Numerical Model Research Papers - Academia.edu (original) (raw)

An intense low pressure system formed in the Bass Strait region of southeastern Australia during the Boxing Day long weekend of 25-28 December 1998. The explosive development of this low commenced on 26 December (Boxing Day) and reached peak intensity on 27 December 1998 with mean wind speeds reported in the 50-60kt range. The event is referred to, for simplicity, as the Boxing Day storm.

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- Sea surface temperature, Atmospheric sciences, Numerical Simulation, Weather Forecasting

The great ice sheets covering Antarctica and Greenland were, traditionally, believed to take thousands of years to respond to external forcing. Recent observations suggest, however, that major changes in the dynamics of parts of the ice sheets are taking place over timescales of years. These changes were not predicted by numerical models, and the underlying cause(s) remains uncertain. It has been suggested that regional oceanic and/or atmospheric warming are responsible but separating the influence and importance of these two forcings has not been possible. In most cases, the role of atmospheric versus oceanic control remains uncertain. Here, we review the observations of rapid change and discuss the possible mechanisms, in the light of advances in numerical modelling and our understanding of the processes that may be responsible.

- by Jonathan Bamber
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- Earth Sciences, Climate Change, Sea Level, Numerical Modelling

The St. Lawrence Lowlands platform, Quebec, Canada, is a densely-populated area, heavily dependent on groundwater resources. In 1999, the Geological Survey of Canada initiated a large-scale hydrogeological assessment study over a 1,500 km2 region northwest of Montreal. The objectives were to define the regional groundwater flow, and to give quantitative estimates of the groundwater dynamic parameters and of the available groundwater resources. The applied approach consisted of defining the hydrogeologic framework, hydraulic properties of the aquifer units, and groundwater dynamic components. Lower Paleozoic sedimentary rocks represent regional aquifer units. Coarse Quaternary fluvio-glacial sediments locally overlay the rock sequence and constitute an interface aquifer unit. Fine marine sediments confine most of the regional aquifers. Collected GIS based information was synthesized in a finite element numerical model. The regional saturated steady-state flow was calibrated under current stress conditions assuming an equivalent porous medium approach. Water budget calculations show that the total groundwater flow in regional aquifers amounts to 97.7 Mm3/y. Infiltration from precipitation provides 86.6% of the groundwater supply, while 9.6% comes from subsurface inflow and the remaining 3.8% is induced recharge from surface waters. Discharge from regional aquifers occurs through flow to streams (76.9%), groundwater withdrawal (18.4%), and underground outflow (4.7%). La plateforme Lowllands du Saint-Laurent, Québec, Canada, est une aire densément peuplée, dépendant grandement des ressources en eau souterraine. En 1999, le Service Géologique du Canada a initié une étude hydrogéologique à grande-échelle sur 1500 km2 au Nord-Ouest de Montréal. Le sobjectifs ont été de définir la dynamique de l’écoulement régional, et de donner des estimations quantitatives des paramètres dynamiques des ressources disponibles en eau souterraine. L’approche utilisée consista à définir le cadre hydrogéologique de travail, les propriétés hydrauliques des unités aquifères, et les composantes dynamiques des eaux souterraines. Les roches sédimentaires du Paléozoïque Inférieur représentent les unités aquifères régionales. Les sédiments marins fins confinent la plus grande partie des aquifères régionaux. Les informations de base, collectées dans un SIG, ont été synthétisées dans un modèle numérique aux éléments finis. L’écoulement permanent régional, en zone saturée, a été calibré en conditions de stress en assumant une approche de milieu poreu équivalent. Les calculs du bilan hydrologique montrent que l’écoulement total des eaux souterraines dans les aquifères régionaux atteind 97,7 Mm3/an. L’infiltration à partir des précipitations apporte 86.6% de l’eau souterraine exploitée; sachant que 9,6% proviennent d’écoulement de subsurfaces, et que les 3,8% restants proviennent de la recharge via les eaux de surface. Le débit pompé des aquifères régionaux apparaît à travers l’écoulement des cours d’eau, le rabattement des eaux souterraines (18.4%), et l’écoulement ascendant (4.7%). La plataforma de Tierras Bajas San Lorenzo, Quebec, Canadá, es un área densamente poblada que depende fuertemente de recursos de agua subterránea. En 1999 el Servicio Geológico de Canadá inició un estudio de evaluación hidrogeológica a gran escala sobre un área de 1,500 km2 en la región noroeste de Montreal. Los objetivos fueron definir el flujo regional de agua subterránea y aportar estimados cuantitativos de los parámetros dinámicos de agua subterráne y de los recursos disponibles de agua subterránea. El enfoque aplicado consistió en definir el marco hidrogeológico, propiedades hidráulicas de las unidades acuíferas, y los componentes dinámicos de agua subterránea. Rocas sedimentarias del Paleozoico Inferior representan unidades regionales de acuíferos. Sedimentos fluvio-glaciares Cuaternarios gruesos sobreyacen localmente la secuencia rocosa y constituyen una unidad acuífera interfacial. Sedimentos marinos finos confinan la mayoría de acuíferos regionales. Información colectada basada en SIG se sintetizó en un modelo numérico de elemento finito. El flujo regional saturado en régimen permanente se calibró bajo condiciones de stress asumiendo un enfoque de medio poroso equivalente. Los cálculos de balance hídrico muestran que el flujo total de agua subterránea en acuíferos regional alcanza 97.7 Mm3/año. Infiltración a partir de lluvia aporta el 86.6% del abastecimiento al agua subterránea, mientras que el 9.6% proviene de entradas subsuperficiales y el restante 3.8% consiste de recarga inducida a partir de aguas superficiales. La descarga proveniente de acuíferos regionales ocurre a través de flujo a ríos (76.9%), utilización de agua subterránea (18.4%), y salida subterránea (4.7%).

- by Ana Rivera
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- Engineering, Earth Sciences, Hydrogeology, Finite Element

To predict the performance of an aquifer thermal energy storage system, an understanding of the system's hydrothermal behavior is needed. One possibility is to run a detailed numerical simulation of the system. However, for a single-well system in which fluid flow is limited to steady radial flow, a characterization scheme based on a set of four dimensionless parameter groups allows production temperatures and energy recovery factors to be read from graphs. The assumption of radial fluid flow is valid when buoyancy flow can be neglected and a well is fully screened in a horizontal aquifer which is confined above and below by impermeable layers. Criteria for little buoyancy flow include a low permeability or vertically stratified aquifer, a small temperature difference between injected and ambient water. and short cycle leneth The ha.•ie enerov tranannrt ., ,.., ........ •,.• ....... r layer system with steady radial fluid flow in the aquifer are nondimensionalized to derive the key parameter groups. Next a numerical model which calculates the heat transfer in the aquifer and confining layers for an injection-storage-production cycle is run for a range of values of these groups. The calculated production temperatures and energy recovery factors are then presented graphically as a function of the parameter groups. Comparisons between results of field experiments and recovery factors read from the graphs show good agreement. ATES cycl• [Tsang eta!., 1977; Fabris et al., 1977]. Recently, Sauty et al. [1980a] have studied the thermal behavior of a simplified single-well ATES system in terms of , a set of dimensionless groups. A few heat storage field experiments in either confined

- by Johan Claesson
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- Environmental Engineering, Civil Engineering, Water resources, Heat Transfer

An analytical model for gas-solid suspension flow through an inclined section of pipe was developed. This model predicts the ratio of the total pressure drop in an inclined pipe to that of a horizontal pipe. The model has been used to predict the critical pipe angle, which is defined as the angle at which the maximum pressure drop for a given solids flow rate is achieved. This angle differs from 90 ° (found in a single-phase flow) and is directly proportional to the ratio between the gas superficial velocity and the particle terminal velocity. The three-dimensional conservation equations for steady-state two-phase flow in an inclined pipe were solved numerically for constant solids and gas flow rates at different pipe inclinations. This model was based on the continuum theory for describing the mass and momentum balance equations for the fluid and solid phases. A packing model, describing the shear stress of the solid phase as a function of its volume fraction, is suggested in order to limit the maximum value of the solid volume fraction. A new model for particle-wall interaction was developed taking into account the angle of inclination of the pipe. The prediction of the numerical model was compared with experimental data obtained in a specially designed test rig. In general, the agreement between the experimental data and the models was satisfactory. The results of the numerical simulation also confirmed that the critical pipe angle for gas-solid flow is lower than 90 ° . The assumptions made during the development of the models were assessed in order to explain the differences between the predicted and measured values of the flow parameters for different flow regimes. © 1997 Elsevier Science S.A.

- by David Mason
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- Mechanical Engineering, Chemical Engineering, Two Phase Flow, Powder technology
- by Brian Sanderson
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- Oceanography, Atmospheric sciences, Standard Deviation, Data Collection

An operational framework is presented for assimilating surface soil moisture remote sensing measurements into a soil-vegetation-atmosphere-transfer (SVAT) model for the robust prediction of root zone moisture time series. The proposed approach is based on analytical treatment of the dynamical equations coupling surface and deeper soil reservoirs. The resulting framework uses biases between observed and modeled time rates of change of surface soil moisture to quantify biases between modeled and actual root zone average soil moisture contents. The approach is based on the popular interactions between soil-biosphere-atmosphere (ISBA) force-restore SVAT model. An experimental data set, collected near Cork, Ireland, is analyzed both for a long data series of 183 days and four short periods that were selected to focus on different hydrometeorological conditions. The results demonstrated that the proposed framework performs uniformly robust over 3 orders of magnitude of misspecification of saturated hydraulic conductivity. In the presence of uncertain initial conditions, the results demonstrated a marked increase in model skill (over the original ISBA model) for periods when average precipitation was less than average potential evaporation.

- by Marco Mancini
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- Environmental Engineering, Civil Engineering, Environmental Science, Remote Sensing

Application of Finite Element techniques of RC structures has been well established. However, this area still needs more research, because of the difficulty of modeling concrete in finite element analysis. Aim of this work is to develop a numerical approach based on the finite element formulation of three dimensional reinforced concrete beams. Concrete is modeled using twenty seven node brick lagrangian element. Bars and bond slip of the bar and concrete were modeled together by introducing the three dimensional truss-linkage elements. The validity of the model is established using comparison of the results with several wellknown tests from the literature.

- by Aeid Abdulrazeg
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- Materials Science, Finite Element, Multidisciplinary, Finite Element Analysis

We present the development and use of a novel distributed geohazard modeling environment for the analysis and interpretation of large scale earthquake data sets. Our work demonstrates, for the first time, how earthquake-related surface deformation measured from satellite images using imageodesy algorithms is coupled with analysis and simulation using finite-element numerical models.

- by Guo Liu
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- Distributed Computing, Grid Computing, Remote Sensing, Finite Element

Finite element models of current structures often behave differently than the structure itself. Model updating techniques are used to enhance the capabilities of the numerical model such that it behaves like the real structure. Experimental data is used in model updating techniques to identify the parameters of the numerical model. In civil infrastructure these model updating techniques use either static or dynamic measurements, separately. This paper studies how a Bayesian updating framework behaves when both static and dynamic data are used to updated the model. Displacements at specific structure locations are obtained for static tests using a computer vision method. High density mode shapes and natural frequencies are obtained using a moving accelerometer structure. The static data and the modal characteristics are combined in a Bayesian modal updating technique that accounts for the incompleteness and uncertainty of the data as well as the possible nonuniqueness of the solution. Results show how the posterior probability density function changes when different type of information is included for updating.

- by Boris Zárate and +1
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- Computer Vision, Model Updating, Natural Frequency, Dynamic Panel Data

Predictions of dense non-aqueous phase liquid (DNAPL) releases are sensitive to the nonwetting phase relative permeability-saturation (k r,N -S) constitutive relationships employed in numerical models. In this study, hysteretic k r,N -S curves were measured for a variety of sands, revealing trends in k r,N -S function shapes that were correlated to sand type. To explore the significance of this conclusion, numerical simulations of a fixed volume DNAPL release were conducted using 10 realisations of a spatially correlated, random permeability field. Simulations assuming homogeneity of relative permeability were compared to those employing the determined functional dependence of relative permeability on porous media properties. The simulations demonstrate both temporal and spatial sensitivity. The time for DNAPL migration to cease is shorter, and the ultimate extent of DNAPL invasion is greater, in those simulations using the traditional assumption that k r,N -S is uniform and not correlated to porous media type.

- by Jason Gerhard
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- Numerical Simulation, Porous Media, Numerical Model, Spatial Correlation

In this paper, lab tests coupled to a semi-pilot test section are used to derive data for the calibration of a numerical model. The paper is aimed at proposing a set of experiments, which can be used to calibrate a numerical model before using it on defined soils. The complexity of the phenomenon of transport of reactive pollutants in soil has to be faced in the most complete way. The different behaviour of soil after wet/dry cycles with respect to the fluidodynamic characteristics and the importance to consider the local biomass behaviour in case of organic contaminant has been underlined. An optimal approach has to take into account all the different components and here a simple series of experimental procedure is presented. The sensitivity analysis of the numerical model has shown that its results are not so much dependent on the classical numerical aspects (time or space increments) but mainly on a set of parameters related to soil structure which must then be derived through a good calibration. (P. Viotti). produced contamination of several aquifers all over the world. Contaminants dispersed at the land surface migrate through the vadose zone before being advected and dispersed by flowing groundwater. Solute transport in unsaturated soils has been the topic of experimental, theoretical research and studies above numerical simulation aspects . The behaviour and fate of chemicals in the vadose zone is complex , being a process occurring in conditions strongly influenced 0304-3800/$ -see front matter

- by Paolo Viotti
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- Unsaturated soil, Sensitivity Analysis, Multidisciplinary, Ecological Modelling

Selective laser melting (SLM) is an additive technology that allows for the production of precisely designed complex structures for energy absorbing applications from a wide range of metallic materials. Geometrical imperfections of the SLM fabricated lattice structures, which form one of the many thin struts, can lead to a great difference in prediction of their behavior. This article deals with the prediction of lattice structure mechanical properties under dynamic loading using finite element method (FEA) with inclusion of geometrical imperfections of the SLM process. Such properties are necessary to know especially for the application of SLM fabricated lattice structures in automotive or aerospace industries. Four types of specimens from AlSi10Mg alloy powder material were manufactured using SLM for quasi-static mechanical testing and determination of lattice structure mechanical properties for the FEA material model, for optical measurement of geometrical accuracy, and for low-v...

- by Pavel Maňas
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- Engineering, Materials Science, Materials, Medicine
- by praveen pinnoji
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- Materials Science, Fracture and cohesive zone model, Numerical Simulation, Impact

From the thermal point of view, windows represent the weak link between the internal and external ambients of a room. In cold climates, they are responsible for 10-25% of the heat lost from the heated ambient to the external atmosphere. In hot climates, the excessive solar radiation entering the internal ambient through the windows leads to increasing the cooling load of the refrigeration system. The use of absorbing gases filling the gap between glass sheets appears to be an alternative solution for thermally insulated glass windows. The other options one may incorporate filling materials such as silica aerogel or a PCM. In this work, a comparison between the thermal efficiency of two glass windows one filled with an absorbing gas and the other with a PCM and exposed to solar radiation in a hot climate is done. To model double glass window filled with infrared absorbing gases, a CW real gas model is used. A radiative convective conductive model and a radiative conductive model were investigated. Three mixtures of gases were used; a strongly absorbing gas mixture, an intermediate absorbing gas mixture and a transparent to infrared radiation mixture. To model the double glass window filled with a PCM, a relatively simple and effective radiation conduction one dimensional formulation is used. Heat transfer through the window is calculated and the total heat gain coefficients are compared and discussed.

A numerical methodology is presented for the modeling of convection-diffusion controlled mushy region change problems. An ef®cient and accurate non-staggered control volume method, based on the momentum interpolation practice and on a high-order convection differencing scheme, is proposed for the solution of the continuum model equation. Suitable numerical techniques are implemented to overcome the numerical instability problems resulting from the strong coupling between the equations of the model. Special attention is given on the ef®cient treatment of the latent head evolution in the energy equation. A new numerical technique is developed which accounts for the dependence of the latent heat on the variation of temperature and concentration ®elds. The proposed method is applied on two phase change problems. Satisfactory agreement with previously published results is observed.

The Vema Transverse Ridge (VTR) is a prominent, long and narrow topographic anomaly that runs for over 300 km along a sea floor spreading flow line south of the Vema transform at 118 N in the Atlantic. It rises abruptly about 140 km from the axis of the Mid-Atlantic Ridge (MAR) in~10 Myr old crust and runs continuously up to~25 Myr old crust. It reaches over 3 km above the predicted lithospheric thermal contraction level. It is absent in crust younger than 10 Myr; thus, the uplift of the VTR must have ended roughly 10 Ma. The VTR is interpreted as the exposed edge of a flexured and uplifted slab of oceanic lithosphere that was generated at an 80 km long MAR segment. Based on satellite gravimetry imagery this MAR segment was born roughly 50 Ma and increased its length at an average rate of 1.6 mm/yr. Multibeam data show that the MAR-parallel sea floor fabric south of the VTR shifts its orientation by 58 to 108 clockwise in~11-12 Myr old crust, indicating a change at that time of the orientation of the MAR axis and of the position of the Euler rotation pole. This change caused extension normal to the transform, followed between 12 and 10 Ma by flexure of the edge of the lithospheric slab, uplift of the VTR at a rate of 2 to 4 mm/yr, and exposure of a lithospheric section (Vema Lithospheric Section or VLS) at the northern edge of the slab, parallel to the Vema transform. Ages of pelagic carbonates encrusting ultramafic rocks sampled at the base of the VLS at different distances from the MAR axis suggest that the entire VTR rose vertically as a single block within the active transform offset. A 50 km long portion of the crest of the VTR rose above sea level, subsided, was truncated at sea level and covered by a carbonate platform. Subaerial and submarine erosion has gradually removed material from the top of the VTR and has modified its slopes. Spreading half rate of the crust south of the transform decreased from 17.2 mm/yr between 26 and 19 Ma to~16.9 mm/yr between 19 and~10 Ma, to~13.6 mm/yr from 10 Ma to present. The slowing down of spreading occurred close in time to the change in ridge/transform geometry, suggesting that the two events are related. A numerical model relates lithospheric flexure to extension normal to the transform, suggesting that the extent of the uplift depends on the thickness of the brittle layer, consistent with the observed greater uplift of the older lithosphere along the VTR.

- by W. Buck
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- Earth Sciences, Sea Level, Mid Ocean Ridge, Physical sciences
- by M. Bristeau
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- Granular Flow, Multidisciplinary, Numerical Simulation, Reference Frame

Application of slump failure mechanism in the numerical modeling of the free meandering is the recent advancement towards dealing the real phenomena on the outer bends of meandering rivers with the numerical models. Recently numerous numerical simulations are performed using two-dimensional morphodynamic model for bed and bank with consideration of effects of slump blocks. Four different cases are simulated separately for steady and unsteady flow condition for about 6 h with and without slump block consideration. The measured bank erosion, channel migration and the channel width evolution show significant difference in the results due to inclusion of slump block effects. Long term simulation has been performed for 24 h to predict the free meandering behavior with variation of different slump block parameters. The result shows clear bar formation and projection, channel formation and migration towards the outer bends, making longer length of the flow path and increasing the sinuosity with the time which is very similar with the natural rivers.

- by gary parker
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- Engineering, Earth Sciences, Numerical Simulation, Unsteady flow

Properties of concentration waves of solutes affected by nonlinear sorption, precipitation/ dissolution and homogeneous reactions in the mobile and stationary phases are established when the number of phases is constant. These properties essentially depend on the structure of a stoichiometric matrix which describes the chemical interactions. A reduction procedure of the stoichiometric matrix gives the number of waves or peaks together with their propagation velocities, and the retardation factors of species at trace levels. The location of the peaks and their broadening behavior due to the nonlinear equilibria are estimated. The number of waves and the properties of suitable linear combinations of concentrations provide a method for discriminating among rival interaction mechanisms irrespective of the equilibrium constants. This cannot be done using conventional methods based on the comparison between numerical simulations and experimental curves. Bryant et al., 1986] are devoted to the consequences of the set of elementary interactions (homogeneous reactions, adsorption and/or exchange reactions, precipitation, dissolution, degassing processes, etc.) on the structure and properties of the corresponding breakthrough curves (BTC). Predicting qualitative properties of BTCs or elucidating the main features of an interaction mechanism from experimental BTCs can be performed using numerical computer codes. Unfortunately, these calculations can be time consuming and they require that the interaction parameters (i.e., equilibrium constants, kinetic constants, etc.) be known. There is thus a need for some general properties relating the structure (i.e., shape, number, and existence of waves or peaks) of the BTCs to the structure of the solid-fluid interaction mechanism. These properties should be as independent as possible of the interaction parameters, and they should help one both to discriminate among rival mecHanisms and to estimate the sensitivity of the shape of the BTCs to physicochemical parameters. This first of two papers describes the underlying concepts

- by Michel Sardin
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- Environmental Engineering, Civil Engineering, Water resources, Carbon Dioxide

A new condition for crack penetration into the aggregate phase in concrete materials is developed based on numerical simulations. The numerical simulation utilizes a newly developed micromechanical model which considers the concrete internal structure as a three-phase material, viz. matrix, aggregate and interfaces between them. The micromechanical model is capable of capturing the entire load-deformation response of a concrete specimen under monotonic loading including softening. The new condition for crack penetration is developed based on a simple specimen con®guration where a crack is driven towards an aggregate particle. Results from numerical simulations are implemented to relate the relative properties of both aggregate and matrix phases (represented by the characteristic length ratio) to their tensile strength ratio. It is shown that the tensile strength ratio between the aggregate and the matrix plays the dominant role in determining the penetration condition. Predictions based on this condition agree with direct tensile simulations using dierent specimen con®guration. Ó

- by Ashraf Mohamed
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- Civil Engineering, Fracture Mechanics, Crack propagation, Numerical Simulation

Tsunami generation by submarine slides have been a major concern in the risk assessment for the Ormen Lange gas field off Western Norway. Tsunamis are analysed with a numerical model supplemented by an analytical one. Both models show how slide extensions and slide dynamics influence the tsunamigenic potential for a large region. Several combinations of slide parameters were tested, and the product of initial acceleration and the volume of the slide gave the best correlation with the maximum surface elevation for the near coastal domain. q

- by Carl Harbitz
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- Geology, Geophysics, Risk assessment, Numerical Model

We calculate the d.c.-current of a semiconductor superlattice in the hopping conduction picture. Electronic transport in this regime is described by hopping transitions between the partially localized Wannier–Stark states. In our numerical model we start from the exact wavefunctions of the superlattice and include both impurity and acoustic phonon scattering. We then obtain the electron drift velocity by considering the

- by Norbert Linder
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- Condensed Matter Physics, Electron Transport, Numerical Model, Boltzmann equation

Bone mass distribution and structure are dependent on mechanical stress and adaptive response at cellular and tissue levels. Mechanical stimulation of bone induces new bone formation in vivo and increases the metabolic activity and gene expression of osteoblasts in culture. A wide variety of devices have been tested for mechanical stimulation of cells and tissues in vitro. The aim of this work was to experimentally validate the possibility to use piezoelectric materials as a mean of mechanical stimulation of bone cells, by converse piezoelectric effect. To estimate the magnitude and the distribution of strain, finite numerical models were applied and the results were complemented with the optical tests (Electronic Speckle Pattern Interferometric Process). In this work, osteoblasts were grown on the surface of a piezoelectric material, both in static and dynamic conditions at low frequencies, and total protein, cell viability and nitric oxide measurement comparisons are presented.

- by J. Reis and +1
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- Mechanical Engineering, Biomedical Engineering, Biomechanics, Gene expression

An analytical method is presented based on the kinematic theorem of limit analysis applied to the stability of reinforced slopes under the seismic loading condition. The rate of external work is due to soil weight and inertia force induced by the earthquake and the only contribution to energy dissipation is that provided by the reinforcement. In the present analysis a rotational failure mechanism is considered. The proposed method considered a log-spiral failure surface. In order to verify the proposed method of analysis; two published case studies Clouterre Test Wall No. 1 and the 4.5 m high wall known as Eparris Wall, built to retain a little cut in plastic clay are utilized. The probable failure surface and the factor of safety obtained by the proposed method are found to be in good agreement with the published test results. Finite element numerical modeling by FLAC is done for these test walls. Numerical analysis is found to be good agreement with the published results and also with field observations.

- by debabrata giri
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- Reinforced soil slope, Numerical Analysis, Finite Element, Earthquake
- by Hans Hanson
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- Civil Engineering, Geology, Coastal Engineering, Prediction

The possibility of quasi-stable trapping of charged particles of hundreds keVMeV energy on the front side Earth magnetosphere is explored in this article by numerical modeling of the single particle orbits in the geomagnetic field... more

Sulfur hexafluoride (SF 6) of >99.9% purity was artificially released to simulate the emission sources in the etching-thin film area of a working cleanroom in a semiconductor fab at the rate of 492 g/h. Three mobile Fourier transform infrared spectrometers (FTIRs, detection limit: 10 ppb) were used simultaneously to measure the real time SF 6 concentrations at different locations of the cleanroom. A three-dimensional numerical model was also used to predict the unsteady gas concentration distribution and the results were compared with the experimental data. Due to high dilution of the pollutant in the cleanroom, it is found that the current gas sensors may not be sensitive enough and a better monitoring system and strategy is needed to protect workers from injury and to ensure good product yield. After comparison with the validated numerical results, the well-mixed model is found to predict the peak pollutant concentrations within a reasonable range which is 0.34-1.33 times the experimental values except when the monitored distance is very close to the release point. The well-mixed model is shown to be capable of predicting a reasonable attainable maximum concentration once a pollutant leaks in the cleanroom.

- by Hui-Ya Shih
- •
- Architecture, Thin Film, Building, Gas Sensor
- by indra jaya
- •
- Geochemistry, Oceanography, Hydrography, Indian Ocean
- by Daniel Delpino
- •
- Geology, Geophysics, Oil and gas, Case Study

An 8-year database of sea surface temperature (SST), 7 years of Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean color images, wind fields, and numerical model results are analyzed to identify regions and periods of coastal upwelling... more

- by Jorge Zavala-hidalgo and +1
- •
- Geology, Oceanography, Sea surface temperature, Seasonality

A numerical model was developed for the computation of the wind field, air temperature and humidity in the urban canopy layer and in the atmospheric boundary layer above urban areas. The model is of k–ε type. The ensemble-spatial averaged three-dimensional Reynolds equations, equation of continuity, turbulent kinetic energy equation (k-equation), and equation for dissipation rate of turbulent energy (ε-equation) are solved together with equations of heat and moisture transfer in the air. Inside the urban canopy layer, volumes of buildings and other urban structures are accounted for by a spatial averaging procedure. With given average building height and building width for each grid mesh, effects of buildings on the momentum transfer are modelled by introducing a form drag force. Temperatures of the ground surface, building walls or roof are computed by the solution of the heat conduction equation in the ground or walls, roof. Evaporation at the ground surface is evaluated using a Bowen ratio. The exhausted heat by building air conditioning is evaluated by employing a building air conditioning model. This heat together with traffic-induced artificial heat are accounted for in the model as heat sources. A numerical model for the momentum, heat and moisture transfer in the plant canopy is also coupled to the model to investigate the effects of vegetation on the urban climate. Verification of the model against observational data in the Tokyo Metropolitan area, Japan, reveals that the model is capable of simulating the momentum, heat and mass transfer in the urban boundary layer. Especially, the model can compute air temperature, humidity and wind velocity at the street level, which cannot be computed by a general above city atmospheric circulation model.

- by Ca Vu Thanh
- •
- Mechanical Engineering, Civil Engineering, Heat and Mass Transfer, Urban Climate

This report summarizes research advances pursued with award funding issued by the DOE to Drexel University through the Presidential Early Career Award (PECASE) program. Professor Rich Cairncross was the recipient of this award in 1997. With it he pursued two related research topics under Sandia's guidance that address the outstanding issue of fluid-structural interactions of liquids with deformable solid materials, focusing mainly on the ubiquitous dynamic wetting problem.

While tomographic inversion has been successfully applied to laboratory-and field-scale tests, here we address the new issue of scale that arises when extending the method to a basin. Specifically, we apply the hydraulic tomography concept to jointly interpret four multi-well aquifer tests in a synthetic basin to illustrate the superiority of this approach to a more traditional Theis analysis of the same tests. Transmissivity and storativity are estimated for each element of a regional numerical model using the geostatistically-based SSLE inverse solution method. We find that hydraulic tomography inversion is an effective strategy for incorporating data from potentially disparate aquifer tests into a basin-wide aquifer property estimate. The robustness of the SSLE algorithm is investigated by considering the effects of noisy observations, changing the variance of the true aquifer parameters, and supplying incorrect initial and boundary conditions to the inverse model.

- by A. Hinnell
- •
- Tomography, Software, Ground Water, Inverse Modeling

Five mercury (Hg) chemistry models are compared using the same data set for model initialisation. All five models include gas-phase oxidation of Hg(0) to Hg(II) (except for one model), fast reduction-oxidation aqueous reactions between Hg(0) and Hg(II), and adsorption of Hg(II) species to soot particles within droplets. However, the models differ in their detailed treatments of these processes. Consequently, the 48-h simulations reveal similarities but also significant discrepancies among the models. For the simulation that included all Hg species (i.e., Hg(0), Hg(II) and Hg(p)) as well as soot in the initial conditions, the maximum simulated Hg(II) aqueous concentrations ranged from 55 to 148 ng l À1 whereas the minimum concentrations ranged from 20 to 110 ng l À1 . These results suggest that further experimental work is critically needed to reduce the current uncertainties in the formulation of Hg chemistry models. r

- by Ilia Ilyin
- •
- Environmental Engineering, Atmospheric Science, Atmospheric sciences, Numerical Model

In this study, the hydrological characteristics of water in the Japan Sea are considered on the basis of the GDEM data of climatic distribution of temperature and salinity . Using a regional-scale numerical model, we investigate the dynamics of these waters and perform a detailed analysis of the formation and propagation of intermediate waters in the Japan Sea. On the basis of numerical modeling, we reveal that the process of the formation and propagation of intermediate waters can be separated into three stages. The first stage is related to the accumulation of a significant water reserve with properties close to the type of intermediate waters in the vicinity of the Peter the Great Bay. The second stage involves the penetration of these waters into intermediate layers as a result of deep convection in the presence of a winter monsoon. The third stage occurs for a reduced subpolar front and leads to the propagation of intermediate waters southward to the Ulung and Yamato basins as well as to their partial recirculation within the northern gyre.

- by Elena Golubeva
- •
- Oceanography, Atmospheric sciences, Regional scale, Numerical Model

In this work, an approach for numerical modeling of the fracture process of complex materials microstructures is presented. It is well known that the relation between a material microstructure and the resulting macroscopic properties is a problem of great practical interest. Thus, we study the effect of the particular microstructure on the fracture mechanism and damage accumulation. To this aim,

- by Marcello Romagnoli
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- Finite element method, Finite Element, Crack Initiation, Fracture Mechanic

In this paper we continue the development of our Python-based package for the solution of partial differential equations using spatial discretization techniques such as the finite element method (FEM), but we take it to a higher level using two approaches: First we define a" Model" class object which makes it easy to break down a complex simulation into simpler sub-models, which then can be linked together into a highly efficient whole. Second, we implement an XML schema in which we can save an entire simulation. Thisn allows ...

Several electrostatic technologies, such as separation of granular mixtures, flocking, printing, or biological cell manipulation, are based on the accurate control of conductive particle motion in insulating gases or liquids by means of relatively high dc electric fields. This paper aimed at characterizing the behavior of such particles by numerical modeling of two aspects: 1) particle motion under the action of electric field forces and 2) insulation breakdown triggered by mobile particles. The equations of particle motion were written by taking into account both gravitational and drag forces, as well as the rebound at particle impact with the electrodes. If the particles move in ionized air, their charge varies in time. In that case, the equation of particle charge should be added to the mathematical model. The output data of the programs for numerical simulation of particle behavior are in good agreement with the available experimental results. Particle movements were shown to be influenced by the intensity of the electric field, by the density of the space charge, by size and mass density of the particles, as well as by their coefficient of restitution at impact with the electrodes. The conclusions regarding the behavior of conductive particles in insulating fluids are useful for the development of improved electrostatic separation technologies; they are of particular interest to all manufacturers of high-voltage equipment.

- by Lucian Dascalescu
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- Engineering, Electrostatics, Numerical Method, High Voltage
- by Harvinder Sidhu
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- Remote Sensing, Satellite remote sensing, Deep water, Depth Estimation

This paper reviews research that has taken place on physical oceanography and sedimentology on New Zealand's estuaries and the inner shelf since c. 1967. It includes estuarine sedimentation, tidal inlets, beach morphodynamics, nearshore and inner shelf sedimentation, tides and coastal currents, numerical modelling, short-period waves, tsunamis, and storm surges. An extensive reference list covering both published and unpublished material is included. Formal teaching and research programmes dealing with coastal landforms and the processes that shape them were only introduced to New Zealand M91078

- by Willem De Lange
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- Earth Sciences, Oceanography, Sedimentology, Mass Transfer

The Ría de Muros is a large coastal embayment on the north-western coast of Spain in which the peak tidal currents exceed 2 m/s. It is therefore a promising site for tidal stream power. The key point when assessing this resource is the accurate estimation of the tidal currents. In this work a finite difference numerical model is used for this purpose. The model solves the vertically integrated Navier-Stokes hydrodynamics and transport equations. It is validated with in situ velocity measurements performed by means of an acoustic Doppler current profiler (ADCP). Thereafter the tidal flow velocities and the corresponding power densities are computed. The largest values are found in a section of the inner ria, in which two points are selected for a detailed assessment of the resource. The model is then run to compute the tidal stream and the corresponding power density at these points during a 14-day period, so as to cover the spring-neap cycle. The power density curve thus obtained is numerically integrated to compute the annual energy output that can be obtained by a tidal stream power plant at each location.

- by Gregorio Iglesias
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- Mechanical Engineering, Renewable Energy, Power Plant, Navier Stokes

The heat and species transport processes in a tubular type solid oxide fuel cell (SOFC) that works in a cell stack were analyzed and modeled. Since most of the single tubular SOFCs working in a cell stack share the same/similar chemical/electrochemical and heat/mass transfer conditions, it is plausible to assume that heat and species are not exchanged between one cell and its neighboring cells. Therefore, a surrounding fuel flow space was outlined controllable by a specific single cell, for which zero flux was assumed at its boundary in neighborhood with other cells. The numerical model subjects such a cell and its controllable fuel flow space to a two-dimensional analysis for the flow, heat/mass transfer and chemical/electrochemical performance. Computations were performed for three different tubular SOFCs having practical operating results available from publications by different researchers. The numerical results of the terminal voltages for those different SOFCs showed very good agreement with the published experimental data. It is expectable that the proposed numerical model be used to significantly help the design and operation of a SOFC stack in practical applications.

- by Peiwen Li and +1
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- Engineering, Mass Transfer, Simulation, Dimensional Analysis

Dense layers of suspended fine sediments (concentrations of the order of 10 1 -10 2 g l À1 ) have been observed within the lower $2-4 m of the water column on the Amazon continental shelf. The presence of these fluid mud layers leads to an increase in the fluid viscosity and density, and has been suggested to reduce the bottom shear stress, thus affecting the tidal wave propagation. This work presents a numerical study of the effects of fluid mud upon the tidal flow in the Amazon shelf. A two dimensional, vertically integrated, finite element numerical model has been configured to the region, for simulating the propagation of the M 2 tidal component. Bottom shear stress over fluid mud layers is parameterized based on a viscous oscillatory boundary layer model, while over sand and consolidated mud beds is computed with a classical turbulent parameterization. Simulations in which the shelf is considered to consist only of sand, or of sand and consolidated muds, significantly underestimate the tidal amplitudes along the coast. Otherwise, if the presence of the fluid mud layers is taken into account, the distribution of which is derived from previous observations, the tidal amplitudes are well represented by the model. The results demonstrate that the presence of nearbottom fluid mud layers represent an important factor in the dynamics of the Amazon continental shelf, since reducing the bottom stress and, therefore, lowering the energy dissipation, larger tidal amplitudes are allowed to occur. r

- by Susana Vinzon and +1
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- Earth Sciences, Finite Element, Biological Sciences, Shear Stress

Global sensitivity analysis is often impracticable for complex and time demanding numerical models, as it requires a large number of runs. The reduced-basis approach provides a way to replace the original model by a much faster to run code. In this paper, we are interested in the information loss induced by the approximation on the estimation of sensitivity indices. We present a method to provide a robust error assessment, hence enabling significant time savings without sacrifice on precision and rigourousness. We illustrate our method with an experiment where computation time is divided by a factor of nearly 6. We also give directions on tuning some of the parameters used in our estimation algorithms.

1] The preservation of high-pressure, low-temperature (HP-LT) mineral assemblages adjacent to marble unit contacts on the Cycladic island of Tinos in Greece was investigated using a new type of digital outcrop mapping and numerical modeling of metamorphic fluid infiltration. Mineral assemblage distributions in a large blueschist outcrop, adjacent to the basal contact of a 150-meter thick marble horizon, were mapped at centimeter-scale resolution onto digital photographs using a belt-worn computer and graphics editing software. Digital mapping reveals that while most HP-LT rocks in the outcrop were pervasively retrograded to greenschist facies, the marble-blueschist contact zone underwent an even more intense retrogression. Preservation of HP-LT mineral assemblages was mainly restricted to a 10-15 meter zone (or enclave) adjacent to the intensely retrograded lithologic contact. The degree and distribution of the retrograde overprint suggests that pervasively infiltrating fluids were channelized into the marbleblueschist contact and associated veins and flowed around the preserved HP-LT enclave. Numerical modeling of Darcian flow, based on the field observations, suggests that near the marble horizon, deflections in fluid flow paths caused by flow channelization along the high-permeability marbleblueschist contact zone likely resulted in very large fluid fluxes along the lithologic contact and significantly smaller fluxes (as much as 8 times smaller than the input flux) within the narrow, low-flux regions where HP-LT minerals were preserved adjacent to the contact. Our results indicate that lithologic contacts are important conduits for metamorphic fluid flow in subduction zones. Channelization of retrograde fluids into these discrete flow conduits played a critical role in the preservation of HP-LT assemblages.

- by Edward Bolton and +1
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- Earth Sciences, Geochemistry, High Pressure, Digital mapping

Submitted for the DFD08 Meeting of The American Physical Society Blast-Induced Pressure Fields Beneath a Military Helmet for Non-Lethal Threats DAVID MOTT, DOUGLAS SCHWER, THEODORE YOUNG, Naval Research Laboratory, JEFFREY LEVINE, JEAN-PHILIPPE DIONNE, ARIS MAKRIS, Allen-Vanguard Corp. (Med-Eng Systems), GRAHAM HUBLER, Naval Research Laboratory — Coordinated experiments and numerical simulations investigated the pressure field surrounding a head with a helmet subjected to a blast wave typical of injurious but non-lethal threats. Experiments were conducted with C4 explosive charges ranging from 0.75 kg to 5 kg, and two anthropomorphic test mannequins (Hybrid III) located 3 m from the explosive. Experimental diagnostics included pressure sensors mounted at selected locations around each mannequin’s head and in the free-field. Numerical modeling was done using a two-step approach. First, the blast and ground reflection were computed using a multi-component, reacting flow model. Second,...

- by Jean-Philippe Dionne
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- Numerical Simulation, Numerical Model, Three Dimensional, Pressure Sensor

The main goal of this paper is to present a numerical model describing the major physical phenomena involved in electromagnetic casting industrial processes as precisely as possible. Under suitable physical assumptions, we derive the set of equations in the two-dimensional case; we describe in detail the numerical methods used to solve such equations and derive an iterative algorithm. Numerical results describing the case of an aluminium ingot are presented in order to show the efliciency of the method. lc'

- by Rachid Touzani
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- Engineering, Computational Physics, Numerical Modelling, Numerical Method

From March 1997 to March 1999, sequential rainwater samples were collected during 12 rainfalls at Avignon, Southern France, with the objective of investigating how the formation conditions affect the isotopic composition of the most frequent rain types occurring in the western Mediterranean region. Three major isotopic trends were identified: (i) a descending d 18 O trend, produced when a cold front penetration causes the rise of warm and humid air masses, accompanied by adiabatic cooling and precipitation. The temperature variation is the predominant feature of frontal rainfalls; (ii) an L-shaped d 18 O trend, which can be produced by convective rains, with an initial rapid decrease followed by a stationary value; (iii) a V-shaped trend, in which the final phase of precipitation obeys a different mechanism from the first phase. Frontal and convective rainfalls may produce this trend.

- by Hélène Celle-Jeanton and +1
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- Hydrology, Multidisciplinary, Numerical Model, Mediterranean region

We describe a method for the visual interactive simulation of wires contacting with rigid multibodies. The physical model used is a hybrid combining lumped elements and massless quasistatic representations. The latter is based on a kinematic constraint preserving the total length of the wire along a segmented path which can involve multiple bodies simultaneously and dry frictional contact nodes used for roping, lassoing and fastening. These nodes provide stick and slide friction along edges of the contacting geometries. The lumped element resolution is adapted dynamically based on local stability criteria, becoming coarser as the tension increases, and up to the purely kinematic representation. Kinematic segments and contact nodes are added and deleted and propagated based on contact geometries and dry friction configurations. The method gives dramatic increase on both performance and robustness because it quickly decimates superfluous nodes without loosing stability, yet adapts to complex configurations with many contacts and high curvature, keeping a fixed, large integration time step. Numerical results demonstrating the performance and stability of the adaptive multiresolution scheme are presented along with an array of representative simulation examples illustrating the versatility of the frictional contact model.

- by Kenneth Bodin
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- Computer Graphics, Animation, Virtual Reality, Adaptive Dynamics