediment effects;a sediment transport model controlling the mass conservation of sediment;and a bed deformation model for updating the bed elevation. The model is solved by a second-order Godunov-type numerical scheme. Through the modelling of the selected sediment-laden flow events, the interactions of flow and sediment transport and geomorphic processes within flood events are elucidated. It is found that the inclusion of sediment transport increases peak flow discharge, water level and water depth in dam-break flows over a flat bed. For a partial dam breach, sediment material has a blockage effect on the flood dynamics. In comparison with the‘sudden collapse’ of a dam, a gradual dam breach significantly delays the arrival time of peak flow, and the flow hydrograph is changed similarly. Considerable bed erosion and deposition occur within the rapid outburst flood, which scours the river channel severely. It is noted that the flood propagation is accelerated after the incorporation of sediment transport, and the water level in most areas of the channel is reduced.

  15. Sediment and radionuclide transport in rivers: radionuclide transport modeling for Cattaraugus and Buttermilk Creeks, New York

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Y.; Yabusaki, S.B.; Kincaid, C.T.; Skaggs, R.L.; Walters, W.H.

    1982-12-01

    SERATRA, a transient, two-dimensional (laterally-averaged) computer model of sediment-contaminant transport in rivers, satisfactorily resolved the distribution of sediment and radionuclide concentrations in the Cattaraugus Creek stream system in New York. By modeling the physical processes of advection, diffusion, erosion, deposition, and bed armoring, SERATRA routed three sediment size fractions, including cohesive soils, to simulate three dynamic flow events. In conjunction with the sediment transport, SERATRA computed radionuclide levels in dissolved, suspended sediment, and bed sediment forms for four radionuclides (/sup 137/Cs, /sup 90/Sr, /sup 239/ /sup 240/Pu, and /sup 3/H). By accounting for time-dependent sediment-radionuclide interaction in the water column and bed, SERATA is a physically explicit model of radionuclide fate and migration. Sediment and radionuclide concentrations calculated by SERATA in the Cattaraugus Creek stream system are in reasonable agreement with measured values. SERATRA is in the field performance phase of an extensive testing program designed to establish the utility of the model as a site assessment tool. The model handles not only radionuclides but other contaminants such as pesticides, heavy metals and other toxic chemicals. Now that the model has been applied to four field sites, including the latest study of the Cattaraugus Creek stream system, it is recommended that a final model be validated through comparison of predicted results with field data from a carefully controlled tracer test at a field site. It is also recommended that a detailed laboratory flume be tested to study cohesive sediment transport, deposition, and erosion characteristics. The lack of current understanding of these characteristics is one of the weakest areas hindering the accurate assessment of the migration of radionuclides sorbed by fine sediments of silt and clay.

  16. Modeling sediment transport in the lower Yellow River and dynamic equilibrium threshold value

    Institute of Scientific and Technical Information of China (English)

    HU; Chunhong; GUO; Qingchao

    2004-01-01

    A major problem in the lower Yellow River is the insufficient incoming water and excessive sediment supply, which results in serious deposition, continuous rise of the river bed, and austere flood control situation. To understand the sediment transport regularity of the lower Yellow River and determine the relationship between sedimentation,incoming water and sediment, and zone water diversion, a mathematical model of the sediment suitable for the characteristics of the lower Yellow River has been developed.This model is first rated and verified by large quantity of observed data, and it is then used to analyze silting reduction for the lower Yellow River by Xiaolangdi Reservoir's operation,the relationship between zone water diversion and channel sedimentation, and critical equilibrium of sedimentation in the lower Yellow River. The threshold values of equilibrium of sedimentation in the lower Yellow River are estimated and they suggest that deposition in the lower Yellow River can be effectively reduced by the operation of regulating flow and sediment from Xiaolangdi Reservoir, water-soil conservation, and controlling water diversion along the lower Yellow River.

  17. A MATHEMATICAL MODEL FOR UNSTEADY SEDIMENT TRANSPORT IN THE LOWER YELLOW RIVER

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hongwu; HUANG Yuandong; ZHAO Lianjun

    2001-01-01

    A one-dimensional mathematical model for unsteady sediment transport in the Lower Yellow River is developed. A coefficient of sediment distribution is defined to represent the ratio of the bottom to the average concentration under the equilibrium conditions. The coefficient is not constant and is evaluated by using an empirical expression obtained by integrating the sediment concentration along water depth.The concentration distributions and the mean diameter distributions of suspended sediment in the transversal direction are also estimated in this model. A four-point (Preismann type) finite difference scheme and TDMA are employed in the numerical method. Three typical floods occurd in 1977,1982 and 1996, respectively, in the Lower Yellow River from Tiexie to Shunkou with a length of 393.67km are numerically simulated with the model. The computed results, such as the water stage, discharge,and sediment concentration agree well with the measured data.

  18. A three-dimensional k-ε-kp model in curvilinear coordinates for sediment movement and bed evolution

    Institute of Scientific and Technical Information of China (English)

    SHEN YongMing; LIU Cheng

    2009-01-01

    To aim at the substitution of the magnitude and direction of water flow movement near bed for those of bed load transport in solid-liquid two-phase one-fluid model, and to simulate the effect of secondary flow on transverse bed load transport in channel bends and the effect of bed slope on bed load transport in a better way, a three-dimensional k-ε-kp solid-liquid two-phase two-fluid model in curvilinear coordinates is solved numerically with a finite-volume method on an adaptive grid for studying water-sediment movements and bed evolution in a 120° channel bend. Numerical results show that the trajectories of solid-phase deviate from those of liquid-phase in the channel bend, and the deviation increases with the increase of the particle diameters. The calculated bed deformation by the k-ε-kpmodel is in better agreement with measured bed deformation than those by one-fluid model. It is proved that the k-ε-kp model can simulate the effect of secondary flow on lateral bed load transport with the higher accuracy than the one-fluid model.

  19. A hybrid model of swash-zone longshore sediment transport on refelctive beaches

    NARCIS (Netherlands)

    Jiang, A.W.; Hughes, M.; Cowell, P.; Gordon, A.; Savioli, J.C.; Ranasinghe, R.W.M.R.J.B.

    2010-01-01

    The hydrodynamics and sediment transport in the swash zone is currently outside the domain of coastal-area models, which is a significant limitation in obtaining littoral sediment-transport estimates, especially on steep reflective beaches where the waves practically break on the beachface. In this

  20. Conceptual model of sedimentation in the Sacramento-San Joaquin River Delta

    Science.gov (United States)

    Schoellhamer, David H.; Wright, Scott A.; Drexler, Judith Z.

    2012-01-01

    Sedimentation in the Sacramento–San Joaquin River Delta builds the Delta landscape, creates benthic and pelagic habitat, and transports sediment-associated contaminants. Here we present a conceptual model of sedimentation that includes submodels for river supply from the watershed to the Delta, regional transport within the Delta and seaward exchange, and local sedimentation in open water and marsh habitats. The model demonstrates feedback loops that affect the Delta ecosystem. Submerged and emergent marsh vegetation act as ecosystem engineers that can create a positive feedback loop by decreasing suspended sediment, increasing water column light, which in turn enables more vegetation. Sea-level rise in open water is partially countered by a negative feedback loop that increases deposition if there is a net decrease in hydrodynamic energy. Manipulation of regional sediment transport is probably the most feasible method to control suspended sediment and thus turbidity. The conceptual model is used to identify information gaps that need to be filled to develop an accurate sediment transport model.

  1. 78 FR 13874 - Watershed Modeling To Assess the Sensitivity of Streamflow, Nutrient, and Sediment Loads to...

    Science.gov (United States)

    2013-03-01

    ... AGENCY Watershed Modeling To Assess the Sensitivity of Streamflow, Nutrient, and Sediment Loads to... Streamflow, Nutrient, and Sediment Loads to Climate Change and Urban Development in 20 U.S. Watersheds (EPA... and Development and is intended to characterize the sensitivity of streamflow, nutrient (nitrogen and...

  2. Distribution of longshore sediment transport along the Indian coast based on empirical model

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    An empirical sediment transport model has been developed based on longshore energy flux equation. Study indicates that annual gross sediment transport rate is high (1.5 x 10 super(6) cubic meters to 2.0 x 10 super(6) cubic meters) along the coasts...

  3. Modeling Benthic Sediment Processes to Predict Water Quality and Ecology in Narragansett Bay

    Science.gov (United States)

    The benthic sediment acts as a huge reservoir of particulate and dissolved material (within interstitial water) which can contribute to loading of contaminants and nutrients to the water column. A benthic sediment model is presented in this report to predict spatial and temporal ...

  4. Modelling spatial sediment delivery in an arid region using Thematic Mapper data and GIS

    NARCIS (Netherlands)

    Sharma, K.D.; Menenti, M.; Huygen, J.; Vich, A.

    1996-01-01

    A distributed-parameter sediment delivery model is linked with a personal computer-based, low-cost geographical information system to facilitate preparation, examination, and analysis of spatially distributed input parameters and to link the sediment delivery from a micro-scale to the watershed scal

  5. A hybrid model of swash-zone longshore sediment transport on refelctive beaches

    NARCIS (Netherlands)

    Jiang, A.W.; Hughes, M.; Cowell, P.; Gordon, A.; Savioli, J.C.; Ranasinghe, R.W.M.R.J.B.

    2010-01-01

    The hydrodynamics and sediment transport in the swash zone is currently outside the domain of coastal-area models, which is a significant limitation in obtaining littoral sediment-transport estimates, especially on steep reflective beaches where the waves practically break on the beachface. In this

  6. Cadmium transport in sediments by tubificid bioturbation: an assessment of model complexity

    NARCIS (Netherlands)

    Delmotte, S.; Meysman, F.J.R.; Ciutat, A.; Boudou, A.; Sauvage, S.; Gerino, M.

    2007-01-01

    Biogeochemistry of metals in aquatic sediments is strongly influenced by bioturbation. To determine the effects of biological transport on cadmium distribution in freshwater sediments, a bioturbation model is explored that describes the conveyor-belt feeding of tubificid oligochaetes. A stepwise

  7. 3D Modeling of sediment movement by ships-generated wakes in confined shipping channel

    Institute of Scientific and Technical Information of China (English)

    Shengcheng JI; Abdellatif OUAHSINE; Hassan SMAOUI; Philippe SERGENT

    2014-01-01

    Ship-generated waves and return currents are capable of re-suspending significant quantities of bottom and bank sediments. However, most of the previous studies done on the subject do not show how and where sediment is re-suspended by the wakes and the directions of net transport. In this paper, a 3D numerical model based on hydro-sedimentary coupling is presented to search the relationship between the sediment movement, and the pattern of ship-generated waves around and far away from the vessel and the return currents around the ships. The hydrodynamic model is based on 3D Navier-Stokes equations including the standard k-ε model for turbulence processes, and the sediment transport model is based on a 3D equation for the re-suspended sediment transport. The computation results show that the areas of sediment concentration and transport (whether by resuspension or by the bedload) depend mainly on the position, the speed of the ship in the waterways, the kinematics of ship-generated waves and on the return flows. Thus, a map of sediment distribution and the modes of sediment transport generated by the passage of the ship are presented.

  8. EVALUATION OF THE STATE-OF-THE-ART CONTAMINATED SEDIMENT TRANSPORT AND FATE MODELING SYSTEM

    Science.gov (United States)

    Modeling approaches for evaluating the transport and fate of sediment and associated contaminants are briefly reviewed. The main emphasis is on: 1) the application of EFDC (Environmental Fluid Dynamics Code), the state-of-the-art contaminated sediment transport and fate public do...

  9. Simulating Landscape Sediment Transport Capacity by Using a Modified SWAT Model.

    Science.gov (United States)

    Bonumá, Nadia B; Rossi, Colleen G; Arnold, Jeffrey G; Reichert, José M; Minella, Jean P; Allen, Peter M; Volk, Martin

    2014-01-01

    Sediment delivery from hillslopes to rivers is spatially variable and may lead to long-term delays between initial erosion and related sediment yield at the watershed outlet. Consideration of spatial variability is important for developing sound strategies for water quality improvement and soil protection at the watershed scale. Hence, the Soil and Water Assessment Tool (SWAT) was modified and tested in this study to simulate the landscape transport capacity of sediment. The study area was the steeply sloped Arroio Lino watershed in southern Brazil. Observed sediment yield data at the watershed outlet were used to calibrate and validate a modified SWAT model. For the calibration period, the modified model performed better than the unaltered SWAT2009 version; the models achieved Nash-Sutcliffe efficiency (NSE) values of 0.7 and -0.1, respectively. Nash-Sutcliffe efficiencies were less for the validation period, but the modified model's NSE was higher than the unaltered model (-1.4 and -12.1, respectively). Despite the relatively low NSE values, the results of this first test are promising because the model modifications lowered the percent bias in sediment yield from 73 to 18%. Simulation results for the modified model indicated that approximately 60% of the mobilized soil is deposited along the landscape before it reaches the river channels. This research demonstrates the modified model's ability to simulate sediment yield in watersheds with steep slopes. The results suggest that integration of the sediment deposition routine in SWAT increases accuracy in steeper areas while significantly improving its ability to predict the spatial distribution of sediment deposition areas. Further work is needed regarding (i) improved strategies for spatially distributed sediment transport measurements (for improving process knowledge and model evaluation) and (ii) extensive model tests in other well instrumented experimental watersheds with differing topographic configurations

  10. Solid waste integrated cost analysis model: 1991 project year report

    Energy Technology Data Exchange (ETDEWEB)

    1991-01-01

    The purpose of the City of Houston's 1991 Solid Waste Integrated Cost Analysis Model (SWICAM) project was to continue the development of a computerized cost analysis model. This model is to provide solid waste managers with tool to evaluate the dollar cost of real or hypothetical solid waste management choices. Those choices have become complicated by the implementation of Subtitle D of the Resources Conservation and Recovery Act (RCRA) and the EPA's Integrated Approach to managing municipal solid waste;. that is, minimize generation, maximize recycling, reduce volume (incinerate), and then bury (landfill) only the remainder. Implementation of an integrated solid waste management system involving all or some of the options of recycling, waste to energy, composting, and landfilling is extremely complicated. Factors such as hauling distances, markets, and prices for recyclable, costs and benefits of transfer stations, and material recovery facilities must all be considered. A jurisdiction must determine the cost impacts of implementing a number of various possibilities for managing, handling, processing, and disposing of waste. SWICAM employs a single Lotus 123 spreadsheet to enable a jurisdiction to predict or assess the costs of its waste management system. It allows the user to select his own process flow for waste material and to manipulate the model to include as few or as many options as he or she chooses. The model will calculate the estimated cost for those choices selected. The user can then change the model to include or exclude waste stream components, until the mix of choices suits the user. Graphs can be produced as a visual communication aid in presenting the results of the cost analysis. SWICAM also allows future cost projections to be made.

  11. High power solid state retrofit lamp thermal characterization and modeling

    NARCIS (Netherlands)

    Jakovenko, J.; Formánek, J.; Vladimír, J.; Husák, M.; Werkhoven, R.J.

    2012-01-01

    Thermal and thermo-mechanical modeling and characterization of solid state lightening (SSL) retrofit LED Lamp are presented in this paper. Paramount Importance is to design SSL lamps for reliability, in which thermal and thermo-mechanical aspects are key points. The main goal is to get a precise 3D

  12. Distributed model of hydrological and sediment transport processes in large river basins in Southeast Asia

    Science.gov (United States)

    Zuliziana, S.; Tanuma, K.; Yoshimura, C.; Saavedra, O. C.

    2015-07-01

    Soil erosion and sediment transport have been modeled at several spatial and temporal scales, yet few models have been reported for large river basins (e.g., drainage areas > 100 000 km2). In this study, we propose a process-based distributed model for assessment of sediment transport at a large basin scale. A distributed hydrological model was coupled with a process-based distributed sediment transport model describing soil erosion and sedimentary processes at hillslope units and channels. The model was tested on two large river basins: the Chao Phraya River Basin (drainage area: 160 000 km2) and the Mekong River Basin (795 000 km2). The simulation over 10 years showed good agreement with the observed suspended sediment load in both basins. The average Nash-Sutcliffe efficiency (NSE) and average correlation coefficient (r) between the simulated and observed suspended sediment loads were 0.62 and 0.61, respectively, in the Chao Phraya River Basin except the lowland section. In the Mekong River Basin, the overall average NSE and r were 0.60 and 0.78, respectively. Sensitivity analysis indicated that suspended sediment load is sensitive to detachability by raindrop (k) in the Chao Phraya River Basin and to soil detachability over land (Kf) in the Mekong River Basin. Overall, the results suggest that the present model can be used to understand and simulate erosion and sediment transport in large river basins.

  13. Distributed model of hydrological and sediment transport processes in large river basins in Southeast Asia

    Directory of Open Access Journals (Sweden)

    S. Zuliziana

    2015-07-01

    Full Text Available Soil erosion and sediment transport have been modeled at several spatial and temporal scales, yet few models have been reported for large river basins (e.g., drainage areas > 100 000 km2. In this study, we propose a process-based distributed model for assessment of sediment transport at a large basin scale. A distributed hydrological model was coupled with a process-based distributed sediment transport model describing soil erosion and sedimentary processes at hillslope units and channels. The model was tested on two large river basins: the Chao Phraya River Basin (drainage area: 160 000 km2 and the Mekong River Basin (795 000 km2. The simulation over 10 years showed good agreement with the observed suspended sediment load in both basins. The average Nash–Sutcliffe efficiency (NSE and average correlation coefficient (r between the simulated and observed suspended sediment loads were 0.62 and 0.61, respectively, in the Chao Phraya River Basin except the lowland section. In the Mekong River Basin, the overall average NSE and r were 0.60 and 0.78, respectively. Sensitivity analysis indicated that suspended sediment load is sensitive to detachability by raindrop (k in the Chao Phraya River Basin and to soil detachability over land (Kf in the Mekong River Basin. Overall, the results suggest that the present model can be used to understand and simulate erosion and sediment transport in large river basins.

  14. Modeling flow, sediment transport and morphodynamics in rivers

    Science.gov (United States)

    Nelson, Jonathan M.; McDonald, Richard R.; Shimizu, Yasuyuki; Kimura, Ichiro; Nabi, Mohamed; Asahi, Kazutake

    2016-01-01

    Predicting the response of natural or man-made channels to imposed supplies of water and sediment is one of the difficult practical problems commonly addressed by fluvial geomorphologists. This problem typically arises in three situations. In the first situation, geomorphologists are attempting to understand why a channel or class of channels has a certain general form; in a sense, this is the central goal of fluvial geomorphology. In the second situation, geomorphologists are trying to understand and explain how and why a specific channel will evolve or has evolved in response to altered or unusual sediment and water supplies to that channel. For example, this would include explaining the short-term response of a channel to an unusually large flood or predicting the response of a channel to long-term changes in flow or sediment supply due to various human activities such as damming or diversions. Finally, geomorphologists may be called upon to design or assess the design of proposed man-made channels that must carry a certain range of flows and sediment loads in a stable or at least quasi-stable manner. In each of these three situations, the problem is really the same: geomorphologists must understand and predict the interaction of the flow field in the channel, the sediment movement in the channel and the geometry of the channel bed and banks. In general, the flow field, the movement of sediment making up the bed and the morphology of the bed are intricately linked; the flow moves the sediment, the bed is altered by erosion and deposition of sediment and the shape of the bed is critically important for predicting the flow. This complex linkage is precisely what makes understanding channel form and process such a difficult and interesting challenge.

  15. Marine sediments monitoring studies for trace elements with the application of fast temperature programs and solid sampling high resolution continuum source atomic absorption spectrometry

    Science.gov (United States)

    Orani, Anna Maria; Han, Eunmi; Mandjukov, Petko; Vassileva, Emilia

    2015-01-01

    Analytical procedure for the determination of As, Cd, Cu, Ni, Co and Cr in marine sediment samples using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR CS AAS) and direct solid sample analysis has been developed. The application of fast programs in combination with direct solid sampling allows to eliminate the drying and pretreatment steps, however makes impossible the use of liquid standards for calibration. Iridium treated platforms were applied throughout the present study. Calibration technique based on the use of solid certified reference materials (marine sediments) similar to the nature of the analyzed sample and statistics of regression analysis were applied to the real sediment samples. The instrumental parameters were optimized in order to obtain reproducible and interference free analytical signals. The ISO-17025 requirements and Eurachem guidelines were followed in the validation of the proposed analytical procedure. Accordingly, blanks, selectivity, calibration, linearity, working range, trueness, repeatability reproducibility, limits of detection and quantification and expanded uncertainty (k = 2) for all investigated elements were assessed. Two different approaches for the estimation of measurement uncertainty were applied and obtained results compared. The major contributors to the combined uncertainty of the analyte mass fraction were found to be the homogeneity of the samples and the microbalance precision. The influence of sample particle sizes on the total combined uncertainty was also evaluated. Traceability to SI system of units of the obtained by the proposed analytical procedure results was demonstrated. Additionally, validation of the methodology developed was effectuated by the comparison of the obtained results with independent method e.g. ICP-MS with external calibration. The use of solid sampling HR CS AAS for the determination of trace elements in marine sediment matrix gives significant advantages

  16. Measuring and modeling suspended sediment concentration profiles in the surf zone

    Directory of Open Access Journals (Sweden)

    Ping Wang

    2012-10-01

    Full Text Available Time-averaged suspended sediment concentration profiles across the surf zone were measured in a large-scale three-dimensional movable bed laboratory facility (LSTF: Large-scale Sediment Transport Facility. Sediment suspension under two different types of breaking waves, spilling and plunging breakers, was investigated. The magnitudes and shapes of the concentration profiles varied substantially at different locations across the surf zone, reflecting the different intensities of breaking-induced turbulence. Sediment suspension at the energetic plunging breaker-line was much more active, resulting in nearly homogeneous concentration profiles throughout most of the water column, as compared to the reminder of the surf zone and at the spilling breaker-line. Four suspended sediment concentration models were examined based on the LSTF data, including the mixing turbulence length approach, segment eddy viscosity model, breaking-induced wave-energy dissipation approach, and a combined breaking and turbulence length model developed by this study. Neglecting the breaking-induced turbulence and subsequent sediment mixing, suspended sediment concentration models failed to predict the across-shore variations of the sediment suspension, especially at the plunging breaker-line. Wave-energy dissipation rate provided an accurate method for estimating the intensity of turbulence generated by wave breaking. By incorporating the breaking-induced turbulence, the combined breaking and turbulence length model reproduced the across-shore variation of sediment suspension in the surf zone. The combined model reproduced the measured time-averaged suspended sediment concentration profiles reasonably well across the surf zone.

  17. A participatory modelling approach to developing a numerical sediment dynamics model

    Science.gov (United States)

    Jones, Nicholas; McEwen, Lindsey; Parker, Chris; Staddon, Chad

    2016-04-01

    Fluvial geomorphology is recognised as an important consideration in policy and legislation in the management of river catchments. Despite this recognition, limited knowledge exchange occurs between scientific researchers and river management practitioners. An example of this can be found within the limited uptake of numerical models of sediment dynamics by river management practitioners in the United Kingdom. The uptake of these models amongst the applied community is important as they have the potential to articulate how, at the catchment-scale, the impacts of management strategies of land-use change affect sediment dynamics and resulting channel quality. This paper describes and evaluates a new approach which involves river management stakeholders in an iterative and reflexive participatory modelling process. The aim of this approach was to create an environment for knowledge exchange between the stakeholders and the research team in the process of co-constructing a model. This process adopted a multiple case study approach, involving four groups of river catchment stakeholders in the United Kingdom. These stakeholder groups were involved in several stages of the participatory modelling process including: requirements analysis, model design, model development, and model evaluation. Stakeholders have provided input into a number of aspects of the modelling process, such as: data requirements, user interface, modelled processes, model assumptions, model applications, and model outputs. This paper will reflect on this process, in particular: the innovative methods used, data generated, and lessons learnt.

  18. Predicting watershed sediment yields after wildland fire with the InVEST sediment retention model at large geographic extent in the western USA: accuracy and uncertainties

    Science.gov (United States)

    Sankey, J. B.; Kreitler, J.; McVay, J.; Hawbaker, T. J.; Vaillant, N.; Lowe, S. E.

    2014-12-01

    Wildland fire is a primary threat to watersheds that can impact water supply through increased sedimentation, water quality decline, and change the timing and amount of runoff leading to increased risk from flood and sediment natural hazards. It is of great societal importance in the western USA and throughout the world to improve understanding of how changing fire frequency, extent, and location, in conjunction with fuel treatments will affect watersheds and the ecosystem services they supply to communities. In this work we assess the utility of the InVEST Sediment Retention Model to accurately characterize vulnerability of burned watersheds to erosion and sedimentation. The InVEST tools are GIS-based implementations of common process models, engineered for high-end computing to allow the faster simulation of larger landscapes and incorporation into decision-making. The InVEST Sediment Retention Model is based on common soil erosion models (e.g., RUSLE -Revised Universal Soil Loss Equation) and determines which areas of the landscape contribute the greatest sediment loads to a hydrological network and conversely evaluate the ecosystem service of sediment retention on a watershed basis. We evaluate the accuracy and uncertainties for InVEST predictions of increased sedimentation after fire, using measured post-fire sedimentation rates available for many watersheds in different rainfall regimes throughout the western USA from an existing, large USGS database of post-fire sediment yield [synthesized in Moody J, Martin D (2009) Synthesis of sediment yields after wildland fire in different rainfall regimes in the western United States. International Journal of Wildland Fire 18: 96-115]. The ultimate goal of this work is to calibrate and implement the model to accurately predict variability in post-fire sediment yield as a function of future landscape heterogeneity predicted by wildfire simulations, and future landscape fuel treatment scenarios, within watersheds.

  19. Applicability of solid-phase microextraction combined with gas chromatography atomic emission detection (GC-MIP AED) for the determination of butyltin compounds in sediment samples

    Energy Technology Data Exchange (ETDEWEB)

    Carpinteiro, J.; Rodriguez, I.; Cela, R. [Universidad de Santiago de Compostela, Departamento de Quimica Analitica, Nutricion y Bromatologia, Instituto de Investigacion y Analisis Alimentario, Santiago de Compostela 15782 (Spain)

    2004-11-01

    The performance of solid-phase microextraction (SPME) applied to the determination of butyltin compounds in sediment samples is systematically evaluated. Matrix effects and influence of blank signals on the detection limits of the method are studied in detail. The interval of linear response is also evaluated in order to assess the applicability of the method to sediments polluted with butyltin compounds over a large range of concentrations. Advantages and drawbacks of including an SPME step, instead of the classic liquid-liquid extraction of the derivatized analytes, in the determination of butyltin compounds in sediment samples are considered in terms of achieved detection limits and experimental effort. Analytes were extracted from the samples by sonication using glacial acetic acid. An aliquot of the centrifuged extract was placed on a vial where compounds were ethylated and concentrated on a PDMS fiber using the headspace mode. Determinations were carried out using GC-MIP AED. (orig.)

  20. Uncertainty in complex three-dimensional sediment transport models: equifinality in a model application of the Ems Estuary, the Netherlands

    Science.gov (United States)

    van Maren, Dirk Sebastiaan; Cronin, Katherine

    2016-12-01

    Estuarine suspended sediment transport models are typically calibrated against suspended sediment concentration data. These data typically cover a limited range of the actual suspended sediment concentration dynamics, constrained in either time or space. As a result of these data limitations, the available data can be reproduced with complex 3D transport models through multiple sets of model calibration parameters. These various model parameter sets influence the relative importance of transport processes such as settling, deposition, erosion, or mixing. As a result, multiple model parameter sets may reproduce sediment dynamics in tidal channels (where most data is typically collected) with the same degree of accuracy but simulate notably different sediment concentration patterns elsewhere (e.g. on the tidal flats). Different combinations of model input parameters leading to the same result are known as equifinality. The effect of equifinality on predictive model capabilities is investigated with a complex three-dimensional sediment transport model of a turbid estuary which is subject to several human interventions. The effect of two human interventions (offshore disposal of dredged sediment and restoration of the tidal channel profile) was numerically examined with several equifinal model settings. The computed effect of these two human interventions was relatively weakly influenced by the model settings, strengthening confidence in the numerical model predictions.

  1. Including Flocculation in a Numerical Sediment Transport Model for a Partially-Mixed Estuary

    Science.gov (United States)

    Tarpley, D.; Harris, C. K.; Friedrichs, C. T.

    2016-12-01

    Particle settling velocity impacts the transport of suspended sediment to the first order but fine-grained material like muds tend to form loosely bound aggregates (flocs) whose settling velocity can vary widely. Properties of flocculated sediment such as settling velocity and particle density are difficult to predict because they change in response to several factors including salinity, suspended sediment concentration, turbulent mixing, and organic content. Knowledge of the mechanisms governing flocculation of cohesive sediment is rapidly expanding; especially in response to recent technical advances. As the understanding of particle dynamics progresses, numerical models describing flocculation and break-up are being developed with varying degrees of complexity. While complex models capture the dynamics of the system, their computational costs may prohibit their incorporation into larger model domains. It is important to determine if the computational costs of intricate floc models are justifiable compared to simpler formulations. For this study, we implement an idealized two-dimensional model designed to represent a longitudinal section of a partially mixed estuary that neglects across-channel variation but exhibits salinity driven estuarine circulation. The idealized domain is designed to mimic the primary features of the York River, VA. Suspended load, erosion and deposition are calculated within the sediment transport routines of the COAWST modeling system. We compare different methods for prescribing settling velocity of fine-grained material. The simplest, standard model neglects flocculation dynamics while the complex treatment is a size-class-based flocculation model (FLOCMOD). Differences in tidal and daily averages of suspended load, bulk settling velocity and bed deposition are compared between the standard and FLOCMOD runs, to examine the relative impact of flocculation on sediment transport patterns. We expect FLOCMOD to have greater variability and

  2. An approach for modeling sediment budgets in supply-limited rivers

    Science.gov (United States)

    Wright, Scott A.; Topping, David J.; Rubin, David M.; Melis, Theodore S.

    2010-01-01

    Reliable predictions of sediment transport and river morphology in response to variations in natural and human-induced drivers are necessary for river engineering and management. Because engineering and management applications may span a wide range of space and time scales, a broad spectrum of modeling approaches has been developed, ranging from suspended-sediment "rating curves" to complex three-dimensional morphodynamic models. Suspended sediment rating curves are an attractive approach for evaluating changes in multi-year sediment budgets resulting from changes in flow regimes because they are simple to implement, computationally efficient, and the empirical parameters can be estimated from quantities that are commonly measured in the field (i.e., suspended sediment concentration and water discharge). However, the standard rating curve approach assumes a unique suspended sediment concentration for a given water discharge. This assumption is not valid in rivers where sediment supply varies enough to cause changes in particle size or changes in areal coverage of sediment on the bed; both of these changes cause variations in suspended sediment concentration for a given water discharge. More complex numerical models of hydraulics and morphodynamics have been developed to address such physical changes of the bed. This additional complexity comes at a cost in terms of computations as well as the type and amount of data required for model setup, calibration, and testing. Moreover, application of the resulting sediment-transport models may require observations of bed-sediment boundary conditions that require extensive (and expensive) observations or, alternatively, require the use of an additional model (subject to its own errors) merely to predict the bed-sediment boundary conditions for use by the transport model. In this paper we present a hybrid approach that combines aspects of the rating curve method and the more complex morphodynamic models. Our primary objective

  3. An approach for modeling sediment budgets in supply-limited rivers

    Science.gov (United States)

    Wright, Scott A.; Topping, David J.; Rubin, David M.; Melis, Theodore S.

    2010-10-01

    Reliable predictions of sediment transport and river morphology in response to variations in natural and human-induced drivers are necessary for river engineering and management. Because engineering and management applications may span a wide range of space and time scales, a broad spectrum of modeling approaches has been developed, ranging from suspended-sediment "rating curves" to complex three-dimensional morphodynamic models. Suspended sediment rating curves are an attractive approach for evaluating changes in multi-year sediment budgets resulting from changes in flow regimes because they are simple to implement, computationally efficient, and the empirical parameters can be estimated from quantities that are commonly measured in the field (i.e., suspended sediment concentration and water discharge). However, the standard rating curve approach assumes a unique suspended sediment concentration for a given water discharge. This assumption is not valid in rivers where sediment supply varies enough to cause changes in particle size or changes in areal coverage of sediment on the bed; both of these changes cause variations in suspended sediment concentration for a given water discharge. More complex numerical models of hydraulics and morphodynamics have been developed to address such physical changes of the bed. This additional complexity comes at a cost in terms of computations as well as the type and amount of data required for model setup, calibration, and testing. Moreover, application of the resulting sediment-transport models may require observations of bed-sediment boundary conditions that require extensive (and expensive) observations or, alternatively, require the use of an additional model (subject to its own errors) merely to predict the bed-sediment boundary conditions for use by the transport model. In this paper we present a hybrid approach that combines aspects of the rating curve method and the more complex morphodynamic models. Our primary objective

  4. An integration scheme for stiff solid-gas reactor models

    Directory of Open Access Journals (Sweden)

    Bjarne A. Foss

    2001-04-01

    Full Text Available Many dynamic models encounter numerical integration problems because of a large span in the dynamic modes. In this paper we develop a numerical integration scheme for systems that include a gas phase, and solid and liquid phases, such as a gas-solid reactor. The method is based on neglecting fast dynamic modes and exploiting the structure of the algebraic equations. The integration method is suitable for a large class of industrially relevant systems. The methodology has proven remarkably efficient. It has in practice performed excellent and been a key factor for the success of the industrial simulator for electrochemical furnaces for ferro-alloy production.

  5. Modeling steel deformation in the semi-solid state

    CERN Document Server

    Hojny, Marcin

    2017-01-01

    This book addresses selected aspects of steel-deformation modelling, both at very high temperatures and under the conditions in which the liquid and the solid phases coexist. Steel-deformation modelling with its simultaneous solidification is particularly difficult due to its specificity and complexity. With regard to industrial applications and the development of new, integrated continuous casting and rolling processes, the issues related to modelling are becoming increasingly important. Since the numerous industrial tests that are necessary when traditional methods are used to design the process of continuous casting immediately followed by rolling are expensive, new modelling concepts have been sought. Comprehensive tests were applied to solve problems related to the deformation of steel with a semi-solid core. Physical tests using specialist laboratory instruments (Gleeble 3800thermo-mechanical simulator, NANOTOM 180 N computer tomography, Zwick Z250 testing equipment, 3D blue-light scanning systems), and...

  6. Modeling of ionic transport in solid polymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Cheang, P L; Teo, L L; Lim, T L, E-mail: plcheang@mmu.edu.my [Centre for Foundation Studies and Extension Education, Multimedia University, Jln Ayer Keroh Lama, 75450 Melaka (Malaysia)

    2010-05-15

    A Monte Carlo model describing the ionic trans port in solid polyme relectrolyte is developed. Single cation simulation is carried out using hopping rate to study the transport mechanism of a thermally activated ion in solid polymer electrolyte. In our model, the ion is able to hop along a polymer chain and to jump between different chains, surmounting energy barriers that consist of polymer's activation energy and the externally applied electric field. The model is able to trace the motion of ion across polymer electrolyte. The mean hopping distance is calculated based on the available open bond in the next nearest side. Random numbers are used to determine the hopping distances, free flight times, final energy and direction of the cation after successful hop. Drift velocity and energy of cation are simulated in our work. The model is expected to be able to simulate the lithium-polymer battery in future.

  7. Sediment transport modelling in a distributed physically based hydrological catchment model

    Directory of Open Access Journals (Sweden)

    M. Konz

    2011-09-01

    Full Text Available Bedload sediment transport and erosion processes in channels are important components of water induced natural hazards in alpine environments. A raster based distributed hydrological model, TOPKAPI, has been further developed to support continuous simulations of river bed erosion and deposition processes. The hydrological model simulates all relevant components of the water cycle and non-linear reservoir methods are applied for water fluxes in the soil, on the ground surface and in the channel. The sediment transport simulations are performed on a sub-grid level, which allows for a better discretization of the channel geometry, whereas water fluxes are calculated on the grid level in order to be CPU efficient. Several transport equations as well as the effects of an armour layer on the transport threshold discharge are considered. Flow resistance due to macro roughness is also considered. The advantage of this approach is the integrated simulation of the entire basin runoff response combined with hillslope-channel coupled erosion and transport simulation. The comparison with the modelling tool SETRAC demonstrates the reliability of the modelling concept. The devised technique is very fast and of comparable accuracy to the more specialised sediment transport model SETRAC.

  8. VERIFICATION OF MATHEMATICL MODEL FOR SEDIMENT TRANSPORT BY UNSTEADY FLOW IN THE LOWER YELLOW RIVER

    Institute of Scientific and Technical Information of China (English)

    Jianjun ZHOU; Bingnan LIN

    2004-01-01

    Field data from the Lower Yellow River (LYR) covering a period of ten consecutive years are used to test a mathematical model for one dimensional sediment transport by unsteady flow developed previously by the writers. Data of the first year of the said period, i.e., 1976, are used to calibrate the model and those of the remaining years to verify it. Items investigated include discharge, water stage, rate of transport of suspended sediment and riverbed erosion/deposition. Comparisons between computed and observed data indicate that the proposed model may well simulate sediment transport in the LYR under conditions of unsteady flow with sufficient accuracy.

  9. Modeling the sediment transport induced by deep sea mining in the Pacific Ocean

    Science.gov (United States)

    Purkiani, Kaveh; Paul, André; Schulz, Michael; Vink, Annemiek; Walter, Maren

    2017-04-01

    A numerical modeling study is conducted in the German license area in northeastern Pacific Ocean to investigate the sediment dispersal of mining exploitation. A sediment transport module is implemented in a hydrodynamic model. All differently sized particles can aggregate and break up until equilibrium floc sizes are obtained. A nested model approach using the MITgcm (Massachusetts Institute of Technology general circulation model) is applied and validated against hydrographic and hydrodynamic measurements obtained in this region. Two different sediment discharge scenarios have been examined to investigate the effect of flocculation on sediment transport distribution in the deep ocean. The suspended sediment is mainly influenced by a dominant SW current far away from the sediment discharge location. Independent of initial particle size all initial particles larger than 30 μm attain similar floc size equilibrium. In contrast to coastal seas and estuaries where floc size equilibrium can be obtained in a few hours, due to low shear rate (G) the flocculation process at deep ocean is completed within 1˜2 days. Considering temporal evolution of the floc size in the model, an increase in floc sinking velocity consequently enhances the sediment deposition at seafloor. The analysis of different sediment concentration scenarios suggests that floc sinking velocity increases at higher suspended sediment concentration (SSC). The presence of a dominant current in this region induces a fine sediment plume in SW direction. The dispersed SSC plume at 20 km downstream the discharge location is able to form the flocculation process and induces a spatial variation of floc size and floc sinking velocity.

  10. Experimental and modelling study on the uptake and desorption kinetics of 133Ba by suspended estuarine sediments from southern Spain.

    Science.gov (United States)

    Barros, H; Abril, J M

    2004-02-01

    Dispersion of pollutants in aquatic environments depends on their uptake by suspended solids. This work deals with the uptake kinetics of 133Ba (gamma-emitter and a good analogue of 226Ra) by suspended estuarine sediments (which can be resuspended into the water column under certain conditions). This study presents a wide set of tracing experiments, including second tracing, decantation and desorption processes. The purpose is to characterize 133Ba uptake by sediments and to investigate the use and limitations of box models in order to describe the uptake kinetics. Water and sediment samples were collected in the Huelva estuary (Spain), where environmental 226Ra concentrations have been increased by two phosphate fertilizer industries. Samples were characterized by granulometric, organic carbon content, cation exchange capacity and XRF-EP analyses. Results revealed three-step kinetics, with characteristic times of minutes, hours and days. These results enabled the selection and calibration of a suitable box model and facilitated the testing of its use as a fully predictive tool.

  11. Modeling effective viscosity reduction behaviour of solid suspensions

    Institute of Scientific and Technical Information of China (English)

    Wei En-Bo; Ji Yan-Ju; Zhang Jun

    2012-01-01

    Under a simple shearing flow,the effective viscosity of solid suspensions can be reduced by controlling the inclusion particle size or the number of inclusion particles in a unit volume.Based on the Stokes equation,the transformation field method is used to model the reduction behaviour of effective viscosity of solid suspensions theoretically by enlarging the particle size at a given high concentration of particles.With a lot of samples of random cubic particles in a unit cell,our statistical results show that at the same higher concentration,the effective viscosity of solid suspensions can be reduced by increasing the particle size or reducing the number of inclusion particles in a unit volume.This work discloses the viscosity reduction mechanism of increasing particle size,which is observed experimentally.

  12. Using disposable solid-phase microextraction (SPME) to determine the freely dissolved concentration of polybrominated diphenyl ethers (PBDEs) in sediments.

    Science.gov (United States)

    Jia, Fang; Cui, Xinyi; Wang, Wei; Delgado-Moreno, Laura; Gan, Jay

    2012-08-01

    Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants (BFRs). The ubiquity and persistence of PBDEs in sediment have raised concerns over their environmental fate and ecological risks. Due to strong affinity for sediment organic matter, environmental fate and bioavailability of PBDEs closely depend on their phase distribution. In this study, disposable polydimethylsiloxane (PDMS) fiber was used to derive the freely dissolved concentration (C(free)) of PBDEs in sediment porewater as a measurement of bioavailability. The PDMS-to-water partition coefficient (log K(PDMS)) was 5.46-5.83 for BDE 47, 99, and 153. In sediments, PBDEs were predominantly sorbed to the sediment phase, with C(free) accounting for PBDEs decreased as their bromination or sediment organic carbon content increased. The strong association with dissolved organic matter (DOM) implies a potential for facilitated offsite transport and dispersion in the environment that depends closely on the stability of sediment aggregates.

  13. Channel responses to varying sediment input: A flume experiment modeled after Redwood Creek, California

    Science.gov (United States)

    Madej, M.A.; Sutherland, D.G.; Lisle, T.E.; Pryor, B.

    2009-01-01

    At the reach scale, a channel adjusts to sediment supply and flow through mutual interactions among channel form, bed particle size, and flow dynamics that govern river bed mobility. Sediment can impair the beneficial uses of a river, but the timescales for studying recovery following high sediment loading in the field setting make flume experiments appealing. We use a flume experiment, coupled with field measurements in a gravel-bed river, to explore sediment transport, storage, and mobility relations under various sediment supply conditions. Our flume experiment modeled adjustments of channel morphology, slope, and armoring in a gravel-bed channel. Under moderate sediment increases, channel bed elevation increased and sediment output increased, but channel planform remained similar to pre-feed conditions. During the following degradational cycle, most of the excess sediment was evacuated from the flume and the bed became armored. Under high sediment feed, channel bed elevation increased, the bed became smoother, mid-channel bars and bedload sheets formed, and water surface slope increased. Concurrently, output increased and became more poorly sorted. During the last degradational cycle, the channel became armored and channel incision ceased before all excess sediment was removed. Selective transport of finer material was evident throughout the aggradational cycles and became more pronounced during degradational cycles as the bed became armored. Our flume results of changes in bed elevation, sediment storage, channel morphology, and bed texture parallel those from field surveys of Redwood Creek, northern California, which has exhibited channel bed degradation for 30??years following a large aggradation event in the 1970s. The flume experiment suggested that channel recovery in terms of reestablishing a specific morphology may not occur, but the channel may return to a state of balancing sediment supply and transport capacity.

  14. Metal availability in a highly contaminated, dredged-sediment disposal site: Field measurements and geochemical modeling

    Energy Technology Data Exchange (ETDEWEB)

    Lions, Julie, E-mail: j.lions@brgm.f [BRGM, 3 Avenue Claude Guillemin, 45060 Orleans Cedex 2 (France); Centre National de Recherche sur les Sites et Sols Pollues, BP 537, 59505 Douai cedex (France); Guerin, Valerie; Bataillard, Philippe [BRGM, 3 Avenue Claude Guillemin, 45060 Orleans Cedex 2 (France); Centre National de Recherche sur les Sites et Sols Pollues, BP 537, 59505 Douai cedex (France); Lee, Jan van der [Mines ParisTech, Centre de Geosciences, 77305 Fontainebleau Cedex (France); Laboudigue, Agnes [Univ Lille Nord de France, F-59000 Lille (France); EMDouai, MPE-GCE, F-59500 Douai (France); Centre National de Recherche sur les Sites et Sols Pollues, BP 537, 59505 Douai cedex (France)

    2010-09-15

    Two complementary approaches were used to characterize arsenic and metal mobilizations from a dredged-sediment disposal site: a detailed field study combined with hydrogeochemical modeling. Contaminants in sediments were found to be mainly present as sulfides subject to oxidation. Secondary phases (carbonates, sulfates, (hydr)oxides) were also observed. Oxidative processes occurred at different rates depending on physicochemical conditions and contaminant contents in the sediment. Two distinct areas were identified on the site, each corresponding to a specific contaminant mobility behavior. In a reducing area, Fe and As were highly soluble and illustrated anoxic behavior. In well-oxygenated material, groundwater was highly contaminated in Zn, Cd and Pb. A third zone in which sediments and groundwater were less contaminated was also characterized. This study enabled us to prioritize remediation work, which should aim to limit infiltration and long-term environmental impact. - A detailed case study of metal behavior in a dredged-sediment disposal site combined with geochemical modeling.

  15. Adsoption Model of Mercury in the Water-Sediment Systems in Riam Kanan Dam, South Kalimantan

    Directory of Open Access Journals (Sweden)

    Utami Irawati

    2014-06-01

    Full Text Available The Riam Kanan  Dam reservoir is one of living source for the people of South Kalimantan and has a strategic value for their prosperity. Traditional and illegal mining activities nearby the area of this dam may cause heavy metals pollution, such as mercury (Hg in the water and sediment. This research was conducted to predict  the adsorption model of mercury (Hg in water and sediment system in Riam Kanan reservoir  Banjar regency.  The modeling was carried out by analyzing the content of mercury (Hg in the water  and sediments. The result was then plotted into Freundlich and Langmuir models. The determination coefficient for each of the models were 0.947 and 0.388 respectively. It can be concluded that the transport of mercury (Hg from water bodies  onto the sediment complies with Freundlich model.

  16. A 2-D process-based model for suspended sediment dynamics: a first step towards ecological modeling

    Directory of Open Access Journals (Sweden)

    F. M. Achete

    2015-02-01

    Full Text Available In estuaries most of the sediment load is carried in suspension. Sediment dynamics differ depending on sediment supply and hydrodynamic forcing conditions that vary over space and over time. Suspended sediment concentration (SSC is one of the most important contributors to turbidity, which influences habitat conditions and ecological functions of the system. A robust sediment model is the first step towards a chain of model including contaminants and phytoplankton dynamics and habitat modeling. This works aims to determine turbidity levels in the complex-geometry Delta of San Francisco Estuary using a process-based approach (D-Flow Flexible Mesh software. Our approach includes a detailed calibration against measured SSC levels, a sensitivity analysis on model parameters, the determination of a yearly sediment budget as well as an assessment of model results in terms of turbidity levels for a single year (Water Year 2011. Model results shows that our process-based approach is a valuable tool in assessing sediment dynamics and their related ecological parameters over a range of spatial and temporal scales. The current model may act as the base model for a chain of ecological models and climate scenario forecasting.

  17. Modeling the Voltage Dependence of Electrochemical Reactions at Solid-Solid and Solid-Liquid Interfaces in Batteries

    Science.gov (United States)

    Leung, Kevin

    2015-03-01

    Electrochemical reactions at electrode/electrolyte interfaces are critically dependent on the total electrochemical potential or voltage. In this presentation, we briefly review ab initio molecular dynamics (AIMD)-based estimate of voltages on graphite basal and edge planes, and then apply similar concepts to solid-solid interfaces relevant to lithium ion and Li-air batteries. Thin solid films on electrode surfaces, whether naturally occuring during power cycling (e.g., undesirable lithium carbonate on Li-air cathodes) or are artificially introduced, can undergo electrochemical reactions as the applied voltage varies. Here the onset of oxidation of lithium carbonate and other oxide thin films on model gold electrode surfaces is correlated with the electronic structure in the presence/absence of solvent molecules. Our predictions help determine whether oxidation first occurs at the electrode-thin film or electrolyte-thin film interface. Finally, we will critically compare the voltage estimate methodology used in the fuel cell community with the lithium cohesive energy calibration method broadly applied in the battery community, and discuss why they may yield different predictions. This work was supported by Nanostructures for Electrical Energy Storage (NEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0001160. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Deparment of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  18. SRM (Solid Rocket Motor) propellant and polymer materials structural modeling

    Science.gov (United States)

    Moore, Carleton J.

    1988-01-01

    The following investigation reviews and evaluates the use of stress relaxation test data for the structural analysis of Solid Rocket Motor (SRM) propellants and other polymer materials used for liners, insulators, inhibitors, and seals. The stress relaxation data is examined and a new mathematical structural model is proposed. This model has potentially wide application to structural analysis of polymer materials and other materials generally characterized as being made of viscoelastic materials. A dynamic modulus is derived from the new model for stress relaxation modulus and is compared to the old viscoelastic model and experimental data.

  19. Modeling the diffusion of solid copper into liquid solder alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rizvi, M.J. [School of Computing and Mathematical Sciences, University of Greenwich, 30 Park Row, London, SE10 9LS (United Kingdom)], E-mail: rm77@gre.ac.uk; Lu, H.; Bailey, C. [School of Computing and Mathematical Sciences, University of Greenwich, 30 Park Row, London, SE10 9LS (United Kingdom)

    2009-01-01

    During the soldering process, the copper atoms diffuse into liquid solders. The diffusion process determines integrity and the reworking possibility of a solder joint. In order to capture the diffusion scenarios of solid copper into liquid Sn-Pb and Sn-Cu solders, a computer modeling has been performed for 10 s. An analytical model has also been proposed for calculating the diffusion coefficient of copper into liquid solders. It is found that the diffusion coefficient for Sn-Pb solder is 2.74 x 10{sup -10} m{sup 2}/s and for Sn-Cu solder is 6.44 x 10{sup -9} m{sup 2}/s. The modeling results reveal that the diffusion coefficient is one of the major factors that govern the rate at which solid Cu dissolve in the molten solder. The predicted dissolved amounts of copper into solders have been validated with the help of scanning electron microscopic analysis.

  20. Modeling sediment accumulation in North American playa wetlands in response to climate change, 1940-2100

    Science.gov (United States)

    Burris, Lucy; Skagen, Susan K.

    2013-01-01

    Playa wetlands on the west-central Great Plains of North America are vulnerable to sediment infilling from upland agriculture, putting at risk several important ecosystem services as well as essential habitats and food resources of diverse wetland-dependent biota. Climate predictions for this semi-arid area indicate reduced precipitation which may alter rates of erosion, runoff, and sedimentation of playas. We forecasted erosion rates, sediment depths, and resultant playa wetland depths across the west-central Great Plains and examined the relative roles of land use context and projected changes in precipitation in the sedimentation process. We estimated erosion with the Revised Universal Soil Loss Equation (RUSLE) using historic values and downscaled precipitation predictions from three general circulation models and three emissions scenarios. We calibrated RUSLE results using field sediment measurements. RUSLE is appealing for regional scale modeling because it uses climate forecasts with monthly resolution and other widely available values including soil texture, slope and land use. Sediment accumulation rates will continue near historic levels through 2070 and will be sufficient to cause most playas (if not already filled) to fill with sediment within the next 100 years in the absence of mitigation. Land use surrounding the playa, whether grassland or tilled cropland, is more influential in sediment accumulation than climate-driven precipitation change.

  1. Modelling of cohesive sediment dynamics in tidal estuarine systems: Case study of Tagus estuary, Portugal

    Science.gov (United States)

    Franz, G.; Pinto, L.; Ascione, I.; Mateus, M.; Fernandes, R.; Leitão, P.; Neves, R.

    2014-12-01

    Cohesive sediment dynamics in estuarine systems is a major issue in water quality and engineering problems. Numerical models can help to assess the complex dynamics of cohesive sediments, integrating the information collected in monitoring studies. Following a numerical approach we investigated the main factors that influence the cohesive sediment dynamics in an estuarine system composed of large mudflats (Tagus estuary, Portugal). After a spin up period of the bottom layer and considering the combined effect of waves and currents on the bottom shear stress, the dynamics of cohesive sediment during the fortnightly and daily erosion-sedimentation cycle was properly reproduced by the model. The results of cohesive suspended sediments were validated with data from sixteen monitoring stations located along the estuary and turbidity data measured by two multiparametric probes. The hydrodynamics were previously validated by harmonic analysis and with ADCP data. Although tidal currents are the major cause of cohesive sediment erosion, the results suggest that wind waves also play an important role. The simulated sediment mass involved in the fortnightly tidal cycle was in the same order of magnitude of the annual load from the rivers, as observed in previous studies based on field data.

  2. Modeling sediment transport after ditch network maintenance of a forested peatland

    Science.gov (United States)

    Haahti, K.; Marttila, H.; Warsta, L.; Kokkonen, T.; Finér, L.; Koivusalo, H.

    2016-11-01

    Elevated suspended sediment (SS) loads released from peatlands after drainage operations and the resulting negative effect on the ecological status of the receiving water bodies have been widely recognized. Understanding the processes controlling erosion and sediment transport within the ditch network forms a prerequisite for adequate sediment control. While numerous experimental studies have been reported in this field, model based assessments are rare. This study presents a modeling approach to investigate sediment transport in a peatland ditch network. The transport model describes bed erosion, rain-induced bank erosion, floc deposition, and consolidation of the bed. Coupled to a distributed hydrological model, sediment transport was simulated in a 5.2 ha forestry-drained peatland catchment for 2 years after ditch cleaning. Comparing simulation results to measured SS concentrations suggested that the loose peat material, produced during excavation, contributed markedly to elevated SS concentrations immediately after ditch cleaning. Both snowmelt and summer rainstorms contributed critically to annual loads. Springtime peat erosion during snowmelt was driven by ditch flow whereas during summer rainfalls, bank erosion by raindrop impact was identified as an important process. Relating modeling results to observed spatial topographic changes in the ditch network was challenging and the results were difficult to verify. Nevertheless, the model has potential to identify risk areas for erosion. The results demonstrate that modeling is effective in separating the importance of different processes and complements pure experimental approaches. Modeling results can aid planning and designing efficient sediment control measures and guide the focus of experimental studies.

  3. Modelling suspended-sediment propagation and related heavy metal contamination in floodplains: a parameter sensitivity analysis

    Science.gov (United States)

    Hostache, R.; Hissler, C.; Matgen, P.; Guignard, C.; Bates, P.

    2014-09-01

    Fine sediments represent an important vector of pollutant diffusion in rivers. When deposited in floodplains and riverbeds, they can be responsible for soil pollution. In this context, this paper proposes a modelling exercise aimed at predicting transport and diffusion of fine sediments and dissolved pollutants. The model is based upon the Telemac hydro-informatic system (dynamical coupling Telemac-2D-Sysiphe). As empirical and semiempirical parameters need to be calibrated for such a modelling exercise, a sensitivity analysis is proposed. An innovative point in this study is the assessment of the usefulness of dissolved trace metal contamination information for model calibration. Moreover, for supporting the modelling exercise, an extensive database was set up during two flood events. It includes water surface elevation records, discharge measurements and geochemistry data such as time series of dissolved/particulate contaminants and suspended-sediment concentrations. The most sensitive parameters were found to be the hydraulic friction coefficients and the sediment particle settling velocity in water. It was also found that model calibration did not benefit from dissolved trace metal contamination information. Using the two monitored hydrological events as calibration and validation, it was found that the model is able to satisfyingly predict suspended sediment and dissolve pollutant transport in the river channel. In addition, a qualitative comparison between simulated sediment deposition in the floodplain and a soil contamination map shows that the preferential zones for deposition identified by the model are realistic.

  4. Quantifying and Modelling Long Term Sediment Dynamics in Catchments in Western Europe

    Science.gov (United States)

    Notebaert, B.; De Brue, H.; Verstraeten, G.; Broothaerts, N.

    2015-12-01

    Quantification of sediment dynamics allows to get insight in driving forces and internal dynamics of the sediment cascade system. A useful tool to achieve this is the sediment budget approach, which encompasses the quantification of different sinks and sources. A Holocene time-differentiated sediment budget has been constructed for the Belgian Dijle River catchment (720 km²), based on a large set of field data. The results show how soil erosion is driven by land use changes over longer timescales. Sediment redistribution and the relative importance of the different sinks also vary over time, mainly as a result of changing land use and related landscape connectivity. However, the coarse temporal resolution typically associated with Holocene studies complicates the understanding of sub-millennial scale processes. In a second step, the field-based sediment budget was combined with a modeling approach using Watem/Sedem, a spatially distributed model that simulates soil erosion and colluvial deposition. After validation of the model calibration against the sediment budget, the model was used in a sensitivity analysis. Results confirm the overwhelming influence of human land use on both soil erosion and landscape connectivity, whereas the climatic impact is comparatively small. In addition to catchment-wide simulations, the model also served to test the relative importance of lynchets and dry valleys in different environments. Finally, the geomorphic model was used to simulate past land use, taking into account equifinality. For this purpose, a large series of hypothetical time-independent land use maps of the Dijle catchment were modeled based on a multi-objective allocation algorithm, and applied in Watem/Sedem. Modeled soil erosion and sediment deposition outcomes for each scenario were subsequently compared with the field-based record, taking into account uncertainties. As such, the model allows to evaluate and select realistic land use scenarios for the Holocene.

  5. Modelling intertidal sediment transport for nutrient change and climate change scenarios.

    Science.gov (United States)

    Wood, Rose; Widdows, John

    2003-10-01

    A model of intertidal sediment transport, including effects of bioturbation and biostabilisation, was applied to two transects on the east coast of England: Leverton (within the Wash) and Skeffling (in the Humber Estuary). The physical and biological parameters were chosen to represent four 1-year scenarios: a baseline year (1995), the same year but with estuarine nitrate inputs reduced by 50% and by 16%, and a year with climate change effects estimated for 2050. The changes in nitrate supply can potentially change microphytobenthos numbers within the surface sediment, which will then affect erodibility. The model results show a range of behaviour determined by bathymetry, external forcing and biotic state. When intertidal sediment transport is dominated by external sediment supply, the model produces highest deposition at the most offshore point, and there is greatest deposition in the winter and spring, when offshore sediment concentrations are highest. When intertidal processes dominate intertidal sediment transport, there is a peak of deposition at the high-shore level and erosion at mid-tide levels. The greatest deposition now occurs in winter and summer, when low chlorophyll levels mean that the sediment is most erodible. The Skeffling transect was dominated by intertidal processes for the baseline scenario and with a 16% reduction in nitrate. Under the climate change (warm winter) scenario, the Skeffling transect was dominated by external sediment supply. The scenario with 50% reduction in nitrate gave intermediate behaviour at Skeffling (intertidally driven during the winter and summer, and governed by offshore sediment supply during spring and autumn). The Leverton transect was dominated by offshore sediment supply for all the scenarios.

  6. Sediment carbon fate in phreatic karst (Part 1): Conceptual model development

    Science.gov (United States)

    Husic, A.; Fox, J.; Agouridis, C.; Currens, J.; Ford, W.; Taylor, C.

    2017-06-01

    Recent research has paid increased attention to quantifying the fate of carbon pools within fluvial networks, but few, if any, studies consider the fate of sediment organic carbon in fluviokarst systems despite that karst landscapes cover 12% of the earth's land surface. The authors develop a conceptual model of sediment carbon fate in karst terrain with specific emphasis upon phreatic karst conduits, i.e., those located below the groundwater table that have the potential to trap surface-derived sediment and turnover carbon. To assist with their conceptual model development, the authors study a phreatic system and apply a mixture of methods traditional and novel to karst studies, including electrical resistivity imaging, well drilling, instantaneous velocimetry, dye tracing, stage recording, discrete and continuous sediment and water quality sampling, and elemental and stable carbon isotope fingerprinting. Results show that the sediment transport carrying capacity of the phreatic karst water is orders of magnitude less than surface streams during storm-activated periods promoting deposition of fine sediments in the phreatic karst. However, the sediment transport carrying capacity is sustained long after the hydrologic event has ended leading to sediment resuspension and prolonged transport. The surficial fine grained laminae occurs in the subsurface karst system; but unlike surface streams, the light-limited conditions of the subsurface karst promotes constant heterotrophy leading to carbon turnover. The coupling of the hydrological processes leads to a conceptual model that frames phreatic karst as a biologically active conveyor of sediment carbon that recharges degraded organic carbon back to surface streams. For example, fluvial sediment is estimated to lose 30% of its organic carbon by mass during a one year temporary residence within the phreatic karst. It is recommended that scientists consider karst pathways when attempting to estimate organic matter stocks

  7. Characterizing biogenous sediments using multibeam echosounder backscatter data - Estimating power law parameter utilizing various models

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, B.; Kodagali, V.N.

    In this paper, Helmholtz-Kirchhoff (H-K) roughness model is employed to characterize seafloor sediment and roughness parameters from the eastern sector of the Southern Oceans The multibeam- Hydroswcep system's angular-backscatter data, which...

  8. Dynamics and recovery of a sediment-exposed Chironomus riparius population: A modelling approach.

    Science.gov (United States)

    Diepens, Noël J; Beltman, Wim H J; Koelmans, Albert A; Van den Brink, Paul J; Baveco, Johannes M

    2016-06-01

    Models can be used to assess long-term risks of sediment-bound contaminants at the population level. However, these models usually lack the coupling between chemical fate in the sediment, toxicokinetic-toxicodynamic processes in individuals and propagation of individual-level effects to the population. We developed a population model that includes all these processes, and used it to assess the importance of chemical uptake routes on a Chironomus riparius population after pulsed exposure to the pesticide chlorpyrifos. We show that particle ingestion is an important additional exposure pathway affecting C. riparius population dynamics and recovery. Models ignoring particle ingestion underestimate the impact and the required recovery times, which implies that they underestimate risks of sediment-bound chemicals. Additional scenario studies showed the importance of selecting the biologically relevant sediment layer and showed population effects in the long term.

  9. A three-dimensional, wave-current coupled, sediment transport model for POM

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-hua

    2010-01-01

    In the high-energy environment of coastal seas and estuaries,strong sediment resuspension/ deposition events are driven by surface waves,tides,winds and buoyancy driven currents.In recent years,A POM based three-dimensional ,wave-current coupled ,sediment transport model has been developed by the University of New South Wales.This paper presents several examples of the model applications to study sediment dynamics in the environments where forcings such as waves,tides, and winds are equally important to affect sediment fluxes and distributions.Firstly,the sediment transport model coupled to the Yellow Sea general circulation model and a third generation wave model SWAN was implemented in the Yellow Sea to study the dynamics of the sediment transport and resuspension in the northern Jiangsu shoal-water(NJSW).The sediment distributions and fluxes and their inter-annual variability were studied by realistic numerical simulations.The study found that the surface waves played a dominant role over the tides to form the turbidity maxima along the muddy coast of NJSW. Secondly,the sediment transport model was used to explore the effect of suspended sediment-induced stratificationin the bottom boundary layer(BBL).The model uses a re-parameterized bottom drag coefficient Cd that incorporates a linear stability function of flux Richardson number RsThe study has shown that the sediment induced stratification in the BBL reduces the vertical eddy viscosity and bottom shear stress in comparison with the model prediction in a neutrally stratified BBL.In response to these apparent reductions,the tidal current shear is increased and sediments are abnormally concentrated within a thin wall layer that is overlain by a thicker layer with much smaller concentration.The formation of this fluid-mud layer near the seabed has led to a significant reduction in the total sediment transport.This study contributes to the understanding of formations of tidal flats along the coasts of turbid seas

  10. Monte Carlo path sampling approach to modeling aeolian sediment transport

    Science.gov (United States)

    Hardin, E. J.; Mitasova, H.; Mitas, L.

    2011-12-01

    Coastal communities and vital infrastructure are subject to coastal hazards including storm surge and hurricanes. Coastal dunes offer protection by acting as natural barriers from waves and storm surge. During storms, these landforms and their protective function can erode; however, they can also erode even in the absence of storms due to daily wind and waves. Costly and often controversial beach nourishment and coastal construction projects are common erosion mitigation practices. With a more complete understanding of coastal morphology, the efficacy and consequences of anthropogenic activities could be better predicted. Currently, the research on coastal landscape evolution is focused on waves and storm surge, while only limited effort is devoted to understanding aeolian forces. Aeolian transport occurs when the wind supplies a shear stress that exceeds a critical value, consequently ejecting sand grains into the air. If the grains are too heavy to be suspended, they fall back to the grain bed where the collision ejects more grains. This is called saltation and is the salient process by which sand mass is transported. The shear stress required to dislodge grains is related to turbulent air speed. Subsequently, as sand mass is injected into the air, the wind loses speed along with its ability to eject more grains. In this way, the flux of saltating grains is itself influenced by the flux of saltating grains and aeolian transport becomes nonlinear. Aeolian sediment transport is difficult to study experimentally for reasons arising from the orders of magnitude difference between grain size and dune size. It is difficult to study theoretically because aeolian transport is highly nonlinear especially over complex landscapes. Current computational approaches have limitations as well; single grain models are mathematically simple but are computationally intractable even with modern computing power whereas cellular automota-based approaches are computationally efficient

  11. ESTIMATION OF THE WANDA GLACIER (SOUTH SHETLANDS SEDIMENT EROSION RATE USING NUMERICAL MODELLING

    Directory of Open Access Journals (Sweden)

    Kátia Kellem Rosa

    2013-09-01

    Full Text Available Glacial sediment yield results from glacial erosion and is influenced by several factors including glacial retreat rate, ice flow velocity and thermal regime. This paper estimates the contemporary subglacial erosion rate and sediment yield of Wanda Glacier (King George Island, South Shetlands. This work also examines basal sediment evacuation mechanisms by runoff and glacial erosion processes during the subglacial transport. This is small temperate glacier that has seen retreating for the last decades. In this work, we examine basal sediment evacuation mechanisms by runoff and analyze glacial erosion processes occurring during subglacial transport. The glacial erosion rate at Wanda Glacier, estimated using a numerical model that consider sediment evacuated to outlet streams, ice flow velocity, ice thickness and glacier area, is 1.1 ton m yr-1.

  12. Evaluating the hydrological component of the new catchment-scale sediment delivery model LAPSUS-D

    Science.gov (United States)

    Keesstra, S. D.; Temme, A. J. A. M.; Schoorl, J. M.; Visser, S. M.

    2014-05-01

    Physically-based, catchment scale sediment delivery models have become increasingly complex, sophisticated and are suitable for a diverse range of environmental contexts. However, in their attempts to best represent the physical processes of erosion and deposition, these models require large and detailed input datasets. When such data are unavailable, annual sediment yield models are relied upon. However, in this class of models, widely available data such as daily precipitation and discharge are disregarded resulting in a reduction in temporal accuracy. To fill this scientific and management gap, the landscape evolution model LAPSUS was adapted (LAPSUS-D) for a meso-scale catchment to model sediment yield on a daily resolution. The water balance component within the model enables the calibration of the model in terms of water discharge with measured daily discharge at the outlet. This methodology is especially important when modeling sediment yield from catchments which are ungaged catchments in terms of sediment, but where hydrological data are available. As the simulation of sediment yield was the main objective of the study, the calibration focused on peak discharge. The focus on peak discharge provides insight into the capability of the model to generate, route and deliver sediment at the outlet of a meso-scale catchment. LAPSUS-D has daily temporal resolution and requires a 10 to 30 m pixel size DEM, soil map, land-use map and daily hydrological records (precipitation and discharge). In this paper we present the first assessment of the hydrological model performance and an analysis of the sensitivity of the model to input parameters. Our study site is a 23-km2 catchment in Upper Nysa Szalona, southwest Poland with temperate climate.

  13. A lumped model for rotational modes in periodic solid composites

    KAUST Repository

    Peng, Pai

    2013-10-01

    We present a lumped model to study the rotational modes in a type of two-dimensional periodic solid composites comprised of a square array of rubber-coated steel cylinders embedded in an epoxy matrix. The model captures the physical essence of rotational modes in such systems for various combinations of material parameters, and, therefore it is able to describe the transition behaviour when the system is gradually adjusted from an elastic metamaterial to an elastic phononic crystal. From the model, we can define a transition zone which separates the typical elastic metamaterials and the phononic crystals.

  14. A Liquid-Solid Coupling Hemodynamic Model with Microcirculation Load

    Directory of Open Access Journals (Sweden)

    Bai Li

    2016-01-01

    Full Text Available From the aspect of human circulation system structure, a complete hemodynamic model requires consideration of the influence of microcirculation load effect. This paper selected the seepage in porous media as the simulant of microcirculation load. On the basis of a bi-directional liquid-solid coupling tube model, we built a liquid-solid-porous media seepage coupling model. The simulation parameters accorded with the physiological reality. Inlet condition was set as transient single-pulse velocity, and outlet as free outlet. The pressure in the tube was kept at the state of dynamic stability in the range of 80–120 mmHg. The model was able to simulate the entire propagating process of pulse wave. The pulse wave velocity simulated was 6.25 m/s, which accorded with the physiological reality. The complex pressure wave shape produced by reflections of pressure wave was also observed. After the model changed the cardiac cycle length, the pressure change according with actual human physiology was simulated successfully. The model in this paper is well-developed and reliable. It demonstrates the importance of microcirculation load in hemodynamic model. Moreover the properties of the model provide a possibility for the simulation of dynamic adjustment process of human circulation system, which indicates a promising prospect in clinical application.

  15. Laboratory And Lysimeter Experimentation And Transport Modeling Of Neptunium And Strontium In Savannah River Site Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Daniel I.; Powell, B. A.; Miller, Todd J.

    2012-09-24

    The Savannah River Site (SRS) conducts performance assessment (PA) calculations to determine the appropriate amount of low-level radiological waste that can be safely disposed on site. Parameters are included in these calculations that account for the interaction between the immobile solid phase and the mobile aqueous phase. These parameters are either the distribution coefficient (K{sub d} value) or the apparent solubility value (K{sub sp}). These parameters are readily found in the literature and are used throughout the DOE complex. One shortcoming of K{sub d} values is that they are only applicable to a given set of solid and aqueous phase conditions. Therefore, a given radionuclide may have several K{sub d} values as it moves between formations and comes into contact with different solids and different aqueous phases. It is expected that the K{sub d} construct will be appropriate to use for a majority of the PA and for a majority of the radionuclides. However, semi-mechanistic models would be more representative in isolated cases where the chemistry is especially transitory or the radionuclide chemistry is especially complex, bringing to bear multiple species of varying sorption tendencies to the sediment. Semi-mechanistic models explicitly accommodate the dependency of K{sub d} values, or other sorption parameters, on contaminant concentration, competing ion concentrations, pH-dependent surface charge on the adsorbent, and solute species distribution. Incorporating semi-mechanistic concepts into geochemical models is desirable to make the models more robust and technically defensible. Furthermore, these alternative models could be used to augment or validate a Kd?based DOE Order 435.1 Performance Assessment. The objectives of this study were to: 1) develop a quantitative thermodynamically-based model for neptunium sorption to SRS sediments, and 2) determine a sorption constant from an SRS 11-year lysimeter study. The modeling studies were conducted with

  16. Laboratory And Lysimeter Experimentation And Transport Modeling Of Neptunium And Strontium In Savannah River Site Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Kaplan, Daniel I.; Powell, B. A.; Miller, Todd J.

    2012-09-24

    The Savannah River Site (SRS) conducts performance assessment (PA) calculations to determine the appropriate amount of low-level radiological waste that can be safely disposed on site. Parameters are included in these calculations that account for the interaction between the immobile solid phase and the mobile aqueous phase. These parameters are either the distribution coefficient (K{sub d} value) or the apparent solubility value (K{sub sp}). These parameters are readily found in the literature and are used throughout the DOE complex. One shortcoming of K{sub d} values is that they are only applicable to a given set of solid and aqueous phase conditions. Therefore, a given radionuclide may have several K{sub d} values as it moves between formations and comes into contact with different solids and different aqueous phases. It is expected that the K{sub d} construct will be appropriate to use for a majority of the PA and for a majority of the radionuclides. However, semi-mechanistic models would be more representative in isolated cases where the chemistry is especially transitory or the radionuclide chemistry is especially complex, bringing to bear multiple species of varying sorption tendencies to the sediment. Semi-mechanistic models explicitly accommodate the dependency of K{sub d} values, or other sorption parameters, on contaminant concentration, competing ion concentrations, pH-dependent surface charge on the adsorbent, and solute species distribution. Incorporating semi-mechanistic concepts into geochemical models is desirable to make the models more robust and technically defensible. Furthermore, these alternative models could be used to augment or validate a Kd?based DOE Order 435.1 Performance Assessment. The objectives of this study were to: 1) develop a quantitative thermodynamically-based model for neptunium sorption to SRS sediments, and 2) determine a sorption constant from an SRS 11-year lysimeter study. The modeling studies were conducted with

  17. Prediction of sedimentation using integration of RS, RUSLE model and GIS in Cameron Highlands, Pahang, Malaysia

    Science.gov (United States)

    Ghani, A. H. A.; Lihan, T.; Rahim, S. A.; Musthapha, M. A.; Idris, W. M. R.; Rahman, Z. A.

    2013-11-01

    Soil erosion and sediment yield are strongly affected by land use change. Spatially distributed erosion models are of great interest to predict soil erosion loss and sediment yield. Hence, the objective of this study was to determine sediment yield using Revised Universal Soil Loss Equation (RUSLE) model in Geographical Information System (GIS) environment at Cameron Highlands, Pahang, Malaysia. Sediment yield at the study area was determined using RUSLE model in GIS environment The RUSLE factors were computed by utilizing information on rainfall erosivity (R) using interpolation of rainfall data, soil erodibility (K) using soil map and field measurement, vegetation cover (C) using satellite images, length and steepness (LS) using contour map and conservation practices using satellite images based on land use/land cover. Field observations were also done to verify the predicted sediment yield. The results indicated that the rate of sediment yield in the study area ranged from very low to extremely high. The higher SY value can be found at middle and lower catchments of Cameron Highland. Meanwhile, the lower SY value can be found at the north part of the study area. Sediment yield value turned out to be higher close to the river due to the topographic characteristic, vegetation type and density, climate and land use within the drainage basin.

  18. Modelling of Cohesive Sediment Transport in the Maasmond Area

    NARCIS (Netherlands)

    Wang, L.

    2006-01-01

    In the Dutch coastal zone, where the marine environment is highly dynamic owing to tidal currents, wind-driven, wave-driven, and density-driven currents and waves, the cohesive sediment dynamics is always a great concern to transportation authority and coastal managers. So far, a lot research has

  19. Modelling of sedimentation processes inside Roseires Reservoir (Sudan)

    NARCIS (Netherlands)

    Omer, A.Y.A.; Ali, Y.S.A.; Roelvink, J.A.; Dastgheib, A.; Paron, P.; Crosato, A.

    2015-01-01

    Roseires Reservoir, located on the Blue Nile River in Sudan, is the first trap to the sediments coming from the vast upper river catchment in Ethiopia, which suffers from high erosion and desertification problems. The reservoir has already lost more than one-third of its storage capacity due to sedi

  20. Modelling of sedimentation processes inside Roseires Reservoir (Sudan) (discussion)

    NARCIS (Netherlands)

    Omer, A.Y.A.; Ali, Y.S.A.; Roelvink, J.A.; Dastgheib, A.; Paron, P.; Crosato, A.

    2014-01-01

    Discussion paper. Roseires Reservoir, located on the Blue Nile River, in Sudan, is the first trap to the sediments coming from the upper catchment in Ethiopia, which suffers from high erosion and desertification problems. The reservoir lost already more than one third of its 5 storage capacity due t

  1. Modelling of sedimentation processes inside Roseires Reservoir (Sudan) (abstract)

    NARCIS (Netherlands)

    Ali, Y.S.A.; Omer, A.Y.A.; Crosato, A.

    2013-01-01

    Roseires Reservoir is located on the Blue Nile River, in Sudan (figure 1). It is the first trap to the sediments coming from the upper catchment in Ethiopia, which suffers from high erosion and desertification problems. The reservoir lost already more than one third of its storage capacity due to se

  2. Sediment Acoustics: Wideband Model, Reflection Loss and Ambient Noise Inversion

    Science.gov (United States)

    2011-09-01

    grain contact in water- saturated sand," J. Acoust. Soc. Am., vol. 124, pp. EL296-301, (2008). N. P. Chotiros, and M. J. Isakson. "Shear and...34Frame bulk modulus of porous granular marine sediments," J. Acoust. Soc. Am. 120, 699-710, (2006). B. J. Kraft and C. P. de Moustier, "Detailed

  3. Modelling of sediment transport: link in a chain

    NARCIS (Netherlands)

    De Vries, M.

    1977-01-01

    Rather than reporting on a specific topic of current research in the broad field of sediment transport and river morphology, the writer will give a general contemplation on the state of the art. This will not be a review in the usual sense. The alloted space would then be filled easily with referenc

  4. Sediment transport modelling in wadi Chemora during flood flow events

    Directory of Open Access Journals (Sweden)

    Berghout Ali

    2016-12-01

    Full Text Available The sediment transport is a complex phenomenon by its intermittent nature, randomness and by its spatiotemporal discontinuity. By reason of its scale, it constitutes a major constraint for development; it decreases storage capacity of dams and degrades state of ancillary structures.

  5. Modelling Dissolved Oxygen/Sediment Oxygen Demand under Ice in a Shallow Eutrophic Prairie Reservoir

    Directory of Open Access Journals (Sweden)

    Julie A. Terry

    2017-02-01

    Full Text Available Dissolved oxygen is an influential factor of aquatic ecosystem health. Future predictions of oxygen deficits are paramount for maintaining water quality. Oxygen demands depend greatly on a waterbody’s attributes. A large sediment–water interface relative to volume means sediment oxygen demand has greater influence in shallow systems. In shallow, ice-covered waterbodies the potential for winter anoxia is high. Water quality models offer two options for modelling sediment oxygen demand: a zero-order constant rate, or a sediment diagenesis model. The constant rate is unrepresentative of a real system, yet a diagenesis model is difficult to parameterise and calibrate without data. We use the water quality model CE-QUAL-W2 to increase the complexity of a zero-order sediment compartment with limited data. We model summer and winter conditions individually to capture decay rates under-ice. Using a semi-automated calibration method, we find an annual pattern in sediment oxygen demand that follows the trend of chlorophyll-a concentrations in a shallow, eutrophic Prairie reservoir. We use chlorophyll-a as a proxy for estimation of summer oxygen demand and winter decay. We show that winter sediment oxygen demand is dependent on the previous summer’s maximum chlorophyll-a concentrations.

  6. A model for simulating the deposition of water-lain sediments in dryland environments

    Directory of Open Access Journals (Sweden)

    M. A. Bunch

    2004-01-01

    Full Text Available A numerical process-imitating model, the Discrete Storm Event Sedimentation Simulator (DSESS, has been developed to represent the climatic and hydraulic conditions of drylands in modelling their geomorphological development and sedimentary facies distributions. The ultimate aim is to provide insights into the lateral variability of permeability in the Triassic Sandstone aquifers of the UK for the study of solute movement. DSESS employs discrete storm-flood automata, released across a cellular landscape, to model sediment transport: erosion, migration and deposition. Sediment classes with different grain sizes can be modelled. Empirical process-based equations are used to quantify the movement of the automata, their erosion potential, sediment-carrying capacity and interaction with the underlying sediments. The approach emphasises the sequence of dryland storm events and associated floods rather than their timing. Flood events are assumed to be discrete in time. Preliminary tests carried out with DSESS using simple systems and idealised initial conditions produce lithological and land surface features characteristic of dryland settings and indicate the potential of the model for large-scale, long-time modelling of sedimentary facies development. Markedly different results are observed across the range of tests carried out in response to the non-linear interactions between the different elements of the landscape and the floodwaters simulated with DSESS. Simulations show that sediment accumulations develop concave upward radial profiles, plano-convex cross-profiles and possess a general lateral grading of sediment with distance from source. The internal grain size architecture shows evidence of both persistent and rapidly changing flow conditions, with both lateral and longitudinal stepping of coarse bodies produced by ‘scour and fill’ events and random avulsions. Armoured layers form so that near-surface sediments have increased likelihood of

  7. Advanced impedance modeling of solid oxide electrochemical cells

    DEFF Research Database (Denmark)

    Graves, Christopher R.; Hjelm, Johan

    2014-01-01

    Impedance spectroscopy is a powerful technique for detailed study of the electrochemical and transport processes that take place in fuel cells and electrolysis cells, including solid oxide cells (SOCs). Meaningful analysis of impedance measurements is nontrivial, however, because a large number o...... analysis methods and integrates the analysis process in a modular workflow – data validation (Kramers-Kronig), clean-up, visualization (DRT and others), modeling (nonlinear least-squares fitting), and final plotting for publication....

  8. Impedance Modeling of Solid Oxide Fuel Cell Cathodes

    DEFF Research Database (Denmark)

    Mortensen, Jakob Egeberg; Søgaard, Martin; Jacobsen, Torben

    2010-01-01

    A 1-dimensional impedance model for a solid oxide fuel cell cathode is formulated and applied to a cathode consisting of 50/50 wt% strontium doped lanthanum cobaltite and gadolinia doped ceria. A total of 42 impedance spectra were recorded in the temperature range: 555-852°C and in the oxygen...... physical parameters such as the cathode thickness. ©2010 COPYRIGHT ECS - The Electrochemical Society...

  9. Treatment of sediments from soil washing plants. Investigation of the suitability of a gas/solids fluidized bed bioreactor for the decontamination; Bodenwaschanlagen-Sedimente behandeln. Untersuchungen der Eignung des Gas/Feststoff-Wirbelschicht-Bioreaktors zur Dekontaminierung

    Energy Technology Data Exchange (ETDEWEB)

    Behns, W.; Haida, H. [Magdeburg Univ. (Germany). Inst. fuer Apparate- und Umwelttechnik; Friedrich, C. [Allgaier-Werke, Uhingen (Germany)

    1997-09-01

    This article deals with the possibility of microbiological decontamination of sediments from soil washing plants in gas/solids fluidized bed bioreactors. The sediments are pressed to granulates. The pollutants which are removed are mineral oil hydrocarbons. The degradation results of this process are presented, the process seems to be an alternative to common waste treatment processes. (SR) [Deutsch] Die mikrobiologische Dekontaminierung sandiger Boeden in einem Gas/Feststoff-Wirbelschicht-Bioreaktor ist eine erfolgversprechende Alternative zu anderen biologischen Reinigungsverfahren. Die biologische Dekontaminierung von Schlufffraktionen oder von Bodenwaschanlagensedimenten (BWS) ist deutlich schwieriger. In der Literatur werden vor allem Verfahren unter Einsatz von Suspensionsreaktoren verwendet, um fuer Feinkorn-Fraktionen eine biologische Reinigung zu ermoeglichen. Hier soll ueber Untersuchungen berichtet werden, mit denen die Eignung des Gas/Feststoff-Wirbelschicht-Bioreaktors fuer die Dekontaminierung derartiger Boeden ueberprueft werden sollte. (orig.)

  10. Two-dimensional modeling of sediments deposits in dam reservoirs in Algeria; Modelisation bidimensionnelle du depot de sediments dans un barrage en Algerie

    Energy Technology Data Exchange (ETDEWEB)

    Bessenasse, M. [Universite SAAD Dahleb (Blida), Lab. de Recherche des Sciences de l' Eau LRS EAU ENP, Alger (Algeria); Kettab, A. [Ecole Nationale Polytechnique, LRS-EAU, Alger (Algeria); Paquier, A. [Cemagref de Lyon, Unite de Recherche Hydrologie-Hydraulique, 69 (France)

    2004-07-01

    The method to build a numerical model intended to predict the formation and the change of sediment deposits upstream from a dam is presented. From information about the inputs of water and sediments coming from the catchment supported by a QdF type hydrological analysis, a horizontal 2-D hydraulic model which couples shallow water equations and one equation for advection and diffusion of sediment concentration is used. Applying this model to Zardezas reservoir in Skikda (Algeria) region shows, on the one hand, the practical difficulties met on such case and, on the other hand, the potentialities of such a method for the management of Algerian reservoirs. (authors)

  11. Design Through Manufacturing: The Solid Model - Finite Element Analysis Interface

    Science.gov (United States)

    Rubin, Carol

    2003-01-01

    State-of-the-art computer aided design (CAD) presently affords engineers the opportunity to create solid models of machine parts which reflect every detail of the finished product. Ideally, these models should fulfill two very important functions: (1) they must provide numerical control information for automated manufacturing of precision parts, and (2) they must enable analysts to easily evaluate the stress levels (using finite element analysis - FEA) for all structurally significant parts used in space missions. Today's state-of-the-art CAD programs perform function (1) very well, providing an excellent model for precision manufacturing. But they do not provide a straightforward and simple means of automating the translation from CAD to FEA models, especially for aircraft-type structures. The research performed during the fellowship period investigated the transition process from the solid CAD model to the FEA stress analysis model with the final goal of creating an automatic interface between the two. During the period of the fellowship a detailed multi-year program for the development of such an interface was created. The ultimate goal of this program will be the development of a fully parameterized automatic ProE/FEA translator for parts and assemblies, with the incorporation of data base management into the solution, and ultimately including computational fluid dynamics and thermal modeling in the interface.

  12. Past and present of sediment and carbon biogeochemical cycling models

    Directory of Open Access Journals (Sweden)

    F. T. Mackenzie

    2004-01-01

    Full Text Available The global carbon cycle is part of the much more extensive sedimentary cycle that involves large masses of carbon in the Earth's inner and outer spheres. Studies of the carbon cycle generally followed a progression in knowledge of the natural biological, then chemical, and finally geological processes involved, culminating in a more or less integrated picture of the biogeochemical carbon cycle by the 1920s. However, knowledge of the ocean's carbon cycle behavior has only within the last few decades progressed to a stage where meaningful discussion of carbon processes on an annual to millennial time scale can take place. In geologically older and pre-industrial time, the ocean was generally a net source of CO2 emissions to the atmosphere owing to the mineralization of land-derived organic matter in addition to that produced in situ and to the process of CaCO3 precipitation. Due to rising atmospheric CO2 concentrations because of fossil fuel combustion and land use changes, the direction of the air-sea CO2 flux has reversed, leading to the ocean as a whole being a net sink of anthropogenic CO2. The present thickness of the surface ocean layer, where part of the anthropogenic CO2 emissions are stored, is estimated as of the order of a few hundred meters. The oceanic coastal zone net air-sea CO2 exchange flux has also probably changed during industrial time. Model projections indicate that in pre-industrial times, the coastal zone may have been net heterotrophic, releasing CO2 to the atmosphere from the imbalance between gross photosynthesis and total respiration. This, coupled with extensive CaCO3 precipitation in coastal zone environments, led to a net flux of CO2 out of the system. During industrial time the coastal zone ocean has tended to reverse its trophic status toward a non-steady state situation of net autotrophy, resulting in net uptake of anthropogenic CO2 and storage of carbon in the coastal ocean, despite the significant calcification

  13. MAST-1D, a Model to Route Sediment and Tracers in Channel-Floodplain Complexes

    Science.gov (United States)

    Viparelli, E.; Lauer, J. W.; Belmont, P.

    2014-12-01

    Sediment exchange between the channel and floodplain can occur via meander migration, overbank deposition or erosion, and channel widening or narrowing. Depending on channel and floodplain history, floodplains can act either as sources or sinks of bed material and/or wash load. The Morphodynamics And Sediment Tracers in 1D program (MAST-1D) is a numerical model built to describe grain size specific transport of sediment and tracers and the long-term - i.e. decadal and longer - evolution of channel floodplain complexes. MAST-1D differs from other 1D numerical models because it allows for 1) uneven exchange of sediment and tracers between the river channel and the floodplain, 2) temporal changes in channel geometry, bed elevation and floodplain thickness, which result in changes in the channel hydraulic capacity, and 3) temporal changes of size distribution and tracer content in the floodplain, in the load and in the underlying substrate. Under conditions of constant base level, water and sediment supply, the main assumptions in the model result in the system evolving asymptotically toward a steady state wherein channel bed erosion is balanced by channel bed deposition. When at this condition, the amount of sediment deposited on the floodplain through point bar deposition and overbank sedimentation is balanced by the erosion of sediment from the floodplain through lateral migration. However, imbalances in floodplain storage can persist for many years even when the channel bed elevation and size distribution are near steady state. The MAST-1D program is applied to study the long term response of a sand bed river, an 80 km long reach of the Minnesota River between Mankato and Jordan, Minnesota, to changes in flow regime and the sediment load due to the development of intensive agriculture in the watershed. The simulations are performed in successive phases, the model is first set up so that under the best estimates available for pre-agriculture conditions, channel

  14. A model for simulating the deposition of water-lain sediments in dryland environments

    Science.gov (United States)

    Bunch, M. A.; Mackay, R.; Tellam, J. H.; Turner, P.

    A numerical process-imitating model, the Discrete Storm Event Sedimentation Simulator (DSESS), has been developed to represent the climatic and hydraulic conditions of drylands in modelling their geomorphological development and sedimentary facies distributions. The ultimate aim is to provide insights into the lateral variability of permeability in the Triassic Sandstone aquifers of the UK for the study of solute movement. DSESS employs discrete storm-flood automata, released across a cellular landscape, to model sediment transport: erosion, migration and deposition. Sediment classes with different grain sizes can be modelled. Empirical process-based equations are used to quantify the movement of the automata, their erosion potential, sediment-carrying capacity and interaction with the underlying sediments. The approach emphasises the sequence of dryland storm events and associated floods rather than their timing. Flood events are assumed to be discrete in time. Preliminary tests carried out with DSESS using simple systems and idealised initial conditions produce lithological and land surface features characteristic of dryland settings and indicate the potential of the model for large-scale, long-time modelling of sedimentary facies development. Markedly different results are observed across the range of tests carried out in response to the non-linear interactions between the different elements of the landscape and the floodwaters simulated with DSESS. Simulations show that sediment accumulations develop concave upward radial profiles, plano-convex cross-profiles and possess a general lateral grading of sediment with distance from source. The internal grain size architecture shows evidence of both persistent and rapidly changing flow conditions, with both lateral and longitudinal stepping of coarse bodies produced by ‘scour and fill’ events and random avulsions. Armoured layers form so that near-surface sediments have increased likelihood of preservation

  15. Modelling importance of sediment effects on fate and transport of enterococci in the Severn Estuary, UK.

    Science.gov (United States)

    Gao, Guanghai; Falconer, Roger A; Lin, Binliang

    2013-02-15

    The paper detailed a water quality modelling study of a hyper-tidal estuary, undertaken to assess the impact of various bacteria input loads on the receiving waters in a coastal basin in the UK, by using the model developed in previous study of the same authors enterococci, used as the indicators for bathing water quality under the new European Union (EU) Bathing Water Directive, were numerically modelled using a hydro-environmental model. In particular, the numerical model used in this study includes the effects of sediment on bacteria transport processes in surface water. Finally, the importance of sediment bacteria inputs on the bathing water quality was also investigated under different weather and tidal condition. During spring tide, the bacteria input from the bed sediments are dominant for both wet and dry weather conditions. During neap tides and during dry weather conditions the inputs of bacteria from the bed sediment were still dominant, but during wet weather conditions the inputs from river were dominant. Under different tidal flow conditions some parameters had a more significant role than others. During high flow conditions the sediment re-suspensions processes were dominant, therefore the bed bacteria concentrations played a dominant role on the overall bacteria concentration levels in the water column. In contrast, during low flow conditions sediment deposition prevails and bacteria are removed from the water column. The partition coefficient was found to be more important than the bed bacteria concentrations, during low flow conditions.

  16. A 2-D process-based model for suspended sediment dynamics: A first step towards ecological modeling

    Science.gov (United States)

    Achete, F. M.; van der Wegen, M.; Roelvink, D.; Jaffe, B.

    2015-01-01

    In estuaries suspended sediment concentration (SSC) is one of the most important contributors to turbidity, which influences habitat conditions and ecological functions of the system. Sediment dynamics differs depending on sediment supply and hydrodynamic forcing conditions that vary over space and over time. A robust sediment transport model is a first step in developing a chain of models enabling simulations of contaminants, phytoplankton and habitat conditions. This works aims to determine turbidity levels in the complex-geometry delta of the San Francisco estuary using a process-based approach (Delft3D Flexible Mesh software). Our approach includes a detailed calibration against measured SSC levels, a sensitivity analysis on model parameters and the determination of a yearly sediment budget as well as an assessment of model results in terms of turbidity levels for a single year, water year (WY) 2011. Model results show that our process-based approach is a valuable tool in assessing sediment dynamics and their related ecological parameters over a range of spatial and temporal scales. The model may act as the base model for a chain of ecological models assessing the impact of climate change and management scenarios. Here we present a modeling approach that, with limited data, produces reliable predictions and can be useful for estuaries without a large amount of processes data.

  17. Coagulation-Sedimentation-Extraction Pretreatment Methods for The Removal of Suspended Solids and Residual Oil From Palm Oil Mill Effluent (Pome

    Directory of Open Access Journals (Sweden)

    Abdul Latif Ahmad, Norliza Ibrahim , Suzylawati Ismail and Subhash Bhatia

    2012-08-01

    Full Text Available Suspended solids and residual oil removal in a liquid are relevant to numerous research areas and industry. The suspended solid cannot be removed completely by plain settling. Large and heavy particles can settle out readily, but smaller and lighter particles settle very slowly or in some cases do not settle at all. Because of this, it requires efficient physical-chemical pretreatment methods.   Our current research is to study the pretreatment methods in the removal of suspended solids and residual oil content in POME. Preliminary analysis shows that POME contains 40,000 mg/L suspended solid and 4,000 mg/L oil and grease content that relatively very high compared to the maximum allowable limit by the Malaysian Department of Environment which are only 400 mg/L and 50 mg/L respectively. The methods chosen were coagulation-sedimentation method for suspended solids removal and solvent extraction for residual oil removal.  Jar test apparatus was used as the standard procedure for bench-scale testing and alum was used as the coagulant. Parameters studied were alum dosage, mixing time, mixing speed, sedimentation time and pH. For removal of residual oil, six different organic solvents; n-hexane, n-heptane, benzene, petroleum ether, pentane and petroleum benzene were used. For every solvent the effect of solvent ratio, mixing time, mixing speed and pH were analyzed. The results show that the optimum conditions in removal of suspended solid from POME were at pH 4.11, sedimentation time of 100 minutes and 150 rpm mixing speed with 1.5 hr mixing time. N-hexane give the best performance in extracting residual oil from POME with solvent to POME ratio of 6:10. It was estimated about 0.54 grams of oil and grease can be extracted with optimum variables at pH 4, mixing speed of 200 rpm, and 20 minutes mixing time.  Key Words: palm oil mill effluent, coagulation, suspended solid, residual oil, solvent extraction.

  18. Sediment Deposition Risk Analysis and PLSR Model Research for Cascade Reservoirs Upstream of the Yellow River

    Directory of Open Access Journals (Sweden)

    Jie Yang

    2015-01-01

    Full Text Available It is difficult to effectively identify and eliminate the multiple correlation influence among the independent factors by least-squares regression. Focusing on this insufficiency, the sediment deposition risk of cascade reservoirs and fitting model of sediment flux into the reservoir are studied. The partial least-squares regression (PLSR method is adopted for modeling analysis; the model fitting is organically combined with the non-model-style data content analysis, so as to realize the regression model, data structure simplification, and multiple correlations analysis among factors; meanwhile the accuracy of the model is ensured through cross validity check. The modeling analysis of sediment flux into the cascade reservoirs of Long-Liu section upstream of the Yellow River indicates that partial least-squares regression can effectively overcome the multiple correlation influence among factors, and the isolated factor variables have better ability to explain the physical cause of measured results.

  19. Modeling of Brain Shift Phenomenon for Different Craniotomies and Solid Models

    Directory of Open Access Journals (Sweden)

    Alvaro Valencia

    2012-01-01

    Full Text Available This study investigates the effects of different solid models on predictions of brain shift for three craniotomies. We created a generic 3D brain model based on healthy human brain and modeled the brain parenchyma as single continuum and constrained by a practically rigid skull. We have used elastic model, hyperelastic 1st, 2nd, and 3rd Ogden models, and hyperelastic Mooney-Rivlin with 2- and 5-parameter models. A pressure on the brain surface at craniotomy region was applied to load the model. The models were solved with the finite elements package ANSYS. The predictions on stress and displacements were compared for three different craniotomies. The difference between the predictions of elastic solid model and a hyperelastic Ogden solid model of maximum brain displacement and maximum effective stress is relevant.

  20. ASSESSMENT OF THE ARTIFICIAL NEURAL NETWORKS TO GEOMORPHIC MODELLING OF SEDIMENT YIELD FOR UNGAUGED CATCHMENTS, ALGERIA

    Directory of Open Access Journals (Sweden)

    Khanchoul Kamel

    2014-01-01

    Full Text Available Knowledge of sediment yield and the factors controlling it provides useful information for estimating erosion intensities within river basins. The objective of this study was to build a model from which suspended sediment yield could be estimated from ungauged rivers using computed sediment yield and physical factors. Researchers working on suspended sediment transported by wadis in the Maghreb are usually facing the lack of available data for such river types. Further study of the prediction of sediment transport in these regions and its variability is clearly required. In this work, ANNs were built between sediment yield established from longterm measurement series at gauging stations in Algerian catchments and corresponding basic physiographic parameters such as rainfall, runoff, lithology index, coefficient of torrentiality, and basin area. The proposed Levenberg-Marquardt and Multilayer Perceptron algorithms to train the neural networks of the current research study was based on the feed-forward backpropagation method with combinations of number of neurons in each hidden layer, transfer function, error goal. Additionally, three statistical measurements, namely the root mean square error (RMSE, the coefficient of determination (R², and the efficiency factor (EF have been reported for examining the forecasting accuracy of the developed model. Single plot displays of network outputs with respect to targets for training have provided good performance results and good fitting . Thus, ANNs were a promising method for predicting suspended sediment yield in ungauged Algerian catchments.

  1. Conceptual Site Model for Newark Bay—Hydrodynamics and Sediment Transport

    Directory of Open Access Journals (Sweden)

    Parmeshwar L. Shrestha

    2014-02-01

    Full Text Available A conceptual site model (CSM has been developed for the Newark Bay Study Area (NBSA as part of the Remedial Investigation/Feasibility Study (RI/FS for this New Jersey site. The CSM is an evolving document that describes the influence of physical, chemical and biological processes on contaminant fate and transport. The CSM is initiated at the start of a project, updated during site activities, and used to inform sampling and remediation planning. This paper describes the hydrodynamic and sediment transport components of the CSM for the NBSA. Hydrodynamic processes are influenced by freshwater inflows, astronomical forcing through two tidal straits, meteorological conditions, and anthropogenic activities such as navigational dredging. Sediment dynamics are driven by hydrodynamics, waves, sediment loading from freshwater sources and the tidal straits, sediment size gradation, sediment bed properties, and particle-to-particle interactions. Cohesive sediment transport is governed by advection, dispersion, aggregation, settling, consolidation, and erosion. Noncohesive sediment transport is governed by advection, dispersion, settling, armoring, and transport in suspension and along the bed. The CSM will inform the development and application of a numerical model that accounts for all key variables to adequately describe the NBSA’s historical, current, and future physical conditions.

  2. MODELING OF TEMPERATURE FIELDS IN A SOLID HEAT ACCUMULLATORS

    Directory of Open Access Journals (Sweden)

    S. S. Belimenko

    2016-10-01

    Full Text Available Purpose. Currently, one of the priorities of energy conservation is a cost savings for heating in commercial and residential buildings by the stored thermal energy during the night and its return in the daytime. Economic effect is achieved due to the difference in tariffs for the cost of electricity in the daytime and at night. One of the most common types of devices that allow accumulating and giving the resulting heat are solid heat accumulators. The main purpose of the work: 1 software development for the calculation of the temperature field of a flat solid heat accumulator, working due to the heat energy accumulation in the volume of thermal storage material without phase transition; 2 determination the temperature distribution in its volumes at convective heat transfer. Methodology. To achieve the study objectives a heat transfer theory and Laplace integral transform were used. On its base the problems of determining the temperature fields in the channels of heat accumulators, having different cross-sectional shapes were solved. Findings. Authors have developed the method of calculation and obtained solutions for the determination of temperature fields in channels of the solid heat accumulator in conditions of convective heat transfer. Temperature fields over length and thickness of channels were investigated. Experimental studies on physical models and industrial equipment were conducted. Originality. For the first time the technique of calculating the temperature field in the channels of different cross-section for the solid heat accumulator in the charging and discharging modes was proposed. The calculation results are confirmed by experimental research. Practical value. The proposed technique is used in the design of solid heat accumulators of different power as well as full-scale production of them was organized.

  3. A user-friendly modified pore-solid fractal model

    Science.gov (United States)

    Ding, Dian-Yuan; Zhao, Ying; Feng, Hao; Si, Bing-Cheng; Hill, Robert Lee

    2016-12-01

    The primary objective of this study was to evaluate a range of calculation points on water retention curves (WRC) instead of the singularity point at air-entry suction in the pore-solid fractal (PSF) model, which additionally considered the hysteresis effect based on the PSF theory. The modified pore-solid fractal (M-PSF) model was tested using 26 soil samples from Yangling on the Loess Plateau in China and 54 soil samples from the Unsaturated Soil Hydraulic Database. The derivation results showed that the M-PSF model is user-friendly and flexible for a wide range of calculation point options. This model theoretically describes the primary differences between the soil moisture desorption and the adsorption processes by the fractal dimensions. The M-PSF model demonstrated good performance particularly at the calculation points corresponding to the suctions from 100 cm to 1000 cm. Furthermore, the M-PSF model, used the fractal dimension of the particle size distribution, exhibited an accepted performance of WRC predictions for different textured soils when the suction values were ≥100 cm. To fully understand the function of hysteresis in the PSF theory, the role of allowable and accessible pores must be examined.

  4. A Geographic Information System approach to modeling nutrient and sediment transport

    Energy Technology Data Exchange (ETDEWEB)

    Levine, D.A. [Automated Sciences Group, Inc., Oak Ridge, TN (United States); Hunsaker, C.T.; Beauchamp, J.J. [Oak Ridge National Lab., TN (United States); Timmins, S.P. [Analysas Corp., Oak Ridge, TN (United States)

    1993-02-01

    The objective of this study was to develop a water quality model to quantify nonpoint-source (NPS) pollution that uses a geographic information system (GIS) to link statistical modeling of nutrient and sediment delivery with the spatial arrangement of the parameters that drive the model. The model predicts annual nutrient and sediment loading and was developed, calibrated, and tested on 12 watersheds within the Lake Ray Roberts drainage basin in north Texas. Three physiographic regions are represented by these watersheds, and model success, as measured by the accuracy of load estimates, was compared within and across these regions.

  5. A Geographic Information System approach to modeling nutrient and sediment transport

    Energy Technology Data Exchange (ETDEWEB)

    Levine, D.A. [Automated Sciences Group, Inc., Oak Ridge, TN (United States); Hunsaker, C.T.; Beauchamp, J.J. [Oak Ridge National Lab., TN (United States); Timmins, S.P. [Analysas Corp., Oak Ridge, TN (United States)

    1993-02-01

    The objective of this study was to develop a water quality model to quantify nonpoint-source (NPS) pollution that uses a geographic information system (GIS) to link statistical modeling of nutrient and sediment delivery with the spatial arrangement of the parameters that drive the model. The model predicts annual nutrient and sediment loading and was developed, calibrated, and tested on 12 watersheds within the Lake Ray Roberts drainage basin in north Texas. Three physiographic regions are represented by these watersheds, and model success, as measured by the accuracy of load estimates, was compared within and across these regions.

  6. Sediment transport modelling based on grain size trend analysis in Augusta Harbour (Sicily)

    Science.gov (United States)

    Barbera, Giuseppe; Feo, Roberto; Freni, Gabriele

    2015-12-01

    To support marine civil engineer in pollutant studies, sediment management or dredging operations, is useful to know how the sediments move in accumulation basin. This paper investigates the dynamic of the sediment path using a two-dimensional numeric model: the Grain Size Trend Analysis (GSTA). The GSTA was applied using GiSedTrend plugin, under GIS software. The case study is the Augusta Harbour, which is one of the most polluted Italian harbours. It is the marine part of the Site of National Interest (SNI) of Priolo Gargallo (Siracusa, Italy) and it can be hydrodynamically considered as a lagoon. Two scenarios were obtained by using different geostatistical criteria.

  7. Facility for cold flow testing of solid rocket motor models

    Science.gov (United States)

    Bacchus, D. L.; Hill, O. E.; Whitesides, R. Harold

    1992-02-01

    A new cold flow test facility was designed and constructed at NASA Marshall Space Flight Center for the purpose of characterizing the flow field in the port and nozzle of solid propellant rocket motors (SRM's). A National Advisory Committee was established to include representatives from industry, government agencies, and universities to guide the establishment of design and instrumentation requirements for the new facility. This facility design includes the basic components of air storage tanks, heater, submicron filter, quiet control valve, venturi, model inlet plenum chamber, solid rocket motor (SRM) model, exhaust diffuser, and exhaust silencer. The facility was designed to accommodate a wide range of motor types and sizes from small tactical motors to large space launch boosters. This facility has the unique capability of testing ten percent scale models of large boosters such as the new Advanced Solid Rocket Motor (ASRM), at full scale motor Reynolds numbers. Previous investigators have established the validity of studying basic features of solid rocket motor development programs include the acquisition of data to (1) directly evaluate and optimize the design configuration of the propellant grain, insulation, and nozzle; and (2) provide data for validation of the computational fluid dynamics, (CFD), analysis codes and the performance analysis codes. A facility checkout model was designed, constructed, and utilized to evaluate the performance characteristics of the new facility. This model consists of a cylindrical chamber and converging/diverging nozzle with appropriate manifolding to connect it to the facility air supply. It was designed using chamber and nozzle dimensions to simulate the flow in a 10 percent scale model of the ASRM. The checkout model was recently tested over the entire range of facility flow conditions which include flow rates from 9.07 to 145 kg/sec (20 to 320 Ibm/sec) and supply pressure from 5.17 x 10 exp 5 to 8.27 x 10 exp 6 Pa. The

  8. Modelling temperature and concentration dependent solid/liquid interfacial energies

    Science.gov (United States)

    Lippmann, Stephanie; Jung, In-Ho; Paliwal, Manas; Rettenmayr, Markus

    2016-01-01

    Models for the prediction of the solid/liquid interfacial energy in pure substances and binary alloys, respectively, are reviewed and extended regarding the temperature and concentration dependence of the required thermodynamic entities. A CALPHAD-type thermodynamic database is used to introduce temperature and concentration dependent melting enthalpies and entropies for multicomponent alloys in the temperature range between liquidus and solidus. Several suitable models are extended and employed to calculate the temperature and concentration dependent interfacial energy for Al-FCC with their respective liquids and compared with experimental data.

  9. Estuarine Sediment Deposition during Wetland Restoration: A GIS and Remote Sensing Modeling Approach

    Science.gov (United States)

    Newcomer, Michelle; Kuss, Amber; Kentron, Tyler; Remar, Alex; Choksi, Vivek; Skiles, J. W.

    2011-01-01

    Restoration of the industrial salt flats in the San Francisco Bay, California is an ongoing wetland rehabilitation project. Remote sensing maps of suspended sediment concentration, and other GIS predictor variables were used to model sediment deposition within these recently restored ponds. Suspended sediment concentrations were calibrated to reflectance values from Landsat TM 5 and ASTER using three statistical techniques -- linear regression, multivariate regression, and an Artificial Neural Network (ANN), to map suspended sediment concentrations. Multivariate and ANN regressions using ASTER proved to be the most accurate methods, yielding r2 values of 0.88 and 0.87, respectively. Predictor variables such as sediment grain size and tidal frequency were used in the Marsh Sedimentation (MARSED) model for predicting deposition rates for three years. MARSED results for a fully restored pond show a root mean square deviation (RMSD) of 66.8 mm (<1) between modeled and field observations. This model was further applied to a pond breached in November 2010 and indicated that the recently breached pond will reach equilibrium levels after 60 months of tidal inundation.

  10. Sediment trapping analysis of flood control reservoirs in Upstream Ciliwung River using SWAT Model

    Science.gov (United States)

    Rofiq Ginanjar, Mirwan; Putra, Santosa Sandy

    2017-06-01

    The plans of Sukamahi dam and Ciawi dam construction for Jakarta flood risk reduction purpose had been proposed as feasible solutions to be implemented. However, the risk of the dam outlets clogging, caused by the sediment, is important to be anticipated. The prediction of the max sediment concentration in the reservoir is crucial for the dam operation planning. It is important to avoid the flood outlet tunnel clogging. This paper present a hydrologic sediment budget model of The Upstream Ciliwung River Basin, with flood control dam existence scenarios. The model was constructed within SWAT (Soil and Water Assessment Tools) plugin and run inside the QGIS framework. The free hydrological data from CFSR, soil data from FAO, and topographical data from CGIAR-CSI were implemented as the model input. The model resulted the sediment concentration dynamics of the Sukamahi and Ciawi reservoirs, on some suspended sediment parameter ranges. The sediment trapping efficiency was also computed by different possible dam capacity alternatives. The research findings will give a scientific decision making base for the river authority, in term of flood control dam planning, especially in The Upstream Ciliwung River Basin.

  11. Modeling of efficient solid-state cooler on layered multiferroics.

    Science.gov (United States)

    Starkov, Ivan; Starkov, Alexander

    2014-08-01

    We have developed theoretical foundations for the design and optimization of a solid-state cooler working through caloric and multicaloric effects. This approach is based on the careful consideration of the thermodynamics of a layered multiferroic system. The main section of the paper is devoted to the derivation and solution of the heat conduction equation for multiferroic materials. On the basis of the obtained results, we have performed the evaluation of the temperature distribution in the refrigerator under periodic external fields. A few practical examples are considered to illustrate the model. It is demonstrated that a 40-mm structure made of 20 ferroic layers is able to create a temperature difference of 25K. The presented work tries to address the whole hierarchy of physical phenomena to capture all of the essential aspects of solid-state cooling.

  12. Limitations of empirical sediment transport formulas for shallow water and their consequences for swash zone modelling

    CERN Document Server

    Li, Wei; Pähtz, Thomas; He, Zhiguo; Cao, Zhixian

    2016-01-01

    Volumetric sediment concentrations computed by phase-resolving swash morphodynamic models are shown to exceed unity minus porosity (i.e. the maximal physically possible concentration value) by up to factor of $10^5$ when using standard expressions to compute the sediment transport rate. An ad hoc limit of sediment concentration is introduced as a means to evaluate consequences of exceeding physically realistic concentration by standard expressions. We find that implementation of this ad hoc limit strongly changes the quantitative and qualitative predictions of phase-resolving swash morphodynamic models, suggesting that existing swash predictions are unreliable. This is because standard expressions inappropriately consider or ignore the fact that the shallow swash water depth limits the storage capacity of transported sediment.

  13. A model to quantify sediment mixing across alluvial piedmonts with cycles of aggradation and incision

    Science.gov (United States)

    Malatesta, Luca C.; Berger, Quentin; Avouac, Jean-Philippe

    2017-04-01

    The accurate interpretation of clastic sedimentary records hinges on a good understanding of the timescale and mode of sediment transport from source to sink. An environmental signal can be accurately recorded in the stratigraphy if it is transported quickly without being mixed with older sediments, or it can be entirely shredded by a slow transport and significant mixing along the way. Both transformations can happen in alluvial piedmonts by successive episodes of aggradation and incision. For example, in the Tian Shan the sediment flux reaching the foreland basin is mixed with sediments of up to 0.5 Ma age, mixing and blurring the environmental signals it carries. We present here a numerical model that reproduces cycles of aggradation and incision on an alluvial fan and keeps track of the age composition in the sediment outflow. The model is based on three fundamental time- and length-scales: the period of aggradation-incision cycles, the depth of incision with respect to net aggradation, and the pattern of lateral migration. All three parameters can be reasonably easily surveyed in the field and with remote sensing. For simple geometries, we replace the numerical model with a probabilistic light analytical model. The output of both models quantifies sediment mixing in terms of the probability of finding a given minimum proportion of sediments of age T or older in the output flux. We apply and test the analytical and numerical models to the Eastern Tian Shan where we can rely on independent measurements of mixing and buffering. There, rivers repeatedly aggraded and incised 100's of meters every 20 to 30 kyr with two main effects: 1) the delivery of coarse sediments to the basin is delayed by at least 7 to 14 kyrs between being first evacuated from the mountain and later re-eroded and transported basinward; 2) the outflux of coarse sediments from the piedmont contains a significant amount of recycled material that was deposited on the piedmont as early as the

  14. ECO: a generic eutrophication model including comprehensive sediment-water interaction.

    Directory of Open Access Journals (Sweden)

    Johannes G C Smits

    Full Text Available The content and calibration of the comprehensive generic 3D eutrophication model ECO for water and sediment quality is presented. Based on a computational grid for water and sediment, ECO is used as a tool for water quality management to simulate concentrations and mass fluxes of nutrients (N, P, Si, phytoplankton species, detrital organic matter, electron acceptors and related substances. ECO combines integral simulation of water and sediment quality with sediment diagenesis and closed mass balances. Its advanced process formulations for substances in the water column and the bed sediment were developed to allow for a much more dynamic calculation of the sediment-water exchange fluxes of nutrients as resulting from steep concentration gradients across the sediment-water interface than is possible with other eutrophication models. ECO is to more accurately calculate the accumulation of organic matter and nutrients in the sediment, and to allow for more accurate prediction of phytoplankton biomass and water quality in response to mitigative measures such as nutrient load reduction. ECO was calibrated for shallow Lake Veluwe (The Netherlands. Due to restoration measures this lake underwent a transition from hypertrophic conditions to moderately eutrophic conditions, leading to the extensive colonization by submerged macrophytes. ECO reproduces observed water quality well for the transition period of ten years. The values of its process coefficients are in line with ranges derived from literature. ECO's calculation results underline the importance of redox processes and phosphate speciation for the nutrient return fluxes. Among other things, the results suggest that authigenic formation of a stable apatite-like mineral in the sediment can contribute significantly to oligotrophication of a lake after a phosphorus load reduction.

  15. ECO: a generic eutrophication model including comprehensive sediment-water interaction.

    Science.gov (United States)

    Smits, Johannes G C; van Beek, Jan K L

    2013-01-01

    The content and calibration of the comprehensive generic 3D eutrophication model ECO for water and sediment quality is presented. Based on a computational grid for water and sediment, ECO is used as a tool for water quality management to simulate concentrations and mass fluxes of nutrients (N, P, Si), phytoplankton species, detrital organic matter, electron acceptors and related substances. ECO combines integral simulation of water and sediment quality with sediment diagenesis and closed mass balances. Its advanced process formulations for substances in the water column and the bed sediment were developed to allow for a much more dynamic calculation of the sediment-water exchange fluxes of nutrients as resulting from steep concentration gradients across the sediment-water interface than is possible with other eutrophication models. ECO is to more accurately calculate the accumulation of organic matter and nutrients in the sediment, and to allow for more accurate prediction of phytoplankton biomass and water quality in response to mitigative measures such as nutrient load reduction. ECO was calibrated for shallow Lake Veluwe (The Netherlands). Due to restoration measures this lake underwent a transition from hypertrophic conditions to moderately eutrophic conditions, leading to the extensive colonization by submerged macrophytes. ECO reproduces observed water quality well for the transition period of ten years. The values of its process coefficients are in line with ranges derived from literature. ECO's calculation results underline the importance of redox processes and phosphate speciation for the nutrient return fluxes. Among other things, the results suggest that authigenic formation of a stable apatite-like mineral in the sediment can contribute significantly to oligotrophication of a lake after a phosphorus load reduction.

  16. Dynamic response of deep-sea sediments to seasonal variations: a model

    OpenAIRE

    Soetaert, K.; Herman, P.M.J.; Middelburg, J. J.

    1996-01-01

    We present a dynamic, numerical model of early diagenetic processes that can be used to examine the response of different organic carbon mineralization pathways, concentration vs. depth profiles, and the resultant fluxes to seasonally varying carbon deposition. We show that there can be substantial temporal variability in sediment-water fluxes as well as in the relative contribution of different organic carbon mineralization pathways and oxygen consumption processes in deep-sea sediments. The...

  17. Flocculation, Optics and Turbulence in the Community Sediment Transport Model System: Application of Oasis Results

    Science.gov (United States)

    2012-09-30

    1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Flocculation , Optics and Turbulence in the Community...www.phys.ocean.dal.ca/~phill LONG-TERM GOALS The goal of this research is to develop greater understanding of how the flocculation of fine-grained sediment...COVERED - 4. TITLE AND SUBTITLE Flocculation , Optics and Turbulence in the Community Sediment Transport Model System: Application of Oasis

  18. Generic 2-D River Network Modeling of Flow and Sediment Transports

    Science.gov (United States)

    Guo, W.; Wang, C.; Xiang, X.; Ma, T.

    2012-04-01

    A generic 2D river network model of flow and sediment transports is proposed for the flow and sediment simulation in the complex river network. The paper expands the three-step method adopted in the 1D river network to the 2D river network simulation. A 2D river network model is divided into several cells, including single river cell, "tree-like" river cell, "ring-like" river cell and "cross-like" river cell, which can reflect the interactive influence of flow field in the bifurcated channel and applies to generic 2D simulation. Based on equation of the 2D shallow water and unsteady non-uniform suspended sediment, the relationship between the variables (water level, discharge and sediment concentration) of each section and those of the boundaries are obtained through the full implicit matrix chase-after method. Through the conservation of water and sediment on the boundaries, the water level and sediment concentration on the nodes can be got by solving the irregular sparse matrix of conservation equation, so as to implement the coupled simulation of flow and sediment in the whole river network. The paper take the Chengtong River Reach located in the low reaches of Yangtze River as the example of "cross-like" river to verify the algorithm. The model is calibrated using the measured data. A comparison of calculated water level, discharge and sediment concentration shows that the generic model can reflex the interactive influence of flow field, with reasonable accuracy, especially in the bifurcated channel.

  19. A Multiphase First Order Model for Non-Equilibrium Sand Erosion, Transport and Sedimentation

    CERN Document Server

    Preziosi, Luigi; Bruno, Luca

    2015-01-01

    Three phenomena are involved in sand movement: erosion, wind transport, and sedimentation. This paper presents a comprehensive easy-to-use multiphase model that include all three aspects with a particular attention to situations in which erosion due to wind shear and sedimentation due to gravity are not in equilibrium. The interest is related to the fact that these are the situations leading to a change of profile of the sand bed.

  20. MODELING OF THE HIGH CONCENTRATION LAYER OF COHESIVE SEDIMENT UNDER THE ACTION OF WAVES AND CURRENTS

    Institute of Scientific and Technical Information of China (English)

    Qinghe ZHANG; Yongsheng WU; Jijian LIAN; Pingxing DING

    2001-01-01

    High concentration layer of cohesive sediment frequently occurs in muddy estuaries and coastal zones, and causes rapid siltation of the waterways. A one dimensional vertical coupled model describing the interactions between waves, currents and suspended cohesive sediment is developed in the present paper. The numerical results and analyses with field measurements reveal the mechanism of the formation and transport behaviors of the layer under the action of waves and currents.

  1. Comparison of empirical models to estimate soil erosion and sediment yield in micro catchments

    Directory of Open Access Journals (Sweden)

    Lida Eisazadeh

    2015-05-01

    Full Text Available Assessment of sediment yield in soil conservation and watershed Project and implementation plan for water and soil resources management is so important. Regarding to somewhere that doesn’t have enough information and statistical data such as upper river branches, Empirical models should be used to estimate erosion and sediment yield. However the efficiency and usage of these models before calibration isn’t clear. In this research, the measurement of erosion and sediment yield of 10 basins upstream of reservoirshas been estimated by RUSLE and MPSIAC empirical models.In order to compare means between measured and estimated datat-test method was applied.Theresults indicated no significant differences between means of measured and estimated sediment yield in MPSAIC model in 5% level. In contrast, T-test showed contrary results in RUSLE model. Then the applicability and priority of two models were examined by statistical methodssuch as MAE and MBE methods. By regarding to accuracy and precision, MPSIAC model placed in first priorityto estimate soil erosion and sediment yield and has minimum value of MAE=0.79 and MBE = -0.59.

  2. Description of adsorption of hydrophobic organic compounds on sediment using multi-component adsorption model

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A chemical sequential separation procedure for sediment bas been developed for the adsorptive investigation of hydrophobic organic compounds(HOCs) including four fractions: carbonate, hydrous metallic oxide(ferric oxide, manganese oxide and alumina), clay and organic matter. Adsorption isotherms of these hydrophobic solute probes, such as hexachloroethane, lindane and 1,2,4,5-tetrachlorobenzene were measured for model sorbents, model and natural sediment, and the latter of which was pretreated with the simplified sequential separation method. The linear and Langmuir models are applied to correlate the experimental data of humic substance and other model sorbents respectively. Multi-component Adsorptive Model (MCAM) was used to simulate adsorption isotherms of model and natural sediment. The results reveal that( 1 ) the separation efficiencies of carbonate, organic matter, ferric oxide, manganese oxide and alumina are 98. 1 % , 72.5% ,82.6%, 93.5% and 83.3%, respectively; (2) except for removing metallic oxide, the external structure of sediment is not changed greatly after separation; (3) the MCAM correlates the data of adsorption isotherm rather well with the maximal relative deviations of 9.76 % , 6.78 %and 9.53% for hexachloroethane, lindane and 1,2,4,5-tetrachlorobenaze in model sediment, respectively. The MCAM can clearly give expression to the different adsorptive mechanisms for HOCs in organic and inorganic matter, though the experimental data in each component are not very accurate due to the sequential separation efficiency.

  3. Well-balanced numerical modelling of non-uniform sediment transport in alluvial rivers

    Institute of Scientific and Technical Information of China (English)

    Honglu Qian; Zhixian Cao; Gareth Pender; Huaihan Liu; Peng Hu

    2015-01-01

    abstract The last two decades have witnessed the development and application of well-balanced numerical models for shallow flows in natural rivers. However, until now there have been no such models for flows with non-uniform sediment transport. This paper presents a 1D well-balanced model to simulate flows and non-capacity transport of non-uniform sediment in alluvial rivers. The active layer formulation is adopted to resolve the change of bed sediment composition. In the framework of the finite volume Slope LImiter Centred (SLIC) scheme, a surface gradient method is incorporated to attain well-balanced solutions to the governing equations. The proposed model is tested against typical cases with irregular topography, including the refilling of dredged trenches, aggradation due to sediment overloading and flood flow due to landslide dam failure. The agreement between the computed results and measured data is encouraging. Compared to a non-well-balanced model, the well-balanced model features improved performance in reproducing stage, velocity and bed deformation. It should find general applications for non-uniform sediment transport modelling in alluvial rivers, especially in mountain areas where the bed topography is mostly irregular.

  4. SSM - SOLID SURFACE MODELER, VERSION 6.0

    Science.gov (United States)

    Goza, S. P.

    1994-01-01

    The Solid Surface Modeler (SSM) is an interactive graphics software application for solid-shaded and wireframe three- dimensional geometric modeling. It enables the user to construct models of real-world objects as simple as boxes or as complex as Space Station Freedom. The program has a versatile user interface that, in many cases, allows mouse input for intuitive operation or keyboard input when accuracy is critical. SSM can be used as a stand-alone model generation and display program and offers high-fidelity still image rendering. Models created in SSM can also be loaded into other software for animation or engineering simulation. (See the information below for the availability of SSM with the Object Orientation Manipulator program, OOM, a graphics software application for three-dimensional rendering and animation.) Models are constructed within SSM using functions of the Create Menu to create, combine, and manipulate basic geometric building blocks called primitives. Among the simpler primitives are boxes, spheres, ellipsoids, cylinders, and plates; among the more complex primitives are tubes, skinned-surface models and surfaces of revolution. SSM also provides several methods for duplicating models. Constructive Solid Geometry (CSG) is one of the most powerful model manipulation tools provided by SSM. The CSG operations implemented in SSM are union, subtraction and intersection. SSM allows the user to transform primitives with respect to each axis, transform the camera (the user's viewpoint) about its origin, apply texture maps and bump maps to model surfaces, and define color properties; to select and combine surface-fill attributes, including wireframe, constant, and smooth; and to specify models' points of origin (the positions about which they rotate). SSM uses Euler angle transformations for calculating the results of translation and rotation operations. The user has complete control over the modeling environment from within the system. A variety of file

  5. Evaluation of stream water quality data generated from MODIS images in modeling total suspended solid emission to a freshwater lake.

    Science.gov (United States)

    Ayana, Essayas K; Worqlul, Abeyou W; Steenhuis, Tammo S

    2015-08-01

    Modeling of suspended sediment emission into freshwater lakes is challenging due to data gaps in developing countries. Existing models simulate sediment concentration at a gauging station upstream and none of these studies had modeled total suspended solids (TSS) emissions by inflowing rivers to freshwater lakes as there are no TSS measurements at the river mouth in the upper Blue Nile basin. In this study a 10year TSS time series data generated from remotely sensed MODIS/Terra images using established empirical relationship is applied to calibrate and validate a hydrology model for Lake Tana in Upper Blue Nile Basin. The result showed that at a monthly time scale TSS at the river mouth can be replicated with Nash-Sutcliffe efficiency (NS) of 0.34 for calibration and 0.21 for validation periods. Percent bias (PBIAS) and ratio of the root-mean-square error to the standard deviation of measured data (RSR) are all within range. Given the inaccessibility and costliness to measure TSS at river mouths to a lake the results found here are considered useful for suspended sediment budget studies in water bodies of the basin. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Estimating reservoir sedimentation using bathymetric differencing and hydrologic modeling in data scarce Koga watershed, Upper Blue Nile

    Directory of Open Access Journals (Sweden)

    Demesew Alemaw Mhiret

    2016-12-01

    Full Text Available ABSTRACT Modeling sediment accumulation in constructed reservoirs is hampered by lack of historic sediment concentration data in developing countries. Existing models simulate sediment concentration using data generated from sediment rating curves usually defined as a power function of the form S = aQb This often results in residual errors that are not identically distributed throughout the range of stream flow values adding to uncertainty in sediment modeling practices. This research measure accumulated sediment in Koga dam in the upper Blue Nile Basin and use the result to validate a Soil and Water Assessment Tool (SWAT sediment model that uses sediment data from rating curves. Bathymetric differencing of the original and current storage digital elevation models (DEMs indicate that the sediment was accumulating at a rate of 5 ton/ha/year while a calibrated SWAT model resulted in 8.6 ton/ha/year. Given the complicated sediment transport processes that are not fully understood and comparable rates reported in recent studies these results are satisfactory. Keywords: Reservoir sedimentation, Koga reservoir, bathymetry

  7. An environmental fate study of methoxychlor using water-sediment model system.

    Science.gov (United States)

    Masuda, Minoru; Satsuma, Koji; Sato, Kiyoshi

    2012-01-01

    Agricultural waste water containing pesticides can reach the sea via rivers and estuaries, including brackish lakes. We studied the metabolic fate of methoxychlor [MXC; 1,1,1-trichloro-2,2-bis(4-methoxyphenyl)ethane] in a model system consisting of sediment and associated water collected from two sampling sites: a brackish lake and a freshwater river. MXC degraded rapidly and was finally mineralized in both sediment systems. The first step of degradation was dechlorination to yield 1,1-dichloro-2,2-bis(4-methoxyphenyl)ethane [de-Cl-MXC] or CN-replacement to yield 2,2-bis(4-methoxyphenyl)acetonitrile [MXC-CN], followed by O-demethylation. Although the metabolites were common to the two sediments, the dynamics of the metabolites over time were clearly distinct. In the brackish lake sediment, de-Cl-MXC accumulated transiently, whereas in the river sediment, it was rapidly converted to its demethylated metabolite. We also found that dechlorination and CN-replacement proceeded in autoclave-sterilized river sediment. In the river sediment, the abiotic reaction mediated by abundant humic acid and low oxygen level also appeared to contribute to the overall MXC metabolism.

  8. Statistical modelling of variability in sediment-water nutrient and oxygen fluxes

    Science.gov (United States)

    Serpetti, Natalia; Witte, Ursula; Heath, Michael

    2016-06-01

    Organic detritus entering, or produced, in the marine environment is re-mineralised to inorganic nutrient in the seafloor sediments. The flux of dissolved inorganic nutrient between the sediment and overlying water column is a key process in the marine ecosystem, which binds the biogeochemical sub-system to the living food web. These fluxes are potentially affected by a wide range of physical and biological factors and disentangling these is a significant challenge. Here we develop a set of General Additive Models (GAM) of nitrate, nitrite, ammonia, phosphate, silicate and oxygen fluxes, based on a year-long campaign of field measurements off the north-east coast of Scotland. We show that sediment grain size, turbidity due to sediment re-suspension, temperature, and biogenic matter content were the key factors affecting oxygen consumption, ammonia and silicate fluxes. However, phosphate fluxes were only related to suspended sediment concentrations, whilst nitrate fluxes showed no clear relationship to any of the expected drivers of change, probably due to the effects of denitrification. Our analyses show that the stoichiometry of nutrient regeneration in the ecosystem is not necessarily constant and may be affected by combinations of processes. We anticipate that our statistical modelling results will form the basis for testing the functionality of process-based mathematical models of whole-sediment biogeochemistry.

  9. Remote sensing and numerical modeling of suspended sediment in Laguna de Terminos, Campeche, Mexico

    Science.gov (United States)

    Jensen, John R.; Kjerfve, Bjorn; Ramsey, Elijah W., III; Magill, Karen E.; Medeiros, Carmen

    1989-01-01

    It is necessary to understand the complex physical processes at work in coastal lagoons in order to manage them effectively. Improved methods of data collection and analysis must be found to provide synoptic, timely hydrodynamic information because of the sheer size of some lagoons and the difficulty of acquiring in situ data (particularly in the tropics). This paper summarizes research to model salinity and suspended sediment distributions in Laguna de Terminos, Mexico, using (1) a coupled hydrodynamic and dispersion model and (2) analysis of two Landsat Thematic Mapper images collected on November 25, 1984 and April 24, 1987. Atmospherically corrected chromaticity data derived from Thermatic Mapper data were significantly correlated with modeled total suspended sediment concentrations for the two dates. Comparison between numerically modeled and remotely sensed suspended sediment maps at 1.5 x 1.5 km resolution yielded a covariation map useful for identifying areas of discrepancy between the remotely sensed data and model output.

  10. LG Solid Oxide Fuel Cell (SOFC) Model Development

    Energy Technology Data Exchange (ETDEWEB)

    Haberman, Ben [LG Fuel Cell Systems Inc., North Canton, OH (United States); Martinez-Baca, Carlos [LG Fuel Cell Systems Inc., North Canton, OH (United States); Rush, Greg [LG Fuel Cell Systems Inc., North Canton, OH (United States)

    2013-05-31

    This report presents a summary of the work performed by LG Fuel Cell Systems Inc. during the project LG Solid Oxide Fuel Cell (SOFC) Model Development (DOE Award Number: DE-FE0000773) which commenced on October 1, 2009 and was completed on March 31, 2013. The aim of this project is for LG Fuel Cell Systems Inc. (formerly known as Rolls-Royce Fuel Cell Systems (US) Inc.) (LGFCS) to develop a multi-physics solid oxide fuel cell (SOFC) computer code (MPC) for performance calculations of the LGFCS fuel cell structure to support fuel cell product design and development. A summary of the initial stages of the project is provided which describes the MPC requirements that were developed and the selection of a candidate code, STAR-CCM+ (CD-adapco). This is followed by a detailed description of the subsequent work program including code enhancement and model verification and validation activities. Details of the code enhancements that were implemented to facilitate MPC SOFC simulations are provided along with a description of the models that were built using the MPC and validated against experimental data. The modeling work described in this report represents a level of calculation detail that has not been previously available within LGFCS.

  11. Modeling of sediment and heavy metal transport in Taihu Lake, China

    Institute of Scientific and Technical Information of China (English)

    WANG Chao; SHEN Chao; WANG Pei-fang; QIAN Jin; HOU Jun; LIU Jia-jia

    2013-01-01

    With the current rapid economic growth,heavy metal pollution has become one of the key issues in the Taihu Lake.Although heavy metal pollution levels and distributions of the Taihu Lake have previously been described,an effective model to describe the transport process of heavy metals between the water column and sediment bed for this lake is not available.It is known that heavy metals in the water column can be related to the resuspension of sediment in the lake bed.In this study,we set up a coupled model of relating hydrodynamics,sediment and heavy metals based on Environmental Fluid Dynamics Code (EFDC),and applied it to Taihu Lake,China.For calibration and validation of the model,we employed two series of field sampling data taken all over Taihu Lake during April and July of 2009.The results show that the hydrodynamics simulations of the coupled model agree with the observations reasonably well and the sediment and heavy metal model shows similar variation trends during the simulation.Our results indicate that the model can be used for simulating the sediment and heavy metal transport process in the Taihu Lake and here we provide an effective tool for water quality management at small time scales.

  12. Soil erosion and sediment connectivity modelling in Burgundy vineyards: case study of Mercurey, France

    Science.gov (United States)

    Fressard, Mathieu; Cossart, Étienne; Lejot, Jêrome; Michel, Kristell; Perret, Franck; Christol, Aurélien; Mathian, Hélène; Navratil, Oldrich

    2017-04-01

    This research aims at assessing the impact of agricultural landscape structure on soil erosion and sediment connectivity at the catchment scale. The investigations were conducted the vineyards of Mercurey (Burgundy, France), characterized by important issues related to soil loss, flash floods and associated management infrastructures maintenance. The methodology is based on two main steps that include (1) field investigations and (2) modelling. The field investigations consists in DEM acquisition by LiDAR imaging from a drone, soil mapping and human infrastructures impacting runoff classification and mapping (such as crop rows, storm water-basins, drainage network, roads, etc.). These data aims at supplying the models with field observations. The modelling strategy is based on two main steps: First, the modelling of soil sensitivity to erosion, using the spatial application of the RUSLE equation. Secondly, to assess the sediment connectivity in this area, a model based on graph theory developed by Cossart and Fressard (2017) is tested. The results allow defining the influence of different anthropogenic structures on the sediment connectivity and soil erosion at the basin scale. A set of sub-basins influenced by various anthropogenic infrastructures have been identified and show contrasted sensitivities to erosion. The modelling of sediment connectivity show that the runoff pattern is strongly influenced by the vine rows orientation and the drainage network. I has also permitted to identify non collected (by storm water-basins) areas that strongly contribute to the turbid floods sediment supply and to soil loss during high intensity precipitations events.

  13. A spatially explicit suspended-sediment load model for western Oregon

    Science.gov (United States)

    Wise, Daniel R.; O'Connor, Jim

    2016-06-27

    We calibrated the watershed model SPARROW (Spatially Referenced Regressions on Watershed attributes) to give estimates of suspended-sediment loads for western Oregon and parts of northwestern California. Estimates of suspended-sediment loads were derived from a nonlinear least squares regression that related explanatory variables representing landscape and transport conditions to measured suspended-sediment loads at 68 measurement stations. The model gives estimates of model coefficients and their uncertainty within a spatial framework defined by the National Hydrography Dataset Plus hydrologic network. The resulting model explained 64 percent of the variability in suspended-sediment yield and had a root mean squared error value of 0.737. The predictor variables selected for the final model were (1) generalized lithologic province, (2) mean annual precipitation, and (3) burned area (by recent wildfire). Other landscape characteristics also were considered, but they were not significant predictors of sediment transport, were strongly correlated with another predictor variable, or were not as significant as the predictors selected for the final model.

  14. Hillslope sediment and soil carbon transport: can we model their movement?

    Science.gov (United States)

    Hancock, Greg; Kunkel, Veikko; Dever, Chris; Braggins, Matthew; Willgoose, Garry

    2016-04-01

    Quantifying and predicting the movement of hillslope sediment and soil organic carbon (SOC) is of huge scientific, agronomic and economic benefit. In particular, the movement and fate of SOC has attracted considerable recent attention. However, the reliable modelling and prediction of sediment and SOC movement has proved elusive. Here we examine the movement of sediment and SOC along a grazing hillslope in south-eastern Australia. The slope is linear, uniformly managed and has consistent vegetation (grassland). We quantify sediment and SOC transport using the environmental tracer 137-Ceasium. However, here we collect field samples using the conventional soil cores but also shallow samples to quantify the dynamics of the near surface. We also model the movement of sediment and SOC using a numerically based soil erosion and landscape evolution model. Our results show that the hillslope is erosional which is supported by field observation. However, there was no relationship between SOC and 137-Caesium suggesting that SOC and their movement and fate are not related. Significant relationships were observed between soil texture and SOC for the near surface but not for the deeper cores suggesting any movement and fate of SOC is more controlled by soil particle size at the near surface. The SIBERIA sediment transport model was calibrated and run for the site. Comparing the field derived erosion and SOC data with model prediction found no significant relationship. However, the numerical model was able to predict the cyclic pattern of 137-Ceasium and SOC as well as overall trends. Our findings demonstrate that the movement and fate of sediment and SOC is complex.

  15. A Photochemical Kinetic Model for Solid Dosage Forms.

    Science.gov (United States)

    Carvalho, Thiago C; La Cruz, Thomas E; Tabora, Jose E

    2017-08-20

    Photochemical kinetics models for pharmaceutical compounds in solution have been extensively investigated, but not in solid phase upon exposure to different light sources. The objective of this study was to develop a mathematical model to describe the solid state photodegradation of pharmaceutical powder materials under different area/volumetric scales and light exposure conditions. The model considered the previous formalism presented for photodegradation kinetics in solution phase with important elements applied to static powder material being irradiated with a polychromatic light source. The model also included the influence of optical phenomena (i.e. reflectance, scattering factors, etc.) by applying Beer-Lambert law to light attenuation, including effects of powder density. Drug substance and drug product intermediates (blends and tablet cores) were exposed to different light sources and intensities. The model reasonably predicted the photodegradation levels of powder beds of drug substance and drug product intermediates under white and yellow lights with intensities around 5 to 11 kLux. Importantly, the model estimates demonstrated that the reciprocity law for photoreactions was held. Further model evaluation showed that, due to light attenuation, the powder bed is in virtual darkness at cake depths greater than 500 μm. At 100 μm, the photodegradation of the investigated compound is expected to be close to 100% in 10 days under white fluorescent halophosphate light at 9.5 kLux. For tablets, defining the volume over exposed surface area ratio is more challenging. Nevertheless, the model can consider a bracket between worst and best cases to provide a reasonable photodegradation estimate. This tool can be significantly leveraged to simulate different light exposure scenarios while assessing photostability risk in order to define appropriate Control Strategy in manufacturing. Copyright © 2017. Published by Elsevier B.V.

  16. Modeling 3D soil and sediment distributions for assessing catchment structure and hydrological feedbacks

    Science.gov (United States)

    Maurer, Thomas; Brück, Yasemine; Hinz, Christoph; Gerke, Horst H.

    2015-04-01

    Structural heterogeneity, namely the spatial distribution of soils and sediments (represented by mineral particles), characterizes catchment hydrological behavior. In natural catchments, local geology and the specific geomorphic processes determine the characteristics and spatial distribution of structures. In constructed catchments, structural features are determined primarily by the construction processes and the geological origin of the parent material. Objectives are scenarios of 3D catchment structures in form of complete 3D description of soil hydraulic properties generated from the knowledge of the formation processes. The constructed hydrological catchment 'Hühnerwasser' (Lower Lusatia, Brandenburg, Germany) was used for the calibration and validation of model results due to its well-known conditions. For the modelling of structural features, a structure generator was used to model i) quasi-deterministic sediment distributions using input data from a geological model of the parent material excavation site; ii) sediment distributions that are conditioned to measurement data from soil sampling; and iii) stochastic component sediment distributions. All three approaches allow a randomization within definable limits. Furthermore, the spoil cone / spoil ridge orientation, internal layering, surface compaction and internal spoil cone compaction were modified. These generated structural models were incorporated in a gridded 3D volume model constructed with the GOCAD software. For selected scenarios, the impact of structure variation was assessed by hydrological modelling with HYDRUS 2D/3D software. For that purpose, 3D distributions of soil hydraulic properties were estimated based on generated sediment properties using adapted pedotransfer functions. Results from the hydrological model were compared them to measured discharges from the catchment. The impact of structural feature variation on flow behaviour was analysed by comparing different simulation scenarios

  17. Inferring tidal wetland stability from channel sediment fluxes: observations and a conceptual model

    Science.gov (United States)

    Ganju, Neil K.; Nidzieko, Nicholas J.; Kirwan, Matthew L.

    2013-01-01

    Anthropogenic and climatic forces have modified the geomorphology of tidal wetlands over a range of timescales. Changes in land use, sediment supply, river flow, storminess, and sea level alter the layout of tidal channels, intertidal flats, and marsh plains; these elements define wetland complexes. Diagnostically, measurements of net sediment fluxes through tidal channels are high-temporal resolution, spatially integrated quantities that indicate (1) whether a complex is stable over seasonal timescales and (2) what mechanisms are leading to that state. We estimated sediment fluxes through tidal channels draining wetland complexes on the Blackwater and Transquaking Rivers, Maryland, USA. While the Blackwater complex has experienced decades of degradation and been largely converted to open water, the Transquaking complex has persisted as an expansive, vegetated marsh. The measured net export at the Blackwater complex (1.0 kg/s or 0.56 kg/m2/yr over the landward marsh area) was caused by northwesterly winds, which exported water and sediment on the subtidal timescale; tidally forced net fluxes were weak and precluded landward transport of suspended sediment from potential seaward sources. Though wind forcing also exported sediment at the Transquaking complex, strong tidal forcing and proximity to a turbidity maximum led to an import of sediment (0.031 kg/s or 0.70 kg/m2/yr). This resulted in a spatially averaged accretion of 3.9 mm/yr, equaling the regional relative sea level rise. Our results suggest that in areas where seaward sediment supply is dominant, seaward wetlands may be more capable of withstanding sea level rise over the short term than landward wetlands. We propose a conceptual model to determine a complex's tendency toward stability or instability based on sediment source, wetland channel location, and transport mechanisms. Wetlands with a reliable portfolio of sources and transport mechanisms appear better suited to offset natural and

  18. Sediment distribution modeling for evaluating the impact of initial structure on catchment hydrological behaviour

    Science.gov (United States)

    Maurer, T. J.; Gerke, H. H.; Hinz, C.

    2015-12-01

    Structural heterogeneity, namely the spatial distribution of soils and sediments (represented by mineral particles), characterizes catchment hydrological behavior. In natural catchments, local geology and the specific geomorphic processes determine the characteristics and spatial distribution of structures. In constructed catchments, structural features are determined primarily by the construction processes and the geological origin of the parent material. Objectives are scenarios of 3D catchment structures in form of complete 3D description of soil hydraulic properties generated from the knowledge of the formation processes. The constructed hydrological catchment 'Hühnerwasser' (Lower Lusatia, Brandenburg, Germany) was used for the calibration and validation of model results due to its well-known conditions. For the modeling of structural features, a structure generator was used to model i) quasi-deterministic sediment distributions using input data from a geological model of the parent material excavation site; ii) sediment distributions that are conditioned to measurement data from soil sampling; and iii) stochastic component sediment distributions. All three approaches allow a randomization within definable limits. Furthermore, the spoil cone / spoil ridge orientation, internal layering, surface compaction and internal spoil cone compaction were modified. These generated structural models were incorporated in a gridded 3D volume model constructed with the GOCAD software. The impact of structure variation was assessed by hydrological modeling with HYDRUS 2D/3D software. 3D distributions of soil hydraulic properties were estimated based on generated sediment properties using adapted pedotransfer functions. Results were compared with hydrological monitoring data. The impact of structural feature variation on hydrological behavior was analyzed by comparing different simulation scenarios. The established initial sediment distributions provide a basis for the

  19. Dynamic hydraulic models to study sedimentation in drinking water networks in detail

    Directory of Open Access Journals (Sweden)

    I. W. M. Pothof

    2012-12-01

    Full Text Available Sedimentation in drinking water networks can lead to discolouration complaints. A sufficient criterion to prevent sedimentation in the Dutch drinking water networks is a daily maximum velocity of 0.25 m s−1. Flushing experiments have shown that this criterion is a sufficient condition for a clean network, but not a necessary condition. Drinking water networks include many locations with a maximum velocity well below 0.25 m s−1 without accumulated sediments. Other criteria need to be developed to predict which locations are susceptible to sedimentation and to prevent sedimentation in future networks. More distinctive criteria are helpful to prioritise flushing operations and to prevent water quality complaints.

    The authors use three different numerical modelling approaches – quasi-steady, rigid column and water hammer – with a temporal discretisation of 1 s in order to assess the influence of unsteady flows on the wall shear stress, causing resuspension of sediment particles. The model predictions are combined with results from flushing experiments in the drinking water distribution system of Purmerend, the Netherlands. The waterhammer model does not result in essentially different flow distribution patterns, compared to the rigid column and quasi-steady modelling approach. The extra information from the waterhammer model is a velocity oscillation of approximately 0.02 m s−1 around the quasi-steady solution. The presence of stagnation zones and multiple flow direction reversals seem to be interesting new parameters to predict sediment accumulation, which are consistent with the observed turbidity data and theoretical considerations on critical shear stresses.

  20. Dynamic hydraulic models to study sedimentation in drinking water networks in detail

    Directory of Open Access Journals (Sweden)

    I. W. M. Pothof

    2012-04-01

    Full Text Available Sedimentation in drinking water networks can lead to discolouration complaints. A sufficient criterion to prevent sedimentation in drinking water networks is a daily maximum velocity of 0.25 m s−1. Flushing experiments have shown that this criterion is a sufficient condition for a clean network, but not a necessary condition. Drinking water networks include many locations with a maximum velocity well below 0.25 m s−1 without sediment. Other criteria need to be developed to predict which locations are susceptible to sedimentation and to prevent sedimentation in future networks. More distinctive criteria are helpful to prioritise flushing operations and to prevent water quality complaints.

    The authors use three different numerical modelling approaches – quasi-steady, rigid column and water hammer – with a temporal discretisation of 1 s in order to assess the influence of unsteady flows on the wall shear stress, causing resuspension of sediment particles. The model predictions are combined with results from flushing experiments in the drinking water distribution system of Purmerend, the Netherlands. The waterhammer model does not result in essentially different flow distribution patterns, compared to the rigid column and quasi-steady modelling approach. The extra information from the waterhammer model is a velocity oscillation of approximately 0.02 m s−1 around the quasi-steady solution. The presence of stagnation zones and multiple flow direction reversals seem to be interesting new parameters to predict sediment accumulation, which are consistent with the observed turbidity data and theoretical considerations on critical shear stresses.

  1. Numerical modeling of subglacial erosion and sediment transport beneath the Laurentide Ice Sheet

    Science.gov (United States)

    Melanson, A.; Bell, T.; Tarasov, L.

    2012-04-01

    Present-day sediment distribution offers a potentially strong constraint on past ice sheet evolution. However, glacial system models (GSMs) cannot address this while lacking physically-based representations of subglacial sediment generation and transport. Incorporation of these elements in GSMs is also required in order to understand the impact of changing sediment cover on glacial cycle dynamics. Towards this goal, we present a subglacial process model that incorporates mechanisms for sediment production, entrainment, transport, and deposition. An abrasion law based on Hallet's model and a quarrying law dependent on basal water pressure and bed roughness are used to calculate bedrock erosion. The incorporation of loose debris in the basal ice is modeled by regelation intrusion and basal freeze-on, depending on the thermal condition and the availability of water at the base. The entrained debris is subsequently transported along the ice sheet's internal velocity field and vertically mixed through a diffusion equation that accounts for folding and thrust faulting. The inclusion of vertical mixing lowers the basal debris concentration and allows more regelation entrainment. Soft bed deformation is included as an advective component within the subglacial sediment, the rheology of which is assumed to be weakly non-linear. Deposition occurs whenever the basal ice is debris-laden and the melting rate exceeds the entrainment rate. The model is coupled to the MUN 3D GSM, which includes a newly developed subglacial hydrology module. The GSM itself has been subject to Bayesian calibration for North American and Eurasian deglaciation and thus a probabilistic ensemble of deglacial chronologies is available. With this calibrated ensemble, we compare the range of calculated sediment thickness fields and cumulative erosion over the last glacial cycle against the present-day pattern of glacigenic sediment and the geological estimates of glacial erosion over North America

  2. Towards a Holistic Model for Simulating Sediment Dynamics at Watershed Scales: Partitioning of Sediment Sources and Uncertainty Quantification

    Science.gov (United States)

    Abban, Benjamin; Papanicolaou, Thanos; Cowles, Kate; Wilson, Christopher; Abaci, Ozan; Wacha, Kenneth

    2016-04-01

    The challenge remains to understand watershed sediment source dynamics for planning and evaluating mitigation measures on anthropogenic activities such as intensive agriculture, which exacerbates soil erosion from the landscape. To this end, our research aims to develop a cross-scale model, capable of simulating sediment transport from the plot scale to the watershed scale while effectively capturing the important feedback effects across the scales. Our approach combines numerical modeling with physical observations and measurements to not only provide a tool capable of mimicking cause and effect relationships, but also capable of quantifying uncertainty related to source dynamics predictions. We present herein a key component of the cross-scale model that quantifies source partitioning and the associated uncertainty. This component is based on a Bayesian un-mixing framework and is particularly useful for watersheds characterized by considerable spatiotemporal heterogeneity. The Bayesian un-mixing framework utilizes two key parameters, namely α and β, that explicitly accounts for spatial origin attributes and the time history of sediments delivered to the watershed outlet, respectively. These parameters are treated probabilistically so as to account for variability in source erosion processes, as well as the delivery times and storage of eroded material within the watershed. The use of Markov Chain Monte Carlo simulations for determining posterior probability density functions in the framework allows uncertainty in source contribution estimates to be quantified naturally as part of the solution process. We demonstrate the utility of the Bayesian un-mixing framework in a predominantly agricultural watershed in the US Midwest known as the Clear Creek Watershed, IA, which is part of the Critical Zone Observatory for Intensively Managed Landscapes (IML-CZO). Stable isotopes of Carbon and Nitrogen are used as tracers since they have been found to be appropriate for

  3. A Multistep Chaotic Model for Municipal Solid Waste Generation Prediction.

    Science.gov (United States)

    Song, Jingwei; He, Jiaying

    2014-08-01

    In this study, a univariate local chaotic model is proposed to make one-step and multistep forecasts for daily municipal solid waste (MSW) generation in Seattle, Washington. For MSW generation prediction with long history data, this forecasting model was created based on a nonlinear dynamic method called phase-space reconstruction. Compared with other nonlinear predictive models, such as artificial neural network (ANN) and partial least square-support vector machine (PLS-SVM), and a commonly used linear seasonal autoregressive integrated moving average (sARIMA) model, this method has demonstrated better prediction accuracy from 1-step ahead prediction to 14-step ahead prediction assessed by both mean absolute percentage error (MAPE) and root mean square error (RMSE). Max error, MAPE, and RMSE show that chaotic models were more reliable than the other three models. As chaotic models do not involve random walk, their performance does not vary while ANN and PLS-SVM make different forecasts in each trial. Moreover, this chaotic model was less time consuming than ANN and PLS-SVM models.

  4. Space modeling with SolidWorks and NX

    CERN Document Server

    Duhovnik, Jože; Drešar, Primož

    2015-01-01

    Through a series of step-by-step tutorials and numerous hands-on exercises, this book aims to equip the reader with both a good understanding of the importance of space in the abstract world of engineers and the ability to create a model of a product in virtual space – a skill essential for any designer or engineer who needs to present ideas concerning a particular product within a professional environment. The exercises progress logically from the simple to the more complex; while SolidWorks or NX is the software used, the underlying philosophy is applicable to all modeling software. In each case, the explanation covers the entire procedure from the basic idea and production capabilities through to the real model; the conversion from 3D model to 2D manufacturing drawing is also clearly explained. Topics covered include modeling of prism, axisymmetric, symmetric, and sophisticated shapes; digitization of physical models using modeling software; creation of a CAD model starting from a physical model; free fo...

  5. A depth-averaged 2-D model of flow and sediment transport in coastal waters

    Science.gov (United States)

    Sanchez, Alejandro; Wu, Weiming; Beck, Tanya M.

    2016-11-01

    A depth-averaged 2-D model has been developed to simulate unsteady flow and nonuniform sediment transport in coastal waters. The current motion is computed by solving the phase-averaged 2-D shallow water flow equations reformulated in terms of total-flux velocity, accounting for the effects of wave radiation stresses and general diffusion or mixing induced by current, waves, and wave breaking. The cross-shore boundary conditions are specified by assuming fully developed longshore current and wave setup that are determined using the reduced 1-D momentum equations. A 2-D wave spectral transformation model is used to calculate the wave height, period, direction, and radiation stresses, and a surface wave roller model is adopted to consider the effects of surface roller on the nearshore currents. The nonequilibrium transport of nonuniform total-load sediment is simulated, considering sediment entrainment by current and waves, the lag of sediment transport relative to the flow, and the hiding and exposure effect of nonuniform bed material. The flow and sediment transport equations are solved using an implicit finite volume method on a variety of meshes including nonuniform rectangular, telescoping (quadtree) rectangular, and hybrid triangular/quadrilateral meshes. The flow and wave models are integrated through a carefully designed steering process. The model has been tested in three field cases, showing generally good performance.

  6. A reduced-complexity model for sediment transport and step-pool morphology

    Science.gov (United States)

    Saletti, Matteo; Molnar, Peter; Hassan, Marwan A.; Burlando, Paolo

    2016-07-01

    A new particle-based reduced-complexity model to simulate sediment transport and channel morphology in steep streams in presented. The model CAST (Cellular Automaton Sediment Transport) contains phenomenological parameterizations, deterministic or stochastic, of sediment supply, bed load transport, and particle entrainment and deposition in a cellular-automaton space with uniform grain size. The model reproduces a realistic bed morphology and typical fluctuations in transport rates observed in steep channels. Particle hop distances, from entrainment to deposition, are well fitted by exponential distributions, in agreement with field data. The effect of stochasticity in both the entrainment and the input rate is shown. A stochastic parameterization of the entrainment is essential to create and maintain a realistic channel morphology, while the intermittent transport of grains in CAST shreds the input signal and its stochastic variability. A jamming routine has been added to CAST to simulate the grain-grain and grain-bed interactions that lead to particle jamming and step formation in a step-pool stream. The results show that jamming is effective in generating steps in unsteady conditions. Steps are created during high-flow periods and they survive during low flows only in sediment-starved conditions, in agreement with the jammed-state hypothesis of Church and Zimmermann (2007). Reduced-complexity models like CAST give new insights into the dynamics of complex phenomena such as sediment transport and bedform stability and are a useful complement to fully physically based models to test research hypotheses.

  7. Parameter uncertainty, sensitivity, and sediment coupling in bioenergetics-based food web models

    Energy Technology Data Exchange (ETDEWEB)

    Barron, M.G.; Cacela, D.; Beltman, D. [Hagler Bailly, Boulder, CO (United States)

    1995-12-31

    A bioenergetics-based food web model was developed and calibrated using measured PCB water and sediment concentrations in two Great Lakes food webs: Green Bay, Michigan and Lake Ontario. The model incorporated functional based trophic levels and sediment, water, and food chain exposures of PCBs to aquatic biota. Sensitivity analysis indicated the parameters with the greatest influence on PCBs in top predators were lipid content of plankton and benthos, planktivore assimilation efficiency, Kow, prey selection, and ambient temperature. Sediment-associated PCBs were estimated to contribute over 90% of PCBs in benthivores and less than 50% in piscivores. Ranges of PCB concentrations in top predators estimated by Monte Carlo simulation incorporating parameter uncertainty were within one order of magnitude of modal values. Model applications include estimation of exceedences of human and ecological thresholds. The results indicate that point estimates from bioenergetics-based food web models have substantial uncertainty that should be considered in regulatory and scientific applications.

  8. Application of 2-D sediment model to fluctuating backwater area of Yangtze River

    Directory of Open Access Journals (Sweden)

    Yong FAN

    2009-09-01

    Full Text Available Based on the characteristics of backflow, a two-dimensional mathematical model of sediment movement was established. The complexity of the watercourse boundary at the confluence of the main stream and the tributary was dealt with using a boundary-fitting orthogonal coordinate system. The basic equation of the two-dimensional total sediment load model, the numerical calculation format, and key problems associated with using the orthogonal curvilinear coordinate system were discussed. Water and sediment flow in the Chongqing reach of the Yangtze River were simulated. The calculated water level, flow velocity distribution, amount of silting and scouring, and alluvial distribution are found to be in agreement with the measured data, which indicates that the numerical model and calculation method are reasonable. The model can be used for calculation of flow in a relatively complicated river network.

  9. Application of 2-D sediment model to fluctuating backwater area of Yangtze River

    Institute of Scientific and Technical Information of China (English)

    Yong FAN

    2009-01-01

    Based on the characteristics of backflow,a two-dimensional mathematical model of sediment movement was established.The complexity of the watercourse boundary at the confluence of the main stream and the tributary was dealt with using a boundary-fitting orthogonal coordinate system.The basic equation of the two-dimensional total sediment load model,the numerical calculation format,and key problems associated with using the orthogonal curvilinear coordinate system were discussed.Water and sediment flow in the Chongqing reach of the Yangtze River were simulated.The calculated water level,flow velocity distribution,amount of silting and scouring,and alluvial distribution are found to be in agreement with the measured data,which indicates that the numerical model and calculation method are reasonable.The model can be used for calculation of flow in a relatively complicated river network.

  10. Well-balanced and flexible morphological modeling of swash hydrodynamics and sediment transport

    CERN Document Server

    Hu, Peng; He, Zhiguo; Pähtz, Thomas; Yue, Zhiyuan

    2014-01-01

    Existing numerical models of the swash zone are relatively inflexible in dealing with sediment transport due to a high dependence of the deployed numerical schemes on empirical sediment transport relations. Moreover, these models are usually not well-balanced, meaning they are unable to correctly simulate quiescent flow. Here a well-balanced and flexible morphological model for the swash zone is presented. The nonlinear shallow water equations and the Exner equation are discretized by the shock-capturing finite volume method, in which the numerical flux and the bed slope source term are estimated by a well-balanced version of the SLIC (Slope LImited Centered) scheme that does not depend on empirical sediment transport relations. The satisfaction of the well-balanced property is demonstrated through simulating quiescent coastal flow. The quantitative accuracy of the model in reproducing key parameters (i.e., the notional shoreline position, the swash depth, the flow velocity, the overtopping flow volume, the b...

  11. Model of spontaneous evaporating droplet on solid horizontal substrate

    Science.gov (United States)

    Dunin, S. Z.; Nagornov, O. V.; Trifonenkov, V. P.

    2017-01-01

    Free evaporation of sessile liquid non-isothermal drop on solid substrate is analyzed. Exact formulae for temperature and concentration fields are found out as functions of dimensionless parameters. The non-uniform temperature distribution at the drop surface creates the thermocapillar Marangonni forces that change their direction in the vicinity of stagnation points. Direction of the forces and disposition of the stagnation points are derived as function of contact angle and thermodynamic parameters of model. Conditions for the stagnation points to appear are found out. Moreover, maximal value of contact angle corresponding to presence of stagnation points in droplet is calculated as a function of the thermal conductivity ratio.

  12. Forecasting municipal solid waste generation using artificial intelligence modelling approaches.

    Science.gov (United States)

    Abbasi, Maryam; El Hanandeh, Ali

    2016-10-01

    Municipal solid waste (MSW) management is a major concern to local governments to protect human health, the environment and to preserve natural resources. The design and operation of an effective MSW management system requires accurate estimation of future waste generation quantities. The main objective of this study was to develop a model for accurate forecasting of MSW generation that helps waste related organizations to better design and operate effective MSW management systems. Four intelligent system algorithms including support vector machine (SVM), adaptive neuro-fuzzy inference system (ANFIS), artificial neural network (ANN) and k-nearest neighbours (kNN) were tested for their ability to predict monthly waste generation in the Logan City Council region in Queensland, Australia. Results showed artificial intelligence models have good prediction performance and could be successfully applied to establish municipal solid waste forecasting models. Using machine learning algorithms can reliably predict monthly MSW generation by training with waste generation time series. In addition, results suggest that ANFIS system produced the most accurate forecasts of the peaks while kNN was successful in predicting the monthly averages of waste quantities. Based on the results, the total annual MSW generated in Logan City will reach 9.4×10(7)kg by 2020 while the peak monthly waste will reach 9.37×10(6)kg.

  13. Converting Boundary Representation Solid Models to Half-Space Representation Models for Monte Carlo Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Davis JE, Eddy MJ, Sutton TM, Altomari TJ

    2007-03-01

    Solid modeling computer software systems provide for the design of three-dimensional solid models used in the design and analysis of physical components. The current state-of-the-art in solid modeling representation uses a boundary representation format in which geometry and topology are used to form three-dimensional boundaries of the solid. The geometry representation used in these systems is cubic B-spline curves and surfaces--a network of cubic B-spline functions in three-dimensional Cartesian coordinate space. Many Monte Carlo codes, however, use a geometry representation in which geometry units are specified by intersections and unions of half-spaces. This paper describes an algorithm for converting from a boundary representation to a half-space representation.

  14. Flow Dynamics and Sediment Entrainment in Natural Turbidity Currents Inferred from Numerical Modeling

    Science.gov (United States)

    Traer, M. M.; Hilley, G. E.; Fildani, A.

    2009-12-01

    Submarine turbidity currents derive their momentum from gravity acting upon the density contrast between sediment-laden and clear water, and so unlike fluvial systems, the dynamics of such flows are inextricably linked to the rates at which they deposit and entrain sediment. We have analyzed the sensitivity of the growth and maintenance of turbidity currents to sediment entrainment and deposition using the layer-averaged equations of conservation of fluid and sediment mass, and conservation of momentum and turbulent kinetic energy. Our model results show that the dynamics of turbidity currents are extremely sensitive to the functional form and empirical constants of the relationship between sediment entrainment and friction velocity. Data on the relationship between sediment entrainment and friction velocity for submarine density flows are few and as a result, entrainment formulations are populated with data from sub-aerial flows not driven by the density contrast between clear and turbid water. If we entertain the possibility that sediment entrainment in sub-aerial rivers is different than in dense underflows, flow parameters such as velocity, height, and concentration were found nearly impossible to predict beyond a few hundred meters based on the limited laboratory data available that constrain the sediment entrainment process in turbidity currents. The sensitivity of flow dynamics to the functional relationship between friction velocity and sediment entrainment indicates that independent calibration of a sediment entrainment law in the submarine environment is necessary to realistically predict the dynamics of these flows and the resulting patterns of erosion and deposition. To calibrate such a relationship, we have developed an inverse methodology that utilizes existing submarine channel morphology as a means of constraining the sediment entrainment function parameters. We use a Bayesian Metropolis-Hastings sampler to determine the sediment entrainment

  15. Development of a three-dimensional, regional, coupled wave, current, and sediment-transport model

    Science.gov (United States)

    Warner, J.C.; Sherwood, C.R.; Signell, R.P.; Harris, C.K.; Arango, H.G.

    2008-01-01

    We are developing a three-dimensional numerical model that implements algorithms for sediment transport and evolution of bottom morphology in the coastal-circulation model Regional Ocean Modeling System (ROMS v3.0), and provides a two-way link between ROMS and the wave model Simulating Waves in the Nearshore (SWAN) via the Model-Coupling Toolkit. The coupled model is applicable for fluvial, estuarine, shelf, and nearshore (surfzone) environments. Three-dimensional radiation-stress terms have been included in the momentum equations, along with effects of a surface wave roller model. The sediment-transport algorithms are implemented for an unlimited number of user-defined non-cohesive sediment classes. Each class has attributes of grain diameter, density, settling velocity, critical stress threshold for erosion, and erodibility constant. Suspended-sediment transport in the water column is computed with the same advection-diffusion algorithm used for all passive tracers and an additional algorithm for vertical settling that is not limited by the CFL criterion. Erosion and deposition are based on flux formulations. A multi-level bed framework tracks the distribution of every size class in each layer and stores bulk properties including layer thickness, porosity, and mass, allowing computation of bed morphology and stratigraphy. Also tracked are bed-surface properties including active-layer thickness, ripple geometry, and bed roughness. Bedload transport is calculated for mobile sediment classes in the top layer. Bottom-boundary layer submodels parameterize wave-current interactions that enhance bottom stresses and thereby facilitate sediment transport and increase bottom drag, creating a feedback to the circulation. The model is demonstrated in a series of simple test cases and a realistic application in Massachusetts Bay. ?? 2008 Elsevier Ltd. All rights reserved.

  16. 3D modelling of the transport and fate of riverine fine sediment exported to a semi-enclosed system

    Science.gov (United States)

    Delandmeter, Philippe; Lambrechts, Jonathan; Lewis, Stephen; Legat, Vincent; Deleersnijder, Eric; Wolanski, Eric

    2015-04-01

    Understanding the transport and fate of suspended sediment exported by rivers is crucial for the management of sensitive marine ecosystems. Sediment transport and fate can vary considerably depending on the geophysical characteristics of the offshore environment (i.e. open, semi-enclosed and enclosed systems and the nature of the continental shelf). In this presentation, we focus on a semi-enclosed setting in the Great Barrier Reef, NE Australia. In this system, the large tropical Burdekin River discharges to a long and narrow continental shelf containing numerous headlands and embayments. Using a new 3D sediment model we developed and SLIM 3D, a Finite Element 3D model for coastal flows, we highlight the key processes of sediment transport for such a system. We validate the model with available measured data from the region. Wind direction and speed during the high river flows are showed to largely control the dynamics and final fate of the sediments. Most (71%) of the sediment load delivered by the river is deposited and retained near the river mouth. The remaining sediment is transported further afield in riverine freshwater plumes. The suspended sediment transported longer distances in the freshwater plumes can reach sensitive marine ecosystems. These results are compared to previous studies on the Burdekin River sediment fate and differences are analysed. The model suggests that wind-driven resuspension events will redistribute sediments within an embayment but have little influence on transporting sediments from bay to bay.

  17. Modelling daily sediment yield from a meso-scale catchment, a case study in SW Poland

    Energy Technology Data Exchange (ETDEWEB)

    Keesstra, S. D.; Schoorl, J.; Temme, A. J. A. M.

    2009-07-01

    For management purposes it is important to be able to assess the sediment yield of a catchment. however, at this moment models designed for estimating sediment yield are only capable to give either very detailed storm-based information or year averages. The storm-based models require input data that are not available for most catchment. However, models that estimate yearly averages, ignore a lot of other detailed information, like daily discharge and precipitation data. There are currently no models available that model sediment yield on the temporal scale of one day and the spatial scale of a meso-scale catchment, without making use of very detailed input data. To fill this scientific and management gap, landscape evolution model LAPSUS has been adapted to model sediment yield on a daily basis. This model has the water balance as a base. To allow calibration with the discharge at the outlet, a subsurface flow module has been added to the model. (Author) 12 refs.

  18. Hydrodynamic and Sediment Modelling within a Macro Tidal Estuary: Port Curtis Estuary, Australia

    Directory of Open Access Journals (Sweden)

    Ryan J. K. Dunn

    2015-07-01

    Full Text Available An understanding of sediment transport processes and resultant concentration dynamics in estuaries is of great importance to engineering design awareness and the management of these environments. Predictive modelling approaches provide an opportunity to investigate and address potential system responses to nominated events, changes, or conditions of interest, often on high temporal and spatial resolution scales. In this study, a three-dimensional hydrodynamic model and wave model were validated and applied to generate forcing conditions for input into a sediment transport model for the period 7 May 2010–30 October 2010 within a macro tidal estuary, Port Curtis estuary (Australia. The hydrodynamic model was verified against surface and near-bottom current measurements. The model accurately reproduced the variations of surface and near-bottom currents at both a mid-estuary and upper-estuary location. Sediment transport model predictions were performed under varying meteorological conditions and tidal forcing over a 180-day period and were validated against turbidity data collected at six stations within Port Curtis estuary. The sediment transport model was able to predict both the magnitudes of the turbidity levels and the modulation induced by the neap and spring tides and wind-wave variations. The model-predicted (converted turbidity levels compared favourably with the measured surface water turbidity levels at all six stations. The study results have useful practical application for Port Curtis estuary, including providing predictive capabilities to support the selection of locations for monitoring/compliance sites.

  19. Macro Level Modeling of a Tubular Solid Oxide Fuel Cell

    Directory of Open Access Journals (Sweden)

    Farshid Zabihian

    2010-11-01

    Full Text Available This paper presents a macro-level model of a solid oxide fuel cell (SOFC stack implemented in Aspen Plus® for the simulation of SOFC system. The model is 0-dimensional and accepts hydrocarbon fuels such as reformed natural gas, with user inputs of current density, fuel and air composition, flow rates, temperature, pressure, and fuel utilization factor. The model outputs the composition of the exhaust, work produced, heat available for the fuel reformer, and electrochemical properties of SOFC for model validation. It was developed considering the activation, concentration, and ohmic losses to be the main over-potentials within the SOFC, and mathematical expressions for these were chosen based on available studies in the literature. The model also considered the water shift reaction of CO and the methane reforming reaction. The model results were validated using experimental data from Siemens Westinghouse. The results showed that the model could capture the operating pressure and temperature dependency of the SOFC performance successfully in an operating range of 1–15 atm for pressure and 900 °C–1,000 °C for temperature. Furthermore, a sensitivity analysis was performed to identify the model constants and input parameters that impacted the over-potentials.

  20. Assimilation of remote sensing observations into a sediment transport model of China's largest freshwater lake: spatial and temporal effects.

    Science.gov (United States)

    Zhang, Peng; Chen, Xiaoling; Lu, Jianzhong; Zhang, Wei

    2015-12-01

    Numerical models are important tools that are used in studies of sediment dynamics in inland and coastal waters, and these models can now benefit from the use of integrated remote sensing observations. This study explores a scheme for assimilating remotely sensed suspended sediment (from charge-coupled device (CCD) images obtained from the Huanjing (HJ) satellite) into a two-dimensional sediment transport model of Poyang Lake, the largest freshwater lake in China. Optimal interpolation is used as the assimilation method, and model predictions are obtained by combining four remote sensing images. The parameters for optimal interpolation are determined through a series of assimilation experiments evaluating the sediment predictions based on field measurements. The model with assimilation of remotely sensed sediment reduces the root-mean-square error of the predicted sediment concentrations by 39.4% relative to the model without assimilation, demonstrating the effectiveness of the assimilation scheme. The spatial effect of assimilation is explored by comparing model predictions with remotely sensed sediment, revealing that the model with assimilation generates reasonable spatial distribution patterns of suspended sediment. The temporal effect of assimilation on the model's predictive capabilities varies spatially, with an average temporal effect of approximately 10.8 days. The current velocities which dominate the rate and direction of sediment transport most likely result in spatial differences in the temporal effect of assimilation on model predictions.

  1. Comparing Two Numerical Models in Simulating Hydrodynamics and Sediment Transport at a Dual Inlet System, West-Central Florida

    Science.gov (United States)

    2015-05-15

    1 COMPARING TWO NUMERICAL MODELS IN SIMULATING HYDRODYNAMICS AND SEDIMENT TRANSPORT AT A DUAL INLET SYSTEM, WEST-CENTRAL FLORIDA PING WANG1...numerical modeling systems, CMS and DELFT3D, in simulating the hydrodynamic and sediment transport processes. The model results are compared with...Introduction Simulating complex fields of wave, current, sediment transport , and morphology change in the vicinity of tidal inlets is a

  2. Quantifying and modeling soil erosion and sediment export from construction sites in southern California

    Science.gov (United States)

    Wernet, A. K.; Beighley, R. E.

    2006-12-01

    Soil erosion is a power process that continuously alters the Earth's landscape. Human activities, such as construction and agricultural practices, and natural events, such as forest fires and landslides, disturb the landscape and intensify erosion processes leading to sudden increases in runoff sediment concentrations and degraded stream water quality. Understanding soil erosion and sediment transport processes is of great importance to researchers and practicing engineers, who routinely use models to predict soil erosion and sediment movement for varied land use and climate change scenarios. However, existing erosion models are limited in their applicability to constructions sites which have highly variable soil conditions (density, moisture, surface roughness, and best management practices) that change often in both space and time. The goal of this research is to improve the understanding, predictive capabilities and integration of treatment methodologies for controlling soil erosion and sediment export from construction sites. This research combines modeling with field monitoring and laboratory experiments to quantify: (a) spatial and temporal distribution of soil conditions on construction sites, (b) soil erosion due to event rainfall, and (c) potential offsite discharge of sediment with and without treatment practices. Field sites in southern California were selected to monitor the effects of common construction activities (ex., cut/fill, grading, foundations, roads) on soil conditions and sediment discharge. Laboratory experiments were performed in the Soil Erosion Research Laboratory (SERL), part of the Civil and Environmental Engineering department at San Diego State University, to quantify the impact of individual factors leading to sediment export. SERL experiments utilize a 3-m by 10-m tilting soil bed with soil depths up to 1 m, slopes ranging from 0 to 50 percent, and rainfall rates up to 150 mm/hr (6 in/hr). Preliminary modeling, field and laboratory

  3. Experimental and numerical modelling of sedimentation in a rectangular shallow basin

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Numerical simulation of flows in shallow reservoirs has to be checked for its consistency in predicting real flow conditions and sedimentation patterns. Typical flow patterns may exhibit flow separation at the inlet, accompanied by several recirculation and stagnation areas all over the reservoir surface. The aim of the present research project is to study the influence of the geometry of a reservoir on sediment transport and deposition numerically and experimentally, focusing on a prototype reservoir depth between 5 and 15 m as well as suspended sediment transport.A series of numerical simulations is presented and compared with scaled laboratory experiments, with the objective of testing the sensitivity to different flow and sediment parameters and different turbulence closure schemes. Different scenarios are analyzed and a detailed comparison of preliminary laboratory tests and some selected simulations are presented.The laboratory experiments show that suspended sediment transport and deposition are determined by the initial flow pattern and by the upstream and downstream boundary conditions. In the experiments, deposition in the rectangular basin systematically developed along the left bank, although inflow and outflow were positioned symmetrically along the centre of the basin. Three major horizontal eddies developed influencing the sediment deposition pattern. Although asymmetric flow patterns are privileged, a symmetric pattern can appear from time to time.This particular behaviour could also be reproduced by a two-dimensional depth-averaged flow and sediment transport model (CCHE2D). The paper presents numerical simulations using different turbulence closure schemes (k-e and eddy viscosity models). In spite of the symmetric setup, these generally produced an asymmetric flow pattern that can easily switch sides depending on the assumptions made for the initial and boundary conditions. When using the laboratory experiment as a reference, the most reliable

  4. Application of hierarchical Bayesian unmixing models in river sediment source apportionment

    Science.gov (United States)

    Blake, Will; Smith, Hugh; Navas, Ana; Bodé, Samuel; Goddard, Rupert; Zou Kuzyk, Zou; Lennard, Amy; Lobb, David; Owens, Phil; Palazon, Leticia; Petticrew, Ellen; Gaspar, Leticia; Stock, Brian; Boeckx, Pacsal; Semmens, Brice

    2016-04-01

    Fingerprinting and unmixing concepts are used widely across environmental disciplines for forensic evaluation of pollutant sources. In aquatic and marine systems, this includes tracking the source of organic and inorganic pollutants in water and linking problem sediment to soil erosion and land use sources. It is, however, the particular complexity of ecological systems that has driven creation of the most sophisticated mixing models, primarily to (i) evaluate diet composition in complex ecological food webs, (ii) inform population structure and (iii) explore animal movement. In the context of the new hierarchical Bayesian unmixing model, MIXSIAR, developed to characterise intra-population niche variation in ecological systems, we evaluate the linkage between ecological 'prey' and 'consumer' concepts and river basin sediment 'source' and sediment 'mixtures' to exemplify the value of ecological modelling tools to river basin science. Recent studies have outlined advantages presented by Bayesian unmixing approaches in handling complex source and mixture datasets while dealing appropriately with uncertainty in parameter probability distributions. MixSIAR is unique in that it allows individual fixed and random effects associated with mixture hierarchy, i.e. factors that might exert an influence on model outcome for mixture groups, to be explored within the source-receptor framework. This offers new and powerful ways of interpreting river basin apportionment data. In this contribution, key components of the model are evaluated in the context of common experimental designs for sediment fingerprinting studies namely simple, nested and distributed catchment sampling programmes. Illustrative examples using geochemical and compound specific stable isotope datasets are presented and used to discuss best practice with specific attention to (1) the tracer selection process, (2) incorporation of fixed effects relating to sample timeframe and sediment type in the modelling

  5. Aeolian processes across transverse dunes. II: Modelling the sediment transport and profile development

    NARCIS (Netherlands)

    van Dijk, P.M.; Arens, S.M.; van Boxel, J.H.

    1999-01-01

    This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and em

  6. Modeling of Sediment Transport and Self-Cleansing in Sea Outfalls

    DEFF Research Database (Denmark)

    Larsen, Torben; Ibro, I.

    2011-01-01

    The paper describes an on-going project on modeling of sediment transport in outfalls with special focus on the self-cleansing problem occurring due to the daily flow variations seen in outfalls. The two central elements of the project is the development of the numerical model and a matching phys...

  7. Aeolian processes across transverse dunes. II: Modelling the sediment transport and profile development

    NARCIS (Netherlands)

    van Dijk, P.M.; Arens, S.M.; van Boxel, J.H.

    1999-01-01

    This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and

  8. Estimating Sediment Yield on Disturbed Rangeland Using the Rangeland Hydrology and Erosion Model (RHEM)

    Science.gov (United States)

    The Rangeland Hydrology and Erosion Model (RHEM) is an event-based model that estimates runoff, erosion, and sediment delivery rates and volumes at the spatial scale of the hillslope and the temporal scale of a single rainfall event. It represents erosion processes on normal rangeland, as well as, r...

  9. Applications of GSTARS Computer Models for Solving River and Reservoir Sedimentation Problems

    Institute of Scientific and Technical Information of China (English)

    YANG Chih Ted

    2008-01-01

    GSTARS (Generalized Sediment Transport model for Alluvial River Simulation) is a series of computer models developed by the U.S. Bureau of Reclamation while the author was employed by that agency. The stream tube concept is used in all GSTARS models which allow us to solve one-dimensional equations for each stream tube independently and obtain semi-two-dimensional variation of the hydraulic conditions along and across stream tubes for rivers and reservoirs. Sedi-ment transport, scour, and deposition processes are simulated along each stream tube independ-ently to give us a semi-three-dimensional variation of the bed geometry. Most sediment transport computer models assume that channel width is given and cannot change during the simulation process. GSTARS models apply the theory of minimum stream power to the determination of op-timum channel width and channel geometry. The concepts of channel side stability, and active,inactive, and armoring layers are used in all GSTARS models for realistic long-term simulation and prediction of the scour and deposition processes in rivers and reservoirs.GSTARS models have been applied in many countries for solving a wide range of river and reservoir sedimentation prob-lems. Case studies will be used to illustrate the applications of GSTARS computer models.

  10. Modeling plan-form deltaic response to changes in fluvial sediment supply

    NARCIS (Netherlands)

    Nienhuis, J.H.; Ashton, A.D.; Roos, P.C.; Hulscher, S.J.M.H.; Giosan, L.; Kranenburg, W.M.; Horstman, E.M.; Wijnberg, K.M.

    2012-01-01

    This study focuses on the effects of changes in fluvial sediment supply on the plan-form shape of wave-dominated deltas. We apply a one-line numerical shoreline model to calculate shoreline evolution after (I) elimination and (II) time-periodic variation of fluvial input. Model results suggest four

  11. Aeolian processes across transverse dunes. II: Modelling the sediment transport and profile development

    NARCIS (Netherlands)

    van Dijk, P.M.; Arens, S.M.; van Boxel, J.H.

    1999-01-01

    This paper discusses a model which simulates dune development resulting from aeolian saltation transport. The model was developed for application to coastal foredunes, but is also applicable to sandy deserts with transverse dunes. Sediment transport is calculated using published deterministic and em

  12. Modelling the advance–retreat cycle of a tidewater glacier with simple sediment dynamics

    NARCIS (Netherlands)

    Oerlemans, J.; Nick, Faezeh Maghami

    2006-01-01

    We present a simple coupled glacier-sediment model to simulate the evolution of a tidewater glacier. The model is based on a consideration of the total mass budget of a glacier, whereas ice mechanics are fully parameterized. The calving rate at the glacier terminus is assumed to be proportional to t

  13. Saturation Concentrations of Suspended Fine Sediment: Computations with the Prandtl Mixing-Length Model

    NARCIS (Netherlands)

    Kranenburg, C.

    1998-01-01

    Adopting a 1DV numerical model including the standard k-eps turbulence model, Winterwerp et al. (1999) calculated a saturation concentration for an initially uniform distribution of fine sediment concentration in steady flow. At concentrations exceeding the saturation concentration the concentration

  14. Evolutionary design of a generalized polynomial neural network for modelling sediment transport in clean pipes

    Science.gov (United States)

    Ebtehaj, Isa; Bonakdari, Hossein; Khoshbin, Fatemeh

    2016-10-01

    To determine the minimum velocity required to prevent sedimentation, six different models were proposed to estimate the densimetric Froude number (Fr). The dimensionless parameters of the models were applied along with a combination of the group method of data handling (GMDH) and the multi-target genetic algorithm. Therefore, an evolutionary design of the generalized GMDH was developed using a genetic algorithm with a specific coding scheme so as not to restrict connectivity configurations to abutting layers only. In addition, a new preserving mechanism by the multi-target genetic algorithm was utilized for the Pareto optimization of GMDH. The results indicated that the most accurate model was the one that used the volumetric concentration of sediment (CV), relative hydraulic radius (d/R), dimensionless particle number (Dgr) and overall sediment friction factor (λs) in estimating Fr. Furthermore, the comparison between the proposed method and traditional equations indicated that GMDH is more accurate than existing equations.

  15. Modelling potential impacts of bottom trawl fisheries on soft sediment biogeochemistry in the North Sea†

    Directory of Open Access Journals (Sweden)

    Parker Ruth

    2001-12-01

    Full Text Available Bottom trawling causes physical disturbance to sediments particularly in shelf areas. The disturbance due to trawling is most significant in deeper areas with softer sediments where levels of natural disturbance due to wave and tidal action are low. In heavily fished areas, trawls may impact the same area of seabed more than four times per year. A single pass of a beam trawl, the heaviest gear routinely used in shelf sea fisheries, can kill 5–65% of the resident fauna and mix the top few cm of sediment. We expect that sediment community function, carbon mineralisation and biogeochemical fluxes will be strongly affected by trawling activity because the physical effects of trawling are equivalent to those of an extreme bioturbator, and yet, unlike bioturbating macrofauna, trawling does not directly contribute to community metabolism. We used an existing box-model of a generalised soft sediment system to examine the effects of trawling disturbance on carbon mineralisation and chemical concentrations. We contrasted the effects of a natural scenario, where bioturbation is a function of macrobenthos biomass, with an anthropogenic impact scenario where physical disturbance results from trawling rather than the action of bioturbating macrofauna. Simulation results suggest that the effects of low levels of trawling disturbance will be similar to those of natural bioturbators but that high levels of trawling disturbance prevent the modelled system from reaching equilibrium due to large carbon fluxes between oxic and anoxic carbon compartments. The presence of macrobenthos in the natural disturbance scenario allowed sediment chemical storage and fluxes to reach equilibrium. This is because the macrobenthos are important carbon consumers in the system whose presence reduces the magnitude of available carbon fluxes. In soft sediment systems, where the level physical disturbance due to waves and tides is low, model results suggest that intensive trawling

  16. Elastic velocity models for gas-hydrate-bearing sediments-a comparison

    Science.gov (United States)

    Chand, Shyam; Minshull, Tim A.; Gei, Davide; Carcione, José M.

    2004-11-01

    The presence of gas hydrate in oceanic sediments is mostly identified by bottom-simulating reflectors (BSRs), reflection events with reversed polarity following the trend of the seafloor. Attempts to quantify the amount of gas hydrate present in oceanic sediments have been based mainly on the presence or absence of a BSR and its relative amplitude. Recent studies have shown that a BSR is not a necessary criterion for the presence of gas hydrates, but rather its presence depends on the type of sediments and the in situ conditions. The influence of hydrate on the physical properties of sediments overlying the BSR is determined by the elastic properties of their constituents and on sediment microstructure. In this context several approaches have been developed to predict the physical properties of sediments, and thereby quantify the amount of gas/gas hydrate present from observed deviations of these properties from those predicted for sediments without gas hydrate. We tested four models: the empirical weighted equation (WE); the three-phase effective-medium theory (TPEM); the three-phase Biot theory (TPB) and the differential effective-medium theory (DEM). We compared these models for a range of variables (porosity and clay content) using standard values for physical parameters. The comparison shows that all the models predict sediment properties comparable to field values except for the WE model at lower porosities and the TPB model at higher porosities. The models differ in the variation of velocity with porosity and clay content. The variation of velocity with hydrate saturation is also different, although the range is similar. We have used these models to predict velocities for field data sets from sediment sections with and without gas hydrates. The first is from the Mallik 2L-38 well, Mackenzie Delta, Canada, and the second is from Ocean Drilling Program (ODP) Leg 164 on Blake Ridge. Both data sets have Vp and Vs information along with the composition and

  17. Development of pressurized liquid extraction and solid-phase microextraction combined with gas chromatography and flame photometric detection for the determination of organophosphate esters in sediments.

    Science.gov (United States)

    Zheng, Jianming; Gao, Zhanqi; Yuan, Wenting; He, Huan; Yang, Shaogui; Sun, Cheng

    2014-09-01

    Organophosphate esters have been extensively used as flame retardants and plasticizers. The analysis of organophosphate esters in the environment is a hot topic because many of them are toxic and persistent. We developed a novel procedure for determining organophosphate esters in sediment. In this work, pressurized liquid extraction and solid-phase microextraction are used for sample preparation to extract and concentrate the analytes, which are then analyzed by gas chromatography with flame photometric detection. The extraction parameters of pressurized liquid extraction were investigated and optimized by orthogonal design and then evaluated by range analysis and analysis of variance. Under the optimal conditions, the proposed procedure showed wide linear ranges (0.90-100 ng/g) with correlation coefficients ranging from 0.9921 to 0.9990. The detection limits of the method were in the range of 0.009-0.280 ng/g with standard deviations ranging from 2.2 to 9.5%. Recoveries of the proposed method ranged from 82.3 to 108.9% with relative standard deviations esters in real sediments with recoveries varying from 79.8 to 107.3%. The proposed method was proved to be simple, easy, and sensitive for analyzing organophosphate esters in sediment samples. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Pressurized liquid extraction using water/isopropanol coupled with solid-phase extraction cleanup for industrial and anthropogenic waste-indicator compounds in sediment

    Science.gov (United States)

    Burkhardt, M.R.; ReVello, R.C.; Smith, S.G.; Zaugg, S.D.

    2005-01-01

    A broad range of organic compounds is recognized as environmentally relevant for their potential adverse effects on human and ecosystem health. This method was developed to better determine the distribution of 61 compounds that are typically associated with industrial and household waste as well as some that are toxic and known (or suspected) for endocrine-disrupting potential extracted from environmental sediment samples. Pressurized liquid extraction (PLE) coupled with solid-phase extraction (SPE) was used to reduce sample preparation time, reduce solvent consumption to one-fifth of that required using dichloromethane-based Soxhlet extraction, and to minimize background interferences for full scan GC/MS analysis. Recoveries from spiked Ottawa sand, commercially available topsoil, and environmental stream sediment, fortified at 4-720 ??g per compound, averaged 76 ?? 13%. Initial method detection limits for single-component compounds ranged from 12.5 to 520 ??g/kg, based on 25 g samples. Results from 103 environmental sediment samples show that 36 out of 61 compounds (59%) were detected in at least one sample with concentrations ranging from 20 to 100,000 ??g/kg. The most frequently detected compound, beta-sitosterol, a plant sterol, was detected in 87 of the 103 (84.5%) environmental samples with a concentration range 360-100,000 ??g/kg. Results for a standard reference material using dichloromethane Soxhlet-based extraction are also compared. ?? 2004 Published by Elsevier B.V.

  19. Using high-performance mathematical modelling tools to predict erosion and sediment fluxes in peri-urban catchments

    Science.gov (United States)

    Pereira, André; Conde, Daniel; Ferreira, Carla S. S.; Walsh, Rory; Ferreira, Rui M. L.

    2017-04-01

    Deforestation and urbanization generally lead to increased soil erosion andthrough the indirect effect of increased overland flow and peak flood discharges. Mathematical modelling tools can be helpful for predicting the spatial distribution of erosion and the morphological changes on the channel network. This is especially useful to predict the impacts of land-use changes in parts of the watershed, namely due to urbanization. However, given the size of the computational domain (normally the watershed itself), the need for high spatial resolution data to model accurately sediment transport processes and possible need to model transcritical flows, the computational cost is high and requires high-performance computing techniques. The aim of this work is to present the latest developments of the hydrodynamic and morphological model STAV2D and its applicability to predict runoff and erosion at watershed scale. STAV2D was developed at CEris - Instituto Superior Técnico, Universidade de Lisboa - as a tool particularly appropriated to model strong transient flows in complex and dynamic geometries. It is based on an explicit, first-order 2DH finite-volume discretization scheme for unstructured triangular meshes, in which a flux-splitting technique is paired with a reviewed Roe-Riemann solver, yielding a model applicable to discontinuous flows over time-evolving geometries. STAV2D features solid transport in both Euleran and Lagrangian forms, with the aim of describing the transport of fine natural sediments and then the large individual debris. The model has been validated with theoretical solutions and laboratory experiments (Canelas et al., 2013 & Conde et al., 2015). STAV-2D now supports fully distributed and heterogeneous simulations where multiple different hardware devices can be used to accelerate computation time within a unified Object-Oriented approach: the source code for CPU and GPU has the same compilation units and requires no device specific branches, like

  20. Automatically extracting sheet-metal features from solid model

    Institute of Scientific and Technical Information of China (English)

    刘志坚; 李建军; 王义林; 李材元; 肖祥芷

    2004-01-01

    With the development of modern industry,sheet-metal parts in mass production have been widely applied in mechanical,communication,electronics,and light industries in recent decades; but the advances in sheet-metal part design and manufacturing remain too slow compared with the increasing importance of sheet-metal parts in modern industry. This paper proposes a method for automatically extracting features from an arbitrary solid model of sheet-metal parts; whose characteristics are used for classification and graph-based representation of the sheet-metal features to extract the features embodied in a sheet-metal part. The extracting feature process can be divided for valid checking of the model geometry,feature matching,and feature relationship. Since the extracted features include abundant geometry and engineering information,they will be effective for downstream application such as feature rebuilding and stamping process planning.

  1. Solid modeling and applications rapid prototyping, CAD and CAE theory

    CERN Document Server

    Um, Dugan

    2016-01-01

    The lessons in this fundamental text equip students with the theory of Computer Assisted Design (CAD), Computer Assisted Engineering (CAE), the essentials of Rapid Prototyping, as well as practical skills needed to apply this understanding in real world design and manufacturing settings. The book includes three main areas: CAD, CAE, and Rapid Prototyping, each enriched with numerous examples and exercises. In the CAD section, Professor Um outlines the basic concept of geometric modeling, Hermite and Bezier Spline curves theory, and 3-dimensional surface theories as well as rendering theory. The CAE section explores mesh generation theory, matrix notion for FEM, the stiffness method, and truss Equations. And in Rapid Prototyping, the author illustrates stereo lithographic theory and introduces popular modern RP technologies. Solid Modeling and Applications: Rapid Prototyping, CAD and CAE Theory is ideal for university students in various engineering disciplines as well as design engineers involved in product...

  2. Life Cycle Costing Model for Solid Waste Management

    DEFF Research Database (Denmark)

    Martinez-Sanchez, Veronica; Astrup, Thomas Fruergaard

    2014-01-01

    To ensure sustainability of solid waste management, there is a need for cost assessment models which are consistent with environmental and social assessments. However, there is a current lack of standardized terminology and methodology to evaluate economic performances and this complicates...... LCC, e.g. waste generator, waste operator and public finances and the perspective often defines the systemboundaries of the study, e.g. waste operators often focus on her/his own cost, i.e. technology based,whereas waste generators and public finances often focus on the entire waste system, i.......e. system based. Figure 1 illustrates the proposed modeling framework that distinguishes between: a) budget cost, b) externality costs and 3) transfers and defines unit costs of each technology (per ton of input waste). Unitcosts are afterwards combined with a mass balance to calculate the technology cost...

  3. Mesoscale Modeling of Impact Compaction of Primitive Solar System Solids

    CERN Document Server

    Davison, Thomas M; Bland, Philip A

    2016-01-01

    We have developed a method for simulating the mesoscale compaction of early solar system solids in low velocity impact events, using the iSALE shock physics code. Chondrules are represented by nonporous disks, placed within a porous matrix. By simulating impacts into bimodal mixtures over a wide range of parameter space (including the chondrule-to-matrix ratio, the matrix porosity and composition and the impact velocity), we have shown how each of these parameters influences the shock processing of heterogeneous materials. The temperature after shock processing shows a strong dichotomy: matrix temperatures are elevated much higher than the chondrules, which remain largely cold. Chondrules can protect some matrix from shock compaction, with shadow regions in the lee side of chondrules exhibiting higher porosity that elsewhere in the matrix. Using the results from this mesoscale modelling, we show how the $\\varepsilon-\\alpha$ porous compaction model parameters depend on initial bulk porosity. We also show that ...

  4. Automatically extracting sheet-metal features from solid model

    Institute of Scientific and Technical Information of China (English)

    刘志坚; 李建军; 王义林; 李材元; 肖祥芷

    2004-01-01

    With the development of modern industry, sheet-metal parts in mass production have been widely applied in mechanical, communication, electronics, and light industries in recent decades; but the advances in sheet-metal part design and manufacturing remain too slow compared with the increasing importance of sheet-metal parts in modern industry. This paper proposes a method for automatically extracting features from an arbitrary solid model of sheet-metal parts; whose characteristics are used for classification and graph-based representation of the sheet-metal features to extract the features embodied in a sheet-metal part. The extracting feature process can be divided for valid checking of the model geometry, feature matching, and feature relationship. Since the extracted features include abundant geometry and engineering information, they will be effective for downstream application such as feature rebuilding and stamping process planning.

  5. The mineral dissolution rate conundrum: Insights from reactive transport modeling of U isotopes and pore fluid chemistry in marine sediments

    Science.gov (United States)

    Maher, Kate; Steefel, Carl I.; DePaolo, Donald J.; Viani, Brian E.

    2006-01-01

    Pore water chemistry and 234U/ 238U activity ratios from fine-grained sediment cored by the Ocean Drilling Project at Site 984 in the North Atlantic were used as constraints in modeling in situ rates of plagioclase dissolution with the multicomponent reactive transport code Crunch. The reactive transport model includes a solid-solution formulation to enable the use of the 234U/ 238U activity ratios in the solid and fluid as a tracer of mineral dissolution. The isotopic profiles are combined with profiles of the major element chemistry (especially alkalinity and calcium) to determine whether the apparent discrepancy between laboratory and field dissolution rates still exists when a mechanistic reactive transport model is used to interpret rates in a natural system. A suite of reactions, including sulfate reduction and methane production, anaerobic methane oxidation, CaCO 3 precipitation, dissolution of plagioclase, and precipitation of secondary clay minerals, along with diffusive transport and fluid and solid burial, control the pore fluid chemistry in Site 984 sediments. The surface area of plagioclase in intimate contact with the pore fluid is estimated to be 6.9 m 2/g based on both grain geometry and on the depletion of 234U/ 238U in the sediment via α-recoil loss. Various rate laws for plagioclase dissolution are considered in the modeling, including those based on (1) a linear transition state theory (TST) model, (2) a nonlinear dependence on the undersaturation of the pore water with respect to plagioclase, and (3) the effect of inhibition by dissolved aluminum. The major element and isotopic methods predict similar dissolution rate constants if additional lowering of the pore water 234U/ 238U activity ratio is attributed to isotopic exchange via recrystallization of marine calcite, which makes up about 10-20% of the Site 984 sediment. The calculated dissolution rate for plagioclase corresponds to a rate constant that is about 10 2 to 10 5 times smaller than

  6. Two-phase flow modelling of sediment suspension in the Ems/Dollard estuary

    Science.gov (United States)

    Xu, Chunyang; Dong, Ping

    2017-05-01

    Understanding and quantifying mud suspension and sediment transport processes are of great importance for effective exploitation and sustainable management of estuarine environments. Event-based predictive models are widely used to identify the key interactions and mechanisms that govern the dynamics involved and to provide the essential parameterisation for assessing the long-term morphodynamic evolution of the estuaries. This study develops a one-dimensional-vertical (1DV) Reynolds averaged two-phase model for cohesive sediments resuspension driven by tidal flows. To capture the time-dependent flocculation process more accurately, a new drag force closure which relates empirically to settling velocity of mud flocs with suspended sediment concentration (SSC) is incorporated into the two-phase model. The model is then applied to simulate mud suspension in the Ems/Dollard estuary during two periods (June and August 1996) of tidal forcing. Numerical predictions of bed shear stresses and sediment concentrations at different elevations above the bed are compared with measured variations. The results confirm the importance of including flocculation effects in calculating the settling velocity of mud flocs and demonstrates the sensitivity of prediction with the settling velocity in terms of flocs concentration. Although the two-phase modelling approach can in principle better capture the essential interactions between fluid and sediment phases, its practical advantages over the simpler single phase approach cannot be confirmed for the data periods simulated, partly because the overall suspended sediment concentration measured is rather low and the interaction between the two phases is weak and also because the uncertainties in the relationship between the settling velocity and flocs concentration.

  7. Physically based modelling of sediment generation and transport under a large rainfall simulator

    Science.gov (United States)

    Adams, Russell; Elliott, Sandy

    2006-07-01

    A series of large rainfall simulator experiments was conducted in 2002 and 2003 on a small plot located in an experimental catchment in the North Island of New Zealand. These experiments measured both runoff and sediment transport under carefully controlled conditions. A physically based hydrological modelling system (SHETRAN) was then applied to reproduce the observed hydrographs and sedigraphs. SHETRAN uses physically based equations to represent flow and sediment transport, and two erodibility coefficients to model detachment of soil particles by raindrop erosion and overland flow erosion. The rate of raindrop erosion also depended on the amount of bare ground under the simulator; this was estimated before each experiment. These erodibility coefficients were calibrated systematically for summer and winter experiments separately, and lower values were obtained for the summer experiments. Earlier studies using small rainfall simulators in the vicinity of the plot also found the soil to be less erodible in summer and autumn. Limited validation of model parameters was carried out using results from a series of autumn experiments. The modelled suspended sediment load was also sensitive to parameters controlling the generation of runoff from the rainfall simulator plot; therefore, we found that accurate runoff predictions were important for the sediment predictions, especially from the experiments where the pasture cover was good and overland flow erosion was the dominant mechanism. The rainfall simulator experiments showed that the mass of suspended sediment increased post-grazing, and according to the model this was due to raindrop detachment. The results indicated that grazing cattle or sheep on steeply sloping hill-country paddocks should be carefully managed, especially in winter, to limit the transport of suspended sediment into watercourses.

  8. Development of a Coupled Hydrological/Sediment Yield Model for a Watershed at Regional Level

    Science.gov (United States)

    Rajbhandaril, Narayan; Crosson, William; Tsegaye, Teferi; Coleman, Tommy; Liu, Yaping; Soman, Vishwas

    1998-01-01

    Development of a hydrologic model for the study of environmental conservation requires a comprehensive understanding of individual-storm affecting hydrologic and sedimentologic processes. The hydrologic models that we are currently coupling are the Simulator for Hydrology and Energy Exchange at the Land Surface (SHEELS) and the Distributed Runoff Model (DRUM). SHEELS runs continuously to estimate surface energy fluxes and sub-surface soil water fluxes, while DRUM operates during and following precipitation events to predict surface runoff and peak flow through channel routing. The lateral re-distribution of surface water determined by DRUM is passed to SHEELS, which then adjusts soil water contents throughout the profile. The model SHEELS is well documented in Smith et al. (1993) and Laymen and Crosson (1995). The model DRUM is well documented in Vieux et al. (1990) and Vieux and Gauer (1994). The coupled hydrologic model, SHEELS/DRUM, does not simulate sedimentologic processes. The simulation of the sedimentologic process is important for environmental conservation planning and management. Therefore, we attempted to develop a conceptual frame work for coupling a sediment yield model with SHEELS/DRUM to estimate individual-storm sediment yield from a watershed at a regional level. The sediment yield model that will be used for this study is the Universal Soil Loss Equation (USLE) with some modifications to enable the model to predict individual-storm sediment yield. The predicted sediment yield does not include wind erosion and erosion caused by irrigation and snow melt. Units used for this study are those given by Foster et al. (1981) for SI units.

  9. Gravity effects on sediment sorting: limitations of models developed on Earth for Mars

    Science.gov (United States)

    Kuhn, N. J.; Kuhn, B.; Gartmann, A.

    2015-10-01

    Most studies on surface processes on planetary bodies assume that the use of empirical models developed for Earth is possible if the mathematical equations include all the relevant factors, such as gravity, viscosity and the density of water and sediment. However, most models for sediment transport on Earth are at least semi-empirical, using coefficients to link observed sediment movement to controlling factors such as flow velocity, slope and channel dimensions. However, using roughness and drag coefficients, as well as parameters describing incipient motion of particles, observed on Earth on another planet, violates, strictly speaking, the boundary conditions set for their application by fluid dynamics because the coefficienst describe a flow condition, not a particle property. Reduced gravity affects the flow around a settling partcile or over the bed of a watercourse, therefore data and models from Earth do not apply to another planet. Comparing observations from reduced gravity experiments and model results obtained on Earth confirm the significance of this error, e.g. by underestimating settling velocities of sandy particles by 10 to 50% for Mars when using models from Earth. In this study, the relevance of this error is examined by simulating the sorting of sediment deposited from water flowing on Mars. The results indicate that sorting on Mars is less pronounced than models calibrated on Earth suggest. This has implications for the selection of landing sites and,more importantly, the identification of strata potentially bearing traces of past life during rover missions on Mars. try, 2001

  10. Computational modeling of 137Cs contaminant transfer associated with sediment transport in Abukuma River.

    Science.gov (United States)

    Iwasaki, T; Nabi, M; Shimizu, Y; Kimura, I

    2015-01-01

    A numerical model capable of simulating the transfer of (137)Cs in rivers associated with transport of fine sediment is presented. The accident at Fukushima Dai-ichi Nuclear Power Plant (FDNPP) released radionuclides into the atmosphere, and after fallout several radionuclides in them, such as radiocesium ((134)Cs, (137)Cs) and radioiodine ((131)I) were adsorbed on surface soil particles around FDNPP and transported by surface water. To understand the transport and deposition of the radioactive contaminant along with surface soil particles and its flux to the ocean, we modeled the transport of the (137)Cs contaminant by computing the water flow and the associated washload and suspended load transport. We have developed a two-dimensional model to simulate the plane flow structure, sediment transport and associated (137)Cs contaminant transport in rivers by combining a shallow water flow model and an advection-diffusion equation for the transport of sediment. The proposed model has been applied to the lower reach of Abukuma River, which is the main river in the highly contaminated area around FDNPP. The numerical results indicate that most (137)Cs supplied from the upstream river reach with washload would directly reach to Pacific Ocean. In contrast, washload-oriented (137)Cs supplied from the upstream river basin has a limited role in the radioactive contamination in the river. The results also suggest that the proposed framework of computational model can be a potential tool for understanding the sediment-oriented (137)Cs behavior in rivers.

  11. Sediment Yields Revealed and Fluid Modelling by Twice LiDAR Surveys in Active Tectonics Area

    Science.gov (United States)

    Hsieh, Y.; Chan, Y.; Hu, J.; Lin, C.

    2010-12-01

    LiDAR technique allows rapid acquisition of high resolution and high precision topographic data. The technique has found considerable use in the earth sciences, for example for fluvial morphology and flood modelling. These developments have offered new opportunities for investigating spatial and temporal patterns of morphological change in gravel-bed river and have contributed to develop in two points: (1)morphometric estimates of sediment transport and sediment yields ;(2)boundary conditions for numerical models, including computational fluid dynamics and modelling. This topographic research funded by the Taiwan Central Geological Survey, surveyed the terrain of the Lanyang River before and after the typhoon season using Airborne LiDAR technique, and computed the terrain variations. The Lanyang River is one of main rivers in Taiwan and often suffers the influence of typhoon during summer. Most of sediments generated from slump and soil erosion into river were transported from the upstream watershed and resulted in the riverbed changes during the typhoon season. In 2008, there are four significant typhoon events influencing this area, including the Kalmaegi, Fung-wong, Sinlaku, and Jangmi typhoons. At present, sediment yield calculation often used empirical or theoretical formula as well as data collected at hydrological stations, and rarely had the actual measured value through high-resolution topography. The variations of the terrain on the riverbed may be regarded as the sediment yield of the bed load transported during the typhoon season. This research used high-resolution terrain models to compute sediment yield of the bed load, and further discussed volumes of sediment yield in watershed during the typhoon season. In the Lanyang River we discovered that the upstream and midstream channel still had the characteristics of erosion and transportation during the typhoon season. The results imply significant sediment yield and transportation from the upstream

  12. Phosphorus dynamics in lake sediments: Insights from field study and reactive-transport modeling

    Science.gov (United States)

    Dittrich, Maria; Markovic, Stefan; Cadena, Sandra; Doan, Phuong T. K.; Watson, Sue; Mugalingam, Shan

    2016-04-01

    Phosphorus is an indispensable nutrient for organisms in aquatic systems and its availability often controls primary productivity. At the sediment-water interface, intensive microbiological, geochemical and physical processes determine the fraction of organic matter, nutrients and pollutants released into the overlying water. Therefore, detailed understanding of the processes occurring in the top centimeters of the sediment is essential for the assessment of water quality and the management of surface waters. In cases where measurements are impossible or expensive, diagenetic modelling is required to investigate the interplay among the processes, verify concepts and predict potential system behavior. The main aims of this study are to identify and predict the dynamics of phosphorus (P) in sediments and gain insight into the mechanism of P release from sediments under varying environmental conditions. We measured redox, O2 and pH profiles with micro-sensors at the sediment-water interface; analyzed phosphate and metals (Fe, Mn, Al, Ca) content in pore waters collected using in situ samplers, so called "peepers"; determined P binding forms using sequential extraction and analyzed metals associated with each fraction. Following the sediment analysis, P binding forms were divided in five groups: inert, carbonate-bound, organic, redox-sensitive, and labile P. Using the flux of organic and inorganic matter as dynamic boundary conditions, the diagenetic model simulates P internal loading and predicts P retention. This presentation will discuss the results of two years studies on P dynamics at the sediment-water interface in three different lakes ranging from heavy-polluted Hamilton Harbor and Bay of Quinte to pristine Georgian Bay in Ontario, Canada.

  13. Modeling of soil erosion and sediment transport in the East River Basin in southern China.

    Science.gov (United States)

    Wu, Yiping; Chen, Ji

    2012-12-15

    Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide.

  14. Modeling of soil erosion and sediment transport in the East River Basin in southern China

    Science.gov (United States)

    Wu, Yping; Chen, Ji

    2012-01-01

    Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide.

  15. CMS-Wave Model: Part 3: Grid Nesting and Application Example for Rhode Island South Shore Regional Sediment Management Study

    Science.gov (United States)

    2010-07-01

    grid nesting capability of the Coastal Modeling System ( CMS ) wave model CMS -Wave availa- ble in the U.S. Army Corps of Engineers (USACE) Surface-water...Martin, 2004). The motivation behind RISRSM is to identify the sediment pathways in a system at a regional scale for management of sediment based on...a system approach. The RISRSM is developing a management plan for sediments along the project study area that consists of a 38 km stretch of

  16. GISCOD: general integrated solid waste co-digestion model.

    Science.gov (United States)

    Zaher, Usama; Li, Rongping; Jeppsson, Ulf; Steyer, Jean-Philippe; Chen, Shulin

    2009-06-01

    This paper views waste as a resource and anaerobic digestion (AD) as an established biological process for waste treatment, methane production and energy generation. A powerful simulation tool was developed for the optimization and the assessment of co-digestion of any combination of solid waste streams. Optimization was aimed to determine the optimal ratio between different waste streams and hydraulic retention time by changing the digester feed rates to maximize the biogas production rate. Different model nodes based on the ADM1 were integrated and implemented on the Matlab-Simulink simulation platform. Transformer model nodes were developed to generate detailed input for ADM1, estimating the particulate waste fractions of carbohydrates, proteins, lipids and inerts. Hydrolysis nodes were modeled separately for each waste stream. The fluxes from the hydrolysis nodes were combined and generated a detailed input vector to the ADM1. The integrated model was applied to a co-digestion case study of diluted dairy manure and kitchen wastes. The integrated model demonstrated reliable results in terms of calibration and optimization of this case study. The hydrolysis kinetics were calibrated for each waste fraction, and led to accurate simulation results of the process and prediction of the biogas production. The optimization simulated 200,000 days of virtual experimental time in 8 h and determined the feedstock ratio and retention time to set the digester operation for maximum biogas production rate.

  17. Model Order Reduction for Fluid Dynamics with Moving Solid Boundary

    Science.gov (United States)

    Gao, Haotian; Wei, Mingjun

    2016-11-01

    We extended the application of POD-Galerkin projection for model order reduction from usual fixed-domain problems to more general fluid-solid systems when moving boundary/interface is involved. The idea is similar to numerical simulation approaches using embedded forcing terms to represent boundary motion and domain change. However, such a modified approach will not get away with the unsteadiness of boundary terms which appear as time-dependent coefficients in the new Galerkin model. These coefficients need to be pre-computed for prescribed motion, or worse, to be computed at each time step for non-prescribed motion. The extra computational cost gets expensive in some cases and eventually undermines the value of using reduced-order models. One solution is to decompose the moving boundary/domain to orthogonal modes and derive another low-order model with fixed coefficients for boundary motion. Further study shows that the most expensive integrations resulted from the unsteady motion (in both original and domain-decomposition approaches) have almost negligible impact on the overall dynamics. Dropping these expensive terms reduces the computation cost by at least one order while no obvious effect on model accuracy is noticed. Supported by ARL.

  18. Dynamic spreading of nanofluids on solids part II: modeling.

    Science.gov (United States)

    Liu, Kuan-Liang; Kondiparty, Kirtiprakash; Nikolov, Alex D; Wasan, Darsh

    2012-11-27

    Recent studies on the spreading phenomena of liquid dispersions of nanoparticles (nanofluids) have revealed that the self-layering and two-dimensional structuring of nanoparticles in the three-phase contact region exert structural disjoining pressure, which drives the spreading of nanofluids by forming a continuous wedge film between the liquid (e.g., oil) and solid surface. Motivated by the practical applications of the phenomenon and experimental results reported in Part I of this two-part series, we thoroughly investigated the spreading dynamics of nanofluids against an oil drop on a solid surface. With the Laplace equation as a starting point, the spreading process is modeled by Navier-Stokes equations through the lubrication approach, which considers the structural disjoining pressure, gravity, and van der Waals force. The temporal interface profile and advancing inner contact line velocity of nanofluidic films are analyzed through varying the effective nanoparticle concentration, the outer contact angle, the effective nanoparticle size, and capillary pressure. It is found that a fast and spontaneous advance of the inner contact line movement can be obtained by increasing the nanoparticle concentration, decreasing the nanoparticle size, and/or decreasing the interfacial tension. Once the nanofluidic film is formed, the advancing inner contact line movement reaches a constant velocity, which is independent of the outer contact angle if the interfacial tension is held constant.

  19. Turbidity and Suspended Solids Levels and Loads in a Sediment Enriched Stream: Implications for Impacted Lotic and Lentic Ecosystems

    Science.gov (United States)

    2007-01-01

    remotely by commands delivered by use (-80% forest, rural and agriculture and -20% urban) a base station computer via phone (Fig. 2b). Collected data...Barko. 1997. Net and gross sedimentation 30-May 2, 2002. in relation to the phosphorus budget of Eau Galle Reservoir. Davies-Colley, R.J. and D.G. Smith

  20. Improving sediment-quality guidelines for nickel: development and application of predictive bioavailability models to assess chronic toxicity of nickel in freshwater sediments

    Science.gov (United States)

    Vangheluwe, Marnix L. U.; Verdonck, Frederik A. M.; Besser, John M.; Brumbaugh, William G.; Ingersoll, Christopher G.; Schlekat, Christan E.; Rogevich Garman, Emily

    2013-01-01

    Within the framework of European Union chemical legislations an extensive data set on the chronic toxicity of sediment nickel has been generated. In the initial phase of testing, tests were conducted with 8 taxa of benthic invertebrates in 2 nickel-spiked sediments, including 1 reasonable worst-case sediment with low concentrations of acid-volatile sulfide (AVS) and total organic carbon. The following species were tested: amphipods (Hyalella azteca, Gammarus pseudolimnaeus), mayflies (Hexagenia sp.), oligochaetes (Tubifex tubifex, Lumbriculus variegatus), mussels (Lampsilis siliquoidea), and midges (Chironomus dilutus, Chironomus riparius). In the second phase, tests were conducted with the most sensitive species in 6 additional spiked sediments, thus generating chronic toxicity data for a total of 8 nickel-spiked sediments. A species sensitivity distribution was elaborated based on 10% effective concentrations yielding a threshold value of 94 mg Ni/kg dry weight under reasonable worst-case conditions. Data from all sediments were used to model predictive bioavailability relationships between chronic toxicity thresholds (20% effective concentrations) and AVS and Fe, and these models were used to derive site-specific sediment-quality criteria. Normalization of toxicity values reduced the intersediment variability in toxicity values significantly for the amphipod species Hyalella azteca and G. pseudolimnaeus, but these relationships were less clearly defined for the mayfly Hexagenia sp. Application of the models to prevailing local conditions resulted in threshold values ranging from 126 mg to 281 mg Ni/kg dry weight, based on the AVS model, and 143 mg to 265 mg Ni/kg dry weight, based on the Fe model

  1. Spatial variability in floodplain sedimentation: the use of generalized linear mixed-effects models

    Science.gov (United States)

    Cabezas, A.; Angulo-Martínez, M.; Gonzalez-Sanchís, M.; Jimenez, J. J.; Comín, F. A.

    2010-08-01

    Sediment, Total Organic Carbon (TOC) and total nitrogen (TN) accumulation during one overbank flood (1.15 y return interval) were examined at one reach of the Middle Ebro River (NE Spain) for elucidating spatial patterns. To achieve this goal, four areas with different geomorphological features and located within the study reach were examined by using artificial grass mats. Within each area, 1 m2 study plots consisting of three pseudo-replicates were placed in a semi-regular grid oriented perpendicular to the main channel. TOC, TN and Particle-Size composition of deposited sediments were examined and accumulation rates estimated. Generalized linear mixed-effects models were used to analyze sedimentation patterns in order to handle clustered sampling units, specific-site effects and spatial self-correlation between observations. Our results confirm the importance of channel-floodplain morphology and site micro-topography in explaining sediment, TOC and TN deposition patterns, although the importance of other factors as vegetation pattern should be included in further studies to explain small-scale variability. Generalized linear mixed-effect models provide a good framework to deal with the high spatial heterogeneity of this phenomenon at different spatial scales, and should be further investigated in order to explore its validity when examining the importance of factors such as flood magnitude or suspended sediment concentration.

  2. Modeled tephra ages from lake sediments, base of Redoubt Volcano, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Schiff, C J; Kaufman, D S; Wallace, K L; Werner, A; Ku, T L; Brown, T A

    2007-02-25

    A 5.6-m-long lake sediment core from Bear Lake, Alaska, located 22 km southeast of Redoubt Volcano, contains 67 tephra layers deposited over the last 8750 cal yr, comprising 15% of the total thickness of recovered sediment. Using 12 AMS {sup 14}C ages, along with the {sup 137}Cs and {sup 210}Pb activities of recent sediment, we evaluated different models to determine the age-depth relation of sediment, and to determine the age of each tephra deposit. The age model is based on a cubic smooth spline function that was passed through the adjusted tephra-free depth of each dated layer. The estimated age uncertainty of the 67 tephras averages {+-} 105 yr (1{sigma}). Tephra-fall frequency at Bear Lake was among the highest during the past 500 yr, with eight tephras deposited compared to an average of 3.7 per 500 yr over the last 8500 yr. Other periods of increased tephra fall occurred 2500-3500, 4500-5000, and 7000-7500 cal yr. Our record suggests that Bear Lake experienced extended periods (1000-2000 yr) of increased tephra fall separated by shorter periods (500-1000 yr) of apparent quiescence. The Bear Lake sediment core affords the most comprehensive tephrochronology from the base of the Redoubt Volcano to date, with an average tephra-fall frequency of once every 130 yr.

  3. Mathematical model of sediment and solute transport along slope land in different rainfall pattern conditions

    Science.gov (United States)

    Tao, Wanghai; Wu, Junhu; Wang, Quanjiu

    2017-03-01

    Rainfall erosion is a major cause of inducing soil degradation, and rainfall patterns have a significant influence on the process of sediment yield and nutrient loss. The mathematical models developed in this study were used to simulate the sediment and nutrient loss in surface runoff. Four rainfall patterns, each with a different rainfall intensity variation, were applied during the simulated rainfall experiments. These patterns were designated as: uniform-type, increasing-type, increasing- decreasing -type and decreasing-type. The results revealed that changes in the rainfall intensity can have an appreciable impact on the process of runoff generation, but only a slight effect on the total amount of runoff generated. Variations in the rainfall intensity in a rainfall event not only had a significant effect on the process of sediment yield and nutrient loss, but also the total amount of sediment and nutrient produced, and early high rainfall intensity may lead to the most severe erosion and nutrient loss. In this study, the calculated data concur with the measured values. The model can be used to predict the process of surface runoff, sediment transport and nutrient loss associated with different rainfall patterns.

  4. Review of Solid Propellant Ignition Models Relative to the Interior Ballistic Modelling of Gun Systems

    Science.gov (United States)

    2012-08-01

    the point of phase change is reached. Solid-phase exothermic reactions may occur in some propellant ingredients (such as AP [9] or ADN [4]) leading...M.L. Gross. Two-dimensional modeling of AP/HTPB utilizing a vorticity formula- tion and one-dimensional modeling of AP and ADN . PhD thesis, Brigham

  5. Evaluation of solid polymeric organic materials for use in bioreactive sediment capping to stimulate the degradation of chlorinated aliphatic hydrocarbons

    NARCIS (Netherlands)

    Atashgahi, S.; Maphosa, F.; Vrieze, de J.; Haest, P.J.; Boon, N.; Smidt, H.; Springael, D.; Dejonghe, W.

    2014-01-01

    In situ bioreactive capping is a promising technology for mitigation of surface water contamination by discharging polluted groundwater. Organohalide respiration (OHR) of chlorinated ethenes in bioreactive caps can be stimulated through incorporation of solid polymeric organic materials (SPOMs) that

  6. Evaluation of solid polymeric organic materials for use in bioreactive sediment capping to stimulate the degradation of chlorinated aliphatic hydrocarbons

    NARCIS (Netherlands)

    Atashgahi, S.; Maphosa, F.; Vrieze, de J.; Haest, P.J.; Boon, N.; Smidt, H.; Springael, D.; Dejonghe, W.

    2014-01-01

    In situ bioreactive capping is a promising technology for mitigation of surface water contamination by discharging polluted groundwater. Organohalide respiration (OHR) of chlorinated ethenes in bioreactive caps can be stimulated through incorporation of solid polymeric organic materials (SPOMs) that

  7. How sedimentation affects rift segment interaction during oblique extension: a 4D analogue modelling study

    Science.gov (United States)

    Zwaan, Frank; Schreurs, Guido; Adam, Jürgen

    2017-04-01

    During the early stages of rifting, rift segments may form along non-continuous and/or offset pre-existing weaknesses. It is important to understand how these initial rift segments interact and connect to form a continuous rift system. Previous modelling of rift interaction structures has shown the dominant influence of oblique extension, promoting rift segment linkage (e.g. Zwaan et al., 2016) and eventual continent break-up (Brune et al., 2012). However, these studies did not incorporate sedimentation, which can have important implications for rift evolution (e.g. Bialas and Buck, 2009). Here we present a series of analogue model experiments investigating the influence of sedimentation on rift interaction structures under oblique extension conditions. Our set-up involves a base of compressed foam and plexiglass that forces distributed extension in the overlying analogue materials when the model sidewalls move apart. A sand layer simulates the brittle upper crust and a viscous sand/silicone mixture the ductile lower crust. One of the underlying base plates can move laterally allowing oblique extension. Right-stepping offset and disconnected lines of silicone (seeds) on top of the basal viscous serve as inherited structures since the strong sand cover is locally thinner. We apply syn-rift sediments by filling in the developing rift and transfer zone basins with sand at fixed time steps. Models are run either with sedimentation or without to allow comparison. The first results suggest that the gross structures are similar with or without sedimentation. As seen by Zwaan et al. (2016), dextral oblique extension promotes rift linkage because rift propagation aligns itself perpendicular to the extension direction. This causes the rift segments to grow towards each other and to establish a continuous rift structure. However, the structures within the rift segments show quite different behaviour when sedimentation is applied. The extra sediment loading in the rift basin

  8. Runoff and sediment yield modeling in a medium-size mediterranean watershed

    Directory of Open Access Journals (Sweden)

    Ossama M.M. Abdelwahab

    2013-09-01

    Full Text Available The AnnAGNPS model was used to estimate runoff, peak discharge and sediment yield at the event scale in the Carapelle watershed, a Mediterranean medium-size watershed (506 km2 located in Apulia, Southern Italy. The model was calibrated and validated using five years of runoff and sediment yield data measured at a monitoring station located at Ordona – Ponte dei Sauri Bridge. A total of 36 events was used to estimate the output of the model during the period 2007-2011, in comparison to the corresponding observations at the watershed outlet. The model performed well in predicting runoff, as was testified by the high values of the coefficients of efficiency and determination during the validation process. The peak flows predictions were satisfactory especially for the high flow events; the prediction capability of sediment yield was good, even if a slight over-estimation was observed. Finally, the model was used to evaluate the effectiveness of different Management practices (MPs on the watershed (converting wheat to forest, using vegetated streams, crop rotation corn/soybean, no tillage. While the maximum reduction in sediment yield was achieved converting wheat to forest, the best compromises between soil conservation and agriculture resulted to be crop rotations.

  9. State-of-the-Art Solid Waste Management Life-Cycle Modeling Workshop

    DEFF Research Database (Denmark)

    Damgaard, Anders; Levis, James W.

    There are many alternatives for the management of solid waste including recycling, biological treatment, thermal treatment and landfill disposal. In many cases, solid waste management systems include the use of several of these processes. Solid waste life-cycle assessment models are often used...... to evaluate the environmental consequences of various waste management strategies. The foundation of every life-cycle model is the development and use of process models to estimate the emissions from solid waste unit processes. The objective of this workshop is to describe life-cycle modeling of the solid...... waste processes and systems. The workshop will begin with an introduction to solid waste life-cycle modeling and available models, which will be followed by sessions on life-cycle process modeling for individual processes (e.g., landfills, biological treatment, and thermal treatment). The first part...

  10. Dynamic modeling of environmental risk associated with drilling discharges to marine sediments.

    Science.gov (United States)

    Durgut, İsmail; Rye, Henrik; Reed, Mark; Smit, Mathijs G D; Ditlevsen, May Kristin

    2015-10-15

    Drilling discharges are complex mixtures of base-fluids, chemicals and particulates, and may, after discharge to the marine environment, result in adverse effects on benthic communities. A numerical model was developed to estimate the fate of drilling discharges in the marine environment, and associated environmental risks. Environmental risk from deposited drilling waste in marine sediments is generally caused by four types of stressors: oxygen depletion, toxicity, burial and change of grain size. In order to properly model these stressors, natural burial, biodegradation and bioturbation processes were also included. Diagenetic equations provide the basis for quantifying environmental risk. These equations are solved numerically by an implicit-central differencing scheme. The sediment model described here is, together with a fate and risk model focusing on the water column, implemented in the DREAM and OSCAR models, both available within the Marine Environmental Modeling Workbench (MEMW) at SINTEF in Trondheim, Norway.

  11. Spatially distributed modeling of sediment and associated heavy metal transport on regional and catchment scale

    Science.gov (United States)

    Schindewolf, Marcus; Schmidt, Jürgen; Käpermann, Philipp

    2013-04-01

    Achievements of new legislations, as EU-Water Framework Directive (EU-WFD), require great efforts in order to reduce the yields of sediment and sediment attached heavy metals of surface water bodies. In this regard planning authorities strongly need comparable assessments on regional scale, which enables predictions on the level of measures. The study aims to identify the main sediment delivery areas in the German federal state of Saxony (18400 km²) and to locate pass over points of sediment and associated heavy metals into surface waters. Applying the process based EROSION 3D simulation model spatially distributed (20 m grid cell) estimates of sediment and particle attached heavy metal inputs are realized on regional and catchment scale related to three land use scenarios and a 10years rainfall event. Concerning these calculations it has to be considered, that this substances are predominantly attached to the fine-grained soil particles. The selective nature of soil erosion causes a preferentially transport of this fine particles while less contaminated larger particles remain on site. Consequently heavy metals are enriched in the eroded sediment compared to the origin soil. Hence it is essential that EROSION 3D provides the particle size distribution (clay, silt and sand) of transported sediments. Regarding heavy metal input calculations from sediment inputs, heavy metal contents of particle size classes has to be known. For this purpose particle size separates of erosion susceptible soils are analyzed. Comprehensive heavy metal contents of origin top soils are interpolated via kriging using available monitoring data. The regional scaled simulations identify the Saxon loess belt as the main affected region of sediment inputs. Since particle attached heavy metal transport to surface waters is strongly related to sediment delivery, the streams of this region suffer from considerable inputs. Compared to empirical estimates, the results of this study suggest that

  12. Modeling polychlorinated biphenyl mass transfer after amendment of contaminated sediment with activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    David Werner; Upal Ghosh; Richard G. Luthy [University of Newcastle upon Tyne, Newcastle (United Kingdom)

    2006-07-01

    The sorption kinetics and concentration of polychlorinated biphenyls (PCBs) in historically polluted sediment is modeled to assess a remediation strategy based on in situ PCB sequestration by mixing with activated carbon (AC). The authors extend their evaluation of a model based on intraparticle diffusion by including a biomimetic semipermeable membrane device (SPMD) and a first-order degradation rate for the aqueous phase. The model predictions are compared with the previously reported experimental PCB concentrations in the bulk water phase and in SPMDs. The simulated scenarios comprise a marine and a freshwater sediment, four PCB congeners, two AC grain sizes, four doses of AC, and comparison with laboratory experiments. The modeling approach distinguishes between two different sediment particles types: a light-density fraction representing carbonaceous particles such as charcoal, coal, coke, cenospheres, or wood, and a heavy-density fraction representing the mineral phase with coatings of organic matter. A third particle type in the numerical model is AC. The model qualitatively reproduces the observed shifts in the PCB distribution during repartitioning after AC amendment but overestimates the overall effect of the treatment in reducing aqueous and SPMD concentrations of PCBs by a factor of 2-6. For the AC application in sediment, competitive sorption of the various solutes apparently requires a reduction by a factor of 16 of the literature values for the AC-water partitioning coefficient measured in pure aqueous systems. With this correction, model results and measurements agree within a factor of 3. After AC amendment is homogeneously mixed into the sediment and then left undisturbed, aqueous PCB concentrations tend toward the same reduction after 5 years. 19 refs., 5 figs., 4 tabs.

  13. Automatic paper sliceform design from 3D solid models.

    Science.gov (United States)

    Le-Nguyen, Tuong-Vu; Low, Kok-Lim; Ruiz, Conrado; Le, Sang N

    2013-11-01

    A paper sliceform or lattice-style pop-up is a form of papercraft that uses two sets of parallel paper patches slotted together to make a foldable structure. The structure can be folded flat, as well as fully opened (popped-up) to make the two sets of patches orthogonal to each other. Automatic design of paper sliceforms is still not supported by existing computational models and remains a challenge. We propose novel geometric formulations of valid paper sliceform designs that consider the stability, flat-foldability and physical realizability of the designs. Based on a set of sufficient construction conditions, we also present an automatic algorithm for generating valid sliceform designs that closely depict the given 3D solid models. By approximating the input models using a set of generalized cylinders, our method significantly reduces the search space for stable and flat-foldable sliceforms. To ensure the physical realizability of the designs, the algorithm automatically generates slots or slits on the patches such that no two cycles embedded in two different patches are interlocking each other. This guarantees local pairwise assembility between patches, which is empirically shown to lead to global assembility. Our method has been demonstrated on a number of example models, and the output designs have been successfully made into real paper sliceforms.

  14. Modeling Degradation in Solid Oxide Electrolysis Cells - Volume II

    Energy Technology Data Exchange (ETDEWEB)

    Manohar Motwani

    2011-09-01

    Idaho National Laboratory has an ongoing project to generate hydrogen from steam using solid oxide electrolysis cells (SOECs). To accomplish this, technical and degradation issues associated with the SOECs will need to be addressed. This report covers various approaches being pursued to model degradation issues in SOECs. An electrochemical model for degradation of SOECs is presented. The model is based on concepts in local thermodynamic equilibrium in systems otherwise in global thermodynamic non-equilibrium. It is shown that electronic conduction through the electrolyte, however small, must be taken into account for determining local oxygen chemical potential,, within the electrolyte. The within the electrolyte may lie out of bounds in relation to values at the electrodes in the electrolyzer mode. Under certain conditions, high pressures can develop in the electrolyte just near the oxygen electrode/electrolyte interface, leading to oxygen electrode delamination. These predictions are in accordance with the reported literature on the subject. Development of high pressures may be avoided by introducing some electronic conduction in the electrolyte. By combining equilibrium thermodynamics, non-equilibrium (diffusion) modeling, and first-principles, atomic scale calculations were performed to understand the degradation mechanisms and provide practical recommendations on how to inhibit and/or completely mitigate them.

  15. Multiscale approach to modeling intrinsic dissipation in solids

    Science.gov (United States)

    Kunal, K.; Aluru, N. R.

    2016-08-01

    In this paper, we develop a multiscale approach to model intrinsic dissipation under high frequency of vibrations in solids. For vibrations with a timescale comparable to the phonon relaxation time, the local phonon distribution deviates from the equilibrium distribution. We extend the quasiharmonic (QHM) method to describe the dynamics under such a condition. The local deviation from the equilibrium state is characterized using a nonequilibrium stress tensor. A constitutive relation for the time evolution of the stress component is obtained. We then parametrize the evolution equation using the QHM method and a stochastic sampling approach. The stress relaxation dynamics is obtained using mode Langevin dynamics. Methods to obtain the input variables for the Langevin dynamics are discussed. The proposed methodology is used to obtain the dissipation rate Edissip for different cases. Frequency and size effect on Edissip are studied. The results are compared with those obtained using nonequilibrium molecular dynamics (MD).

  16. A conceptual model of pore-space blockage in mixed sediments using a new numerical approach, with implications for sediment bed stabilization

    Science.gov (United States)

    Bartzke, Gerhard; Huhn, Katrin

    2015-06-01

    In mixed sediment beds, erosion resistance can change relative to that of beds composed of a uniform sediment because of varying textural and/or other grain-size parameters, with effects on pore water flow that are difficult to quantify by means of analogue techniques. To overcome this difficulty, a three-dimensional numerical model was developed using a finite difference method (FDM) flow model coupled with a distinct element method (DEM) particle model. The main aim was to investigate, at a high spatial resolution, the physical processes occurring during the initiation of motion of single grains at the sediment-water interface and in the shallow subsurface of simplified sediment beds under different flow velocities. Increasing proportions of very fine sand (D50=0.08 mm) were mixed into a coarse sand matrix (D50=0.6 mm) to simulate mixed sediment beds, starting with a pure coarse sand bed in experiment 1 (0 wt% fines), and proceeding through experiment 2 (6.5 wt% fines), experiment 3 (10.5 wt% fines), and experiment 4 (28.7 wt% fines). All mixed beds were tested for their erosion behavior at predefined flow velocities varying in the range of U 1-5=10-30 cm/s. The experiments show that, with increasing fine content, the smaller particles increasingly fill the spaces between the larger particles. As a consequence, pore water inflow into the sediment is increasingly blocked, i.e., there is a decrease in pore water flow velocity and, hence, in the flow momentum available to entrain particles. These findings are portrayed in a new conceptual model of enhanced sediment bed stabilization.

  17. Assessing sediment hazard through a weight of evidence approach with bioindicator organisms: a practical model to elaborate data from sediment chemistry, bioavailability, biomarkers and ecotoxicological bioassays.

    Science.gov (United States)

    Piva, Francesco; Ciaprini, Francesco; Onorati, Fulvio; Benedetti, Maura; Fattorini, Daniele; Ausili, Antonella; Regoli, Francesco

    2011-04-01

    Quality assessments are crucial to all activities related to removal and management of sediments. Following a multidisciplinary, weight of evidence approach, a new model is presented here for comprehensive assessment of hazards associated to polluted sediments. The lines of evidence considered were sediment chemistry, assessment of bioavailability, sub-lethal effects on biomarkers, and ecotoxicological bioassays. A conceptual and software-assisted model was developed with logical flow-charts elaborating results from each line of evidence on the basis of several chemical and biological parameters, normative guidelines or scientific evidence; the data are thus summarized into four specific synthetic indices, before their integration into an overall sediment hazard evaluation. This model was validated using European eels (Anguilla anguilla) as the bioindicator species, exposed under laboratory conditions to sediments from an industrial site, and caged under field conditions in two harbour areas. The concentrations of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons and trace metals were much higher in the industrial compared to harbour sediments, and accordingly the bioaccumulation in liver and gills of exposed eels showed marked differences between conditions seen. Among biomarkers, significant variations were observed for cytochrome P450-related responses, oxidative stress biomarkers, lysosomal stability and genotoxic effects; the overall elaboration of these data, as those of standard ecotoxicological bioassays with bacteria, algae and copepods, confirmed a higher level of biological hazard for industrial sediments. Based on comparisons with expert judgment, the model presented efficiently discriminates between the various conditions, both as individual modules and as an integrated final evaluation, and it appears to be a powerful tool to support more complex processes of environmental risk assessment.

  18. A Model of Solid Waste Management Based Multilateral Co-Operation in Semi-Urban Community

    Science.gov (United States)

    Kanchanabhandhu, Chanchai; Woraphong, Seree

    2016-01-01

    The purpose of this research was to construct a model of solid waste management based on multilateral cooperation in semi-urban community. Its specific objectives were to 1) study the solid waste situation and involvement of community in the solid waste management in Wangtaku Sub-district, Muang District, Nakhon Pathom Province; 2) construct a…

  19. Sediment-hosted gold deposits of the world: database and grade and tonnage models

    Science.gov (United States)

    Berger, Vladimir I.; Mosier, Dan L.; Bliss, James D.; Moring, Barry C.

    2014-01-01

    All sediment-hosted gold deposits (as a single population) share one characteristic—they all have disseminated micron-sized invisible gold in sedimentary rocks. Sediment-hosted gold deposits are recognized in the Great Basin province of the western United States and in China along with a few recognized deposits in Indonesia, Iran, and Malaysia. Three new grade and tonnage models for sediment-hosted gold deposits are presented in this paper: (1) a general sediment-hosted gold type model, (2) a Carlin subtype model, and (3) a Chinese subtype model. These models are based on grade and tonnage data from a database compilation of 118 sediment-hosted gold deposits including a total of 123 global deposits. The new general grade and tonnage model for sediment-hosted gold deposits (n=118) has a median tonnage of 5.7 million metric tonnes (Mt) and a gold grade of 2.9 grams per tonne (g/t). This new grade and tonnage model is remarkable in that the estimated parameters of the resulting grade and tonnage distributions are comparable to the previous model of Mosier and others (1992). A notable change is in the reporting of silver in more than 10 percent of deposits; moreover, the previous model had not considered deposits in China. From this general grade and tonnage model, two significantly different subtypes of sediment-hosted gold deposits are differentiated: Carlin and Chinese. The Carlin subtype includes 88 deposits in the western United States, Indonesia, Iran, and Malaysia, with median tonnage and grade of 7.1 Mt and 2.0 g/t Au, respectively. The silver grade is 0.78 g/t Ag for the 10th percentile of deposits. The Chinese subtype represents 30 deposits in China, with a median tonnage of 3.9 Mt and medium grade of 4.6 g/t Au. Important differences are recognized in the mineralogy and alteration of the two sediment-hosted gold subtypes such as: increased sulfide minerals in the Chinese subtype and decalcification alteration dominant in the Carlin type. We therefore

  20. Tidal-scale flow routing and sedimentation in mangrove forests: Combining field data and numerical modelling

    Science.gov (United States)

    Horstman, E. M.; Dohmen-Janssen, C. M.; Bouma, T. J.; Hulscher, S. J. M. H.

    2015-01-01

    Tidal-scale biophysical interactions establish particular flow routing and sedimentation patterns in coastal mangroves. Sluggish water flows through the mangrove vegetation and enhanced sediment deposition are essential to maintain these valuable ecosystems, thereby enabling their contribution to coastal protection and stabilization. Spatially explicit field observations of tidal-scale flow routing and sediment deposition were obtained in an elevated mangrove stand dissected by tidal creeks, located in the Trang river estuary at the Thai Andaman coast. An accurate and efficient depth-averaged process-based numerical model of this field site was developed in Delft3D to study the contributions of various biogeophysical mangrove settings to the observed tidal dynamics and to study the impacts of changes of these environmental conditions. The creeks are found to form the major pathway for the tidal inflow during the lower tides, while the sheltered interior of the forest is an effective sediment sink during the higher tides. A numerical sensitivity analysis of the initial response-or adaptive capacity-of the studied mangrove system to instantaneous environmental changes reveals the stable state of the study site: deposition rates are largely imposed by the topography and relative elevation, while they are rather independent of the vegetation density. Deeper inundations of the mangroves favor sheet flows through the forest and spatially averaged deposition rates decrease, particularly when this coincides with decreasing vegetation densities. Moreover, the sediment trapping efficiency is found to reduce significantly with diminishing sediment inputs and with mangrove area losses. These results clearly indicate the sensitivity of mangroves' ecosystem engineering ability-in terms of sedimentation-to climate change and anthropogenic threats.

  1. Dynamic linear models to explore time-varying suspended sediment-discharge rating curves

    Science.gov (United States)

    Ahn, Kuk-Hyun; Yellen, Brian; Steinschneider, Scott

    2017-06-01

    This study presents a new method to examine long-term dynamics in sediment yield using time-varying sediment-discharge rating curves. Dynamic linear models (DLMs) are introduced as a time series filter that can assess how the relationship between streamflow and sediment concentration or load changes over time in response to a wide variety of natural and anthropogenic watershed disturbances or long-term changes. The filter operates by updating parameter values using a recursive Bayesian design that responds to 1 day-ahead forecast errors while also accounting for observational noise. The estimated time series of rating curve parameters can then be used to diagnose multiscale (daily-decadal) variability in sediment yield after accounting for fluctuations in streamflow. The technique is applied in a case study examining changes in turbidity load, a proxy for sediment load, in the Esopus Creek watershed, part of the New York City drinking water supply system. The results show that turbidity load exhibits a complex array of variability across time scales. The DLM highlights flood event-driven positive hysteresis, where turbidity load remained elevated for months after large flood events, as a major component of dynamic behavior in the rating curve relationship. The DLM also produces more accurate 1 day-ahead loading forecasts compared to other static and time-varying rating curve methods. The results suggest that DLMs provide a useful tool for diagnosing changes in sediment-discharge relationships over time and may help identify variability in sediment concentrations and loads that can be used to inform dynamic water quality management.

  2. Implications of sediment redistribution on modeled sea-level changes over millennial timescales

    Science.gov (United States)

    Ferrier, Ken

    2016-04-01

    Sea level is a critical link in feedbacks among topography, tectonics, and climate. Over millennial timescales, changes in sea level reshape river networks, regulate organic carbon burial, influence sediment deposition, and set moving boundary conditions for landscape evolution. Sea-level changes influence tectonics by regulating rates and patterns of erosion and deposition, which perturb the surface loads that drive geodynamic processes at depth. These interactions are complex because sea-level changes are influenced by the geomorphic processes that they themselves modify, since sediment redistribution deforms the gravitational and crustal elevation fields that define sea level. A recent advance in understanding the coupling between sea level, tectonics, and topography was the incorporation of sediment redistribution into a gravitationally self-consistent sea-level model, which permits the computation of sea-level responses to erosion and deposition (Dalca et al., 2013, Geophysical Journal International). Here I use this model to quantify changes in sea level resulting from the erosion of some of the most rapidly eroding sites on Earth and the deposition of sediment offshore. These model results show that the sea-level fingerprints of sediment redistribution are strongly variable in space, and that they can represent a significant component of the total sea level change since the last interglacial. This work provides a basis for understanding a fundamental driver of landscape evolution at some of Earth's most geomorphically dynamic sites, and thus aids investigation of the couplings among tectonics, climate, and topography. References Dalca A.V., Ferrier K.L., Mitrovica J.X., Perron J.T., Milne G.A., Creveling J.R., 2013. On postglacial sea level - III. Incorporating sediment redistribution. Geophysical Journal International, doi: 10.1093/gji/ggt089.

  3. INTEGRATION OF THE MODELS OF ANNAGNPS AND REMM TO ASSESS RIPARIAN BUFFER SYSTEM FOR SEDIMENT REDUCTION

    Institute of Scientific and Technical Information of China (English)

    Yongping YUAN; Ronald BINGNER; Randall WILLIAMS; Richard LOWRANCE; David BOSCH; Joe SHERIDAN

    2007-01-01

    The United States Department of Agriculture (USDA) Annualized Agricultural Non-Point Source Pollution model (AnnAGNPS) is used to help evaluate a watershed response to agricultural management practices to control water quality. However, AnnAGNPS version 3.5 does not contain features to estimate the effect of a riparian buffer (RB) system on water quality. The Riparian Ecosystem Management Model (REMM) is used to simulate the impact of riparian buffer systems on water quality. However, frequently the lack of measured upland loadings that are required by REMM simulation limits the application of REMM. To address this data gap, a study was conducted to integrate AnnAGNPS with REMM for RB system simulation. AnnAGNPS was used to simulate water and sediment loadings from an upland field into a three-zone RB system at the Gibbs Farm located in the Georgia coastal plain. These AnnAGNPS outputs were used as the inputs to REMM. REMM was used to simulate water and sediment movement along the riparian buffers. The AnnAGNPS simulated amount of annual runoff at the edge of the field was close to observed amounts (Nash-Sutcliffe efficiency of 0.92). It is believed that a substantial portion of sand was removed from the runoff one meter into the grass buffer where the samplers were located; therefore, sand was excluded from the AnnAGNPS simulation for comparison with observed sediment. Excluding sand, the AnnAGNPS predicted amount of annual sediment matches the observed amount fairly well (Nash-Sutcliffe efficiency of 0.46). In addition, based on evaluating the percent reduction of sediment at each zonal interface, the AnnAGNPS/REMM model well simulated the function of the RB system to reduce sediment.

  4. Reconstructing a sediment pulse: Modeling the effect of placer mining on Fraser River, Canada

    Science.gov (United States)

    Ferguson, R. I.; Church, M.; Rennie, C. D.; Venditti, J. G.

    2015-07-01

    Gold mining along 525 km of the Fraser River between 1858 and 1909 added an estimated 1.1 × 108 t of tailings, half gravel and the rest finer, to the river's natural sediment load. We simulate the response using a 1-D multigrain size morphodynamic model. Since premining conditions are unknown and modern data are insufficient for tuning the process representation, we devised a novel modeling strategy which may be useful in other data-poor applications. We start the model from a smoothed version of the modern longitudinal profile with bed grain size distributions optimized to match alternative assumptions about natural sediment supply and compare runs that include mining with control runs that can be used to quantify the effects of deficiencies in process representation and initialization. Simulations with an appropriate choice of natural supply rate closely match the best available test data, which consist of a detailed 1952-1999 gravel budget for the distal part of the model domain. The simulations suggest that the main response to mining was rapid bed fining, which allowed a major increase in bed load transport rate with only slight (~0.1 m) mean aggradation within the mining region and most of the excess sediment exported well beyond the mountain front within the mining period or soon afterward. We compare this pattern of response by a large, powerful river with previous case studies of river adjustment to sediment supply change.

  5. A Non-Equilibrium Sediment Transport Model for Coastal Inlets and Navigation Channels

    Science.gov (United States)

    2011-01-01

    Navigation Channels Alejandro Sánchez† and Weiming Wu‡ ABSTRACT SANCHEZ, A. and WU, W., 2011. A Non-Equilibrium Sediment Transport Model...2009; accessed January 20, 2009). Nicholson, J.; Brøker, I.; Roelvink, J. A.; Price, D.; Tanguy, J. M., and Moreno , L., 1997. Intercomparison of

  6. COMPARISON OF THREE MODELS TO PREDICT ANNUAL SEDIMENT YIELD IN CARONI RIVER BASIN, VENEZUELA

    Directory of Open Access Journals (Sweden)

    Edilberto Guevara-Pérez

    2007-06-01

    Full Text Available Caroní River Basin is located in the south-eastern part of Venezuela; with an area of 92.000 km², 40% of which belongs to the main affluent, the Paragua River. Caroní basin is the source of 66% of energy of the country. About 85% of the hydro electrical energy is generated in Guri reservoir located in the lower part of the watershed. To take provisions to avoid the reservoir silting it is very important the study of sediment yield of the basin. In this paper result of three empirical sediment yield models: LangbeinSchumm, Universal Soil Loss Equation-USLE and Poesen, are compared with observed data from five sub basins with records of twenty to thirty years. Men values of sediment yield for low, middle and upper Caroní are of 27, 76, 17 t/km²-year, respectively; and 46 and 78 t/km²-year for low and upper Paragua sub basins are. Standard errors of estimates vary between 13 and 29 for Langbein-Schumm model; between 8 and 32 for USLE procedure; and between 9 and 79, for Poesen model. Sediment yield predictions by Langbein-Schumm model seem to the best in Caroní basin.

  7. COMPARISON OF THREE MODELS TO PREDICT ANNUAL SEDIMENT YIELD IN CARONI RIVER BASIN, VENEZUELA

    Directory of Open Access Journals (Sweden)

    Edilberto Guevara-Pérez

    2007-01-01

    Full Text Available Caroní River Basin is located in the south-eastern part of Venezuela; with an area of 92.000 km2, 40% of which belongs to the main affluent, the Paragua River. Caroní basin is the source of 66% of energy of the country. About 85% of the hydro electrical energy is generated in Guri reservoir located in the lower part of the watershed. To take provisions to avoid the reservoir silting it is very important the study of sediment yield of the basin. In this paper result of three empirical sediment yield models: Langbein- Schumm, Universal Soil Loss Equation-USLE and Poesen, are compared with observed data from five sub basins with records of twenty to thirty years. Men values of sediment yield for low, middle and upper Caroní are of 27, 76, 17 t/km2-year, respectively; and 46 and 78 t/km2-year for low and upper Paragua sub basins are. Standard errors of estimates vary between 13 and 29 for Langbein-Schumm model; between 8 and 32 for USLE procedure; and between 9 and 79, for Poesen model. Sediment yield predictions by Langbein-Schumm model seem to the best in Caroní basin.

  8. Quantitative analysis of anaerobic oxidation of methane (AOM) in marine sediments: a modeling perspective

    NARCIS (Netherlands)

    Regnier, P.; Dale, A.W.; Arndt, S.; LaRowe, D.E.; Mogollon, J.M.; Van Cappellen, P.

    2011-01-01

    Recent developments in the quantitativemodeling of methane dynamics and anaerobic oxidation of methane (AOM) in marine sediments are critically reviewed. The first part of the review begins with a comparison of alternative kinetic models for AOM. The roles of bioenergetic limitations, intermediate c

  9. Experimental Research on Quantitative Inversion Models of Suspended Sediment Concentration Using Remote Sensing Technology

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Research on quantitative models of suspended sediment concentration (SSC) using remote sensing technology is very important to understand the scouring and siltation variation in harbors and water channels. Based on laboratory study of the relationship between different suspended sediment concentrations and reflectance spectra measured synchronously, quantitative inversion models of SSC based on single factor, band ratio and sediment parameter were developed, which provides an effective method to retrieve the SSC from satellite images. Results show that the b1 (430-500nm) and b3 (670-735nm) are the optimal wavelengths for the estimation of lower SSC and the b4 (780-835nm) is the optimal wavelength to estimate the higher SSC. Furthermore the band ratio B2/B3 can be used to simulate the variation of lower SSC better and the B4/B1 to estimate the higher SSC accurately. Also the inversion models developed by sediment parameters of higher and lower SSCs can get a relatively higher accuracy than the single factor and band ratio models.

  10. Model-based temperature measurement system development for marine methane hydrate-bearing sediments

    Energy Technology Data Exchange (ETDEWEB)

    Fukuhara, Masafumi; Sugiyama, Hitoshi; Igarashi, Juei; Fujii, Kasumi; Shun' etsu, Onodera; Tertychnyi, Vladimir; Shandrygin, Alexander; Pimenov, Viacheslav; Shako, Valery; Matsubayashi, Osamu; Ochiai, Koji

    2005-07-01

    This paper describes the effect of the sensor installation on the temperature of the hydrate-bearing sediments through modeling, how the system was deployed in Nankai Trough area in Japan, and the features of the marine methane hydrate temperature measurement system. (Author)

  11. Modeling the effect of nonuniform sediment on the dynamics of offshore tidal sandbanks

    NARCIS (Netherlands)

    Roos, Pieter C.; Wemmenhove, Rik; Hulscher, Suzanne J. M. H.; Hoeijmakers, Harry W. M.; Kruyt, N. P.

    2007-01-01

    [1] Tidal sandbanks are large-scale bed features present in many shallow shelf seas. Here we investigate the effect of nonuniform sediment on their dynamics, with a particular aim to explain observed surficial grain size variations over tidal sandbanks from a process-based modeling perspective. To t

  12. A Hybrid Approach to Combine Physically Based and Data-Driven Models in Simulating Sediment Transportation

    NARCIS (Netherlands)

    Sewagudde, S.

    2008-01-01

    The objective of this study is to develop a methodology for hybrid modelling of sedimentation in a coastal basin or large shallow lake where physically based and data driven approaches are combined. This research was broken down into three blocks. The first block explores the possibility of approxim

  13. Development of an integrated sediment transport model and application at a large gravel bed river

    Science.gov (United States)

    Tritthart, M.; Schober, B.; Liedermann, M.; Habersack, H.

    2009-04-01

    This paper presents the development, validation and application of iSed, an integrated numerical sediment transport and morphology model. The model was specifically designed to suit the needs of large gravel bed rivers, such as the Danube East of Vienna. It is coupled with external 2-D or 3-D hydrodynamic codes to obtain the flow field and bed shear stress patterns driving sediment transport processes. This approach is of particular advantage for an investigation into sediment dynamics based on hydrodynamics of different dimensionality. The model is capable of calculating both suspended and bed load transport. It solves a convection-diffusion equation to account for suspended load; in addition, four different transport formulae - the relations of Meyer-Peter/Müller, Hunziker, van Rijn and Egiazaroff - are implemented for the computation of bed load. The well-known Exner equation is solved for deriving resulting bed level differences for every node of the computation mesh based on the sediment balance. All equations are evaluated for an unlimited number of sediment size fractions, allowing for the investigation of sorting processes. The river bed is organized into an active layer, where sorting takes place, and an unlimited number of bed layers below the active layer. The sediment transport model was validated using results from three different laboratory experiments: (i) morphodynamics of a 180 degree channel bend, based on hydraulics of a 3-D numerical model; (ii) erosion and deposition patterns due to a channel contraction, using a 2-D model to provide the flow field; (iii) incipient motion and erosion processes due to different sediment materials in a straight laboratory channel, coupled with a 3-D numerical model. The results of the numerical code were in satisfactory agreement with the experimental measurements, demonstrating the general validity of the sediment transport model. After successful validation, the model was applied to a 4 kilometre reach of the

  14. Trace element-bearing phases during the solid transport: in-situ characterization and temporal variability in the Loire bed-sediments (France)

    Science.gov (United States)

    Grosbois, Cécile; Courtin-Nomade, Alexandra; Dhivert, Elie; Desmet, Marc; Kunz, Martin

    2013-04-01

    As a result of increased of agriculture, land use, urban areas, industry, traffic and population density, trace element inputs have altered considerably fluvial system (sediment, water quality and biota). The Loire River Basin (117,800 km2, total population of 8.4 Mp in 2010), even if it is considered one of the least human-impacted hydrosystem among the 5 large French basins, has been exposed to multiple sources of metals during the last 150 years, originating from major mining districts (coal and non-ferrous metals) and their associated industrial activities (Grosbois et al, 2012; Dhivert et al, 2013). Two major contamination periods