Chen, Xinzhong; Lo, Chiu Fan Bowen; Zheng, William; Hu, Hai; Dai, Qing; Liu, Mengkun
2017-11-01
Over the last decade, scattering-type scanning near-field optical microscopy and spectroscopy have been widely used in nano-photonics and material research due to their fine spatial resolution and broad spectral range. A number of simplified analytical models have been proposed to quantitatively understand the tip-scattered near-field signal. However, a rigorous interpretation of the experimental results is still lacking at this stage. Numerical modelings, on the other hand, are mostly done by simulating the local electric field slightly above the sample surface, which only qualitatively represents the near-field signal rendered by the tip-sample interaction. In this work, we performed a more comprehensive numerical simulation which is based on realistic experimental parameters and signal extraction procedures. By directly comparing to the experiments as well as other simulation efforts, our methods offer a more accurate quantitative description of the near-field signal, paving the way for future studies of complex systems at the nanoscale.
Photoconductivity of amorphous silicon-rigorous modelling
International Nuclear Information System (INIS)
Brada, P.; Schauer, F.
1991-01-01
It is our great pleasure to express our gratitude to Prof. Grigorovici, the pioneer of the exciting field of amorphous state by our modest contribution to this area. In this paper are presented the outline of the rigorous modelling program of the steady-state photoconductivity in amorphous silicon and related materials. (Author)
A rigorous test for a new conceptual model for collisions
International Nuclear Information System (INIS)
Peixoto, E.M.A.; Mu-Tao, L.
1979-01-01
A rigorous theoretical foundation for the previously proposed model is formulated and applied to electron scattering by H 2 in the gas phase. An rigorous treatment of the interaction potential between the incident electron and the Hydrogen molecule is carried out to calculate Differential Cross Sections for 1 KeV electrons, using Glauber's approximation Wang's molecular wave function for the ground electronic state of H 2 . Moreover, it is shown for the first time that, when adequately done, the omission of two center terms does not adversely influence the results of molecular calculations. It is shown that the new model is far superior to the Independent Atom Model (or Independent Particle Model). The accuracy and simplicity of the new model suggest that it may be fruitfully applied to the description of other collision phenomena (e.g., in molecular beam experiments and nuclear physics). A new techniques is presented for calculations involving two center integrals within the frame work of the Glauber's approximation for scattering. (Author) [pt
Energy Technology Data Exchange (ETDEWEB)
Maksymov, Ivan S., E-mail: ivan.maksymov@uwa.edu.au [School of Physics M013, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia); ARC Centre of Excellence for Nanoscale BioPhotonics, School of Applied Sciences, RMIT University, Melbourne, VIC 3001 (Australia); Hutomo, Jessica; Nam, Donghee; Kostylev, Mikhail [School of Physics M013, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)
2015-05-21
We demonstrate theoretically a ∼350-fold local enhancement of the intensity of the in-plane microwave magnetic field in multilayered structures made from a magneto-insulating yttrium iron garnet (YIG) layer sandwiched between two non-magnetic layers with a high dielectric constant matching that of YIG. The enhancement is predicted for the excitation regime when the microwave magnetic field is induced inside the multilayer by the transducer of a stripline Broadband Ferromagnetic Resonance (BFMR) setup. By means of a rigorous numerical solution of the Landau-Lifshitz-Gilbert equation consistently with the Maxwell's equations, we investigate the magnetisation dynamics in the multilayer. We reveal a strong photon-magnon coupling, which manifests itself as anti-crossing of the ferromagnetic resonance magnon mode supported by the YIG layer and the electromagnetic resonance mode supported by the whole multilayered structure. The frequency of the magnon mode depends on the external static magnetic field, which in our case is applied tangentially to the multilayer in the direction perpendicular to the microwave magnetic field induced by the stripline of the BFMR setup. The frequency of the electromagnetic mode is independent of the static magnetic field. Consequently, the predicted photon-magnon coupling is sensitive to the applied magnetic field and thus can be used in magnetically tuneable metamaterials based on simultaneously negative permittivity and permeability achievable thanks to the YIG layer. We also suggest that the predicted photon-magnon coupling may find applications in microwave quantum information systems.
Memory sparing, fast scattering formalism for rigorous diffraction modeling
Iff, W.; Kämpfe, T.; Jourlin, Y.; Tishchenko, A. V.
2017-07-01
The basics and algorithmic steps of a novel scattering formalism suited for memory sparing and fast electromagnetic calculations are presented. The formalism, called ‘S-vector algorithm’ (by analogy with the known scattering-matrix algorithm), allows the calculation of the collective scattering spectra of individual layered micro-structured scattering objects. A rigorous method of linear complexity is applied to model the scattering at individual layers; here the generalized source method (GSM) resorting to Fourier harmonics as basis functions is used as one possible method of linear complexity. The concatenation of the individual scattering events can be achieved sequentially or in parallel, both having pros and cons. The present development will largely concentrate on a consecutive approach based on the multiple reflection series. The latter will be reformulated into an implicit formalism which will be associated with an iterative solver, resulting in improved convergence. The examples will first refer to 1D grating diffraction for the sake of simplicity and intelligibility, with a final 2D application example.
International Nuclear Information System (INIS)
Ahmadi, A.; Meyer, M.; Rouzineau, D.; Prevost, M.; Alix, P.; Laloue, N.
2010-01-01
This paper gives the first step of the development of a rigorous multicomponent reactive separation model. Such a model is highly essential to further the optimization of acid gases removal plants (CO 2 capture, gas treating, etc.) in terms of size and energy consumption, since chemical solvents are conventionally used. Firstly, two main modelling approaches are presented: the equilibrium-based and the rate-based approaches. Secondly, an extended rate-based model with rigorous modelling methodology for diffusion-reaction phenomena is proposed. The film theory and the generalized Maxwell-Stefan equations are used in order to characterize multicomponent interactions. The complete chain of chemical reactions is taken into account. The reactions can be kinetically controlled or at chemical equilibrium, and they are considered for both liquid film and liquid bulk. Thirdly, the method of numerical resolution is described. Coupling the generalized Maxwell-Stefan equations with chemical equilibrium equations leads to a highly non-linear Differential-Algebraic Equations system known as DAE index 3. The set of equations is discretized with finite-differences as its integration by Gear method is complex. The resulting algebraic system is resolved by the Newton- Raphson method. Finally, the present model and the associated methods of numerical resolution are validated for the example of esterification of methanol. This archetype non-electrolytic system permits an interesting analysis of reaction impact on mass transfer, especially near the phase interface. The numerical resolution of the model by Newton-Raphson method gives good results in terms of calculation time and convergence. The simulations show that the impact of reactions at chemical equilibrium and that of kinetically controlled reactions with high kinetics on mass transfer is relatively similar. Moreover, the Fick's law is less adapted for multicomponent mixtures where some abnormalities such as counter
Rigorous Numerics for ill-posed PDEs: Periodic Orbits in the Boussinesq Equation
Castelli, Roberto; Gameiro, Marcio; Lessard, Jean-Philippe
2018-04-01
In this paper, we develop computer-assisted techniques for the analysis of periodic orbits of ill-posed partial differential equations. As a case study, our proposed method is applied to the Boussinesq equation, which has been investigated extensively because of its role in the theory of shallow water waves. The idea is to use the symmetry of the solutions and a Newton-Kantorovich type argument (the radii polynomial approach) to obtain rigorous proofs of existence of the periodic orbits in a weighted ℓ1 Banach space of space-time Fourier coefficients with exponential decay. We present several computer-assisted proofs of the existence of periodic orbits at different parameter values.
Rigorous bounds on the free energy of electron-phonon models
Raedt, Hans De; Michielsen, Kristel
1997-01-01
We present a collection of rigorous upper and lower bounds to the free energy of electron-phonon models with linear electron-phonon interaction. These bounds are used to compare different variational approaches. It is shown rigorously that the ground states corresponding to the sharpest bounds do
International Nuclear Information System (INIS)
Terhesiu, Dalia; Froyland, Gary
2008-01-01
It is well known that for different classes of transformations, including the class of piecewise C 2 expanding maps T : [0, 1] O, Ulam's method is an efficient way to numerically approximate the absolutely continuous invariant measure of T. We develop a new extension of Ulam's method and prove that this extension can be used for the numerical approximation of the Ruelle–Perron–Frobenius operator associated with T and the potential φ β = −β log |T | |, where β element of R. In particular, we prove that our extended Ulam's method is a powerful tool for computing the topological pressure P(T, φ β ) and the density of the equilibrium state
A Rigorous Investigation on the Ground State of the Penson-Kolb Model
Yang, Kai-Hua; Tian, Guang-Shan; Han, Ru-Qi
2003-05-01
By using either numerical calculations or analytical methods, such as the bosonization technique, the ground state of the Penson-Kolb model has been previously studied by several groups. Some physicists argued that, as far as the existence of superconductivity in this model is concerned, it is canonically equivalent to the negative-U Hubbard model. However, others did not agree. In the present paper, we shall investigate this model by an independent and rigorous approach. We show that the ground state of the Penson-Kolb model is nondegenerate and has a nonvanishing overlap with the ground state of the negative-U Hubbard model. Furthermore, we also show that the ground states of both the models have the same good quantum numbers and may have superconducting long-range order at the same momentum q = 0. Our results support the equivalence between these models. The project partially supported by the Special Funds for Major State Basic Research Projects (G20000365) and National Natural Science Foundation of China under Grant No. 10174002
Rigorous theoretical derivation of lumped models to transmission line systems
International Nuclear Information System (INIS)
Zhao Jixiang
2012-01-01
By virtue of the negative electric parameter concept, i.e. negative lumped resistance, inductance, conductance and capacitance (N-RLGC), the lumped equivalent models of transmission line systems, including the circuit model, two-port π-network and T-network, are given. We start from the N-segment-ladder-like equivalent networks composed distributed parameters, and achieve the input impedance in the form of a continued fraction. Utilizing the continued fraction theory, the expressions of input impedance are obtained under three kinds of extreme cases, i.e. the load impedances are equal to zero, infinity and characteristic impedance, respectively. When the number of segment N is limited to infinity, they are transformed to lumped elements. Comparison between the distributed model and lumped model of transmission lines, the expression of tanh γd, which is the key term in the transmission line equations, are obtained by RLGC, furthermore, according to input admittance, admittance matrix and ABCD matrix of transmission lines, the lumped equivalent circuit models, π-networks and T-networks have been given. The models are verified in the frequency and time domain, respectively, showing that the models are accurate and efficient. (semiconductor integrated circuits)
Rigorously testing multialternative decision field theory against random utility models.
Berkowitsch, Nicolas A J; Scheibehenne, Benjamin; Rieskamp, Jörg
2014-06-01
Cognitive models of decision making aim to explain the process underlying observed choices. Here, we test a sequential sampling model of decision making, multialternative decision field theory (MDFT; Roe, Busemeyer, & Townsend, 2001), on empirical grounds and compare it against 2 established random utility models of choice: the probit and the logit model. Using a within-subject experimental design, participants in 2 studies repeatedly choose among sets of options (consumer products) described on several attributes. The results of Study 1 showed that all models predicted participants' choices equally well. In Study 2, in which the choice sets were explicitly designed to distinguish the models, MDFT had an advantage in predicting the observed choices. Study 2 further revealed the occurrence of multiple context effects within single participants, indicating an interdependent evaluation of choice options and correlations between different context effects. In sum, the results indicate that sequential sampling models can provide relevant insights into the cognitive process underlying preferential choices and thus can lead to better choice predictions. PsycINFO Database Record (c) 2014 APA, all rights reserved.
Some rigorous results on the Hopfield neural network model
International Nuclear Information System (INIS)
Koch, H.; Piasko, J.
1989-01-01
The authors analyze the thermal equilibrium distribution of 2 p mean field variables for the Hopfield model with p stored patterns, in the case where 2 p is small compared to the number of spins. In particular, they give a full description of the free energy density in the thermodynamic limit, and of the so-called symmetric solutions for the mean field equations
Semantically-Rigorous Systems Engineering Modeling Using Sysml and OWL
Jenkins, J. Steven; Rouquette, Nicolas F.
2012-01-01
The Systems Modeling Language (SysML) has found wide acceptance as a standard graphical notation for the domain of systems engineering. SysML subsets and extends the Unified Modeling Language (UML) to define conventions for expressing structural, behavioral, and analytical elements, and relationships among them. SysML-enabled modeling tools are available from multiple providers, and have been used for diverse projects in military aerospace, scientific exploration, and civil engineering. The Web Ontology Language (OWL) has found wide acceptance as a standard notation for knowledge representation. OWL-enabled modeling tools are available from multiple providers, as well as auxiliary assets such as reasoners and application programming interface libraries, etc. OWL has been applied to diverse projects in a wide array of fields. While the emphasis in SysML is on notation, SysML inherits (from UML) a semantic foundation that provides for limited reasoning and analysis. UML's partial formalization (FUML), however, does not cover the full semantics of SysML, which is a substantial impediment to developing high confidence in the soundness of any conclusions drawn therefrom. OWL, by contrast, was developed from the beginning on formal logical principles, and consequently provides strong support for verification of consistency and satisfiability, extraction of entailments, conjunctive query answering, etc. This emphasis on formal logic is counterbalanced by the absence of any graphical notation conventions in the OWL standards. Consequently, OWL has had only limited adoption in systems engineering. The complementary strengths and weaknesses of SysML and OWL motivate an interest in combining them in such a way that we can benefit from the attractive graphical notation of SysML and the formal reasoning of OWL. This paper describes an approach to achieving that combination.
DEFF Research Database (Denmark)
Henriquez, Vicente Cutanda
This thesis describes the development of a numerical model of the propagation of sound waves in fluids with viscous and thermal losses, with application to the simulation of acoustic transducers, in particular condenser microphones for measurement. The theoretical basis is presented, numerical...... manipulations are developed to satisfy the more complicated boundary conditions, and a model of a condenser microphone with a coupled membrane is developed. The model is tested against measurements of ¼ inch condenser microphones and analytical calculations. A detailed discussion of the results is given....
Diffraction-based overlay measurement on dedicated mark using rigorous modeling method
Lu, Hailiang; Wang, Fan; Zhang, Qingyun; Chen, Yonghui; Zhou, Chang
2012-03-01
Diffraction Based Overlay (DBO) is widely evaluated by numerous authors, results show DBO can provide better performance than Imaging Based Overlay (IBO). However, DBO has its own problems. As well known, Modeling based DBO (mDBO) faces challenges of low measurement sensitivity and crosstalk between various structure parameters, which may result in poor accuracy and precision. Meanwhile, main obstacle encountered by empirical DBO (eDBO) is that a few pads must be employed to gain sufficient information on overlay-induced diffraction signature variations, which consumes more wafer space and costs more measuring time. Also, eDBO may suffer from mark profile asymmetry caused by processes. In this paper, we propose an alternative DBO technology that employs a dedicated overlay mark and takes a rigorous modeling approach. This technology needs only two or three pads for each direction, which is economic and time saving. While overlay measurement error induced by mark profile asymmetry being reduced, this technology is expected to be as accurate and precise as scatterometry technologies.
International Nuclear Information System (INIS)
García-Valenzuela, A; Contreras-Tello, H; Márquez-Islas, R; Sánchez-Pérez, C
2013-01-01
We derive an optical model for the light intensity distribution around the critical angle in a standard Abbe refractometer when used on absorbing homogenous fluids. The model is developed using rigorous electromagnetic optics. The obtained formula is very simple and can be used suitably in the analysis and design of optical sensors relying on Abbe type refractometry.
International Nuclear Information System (INIS)
Bodvarsson, G.S.; Lippmann, M.J.
1980-01-01
The computer program CCC (conduction-convection-consolidation), developed at Lawrence Berkeley Laboratory, solves numerically the heat and mass flow equations for a fully saturated medium, and computes one-dimensional consolidation of the simulated systems. The model employs the Integrated Finite Difference Method (IFDM) in discretizing the saturated medium and formulating the governing equations. The sets of equations are solved either by an iterative solution technique (old version) or an efficient sparse solver (new version). The deformation of the medium is calculated using the one-dimensional consolidation theory of Terzaghi. In this paper, the numerical code is described, validation examples given and areas of application discussed. Several example problems involving flow through fractured media are also presented
The effect of temperature on the mechanical aspects of rigor mortis in a liquid paraffin model.
Ozawa, Masayoshi; Iwadate, Kimiharu; Matsumoto, Sari; Asakura, Kumiko; Ochiai, Eriko; Maebashi, Kyoko
2013-11-01
Rigor mortis is an important phenomenon to estimate the postmortem interval in forensic medicine. Rigor mortis is affected by temperature. We measured stiffness of rat muscles using a liquid paraffin model to monitor the mechanical aspects of rigor mortis at five temperatures (37, 25, 10, 5 and 0°C). At 37, 25 and 10°C, the progression of stiffness was slower in cooler conditions. At 5 and 0°C, the muscle stiffness increased immediately after the muscles were soaked in cooled liquid paraffin and then muscles gradually became rigid without going through a relaxed state. This phenomenon suggests that it is important to be careful when estimating the postmortem interval in cold seasons. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
Kavka, P.; Jeřábek, J.; Strouhal, L.
2016-12-01
The contribution presents a numerical model SMODERP that is used for calculation and prediction of surface runoff and soil erosion from agricultural land. The physically based model includes the processes of infiltration (Phillips equation), surface runoff routing (kinematic wave based equation), surface retention, surface roughness and vegetation impact on runoff. The model is being developed at the Department of Irrigation, Drainage and Landscape Engineering, Civil Engineering Faculty, CTU in Prague. 2D version of the model was introduced in last years. The script uses ArcGIS system tools for data preparation. The physical relations are implemented through Python scripts. The main computing part is stand alone in numpy arrays. Flow direction is calculated by Steepest Descent algorithm and in multiple flow algorithm. Sheet flow is described by modified kinematic wave equation. Parameters for five different soil textures were calibrated on the set of hundred measurements performed on the laboratory and filed rainfall simulators. Spatially distributed models enable to estimate not only surface runoff but also flow in the rills. Development of the rills is based on critical shear stress and critical velocity. For modelling of the rills a specific sub model was created. This sub model uses Manning formula for flow estimation. Flow in the ditches and streams are also computed. Numerical stability of the model is controled by Courant criterion. Spatial scale is fixed. Time step is dynamic and depends on the actual discharge. The model is used in the framework of the project "Variability of Short-term Precipitation and Runoff in Small Czech Drainage Basins and its Influence on Water Resources Management". Main goal of the project is to elaborate a methodology and online utility for deriving short-term design precipitation series, which could be utilized by a broad community of scientists, state administration as well as design planners. The methodology will account for
International Nuclear Information System (INIS)
Kim, Chang-Bae; Krommes, J.A.
1988-08-01
The work of Krommes and Smith on rigorous upper bounds for the turbulent transport of a passively advected scalar [/ital Ann. Phys./ 177:246 (1987)] is extended in two directions: (1) For their ''reference model,'' improved upper bounds are obtained by utilizing more sophisticated two-time constraints which include the effects of cross-correlations up to fourth order. Numerical solutions of the model stochastic differential equation are also obtained; they show that the new bounds compare quite favorably with the exact results, even at large Reynolds and Kubo numbers. (2) The theory is extended to take account of a finite spatial autocorrelation length L/sub c/. As a reasonably generic example, the problem of particle transport due to statistically specified stochastic magnetic fields in a collisionless turbulent plasma is revisited. A bound is obtained which reduces for small L/sub c/ to the quasilinear limit and for large L/sub c/ to the strong turbulence limit, and which provides a reasonable and rigorous interpolation for intermediate values of L/sub c/. 18 refs., 6 figs
Rigorous spin-spin correlation function of Ising model on a special kind of Sierpinski Carpets
International Nuclear Information System (INIS)
Yang, Z.R.
1993-10-01
We have exactly calculated the rigorous spin-spin correlation function of Ising model on a special kind of Sierpinski Carpets (SC's) by means of graph expansion and a combinatorial approach and investigated the asymptotic behaviour in the limit of long distance. The result show there is no long range correlation between spins at any finite temperature which indicates no existence of phase transition and thus finally confirms the conclusion produced by the renormalization group method and other physical arguments. (author). 7 refs, 6 figs
Parent Management Training-Oregon Model: Adapting Intervention with Rigorous Research.
Forgatch, Marion S; Kjøbli, John
2016-09-01
Parent Management Training-Oregon Model (PMTO(®) ) is a set of theory-based parenting programs with status as evidence-based treatments. PMTO has been rigorously tested in efficacy and effectiveness trials in different contexts, cultures, and formats. Parents, the presumed agents of change, learn core parenting practices, specifically skill encouragement, limit setting, monitoring/supervision, interpersonal problem solving, and positive involvement. The intervention effectively prevents and ameliorates children's behavior problems by replacing coercive interactions with positive parenting practices. Delivery format includes sessions with individual families in agencies or families' homes, parent groups, and web-based and telehealth communication. Mediational models have tested parenting practices as mechanisms of change for children's behavior and found support for the theory underlying PMTO programs. Moderating effects include children's age, maternal depression, and social disadvantage. The Norwegian PMTO implementation is presented as an example of how PMTO has been tailored to reach diverse populations as delivered by multiple systems of care throughout the nation. An implementation and research center in Oslo provides infrastructure and promotes collaboration between practitioners and researchers to conduct rigorous intervention research. Although evidence-based and tested within a wide array of contexts and populations, PMTO must continue to adapt to an ever-changing world. © 2016 Family Process Institute.
Directory of Open Access Journals (Sweden)
Spiros Pagiatakis
2009-10-01
Full Text Available In this paper, we examine the effect of changing the temperature points on MEMS-based inertial sensor random error. We collect static data under different temperature points using a MEMS-based inertial sensor mounted inside a thermal chamber. Rigorous stochastic models, namely Autoregressive-based Gauss-Markov (AR-based GM models are developed to describe the random error behaviour. The proposed AR-based GM model is initially applied to short stationary inertial data to develop the stochastic model parameters (correlation times. It is shown that the stochastic model parameters of a MEMS-based inertial unit, namely the ADIS16364, are temperature dependent. In addition, field kinematic test data collected at about 17 °C are used to test the performance of the stochastic models at different temperature points in the filtering stage using Unscented Kalman Filter (UKF. It is shown that the stochastic model developed at 20 °C provides a more accurate inertial navigation solution than the ones obtained from the stochastic models developed at −40 °C, −20 °C, 0 °C, +40 °C, and +60 °C. The temperature dependence of the stochastic model is significant and should be considered at all times to obtain optimal navigation solution for MEMS-based INS/GPS integration.
El-Diasty, Mohammed; Pagiatakis, Spiros
2009-01-01
In this paper, we examine the effect of changing the temperature points on MEMS-based inertial sensor random error. We collect static data under different temperature points using a MEMS-based inertial sensor mounted inside a thermal chamber. Rigorous stochastic models, namely Autoregressive-based Gauss-Markov (AR-based GM) models are developed to describe the random error behaviour. The proposed AR-based GM model is initially applied to short stationary inertial data to develop the stochastic model parameters (correlation times). It is shown that the stochastic model parameters of a MEMS-based inertial unit, namely the ADIS16364, are temperature dependent. In addition, field kinematic test data collected at about 17 °C are used to test the performance of the stochastic models at different temperature points in the filtering stage using Unscented Kalman Filter (UKF). It is shown that the stochastic model developed at 20 °C provides a more accurate inertial navigation solution than the ones obtained from the stochastic models developed at -40 °C, -20 °C, 0 °C, +40 °C, and +60 °C. The temperature dependence of the stochastic model is significant and should be considered at all times to obtain optimal navigation solution for MEMS-based INS/GPS integration.
Numerical modelling of mine workings.
CSIR Research Space (South Africa)
Lightfoot, N
1999-03-01
Full Text Available to cover most of what is required for a practising rock mechanics engineer to be able to use any of these five programs to solve practical mining problems. The chapters on specific programs discuss their individual strengths and weaknesses and highlight... and applications of numerical modelling in the context of the South African gold and platinum mining industries. This includes an example that utilises a number of different numerical 3 modelling programs to solve a single problem. This particular example...
Numerical modeling of economic uncertainty
DEFF Research Database (Denmark)
Schjær-Jacobsen, Hans
2007-01-01
Representation and modeling of economic uncertainty is addressed by different modeling methods, namely stochastic variables and probabilities, interval analysis, and fuzzy numbers, in particular triple estimates. Focusing on discounted cash flow analysis numerical results are presented, comparisons...... are made between alternative modeling methods, and characteristics of the methods are discussed....
Hamid, H.
2018-01-01
The purpose of this study is to analyze an improvement of students’ mathematical critical thinking (CT) ability in Real Analysis course by using Rigorous Teaching and Learning (RTL) model with informal argument. In addition, this research also attempted to understand students’ CT on their initial mathematical ability (IMA). This study was conducted at a private university in academic year 2015/2016. The study employed the quasi-experimental method with pretest-posttest control group design. The participants of the study were 83 students in which 43 students were in the experimental group and 40 students were in the control group. The finding of the study showed that students in experimental group outperformed students in control group on mathematical CT ability based on their IMA (high, medium, low) in learning Real Analysis. In addition, based on medium IMA the improvement of mathematical CT ability of students who were exposed to RTL model with informal argument was greater than that of students who were exposed to CI (conventional instruction). There was also no effect of interaction between RTL model and CI model with both (high, medium, and low) IMA increased mathematical CT ability. Finally, based on (high, medium, and low) IMA there was a significant improvement in the achievement of all indicators of mathematical CT ability of students who were exposed to RTL model with informal argument than that of students who were exposed to CI.
Layout optimization of DRAM cells using rigorous simulation model for NTD
Jeon, Jinhyuck; Kim, Shinyoung; Park, Chanha; Yang, Hyunjo; Yim, Donggyu; Kuechler, Bernd; Zimmermann, Rainer; Muelders, Thomas; Klostermann, Ulrich; Schmoeller, Thomas; Do, Mun-hoe; Choi, Jung-Hoe
2014-03-01
scanning electron microscope (SEM) measurements. High resist impact and difficult model data acquisition demand for a simulation model that hat is capable of extrapolating reliably beyond its calibration dataset. We use rigorous simulation models to provide that predictive performance. We have discussed the need of a rigorous mask optimization process for DRAM contact cell layout yielding mask layouts that are optimal in process performance, mask manufacturability and accuracy. In this paper, we have shown the step by step process from analytical illumination source derivation, a NTD and application tailored model calibration to layout optimization such as OPC and SRAF placement. Finally the work has been verified with simulation and experimental results on wafer.
Numerical Modeling of Shoreline Undulations
DEFF Research Database (Denmark)
Kærgaard, Kasper Hauberg
model has been developed which describes the longshore sediment transport along arbitrarily shaped shorelines. The numerical model is based on a spectral wave model, a depth integrated flow model, a wave-phase resolving sediment transport description and a one-line shoreline model. First the theoretical...... of the feature and under predicts the migration speeds of the features. On the second shoreline, the shoreline model predicts undulations lengths which are longer than the observed undulations. Lastly the thesis considers field measurements of undulations of the bottom bathymetry along an otherwise straight...... length of the shoreline undulations is determined in the linear regime using a shoreline stability analysis based on the numerical model. The analysis shows that the length of the undulations in the linear regime depends on the incoming wave conditions and on the coastal profile. For larger waves...
Revisiting the constant growth angle: Estimation and verification via rigorous thermal modeling
Virozub, Alexander; Rasin, Igal G.; Brandon, Simon
2008-12-01
Methods for estimating growth angle ( θgr) values, based on the a posteriori analysis of directionally solidified material (e.g. drops) often involve assumptions of negligible gravitational effects as well as a planar solid/liquid interface during solidification. We relax both of these assumptions when using experimental drop shapes from the literature to estimate the relevant growth angles at the initial stages of solidification. Assumed to be constant, we use these values as input into a rigorous heat transfer and solidification model of the growth process. This model, which is shown to reproduce the experimental shape of a solidified sessile water drop using the literature value of θgr=0∘, yields excellent agreement with experimental profiles using our estimated values for silicon ( θgr=10∘) and germanium ( θgr=14.3∘) solidifying on an isotropic crystalline surface. The effect of gravity on the solidified drop shape is found to be significant in the case of germanium, suggesting that gravity should either be included in the analysis or that care should be taken that the relevant Bond number is truly small enough in each measurement. The planar solidification interface assumption is found to be unjustified. Although this issue is important when simulating the inflection point in the profile of the solidified water drop, there are indications that solidified drop shapes (at least in the case of silicon) may be fairly insensitive to the shape of this interface.
A Generic Model for Relative Adjustment Between Optical Sensors Using Rigorous Orbit Mechanics
Directory of Open Access Journals (Sweden)
B. Islam
2008-06-01
Full Text Available The classical calibration or space resection is the fundamental task in photogrammetry. The lack of sufficient knowledge of interior and exterior orientation parameters lead to unreliable results in the photogrammetric process. One of the earliest in approaches using in photogrammetry was the plumb line calibration method. This method is suitable to recover the radial and decentering lens distortion coefficients, while the remaining interior(focal length and principal point coordinates and exterior orientation parameters have to be determined by a complimentary method. As the lens distortion remains very less it not considered as the interior orientation parameters, in the present rigorous sensor model. There are several other available methods based on the photogrammetric collinearity equations, which consider the determination of exterior orientation parameters, with no mention to the simultaneous determination of inner orientation parameters. Normal space resection methods solve the problem using control points, whose coordinates are known both in image and object reference systems. The non-linearity of the model and the problems, in point location in digital images and identifying the maximum GPS measured control points are the main drawbacks of the classical approaches. This paper addresses mathematical model based on the fundamental assumption of collineariy of three points of two Along-Track Stereo imagery sensors and independent object point. Assuming this condition it is possible to extract the exterior orientation (EO parameters for a long strip and single image together, without and with using the control points. Moreover, after extracting the EO parameters the accuracy for satellite data products are compared in with using single and with no control points.
Mathematical and numerical foundations of turbulence models and applications
Chacón Rebollo, Tomás
2014-01-01
With applications to climate, technology, and industry, the modeling and numerical simulation of turbulent flows are rich with history and modern relevance. The complexity of the problems that arise in the study of turbulence requires tools from various scientific disciplines, including mathematics, physics, engineering, and computer science. Authored by two experts in the area with a long history of collaboration, this monograph provides a current, detailed look at several turbulence models from both the theoretical and numerical perspectives. The k-epsilon, large-eddy simulation, and other models are rigorously derived and their performance is analyzed using benchmark simulations for real-world turbulent flows. Mathematical and Numerical Foundations of Turbulence Models and Applications is an ideal reference for students in applied mathematics and engineering, as well as researchers in mathematical and numerical fluid dynamics. It is also a valuable resource for advanced graduate students in fluid dynamics,...
Numerical models for differential problems
Quarteroni, Alfio
2017-01-01
In this text, we introduce the basic concepts for the numerical modelling of partial differential equations. We consider the classical elliptic, parabolic and hyperbolic linear equations, but also the diffusion, transport, and Navier-Stokes equations, as well as equations representing conservation laws, saddle-point problems and optimal control problems. Furthermore, we provide numerous physical examples which underline such equations. We then analyze numerical solution methods based on finite elements, finite differences, finite volumes, spectral methods and domain decomposition methods, and reduced basis methods. In particular, we discuss the algorithmic and computer implementation aspects and provide a number of easy-to-use programs. The text does not require any previous advanced mathematical knowledge of partial differential equations: the absolutely essential concepts are reported in a preliminary chapter. It is therefore suitable for students of bachelor and master courses in scientific disciplines, an...
Numerical simulation of Higgs models
International Nuclear Information System (INIS)
Jaster, A.
1995-10-01
The SU(2) Higgs and the Schwinger model on the lattice were analysed. Numerical simulations of the SU(2) Higgs model were performed to study the finite temperature electroweak phase transition. With the help of the multicanonical method the distribution of an order parameter at the phase transition point was measured. This was used to obtain the order of the phase transition and the value of the interface tension with the histogram method. Numerical simulations were also performed at zero temperature to perform renormalization. The measured values for the Wilson loops were used to determine the static potential and from this the renormalized gauge coupling. The Schwinger model was simulated at different gauge couplings to analyse the properties of the Kaplan-Shamir fermions. The prediction that the mass parameter gets only multiplicative renormalization was tested and verified. (orig.)
Directory of Open Access Journals (Sweden)
Kun Hu
2016-09-01
Full Text Available High precision geometric rectification of High Resolution Satellite Imagery (HRSI is the basis of digital mapping and Three-Dimensional (3D modeling. Taking advantage of line features as basic geometric control conditions instead of control points, the Line-Based Transformation Model (LBTM provides a practical and efficient way of image rectification. It is competent to build the mathematical relationship between image space and the corresponding object space accurately, while it reduces the workloads of ground control and feature recognition dramatically. Based on generalization and the analysis of existing LBTMs, a novel rigorous LBTM is proposed in this paper, which can further eliminate the geometric deformation caused by sensor inclination and terrain variation. This improved nonlinear LBTM is constructed based on a generalized point strategy and resolved by least squares overall adjustment. Geo-positioning accuracy experiments with IKONOS, GeoEye-1 and ZiYuan-3 satellite imagery are performed to compare rigorous LBTM with other relevant line-based and point-based transformation models. Both theoretic analysis and experimental results demonstrate that the rigorous LBTM is more accurate and reliable without adding extra ground control. The geo-positioning accuracy of satellite imagery rectified by rigorous LBTM can reach about one pixel with eight control lines and can be further improved by optimizing the horizontal and vertical distribution of control lines.
Plasma modelling and numerical simulation
International Nuclear Information System (INIS)
Van Dijk, J; Kroesen, G M W; Bogaerts, A
2009-01-01
Plasma modelling is an exciting subject in which virtually all physical disciplines are represented. Plasma models combine the electromagnetic, statistical and fluid dynamical theories that have their roots in the 19th century with the modern insights concerning the structure of matter that were developed throughout the 20th century. The present cluster issue consists of 20 invited contributions, which are representative of the state of the art in plasma modelling and numerical simulation. These contributions provide an in-depth discussion of the major theories and modelling and simulation strategies, and their applications to contemporary plasma-based technologies. In this editorial review, we introduce and complement those papers by providing a bird's eye perspective on plasma modelling and discussing the historical context in which it has surfaced. (editorial review)
Numerical model of thyroid counter
Directory of Open Access Journals (Sweden)
Szuchta Maciej
2016-03-01
Full Text Available The aim of this study was to develop a numerical model of spectrometric thyroid counter, which is used for the measurements of internal contamination by in vivo method. The modeled detector is used for a routine internal exposure monitoring procedure in the Radiation Protection Measurements Laboratory of National Centre for Nuclear Research (NCBJ. This procedure may also be used for monitoring of occupationally exposed nuclear medicine personnel. The developed model was prepared using Monte Carlo code FLUKA 2011 ver. 2b.6 Apr-14 and FLAIR ver. 1.2-5 interface. It contains a scintillation NaI(Tl detector, the collimator and the thyroid water phantom with a reference source of iodine 131I. The geometry of the model was designed and a gamma energy spectrum of iodine 131I deposited in the detector was calculated.
Comprehensive numerical modelling of tokamaks
International Nuclear Information System (INIS)
Cohen, R.H.; Cohen, B.I.; Dubois, P.F.
1991-01-01
We outline a plan for the development of a comprehensive numerical model of tokamaks. The model would consist of a suite of independent, communicating packages describing the various aspects of tokamak performance (core and edge transport coefficients and profiles, heating, fueling, magnetic configuration, etc.) as well as extensive diagnostics. These codes, which may run on different computers, would be flexibly linked by a user-friendly shell which would allow run-time specification of packages and generation of pre- and post-processing functions, including workstation-based visualization of output. One package in particular, the calculation of core transport coefficients via gyrokinetic particle simulation, will become practical on the scale required for comprehensive modelling only with the advent of teraFLOP computers. Incremental effort at LLNL would be focused on gyrokinetic simulation and development of the shell
Numerical modeling of foam flows
International Nuclear Information System (INIS)
Cheddadi, Ibrahim
2010-01-01
Liquid foam flows are involved in numerous applications, e.g. food and cosmetics industries, oil extraction, nuclear decontamination. Moreover, their study leads to fundamental knowledge: as it is easier to manipulate and analyse, foam is used as a model material to understand the flow of emulsions, polymers, pastes, or cell aggregates, all of which display both solid and liquid behaviour. Systematic experiments performed by Francois Graner et al. provide precise data that emphasize the non Newtonian properties of the foam. Meanwhile, Pierre Saramito proposed a visco-elasto-plastic continuous tensorial model, akin to predict the behaviour of the foam. The goal of this thesis is to understand this complex behaviour, using these two elements. We have built and validated a resolution algorithm based on a bidimensional finite elements methods. The numerical solutions are in excellent agreement with the spatial distribution of all measured quantities, and confirm the predictive capabilities of the model. The dominant parameters have been identified and we evidenced the fact that the viscous, elastic, and plastic contributions to the flow have to be treated simultaneously in a tensorial formalism. We provide a substantial contribution to the understanding of foams and open the path to realistic simulations of complex VEP flows for industrial applications. (author)
Numerical Modeling of Ocean Circulation
Miller, Robert N.
2007-01-01
The modelling of ocean circulation is important not only for its own sake, but also in terms of the prediction of weather patterns and the effects of climate change. This book introduces the basic computational techniques necessary for all models of the ocean and atmosphere, and the conditions they must satisfy. It describes the workings of ocean models, the problems that must be solved in their construction, and how to evaluate computational results. Major emphasis is placed on examining ocean models critically, and determining what they do well and what they do poorly. Numerical analysis is introduced as needed, and exercises are included to illustrate major points. Developed from notes for a course taught in physical oceanography at the College of Oceanic and Atmospheric Sciences at Oregon State University, this book is ideal for graduate students of oceanography, geophysics, climatology and atmospheric science, and researchers in oceanography and atmospheric science. Features examples and critical examination of ocean modelling and results Demonstrates the strengths and weaknesses of different approaches Includes exercises to illustrate major points and supplement mathematical and physical details
Numerical modelling of fuel sprays
Energy Technology Data Exchange (ETDEWEB)
Bergstroem, C.
1999-06-01
The way the fuel is introduced into the combustion chamber is one of the most important parameters for the power output and the generation of emissions in the combustion of liquid fuels. The interaction between the turbulent gas flow field and the liquid fuel droplets, the vaporisation of them and the mixing of the gaseous fuel with the ambient air that are vital parameters in the combustion process. The use of numerical calculations is an important tool to better understand these complex interacting phenomena. This thesis reports on the numerical modelling of fuel sprays in non-reacting cases using an own developed spray module. The spray module uses the stochastic parcel method to represent the spray. The module was made in such manner that it could by coupled with different gas flow solver. Results obtained from four different gas flow solvers are presented in the thesis, including the use of two different kinds of turbulence models. In the first part the spray module is coupled with a k-{eta} based 2-D cylindrical gas flow solver. A thorough sensitivity analysis was performed on the spray and gas flow solver parameters, such as grid size dependence and sensitivity to initial values of k-{eta}. The results of the spray module were also compared to results from other spray codes, e.g. the well known KIVA code. In the second part of this thesis the spray was injected into a turbulent and fully developed crossflow studied. The spray module was attached to a LES (Large Eddy Simulation) based flow solvers enabling the study of the complex structures and time dependent phenomena involved in spray in crossflows. It was found that the spray performs an oscillatory motion and that the Strouhal number in the wake was about 0.1. Different spray breakup models were evaluated by comparing with experimental results 66 refs, 56 figs
Scientific rigor through videogames.
Treuille, Adrien; Das, Rhiju
2014-11-01
Hypothesis-driven experimentation - the scientific method - can be subverted by fraud, irreproducibility, and lack of rigorous predictive tests. A robust solution to these problems may be the 'massive open laboratory' model, recently embodied in the internet-scale videogame EteRNA. Deploying similar platforms throughout biology could enforce the scientific method more broadly. Copyright © 2014 Elsevier Ltd. All rights reserved.
Simic, Vladimir
2016-06-01
As the number of end-of-life vehicles (ELVs) is estimated to increase to 79.3 million units per year by 2020 (e.g., 40 million units were generated in 2010), there is strong motivation to effectively manage this fast-growing waste flow. Intensive work on management of ELVs is necessary in order to more successfully tackle this important environmental challenge. This paper proposes an interval-parameter chance-constraint programming model for end-of-life vehicles management under rigorous environmental regulations. The proposed model can incorporate various uncertainty information in the modeling process. The complex relationships between different ELV management sub-systems are successfully addressed. Particularly, the formulated model can help identify optimal patterns of procurement from multiple sources of ELV supply, production and inventory planning in multiple vehicle recycling factories, and allocation of sorted material flows to multiple final destinations under rigorous environmental regulations. A case study is conducted in order to demonstrate the potentials and applicability of the proposed model. Various constraint-violation probability levels are examined in detail. Influences of parameter uncertainty on model solutions are thoroughly investigated. Useful solutions for the management of ELVs are obtained under different probabilities of violating system constraints. The formulated model is able to tackle a hard, uncertainty existing ELV management problem. The presented model has advantages in providing bases for determining long-term ELV management plans with desired compromises between economic efficiency of vehicle recycling system and system-reliability considerations. The results are helpful for supporting generation and improvement of ELV management plans. Copyright © 2016 Elsevier Ltd. All rights reserved.
Thermal Impact Assessment of Groundwater Heat Pumps (GWHPs: Rigorous vs. Simplified Models
Directory of Open Access Journals (Sweden)
Bruno Piga
2017-09-01
Full Text Available Groundwater Heat Pumps (GWHPs are increasingly adopted for air conditioning in urban areas, thus reducing CO2 emissions, and this growth needs to be managed to ensure the sustainability of the thermal alteration of aquifers. However, few studies have addressed the propagation of thermal plumes from open-loop geothermal systems from a long-term perspective. We provide a comprehensive sensitivity analysis, performed with numerical finite-element simulations, to assess how the size of the thermally affected zone is driven by hydrodynamic and thermal subsurface properties, the vadose zone and aquifer thickness, and plant setup. In particular, we focus the analysis on the length and width of thermal plumes, and on their time evolution. Numerical simulations are compared with two simplified methods, namely (i replacing the time-varying thermal load with its yearly average and (ii analytical formulae for advective heat transport in the aquifer. The former proves acceptable for the assessment of plume length, while the latter can be used to estimate the width of the thermally affected zone. The results highlight the strong influence of groundwater velocity on the plume size and, especially for its long-term evolution, of ground thermal properties and of subsurface geometrical parameters.
Numerical modeling of slow shocks
International Nuclear Information System (INIS)
Winske, D.
1987-01-01
This paper reviews previous attempt and the present status of efforts to understand the structure of slow shocks by means of time dependent numerical calculations. Studies carried out using MHD or hybrid-kinetic codes have demonstrated qualitative agreement with theory. A number of unresolved issues related to hybrid simulations of the internal shock structure are discussed in some detail. 43 refs., 8 figs
Exactly solvable models: the way towards a rigorous treatment of phase transitions in finite systems
International Nuclear Information System (INIS)
Bugaev, K.A.
2007-01-01
The exact analytical solutions of a variety of statistical models recently obtained for finite systems are thoroughly discussed. Among them are a constrained version of the statistical multifragmentation model, the Bag Model of Gases and the Hills and Dales Model of surface partition. The finite volume analytical solutions of these models were obtained by a novel powerful mathematical method - the Laplace-Fourier transform. The Laplace-Fourier transform allows one to study the nuclear matter equation of state, the equation of state of hadronic and quark-gluon plasma and the surface entropy of large clusters on the same footing. A complete analysis of the isobaric partition singularities of these models is done for finite systems. The developed formalism allows one to exactly define the finite volume analogs of gaseous, liquid and mixed phases of these models from the first principles of statistical mechanics [ru
McCaig, Chris; Begon, Mike; Norman, Rachel; Shankland, Carron
2011-03-01
Changing scale, for example, the ability to move seamlessly from an individual-based model to a population-based model, is an important problem in many fields. In this paper, we introduce process algebra as a novel solution to this problem in the context of models of infectious disease spread. Process algebra allows us to describe a system in terms of the stochastic behaviour of individuals, and is a technique from computer science. We review the use of process algebra in biological systems, and the variety of quantitative and qualitative analysis techniques available. The analysis illustrated here solves the changing scale problem: from the individual behaviour we can rigorously derive equations to describe the mean behaviour of the system at the level of the population. The biological problem investigated is the transmission of infection, and how this relates to individual interactions.
Numerical Modelling of Electrical Discharges
International Nuclear Information System (INIS)
Durán-Olivencia, F J; Pontiga, F; Castellanos, A
2014-01-01
The problem of the propagation of an electrical discharge between a spherical electrode and a plane has been solved by means of finite element methods (FEM) using a fluid approximation and assuming weak ionization and local equilibrium with the electric field. The numerical simulation of this type of problems presents the usual difficulties of convection-diffusion-reaction problems, in addition to those associated with the nonlinearities of the charged species velocities, the formation of steep gradients of the electric field and particle densities, and the coexistence of very different temporal scales. The effect of using different temporal discretizations for the numerical integration of the corresponding system of partial differential equations will be here investigated. In particular, the so-called θ-methods will be used, which allows to implement implicit, semi-explicit and fully explicit schemes in a simple way
Qian, Ma; Ma, Jie
2009-06-07
Fletcher's spherical substrate model [J. Chem. Phys. 29, 572 (1958)] is a basic model for understanding the heterogeneous nucleation phenomena in nature. However, a rigorous thermodynamic formulation of the model has been missing due to the significant complexities involved. This has not only left the classical model deficient but also likely obscured its other important features, which would otherwise have helped to better understand and control heterogeneous nucleation on spherical substrates. This work presents a rigorous thermodynamic formulation of Fletcher's model using a novel analytical approach and discusses the new perspectives derived. In particular, it is shown that the use of an intermediate variable, a selected geometrical angle or pseudocontact angle between the embryo and spherical substrate, revealed extraordinary similarities between the first derivatives of the free energy change with respect to embryo radius for nucleation on spherical and flat substrates. Enlightened by the discovery, it was found that there exists a local maximum in the difference between the equivalent contact angles for nucleation on spherical and flat substrates due to the existence of a local maximum in the difference between the shape factors for nucleation on spherical and flat substrate surfaces. This helps to understand the complexity of the heterogeneous nucleation phenomena in a practical system. Also, it was found that the unfavorable size effect occurs primarily when R<5r( *) (R: radius of substrate and r( *): critical embryo radius) and diminishes rapidly with increasing value of R/r( *) beyond R/r( *)=5. This finding provides a baseline for controlling the size effects in heterogeneous nucleation.
International Nuclear Information System (INIS)
Adam, G.; Adam, S.
2007-01-01
The Green function (GF) equation of motion technique for solving the effective two-band Hubbard model of high-T c superconductivity in cuprates rests on the Hubbard operator (HO) algebra. We show that, if we take into account the invariance to translations and spin reversal, the HO algebra results in invariance properties of several specific correlation functions. The use of these properties allows rigorous derivation and simplification of the expressions of the frequency matrix (FM) and of the generalized mean-field approximation (GMFA) Green functions (GFs) of the model. For the normal singlet hopping and anomalous exchange pairing correlation functions which enter the FM and GMFA-GFs, the use of spectral representations allows the identification and elimination of exponentially small quantities. This procedure secures the reduction of the correlation order to the GMFA-GF expressions
National Research Council Canada - National Science Library
Petkovska, Menka; Antov-Bozalo, Danijela; Nikacevic, Nikola
2006-01-01
The general objective of the project is fundamental mathematical modeling of a complex TSA system with electrothermal desorption step, with absorbers assembled of one or more cartridge-type, radial...
National Research Council Canada - National Science Library
Petkovska, Menka; Antov-Bozalo, Danijela; Markovic, Ana
2005-01-01
The general objective of the project is fundamental mathematical modeling of a complex TSA system with electrothermal desorption step, with adsorbers assembled of one or more activated carbon fiber clot (ACFC...
Directory of Open Access Journals (Sweden)
Christian Nowke
2018-06-01
Full Text Available Simulation models in many scientific fields can have non-unique solutions or unique solutions which can be difficult to find. Moreover, in evolving systems, unique final state solutions can be reached by multiple different trajectories. Neuroscience is no exception. Often, neural network models are subject to parameter fitting to obtain desirable output comparable to experimental data. Parameter fitting without sufficient constraints and a systematic exploration of the possible solution space can lead to conclusions valid only around local minima or around non-minima. To address this issue, we have developed an interactive tool for visualizing and steering parameters in neural network simulation models. In this work, we focus particularly on connectivity generation, since finding suitable connectivity configurations for neural network models constitutes a complex parameter search scenario. The development of the tool has been guided by several use cases—the tool allows researchers to steer the parameters of the connectivity generation during the simulation, thus quickly growing networks composed of multiple populations with a targeted mean activity. The flexibility of the software allows scientists to explore other connectivity and neuron variables apart from the ones presented as use cases. With this tool, we enable an interactive exploration of parameter spaces and a better understanding of neural network models and grapple with the crucial problem of non-unique network solutions and trajectories. In addition, we observe a reduction in turn around times for the assessment of these models, due to interactive visualization while the simulation is computed.
International Nuclear Information System (INIS)
Takahashi, A.; Rusch, D.
1979-07-01
Some recent neutronics experiments for fusion reactor blankets show that the precise treatment of anisotropic secondary emissions for all types of neutron scattering is needed for neutron transport calculations. In the present work new rigorous methods, i.e. based on non-approximative microscopic neutron balance equations, are applied to treat the anisotropic collision source term in transport equations. The collision source calculation is free from approximations except for the discretization of energy, angle and space variables and includes the rigorous treatment of nonelastic collisions, as far as nuclear data are given. Two methods are presented: first the Ii-method, which relies on existing nuclear data files and then, as an ultimate goal, the I*-method, which aims at the use of future double-differential cross section data, but which is also applicable to the present single-differential data basis to allow a smooth transition to the new data type. An application of the Ii-method is given in the code system NITRAN which employs the Ssub(N)-method to solve the transport equations. Both rigorous methods, the Ii- and the I*-method, are applicable to all radiation transport problems and they can be used also in the Monte-Carlo-method to solve the transport problem. (orig./RW) [de
Hartree-Fock-Bogoliubov model: a theoretical and numerical perspective
International Nuclear Information System (INIS)
Paul, S.
2012-01-01
This work is devoted to the theoretical and numerical study of Hartree-Fock-Bogoliubov (HFB) theory for attractive quantum systems, which is one of the main methods in nuclear physics. We first present the model and its main properties, and then explain how to get numerical solutions. We prove some convergence results, in particular for the simple fixed point algorithm (sometimes called Roothaan). We show that it converges, or oscillates between two states, none of them being a solution. This generalizes to the HFB case previous results of Cances and Le Bris for the simpler Hartree-Fock model in the repulsive case. Following these authors, we also propose a relaxed constraint algorithm for which convergence is guaranteed. In the last part of the thesis, we illustrate the behavior of these algorithms by some numerical experiments. We first consider a system where the particles only interact through the Newton potential. Our numerical results show that the pairing matrix never vanishes, a fact that has not yet been proved rigorously. We then study a very simplified model for protons and neutrons in a nucleus. (author)
DEFF Research Database (Denmark)
Frutiger, Jerome; Abildskov, Jens; Sin, Gürkan
) weighted-least-square regression. 3) Initialization of estimation by use of linear algebra providing a first guess. 4) Sequential parameter and simultaneous GC parameter by using of 4 different minimization algorithms. 5) Thorough uncertainty analysis: a) based on asymptotic approximation of parameter...... covariance matrix b) based on boot strap method. Providing 95%-confidence intervals of parameters and predicted property. 6) Performance statistics analysis and model application. The application of the methodology is shown for a new GC model built to predict lower flammability limit (LFL) for refrigerants...... their credibility and robustness in wider industrial and scientific applications....
Numerical modelling in material physics
International Nuclear Information System (INIS)
Proville, L.
2004-12-01
The author first briefly presents his past research activities: investigation of a dislocation sliding in solid solution by molecular dynamics, modelling of metal film growth by phase field and Monte Carlo kinetics, phase field model for surface self-organisation, phase field model for the Al 3 Zr alloy, calculation of anharmonic photons, mobility of bipolarons in superconductors. Then, he more precisely reports the mesoscopic modelling in phase field, and some atomistic modelling (dislocation sliding, Monte Carlo simulation of metal surface growth, anharmonic network optical spectrum modelling)
Numerical modelling approach for mine backfill
Indian Academy of Sciences (India)
Muhammad Zaka Emad
2017-07-24
Jul 24, 2017 ... conditions. This paper discusses a numerical modelling strategy for modelling mine backfill material. The .... placed in an ore pass that leads the ore to the ore bin and crusher, from ... 1 year, depending on the mine plan.
Numerical models of planetary dynamos
International Nuclear Information System (INIS)
Glatzmaier, G.A.; Roberts, P.H.
1992-01-01
We describe a nonlinear, axisymmetric, spherical-shell model of planetary dynamos. This intermediate-type dynamo model requires a prescribed helicity field (the alpha effect) and a prescribed buoyancy force or thermal wind (the omega effect) and solves for the axisymmetric time-dependent magnetic and velocity fields. Three very different time dependent solutions are obtained from different prescribed sets of alpha and omega fields
International Nuclear Information System (INIS)
ZareNezhad, Bahman; Mottahedin, Mona
2012-01-01
Highlights: ► A mechanistic model for predicting gas hydrate formation kinetics is presented. ► A secondary nucleation rate model is proposed for the first time. ► Crystal–crystal collisions and crystal–impeller collisions are distinguished. ► Simultaneous determination of nucleation and growth kinetics are established. ► Important for design of gas hydrate based energy storage and CO 2 recovery systems. - Abstract: A rigorous mechanistic model for predicting gas hydrate formation crystallization kinetics is presented and the special case of CO 2 gas hydrate formation regarding CO 2 recovery and sequestration processes has been investigated by using the proposed model. A physical model for prediction of secondary nucleation rate is proposed for the first time and the formation rates of secondary nuclei by crystal–crystal collisions and crystal–impeller collisions are formulated. The objective functions for simultaneous determination of nucleation and growth kinetics are presented and a theoretical framework for predicting the dynamic behavior of gas hydrate formation is presented. Predicted time variations of CO 2 content, total number and surface area of produced hydrate crystals are in good agreement with the available experimental data. The proposed approach can have considerable application for design of gas hydrate converters regarding energy storage and CO 2 recovery processes.
Numerical Modeling of Microelectrochemical Systems
DEFF Research Database (Denmark)
Adesokan, Bolaji James
incorporates the finite size of ionic species in the transport equation. The model presents a more appropriate boundary conditions which describe the modified Butler-Volmer reaction kinetics and account for the surface capacitance of the thin electric double layer. We also have found analytical solution...... at the electrode in a microelectrochemical system. In our analysis, we account for the finite size properties of ions in the mass and the charge transport of ionic species in an electrochemical system. This term characterizes the saturation of the ionic species close to the electrode surface. We then analyse......The PhD dissertation is concerned with mathematical modeling and simulation of electrochemical systems. The first three chapters of the thesis consist of the introductory part, the model development chapter and the chapter on the summary of the main results. The remaining three chapters report...
Mathematical and Numerical Modeling in Maritime Geomechanics
Directory of Open Access Journals (Sweden)
Miguel Martín Stickle
2012-04-01
Full Text Available A theoretical and numerical framework to model the foundation of marine offshore structures is presented. The theoretical model is composed by a system of partial differential equations describing coupling between seabed solid skeleton and pore fluids (water, air, oil,... combined with a system of ordinary differential equations describing the specific constitutive relation of the seabed soil skeleton. Once the theoretical model is described, the finite element numerical procedure to achieve an approximate solution of the overning equations is outlined. In order to validate the proposed theoretical and numerical framework the seaward tilt mechanism induced by the action of breaking waves over a vertical breakwater is numerically reproduced. The results numerically attained are in agreement with the main conclusions drawn from the literature associated with this failure mechanism.
Numerical modelling of reflood processes
International Nuclear Information System (INIS)
Glynn, D.R.; Rhodes, N.; Tatchell, D.G.
1983-01-01
The use of a detailed computer model to investigate the effects of grid size and the choice of wall-to-fluid heat-transfer correlations on the predictions obtained for reflooding of a vertical heated channel is described. The model employs equations for the momentum and enthalpy of vapour and liquid and hence accounts for both thermal non-equilibrium and slip between the phases. Empirical correlations are used to calculate interphase and wall-to-fluid friction and heat-transfer as functions of flow regime and local conditions. The empirical formulae have remained fixed with the exception of the wall-to-fluid heat-transfer correlations. These have been varied according to the practices adopted in other computer codes used to model reflood, namely REFLUX, RELAP and TRAC. Calculations have been performed to predict the CSNI standard problem number 7, and the results are compared with experiment. It is shown that the results are substantially grid-independent, and that the choice of correlation has a significant influence on the general flow behaviour, the rate of quenching and on the maximum cladding temperature predicted by the model. It is concluded that good predictions of reflooding rates can be obtained with particular correlation sets. (author)
Recent advances in numerical modeling of detonations
Energy Technology Data Exchange (ETDEWEB)
Mader, C.L.
1986-12-01
Three lectures were presented on recent advances in numerical modeling detonations entitled (1) Jet Initiation and Penetration of Explosives; (2) Explosive Desensitization by Preshocking; (3) Inert Metal-Loaded Explosives.
A numerical reference model for themomechanical subduction
DEFF Research Database (Denmark)
Quinquis, Matthieu; Chemia, Zurab; Tosi, Nicola
2010-01-01
Building an advanced numerical model of subduction requires choosing values for various geometrical parameters and material properties, among others, the initial lithosphere thicknesses, representative lithological types and their mechanical and thermal properties, rheologies, initial temperature...
Other relevant numerical modelling papers
International Nuclear Information System (INIS)
Chartier, M.
1989-01-01
The ocean modelling is a rapidly evolving science and a large number of results have been published. Several categories of papers are of particular interest for this review: the papers published by the international atomic institutions, such as the NEA (for the CRESP or Subseabed Programs), the IAEA (for example the Safety Series, the Technical Report Series or the TECDOC), and the ICRP, and the papers concerned by more fundamental research, which are published in specific scientific literature. This paper aims to list some of the most relevant publications for the CRESP purposes. It means by no way to be exhaustive, but informative on the incontestable progress recently achieved in that field. One should note that some of these papers are so recent that their final version has not yet been published
Numerical modelling of elastic space tethers
DEFF Research Database (Denmark)
Kristiansen, Kristian Uldall; Palmer, P. L.; Roberts, R. M.
2012-01-01
In this paper the importance of the ill-posedness of the classical, non-dissipative massive tether model on an orbiting tether system is studied numerically. The computations document that via the regularisation of bending resistance a more reliable numerical integrator can be produced. Furthermo....... It is also shown that on the slow manifold the dynamics of the satellites are well-approximated by the finite dimensional slack-spring model....
Numerical models of groundwater flow and transport
International Nuclear Information System (INIS)
Konikow, L.F.
1996-01-01
This chapter reviews the state-of-the-art in deterministic modeling of groundwater flow and transport processes, which can be used for interpretation of isotope data through groundwater flow analyses. Numerical models which are available for this purpose are described and their applications to complex field problems are discussed. The theoretical bases of deterministic modeling are summarized, and advantages and limitations of numerical models are described. The selection of models for specific applications and their calibration procedures are described, and results of a few illustrative case study type applications are provided. (author). 145 refs, 17 figs, 2 tabs
Numerical models of groundwater flow and transport
Energy Technology Data Exchange (ETDEWEB)
Konikow, L F [Geological Survey, Reston, VA (United States)
1996-10-01
This chapter reviews the state-of-the-art in deterministic modeling of groundwater flow and transport processes, which can be used for interpretation of isotope data through groundwater flow analyses. Numerical models which are available for this purpose are described and their applications to complex field problems are discussed. The theoretical bases of deterministic modeling are summarized, and advantages and limitations of numerical models are described. The selection of models for specific applications and their calibration procedures are described, and results of a few illustrative case study type applications are provided. (author). 145 refs, 17 figs, 2 tabs.
Changyong, Dou; Huadong, Guo; Chunming, Han; yuquan, Liu; Xijuan, Yue; Yinghui, Zhao
2014-03-01
Raw signal simulation is a useful tool for the system design, mission planning, processing algorithm testing, and inversion algorithm design of Synthetic Aperture Radar (SAR). Due to the wide and high frequent variation of aircraft's trajectory and attitude, and the low accuracy of the Position and Orientation System (POS)'s recording data, it's difficult to quantitatively study the sensitivity of the key parameters, i.e., the baseline length and inclination, absolute phase and the orientation of the antennas etc., of the airborne Interferometric SAR (InSAR) system, resulting in challenges for its applications. Furthermore, the imprecise estimation of the installation offset between the Global Positioning System (GPS), Inertial Measurement Unit (IMU) and the InSAR antennas compounds the issue. An airborne interferometric SAR (InSAR) simulation based on the rigorous geometric model and real navigation data is proposed in this paper, providing a way for quantitatively studying the key parameters and for evaluating the effect from the parameters on the applications of airborne InSAR, as photogrammetric mapping, high-resolution Digital Elevation Model (DEM) generation, and surface deformation by Differential InSAR technology, etc. The simulation can also provide reference for the optimal design of the InSAR system and the improvement of InSAR data processing technologies such as motion compensation, imaging, image co-registration, and application parameter retrieval, etc.
International Nuclear Information System (INIS)
Changyong, Dou; Huadong, Guo; Chunming, Han; Yuquan, Liu; Xijuan, Yue; Yinghui, Zhao
2014-01-01
Raw signal simulation is a useful tool for the system design, mission planning, processing algorithm testing, and inversion algorithm design of Synthetic Aperture Radar (SAR). Due to the wide and high frequent variation of aircraft's trajectory and attitude, and the low accuracy of the Position and Orientation System (POS)'s recording data, it's difficult to quantitatively study the sensitivity of the key parameters, i.e., the baseline length and inclination, absolute phase and the orientation of the antennas etc., of the airborne Interferometric SAR (InSAR) system, resulting in challenges for its applications. Furthermore, the imprecise estimation of the installation offset between the Global Positioning System (GPS), Inertial Measurement Unit (IMU) and the InSAR antennas compounds the issue. An airborne interferometric SAR (InSAR) simulation based on the rigorous geometric model and real navigation data is proposed in this paper, providing a way for quantitatively studying the key parameters and for evaluating the effect from the parameters on the applications of airborne InSAR, as photogrammetric mapping, high-resolution Digital Elevation Model (DEM) generation, and surface deformation by Differential InSAR technology, etc. The simulation can also provide reference for the optimal design of the InSAR system and the improvement of InSAR data processing technologies such as motion compensation, imaging, image co-registration, and application parameter retrieval, etc
Analytical and numerical modeling of sandbanks dynamics
Idier, Deborah; Astruc, Dominique
2003-01-01
Linear and nonlinear behavior of large-scale underwater bedform patterns like sandbanks are studied using linear stability analysis and numerical modeling. The model is based on depth-integrated hydrodynamics equations with a quadratic bottom friction law and a bed load sediment transport model
Numerical 3-D Modelling of Overflows
DEFF Research Database (Denmark)
Larsen, Torben; Nielsen, L.; Jensen, B.
2008-01-01
-dimensional so-called Volume of Fluid Models (VOF-models) based on the full Navier-Stokes equations (named NS3 and developed by DHI Water & Environment) As a general conclusion, the two numerical models show excellent results when compared with measurements. However, considerable errors occur when...
Ferrofluids: Modeling, numerical analysis, and scientific computation
Tomas, Ignacio
This dissertation presents some developments in the Numerical Analysis of Partial Differential Equations (PDEs) describing the behavior of ferrofluids. The most widely accepted PDE model for ferrofluids is the Micropolar model proposed by R.E. Rosensweig. The Micropolar Navier-Stokes Equations (MNSE) is a subsystem of PDEs within the Rosensweig model. Being a simplified version of the much bigger system of PDEs proposed by Rosensweig, the MNSE are a natural starting point of this thesis. The MNSE couple linear velocity u, angular velocity w, and pressure p. We propose and analyze a first-order semi-implicit fully-discrete scheme for the MNSE, which decouples the computation of the linear and angular velocities, is unconditionally stable and delivers optimal convergence rates under assumptions analogous to those used for the Navier-Stokes equations. Moving onto the much more complex Rosensweig's model, we provide a definition (approximation) for the effective magnetizing field h, and explain the assumptions behind this definition. Unlike previous definitions available in the literature, this new definition is able to accommodate the effect of external magnetic fields. Using this definition we setup the system of PDEs coupling linear velocity u, pressure p, angular velocity w, magnetization m, and magnetic potential ϕ We show that this system is energy-stable and devise a numerical scheme that mimics the same stability property. We prove that solutions of the numerical scheme always exist and, under certain simplifying assumptions, that the discrete solutions converge. A notable outcome of the analysis of the numerical scheme for the Rosensweig's model is the choice of finite element spaces that allow the construction of an energy-stable scheme. Finally, with the lessons learned from Rosensweig's model, we develop a diffuse-interface model describing the behavior of two-phase ferrofluid flows and present an energy-stable numerical scheme for this model. For a
Comparing numerically exact and modelled static friction
Directory of Open Access Journals (Sweden)
Krengel Dominik
2017-01-01
Full Text Available Currently there exists no mechanically consistent “numerically exact” implementation of static and dynamic Coulomb friction for general soft particle simulations with arbitrary contact situations in two or three dimension, but only along one dimension. We outline a differential-algebraic equation approach for a “numerically exact” computation of friction in two dimensions and compare its application to the Cundall-Strack model in some test cases.
Reactor Thermal Hydraulic Numerical Calculation And Modeling
International Nuclear Information System (INIS)
Duong Ngoc Hai; Dang The Ba
2008-01-01
In the paper the results of analysis of thermal hydraulic state models using the numerical codes such as COOLOD, EUREKA and RELAP5 for simulation of the reactor thermal hydraulic states are presented. The calculations, analyses of reactor thermal hydraulic state and safety were implemented using different codes. The received numerical results, which were compared each to other, to experiment measurement of Dalat (Vietnam) research reactor and published results, show their appropriateness and capacity for analyses of different appropriate cases. (author)
Numerical Modeling of Ablation Heat Transfer
Ewing, Mark E.; Laker, Travis S.; Walker, David T.
2013-01-01
A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.
Numerical methods and modelling for engineering
Khoury, Richard
2016-01-01
This textbook provides a step-by-step approach to numerical methods in engineering modelling. The authors provide a consistent treatment of the topic, from the ground up, to reinforce for students that numerical methods are a set of mathematical modelling tools which allow engineers to represent real-world systems and compute features of these systems with a predictable error rate. Each method presented addresses a specific type of problem, namely root-finding, optimization, integral, derivative, initial value problem, or boundary value problem, and each one encompasses a set of algorithms to solve the problem given some information and to a known error bound. The authors demonstrate that after developing a proper model and understanding of the engineering situation they are working on, engineers can break down a model into a set of specific mathematical problems, and then implement the appropriate numerical methods to solve these problems. Uses a “building-block” approach, starting with simpler mathemati...
On the Hughes model and numerical aspects
Gomes, Diogo A.
2017-01-05
We study a crowd model proposed by R. Hughes in [11] and we describe a numerical approach to solve it. This model comprises a Fokker-Planck equation coupled with an eikonal equation with Dirichlet or Neumann data. First, we establish a priori estimates for the solutions. Second, we study radial solutions and identify a shock formation mechanism. Third, we illustrate the existence of congestion, the breakdown of the model, and the trend to the equilibrium. Finally, we propose a new numerical method and consider two examples.
On the Hughes model and numerical aspects
Gomes, Diogo A.; Machado Velho, Roberto
2017-01-01
We study a crowd model proposed by R. Hughes in [11] and we describe a numerical approach to solve it. This model comprises a Fokker-Planck equation coupled with an eikonal equation with Dirichlet or Neumann data. First, we establish a priori
Fundamentals of Numerical Modelling of Casting Processes
DEFF Research Database (Denmark)
Hattel, Jesper Henri; Pryds, Nini; Thorborg, Jesper
Fundamentals of Numerical Modelling of Casting Processes comprises a thorough presentation of the basic phenomena that need to be addressed in numerical simulation of casting processes. The main philosophy of the book is to present the topics in view of their physical meaning, whenever possible......, rather than relying strictly on mathematical formalism. The book, aimed both at the researcher and the practicing engineer, as well as the student, is naturally divided into four parts. Part I (Chapters 1-3) introduces the fundamentals of modelling in a 1-dimensional framework. Part II (Chapter 4...
Numerical modeling techniques for flood analysis
Anees, Mohd Talha; Abdullah, K.; Nawawi, M. N. M.; Ab Rahman, Nik Norulaini Nik; Piah, Abd. Rahni Mt.; Zakaria, Nor Azazi; Syakir, M. I.; Mohd. Omar, A. K.
2016-12-01
Topographic and climatic changes are the main causes of abrupt flooding in tropical areas. It is the need to find out exact causes and effects of these changes. Numerical modeling techniques plays a vital role for such studies due to their use of hydrological parameters which are strongly linked with topographic changes. In this review, some of the widely used models utilizing hydrological and river modeling parameters and their estimation in data sparse region are discussed. Shortcomings of 1D and 2D numerical models and the possible improvements over these models through 3D modeling are also discussed. It is found that the HEC-RAS and FLO 2D model are best in terms of economical and accurate flood analysis for river and floodplain modeling respectively. Limitations of FLO 2D in floodplain modeling mainly such as floodplain elevation differences and its vertical roughness in grids were found which can be improve through 3D model. Therefore, 3D model was found to be more suitable than 1D and 2D models in terms of vertical accuracy in grid cells. It was also found that 3D models for open channel flows already developed recently but not for floodplain. Hence, it was suggested that a 3D model for floodplain should be developed by considering all hydrological and high resolution topographic parameter's models, discussed in this review, to enhance the findings of causes and effects of flooding.
Ehret, Gerd; Bodermann, Bernd; Woehler, Martin
2007-06-01
The optical microscopy is an important instrument for dimensional characterisation or calibration of micro- and nanostructures, e.g. chrome structures on photomasks. In comparison to scanning electron microscopy (possible contamination of the sample) and atomic force microscopy (slow, risk of damage) optical microscopy is a fast and non destructive metrology method. The precise quantitative determination of the linewidth from the microscope image is, however, only possible by knowledge of the geometry of the structures and their consideration in the optical modelling. We compared two different rigorous model approaches, the Rigorous Coupled Wave Analysis (RCWA) and the Finite Elements Method (FEM) for modelling of structures with different edge angles, linewidths, line to space ratios and polarisations. The RCWA method can adapt inclined edges profiles only by a staircase approximation leading to increased modelling errors of the RCWA method. Even today's sophisticated rigorous methods still show problems with TM-polarisation. Therefore both rigorous methods are compared in terms of their convergence for TE and TM- polarisation. Beyond that also the influence of typical illumination wavelengths (365 nm, 248 nm and 193 nm) on the microscope images and their contribution to the measuring uncertainty budget will be discussed.
Basset force in numerical models of saltation
Czech Academy of Sciences Publication Activity Database
Lukerchenko, Nikolay; Dolanský, Jindřich; Vlasák, Pavel
2012-01-01
Roč. 60, č. 4 (2012), s. 277-287 ISSN 0042-790X R&D Projects: GA ČR GA103/09/1718 Institutional research plan: CEZ:AV0Z20600510 Keywords : basset force * bed load transport * numerical model * particle-bed collision Subject RIV: BK - Fluid Dynamics Impact factor: 0.653, year: 2012
Thin sheet numerical modelling of continental collision
Jimenez-Munt, I.; Garcia-Gastellanos, D.; Fernandez, M.
2005-01-01
We study the effects of incorporating surface mass transport and the gravitational potential energy of both crust and lithospheric mantle to the viscous thin sheet approach. Recent 2D (cross-section) numerical models show that surface erosion and sediment transport can play a major role in shaping
Numerical modelling of steel arc welding
International Nuclear Information System (INIS)
Hamide, M.
2008-07-01
Welding is a highly used assembly technique. Welding simulation software would give access to residual stresses and information about the weld's microstructure, in order to evaluate the mechanical resistance of a weld. It would also permit to evaluate the process feasibility when complex geometrical components are to be made, and to optimize the welding sequences in order to minimize defects. This work deals with the numerical modelling of arc welding process of steels. After describing the industrial context and the state of art, the models implemented in TransWeld (software developed at CEMEF) are presented. The set of macroscopic equations is followed by a discussion on their numerical implementation. Then, the theory of re-meshing and our adaptive anisotropic re-meshing strategy are explained. Two welding metal addition techniques are investigated and are compared in terms of the joint size and transient temperature and stresses. The accuracy of the finite element model is evaluated based on experimental results and the results of the analytical solution. Comparative analysis between experimental and numerical results allows the assessment of the ability of the numerical code to predict the thermomechanical and metallurgical response of the welded structure. The models limitations and the phenomena identified during this study are finally discussed and permit to define interesting orientations for future developments. (author)
Numerical modeling of magma-repository interactions
Bokhove, Onno
2001-01-01
This report explains the numerical programs behind a comprehensive modeling effort of magma-repository interactions. Magma-repository interactions occur when a magma dike with high-volatile content magma ascends through surrounding rock and encounters a tunnel or drift filled with either a magmatic
Graphical interpretation of numerical model results
International Nuclear Information System (INIS)
Drewes, D.R.
1979-01-01
Computer software has been developed to produce high quality graphical displays of data from a numerical grid model. The code uses an existing graphical display package (DISSPLA) and overcomes some of the problems of both line-printer output and traditional graphics. The software has been designed to be flexible enough to handle arbitrarily placed computation grids and a variety of display requirements
Adaptive numerical modeling of dynamic crack propagation
International Nuclear Information System (INIS)
Adouani, H.; Tie, B.; Berdin, C.; Aubry, D.
2006-01-01
We propose an adaptive numerical strategy that aims at developing reliable and efficient numerical tools to model dynamic crack propagation and crack arrest. We use the cohesive zone theory as behavior of interface-type elements to model crack. Since the crack path is generally unknown beforehand, adaptive meshing is proposed to model the dynamic crack propagation. The dynamic study requires the development of specific solvers for time integration. As both geometry and finite element mesh of the studied structure evolve in time during transient analysis, the stability behavior of dynamic solver becomes a major concern. For this purpose, we use the space-time discontinuous Galerkin finite element method, well-known to provide a natural framework to manage meshes that evolve in time. As an important result, we prove that the space-time discontinuous Galerkin solver is unconditionally stable, when the dynamic crack propagation is modeled by the cohesive zone theory, which is highly non-linear. (authors)
Numerical modelling in non linear fracture mechanics
Directory of Open Access Journals (Sweden)
Viggo Tvergaard
2007-07-01
Full Text Available Some numerical studies of crack propagation are based on using constitutive models that accountfor damage evolution in the material. When a critical damage value has been reached in a materialpoint, it is natural to assume that this point has no more carrying capacity, as is done numerically in the elementvanish technique. In the present review this procedure is illustrated for micromechanically based materialmodels, such as a ductile failure model that accounts for the nucleation and growth of voids to coalescence, and a model for intergranular creep failure with diffusive growth of grain boundary cavities leading to micro-crack formation. The procedure is also illustrated for low cycle fatigue, based on continuum damage mechanics. In addition, the possibility of crack growth predictions for elastic-plastic solids using cohesive zone models to represent the fracture process is discussed.
Numerical modeling of fires on gas pipelines
International Nuclear Information System (INIS)
Zhao Yang; Jianbo Lai; Lu Liu
2011-01-01
When natural gas is released through a hole on a high-pressure pipeline, it disperses in the atmosphere as a jet. A jet fire will occur when the leaked gas meets an ignition source. To estimate the dangerous area, the shape and size of the fire must be known. The evolution of the jet fire in air is predicted by using a finite-volume procedure to solve the flow equations. The model is three-dimensional, elliptic and calculated by using a compressibility corrected version of the k - ξ turbulence model, and also includes a probability density function/laminar flamelet model of turbulent non-premixed combustion process. Radiation heat transfer is described using an adaptive version of the discrete transfer method. The model is compared with the experiments about a horizontal jet fire in a wind tunnel in the literature with success. The influence of wind and jet velocity on the fire shape has been investigated. And a correlation based on numerical results for predicting the stoichiometric flame length is proposed. - Research highlights: → We developed a model to predict the evolution of turbulent jet diffusion flames. → Measurements of temperature distributions match well with the numerical predictions. → A correlation has been proposed to predict the stoichiometric flame length. → Buoyancy effects are higher in the numerical results. → The radiative heat loss is bigger in the experimental results.
Numerical Modelling Of Pumpkin Balloon Instability
Wakefield, D.
Tensys have been involved in the numerical formfinding and load analysis of architectural stressed membrane structures for 15 years. They have recently broadened this range of activities into the `lighter than air' field with significant involvement in aerostat and heavy-lift hybrid airship design. Since early 2004 they have been investigating pumpkin balloon instability on behalf of the NASA ULDB programme. These studies are undertaken using inTENS, an in-house finite element program suite based upon the Dynamic Relaxation solution method and developed especially for the non-linear analysis and patterning of membrane structures. The paper describes the current state of an investigation that started with a numerical simulation of the lobed cylinder problem first studied by Calladine. The influence of material properties and local geometric deformation on stability is demonstrated. A number of models of complete pumpkin balloons have then been established, including a 64-gore balloon with geometry based upon Julian Nott's Endeavour. This latter clefted dramatically upon initial inflation, a phenomenon that has been reproduced in the numerical model. Ongoing investigations include the introduction of membrane contact modelling into inTENS and correlation studies with the series of large-scale ULDB models currently in preparation.
Numerical Modeling of Piezoelectric Transducers Using Physical Parameters
Cappon, H.; Keesman, K.J.
2012-01-01
Design of ultrasonic equipment is frequently facilitated with numerical models. These numerical models, however, need a calibration step, because usually not all characteristics of the materials used are known. Characterization of material properties combined with numerical simulations and
Numerical modeling in materials science and engineering
Rappaz, Michel; Deville, Michel
2003-01-01
This book introduces the concepts and methodologies related to the modelling of the complex phenomena occurring in materials processing. After a short reminder of conservation laws and constitutive relationships, the authors introduce the main numerical methods: finite differences, finite volumes and finite elements. These techniques are developed in three main chapters of the book that tackle more specific problems: phase transformation, solid mechanics and fluid flow. The two last chapters treat inverse methods to obtain the boundary conditions or the material properties and stochastic methods for microstructural simulation. This book is intended for undergraduate and graduate students in materials science and engineering, mechanical engineering and physics and for engineering professionals or researchers who want to get acquainted with numerical simulation to model and compute materials processing.
Lattice Boltzmann model for numerical relativity.
Ilseven, E; Mendoza, M
2016-02-01
In the Z4 formulation, Einstein equations are written as a set of flux conservative first-order hyperbolic equations that resemble fluid dynamics equations. Based on this formulation, we construct a lattice Boltzmann model for numerical relativity and validate it with well-established tests, also known as "apples with apples." Furthermore, we find that by increasing the relaxation time, we gain stability at the cost of losing accuracy, and by decreasing the lattice spacings while keeping a constant numerical diffusivity, the accuracy and stability of our simulations improve. Finally, in order to show the potential of our approach, a linear scaling law for parallelization with respect to number of CPU cores is demonstrated. Our model represents the first step in using lattice kinetic theory to solve gravitational problems.
Infrared radiation parameterizations in numerical climate models
Chou, Ming-Dah; Kratz, David P.; Ridgway, William
1991-01-01
This study presents various approaches to parameterizing the broadband transmission functions for utilization in numerical climate models. One-parameter scaling is applied to approximate a nonhomogeneous path with an equivalent homogeneous path, and the diffuse transmittances are either interpolated from precomputed tables or fit by analytical functions. Two-parameter scaling is applied to parameterizing the carbon dioxide and ozone transmission functions in both the lower and middle atmosphere. Parameterizations are given for the nitrous oxide and methane diffuse transmission functions.
Advanced Numerical Model for Irradiated Concrete
Energy Technology Data Exchange (ETDEWEB)
Giorla, Alain B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2015-03-01
In this report, we establish a numerical model for concrete exposed to irradiation to address these three critical points. The model accounts for creep in the cement paste and its coupling with damage, temperature and relative humidity. The shift in failure mode with the loading rate is also properly represented. The numerical model for creep has been validated and calibrated against different experiments in the literature [Wittmann, 1970, Le Roy, 1995]. Results from a simplified model are shown to showcase the ability of numerical homogenization to simulate irradiation effects in concrete. In future works, the complete model will be applied to the analysis of the irradiation experiments of Elleuch et al. [1972] and Kelly et al. [1969]. This requires a careful examination of the experimental environmental conditions as in both cases certain critical information are missing, including the relative humidity history. A sensitivity analysis will be conducted to provide lower and upper bounds of the concrete expansion under irradiation, and check if the scatter in the simulated results matches the one found in experiments. The numerical and experimental results will be compared in terms of expansion and loss of mechanical stiffness and strength. Both effects should be captured accordingly by the model to validate it. Once the model has been validated on these two experiments, it can be applied to simulate concrete from nuclear power plants. To do so, the materials used in these concrete must be as well characterized as possible. The main parameters required are the mechanical properties of each constituent in the concrete (aggregates, cement paste), namely the elastic modulus, the creep properties, the tensile and compressive strength, the thermal expansion coefficient, and the drying shrinkage. These can be either measured experimentally, estimated from the initial composition in the case of cement paste, or back-calculated from mechanical tests on concrete. If some
Numerical model simulation of atmospheric coolant plumes
International Nuclear Information System (INIS)
Gaillard, P.
1980-01-01
The effect of humid atmospheric coolants on the atmosphere is simulated by means of a three-dimensional numerical model. The atmosphere is defined by its natural vertical profiles of horizontal velocity, temperature, pressure and relative humidity. Effluent discharge is characterised by its vertical velocity and the temperature of air satured with water vapour. The subject of investigation is the area in the vicinity of the point of discharge, with due allowance for the wake effect of the tower and buildings and, where application, wind veer with altitude. The model equations express the conservation relationships for mometum, energy, total mass and water mass, for an incompressible fluid behaving in accordance with the Boussinesq assumptions. Condensation is represented by a simple thermodynamic model, and turbulent fluxes are simulated by introduction of turbulent viscosity and diffusivity data based on in-situ and experimental water model measurements. The three-dimensional problem expressed in terms of the primitive variables (u, v, w, p) is governed by an elliptic equation system which is solved numerically by application of an explicit time-marching algorithm in order to predict the steady-flow velocity distribution, temperature, water vapour concentration and the liquid-water concentration defining the visible plume. Windstill conditions are simulated by a program processing the elliptic equations in an axisymmetrical revolution coordinate system. The calculated visible plumes are compared with plumes observed on site with a view to validate the models [fr
Numerical modelling of methanol liquid pool fires
Prasad, Kuldeep; Li, Chiping; Kailasanath, K.; Ndubizu, Chuka; Ananth, Ramagopal; Tatem, P. A.
1999-12-01
The focus of this paper is on numerical modelling of methanol liquid pool fires. A mathematical model is first developed to describe the evaporation and burning of a two-dimensional or axisymmetric pool containing pure liquid methanol. Then, the complete set of unsteady, compressible Navier-Stokes equations for reactive flows are solved in the gas phase to describe the convection of the fuel gases away from the pool surface, diffusion of the gases into the surrounding air and the oxidation of the fuel into product species. Heat transfer into the liquid pool and the metal container through conduction, convection and radiation are modelled by solving a modified form of the energy equation. Clausius-Clapeyron relationships are invoked to model the evaporation rate of a two-dimensional pool of pure liquid methanol. The governing equations along with appropriate boundary and interface conditions are solved using the flux-corrected transport algorithm. Numerical results exhibit a flame structure that compares well with experimental observations. Temperature profiles and burning rates were found to compare favourably with experimental data from single- and three-compartment laboratory burners. The model predicts a puffing frequency of approximately 12 Hz for a 1 cm diameter methanol pool in the absence of any air co-flow. It is also observed that increasing the air co-flow velocity helps in stabilizing the diffusion flame, by pushing the vortical structures away from the flame region.
A Numerical Model for Trickle Bed Reactors
Propp, Richard M.; Colella, Phillip; Crutchfield, William Y.; Day, Marcus S.
2000-12-01
Trickle bed reactors are governed by equations of flow in porous media such as Darcy's law and the conservation of mass. Our numerical method for solving these equations is based on a total-velocity splitting, sequential formulation which leads to an implicit pressure equation and a semi-implicit mass conservation equation. We use high-resolution finite-difference methods to discretize these equations. Our solution scheme extends previous work in modeling porous media flows in two ways. First, we incorporate physical effects due to capillary pressure, a nonlinear inlet boundary condition, spatial porosity variations, and inertial effects on phase mobilities. In particular, capillary forces introduce a parabolic component into the recast evolution equation, and the inertial effects give rise to hyperbolic nonconvexity. Second, we introduce a modification of the slope-limiting algorithm to prevent our numerical method from producing spurious shocks. We present a numerical algorithm for accommodating these difficulties, show the algorithm is second-order accurate, and demonstrate its performance on a number of simplified problems relevant to trickle bed reactor modeling.
Numerical modelling of swirling diffusive flames
Directory of Open Access Journals (Sweden)
Parra-Santos Teresa
2016-01-01
Full Text Available Computational Fluid Dynamics has been used to study the mixing and combustion of two confined jets whose setup and operating conditions are those of the benchmark of Roback and Johnson. Numerical model solves 3D transient Navier Stokes for turbulent and reactive flows. Averaged velocity profiles using RNG swirl dominated k-epsilon model have been validated with experimental measurements from other sources for the non reactive case. The combustion model is Probability Density Function. Bearing in mind the annular jet has swirl number over 0.5, a vortex breakdown appears in the axis of the burner. Besides, the sudden expansion with a ratio of 2 in diameter between nozzle exits and the test chamber produces the boundary layer separation with the corresponding torus shape recirculation. Contrasting the mixing and combustion models, the last one produces the reduction of the vortex breakdown.
Aerosol numerical modelling at local scale
International Nuclear Information System (INIS)
Albriet, Bastien
2007-01-01
At local scale and in urban areas, an important part of particulate pollution is due to traffic. It contributes largely to the high number concentrations observed. Two aerosol sources are mainly linked to traffic. Primary emission of soot particles and secondary nanoparticle formation by nucleation. The emissions and mechanisms leading to the formation of such bimodal distribution are still badly understood nowadays. In this thesis, we try to provide an answer to this problematic by numerical modelling. The Modal Aerosol Model MAM is used, coupled with two 3D-codes: a CFD (Mercure Saturne) and a CTM (Polair3D). A sensitivity analysis is performed, at the border of a road but also in the first meters of an exhaust plume, to identify the role of each process involved and the sensitivity of different parameters used in the modelling. (author) [fr
Posttraumatic Orbital Emphysema: A Numerical Model
Directory of Open Access Journals (Sweden)
Andrzej Skorek
2014-01-01
Full Text Available Orbital emphysema is a common symptom accompanying orbital fracture. The pathomechanism is still not recognized and the usually assumed cause, elevated pressure in the upper airways connected with sneezing or coughing, does not always contribute to the occurrence of this type of fracture. Observations based on the finite model (simulating blowout type fracture of the deformations of the inferior orbital wall after a strike in its lower rim. Authors created a computer numeric model of the orbit with specified features—thickness and resilience modulus. During simulation an evenly spread 14400 N force was applied to the nodular points in the inferior rim (the maximal value not causing cracking of the outer rim, but only ruptures in the inferior wall. The observation was made from 1·10-3 to 1·10-2 second after a strike. Right after a strike dislocations of the inferior orbital wall toward the maxillary sinus were observed. Afterwards a retrograde wave of the dislocation of the inferior wall toward the orbit was noticed. Overall dislocation amplitude reached about 6 mm. Based on a numeric model of the orbit submitted to a strike in the inferior wall an existence of a retrograde shock wave causing orbital emphysema has been found.
Numerical modeling of atmospheric washout processes
International Nuclear Information System (INIS)
Bayer, D.; Beheng, K.D.; Herbert, F.
1987-01-01
For the washout of particles from the atmosphere by clouds and rain one has to distinguish between processes which work in the first phase of cloud development, when condensation nuclei build up in saturated air (Nucleation Aerosol Scavenging, NAS) and those processes which work at the following cloud development. In the second case particles are taken off by cloud droplets or by falling rain drops via collision (Collision Aerosol Scavenging, CAS). The physics of both processes is described. For the CAS process a numerical model is presented. The report contains a documentation of the mathematical equations and the computer programs (FORTRAN). (KW) [de
NUMERICAL MODEL APPLICATION IN ROWING SIMULATOR DESIGN
Directory of Open Access Journals (Sweden)
Petr Chmátal
2016-04-01
Full Text Available The aim of the research was to carry out a hydraulic design of rowing/sculling and paddling simulator. Nowadays there are two main approaches in the simulator design. The first one includes a static water with no artificial movement and counts on specially cut oars to provide the same resistance in the water. The second approach, on the other hand uses pumps or similar devices to force the water to circulate but both of the designs share many problems. Such problems are affecting already built facilities and can be summarized as unrealistic feeling, unwanted turbulent flow and bad velocity profile. Therefore, the goal was to design a new rowing simulator that would provide nature-like conditions for the racers and provide an unmatched experience. In order to accomplish this challenge, it was decided to use in-depth numerical modeling to solve the hydraulic problems. The general measures for the design were taken in accordance with space availability of the simulator ́s housing. The entire research was coordinated with other stages of the construction using BIM. The detailed geometry was designed using a numerical model in Ansys Fluent and parametric auto-optimization tools which led to minimum negative hydraulic phenomena and decreased investment and operational costs due to the decreased hydraulic losses in the system.
Numerical modeling of materials under extreme conditions
Brown, Eric
2014-01-01
The book presents twelve state of the art contributions in the field of numerical modeling of materials subjected to large strain, high strain rates, large pressure and high stress triaxialities, organized into two sections. The first part is focused on high strain rate-high pressures such as those occurring in impact dynamics and shock compression related phenomena, dealing with material response identification, advanced modeling incorporating microstructure and damage, stress waves propagation in solids and structures response under impact. The latter part is focused on large strain-low strain rates applications such as those occurring in technological material processing, dealing with microstructure and texture evolution, material response at elevated temperatures, structural behavior under large strain and multi axial state of stress.
Partial Differential Equations Modeling and Numerical Simulation
Glowinski, Roland
2008-01-01
This book is dedicated to Olivier Pironneau. For more than 250 years partial differential equations have been clearly the most important tool available to mankind in order to understand a large variety of phenomena, natural at first and then those originating from human activity and technological development. Mechanics, physics and their engineering applications were the first to benefit from the impact of partial differential equations on modeling and design, but a little less than a century ago the Schrödinger equation was the key opening the door to the application of partial differential equations to quantum chemistry, for small atomic and molecular systems at first, but then for systems of fast growing complexity. Mathematical modeling methods based on partial differential equations form an important part of contemporary science and are widely used in engineering and scientific applications. In this book several experts in this field present their latest results and discuss trends in the numerical analy...
A delta-rule model of numerical and non-numerical order processing.
Verguts, Tom; Van Opstal, Filip
2014-06-01
Numerical and non-numerical order processing share empirical characteristics (distance effect and semantic congruity), but there are also important differences (in size effect and end effect). At the same time, models and theories of numerical and non-numerical order processing developed largely separately. Currently, we combine insights from 2 earlier models to integrate them in a common framework. We argue that the same learning principle underlies numerical and non-numerical orders, but that environmental features determine the empirical differences. Implications for current theories on order processing are pointed out. PsycINFO Database Record (c) 2014 APA, all rights reserved.
Adaptive Numerical Algorithms in Space Weather Modeling
Toth, Gabor; vanderHolst, Bart; Sokolov, Igor V.; DeZeeuw, Darren; Gombosi, Tamas I.; Fang, Fang; Manchester, Ward B.; Meng, Xing; Nakib, Dalal; Powell, Kenneth G.;
2010-01-01
Space weather describes the various processes in the Sun-Earth system that present danger to human health and technology. The goal of space weather forecasting is to provide an opportunity to mitigate these negative effects. Physics-based space weather modeling is characterized by disparate temporal and spatial scales as well as by different physics in different domains. A multi-physics system can be modeled by a software framework comprising of several components. Each component corresponds to a physics domain, and each component is represented by one or more numerical models. The publicly available Space Weather Modeling Framework (SWMF) can execute and couple together several components distributed over a parallel machine in a flexible and efficient manner. The framework also allows resolving disparate spatial and temporal scales with independent spatial and temporal discretizations in the various models. Several of the computationally most expensive domains of the framework are modeled by the Block-Adaptive Tree Solar wind Roe Upwind Scheme (BATS-R-US) code that can solve various forms of the magnetohydrodynamics (MHD) equations, including Hall, semi-relativistic, multi-species and multi-fluid MHD, anisotropic pressure, radiative transport and heat conduction. Modeling disparate scales within BATS-R-US is achieved by a block-adaptive mesh both in Cartesian and generalized coordinates. Most recently we have created a new core for BATS-R-US: the Block-Adaptive Tree Library (BATL) that provides a general toolkit for creating, load balancing and message passing in a 1, 2 or 3 dimensional block-adaptive grid. We describe the algorithms of BATL and demonstrate its efficiency and scaling properties for various problems. BATS-R-US uses several time-integration schemes to address multiple time-scales: explicit time stepping with fixed or local time steps, partially steady-state evolution, point-implicit, semi-implicit, explicit/implicit, and fully implicit numerical
Statistical mechanics rigorous results
Ruelle, David
1999-01-01
This classic book marks the beginning of an era of vigorous mathematical progress in equilibrium statistical mechanics. Its treatment of the infinite system limit has not been superseded, and the discussion of thermodynamic functions and states remains basic for more recent work. The conceptual foundation provided by the Rigorous Results remains invaluable for the study of the spectacular developments of statistical mechanics in the second half of the 20th century.
The basic approach to age-structured population dynamics models, methods and numerics
Iannelli, Mimmo
2017-01-01
This book provides an introduction to age-structured population modeling which emphasises the connection between mathematical theory and underlying biological assumptions. Through the rigorous development of the linear theory and the nonlinear theory alongside numerics, the authors explore classical equations that describe the dynamics of certain ecological systems. Modeling aspects are discussed to show how relevant problems in the fields of demography, ecology, and epidemiology can be formulated and treated within the theory. In particular, the book presents extensions of age-structured modelling to the spread of diseases and epidemics while also addressing the issue of regularity of solutions, the asymptotic behaviour of solutions, and numerical approximation. With sections on transmission models, non-autonomous models and global dynamics, this book fills a gap in the literature on theoretical population dynamics. The Basic Approach to Age-Structured Population Dynamics will appeal to graduate students an...
Numerical modelling of ion transport in flames
Han, Jie
2015-10-20
This paper presents a modelling framework to compute the diffusivity and mobility of ions in flames. The (n, 6, 4) interaction potential is adopted to model collisions between neutral and charged species. All required parameters in the potential are related to the polarizability of the species pair via semi-empirical formulas, which are derived using the most recently published data or best estimates. The resulting framework permits computation of the transport coefficients of any ion found in a hydrocarbon flame. The accuracy of the proposed method is evaluated by comparing its predictions with experimental data on the mobility of selected ions in single-component neutral gases. Based on this analysis, the value of a model constant available in the literature is modified in order to improve the model\\'s predictions. The newly determined ion transport coefficients are used as part of a previously developed numerical approach to compute the distribution of charged species in a freely propagating premixed lean CH4/O2 flame. Since a significant scatter of polarizability data exists in the literature, the effects of changes in polarizability on ion transport properties and the spatial distribution of ions in flames are explored. Our analysis shows that changes in polarizability propagate with decreasing effect from binary transport coefficients to species number densities. We conclude that the chosen polarizability value has a limited effect on the ion distribution in freely propagating flames. We expect that the modelling framework proposed here will benefit future efforts in modelling the effect of external voltages on flames. Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/13647830.2015.1090018. © 2015 Taylor & Francis.
Modeling and numerical simulations of the influenced Sznajd model
Karan, Farshad Salimi Naneh; Srinivasan, Aravinda Ramakrishnan; Chakraborty, Subhadeep
2017-08-01
This paper investigates the effects of independent nonconformists or influencers on the behavioral dynamic of a population of agents interacting with each other based on the Sznajd model. The system is modeled on a complete graph using the master equation. The acquired equation has been numerically solved. Accuracy of the mathematical model and its corresponding assumptions have been validated by numerical simulations. Regions of initial magnetization have been found from where the system converges to one of two unique steady-state PDFs, depending on the distribution of influencers. The scaling property and entropy of the stationary system in presence of varying level of influence have been presented and discussed.
Liu, Gang; Zhang, Jian; Bao, Jie
2016-01-01
Cost reduction on cellulase enzyme usage has been the central effort in the commercialization of fuel ethanol production from lignocellulose biomass. Therefore, establishing an accurate evaluation method on cellulase enzyme cost is crucially important to support the health development of the future biorefinery industry. Currently, the cellulase cost evaluation methods were complicated and various controversial or even conflict results were presented. To give a reliable evaluation on this important topic, a rigorous analysis based on the Aspen Plus flowsheet simulation in the commercial scale ethanol plant was proposed in this study. The minimum ethanol selling price (MESP) was used as the indicator to show the impacts of varying enzyme supply modes, enzyme prices, process parameters, as well as enzyme loading on the enzyme cost. The results reveal that the enzyme cost drives the cellulosic ethanol price below the minimum profit point when the enzyme is purchased from the current industrial enzyme market. An innovative production of cellulase enzyme such as on-site enzyme production should be explored and tested in the industrial scale to yield an economically sound enzyme supply for the future cellulosic ethanol production.
Mathematical models and numerical simulation in electromagnetism
Bermúdez, Alfredo; Salgado, Pilar
2014-01-01
The book represents a basic support for a master course in electromagnetism oriented to numerical simulation. The main goal of the book is that the reader knows the boundary-value problems of partial differential equations that should be solved in order to perform computer simulation of electromagnetic processes. Moreover it includes a part devoted to electric circuit theory based on ordinary differential equations. The book is mainly oriented to electric engineering applications, going from the general to the specific, namely, from the full Maxwell’s equations to the particular cases of electrostatics, direct current, magnetostatics and eddy currents models. Apart from standard exercises related to analytical calculus, the book includes some others oriented to real-life applications solved with MaxFEM free simulation software.
Numerical modeling capabilities to predict repository performance
International Nuclear Information System (INIS)
1979-09-01
This report presents a summary of current numerical modeling capabilities that are applicable to the design and performance evaluation of underground repositories for the storage of nuclear waste. The report includes codes that are available in-house, within Golder Associates and Lawrence Livermore Laboratories; as well as those that are generally available within the industry and universities. The first listing of programs are in-house codes in the subject areas of hydrology, solute transport, thermal and mechanical stress analysis, and structural geology. The second listing of programs are divided by subject into the following categories: site selection, structural geology, mine structural design, mine ventilation, hydrology, and mine design/construction/operation. These programs are not specifically designed for use in the design and evaluation of an underground repository for nuclear waste; but several or most of them may be so used
DeGeest, David Scott; Schmidt, Frank
2015-01-01
Our objective was to apply the rigorous test developed by Browne (1992) to determine whether the circumplex model fits Big Five personality data. This test has yet to be applied to personality data. Another objective was to determine whether blended items explained correlations among the Big Five traits. We used two working adult samples, the Eugene-Springfield Community Sample and the Professional Worker Career Experience Survey. Fit to the circumplex was tested via Browne's (1992) procedure. Circumplexes were graphed to identify items with loadings on multiple traits (blended items), and to determine whether removing these items changed five-factor model (FFM) trait intercorrelations. In both samples, the circumplex structure fit the FFM traits well. Each sample had items with dual-factor loadings (8 items in the first sample, 21 in the second). Removing blended items had little effect on construct-level intercorrelations among FFM traits. We conclude that rigorous tests show that the fit of personality data to the circumplex model is good. This finding means the circumplex model is competitive with the factor model in understanding the organization of personality traits. The circumplex structure also provides a theoretically and empirically sound rationale for evaluating intercorrelations among FFM traits. Even after eliminating blended items, FFM personality traits remained correlated.
Ocean wave prediction using numerical and neural network models
Digital Repository Service at National Institute of Oceanography (India)
Mandal, S.; Prabaharan, N.
This paper presents an overview of the development of the numerical wave prediction models and recently used neural networks for ocean wave hindcasting and forecasting. The numerical wave models express the physical concepts of the phenomena...
Numerical modeling of bubble dynamics in magmas
Huber, Christian; Su, Yanqing; Parmigiani, Andrea
2014-05-01
Understanding the complex non-linear physics that governs volcanic eruptions is contingent on our ability to characterize the dynamics of bubbles and its effect on the ascending magma. The exsolution and migration of bubbles has also a great impact on the heat and mass transport in and out of magma bodies stored at shallow depths in the crust. Multiphase systems like magmas are by definition heterogeneous at small scales. Although mixture theory or homogenization methods are convenient to represent multiphase systems as a homogeneous equivalent media, these approaches do not inform us on possible feedbacks at the pore-scale and can be significantly misleading. In this presentation, we discuss the development and application of bubble-scale multiphase flow modeling to address the following questions : How do bubbles impact heat and mass transport in magma chambers ? How efficient are chemical exchanges between the melt and bubbles during magma decompression? What is the role of hydrodynamic interactions on the deformation of bubbles while the magma is sheared? Addressing these questions requires powerful numerical methods that accurately model the balance between viscous, capillary and pressure stresses. We discuss how these bubble-scale models can provide important constraints on the dynamics of magmas stored at shallow depth or ascending to the surface during an eruption.
Numerical modeling of polar mesocyclones generation mechanisms
Sergeev, Dennis; Stepanenko, Victor
2013-04-01
parameters, lateral boundary conditions are varied in the typically observed range. The approach is fully nonlinear: we use a three-dimensional non-hydrostatic mesoscale model NH3D_MPI [1] coupled with one-dimensional water body model LAKE. A key method used in the present study is the analysis of eddy kinetic and available potential energy budgets. References 1. Mikushin, D.N., and Stepanenko, V.M., The implementation of regional atmospheric model numerical algorithms for CBEA-based clusters. Lecture Notes in Computer Science, Parallel Processing and Applied Mathematics, 2010, vol. 6067, p. 525-534. 2. Rasmussen, E., and Turner, J. (eds), Polar Lows: Mesoscale Weather Systems in the Polar Regions. Cambridge: Cambridge University Press, 2003, 612 pp. 3. Yanase, W., and Niino, H., Dependence of Polar Low Development on Baroclinicity and Physical Processes: An Idealized High-Resolution Experiment, J. Atmos. Sci., 2006, vol. 64, p. 3044-3067.
Numerical Modelling of Flow and Settling in Secondary Settling Tanks
DEFF Research Database (Denmark)
Dahl, Claus Poulsen
This thesis discusses the development of a numerical model for the simulation of secondary settling tanks. In the first part, the status on the development of numerical models for settling tanks and a discussion of the current design practice are presented. A study of the existing numerical models...... and design practice proved a demand for further development to include numerical models in the design of settling tanks, thus improving the future settling tanks....
Numerical modeling of the autumnal thermal bar
Tsydenov, Bair O.
2018-03-01
The autumnal riverine thermal bar of Kamloops Lake has been simulated using atmospheric data from December 1, 2015, to January 4, 2016. The nonhydrostatic 2.5D mathematical model developed takes into account the diurnal variability of the heat fluxes and wind on the lake surface. The average values for shortwave and longwave radiation and latent and sensible heat fluxes were 19.7 W/m2, - 95.9 W/m2, - 11.8 W/m2, and - 32.0 W/m2 respectively. Analysis of the wind regime data showed prevailing easterly winds and maximum speed of 11 m/s on the 8th and 19th days. Numerical experiments with different boundary conditions at the lake surface were conducted to evaluate effects of variable heat flux and wind stress. The results of modeling demonstrated that the variable heat flux affects the process of thermal bar evolution, especially during the lengthy night cooling. However, the wind had the greatest impact on the behavior of the autumnal thermal bar: The easterly winds contributed to an earlier appearance of the thermal bar, but the strong winds generating the intensive circulations (the velocity of the upper lake flow increased to 6 cm/s) may destroy the thermal bar front.
A numerical model of aerosol scavenging
International Nuclear Information System (INIS)
Bradley, M.M.; Molenkamp, C.R.
1991-10-01
Using a three-dimensional numerical cloud/smoke-plume model, we have simulated the burning of a large, mid-latitude city following a nuclear exchange. The model includes 18 dynamic and microphysical equations that predict the fire-driven airflow, cloud processes, and smoke-cloud interactions. In the simulation, the intense heating from the burning city produces a firestorm with updraft velocities exceeding 60 m/s. Within 15 minutes of ignition, the smoke plume penetrates the tropopause. The updraft triggers a cumulonimbus cloud that produces significant quantities of ice, snow, and hail. These solid hydrometeors, as well as cloud droplets and rain, interact with the smoke particles from the fire. At the end of the one-hour simulation, over 20% of the smoke is in slowly falling snowflakes. If the snow reaches the ground before the flakes completely sublimate (or melt and then evaporate), then only approximately 50% of the smoke will survive the scavenging processes and remain in the atmosphere to affect the global climate
Numerical Modelling of Seismic Slope Stability
Bourdeau, Céline; Havenith, Hans-Balder; Fleurisson, Jean-Alain; Grandjean, Gilles
Earthquake ground-motions recorded worldwide have shown that many morphological and geological structures (topography, sedimentary basin) are prone to amplify the seismic shaking (San Fernando, 1971 [Davis and West 1973] Irpinia, 1980 [Del Pezzo et al. 1983]). This phenomenon, called site effects, was again recently observed in El Salvador when, on the 13th of January 2001, the country was struck by a M = 7.6 earthquake. Indeed, while horizontal accelerations on a rock site at Berlin, 80 km from the epicentre, did not exceed 0.23 g, they reached 0.6 g at Armenia, 110 km from the epicentre. Armenia is located on a small hill underlaid by a few meters thick pyroclastic deposits. Both the local topography and the presence of surface layers are likely to have caused the observed amplification effects, which are supposed to have contributed to the triggering of some of the hundreds of landslides related to this seismic event (Murphy et al. 2002). In order to better characterize the way site effects may influence the triggering of landslides along slopes, 2D numerical elastic and elasto-plastic models were developed. Various geometrical, geological and seismic conditions were analysed and the dynamic behaviour of the slope under these con- ditions was studied in terms of creation and location of a sliding surface. Preliminary results suggest that the size of modelled slope failures is dependent on site effects.
Understanding Etna flank instability through numerical models
Apuani, Tiziana; Corazzato, Claudia; Merri, Andrea; Tibaldi, Alessandro
2013-02-01
As many active volcanoes, Mount Etna shows clear evidence of flank instability, and different mechanisms were suggested to explain this flank dynamics, based on the recorded deformation pattern and character. Shallow and deep deformations, mainly associated with both eruptive and seismic events, are concentrated along recognised fracture and fault systems, mobilising the eastern and south-eastern flank of the volcano. Several interacting causes were postulated to control the phenomenon, including gravity force, magma ascent along the feeding system, and a very complex local and/or regional tectonic activity. Nevertheless, the complexity of such dynamics is still an open subject of research and being the volcano flanks heavily urbanised, the comprehension of the gravitative dynamics is a major issue for public safety and civil protection. The present research explores the effects of the main geological features (in particular the role of the subetnean clays, interposed between the Apennine-Maghrebian flysch and the volcanic products) and the role of weakness zones, identified by fracture and fault systems, on the slope instability process. The effects of magma intrusions are also investigated. The problem is addressed by integrating field data, laboratory tests and numerical modelling. A bi- and tri-dimensional stress-strain analysis was performed by a finite difference numerical code (FLAC and FLAC3D), mainly aimed at evaluating the relationship among geological features, volcano-tectonic structures and magmatic activity in controlling the deformation processes. The analyses are well supported by dedicated structural-mechanical field surveys, which allowed to estimate the rock mass strength and deformability parameters. To take into account the uncertainties which inevitably occur in a so complicated model, many efforts were done in performing a sensitivity analysis along a WNW-ESE section crossing the volcano summit and the Valle del Bove depression. This was
Numerical modeling of atoll island hydrogeology.
Bailey, R T; Jenson, J W; Olsen, A E
2009-01-01
We implemented Ayers and Vachers' (1986) inclusive conceptual model for atoll island aquifers in a comprehensive numerical modeling study to evaluate the response of the fresh water lens to selected controlling climatic and geologic variables. Climatic factors include both constant and time-varying recharge rates, with particular attention paid to the effects of El Niño and the associated drought it brings to the western Pacific. Geologic factors include island width; hydraulic conductivity of the uppermost Holocene-age aquifer, which contains the fresh water lens; the depth to the contact with the underlying, and much more conductive, Pleistocene karst aquifer, which transmits tidal signals to the base of the lens; and the presence or absence of a semiconfining reef flat plate on the ocean side. Sensitivity analyses of steady-steady simulations show that lens thickness is most strongly sensitive to the depth to the Holocene-Pleistocene contact and to the hydraulic conductivity of the Holocene aquifer, respectively. Comparisons between modeling results and published observations of atoll island lens thicknesses suggest a hydraulic conductivity of approximately 50 m/d for leeward islands and approximately 400 m/d for windward islands. Results of transient simulations show that lens thickness fluctuations during average seasonal conditions and El Niño events are quite sensitive to island width, recharge rate, and hydraulic conductivity of the Holocene aquifer. In general, the depletion of the lens during drought conditions is most drastic for small, windward islands. Simulation results suggest that recovery from a 6-month drought requires about 1.5 years.
Large scale experiments as a tool for numerical model development
DEFF Research Database (Denmark)
Kirkegaard, Jens; Hansen, Erik Asp; Fuchs, Jesper
2003-01-01
Experimental modelling is an important tool for study of hydrodynamic phenomena. The applicability of experiments can be expanded by the use of numerical models and experiments are important for documentation of the validity of numerical tools. In other cases numerical tools can be applied...
Numerical modelling of new rockfall interception nets
von Boetticher, Albrecht; Volkwein, Axel; Wendeler, Corinna
2010-05-01
The design and certification of effective rockfall protection barriers is mainly achieved through 1:1 prototype testing. In order to reduce development costs of a prototype it is recommended that pre-studies using numerical simulations are performed. A large component to modelling rockfall protection systems is the numerical simulation of the nets. To date there exist several approaches to model the different mesh types such as ring nets or diagonal meshes (Nicot 1999, Cazzani et al. 2002, Volkwein 2004). However, the consideration of chain link meshes has not yet been realised. Chain link meshes are normally found as standard fence structures. However, they also exist in setups using high-strength steel and wire bundles. These variants show an enormous capacity to retain loads e.g. rockfalls, and at the same time are very efficient due to their low demand of steel material. The increasing application of chain link mesh in barrier systems requires an accurate model is available to complete prototype studies. A new approach now aims to perform a Finite Element simulation of such chain link meshes. The main challenge herein is to achieve the net deformation behaviour that is observed in field tests also in the simulation. A simulation using simple truss elements would not work since it neglects the out-of-plane-height of the mesh construction providing important reserves for local and global high deformations. Thus addressing this, a specially developed Discrete Element is able to reconstruct the mechanical behaviour of the single chain wire (bundles). As input parameters it utilises typical properties such as longitudinal and transversal mesh widths, and break loads resulting from in-plane-tension tests and steel strength. The single chain elements then can be combined to a complete mesh (e.g. 130 x 65 mm, 3 - 4 mm wire with a strength of 1770 N-mm2). Combining these elements with a supporting structure consisting of posts, ropes and energy absorbers, enables the
Numerical models for high beta magnetohydrodynamic flow
International Nuclear Information System (INIS)
Brackbill, J.U.
1987-01-01
The fundamentals of numerical magnetohydrodynamics for highly conducting, high-beta plasmas are outlined. The discussions emphasize the physical properties of the flow, and how elementary concepts in numerical analysis can be applied to the construction of finite difference approximations that capture these features. The linear and nonlinear stability of explicit and implicit differencing in time is examined, the origin and effect of numerical diffusion in the calculation of convective transport is described, and a technique for maintaining solenoidality in the magnetic field is developed. Many of the points are illustrated by numerical examples. The techniques described are applicable to the time-dependent, high-beta flows normally encountered in magnetically confined plasmas, plasma switches, and space and astrophysical plasmas. 40 refs
Numerical modelling of nearshore wave transformation
Digital Repository Service at National Institute of Oceanography (India)
Chandramohan, P.; Nayak, B.U.; SanilKumar, V.
A software has been developed for numerical refraction study based on finite amplitude wave theories. Wave attenuation due to shoaling, bottom friction, bottom percolation and viscous dissipation has also been incorporated. The software...
Numerical modelling of multicomponent LNAPL dissolution kinetics ...
Indian Academy of Sciences (India)
subsequent removal of free phase liquid, still the organic compounds are present .... Since the flow through porous media is mainly restricted to the pore space ..... initial and boundary conditions for the numerical scheme are given in table 2.
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....
A numerical 4D Collision Risk Model
Schmitt, Pal; Culloch, Ross; Lieber, Lilian; Kregting, Louise
2017-04-01
With the growing number of marine renewable energy (MRE) devices being installed across the world, some concern has been raised about the possibility of harming mobile, marine fauna by collision. Although physical contact between a MRE device and an organism has not been reported to date, these novel sub-sea structures pose a challenge for accurately estimating collision risks as part of environmental impact assessments. Even if the animal motion is simplified to linear translation, ignoring likely evasive behaviour, the mathematical problem of establishing an impact probability is not trivial. We present a numerical algorithm to obtain such probability distributions using transient, four-dimensional simulations of a novel marine renewable device concept, Deep Green, Minesto's power plant and hereafter referred to as the 'kite' that flies in a figure-of-eight configuration. Simulations were carried out altering several configurations including kite depth, kite speed and kite trajectory while keeping the speed of the moving object constant. Since the kite assembly is defined as two parts in the model, a tether (attached to the seabed) and the kite, collision risk of each part is reported independently. By comparing the number of collisions with the number of collision-free simulations, a probability of impact for each simulated position in the cross- section of the area is considered. Results suggest that close to the bottom, where the tether amplitude is small, the path is always blocked and the impact probability is 100% as expected. However, higher up in the water column, the collision probability is twice as high in the mid line, where the tether passes twice per period than at the extremes of its trajectory. The collision probability distribution is much more complex in the upper end of the water column, where the kite and tether can simultaneously collide with the object. Results demonstrate the viability of such models, which can also incorporate empirical
Directory of Open Access Journals (Sweden)
M. Boumaza
2015-07-01
Full Text Available Transient convection heat transfer is of fundamental interest in many industrial and environmental situations, as well as in electronic devices and security of energy systems. Transient fluid flow problems are among the more difficult to analyze and yet are very often encountered in modern day technology. The main objective of this research project is to carry out a theoretical and numerical analysis of transient convective heat transfer in vertical flows, when the thermal field is due to different kinds of variation, in time and space of some boundary conditions, such as wall temperature or wall heat flux. This is achieved by the development of a mathematical model and its resolution by suitable numerical methods, as well as performing various sensitivity analyses. These objectives are achieved through a theoretical investigation of the effects of wall and fluid axial conduction, physical properties and heat capacity of the pipe wall on the transient downward mixed convection in a circular duct experiencing a sudden change in the applied heat flux on the outside surface of a central zone.
Backus, George E.
1999-01-01
The purpose of the grant was to study how prior information about the geomagnetic field can be used to interpret surface and satellite magnetic measurements, to generate quantitative descriptions of prior information that might be so used, and to use this prior information to obtain from satellite data a model of the core field with statistically justifiable error estimates. The need for prior information in geophysical inversion has long been recognized. Data sets are finite, and faithful descriptions of aspects of the earth almost always require infinite-dimensional model spaces. By themselves, the data can confine the correct earth model only to an infinite-dimensional subset of the model space. Earth properties other than direct functions of the observed data cannot be estimated from those data without prior information about the earth. Prior information is based on what the observer already knows before the data become available. Such information can be "hard" or "soft". Hard information is a belief that the real earth must lie in some known region of model space. For example, the total ohmic dissipation in the core is probably less that the total observed geothermal heat flow out of the earth's surface. (In principle, ohmic heat in the core can be recaptured to help drive the dynamo, but this effect is probably small.) "Soft" information is a probability distribution on the model space, a distribution that the observer accepts as a quantitative description of her/his beliefs about the earth. The probability distribution can be a subjective prior in the sense of Bayes or the objective result of a statistical study of previous data or relevant theories.
Püthe, Christoph; Manoj, Chandrasekharan; Kuvshinov, Alexey
2015-04-01
Electric fields induced in the conducting Earth during magnetic storms drive currents in power transmission grids, telecommunication lines or buried pipelines. These geomagnetically induced currents (GIC) can cause severe service disruptions. The prediction of GIC is thus of great importance for public and industry. A key step in the prediction of the hazard to technological systems during magnetic storms is the calculation of the geoelectric field. To address this issue for mid-latitude regions, we developed a method that involves 3-D modelling of induction processes in a heterogeneous Earth and the construction of a model of the magnetospheric source. The latter is described by low-degree spherical harmonics; its temporal evolution is derived from observatory magnetic data. Time series of the electric field can be computed for every location on Earth's surface. The actual electric field however is known to be perturbed by galvanic effects, arising from very local near-surface heterogeneities or topography, which cannot be included in the conductivity model. Galvanic effects are commonly accounted for with a real-valued time-independent distortion matrix, which linearly relates measured and computed electric fields. Using data of various magnetic storms that occurred between 2000 and 2003, we estimated distortion matrices for observatory sites onshore and on the ocean bottom. Strong correlations between modellings and measurements validate our method. The distortion matrix estimates prove to be reliable, as they are accurately reproduced for different magnetic storms. We further show that 3-D modelling is crucial for a correct separation of galvanic and inductive effects and a precise prediction of electric field time series during magnetic storms. Since the required computational resources are negligible, our approach is suitable for a real-time prediction of GIC. For this purpose, a reliable forecast of the source field, e.g. based on data from satellites
Masonry constructions mechanical models and numerical applications
Lucchesi, Massimiliano; Padovani, Cristina
2008-01-01
Numerical methods for the structural analysis of masonry constructions can be of great value in assessing the safety of artistically important masonry buildings and optimizing potential operations of maintenance and strengthening in terms of their cost-effectiveness, architectural impact and static effectiveness. This monograph firstly provides a detailed description of the constitutive equation of masonry-like materials, clearly setting out its most important features. It then goes on to provide a numerical procedure to solve the equilibrium problem of masonry solids. A large portion of the w
When Lagrangian stochastic models for turbulent dispersion are applied to complex flows, some type of ad hoc intervention is almost always necessary to eliminate unphysical behavior in the numerical solution. This paper discusses numerical considerations when solving the Langevin-based particle velo...
Some Experiences with Numerical Modelling of Overflows
DEFF Research Database (Denmark)
Larsen, Torben; Nielsen, L.; Jensen, B.
2007-01-01
across the edge of the overflow. To ensure critical flow across the edge, the upstream flow must be subcritical whereas the downstream flow is either supercritical or a free jet. Experimentally overflows are well studied. Based on laboratory experiments and Froude number scaling, numerous accurate...
Numerical time integration for air pollution models
J.G. Verwer (Jan); W. Hundsdorfer (Willem); J.G. Blom (Joke)
1998-01-01
textabstractDue to the large number of chemical species and the three space dimensions, off-the-shelf stiff ODE integrators are not feasible for the numerical time integration of stiff systems of advection-diffusion-reaction equations [ fracpar{c{t + nabla cdot left( vu{u c right) = nabla cdot left(
Dolev, Danny; Függer, Matthias; Posch, Markus; Schmid, Ulrich; Steininger, Andreas; Lenzen, Christoph
2014-01-01
We present the first implementation of a distributed clock generation scheme for Systems-on-Chip that recovers from an unbounded number of arbitrary transient faults despite a large number of arbitrary permanent faults. We devise self-stabilizing hardware building blocks and a hybrid synchronous/asynchronous state machine enabling metastability-free transitions of the algorithm's states. We provide a comprehensive modeling approach that permits to prove, given correctness of the constructed low-level building blocks, the high-level properties of the synchronization algorithm (which have been established in a more abstract model). We believe this approach to be of interest in its own right, since this is the first technique permitting to mathematically verify, at manageable complexity, high-level properties of a fault-prone system in terms of its very basic components. We evaluate a prototype implementation, which has been designed in VHDL, using the Petrify tool in conjunction with some extensions, and synthesized for an Altera Cyclone FPGA. PMID:26516290
Dolev, Danny; Függer, Matthias; Posch, Markus; Schmid, Ulrich; Steininger, Andreas; Lenzen, Christoph
2014-06-01
We present the first implementation of a distributed clock generation scheme for Systems-on-Chip that recovers from an unbounded number of arbitrary transient faults despite a large number of arbitrary permanent faults. We devise self-stabilizing hardware building blocks and a hybrid synchronous/asynchronous state machine enabling metastability-free transitions of the algorithm's states. We provide a comprehensive modeling approach that permits to prove, given correctness of the constructed low-level building blocks, the high-level properties of the synchronization algorithm (which have been established in a more abstract model). We believe this approach to be of interest in its own right, since this is the first technique permitting to mathematically verify, at manageable complexity, high-level properties of a fault-prone system in terms of its very basic components. We evaluate a prototype implementation, which has been designed in VHDL, using the Petrify tool in conjunction with some extensions, and synthesized for an Altera Cyclone FPGA.
Numerical modeling and the physical basis of seismic discriminants
International Nuclear Information System (INIS)
Denny, M.D.
1993-01-01
Accurate seismic event discrimination is critical to detection of nuclear explosions. Numerical modeling applied to seismic event discrimination can lead to increased reliability of proliferation detection. It is particularly applicable to error budgeting and to understanding explosion and earthquake phenomenologies. There also is a need for minimum requirements to validate the models used in numerical modeling
2-dimensional numerical modeling of active magnetic regeneration
DEFF Research Database (Denmark)
Nielsen, Kaspar Kirstein; Pryds, Nini; Smith, Anders
2009-01-01
Various aspects of numerical modeling of Active Magnetic Regeneration (AMR) are presented. Using a 2-dimensional numerical model for solving the unsteady heat transfer equations for the AMR system, a range of physical effects on both idealized and non-idealized AMR are investigated. The modeled...
Rigor or mortis: best practices for preclinical research in neuroscience.
Steward, Oswald; Balice-Gordon, Rita
2014-11-05
Numerous recent reports document a lack of reproducibility of preclinical studies, raising concerns about potential lack of rigor. Examples of lack of rigor have been extensively documented and proposals for practices to improve rigor are appearing. Here, we discuss some of the details and implications of previously proposed best practices and consider some new ones, focusing on preclinical studies relevant to human neurological and psychiatric disorders. Copyright © 2014 Elsevier Inc. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Chhabra, S.R.; Joachimiak, M.P.; Petzold, C.J.; Zane, G.M.; Price, M.N.; Gaucher, S.; Reveco, S.A.; Fok, V.; Johanson, A.R.; Batth, T.S.; Singer, M.; Chandonia, J.M.; Joyner, D.; Hazen, T.C.; Arkin, A.P.; Wall, J.D.; Singh, A.K.; Keasling, J.D.
2011-05-01
Protein–protein interactions offer an insight into cellular processes beyond what may be obtained by the quantitative functional genomics tools of proteomics and transcriptomics. The aforementioned tools have been extensively applied to study E. coli and other aerobes and more recently to study the stress response behavior of Desulfovibrio 5 vulgaris Hildenborough, a model anaerobe and sulfate reducer. In this paper we present the first attempt to identify protein-protein interactions in an obligate anaerobic bacterium. We used suicide vector-assisted chromosomal modification of 12 open reading frames encoded by this sulfate reducer to append an eight amino acid affinity tag to the carboxy-terminus of the chosen proteins. Three biological replicates of the 10 ‘pulled-down’ proteins were separated and analyzed using liquid chromatography-mass spectrometry. Replicate agreement ranged between 35% and 69%. An interaction network among 12 bait and 90 prey proteins was reconstructed based on 134 bait-prey interactions computationally identified to be of high confidence. We discuss the biological significance of several unique metabolic features of D. vulgaris revealed by this protein-protein interaction data 15 and protein modifications that were observed. These include the distinct role of the putative carbon monoxide-induced hydrogenase, unique electron transfer routes associated with different oxidoreductases, and the possible role of methylation in regulating sulfate reduction.
Directory of Open Access Journals (Sweden)
Swapnil R Chhabra
Full Text Available Protein-protein interactions offer an insight into cellular processes beyond what may be obtained by the quantitative functional genomics tools of proteomics and transcriptomics. The aforementioned tools have been extensively applied to study Escherichia coli and other aerobes and more recently to study the stress response behavior of Desulfovibrio vulgaris Hildenborough, a model obligate anaerobe and sulfate reducer and the subject of this study. Here we carried out affinity purification followed by mass spectrometry to reconstruct an interaction network among 12 chromosomally encoded bait and 90 prey proteins based on 134 bait-prey interactions identified to be of high confidence. Protein-protein interaction data are often plagued by the lack of adequate controls and replication analyses necessary to assess confidence in the results, including identification of potential false positives. We addressed these issues through the use of biological replication, exponentially modified protein abundance indices, results from an experimental negative control, and a statistical test to assign confidence to each putative interacting pair applicable to small interaction data studies. We discuss the biological significance of metabolic features of D. vulgaris revealed by these protein-protein interaction data and the observed protein modifications. These include the distinct role of the putative carbon monoxide-induced hydrogenase, unique electron transfer routes associated with different oxidoreductases, and the possible role of methylation in regulating sulfate reduction.
A methodology for the rigorous verification of plasma simulation codes
Riva, Fabio
2016-10-01
The methodology used to assess the reliability of numerical simulation codes constitutes the Verification and Validation (V&V) procedure. V&V is composed by two separate tasks: the verification, which is a mathematical issue targeted to assess that the physical model is correctly solved, and the validation, which determines the consistency of the code results, and therefore of the physical model, with experimental data. In the present talk we focus our attention on the verification, which in turn is composed by the code verification, targeted to assess that a physical model is correctly implemented in a simulation code, and the solution verification, that quantifies the numerical error affecting a simulation. Bridging the gap between plasma physics and other scientific domains, we introduced for the first time in our domain a rigorous methodology for the code verification, based on the method of manufactured solutions, as well as a solution verification based on the Richardson extrapolation. This methodology was applied to GBS, a three-dimensional fluid code based on a finite difference scheme, used to investigate the plasma turbulence in basic plasma physics experiments and in the tokamak scrape-off layer. Overcoming the difficulty of dealing with a numerical method intrinsically affected by statistical noise, we have now generalized the rigorous verification methodology to simulation codes based on the particle-in-cell algorithm, which are employed to solve Vlasov equation in the investigation of a number of plasma physics phenomena.
Conceptual and Numerical Models for UZ Flow and Transport
International Nuclear Information System (INIS)
Liu, H.
2000-01-01
The purpose of this Analysis/Model Report (AMR) is to document the conceptual and numerical models used for modeling of unsaturated zone (UZ) fluid (water and air) flow and solute transport processes. This is in accordance with ''AMR Development Plan for U0030 Conceptual and Numerical Models for Unsaturated Zone (UZ) Flow and Transport Processes, Rev 00''. The conceptual and numerical modeling approaches described in this AMR are used for models of UZ flow and transport in fractured, unsaturated rock under ambient and thermal conditions, which are documented in separate AMRs. This AMR supports the UZ Flow and Transport Process Model Report (PMR), the Near Field Environment PMR, and the following models: Calibrated Properties Model; UZ Flow Models and Submodels; Mountain-Scale Coupled Processes Model; Thermal-Hydrologic-Chemical (THC) Seepage Model; Drift Scale Test (DST) THC Model; Seepage Model for Performance Assessment (PA); and UZ Radionuclide Transport Models
Numerical Models of Sewage Dispersion and Statistica Bathing Water Standards
DEFF Research Database (Denmark)
Petersen, Ole; Larsen, Torben
1991-01-01
As bathing water standards usually are founded in statistical methods, the numerical models used in outfall design should reflect this. A statistical approach, where stochastic variations in source strength and bacterial disappearance is incorporated into a numerical dilution model is presented. ...
Mathematical modelling and numerical simulation of casting processes
DEFF Research Database (Denmark)
Hattel, Jesper Henri
1998-01-01
The control volume method applied to numerical modelling of castning. Analytical solutions based on the error function.Riemann-temperature. Modelling of release of latent heat with the enthalpy method....
A numerical model of heavy gas dispersion
International Nuclear Information System (INIS)
Bidokhtti, A.A.
1993-01-01
A simple mathematical model describing the motion of a dense gas released continuously into and environment is presented. The model correctly predicts the laboratory experiments which were carried out by Britter and Snyder (1987). It is an entrainment model better known as box model. In this model, the effects of temperature change and phase change are not considered and it is for a steady-state case. Further work is required for including these effects which are often associated with the mechanisms involved in accidental or natural release of heavy gases in the environment. The results of such a model will be extended to the practical situations which are and will be common to the nuclear industry at the Atomic Energy Organization of Iran. The applicability of such studies to these situations will be discussed
Numerical Model of High Strength Concrete
Wang, R. Z.; Wang, C. Y.; Lin, Y. L.
2018-03-01
The purpose of this paper is to present a three-dimensional constitutive model based on the concept of equivalent uniaxial strain. closed Menetrey-Willam (CMW) failure surfaces which combined with Menetrey-Willam meridian and the cap model are introduced in this paper. Saenz stress-strain model is applied and adjusted by the ultimate strength parameters from CMW failure surface to reflect the latest stress or strain condition. The high strength concrete (HSC) under tri-axial non-proportional loading is considered and the model in this paper performed a good prediction.
Koster, T.; Peelen, W.; Larbi, J.; Rooij, M. de; Polder, R.
2010-01-01
A mathematical model is being developed to describe a repair method in concrete, called cathodic protection (CP). The model is in principle also useful to describe electrodeposition in concrete, e.g. the process of re-precipitation of Ca(OH)_{2} invoked by an electrical current. In CP, the
Numerical Modelling of Wave Run-Up
DEFF Research Database (Denmark)
Ramirez, Jorge Robert Rodriguez; Frigaard, Peter; Andersen, Thomas Lykke
2011-01-01
Wave loads are important in problems related to offshore structure, such as wave run-up, slamming. The computation of such wave problems are carried out by CFD models. This paper presents one model, NS3, which solve 3D Navier-Stokes equations and use Volume of Fluid (VOF) method to treat the free...
Improving stability of regional numerical ocean models
Herzfeld, Mike
2009-02-01
An operational limited-area ocean modelling system was developed to supply forecasts of ocean state out to 3 days. This system is designed to allow non-specialist users to locate the model domain anywhere within the Australasian region with minimum user input. The model is required to produce a stable simulation every time it is invoked. This paper outlines the methodology used to ensure the model remains stable over the wide range of circumstances it might encounter. Central to the model configuration is an alternative approach to implementing open boundary conditions in a one-way nesting environment. Approximately 170 simulations were performed on limited areas in the Australasian region to assess the model stability; of these, 130 ran successfully with a static model parameterisation allowing a statistical estimate of the model’s approach toward instability to be determined. Based on this, when the model was deemed to be approaching instability a strategy of adaptive intervention in the form of constraint on velocity and elevation was invoked to maintain stability.
Numerical Modelling of Structures with Uncertainties
Directory of Open Access Journals (Sweden)
Kahsin Maciej
2017-04-01
Full Text Available The nature of environmental interactions, as well as large dimensions and complex structure of marine offshore objects, make designing, building and operation of these objects a great challenge. This is the reason why a vast majority of investment cases of this type include structural analysis, performed using scaled laboratory models and complemented by extended computer simulations. The present paper focuses on FEM modelling of the offshore wind turbine supporting structure. Then problem is studied using the modal analysis, sensitivity analysis, as well as the design of experiment (DOE and response surface model (RSM methods. The results of modal analysis based simulations were used for assessing the quality of the FEM model against the data measured during the experimental modal analysis of the scaled laboratory model for different support conditions. The sensitivity analysis, in turn, has provided opportunities for assessing the effect of individual FEM model parameters on the dynamic response of the examined supporting structure. The DOE and RSM methods allowed to determine the effect of model parameter changes on the supporting structure response.
Paleoclimate validation of a numerical climate model
International Nuclear Information System (INIS)
Schelling, F.J.; Church, H.W.; Zak, B.D.; Thompson, S.L.
1994-01-01
An analysis planned to validate regional climate model results for a past climate state at Yucca Mountain, Nevada, against paleoclimate evidence for the period is described. This analysis, which will use the GENESIS model of global climate nested with the RegCM2 regional climate model, is part of a larger study for DOE's Yucca Mountain Site Characterization Project that is evaluating the impacts of long term future climate change on performance of the potential high level nuclear waste repository at Yucca Mountain. The planned analysis and anticipated results are presented
Amorphous track models: a numerical comparison study
DEFF Research Database (Denmark)
Greilich, Steffen; Grzanka, Leszek; Hahn, Ute
in carbon ion treatment at the particle facility HIT in Heidelberg. Apparent differences between the LEM and the Katz model are the way how interactions of individual particle tracks and how extended targets are handled. Complex scenarios, however, can mask the actual effect of these differences. Here, we......Amorphous track models such as Katz' Ion-Gamma-Kill (IGK) approach [1, 2] or the Local Effect Model (LEM) [3, 4] had reasonable success in predicting the response of solid state dosimeters and radiobiological systems. LEM is currently applied in radiotherapy for biological dose optimization...
NUMERICAL SIMULATION AND MODELING OF UNSTEADY FLOW ...
African Journals Online (AJOL)
2014-06-30
Jun 30, 2014 ... objective of this study is to control the simulation of unsteady flows around structures. ... Aerospace, our results were in good agreement with experimental .... Two-Equation Eddy-Viscosity Turbulence Models for Engineering.
Computational numerical modelling of plasma focus
International Nuclear Information System (INIS)
Brollo, Fabricio
2005-01-01
Several models for calculation of the dynamics of Plasma Focus have been developed. All of them begin from the same physic principle: the current sheet run down the anode length, ionizing and collecting the gas that finds in its way.This is known as snow-plow model.Concerning pinch's compression, a MHD model is proposed.The plasma is treated as a fluid , particularly as a high ionized gas.However, there are not many models that, taking into account thermal equilibrium inside the plasma, make approximated calculations of the maximum temperatures reached in the pinch.Besides, there are no models which use those temperatures to estimate the termofusion neutron yield for the Deuterium or Deuterium-Tritium gas filled cases.In the PLADEMA network (Dense Magnetized Plasmas) a code was developed with the objective of describe the plasma focus dynamics, in a conceptual engineering stage.The codes calculates the principal variables (currents, time to focus, etc) and estimates the neutron yield in Deuterium-filled plasma focus devices.It can be affirmed that the code's experimental validation, in its axial and radial stages, was very successfully. However, it was accepted that the compression stage should be formulated again, to find a solution for a large variation of a parameter related with velocity profiles for the particles trapped inside the pinch.The objectives of this work can be stated in the next way : - Check the compression's model hypothesis. Develop a new model .- Implement the new model in the code. Compare results against experimental data of Plasma Focus devices from all around the world [es
The influence of numerical models on determining the drag coefficient
Directory of Open Access Journals (Sweden)
Dobeš Josef
2014-03-01
Full Text Available The paper deals with numerical modelling of body aerodynamic drag coefficient in the transition from laminar to turbulent flow regimes, where the selection of a suitable numerical model is problematic. On the basic problem of flow around a simple body – sphere selected computational models are tested. The values obtained by numerical simulations of drag coefficients of each model are compared with the graph of dependency of the drag coefficient vs. Reynolds number for a sphere. Next the dependency of Strouhal number vs. Reynolds number is evaluated, where the vortex shedding frequency values for given speed are obtained numerically and experimentally and then the values are compared for each numerical model and experiment. The aim is to specify trends for the selection of appropriate numerical model for flow around bodies problem in which the precise description of the flow field around the obstacle is used to define the acoustic noise source. Numerical modelling is performed by finite volume method using CFD code.
Numerical modelling of laser rapid prototyping by fusion wire deposit
Arbaoui , Larbi; Masse , J.E.; Barrallier , Laurent; Mocellin , Katia
2010-01-01
International audience; A finite element model has been developed to simulate an innovative laser rapid prototyping process. Several numerical developments have been implemented in order to simulate the main steps of the rapid prototyping process: injection, heating, phase change and deposit. The numerical model also takes into account different phenomena: surface tension in the liquid state, asborptivity and plasma effects during materiallaser interaction. The threedimensional model is based...
Evaluation of wave runup predictions from numerical and parametric models
Stockdon, Hilary F.; Thompson, David M.; Plant, Nathaniel G.; Long, Joseph W.
2014-01-01
Wave runup during storms is a primary driver of coastal evolution, including shoreline and dune erosion and barrier island overwash. Runup and its components, setup and swash, can be predicted from a parameterized model that was developed by comparing runup observations to offshore wave height, wave period, and local beach slope. Because observations during extreme storms are often unavailable, a numerical model is used to simulate the storm-driven runup to compare to the parameterized model and then develop an approach to improve the accuracy of the parameterization. Numerically simulated and parameterized runup were compared to observations to evaluate model accuracies. The analysis demonstrated that setup was accurately predicted by both the parameterized model and numerical simulations. Infragravity swash heights were most accurately predicted by the parameterized model. The numerical model suffered from bias and gain errors that depended on whether a one-dimensional or two-dimensional spatial domain was used. Nonetheless, all of the predictions were significantly correlated to the observations, implying that the systematic errors can be corrected. The numerical simulations did not resolve the incident-band swash motions, as expected, and the parameterized model performed best at predicting incident-band swash heights. An assimilated prediction using a weighted average of the parameterized model and the numerical simulations resulted in a reduction in prediction error variance. Finally, the numerical simulations were extended to include storm conditions that have not been previously observed. These results indicated that the parameterized predictions of setup may need modification for extreme conditions; numerical simulations can be used to extend the validity of the parameterized predictions of infragravity swash; and numerical simulations systematically underpredict incident swash, which is relatively unimportant under extreme conditions.
Numerical Modeling of Ophthalmic Response to Space
Nelson, E. S.; Myers, J. G.; Mulugeta, L.; Vera, J.; Raykin, J.; Feola, A.; Gleason, R.; Samuels, B.; Ethier, C. R.
2015-01-01
To investigate ophthalmic changes in spaceflight, we would like to predict the impact of blood dysregulation and elevated intracranial pressure (ICP) on Intraocular Pressure (IOP). Unlike other physiological systems, there are very few lumped parameter models of the eye. The eye model described here is novel in its inclusion of the human choroid and retrobulbar subarachnoid space (rSAS), which are key elements in investigating the impact of increased ICP and ocular blood volume. Some ingenuity was required in modeling the blood and rSAS compartments due to the lack of quantitative data on essential hydrodynamic quantities, such as net choroidal volume and blood flowrate, inlet and exit pressures, and material properties, such as compliances between compartments.
Piecewise Polynomial Aggregation as Preprocessing for Data Numerical Modeling
Dobronets, B. S.; Popova, O. A.
2018-05-01
Data aggregation issues for numerical modeling are reviewed in the present study. The authors discuss data aggregation procedures as preprocessing for subsequent numerical modeling. To calculate the data aggregation, the authors propose using numerical probabilistic analysis (NPA). An important feature of this study is how the authors represent the aggregated data. The study shows that the offered approach to data aggregation can be interpreted as the frequency distribution of a variable. To study its properties, the density function is used. For this purpose, the authors propose using the piecewise polynomial models. A suitable example of such approach is the spline. The authors show that their approach to data aggregation allows reducing the level of data uncertainty and significantly increasing the efficiency of numerical calculations. To demonstrate the degree of the correspondence of the proposed methods to reality, the authors developed a theoretical framework and considered numerical examples devoted to time series aggregation.
Numerical model updating technique for structures using firefly algorithm
Sai Kubair, K.; Mohan, S. C.
2018-03-01
Numerical model updating is a technique used for updating the existing experimental models for any structures related to civil, mechanical, automobiles, marine, aerospace engineering, etc. The basic concept behind this technique is updating the numerical models to closely match with experimental data obtained from real or prototype test structures. The present work involves the development of numerical model using MATLAB as a computational tool and with mathematical equations that define the experimental model. Firefly algorithm is used as an optimization tool in this study. In this updating process a response parameter of the structure has to be chosen, which helps to correlate the numerical model developed with the experimental results obtained. The variables for the updating can be either material or geometrical properties of the model or both. In this study, to verify the proposed technique, a cantilever beam is analyzed for its tip deflection and a space frame has been analyzed for its natural frequencies. Both the models are updated with their respective response values obtained from experimental results. The numerical results after updating show that there is a close relationship that can be brought between the experimental and the numerical models.
Numerical Modeling of Rotary Kiln Productivity Increase
Romero-Valle, M.A.; Pisaroni, M.; Van Puyvelde, D.; Lahaye, D.J.P.; Sadi, R.
2013-01-01
Rotary kilns are used in many industrial processes ranging from cement manufacturing to waste incineration. The operating conditions vary widely depending on the process. While there are many models available within the literature and industry, the wide range of operating conditions justifies
Numerical modeling of transformer inrush currents
Energy Technology Data Exchange (ETDEWEB)
Cardelli, E. [Department of Industrial Engineering, University of Perugia, I-06125 Perugia (Italy); Center for Electric and Magnetic Applied Research (Italy); Faba, A., E-mail: faba@unipg.it [Department of Industrial Engineering, University of Perugia, I-06125 Perugia (Italy); Center for Electric and Magnetic Applied Research (Italy)
2014-02-15
This paper presents an application of a vector hysteresis model to the prediction of the inrush current due the arbitrary initial excitation of a transformer after a fault. The approach proposed seems promising in order to predict the transient overshoot in current and the optimal time to close the circuit after the fault.
Numerical Modeling of Foam Drilling Hydraulics
Directory of Open Access Journals (Sweden)
Ozcan Baris
2007-12-01
Full Text Available The use of foam as a drilling fluid was developed to meet a special set of conditions under which other common drilling fluids had failed. Foam drilling is defined as the process of making boreholes by utilizing foam as the circulating fluid. When compared with conventional drilling, underbalanced or foam drilling has several advantages. These advantages include: avoidance of lost circulation problems, minimizing damage to pay zones, higher penetration rates and bit life. Foams are usually characterized by the quality, the ratio of the volume of gas, and the total foam volume. Obtaining dependable pressure profiles for aerated (gasified fluids and foam is more difficult than for single phase fluids, since in the former ones the drilling mud contains a gas phase that is entrained within the fluid system. The primary goal of this study is to expand the knowledge-base of the hydrodynamic phenomena that occur in a foam drilling operation. In order to gain a better understanding of foam drilling operations, a hydrodynamic model is developed and run at different operating conditions. For this purpose, the flow of foam through the drilling system is modeled by invoking the basic principles of continuum mechanics and thermodynamics. The model was designed to allow gas and liquid flow at desired volumetric flow rates through the drillstring and annulus. Parametric studies are conducted in order to identify the most influential variables in the hydrodynamic modeling of foam flow.
Numerical Modelling and Prediction of Erosion Induced by Hydrodynamic Cavitation
Peters, A.; Lantermann, U.; el Moctar, O.
2015-12-01
The present work aims to predict cavitation erosion using a numerical flow solver together with a new developed erosion model. The erosion model is based on the hypothesis that collapses of single cavitation bubbles near solid boundaries form high velocity microjets, which cause sonic impacts with high pressure amplitudes damaging the surface. The erosion model uses information from a numerical Euler-Euler flow simulation to predict erosion sensitive areas and assess the erosion aggressiveness of the flow. The obtained numerical results were compared to experimental results from tests of an axisymmetric nozzle.
Some Numerical Aspects on Crowd Motion - The Hughes Model
Gomes, Diogo A.
2016-01-06
Here, we study a crowd model proposed by R. Hughes in [5] and we describe a numerical approach to solve it. This model comprises a Fokker-Planck equation coupled with an Eikonal equation with Dirichlet or Neumann data. First, we establish a priori estimates for the solution. Second, we study radial solutions and identify a shock formation mechanism. Third, we illustrate the existence of congestion, the breakdown of the model, and the trend to the equilibrium. Finally, we propose a new numerical method and consider two numerical examples.
Numerical Validation of Chemical Compositional Model for Wettability Alteration Processes
Bekbauov, Bakhbergen; Berdyshev, Abdumauvlen; Baishemirov, Zharasbek; Bau, Domenico
2017-12-01
Chemical compositional simulation of enhanced oil recovery and surfactant enhanced aquifer remediation processes is a complex task that involves solving dozens of equations for all grid blocks representing a reservoir. In the present work, we perform a numerical validation of the newly developed mathematical formulation which satisfies the conservation laws of mass and energy and allows applying a sequential solution approach to solve the governing equations separately and implicitly. Through its application to the numerical experiment using a wettability alteration model and comparisons with existing chemical compositional model's numerical results, the new model has proven to be practical, reliable and stable.
Numerical Modelling and Measurement in a Test Secondary Settling Tank
DEFF Research Database (Denmark)
Dahl, C.; Larsen, Torben; Petersen, O.
1994-01-01
sludge. Phenomena as free and hindered settling and the Bingham plastic characteristic of activated sludge suspensions are included in the numerical model. Further characterisation and test tank experiments are described. The characterisation experiments were designed to measure calibration parameters...... for model description of settling and density differences. In the test tank experiments, flow velocities and suspended sludge concentrations were measured with different tank inlet geomotry and hydraulic and sludge loads. The test tank experiments provided results for the calibration of the numerical model......A numerical model and measurements of flow and settling in activated sludge suspension is presented. The numerical model is an attempt to describe the complex and interrelated hydraulic and sedimentation phenomena by describing the turbulent flow field and the transport/dispersion of suspended...
NUMERICAL MODELLING OF CHICKEN-FOOT FOUNDATION
Directory of Open Access Journals (Sweden)
Vipman Tandjiria
1999-01-01
Full Text Available This paper presents an analysis of the chicken-foot foundation using the finite element method. The foundation is considered as a reinforced concrete slab resting on a number of reinforced concrete pipes filled with and surrounded by in-situ soil. The soil and the pipes were modelled by isoparametric solid elements while the slab was modelled by isoparametric thick-plate elements. The study was intended to illustrate the basic mechanism of the chicken-foot foundation. Three cases have been considered for the parametric studies. The parameters investigated are thickness of slab, length of pipes and spacing between pipes. It is shown that such a foundation improves the behaviour of the raft foundation. It is also found that all the parameters used in the parametric studies influence the behaviour of the chicken-foot foundation.
Analytical and numerical modeling for flexible pipes
Wang, Wei; Chen, Geng
2011-12-01
The unbonded flexible pipe of eight layers, in which all the layers except the carcass layer are assumed to have isotropic properties, has been analyzed. Specifically, the carcass layer shows the orthotropic characteristics. The effective elastic moduli of the carcass layer have been developed in terms of the influence of deformation to stiffness. With consideration of the effective elastic moduli, the structure can be properly analyzed. Also the relative movements of tendons and relative displacements of wires in helical armour layer have been investigated. A three-dimensional nonlinear finite element model has been presented to predict the response of flexible pipes under axial force and torque. Further, the friction and contact of interlayer have been considered. Comparison between the finite element model and experimental results obtained in literature has been given and discussed, which might provide practical and technical support for the application of unbonded flexible pipes.
Numerical modeling of a vaporizing multicomponent droplet
Megaridis, C. M.; Sirignano, W. A.
The fundamental processes governing the energy, mass, and momentum exchange between the liquid and gas phases of vaporizing, multicomponent liquid droplets have been investigated. The axisymmetric configuration under consideration consists of an isolated multicomponent droplet vaporizing in a convective environment. The model considers different volatilities of the liquid components, variable liquid properties due to variation of the species concentrations, and non-Fickian multicomponent gaseous diffusion. The bicomponent droplet model was employed to examine the commonly used assumptions of unity Lewis number in the liquid phase and Fickian gaseous diffusion. It is found that the droplet drag coefficients, the vaporization rates, and the related transfer numbers are not influenced by the above assumptions in a significant way.
REPFLO model evaluation, physical and numerical consistency
International Nuclear Information System (INIS)
Wilson, R.N.; Holland, D.H.
1978-11-01
This report contains a description of some suggested changes and an evaluation of the REPFLO computer code, which models ground-water flow and nuclear-waste migration in and about a nuclear-waste repository. The discussion contained in the main body of the report is supplemented by a flow chart, presented in the Appendix of this report. The suggested changes are of four kinds: (1) technical changes to make the code compatible with a wider variety of digital computer systems; (2) changes to fill gaps in the computer code, due to missing proprietary subroutines; (3) changes to (a) correct programming errors, (b) correct logical flaws, and (c) remove unnecessary complexity; and (4) changes in the computer code logical structure to make REPFLO a more viable model from the physical point of view
Numerical modeling of the debris flows runout
Directory of Open Access Journals (Sweden)
Federico Francesco
2017-01-01
Full Text Available Rapid debris flows are identified among the most dangerous of all landslides. Due to their destructive potential, the runout length has to be predicted to define the hazardous areas and design safeguarding measures. To this purpose, a continuum model to predict the debris flows mobility is developed. It is based on the well known depth-integrated avalanche model proposed by Savage and Hutter (S&H model to simulate the dry granular materials flows. Conservation of mass and momentum equations, describing the evolving geometry and the depth averaged velocity distribution, are re-written taking into account the effects of the interstitial pressures and the possible variation of mass along the motion due to erosion/deposition processes. Furthermore, the mechanical behaviour of the debris flow is described by a recently developed rheological law, which allows to take into account the dissipative effects of the grain inelastic collisions and friction, simultaneously acting within a ‘shear layer’, typically at the base of the debris flows. The governing PDEs are solved by applying the finite difference method. The analysis of a documented case is finally carried out.
Wallis, Ilka; Prommer, Henning; Simmons, Craig T; Post, Vincent; Stuyfzand, Pieter J
2010-07-01
Managed Aquifer Recharge (MAR) is promoted as an attractive technique to meet growing water demands. An impediment to MAR applications, where oxygenated water is recharged into anoxic aquifers, is the potential mobilization of trace metals (e.g., arsenic). While conceptual models for arsenic transport under such circumstances exist, they are generally not rigorously evaluated through numerical modeling, especially at field-scale. In this work, geochemical data from an injection experiment in The Netherlands, where the introduction of oxygenated water into an anoxic aquifer mobilized arsenic, was used to develop and evaluate conceptual and numerical models of arsenic release and attenuation under field-scale conditions. Initially, a groundwater flow and nonreactive transport model was developed. Subsequent reactive transport simulations focused on the description of the temporal and spatial evolution of the redox zonation. The calibrated model was then used to study and quantify the transport of arsenic. In the model that best reproduced field observations, the fate of arsenic was simulated by (i) release via codissolution of arsenopyrite, stoichiometrically linked to pyrite oxidation, (ii) kinetically controlled oxidation of dissolved As(III) to As(V), and (iii) As adsorption via surface complexation on neo-precipitated iron oxides.
Complexities in coastal sediment transport studies by numerical modelling
Digital Repository Service at National Institute of Oceanography (India)
Ilangovan, D.; ManiMurali, R.
equations arrived based on scientific principles as all natural phenomena are governed by certain rules which can be explained by scientific principles. Efficiency of numerical modeling greatly depends on quality of input parameters. When input parameters...
Summary of Numerical Modeling for Underground Nuclear Test Monitoring Symposium
International Nuclear Information System (INIS)
Taylor, S.R.; Kamm, J.R.
1993-01-01
This document contains the Proceedings of the Numerical Modeling for Underground Nuclear Test Monitoring Symposium held in Durango, Colorado on March 23-25, 1993. The symposium was sponsored by the Office of Arms Control and Nonproliferation of the United States Department of Energy and hosted by the Source Region Program of Los Alamos National Laboratory. The purpose of the meeting was to discuss state-of-the-art advances in numerical simulations of nuclear explosion phenomenology for the purpose of test ban monitoring. Another goal of the symposium was to promote discussion between seismologists and explosion source-code calculators. Presentation topics include the following: numerical model fits to data, measurement and characterization of material response models, applications of modeling to monitoring problems, explosion source phenomenology, numerical simulations and seismic sources
Guadalupe River, California, Sedimentation Study. Numerical Model Investigation
National Research Council Canada - National Science Library
Copeland, Ronald
2002-01-01
A numerical model study was conducted to evaluate the potential impact that the Guadalupe River flood-control project would have on channel stability in terms of channel aggradation and degradation...
Numerical Modeling of Subglacial Sediment Deformation
DEFF Research Database (Denmark)
Damsgaard, Anders
2015-01-01
may cause mass loss in the near future to exceed current best estimates. Ice flow in larger ice sheets focuses in fast-moving streams due to mechanical non-linearity of ice. These ice streams often move at velocities several magnitudes larger than surrounding ice and consequentially constitute...... glaciers move by deforming their sedimentary beds. Several modern ice streams, in particular, move as plug flows due to basal sediment deformation. An intense and long-winded discussion about the appropriate description for subglacial sediment mechanics followed this discovery, with good reason...... 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...
Reservoir Models for Gas Hydrate Numerical Simulation
Boswell, R.
2016-12-01
Scientific and industrial drilling programs have now providing detailed information on gas hydrate systems that will increasingly be the subject of field experiments. The need to carefully plan these programs requires reliable prediction of reservoir response to hydrate dissociation. Currently, a major emphasis in gas hydrate modeling is the integration of thermodynamic/hydrologic phenomena with geomechanical response for both reservoir and bounding strata. However, also critical to the ultimate success of these efforts is the appropriate development of input geologic models, including several emerging issues, including (1) reservoir heterogeneity, (2) understanding of the initial petrophysical characteristics of the system (reservoirs and seals), the dynamic evolution of those characteristics during active dissociation, and the interdependency of petrophysical parameters and (3) the nature of reservoir boundaries. Heterogeneity is ubiquitous aspect of every natural reservoir, and appropriate characterization is vital. However, heterogeneity is not random. Vertical variation can be evaluated with core and well log data; however, core data often are challenged by incomplete recovery. Well logs also provide interpretation challenges, particularly where reservoirs are thinly-bedded due to limitation in vertical resolution. This imprecision will extend to any petrophysical measurements that are derived from evaluation of log data. Extrapolation of log data laterally is also complex, and should be supported by geologic mapping. Key petrophysical parameters include porosity, permeability and it many aspects, and water saturation. Field data collected to date suggest that the degree of hydrate saturation is strongly controlled by/dependant upon reservoir quality and that the ratio of free to bound water in the remaining pore space is likely also controlled by reservoir quality. Further, those parameters will also evolve during dissociation, and not necessary in a simple
Numerical solution of dynamic equilibrium models under Poisson uncertainty
DEFF Research Database (Denmark)
Posch, Olaf; Trimborn, Timo
2013-01-01
We propose a simple and powerful numerical algorithm to compute the transition process in continuous-time dynamic equilibrium models with rare events. In this paper we transform the dynamic system of stochastic differential equations into a system of functional differential equations of the retar...... solution to Lucas' endogenous growth model under Poisson uncertainty are used to compute the exact numerical error. We show how (potential) catastrophic events such as rare natural disasters substantially affect the economic decisions of households....
The Turbulent Interstellar Medium: Insights and Questions from Numerical Models
Mac Low, Mordecai-Mark; de Avillez, Miguel A.; Korpi, Maarit J.
2003-01-01
"The purpose of numerical models is not numbers but insight." (Hamming) In the spirit of this adage, and of Don Cox's approach to scientific speaking, we discuss the questions that the latest generation of numerical models of the interstellar medium raise, at least for us. The energy source for the interstellar turbulence is still under discussion. We review the argument for supernovae dominating in star forming regions. Magnetorotational instability has been suggested as a way of coupling di...
Numerical modeling in photonic crystals integrated technology: the COPERNICUS Project
DEFF Research Database (Denmark)
Malaguti, Stefania; Armaroli, Andrea; Bellanca, Gaetano
2011-01-01
Photonic crystals will play a fundamental role in the future of optical communications. The relevance of the numerical modeling for the success of this technology is assessed by using some examples concerning the experience of the COPERNICUS Project.......Photonic crystals will play a fundamental role in the future of optical communications. The relevance of the numerical modeling for the success of this technology is assessed by using some examples concerning the experience of the COPERNICUS Project....
Polynomial model inversion control: numerical tests and applications
Novara, Carlo
2015-01-01
A novel control design approach for general nonlinear systems is described in this paper. The approach is based on the identification of a polynomial model of the system to control and on the on-line inversion of this model. Extensive simulations are carried out to test the numerical efficiency of the approach. Numerical examples of applicative interest are presented, concerned with control of the Duffing oscillator, control of a robot manipulator and insulin regulation in a type 1 diabetic p...
Numerical modelling of concentrated leak erosion during Hole Erosion Tests
Mercier, F.; Bonelli, S.; Golay, F.; Anselmet, F.; Philippe, P.; Borghi, R.
2015-01-01
This study focuses on the numerical modelling of concentrated leak erosion of a cohesive soil by a turbulent flow in axisymmetrical geometry, with application to the Hole Erosion Test (HET). The numerical model is based on adaptive remeshing of the water/soil interface to ensure accurate description of the mechanical phenomena occurring near the soil/water interface. The erosion law governing the interface motion is based on two erosion parameters: the critical shear stress and the erosion co...
Soil remediation by heat injection: Experiments and numerical modelling
Energy Technology Data Exchange (ETDEWEB)
Betz, C.; Emmert, M.; Faerber, A. [Univ. of Stuttgart (Germany)] [and others
1995-03-01
In order to understand physical processes of thermally enhanced soil vapor extraction methods in porous media the isothermal, multiphase formulation for the numerical model MUFTE will be extended by a non-isothermal, multiphase-multicomponent formulation. In order to verify the numerical model, comparison with analytical solutions for well defined problems will be carried out. To identify relevant processes and their interactions, the results of the simulation will be compared with well controlled experiments with sophisticated measurement equipment in three different scales. The aim is to compare the different numerical solution techniques namely Finite Element versus Integral Finite Difference technique as implemented in MUFTE and TOUGH2 [9] respectively.
Numerical approaches to expansion process modeling
Directory of Open Access Journals (Sweden)
G. V. Alekseev
2017-01-01
Full Text Available Forage production is currently undergoing a period of intensive renovation and introduction of the most advanced technologies and equipment. More and more often such methods as barley toasting, grain extrusion, steaming and grain flattening, boiling bed explosion, infrared ray treatment of cereals and legumes, followed by flattening, and one-time or two-time granulation of the purified whole grain without humidification in matrix presses By grinding the granules. These methods require special apparatuses, machines, auxiliary equipment, created on the basis of different methods of compiled mathematical models. When roasting, simulating the heat fields arising in the working chamber, provide such conditions, the decomposition of a portion of the starch to monosaccharides, which makes the grain sweetish, but due to protein denaturation the digestibility of the protein and the availability of amino acids decrease somewhat. Grain is roasted mainly for young animals in order to teach them to eat food at an early age, stimulate the secretory activity of digestion, better development of the masticatory muscles. In addition, the high temperature is detrimental to bacterial contamination and various types of fungi, which largely avoids possible diseases of the gastrointestinal tract. This method has found wide application directly on the farms. Apply when used in feeding animals and legumes: peas, soy, lupine and lentils. These feeds are preliminarily ground, and then cooked or steamed for 1 hour for 30–40 minutes. In the feed mill. Such processing of feeds allows inactivating the anti-nutrients in them, which reduce the effectiveness of their use. After processing, legumes are used as protein supplements in an amount of 25–30% of the total nutritional value of the diet. But it is recommended to cook and steal a grain of good quality. A poor-quality grain that has been stored for a long time and damaged by pathogenic micro flora is subject to
A simple numerical model of a geometrically nonlinear Timoshenko beam
Keijdener, C.; Metrikine, A.
2015-01-01
In the original problem for which this model was developed, onedimensional flexible objects interact through a non-linear contact model. Due to the non-linear nature of the contact model, a numerical time-domain approach was adopted. One of the goals was to see if the coupling between axial and
A modular approach to numerical human body modeling
Forbes, P.A.; Griotto, G.; Rooij, L. van
2007-01-01
The choice of a human body model for a simulated automotive impact scenario must take into account both accurate model response and computational efficiency as key factors. This study presents a "modular numerical human body modeling" approach which allows the creation of a customized human body
Numerical simulations of a reduced model for blood coagulation
Pavlova, Jevgenija; Fasano, Antonio; Sequeira, Adélia
2016-04-01
In this work, the three-dimensional numerical resolution of a complex mathematical model for the blood coagulation process is presented. The model was illustrated in Fasano et al. (Clin Hemorheol Microcirc 51:1-14, 2012), Pavlova et al. (Theor Biol 380:367-379, 2015). It incorporates the action of the biochemical and cellular components of blood as well as the effects of the flow. The model is characterized by a reduction in the biochemical network and considers the impact of the blood slip at the vessel wall. Numerical results showing the capacity of the model to predict different perturbations in the hemostatic system are discussed.
Putrefactive rigor: apparent rigor mortis due to gas distension.
Gill, James R; Landi, Kristen
2011-09-01
Artifacts due to decomposition may cause confusion for the initial death investigator, leading to an incorrect suspicion of foul play. Putrefaction is a microorganism-driven process that results in foul odor, skin discoloration, purge, and bloating. Various decompositional gases including methane, hydrogen sulfide, carbon dioxide, and hydrogen will cause the body to bloat. We describe 3 instances of putrefactive gas distension (bloating) that produced the appearance of inappropriate rigor, so-called putrefactive rigor. These gases may distend the body to an extent that the extremities extend and lose contact with their underlying support surface. The medicolegal investigator must recognize that this is not true rigor mortis and the body was not necessarily moved after death for this gravity-defying position to occur.
Numerical Modeling and Mechanical Analysis of Flexible Risers
Directory of Open Access Journals (Sweden)
J. Y. Li
2015-01-01
Full Text Available ABAQUS is used to create a detailed finite element model for a 10-layer unbonded flexible riser to simulate the riser’s mechanical behavior under three load conditions: tension force and internal and external pressure. It presents a technique to create detailed finite element model and to analyze flexible risers. In FEM model, all layers are modeled separately with contact interfaces; interaction between steel trips in certain layers has been considered as well. FEM model considering contact interaction, geometric nonlinearity, and friction has been employed to accurately simulate the structural behavior of riser. The model includes the main features of the riser geometry with very little simplifying assumptions. The model was solved using a fully explicit time-integration scheme implemented in a parallel environment on an eight-processor cluster and 24 G memory computer. There is a very good agreement obtained from numerical and analytical comparisons, which validates the use of numerical model here. The results from the numerical simulation show that the numerical model takes into account various details of the riser. It has been shown that the detailed finite element model can be used to predict riser’s mechanics behavior under various load cases and bound conditions.
Models and numerical methods for time- and energy-dependent particle transport
Energy Technology Data Exchange (ETDEWEB)
Olbrant, Edgar
2012-04-13
Particles passing through a medium can be described by the Boltzmann transport equation. Therein, all physical interactions of particles with matter are given by cross sections. We compare different analytical models of cross sections for photons, electrons and protons to state-of-the-art databases. The large dimensionality of the transport equation and its integro-differential form make it analytically difficult and computationally costly to solve. In this work, we focus on the following approximative models to the linear Boltzmann equation: (i) the time-dependent simplified P{sub N} (SP{sub N}) equations, (ii) the M{sub 1} model derived from entropy-based closures and (iii) a new perturbed M{sub 1} model derived from a perturbative entropy closure. In particular, an asymptotic analysis for SP{sub N} equations is presented and confirmed by numerical computations in 2D. Moreover, we design an explicit Runge-Kutta discontinuous Galerkin (RKDG) method to the M{sub 1} model of radiative transfer in slab geometry and construct a scheme ensuring the realizability of the moment variables. Among other things, M{sub 1} numerical results are compared with an analytical solution in a Riemann problem and the Marshak wave problem is considered. Additionally, we rigorously derive a new hierarchy of kinetic moment models in the context of grey photon transport in one spatial dimension. For the perturbed M{sub 1} model, we present numerical results known as the two beam instability or the analytical benchmark due to Su and Olson and compare them to the standard M{sub 1} as well as transport solutions.
Numerical modelling of river morphodynamics: Latest developments and remaining challenges
Siviglia, Annunziato; Crosato, Alessandra
2016-07-01
Numerical morphodynamic models provide scientific frameworks for advancing our understanding of river systems. The research on involved topics is an important and socially relevant undertaking regarding our environment. Nowadays numerical models are used for different purposes, from answering questions about basic morphodynamic research to managing complex river engineering problems. Due to increasing computer power and the development of advanced numerical techniques, morphodynamic models are now more and more used to predict the bed patterns evolution to a broad spectrum of spatial and temporal scales. The development and the success of application of such models are based upon a wide range of disciplines from applied mathematics for the numerical solution of the equations to geomorphology for the physical interpretation of the results. In this light we organized this special issue (SI) soliciting multidisciplinary contributions which encompass any aspect needed for the development and applications of such models. Most of the papers in the SI stem from contributions to session HS9.5/GM7.11 on numerical modelling and experiments in river morphodynamics at the European Geosciences Union (EGU) General Assembly held in Vienna, April 27th to May 2nd 2014.
Nonspinning numerical relativity waveform surrogates: assessing the model
Field, Scott; Blackman, Jonathan; Galley, Chad; Scheel, Mark; Szilagyi, Bela; Tiglio, Manuel
2015-04-01
Recently, multi-modal gravitational waveform surrogate models have been built directly from data numerically generated by the Spectral Einstein Code (SpEC). I will describe ways in which the surrogate model error can be quantified. This task, in turn, requires (i) characterizing differences between waveforms computed by SpEC with those predicted by the surrogate model and (ii) estimating errors associated with the SpEC waveforms from which the surrogate is built. Both pieces can have numerous sources of numerical and systematic errors. We make an attempt to study the most dominant error sources and, ultimately, the surrogate model's fidelity. These investigations yield information about the surrogate model's uncertainty as a function of time (or frequency) and parameter, and could be useful in parameter estimation studies which seek to incorporate model error. Finally, I will conclude by comparing the numerical relativity surrogate model to other inspiral-merger-ringdown models. A companion talk will cover the building of multi-modal surrogate models.
Thermodynamic analysis and numerical modeling of supercritical injection
Banuti, Daniel
2015-01-01
Although liquid propellant rocket engines are operational and have been studied for decades, cryogenic injection at supercritical pressures is still considered essentially not understood. This thesis intends to approach this problem in three steps: by developing a numerical model for real gas thermodynamics, by extending the present thermodynamic view of supercritical injection, and finally by applying these methods to the analysis of injection. A new numerical real gas thermodynamics mode...
Numerical modeling of nitrogen oxide emission and experimental verification
Directory of Open Access Journals (Sweden)
Szecowka Lech
2003-12-01
Full Text Available The results of nitrogen reduction in combustion process with application of primary method are presented in paper. The reduction of NOx emission, by the recirculation of combustion gasses, staging of fuel and of air was investigated, and than the reduction of NOx emission by simultaneous usage of the mentioned above primary method with pulsatory disturbances.The investigations contain numerical modeling of NOx reduction and experimental verification of obtained numerical calculation results.
Numerical modelling of the HAB Energy Buoy: Stage 1
DEFF Research Database (Denmark)
Kurniawan, Adi
This report presents the results of the first stage of the project "Numerical modelling of the HAB Energy Buoy". The objectives of this stage are to develop a numerical model of the HAB Energy Buoy, a self-reacting wave energy device consisting of two heaving bodies, and to investigate a number...... and a summary of the main findings is presented. A numerical model of the HAB Energy Buoy has been developed in the frequency domain using two alternative formulations of the equations of motion. The model is capable of predicting the power capture, motion response, and power take-off loads of the device...... configuration are imposed to give a more realistic prediction of the power capture and help ensure a fair comparison. Recommendations with regard to the HAB design are finally suggested....
Numerical modelling of the jet nozzle enrichment process
International Nuclear Information System (INIS)
Vercelli, P.
1983-01-01
A numerical model was developed for the simulation of the isotopic enrichment produced by the jet nozzle process. The flow was considered stationary and under ideal gas conditions. The model calculates, for any position of the skimmer piece: (a) values of radial mass concentration profiles for each isotopic species and (b) values of elementary separation effect (Σ sub(A)) and uranium cut (theta). The comparison of the numerical results obtained with the experimental values given in the literature proves the validity of the present work as an initial step in the modelling of the process. (Author) [pt
Generalized Roe's numerical scheme for a two-fluid model
International Nuclear Information System (INIS)
Toumi, I.; Raymond, P.
1993-01-01
This paper is devoted to a mathematical and numerical study of a six equation two-fluid model. We will prove that the model is strictly hyperbolic due to the inclusion of the virtual mass force term in the phasic momentum equations. The two-fluid model is naturally written under a nonconservative form. To solve the nonlinear Riemann problem for this nonconservative hyperbolic system, a generalized Roe's approximate Riemann solver, is used, based on a linearization of the nonconservative terms. A Godunov type numerical scheme is built, using this approximate Riemann solver. 10 refs., 5 figs,
Numerical Modelling of Flow and Settling in Secondary Settling Tanks
Dahl, Claus Poulsen
1995-01-01
Denne afhandling omhandler udviklingen af en numerisk model til simulering af efterklaringstanke. lndledningsvis er beskrevet status for udviklingen inden for numeriske modeller for efterklaring og den nuværende designpraksis. Resultatet af denne statusbeskrivelse er et behov for videre udvikling for at indføre numeriske modeller i design af efterklaringstanke og hermed forbedre efterklaringstanke i fremtiden. This thesis discusses the development of a numerical model for the simulation of...
Numerical equilibrium analysis for structured consumer resource models
de Roos, A.M.; Diekmann, O.; Getto, P.; Kirkilionis, M.A.
2010-01-01
In this paper, we present methods for a numerical equilibrium and stability analysis for models of a size structured population competing for an unstructured re- source. We concentrate on cases where two model parameters are free, and thus existence boundaries for equilibria and stability boundaries
Numerical equilibrium analysis for structured consumer resource models
de Roos, A.M.; Diekmann, O.; Getto, P.; Kirkilionis, M.A.
2010-01-01
In this paper, we present methods for a numerical equilibrium and stability analysis for models of a size structured population competing for an unstructured resource. We concentrate on cases where two model parameters are free, and thus existence boundaries for equilibria and stability boundaries
Application of numerical modelling in SSM automotive brake calliper castings
CSIR Research Space (South Africa)
Jahajeeah, N
2006-01-01
Full Text Available Numerical modelling has successfully been used as an efficient tool to convert a gravity cast brake calliper to a thixocasting process. The thixo-modue of Procast has been used for the modelling process to obtain optimum processing parameters...
Some Numerical Aspects on Crowd Motion - The Hughes Model
Gomes, Diogo A.; Machado Velho, Roberto
2016-01-01
Here, we study a crowd model proposed by R. Hughes in [5] and we describe a numerical approach to solve it. This model comprises a Fokker-Planck equation coupled with an Eikonal equation with Dirichlet or Neumann data. First, we establish a priori
Numerical human model for impact and seating comfort
Hoof, J.F.A.M. van; Lange, R. de; Verver, M.M.
2003-01-01
This paper presents a detailed numerical model of the human body that can be used to evaluate both safety and comfort aspects of vehicle interiors. The model is based on a combination of rigid body and finite element techniques to provide an optimal combination of computational efficiency and
Numerical modelling of erosion and sedimentation around offshore pipelines
van Beek, 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
NUMERICAL PREDICTION MODELS FOR AIR POLLUTION BY MOTOR VEHICLE EMISSIONS
Directory of Open Access Journals (Sweden)
M. M. Biliaiev
2016-12-01
Full Text Available Purpose. Scientific work involves: 1 development of 3D numerical models that allow calculating the process of air pollution by motor vehicles emissions; 2 creation of models which would allow predicting the air pollution level in urban areas. Methodology. To solve the problem upon assessing the level of air pollution by motor vehicles emissions fundamental equations of aerodynamics and mass transfer are used. For the solution of differential equations of aerodynamics and mass transfer finite-difference methods are used. For the numerical integration of the equation for the velocity potential the method of conditional approximations is applied. The equation for the velocity potential written in differential form, splits into two equations, where at each step of splitting an unknown value of the velocity potential is determined by an explicit scheme of running computation, while the difference scheme is implicit one. For the numerical integration of the emissions dispersion equation in the atmosphere applies the implicit alternating-triangular difference scheme of splitting. Emissions from the road are modeled by a series of point sources of given intensity. Developed numerical models form is the basis of the created software package. Findings. 3D numerical models were developed; they belong to the class of «diagnostic models». These models take into account main physical factors that influence the process of dispersion of harmful substances in the atmosphere when emissions from vehicles in the city occur. Based on the constructed numerical models the computational experiment was conducted to assess the level of air pollution in the street. Originality. Authors have developed numerical models that allow to calculate the 3D aerodynamics of the wind flow in urban areas and the process of mass transfer emissions from the highway. Calculations to determine the area of contamination, which is formed near the buildings, located along the highway were
Concrete ensemble Kalman filters with rigorous catastrophic filter divergence.
Kelly, David; Majda, Andrew J; Tong, Xin T
2015-08-25
The ensemble Kalman filter and ensemble square root filters are data assimilation methods used to combine high-dimensional, nonlinear dynamical models with observed data. Ensemble methods are indispensable tools in science and engineering and have enjoyed great success in geophysical sciences, because they allow for computationally cheap low-ensemble-state approximation for extremely high-dimensional turbulent forecast models. From a theoretical perspective, the dynamical properties of these methods are poorly understood. One of the central mysteries is the numerical phenomenon known as catastrophic filter divergence, whereby ensemble-state estimates explode to machine infinity, despite the true state remaining in a bounded region. In this article we provide a breakthrough insight into the phenomenon, by introducing a simple and natural forecast model that transparently exhibits catastrophic filter divergence under all ensemble methods and a large set of initializations. For this model, catastrophic filter divergence is not an artifact of numerical instability, but rather a true dynamical property of the filter. The divergence is not only validated numerically but also proven rigorously. The model cleanly illustrates mechanisms that give rise to catastrophic divergence and confirms intuitive accounts of the phenomena given in past literature.
Mathematical Rigor in Introductory Physics
Vandyke, Michael; Bassichis, William
2011-10-01
Calculus-based introductory physics courses intended for future engineers and physicists are often designed and taught in the same fashion as those intended for students of other disciplines. A more mathematically rigorous curriculum should be more appropriate and, ultimately, more beneficial for the student in his or her future coursework. This work investigates the effects of mathematical rigor on student understanding of introductory mechanics. Using a series of diagnostic tools in conjunction with individual student course performance, a statistical analysis will be performed to examine student learning of introductory mechanics and its relation to student understanding of the underlying calculus.
Rapid installation of numerical models in multiple parent codes
Energy Technology Data Exchange (ETDEWEB)
Brannon, R.M.; Wong, M.K.
1996-10-01
A set of``model interface guidelines``, called MIG, is offered as a means to more rapidly install numerical models (such as stress-strain laws) into any parent code (hydrocode, finite element code, etc.) without having to modify the model subroutines. The model developer (who creates the model package in compliance with the guidelines) specifies the model`s input and storage requirements in a standardized way. For portability, database management (such as saving user inputs and field variables) is handled by the parent code. To date, NUG has proved viable in beta installations of several diverse models in vectorized and parallel codes written in different computer languages. A NUG-compliant model can be installed in different codes without modifying the model`s subroutines. By maintaining one model for many codes, MIG facilitates code-to-code comparisons and reduces duplication of effort potentially reducing the cost of installing and sharing models.
Development of a numerical 2-dimensional beach evolution model
DEFF Research Database (Denmark)
Baykal, Cüneyt
2014-01-01
This paper presents the description of a 2-dimensional numerical model constructed for the simulation of beach evolution under the action of wind waves only over the arbitrary land and sea topographies around existing coastal structures and formations. The developed beach evolution numerical model...... is composed of 4 submodels: a nearshore spectral wave transformation model based on an energy balance equation including random wave breaking and diffraction terms to compute the nearshore wave characteristics, a nearshore wave-induced circulation model based on the nonlinear shallow water equations...... to compute the nearshore depth-averaged wave-induced current velocities and mean water level changes, a sediment transport model to compute the local total sediment transport rates occurring under the action of wind waves, and a bottom evolution model to compute the bed level changes in time based...
The Liquid Film Flow with Evaporation: Numerical Modelling
Directory of Open Access Journals (Sweden)
Rezanova Ekaterina
2016-01-01
Full Text Available The flow of thin liquid layer on an inclined substrate is investigated numerically. The mathematical modelling is based on the Oberbeck-Boussinesq equations and the generalized conditions on the thermocapillary boundary simplified during the parametrical analysis. In the framework of the long-wave approximation the evolution equation which determines the thickness of the liquid layer in the case of moderate Reynolds numbers is derived. The results of numerical modelling of the liquid flow with evaporation at the interface are obtained.
A numerical method for a transient two-fluid model
International Nuclear Information System (INIS)
Le Coq, G.; Libmann, M.
1978-01-01
The transient boiling two-phase flow is studied. In nuclear reactors, the driving conditions for the transient boiling are a pump power decay or/and an increase in heating power. The physical model adopted for the two-phase flow is the two fluid model with the assumption that the vapor remains at saturation. The numerical method for solving the thermohydraulics problems is a shooting method, this method is highly implicit. A particular problem exists at the boiling and condensation front. A computer code using this numerical method allow the calculation of a transient boiling initiated by a steady state for a PWR or for a LMFBR
Calibration and verification of numerical runoff and erosion model
Directory of Open Access Journals (Sweden)
Gabrić Ognjen
2015-01-01
Full Text Available Based on the field and laboratory measurements, and analogous with development of computational techniques, runoff and erosion models based on equations which describe the physics of the process are also developed. Based on the KINEROS2 model, this paper presents basic modelling principles of runoff and erosion processes based on the St. Venant's equations. Alternative equations for friction calculation, calculation of source and deposition elements and transport capacity are also shown. Numerical models based on original and alternative equations are calibrated and verified on laboratory scale model. According to the results, friction calculation based on the analytic solution of laminar flow must be included in all runoff and erosion models.
Development of Numerical Grids for UZ Flow and Transport Modeling
International Nuclear Information System (INIS)
Hinds, J.
2001-01-01
This Analysis/Model Report (AMR) describes the methods used to develop numerical grids of the unsaturated hydrogeologic system beneath Yucca Mountain. Numerical grid generation is an integral part of the development of a complex, three-dimensional (3-D) model, such as the Unsaturated-Zone Flow and Transport Model (UZ Model) of Yucca Mountain. The resulting numerical grids, developed using current geologic, hydrogeologic, and mineralogic data, provide the necessary framework to: (1) develop calibrated hydrogeologic property sets and flow fields, (2) test conceptual hypotheses of flow and transport, and (3) predict flow and transport behavior under a variety of climatic and thermal loading conditions. Revision 00 of the work described herein follows the planning and work direction outlined in the ''Development of Numerical Grids for UZ Flow and Transport Modeling'' (CRWMS M and O 1999c). The technical scope, content, and management of ICN 01 of this AMR is currently controlled by the planning document, ''Technical Work Plan for Unsaturated Zone (UZ) Flow and Transport Process Model Report'' (BSC 2001a). The scope for the TBV resolution actions in this ICN is described in the ''Technical Work Plan for: Integrated Management of Technical Product Input Department'' (BSC 2001 b, Addendum B, Section 4.1). The steps involved in numerical grid development include: (1) defining the location of important calibration features, (2) determining model grid layers and fault geometry based on the Geologic Framework Model (GFM), the Integrated Site Model (ISM), and definition of hydrogeologic units (HGUs), (3) analyzing and extracting GFM and ISM data pertaining to layer contacts and property distributions, (4) discretizing and refining the two-dimensional (2-D), plan-view numerical grid, (5) generating the 3-D grid with finer resolution at the repository horizon and within the Calico Hills nonwelded (CHn) hydrogeologic unit, and (6) formulating the dual-permeability mesh. The
Numerical modelling of carbonate platforms and reefs: approaches and opportunities
Energy Technology Data Exchange (ETDEWEB)
Dalmasso, H.; Montaggioni, L.F.; Floquet, M. [Universite de Provence, Marseille (France). Centre de Sedimentologie-Palaeontologie; Bosence, D. [Royal Holloway University of London, Egham (United Kingdom). Dept. of Geology
2001-07-01
This paper compares different computing procedures that have been utilized in simulating shallow-water carbonate platform development. Based on our geological knowledge we can usually give a rather accurate qualitative description of the mechanisms controlling geological phenomena. Further description requires the use of computer stratigraphic simulation models that allow quantitative evaluation and understanding of the complex interactions of sedimentary depositional carbonate systems. The roles of modelling include: (1) encouraging accuracy and precision in data collection and process interpretation (Watney et al., 1999); (2) providing a means to quantitatively test interpretations concerning the control of various mechanisms on producing sedimentary packages; (3) predicting or extrapolating results into areas of limited control; (4) gaining new insights regarding the interaction of parameters; (5) helping focus on future studies to resolve specific problems. This paper addresses two main questions, namely: (1) What are the advantages and disadvantages of various types of models? (2) How well do models perform? In this paper we compare and discuss the application of five numerical models: CARBONATE (Bosence and Waltham, 1990), FUZZIM (Nordlund, 1999), CARBPLAT (Bosscher, 1992), DYNACARB (Li et al., 1993), PHIL (Bowman, 1997) and SEDPAK (Kendall et al., 1991). The comparison, testing and evaluation of these models allow one to gain a better knowledge and understanding of controlling parameters of carbonate platform development, which are necessary for modelling. Evaluating numerical models, critically comparing results from models using different approaches, and pushing experimental tests to their limits, provide an effective vehicle to improve and develop new numerical models. A main feature of this paper is to closely compare the performance between two numerical models: a forward model (CARBONATE) and a fuzzy logic model (FUZZIM). These two models use common
Mathematical modeling and numerical simulation of Czochralski Crystal Growth
Energy Technology Data Exchange (ETDEWEB)
Jaervinen, J.; Nieminen, R. [Center for Scientific Computing, Espoo (Finland)
1996-12-31
A detailed mathematical model and numerical simulation tools based on the SUPG Finite Element Method for the Czochralski crystal growth has been developed. In this presentation the mathematical modeling and numerical simulation of the melt flow and the temperature distribution in a rotationally symmetric crystal growth environment is investigated. The temperature distribution and the position of the free boundary between the solid and liquid phases are solved by using the Enthalpy method. Heat inside of the Czochralski furnace is transferred by radiation, conduction and convection. The melt flow is governed by the incompressible Navier-Stokes equations coupled with the enthalpy equation. The melt flow is numerically demonstrated and the temperature distribution in the whole Czochralski furnace. (author)
Behavioral modeling of SRIM tables for numerical simulation
Energy Technology Data Exchange (ETDEWEB)
Martinie, S., E-mail: sebastien.martinie@cea.fr; Saad-Saoud, T.; Moindjie, S.; Munteanu, D.; Autran, J.L., E-mail: jean-luc.autran@univ-amu.fr
2014-03-01
Highlights: • Behavioral modeling of SRIM data is performed on the basis of power polynomial fitting functions. • Fast and continuous numerical functions are proposed for the stopping power and projected range. • Functions have been successfully tested for a wide variety of ions and targets. • Typical accuracies below the percent have been obtained in the range 1 keV–1 GeV. - Abstract: This work describes a simple way to implement SRIM stopping power and range tabulated data in the form of fast and continuous numerical functions for intensive simulation. We provide here the methodology of this behavioral modeling as well as the details of the implementation and some numerical examples for ions in silicon target. Developed functions have been successfully tested and used for the simulation of soft errors in microelectronics circuits.
Mathematical modeling and numerical simulation of Czochralski Crystal Growth
Energy Technology Data Exchange (ETDEWEB)
Jaervinen, J; Nieminen, R [Center for Scientific Computing, Espoo (Finland)
1997-12-31
A detailed mathematical model and numerical simulation tools based on the SUPG Finite Element Method for the Czochralski crystal growth has been developed. In this presentation the mathematical modeling and numerical simulation of the melt flow and the temperature distribution in a rotationally symmetric crystal growth environment is investigated. The temperature distribution and the position of the free boundary between the solid and liquid phases are solved by using the Enthalpy method. Heat inside of the Czochralski furnace is transferred by radiation, conduction and convection. The melt flow is governed by the incompressible Navier-Stokes equations coupled with the enthalpy equation. The melt flow is numerically demonstrated and the temperature distribution in the whole Czochralski furnace. (author)
Behavioral modeling of SRIM tables for numerical simulation
International Nuclear Information System (INIS)
Martinie, S.; Saad-Saoud, T.; Moindjie, S.; Munteanu, D.; Autran, J.L.
2014-01-01
Highlights: • Behavioral modeling of SRIM data is performed on the basis of power polynomial fitting functions. • Fast and continuous numerical functions are proposed for the stopping power and projected range. • Functions have been successfully tested for a wide variety of ions and targets. • Typical accuracies below the percent have been obtained in the range 1 keV–1 GeV. - Abstract: This work describes a simple way to implement SRIM stopping power and range tabulated data in the form of fast and continuous numerical functions for intensive simulation. We provide here the methodology of this behavioral modeling as well as the details of the implementation and some numerical examples for ions in silicon target. Developed functions have been successfully tested and used for the simulation of soft errors in microelectronics circuits
Numerical modeling of turbulent combustion and flame spread
Energy Technology Data Exchange (ETDEWEB)
Yan Zhenghua
1999-01-01
Theoretical models have been developed to address several important aspects of numerical modeling of turbulent combustion and flame spread. The developed models include a pyrolysis model for charring and non-charring solid materials, a fast narrow band radiation property evaluation model (FASTNB) and a turbulence model for buoyant flow and flame. In the pyrolysis model, a completely new algorithm has been proposed, where a moving dual mesh concept was developed and implemented. With this new concept, it provides proper spatial resolution for both temperature and density and automatically considers the regression of the surface of the non-charring solid material during its pyrolysis. It is simple, very efficient and applicable to both charring and non-charring materials. FASTNB speeds up significantly the evaluation of narrow band spectral radiation properties and thus provides a potential of applying narrow band model in numerical simulations of practical turbulent combustion. The turbulence model was developed to improve the consideration of buoyancy effect on turbulence and turbulent transport. It was found to be simple, promising and numerically stable. It has been tested against both plane and axisymmetric thermal plumes and an axisymmetric buoyant diffusion flame. When compared with the widely used standard buoyancy-modified {kappa} - {epsilon} model, it gives significant improvement on numerical results. These developed models have been fully incorporated into CFD (Computational Fluid Dynamics) code and coupled with other CFD sub-models, including the DT (Discrete Transfer) radiation model, EDC (Eddy Dissipation Concept) combustion model, flamelet combustion model, various soot models and transpired wall function. Comprehensive numerical simulations have been carried out to study soot formation and oxidation in turbulent buoyant diffusion flames, flame heat transfer and flame spread in fires. The gas temperature and velocity, soot volume fraction, wall
Physical and numerical modeling of Joule-heated melters
Energy Technology Data Exchange (ETDEWEB)
Eyler, L.L.; Skarda, R.J.; Crowder, R.S. III; Trent, D.S.; Reid, C.R.; Lessor, D.L.
1985-10-01
The Joule-heated ceramic-lined melter is an integral part of the high level waste immobilization process under development by the US Department of Energy. Scaleup and design of this waste glass melting furnace requires an understanding of the relationships between melting cavity design parameters and the furnace performance characteristics such as mixing, heat transfer, and electrical requirements. Developing empirical models of these relationships through actual melter testing with numerous designs would be a very costly and time consuming task. Additionally, the Pacific Northwest Laboratory (PNL) has been developing numerical models that simulate a Joule-heated melter for analyzing melter performance. This report documents the method used and results of this modeling effort. Numerical modeling results are compared with the more conventional, physical modeling results to validate the approach. Also included are the results of numerically simulating an operating research melter at PNL. Physical Joule-heated melters modeling results used for qualiying the simulation capabilities of the melter code included: (1) a melter with a single pair of electrodes and (2) a melter with a dual pair (two pairs) of electrodes. The physical model of the melter having two electrode pairs utilized a configuration with primary and secondary electrodes. The principal melter parameters (the ratio of power applied to each electrode pair, modeling fluid depth, electrode spacing) were varied in nine tests of the physical model during FY85. Code predictions were made for five of these tests. Voltage drops, temperature field data, and electric field data varied in their agreement with the physical modeling results, but in general were judged acceptable. 14 refs., 79 figs., 17 tabs.
Physical and numerical modeling of Joule-heated melters
International Nuclear Information System (INIS)
Eyler, L.L.; Skarda, R.J.; Crowder, R.S. III; Trent, D.S.; Reid, C.R.; Lessor, D.L.
1985-10-01
The Joule-heated ceramic-lined melter is an integral part of the high level waste immobilization process under development by the US Department of Energy. Scaleup and design of this waste glass melting furnace requires an understanding of the relationships between melting cavity design parameters and the furnace performance characteristics such as mixing, heat transfer, and electrical requirements. Developing empirical models of these relationships through actual melter testing with numerous designs would be a very costly and time consuming task. Additionally, the Pacific Northwest Laboratory (PNL) has been developing numerical models that simulate a Joule-heated melter for analyzing melter performance. This report documents the method used and results of this modeling effort. Numerical modeling results are compared with the more conventional, physical modeling results to validate the approach. Also included are the results of numerically simulating an operating research melter at PNL. Physical Joule-heated melters modeling results used for qualiying the simulation capabilities of the melter code included: (1) a melter with a single pair of electrodes and (2) a melter with a dual pair (two pairs) of electrodes. The physical model of the melter having two electrode pairs utilized a configuration with primary and secondary electrodes. The principal melter parameters (the ratio of power applied to each electrode pair, modeling fluid depth, electrode spacing) were varied in nine tests of the physical model during FY85. Code predictions were made for five of these tests. Voltage drops, temperature field data, and electric field data varied in their agreement with the physical modeling results, but in general were judged acceptable. 14 refs., 79 figs., 17 tabs
Numerical Simulation of the Heston Model under Stochastic Correlation
Directory of Open Access Journals (Sweden)
Long Teng
2017-12-01
Full Text Available Stochastic correlation models have become increasingly important in financial markets. In order to be able to price vanilla options in stochastic volatility and correlation models, in this work, we study the extension of the Heston model by imposing stochastic correlations driven by a stochastic differential equation. We discuss the efficient algorithms for the extended Heston model by incorporating stochastic correlations. Our numerical experiments show that the proposed algorithms can efficiently provide highly accurate results for the extended Heston by including stochastic correlations. By investigating the effect of stochastic correlations on the implied volatility, we find that the performance of the Heston model can be proved by including stochastic correlations.
Numerical model for the thermal behavior of thermocline storage tanks
Ehtiwesh, Ismael A. S.; Sousa, Antonio C. M.
2018-03-01
Energy storage is a critical factor in the advancement of solar thermal power systems for the sustained delivery of electricity. In addition, the incorporation of thermal energy storage into the operation of concentrated solar power systems (CSPs) offers the potential of delivering electricity without fossil-fuel backup even during peak demand, independent of weather conditions and daylight. Despite this potential, some areas of the design and performance of thermocline systems still require further attention for future incorporation in commercial CSPs, particularly, their operation and control. Therefore, the present study aims to develop a simple but efficient numerical model to allow the comprehensive analysis of thermocline storage systems aiming better understanding of their dynamic temperature response. The validation results, despite the simplifying assumptions of the numerical model, agree well with the experiments for the time evolution of the thermocline region. Three different cases are considered to test the versatility of the numerical model; for the particular type of a storage tank with top round impingement inlet, a simple analytical model was developed to take into consideration the increased turbulence level in the mixing region. The numerical predictions for the three cases are in general good agreement against the experimental results.
Bubbles in inkjet printheads: analytical and numerical models
Jeurissen, R.J.M.
2009-01-01
The phenomenon of nozzle failure of an inkjet printhead due to entrainment of air bubbles was studies using analytical and numerical models. The studied inkjet printheads consist of many channels in which an acoustic field is generated to eject a droplet. When an air bubble is entrained, it disrupts
Bubbles in inkjet printheads : analytical and numerical models
Jeurissen, R.J.M.
2009-01-01
The phenomenon of nozzle failure of an inkjet printhead due to entrainment of air bubbles was studies using analytical and numerical models. The studied inkjet printheads consist of many channels in which an acoustic field is generated to eject a droplet. When an air bubble is entrained, it disrupts
Numerical modeling of secondary side thermohydraulics of horizontal steam generator
Energy Technology Data Exchange (ETDEWEB)
Melikhov, V.I.; Melikhov, O.I.; Nigmatulin, B.I. [Research and Engineering Centre of LWR Nuclear Plants Safety, Moscow (Russian Federation)
1995-12-31
A mathematical model for the transient three-dimensional secondary side thermal hydraulics of the horizontal steam generator has been developed. The calculations of the steam generator PGV-1000 and PGV-4 nominal regimes and comparison of numerical and experimental results have been carried out. 7 refs.
LED-based Photometric Stereo: Modeling, Calibration and Numerical Solutions
DEFF Research Database (Denmark)
Quéau, Yvain; Durix, Bastien; Wu, Tao
2018-01-01
We conduct a thorough study of photometric stereo under nearby point light source illumination, from modeling to numerical solution, through calibration. In the classical formulation of photometric stereo, the luminous fluxes are assumed to be directional, which is very difficult to achieve in pr...
Numerical modeling of secondary side thermohydraulics of horizontal steam generator
Energy Technology Data Exchange (ETDEWEB)
Melikhov, V I; Melikhov, O I; Nigmatulin, B I [Research and Engineering Centre of LWR Nuclear Plants Safety, Moscow (Russian Federation)
1996-12-31
A mathematical model for the transient three-dimensional secondary side thermal hydraulics of the horizontal steam generator has been developed. The calculations of the steam generator PGV-1000 and PGV-4 nominal regimes and comparison of numerical and experimental results have been carried out. 7 refs.
Development of numerical Grids for UZ Flow and Transport Modeling
International Nuclear Information System (INIS)
P. Dobson
2004-01-01
This report describes the methods used to develop numerical grids of the unsaturated hydrogeologic system beneath Yucca Mountain, Nevada. Numerical grid generation is an integral part of the development of the unsaturated zone (UZ) flow and transport model, a complex, three-dimensional (3-D) model of Yucca Mountain. This revision contains changes made to improve the clarity of the description of grid generation. The numerical grids, developed using current geologic, hydrogeologic, and mineralogic data, provide the necessary framework to: (1) develop calibrated hydrogeologic property sets and flow fields, (2) test conceptual hypotheses of flow and transport, and (3) predict flow and transport behavior under a variety of climatic and thermal-loading conditions. The technical scope, content, and management for the current revision of this report are described in the planning document ''Technical Work Plan for: Unsaturated Zone Flow Analysis and Model Report Integration'' (BSC 2004 [DIRS 169654], Section 2). Grids generated and documented in this report supersede those documented in Revision 00 of this report, ''Development of Numerical Grids for UZ Flow and Transport Modeling'' (BSC 2001 [DIRS 159356]). The grids presented in this report are the same as those developed in Revision 01 (BSC 2003 [DIRS 160109]); however, the documentation of the development of the grids in Revision 02 has been updated to address technical inconsistencies and achieve greater transparency, readability, and traceability. The constraints, assumptions, and limitations associated with this report are discussed in the appropriate sections that follow
Physical and numerical modelling of low mach number compressible flows
International Nuclear Information System (INIS)
Paillerre, H.; Clerc, S.; Dabbene, F.; Cueto, O.
1999-01-01
This article reviews various physical models that may be used to describe compressible flow at low Mach numbers, as well as the numerical methods developed at DRN to discretize the different systems of equations. A selection of thermal-hydraulic applications illustrate the need to take into account compressibility and multidimensional effects as well as variable flow properties. (authors)
Numerical Modeling of Multi-Material Active Magnetic Regeneration
DEFF Research Database (Denmark)
Nielsen, Kaspar Kirstein; Engelbrecht, Kurt; Bahl, Christian Robert Haffenden
2009-01-01
and the specific heat as a function of temperature at constant magnetic field. A 2.5-dimensional numerical model of an active magnetic regenerative (AMR) refrigerator device is presented. The experimental AMR located at Risø DTU has been equipped with a parallel-plate based regenerator made of the two materials...
Numeral eddy current sensor modelling based on genetic neural network
International Nuclear Information System (INIS)
Yu Along
2008-01-01
This paper presents a method used to the numeral eddy current sensor modelling based on the genetic neural network to settle its nonlinear problem. The principle and algorithms of genetic neural network are introduced. In this method, the nonlinear model parameters of the numeral eddy current sensor are optimized by genetic neural network (GNN) according to measurement data. So the method remains both the global searching ability of genetic algorithm and the good local searching ability of neural network. The nonlinear model has the advantages of strong robustness, on-line modelling and high precision. The maximum nonlinearity error can be reduced to 0.037% by using GNN. However, the maximum nonlinearity error is 0.075% using the least square method
Wind laws for shockless initialization. [numerical forecasting model
Ghil, M.; Shkoller, B.
1976-01-01
A system of diagnostic equations for the velocity field, or wind laws, was derived for each of a number of models of large-scale atmospheric flow. The derivation in each case is mathematically exact and does not involve any physical assumptions not already present in the prognostic equations, such as nondivergence or vanishing of derivatives of the divergence. Therefore, initial states computed by solving these diagnostic equations should be compatible with the type of motion described by the prognostic equations of the model and should not generate initialization shocks when inserted into the model. Numerical solutions of the diagnostic system corresponding to a barotropic model are exhibited. Some problems concerning the possibility of implementing such a system in operational numerical weather prediction are discussed.
Numerical modeling of batch formation in waste incineration plants
Directory of Open Access Journals (Sweden)
Obroučka Karel
2015-03-01
Full Text Available The aim of this paper is a mathematical description of algorithm for controlled assembly of incinerated batch of waste. The basis for formation of batch is selected parameters of incinerated waste as its calorific value or content of pollutants or the combination of both. The numerical model will allow, based on selected criteria, to compile batch of wastes which continuously follows the previous batch, which is a prerequisite for optimized operation of incinerator. The model was prepared as for waste storage in containers, as well as for waste storage in continuously refilled boxes. The mathematical model was developed into the computer program and its functionality was verified either by practical measurements or by numerical simulations. The proposed model can be used in incinerators for hazardous and municipal waste.
The Finite Element Numerical Modelling of 3D Magnetotelluric
Directory of Open Access Journals (Sweden)
Ligang Cao
2014-01-01
Full Text Available The ideal numerical simulation of 3D magnetotelluric was restricted by the methodology complexity and the time-consuming calculation. Boundary values, the variation of weighted residual equation, and the hexahedral mesh generation method of finite element are three major causes. A finite element method for 3D magnetotelluric numerical modeling is presented in this paper as a solution for the problem mentioned above. In this algorithm, a hexahedral element coefficient matrix for magnetoelluric finite method is developed, which solves large-scale equations using preconditioned conjugate gradient of the first-type boundary conditions. This algorithm is verified using the homogeneous model, and the positive landform model, as well as the low resistance anomaly model.
Numerical modelling of damage evolution in ingot forging
DEFF Research Database (Denmark)
Christiansen, Peter; Martins, Paulo A.F.; Bay, Niels Oluf
2015-01-01
The ingot forging process is numerically simulated applying both the Shima-Oyane porous plasticity model as a coupled damage model and the uncoupled normalized Cockcroft & Latham criterion. Four different cases including two different lower die angles (120º and 180º) and two different sizes of feed...... (400mm and 800mm) are analysed. Comparison of the simulation results with recommendations in literature on ingot forging, indicates the normalized Cockcroft & Latham damage criterion to be the most realistic of the two....
Numerical modeling of oil spills in continental and estuarine waters
International Nuclear Information System (INIS)
Goeury, C.
2012-10-01
The application of the European Water Framework Directive on water quality for human consumption and industrial activities creates a need for water quality assessment and monitoring systems. The MIGR'HYCAR research project (http://www.migrhycar.com) was initiated to provide decisional tools for risks connected to oil spills in continental waters (rivers, lakes and estuaries), which represent more than 50% of accidental spills in France. Within the framework of this project, a new numerical oil spill model has been developed, as part of the TELEMAC hydro-informatics system (http://www.opentelemac.org), by combining Lagrangian and Eulerian methods. The Lagrangian model describes the transport of an oil spill near the free surface. The oil spill model enables to simulate the main processes driving oil plumes: advection, diffusion, oil beaching, oil re-floating, evaporation, dissolution, spreading and volatilization. Though generally considered as a minor process, dissolution is important from the point of view of toxicity. To model dissolved oil in water, an Eulerian advection-diffusion model is used. The fraction of dissolved oil is represented by a passive tracer. This approach is able to follow dissolved hydrocarbons in the water column. Laboratory experiments were conducted to characterise the numerous kinetics of the processes listed above. In addition, meso-scale dynamic experiments in artificial channels and test cases derived from the literature are used to validate the numerical model. (author)
Analysis and modeling of subgrid scalar mixing using numerical data
Girimaji, Sharath S.; Zhou, YE
1995-01-01
Direct numerical simulations (DNS) of passive scalar mixing in isotropic turbulence is used to study, analyze and, subsequently, model the role of small (subgrid) scales in the mixing process. In particular, we attempt to model the dissipation of the large scale (supergrid) scalar fluctuations caused by the subgrid scales by decomposing it into two parts: (1) the effect due to the interaction among the subgrid scales; and (2) the effect due to interaction between the supergrid and the subgrid scales. Model comparisons with DNS data show good agreement. This model is expected to be useful in the large eddy simulations of scalar mixing and reaction.
Kim, J.; Sonnenthal, E. L.; Rutqvist, J.
2011-12-01
Rigorous modeling of coupling between fluid, heat, and geomechanics (thermo-poro-mechanics), in fractured porous media is one of the important and difficult topics in geothermal reservoir simulation, because the physics are highly nonlinear and strongly coupled. Coupled fluid/heat flow and geomechanics are investigated using the multiple interacting continua (MINC) method as applied to naturally fractured media. In this study, we generalize constitutive relations for the isothermal elastic dual porosity model proposed by Berryman (2002) to those for the non-isothermal elastic/elastoplastic multiple porosity model, and derive the coupling coefficients of coupled fluid/heat flow and geomechanics and constraints of the coefficients. When the off-diagonal terms of the total compressibility matrix for the flow problem are zero, the upscaled drained bulk modulus for geomechanics becomes the harmonic average of drained bulk moduli of the multiple continua. In this case, the drained elastic/elastoplastic moduli for mechanics are determined by a combination of the drained moduli and volume fractions in multiple porosity materials. We also determine a relation between local strains of all multiple porosity materials in a gridblock and the global strain of the gridblock, from which we can track local and global elastic/plastic variables. For elastoplasticity, the return mapping is performed for all multiple porosity materials in the gridblock. For numerical implementation, we employ and extend the fixed-stress sequential method of the single porosity model to coupled fluid/heat flow and geomechanics in multiple porosity systems, because it provides numerical stability and high accuracy. This sequential scheme can be easily implemented by using a porosity function and its corresponding porosity correction, making use of the existing robust flow and geomechanics simulators. We implemented the proposed modeling and numerical algorithm to the reaction transport simulator
Numerical models for fluid-grains interactions: opportunities and limitations
Esteghamatian, Amir; Rahmani, Mona; Wachs, Anthony
2017-06-01
In the framework of a multi-scale approach, we develop numerical models for suspension flows. At the micro scale level, we perform particle-resolved numerical simulations using a Distributed Lagrange Multiplier/Fictitious Domain approach. At the meso scale level, we use a two-way Euler/Lagrange approach with a Gaussian filtering kernel to model fluid-solid momentum transfer. At both the micro and meso scale levels, particles are individually tracked in a Lagrangian way and all inter-particle collisions are computed by a Discrete Element/Soft-sphere method. The previous numerical models have been extended to handle particles of arbitrary shape (non-spherical, angular and even non-convex) as well as to treat heat and mass transfer. All simulation tools are fully-MPI parallel with standard domain decomposition and run on supercomputers with a satisfactory scalability on up to a few thousands of cores. The main asset of multi scale analysis is the ability to extend our comprehension of the dynamics of suspension flows based on the knowledge acquired from the high-fidelity micro scale simulations and to use that knowledge to improve the meso scale model. We illustrate how we can benefit from this strategy for a fluidized bed, where we introduce a stochastic drag force model derived from micro-scale simulations to recover the proper level of particle fluctuations. Conversely, we discuss the limitations of such modelling tools such as their limited ability to capture lubrication forces and boundary layers in highly inertial flows. We suggest ways to overcome these limitations in order to enhance further the capabilities of the numerical models.
Numerical Analysis of Electromagnetic Fields in Multiscale Model
International Nuclear Information System (INIS)
Ma Ji; Fang Guang-You; Ji Yi-Cai
2015-01-01
Modeling technique for electromagnetic fields excited by antennas is an important topic in computational electromagnetics, which is concerned with the numerical solution of Maxwell's equations. In this paper, a novel hybrid technique that combines method of moments (MoM) with finite-difference time-domain (FDTD) method is presented to handle the problem. This approach employed Huygen's principle to realize the hybridization of the two classical numerical algorithms. For wideband electromagnetic data, the interpolation scheme is used in the MoM based on the dyadic Green's function. On the other hand, with the help of equivalence principle, the scattered electric and magnetic fields on the Huygen's surface calculated by MoM are taken as the sources for FDTD. Therefore, the electromagnetic fields in the environment can be obtained by employing finite-difference time-domain method. Finally, numerical results show the validity of the proposed technique by analyzing two canonical samples. (paper)
Numerical modeling and experimental validation of thermoplastic composites induction welding
Palmieri, Barbara; Nele, Luigi; Galise, Francesco
2018-05-01
In this work, a numerical simulation and experimental test of the induction welding of continuous fibre-reinforced thermoplastic composites (CFRTPCs) was provided. The thermoplastic Polyamide 66 (PA66) with carbon fiber fabric was used. Using a dedicated software (JMag Designer), the influence of the fundamental process parameters such as temperature, current and holding time was investigated. In order to validate the results of the simulations, and therefore the numerical model used, experimental tests were carried out, and the temperature values measured during the tests were compared with the aid of an optical pyrometer, with those provided by the numerical simulation. The mechanical properties of the welded joints were evaluated by single lap shear tests.
Direct numerical methods of mathematical modeling in mechanical structural design
International Nuclear Information System (INIS)
Sahili, Jihad; Verchery, Georges; Ghaddar, Ahmad; Zoaeter, Mohamed
2002-01-01
Full text.Structural design and numerical methods are generally interactive; requiring optimization procedures as the structure is analyzed. This analysis leads to define some mathematical terms, as the stiffness matrix, which are resulting from the modeling and then used in numerical techniques during the dimensioning procedure. These techniques and many others involve the calculation of the generalized inverse of the stiffness matrix, called also the 'compliance matrix'. The aim of this paper is to introduce first, some different existing mathematical procedures, used to calculate the compliance matrix from the stiffness matrix, then apply direct numerical methods to solve the obtained system with the lowest computational time, and to compare the obtained results. The results show a big difference of the computational time between the different procedures
A case of instantaneous rigor?
Pirch, J; Schulz, Y; Klintschar, M
2013-09-01
The question of whether instantaneous rigor mortis (IR), the hypothetic sudden occurrence of stiffening of the muscles upon death, actually exists has been controversially debated over the last 150 years. While modern German forensic literature rejects this concept, the contemporary British literature is more willing to embrace it. We present the case of a young woman who suffered from diabetes and who was found dead in an upright standing position with back and shoulders leaned against a punchbag and a cupboard. Rigor mortis was fully established, livor mortis was strong and according to the position the body was found in. After autopsy and toxicological analysis, it was stated that death most probably occurred due to a ketoacidotic coma with markedly increased values of glucose and lactate in the cerebrospinal fluid as well as acetone in blood and urine. Whereas the position of the body is most unusual, a detailed analysis revealed that it is a stable position even without rigor mortis. Therefore, this case does not further support the controversial concept of IR.
Accelerating Biomedical Discoveries through Rigor and Transparency.
Hewitt, Judith A; Brown, Liliana L; Murphy, Stephanie J; Grieder, Franziska; Silberberg, Shai D
2017-07-01
Difficulties in reproducing published research findings have garnered a lot of press in recent years. As a funder of biomedical research, the National Institutes of Health (NIH) has taken measures to address underlying causes of low reproducibility. Extensive deliberations resulted in a policy, released in 2015, to enhance reproducibility through rigor and transparency. We briefly explain what led to the policy, describe its elements, provide examples and resources for the biomedical research community, and discuss the potential impact of the policy on translatability with a focus on research using animal models. Importantly, while increased attention to rigor and transparency may lead to an increase in the number of laboratory animals used in the near term, it will lead to more efficient and productive use of such resources in the long run. The translational value of animal studies will be improved through more rigorous assessment of experimental variables and data, leading to better assessments of the translational potential of animal models, for the benefit of the research community and society. Published by Oxford University Press on behalf of the Institute for Laboratory Animal Research 2017. This work is written by (a) US Government employee(s) and is in the public domain in the US.
Numerical modelling of flow and transport in rough fractures
Directory of Open Access Journals (Sweden)
Scott Briggs
2014-12-01
Full Text Available Simulation of flow and transport through rough walled rock fractures is investigated using the lattice Boltzmann method (LBM and random walk (RW, respectively. The numerical implementation is developed and validated on general purpose graphic processing units (GPGPUs. Both the LBM and RW method are well suited to parallel implementation on GPGPUs because they require only next-neighbour communication and thus can reduce expenses. The LBM model is an order of magnitude faster on GPGPUs than published results for LBM simulations run on modern CPUs. The fluid model is verified for parallel plate flow, backward facing step and single fracture flow; and the RW model is verified for point-source diffusion, Taylor-Aris dispersion and breakthrough behaviour in a single fracture. Both algorithms place limitations on the discrete displacement of fluid or particle transport per time step to minimise the numerical error that must be considered during implementation.
Customer requirement modeling and mapping of numerical control machine
Directory of Open Access Journals (Sweden)
Zhongqi Sheng
2015-10-01
Full Text Available In order to better obtain information about customer requirement and develop products meeting customer requirement, it is necessary to systematically analyze and handle the customer requirement. This article uses the product service system of numerical control machine as research objective and studies the customer requirement modeling and mapping oriented toward configuration design. It introduces the conception of requirement unit, expounds the customer requirement decomposition rules, and establishes customer requirement model; it builds the house of quality using quality function deployment and confirms the weight of technical feature of product and service; it explores the relevance rules between data using rough set theory, establishes rule database, and solves the target value of technical feature of product. Using economical turning center series numerical control machine as an example, it verifies the rationality of proposed customer requirement model.
Modern Perspectives on Numerical Modeling of Cardiac Pacemaker Cell
Maltsev, Victor A.; Yaniv, Yael; Maltsev, Anna V.; Stern, Michael D.; Lakatta, Edward G.
2015-01-01
Cardiac pacemaking is a complex phenomenon that is still not completely understood. Together with experimental studies, numerical modeling has been traditionally used to acquire mechanistic insights in this research area. This review summarizes the present state of numerical modeling of the cardiac pacemaker, including approaches to resolve present paradoxes and controversies. Specifically we discuss the requirement for realistic modeling to consider symmetrical importance of both intracellular and cell membrane processes (within a recent “coupled-clock” theory). Promising future developments of the complex pacemaker system models include the introduction of local calcium control, mitochondria function, and biochemical regulation of protein phosphorylation and cAMP production. Modern numerical and theoretical methods such as multi-parameter sensitivity analyses within extended populations of models and bifurcation analyses are also important for the definition of the most realistic parameters that describe a robust, yet simultaneously flexible operation of the coupled-clock pacemaker cell system. The systems approach to exploring cardiac pacemaker function will guide development of new therapies, such as biological pacemakers for treating insufficient cardiac pacemaker function that becomes especially prevalent with advancing age. PMID:24748434
Numerical modeling of the 2017 active seismic infrasound balloon experiment
Brissaud, Q.; Komjathy, A.; Garcia, R.; Cutts, J. A.; Pauken, M.; Krishnamoorthy, S.; Mimoun, D.; Jackson, J. M.; Lai, V. H.; Kedar, S.; Levillain, E.
2017-12-01
We have developed a numerical tool to propagate acoustic and gravity waves in a coupled solid-fluid medium with topography. It is a hybrid method between a continuous Galerkin and a discontinuous Galerkin method that accounts for non-linear atmospheric waves, visco-elastic waves and topography. We apply this method to a recent experiment that took place in the Nevada desert to study acoustic waves from seismic events. This experiment, developed by JPL and its partners, wants to demonstrate the viability of a new approach to probe seismic-induced acoustic waves from a balloon platform. To the best of our knowledge, this could be the only way, for planetary missions, to perform tomography when one faces challenging surface conditions, with high pressure and temperature (e.g. Venus), and thus when it is impossible to use conventional electronics routinely employed on Earth. To fully demonstrate the effectiveness of such a technique one should also be able to reconstruct the observed signals from numerical modeling. To model the seismic hammer experiment and the subsequent acoustic wave propagation, we rely on a subsurface seismic model constructed from the seismometers measurements during the 2017 Nevada experiment and an atmospheric model built from meteorological data. The source is considered as a Gaussian point source located at the surface. Comparison between the numerical modeling and the experimental data could help future mission designs and provide great insights into the planet's interior structure.
A review of laboratory and numerical modelling in volcanology
Directory of Open Access Journals (Sweden)
J. L. Kavanagh
2018-04-01
Full Text Available Modelling has been used in the study of volcanic systems for more than 100 years, building upon the approach first applied by Sir James Hall in 1815. Informed by observations of volcanological phenomena in nature, including eye-witness accounts of eruptions, geophysical or geodetic monitoring of active volcanoes, and geological analysis of ancient deposits, laboratory and numerical models have been used to describe and quantify volcanic and magmatic processes that span orders of magnitudes of time and space. We review the use of laboratory and numerical modelling in volcanological research, focussing on sub-surface and eruptive processes including the accretion and evolution of magma chambers, the propagation of sheet intrusions, the development of volcanic flows (lava flows, pyroclastic density currents, and lahars, volcanic plume formation, and ash dispersal. When first introduced into volcanology, laboratory experiments and numerical simulations marked a transition in approach from broadly qualitative to increasingly quantitative research. These methods are now widely used in volcanology to describe the physical and chemical behaviours that govern volcanic and magmatic systems. Creating simplified models of highly dynamical systems enables volcanologists to simulate and potentially predict the nature and impact of future eruptions. These tools have provided significant insights into many aspects of the volcanic plumbing system and eruptive processes. The largest scientific advances in volcanology have come from a multidisciplinary approach, applying developments in diverse fields such as engineering and computer science to study magmatic and volcanic phenomena. A global effort in the integration of laboratory and numerical volcano modelling is now required to tackle key problems in volcanology and points towards the importance of benchmarking exercises and the need for protocols to be developed so that models are routinely tested against real
A review of laboratory and numerical modelling in volcanology
Kavanagh, Janine L.; Engwell, Samantha L.; Martin, Simon A.
2018-04-01
Modelling has been used in the study of volcanic systems for more than 100 years, building upon the approach first applied by Sir James Hall in 1815. Informed by observations of volcanological phenomena in nature, including eye-witness accounts of eruptions, geophysical or geodetic monitoring of active volcanoes, and geological analysis of ancient deposits, laboratory and numerical models have been used to describe and quantify volcanic and magmatic processes that span orders of magnitudes of time and space. We review the use of laboratory and numerical modelling in volcanological research, focussing on sub-surface and eruptive processes including the accretion and evolution of magma chambers, the propagation of sheet intrusions, the development of volcanic flows (lava flows, pyroclastic density currents, and lahars), volcanic plume formation, and ash dispersal. When first introduced into volcanology, laboratory experiments and numerical simulations marked a transition in approach from broadly qualitative to increasingly quantitative research. These methods are now widely used in volcanology to describe the physical and chemical behaviours that govern volcanic and magmatic systems. Creating simplified models of highly dynamical systems enables volcanologists to simulate and potentially predict the nature and impact of future eruptions. These tools have provided significant insights into many aspects of the volcanic plumbing system and eruptive processes. The largest scientific advances in volcanology have come from a multidisciplinary approach, applying developments in diverse fields such as engineering and computer science to study magmatic and volcanic phenomena. A global effort in the integration of laboratory and numerical volcano modelling is now required to tackle key problems in volcanology and points towards the importance of benchmarking exercises and the need for protocols to be developed so that models are routinely tested against real world data.
Prospect of Using Numerical Dynamo Model for Prediction of Geomagnetic Secular Variation
Kuang, Weijia; Tangborn, Andrew
2003-01-01
Modeling of the Earth's core has reached a level of maturity to where the incorporation of observations into the simulations through data assimilation has become feasible. Data assimilation is a method by which observations of a system are combined with a model output (or forecast) to obtain a best guess of the state of the system, called the analysis. The analysis is then used as an initial condition for the next forecast. By doing assimilation, not only we shall be able to predict partially secular variation of the core field, we could also use observations to further our understanding of dynamical states in the Earth's core. One of the first steps in the development of an assimilation system is a comparison between the observations and the model solution. The highly turbulent nature of core dynamics, along with the absence of any regular external forcing and constraint (which occurs in atmospheric dynamics, for example) means that short time comparisons (approx. 1000 years) cannot be made between model and observations. In order to make sensible comparisons, a direct insertion assimilation method has been implemented. In this approach, magnetic field observations at the Earth's surface have been substituted into the numerical model, such that the ratio of the multiple components and the dipole component from observation is adjusted at the core-mantle boundary and extended to the interior of the core, while the total magnetic energy remains unchanged. This adjusted magnetic field is then used as the initial field for a new simulation. In this way, a time tugged simulation is created which can then be compared directly with observations. We present numerical solutions with and without data insertion and discuss their implications for the development of a more rigorous assimilation system.
Rigorous Quantum Field Theory A Festschrift for Jacques Bros
Monvel, Anne Boutet; Iagolnitzer, Daniel; Moschella, Ugo
2007-01-01
Jacques Bros has greatly advanced our present understanding of rigorous quantum field theory through numerous fundamental contributions. This book arose from an international symposium held in honour of Jacques Bros on the occasion of his 70th birthday, at the Department of Theoretical Physics of the CEA in Saclay, France. The impact of the work of Jacques Bros is evident in several articles in this book. Quantum fields are regarded as genuine mathematical objects, whose various properties and relevant physical interpretations must be studied in a well-defined mathematical framework. The key topics in this volume include analytic structures of Quantum Field Theory (QFT), renormalization group methods, gauge QFT, stability properties and extension of the axiomatic framework, QFT on models of curved spacetimes, QFT on noncommutative Minkowski spacetime. Contributors: D. Bahns, M. Bertola, R. Brunetti, D. Buchholz, A. Connes, F. Corbetta, S. Doplicher, M. Dubois-Violette, M. Dütsch, H. Epstein, C.J. Fewster, K....
Modelization and numerical simulation of atmospheric aerosols dynamics
International Nuclear Information System (INIS)
Debry, Edouard
2004-01-01
Chemical-transport models are now able to describe in a realistic way gaseous pollutants behavior in the atmosphere. Nevertheless atmospheric pollution also exists as a fine suspended particles, called aerosols which interact with gaseous phase, solar radiation, and have their own dynamic behavior. The goal of this thesis is the modelization and numerical simulation of the General Dynamic Equation of aerosols (GDE). Part I deals with some theoretical aspects of aerosol modelization. Part II is dedicated to the building of one size resolved aerosol model (SIREAM). In part III we perform the reduction of this model in order to use it in dispersion models as POLAIR3D. Several modelization issues are still opened: organic aerosol matter, externally mixed aerosols, coupling with turbulent mixing, and nano-particles. (author) [fr
Physicochemical and numerical modeling of electrokinetics in inhomogenous matrices
DEFF Research Database (Denmark)
Paz-Garcia, Juan Manuel
A physicochemical model has been proposed based on the Nernst-Planck-Poisson system. The model includes the transport of water through the porous media, the monitoring of the degree of saturation, the pH value and the porosity throughout the domain; and a comprehensive set of chemical and electrochemical reactions...... is mainly based on a finite elements method for the integration of the transient system of partial differential equations coupled with a Newton-Raphson method for computing chemical equilibrium. During the development of the proposed physicochemical and numerical model, different electrokinetic systems have...
Numerical Modelling Of Humid Air Flow Around A Porous Body
Directory of Open Access Journals (Sweden)
Bohojło-Wiśniewska Aneta
2015-09-01
Full Text Available This paper presents an example of humid air flow around a single head of Chinese cabbage under conditions of complex heat transfer. This kind of numerical simulation allows us to create a heat and humidity transfer model between the Chinese cabbage and the flowing humid air. The calculations utilize the heat transfer model in porous medium, which includes the temperature difference between the solid (vegetable tissue and fluid (air phases of the porous medium. Modelling and calculations were performed in ANSYS Fluent 14.5 software.
Numerical model of solar dynamic radiator for parametric analysis
Rhatigan, Jennifer L.
1989-01-01
Growth power requirements for Space Station Freedom will be met through addition of 25 kW solar dynamic (SD) power modules. Extensive thermal and power cycle modeling capabilities have been developed which are powerful tools in Station design and analysis, but which prove cumbersome and costly for simple component preliminary design studies. In order to aid in refining the SD radiator to the mature design stage, a simple and flexible numerical model was developed. The model simulates heat transfer and fluid flow performance of the radiator and calculates area mass and impact survivability for many combinations of flow tube and panel configurations, fluid and material properties, and environmental and cycle variations.
Rigorous Results for the Distribution of Money on Connected Graphs
Lanchier, Nicolas; Reed, Stephanie
2018-05-01
This paper is concerned with general spatially explicit versions of three stochastic models for the dynamics of money that have been introduced and studied numerically by statistical physicists: the uniform reshuffling model, the immediate exchange model and the model with saving propensity. All three models consist of systems of economical agents that consecutively engage in pairwise monetary transactions. Computer simulations performed in the physics literature suggest that, when the number of agents and the average amount of money per agent are large, the limiting distribution of money as time goes to infinity approaches the exponential distribution for the first model, the gamma distribution with shape parameter two for the second model and a distribution similar but not exactly equal to a gamma distribution whose shape parameter depends on the saving propensity for the third model. The main objective of this paper is to give rigorous proofs of these conjectures and also extend these conjectures to generalizations of the first two models and a variant of the third model that include local rather than global interactions, i.e., instead of choosing the two interacting agents uniformly at random from the system, the agents are located on the vertex set of a general connected graph and can only interact with their neighbors.
Advanced modelling and numerical strategies in nuclear thermal-hydraulics
International Nuclear Information System (INIS)
Staedtke, H.
2001-01-01
The first part of the lecture gives a brief review of the current status of nuclear thermal hydraulics as it forms the basis of established system codes like TRAC, RELAP5, CATHARE or ATHLET. Specific emphasis is given to the capabilities and limitations of the underlying physical modelling and numerical solution strategies with regard to the description of complex transient two-phase flow and heat transfer conditions as expected to occur in PWR reactors during off-normal and accident conditions. The second part of the lecture focuses on new challenges and future needs in nuclear thermal-hydraulics which might arise with regard to re-licensing of old plants using bestestimate methodologies or the design and safety analysis of Advanced Light Water Reactors relying largely on passive safety systems. In order to meet these new requirements various advanced modelling and numerical techniques will be discussed including extended wellposed (hyperbolic) two-fluid models, explicit modelling of interfacial area transport or higher order numerical schemes allowing a high resolution of local multi-dimensional flow processes.(author)
The concept of validation of numerical models for consequence analysis
International Nuclear Information System (INIS)
Borg, Audun; Paulsen Husted, Bjarne; Njå, Ove
2014-01-01
Numerical models such as computational fluid dynamics (CFD) models are increasingly used in life safety studies and other types of analyses to calculate the effects of fire and explosions. The validity of these models is usually established by benchmark testing. This is done to quantitatively measure the agreement between the predictions provided by the model and the real world represented by observations in experiments. This approach assumes that all variables in the real world relevant for the specific study are adequately measured in the experiments and in the predictions made by the model. In this paper the various definitions of validation for CFD models used for hazard prediction are investigated to assess their implication for consequence analysis in a design phase. In other words, how is uncertainty in the prediction of future events reflected in the validation process? The sources of uncertainty are viewed from the perspective of the safety engineer. An example of the use of a CFD model is included to illustrate the assumptions the analyst must make and how these affect the prediction made by the model. The assessments presented in this paper are based on a review of standards and best practice guides for CFD modeling and the documentation from two existing CFD programs. Our main thrust has been to assess how validation work is performed and communicated in practice. We conclude that the concept of validation adopted for numerical models is adequate in terms of model performance. However, it does not address the main sources of uncertainty from the perspective of the safety engineer. Uncertainty in the input quantities describing future events, which are determined by the model user, outweighs the inaccuracies in the model as reported in validation studies. - Highlights: • Examine the basic concept of validation applied to models for consequence analysis. • Review standards and guides for validation of numerical models. • Comparison of the validation
Untangling Slab Dynamics Using 3-D Numerical and Analytical Models
Holt, A. F.; Royden, L.; Becker, T. W.
2016-12-01
Increasingly sophisticated numerical models have enabled us to make significant strides in identifying the key controls on how subducting slabs deform. For example, 3-D models have demonstrated that subducting plate width, and the related strength of toroidal flow around the plate edge, exerts a strong control on both the curvature and the rate of migration of the trench. However, the results of numerical subduction models can be difficult to interpret, and many first order dynamics issues remain at least partially unresolved. Such issues include the dominant controls on trench migration, the interdependence of asthenospheric pressure and slab dynamics, and how nearby slabs influence each other's dynamics. We augment 3-D, dynamically evolving finite element models with simple, analytical force-balance models to distill the physics associated with subduction into more manageable parts. We demonstrate that for single, isolated subducting slabs much of the complexity of our fully numerical models can be encapsulated by simple analytical expressions. Rates of subduction and slab dip correlate strongly with the asthenospheric pressure difference across the subducting slab. For double subduction, an additional slab gives rise to more complex mantle pressure and flow fields, and significantly extends the range of plate kinematics (e.g., convergence rate, trench migration rate) beyond those present in single slab models. Despite these additional complexities, we show that much of the dynamics of such multi-slab systems can be understood using the physics illuminated by our single slab study, and that a force-balance method can be used to relate intra-plate stress to viscous pressure in the asthenosphere and coupling forces at plate boundaries. This method has promise for rapid modeling of large systems of subduction zones on a global scale.
International Nuclear Information System (INIS)
Lorrette, Ch.
2007-04-01
This work is an original contribution to the study of the thermo-structural composite materials thermal behaviour. It aims to develop a methodology with a new experimental device for thermal characterization adapted to this type of material and to model the heat transfer by conduction within these heterogeneous media. The first part deals with prediction of the thermal effective conductivity of stratified composite materials in the three space directions. For that, a multi scale model using a rigorous morphology analysis of the structure and the elementary properties is proposed and implemented. The second part deals with the thermal characterization at high temperature. It shows how to estimate simultaneously the thermal effusiveness and the thermal conductivity. The present method is based on the observation of the heating from a plane sample submitted to a continuous excitation generated by Joule Effect. Heat transfer is modelled with the quadrupole formalism, temperature is here measured on two sides of the sample. The development of both resistive probes for excitation and linear probes for temperature measurements enables the thermal properties measured up to 1000 C. Finally, some experimental and numerical application examples lead to review the obtained results. (author)
Numerical Simulation of Hydrogen Combustion: Global Reaction Model and Validation
Energy Technology Data Exchange (ETDEWEB)
Zhang, Yun [School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an (China); Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY (United States); Liu, Yinhe, E-mail: yinheliu@mail.xjtu.edu.cn [School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an (China)
2017-11-20
Due to the complexity of modeling the combustion process in nuclear power plants, the global mechanisms are preferred for numerical simulation. To quickly perform the highly resolved simulations with limited processing resources of large-scale hydrogen combustion, a method based on thermal theory was developed to obtain kinetic parameters of global reaction mechanism of hydrogen–air combustion in a wide range. The calculated kinetic parameters at lower hydrogen concentration (C{sub hydrogen} < 20%) were validated against the results obtained from experimental measurements in a container and combustion test facility. In addition, the numerical data by the global mechanism (C{sub hydrogen} > 20%) were compared with the results by detailed mechanism. Good agreement between the model prediction and the experimental data was achieved, and the comparison between simulation results by the detailed mechanism and the global reaction mechanism show that the present calculated global mechanism has excellent predictable capabilities for a wide range of hydrogen–air mixtures.
Elements of Constitutive Modelling and Numerical Analysis of Frictional Soils
DEFF Research Database (Denmark)
Jakobsen, Kim Parsberg
of a constitutive model for soil is based on a profound knowledge of the soil behaviour upon loading. In the present study it is attempted to get a better understanding of the soil behaviour bv performing a number of triaxial compression tests on sand. The stress-strain behaviour of sand depends strongly......This thesis deals with elements of elasto-plastic constitutive modelling and numerical analysis of frictional soils. The thesis is based on a number of scientific papers and reports in which central characteristics of soil behaviour and applied numerical techniques are considered. The development...... and subsequently dilates during shear. The change in the volumetric behaviour of the soil skeleton is commonly referred to as the characteristic state. The stress ratio corresponding to the characteristic state is independent of the mean normal effective stress and the relative density, but depends on the stress...
Mathematical and numerical modeling of early atherosclerotic lesions***
Directory of Open Access Journals (Sweden)
Raoult Annie
2010-12-01
Full Text Available This article is devoted to the construction of a mathematical model describing the early formation of atherosclerotic lesions. The early stage of atherosclerosis is an inflammatory process that starts with the penetration of low density lipoproteins in the intima and with their oxidation. This phenomenon is closely linked to the local blood flow dynamics. Extending a previous work [5] that was mainly restricted to a one-dimensional setting, we couple a simple lesion growth model relying on the biomolecular process that takes place in the intima with blood flow dynamics and mass transfer. We perform numerical simulations on a two-dimensional geometry taken from [6,7] that mimicks a carotid artery deformed by a perivascular cast and we compare the numerical results with experimental data.
On numerical considerations for modeling reactive astrophysical shocks
International Nuclear Information System (INIS)
Papatheodore, Thomas L.; Messer, O. E. Bronson
2014-01-01
Simulating detonations in astrophysical environments is often complicated by numerical approximations to shock structure. A common prescription to ensure correct detonation speeds and associated quantities is to prohibit burning inside the numerically broadened shock. We have performed a series of simulations to verify the efficacy of this approximation and to understand how resolution and dimensionality might affect its use. Our results show that in one dimension, prohibiting burning in the shock is important wherever the carbon burning length is not resolved, in keeping with the results of Fryxell et al. In two dimensions, we find that the prohibition of shock burning effectively inhibits the development of cellular structure for all but the most highly resolved cases. We discuss the possible impacts this outcome may have on sub-grid models and detonation propagation in models of Type Ia supernovae, including potential impacts on observables.
Numerical Simulation of Hydrogen Combustion: Global Reaction Model and Validation
International Nuclear Information System (INIS)
Zhang, Yun; Liu, Yinhe
2017-01-01
Due to the complexity of modeling the combustion process in nuclear power plants, the global mechanisms are preferred for numerical simulation. To quickly perform the highly resolved simulations with limited processing resources of large-scale hydrogen combustion, a method based on thermal theory was developed to obtain kinetic parameters of global reaction mechanism of hydrogen–air combustion in a wide range. The calculated kinetic parameters at lower hydrogen concentration (C hydrogen < 20%) were validated against the results obtained from experimental measurements in a container and combustion test facility. In addition, the numerical data by the global mechanism (C hydrogen > 20%) were compared with the results by detailed mechanism. Good agreement between the model prediction and the experimental data was achieved, and the comparison between simulation results by the detailed mechanism and the global reaction mechanism show that the present calculated global mechanism has excellent predictable capabilities for a wide range of hydrogen–air mixtures.
Numerical modeling of a nuclear production reactor cooling lake
International Nuclear Information System (INIS)
Hamm, L.L.; Pepper, D.W.
1987-01-01
A finite element model has been developed which predicts flow and temperature distributions within a nuclear reactor cooling lake at the Savannah River Plant near Aiken, South Carolina. Numerical results agree with values obtained from a 3-D EPA numerical lake model and actual measurements obtained from the lake. Because the effluent water from the reactor heat exchangers discharges directly into the lake, downstream temperatures at mid-lake could exceed the South Carolina DHEC guidelines for thermal exchanges during the summer months. Therefore, reactor power was reduced to maintain temperature compliance at mid-lake. Thermal mitigation measures were studied that included placing a 6.1 m deep fabric curtain across mid-lake and moving the reactor outfall upstream. These measurements were calculated to permit about an 8% improvement in reactor power during summer operation
OPTIMIZATION OF HEATING OF GEAR WHEEL USING NUMERICAL MODELING
Directory of Open Access Journals (Sweden)
Soňa Benešová
2013-09-01
Full Text Available Successful heat treating and carburizing of gear wheels for wind turbine gear boxes requires that plastic deformation in the wheel is minimized. Numerical modeling using the DEFORM software was aimed at exploring the effects of the base, on which the gear wheel rests during heating, on the heating process. Homogeneous heating was assumed. It was found that the base heats up more quickly than the workpiece. It is the consequence of the base's shape and volume. As a result, the base expands and slides against the wheel, predominantly at the first heating stage. Later on, it prevents the gear wheel from expanding, causing plastic deformation in the wheel. The findings were used for designing new heating schedules to minimize these undesirable interactions and to reduce the plastic deformation to a negligible magnitude. In addition, this paper presents an example of a practical use of numerical modeling in the DEFORM software.
OPTIMIZATION OF HEATING OF GEAR WHEEL USING NUMERICAL MODELING
Directory of Open Access Journals (Sweden)
Sona Benesova
2013-05-01
Full Text Available Successful heat treating and carburizing of gear wheels for wind turbine gear boxes requires that plastic deformation in the wheel is minimized. Numerical modeling using the DEFORM software was aimed at exploring the effects of the base, on which the gear wheel rests during heating, on the heating process. Homogeneous heating was assumed. It was found that the base heats up more quickly than the workpiece. It is the consequence of the base's shape and volume. As a result, the base expands and slides against the wheel, predominantly at the first heating stage. Later on, it prevents the gear wheel from expanding, causing plastic deformation in the wheel. The findings were used for designing new heating schedules to minimize these undesirable interactions and to reduce the plastic deformation to a negligible magnitude. In addition, this paper presents an example of a practical use of numerical modeling in the DEFORM software.
New Trends in Model Coupling Theory, Numerics and Applications
International Nuclear Information System (INIS)
Coquel, F.; Godlewski, E.; Herard, J. M.; Segre, J.
2010-01-01
This special issue comprises selected papers from the workshop New Trends in Model Coupling, Theory, Numerics and Applications (NTMC'09) which took place in Paris, September 2 - 4, 2009. The research of optimal technological solutions in a large amount of industrial systems requires to perform numerical simulations of complex phenomena which are often characterized by the coupling of models related to various space and/or time scales. Thus, the so-called multi-scale modelling has been a thriving scientific activity which connects applied mathematics and other disciplines such as physics, chemistry, biology or even social sciences. To illustrate the variety of fields concerned by the natural occurrence of model coupling we may quote: meteorology where it is required to take into account several turbulence scales or the interaction between oceans and atmosphere, but also regional models in a global description, solid mechanics where a thorough understanding of complex phenomena such as propagation of cracks needs to couple various models from the atomistic level to the macroscopic level; plasma physics for fusion energy for instance where dense plasmas and collisionless plasma coexist; multiphase fluid dynamics when several types of flow corresponding to several types of models are present simultaneously in complex circuits; social behaviour analysis with interaction between individual actions and collective behaviour. (authors)
International Nuclear Information System (INIS)
Grange, J.L.; Caremoli, C.; Eddi, M.
1988-01-01
This paper presents improvements performed on SICLE numerical model in order to analyse the condensation front that occurs in the moisture separator reheaters (MSR) of nuclear power plants. Modifications of SICLE numerical model architecture and a fine modelling of reheater have allowed to correctly simulate the MSR thermohydraulic behaviour during a severe transient (plant islanding) [fr
Numerical modeling of underground openings behavior with a viscoplastic approach
International Nuclear Information System (INIS)
Kleine, A.
2007-01-01
Nature is complex and must be approached in total modesty by engineers seeking to predict the behavior of underground openings. The engineering of industrial projects in underground situations, with high economic and social stakes (Alpine mountain crossings, nuclear waste repository), mean striving to gain better understanding of the behavioral mechanisms of the openings to be designed. This improvement necessarily involves better physical representativeness of macroscopic mechanisms and the provision of prediction tools suited to the expectations and needs of the engineers. The calculation tools developed in this work is in step with this concern for satisfying industrial needs and developing knowledge related to the rheology of geo-materials. These developments led to the proposing of a mechanical constitutive model, suited to lightly fissured rocks, comparable to continuous media, while integrating more particularly the effect of time. Thread of this study, the problematics ensued from the subject of the thesis is precisely about the rock mass delayed behavior in numerical modeling and its consequences on underground openings design. Based on physical concepts of reference, defined in several scales (macro/meso/micro), the developed constitutive model is translated in a mathematical formalism in order to be numerically implemented. Numerical applications presented as illustrations fall mainly within the framework of nuclear waste repository problems. They concern two very different configurations of underground openings: the AECL's underground canadian laboratory, excavated in the Lac du Bonnet granite, and the GMR gallery of Bure's laboratory (Meuse/Haute-Marne), dug in argillaceous rock. In this two cases, this constitutive model use highlights the gains to be obtained from allowing for delayed behavior regarding the accuracy of numerical tunnel behavior predictions in the short, medium and long terms. (author)
NUMERICAL MODELING OF HARDENING OF UNINTERRUPTEDLY-CASTED BRONZE CASTING
Directory of Open Access Journals (Sweden)
E. I. Marukovich
2009-01-01
Full Text Available The three-dimensional numerical model for calculation of thermal fields during solidification of continuously casted bronze casting is developed. Coefficients of heat transfer on borders of calculation areas on the basis of the solution of inverse heat transfer conduction problem are determined. The analysis of thermal fields, depending on loop variables of drawing and the sizes of not cooled zone of crystallizer is curried out.
Numerical modelling of so-called secondary ultrasonic echoes
International Nuclear Information System (INIS)
Langenberg, K.J.; Fellinger, P.; Hofmann, C.
1994-01-01
The formation of secondary ultrasonic echoes is discussed for a particularly simple testing situation. This discussion is based upon the intuitive visualization of elastic wave propagation as obtained with the numerical EFIT-Code (Elastodynamic Finite Integration Technique). The resulting travel times for the econdary echoes contain well-defined limits as they originate from the simple model of grazing incidence plane longitudinal wave mode conversion. (orig.) [de
Numerical methods for modeling photonic-crystal VCSELs
DEFF Research Database (Denmark)
Dems, Maciej; Chung, Il-Sug; Nyakas, Peter
2010-01-01
We show comparison of four different numerical methods for simulating Photonic-Crystal (PC) VCSELs. We present the theoretical basis behind each method and analyze the differences by studying a benchmark VCSEL structure, where the PC structure penetrates all VCSEL layers, the entire top-mirror DBR...... to the effective index method. The simulation results elucidate the strength and weaknesses of the analyzed methods; and outline the limits of applicability of the different models....
Numerical Modeling of a Wave Energy Point Absorber
DEFF Research Database (Denmark)
Hernandez, Lorenzo Banos; Frigaard, Peter; Kirkegaard, Poul Henning
2009-01-01
The present study deals with numerical modelling of the Wave Star Energy WSE device. Hereby, linear potential theory is applied via a BEM code on the wave hydrodynamics exciting the floaters. Time and frequency domain solutions of the floater response are determined for regular and irregular seas....... Furthermore, these results are used to estimate the power and the energy absorbed by a single oscillating floater. Finally, a latching control strategy is analysed in open-loop configuration for energy maximization....
Modelling of multidimensional quantum systems by the numerical functional integration
International Nuclear Information System (INIS)
Lobanov, Yu.Yu.; Zhidkov, E.P.
1990-01-01
The employment of the numerical functional integration for the description of multidimensional systems in quantum and statistical physics is considered. For the multiple functional integrals with respect to Gaussian measures in the full separable metric spaces the new approximation formulas exact on a class of polynomial functionals of a given summary degree are constructed. The use of the formulas is demonstrated on example of computation of the Green function and the ground state energy in multidimensional Calogero model. 15 refs.; 2 tabs
Numerical modeling of bubble dynamics in viscoelastic media with relaxation
Warnez, M. T.; Johnsen, E.
2015-06-01
Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical bubble dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller-Miksis equation with full thermal effects (inside and outside the bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin-Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate bubble dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time.
Numerical equilibrium analysis for structured consumer resource models.
de Roos, A M; Diekmann, O; Getto, P; Kirkilionis, M A
2010-02-01
In this paper, we present methods for a numerical equilibrium and stability analysis for models of a size structured population competing for an unstructured resource. We concentrate on cases where two model parameters are free, and thus existence boundaries for equilibria and stability boundaries can be defined in the (two-parameter) plane. We numerically trace these implicitly defined curves using alternatingly tangent prediction and Newton correction. Evaluation of the maps defining the curves involves integration over individual size and individual survival probability (and their derivatives) as functions of individual age. Such ingredients are often defined as solutions of ODE, i.e., in general only implicitly. In our case, the right-hand sides of these ODE feature discontinuities that are caused by an abrupt change of behavior at the size where juveniles are assumed to turn adult. So, we combine the numerical solution of these ODE with curve tracing methods. We have implemented the algorithms for "Daphnia consuming algae" models in C-code. The results obtained by way of this implementation are shown in the form of graphs.
Numerical solution of High-kappa model of superconductivity
Energy Technology Data Exchange (ETDEWEB)
Karamikhova, R. [Univ. of Texas, Arlington, TX (United States)
1996-12-31
We present formulation and finite element approximations of High-kappa model of superconductivity which is valid in the high {kappa}, high magnetic field setting and accounts for applied magnetic field and current. Major part of this work deals with steady-state and dynamic computational experiments which illustrate our theoretical results numerically. In our experiments we use Galerkin discretization in space along with Backward-Euler and Crank-Nicolson schemes in time. We show that for moderate values of {kappa}, steady states of the model system, computed using the High-kappa model, are virtually identical with results computed using the full Ginzburg-Landau (G-L) equations. We illustrate numerically optimal rates of convergence in space and time for the L{sup 2} and H{sup 1} norms of the error in the High-kappa solution. Finally, our numerical approximations demonstrate some well-known experimentally observed properties of high-temperature superconductors, such as appearance of vortices, effects of increasing the applied magnetic field and the sample size, and the effect of applied constant current.
ASSIMILATION OF DOPPLER RADAR DATA INTO NUMERICAL WEATHER MODELS
Energy Technology Data Exchange (ETDEWEB)
Chiswell, S.; Buckley, R.
2009-01-15
During the year 2008, the United States National Weather Service (NWS) completed an eight fold increase in sampling capability for weather radars to 250 m resolution. This increase is expected to improve warning lead times by detecting small scale features sooner with increased reliability; however, current NWS operational model domains utilize grid spacing an order of magnitude larger than the radar data resolution, and therefore the added resolution of radar data is not fully exploited. The assimilation of radar reflectivity and velocity data into high resolution numerical weather model forecasts where grid spacing is comparable to the radar data resolution was investigated under a Laboratory Directed Research and Development (LDRD) 'quick hit' grant to determine the impact of improved data resolution on model predictions with specific initial proof of concept application to daily Savannah River Site operations and emergency response. Development of software to process NWS radar reflectivity and radial velocity data was undertaken for assimilation of observations into numerical models. Data values within the radar data volume undergo automated quality control (QC) analysis routines developed in support of this project to eliminate empty/missing data points, decrease anomalous propagation values, and determine error thresholds by utilizing the calculated variances among data values. The Weather Research and Forecasting model (WRF) three dimensional variational data assimilation package (WRF-3DVAR) was used to incorporate the QC'ed radar data into input and boundary conditions. The lack of observational data in the vicinity of SRS available to NWS operational models signifies an important data void where radar observations can provide significant input. These observations greatly enhance the knowledge of storm structures and the environmental conditions which influence their development. As the increase in computational power and availability has
Interaction of tide and salinity barrier: Limitation of numerical model
Directory of Open Access Journals (Sweden)
Suphat Vongvisessomjai1
2008-07-01
Full Text Available Nowadays, the study of interaction of the tide and the salinity barrier in an estuarine area is usually accomplished vianumerical modeling, due to the speed and convenience of modern computers. However, numerical models provide littleinsight with respect to the fundamental physical mechanisms involved. In this study, it is found that all existing numericalmodels work satisfactorily when the barrier is located at some distance far from upstream and downstream boundary conditions.Results are considerably underestimate reality when the barrier is located near the downstream boundary, usually theriver mouth. Meanwhile, this analytical model provides satisfactory output for all scenarios. The main problem of thenumerical model is that the effects of barrier construction in creation of reflected tide are neglected when specifying thedownstream boundary conditions; the use of the boundary condition before construction of the barrier which are significantlydifferent from those after the barrier construction would result in an error outputs. Future numerical models shouldattempt to account for this deficiency; otherwise, using this analytical model is another choice.
Numerical modeling of flow boiling instabilities using TRACE
International Nuclear Information System (INIS)
Kommer, Eric M.
2015-01-01
Highlights: • TRACE was used to realistically model boiling instabilities in single and parallel channel configurations. • Model parameters were chosen to exactly mimic other author’s work in order to provide for direct comparison of results. • Flow stability maps generated by the model show unstable flow at operating points similar to other authors. • The method of adjudicating when a flow is “unstable” is critical in this type of numerical study. - Abstract: Dynamic flow instabilities in two-phase systems are a vitally important area of study due to their effects on a great number of industrial applications, including heat exchangers in nuclear power plants. Several next generation nuclear reactor designs incorporate once through steam generators which will exhibit boiling flow instabilities if not properly designed or when operated outside design limits. A number of numerical thermal hydraulic codes attempt to model instabilities for initial design and for use in accident analysis. TRACE, the Nuclear Regulatory Commission’s newest thermal hydraulic code is used in this study to investigate flow instabilities in both single and dual parallel channel configurations. The model parameters are selected as to replicate other investigators’ experimental and numerical work in order to provide easy comparison. Particular attention is paid to the similarities between analysis using TRACE Version 5.0 and RELAP5/MOD3.3. Comparison of results is accomplished via flow stability maps non-dimensionalized via the phase change and subcooling numbers. Results of this study show that TRACE does indeed model two phase flow instabilities, with the transient response closely mimicking that seen in experimental studies. When compared to flow stability maps generated using RELAP, TRACE shows similar results with differences likely due to the somewhat qualitative criteria used by various authors to determine when the flow is truly unstable
Numerical modeling of hypolimnetic oxygenation by electrolysis of water
Directory of Open Access Journals (Sweden)
Jaćimović Nenad M.
2017-01-01
Full Text Available The paper presents a novel method for hypolimnetic oxygenation by electrolysis of water. The performance of the method is investigated by the laboratory and the field experiment. The laboratory experiment is conducted in a 90 L vessel, while the field experiment is conducted at the lake Biwa in Japan. In order to provide a better insight into involved processes, a numerical model for simulation of bubble flow is developed with consideration of gas compressibility and oxygen dissolution. The model simultaneously solves 3-D volume averaged two-fluid governing equations. Developed model is firstly verified by simulation of bubble flow experiments, reported in the literature, where good qualitative agreement between measured and simulated results is observed. In the second part, the model is applied for simulation of conducted water electrolysis experiments. The model reproduced the observed oxygen concentration dynamics reasonably well. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 37009
Numerical modeling of a cryogenic fluid within a fuel tank
Greer, Donald S.
1994-01-01
The computational method developed to study the cryogenic fluid characteristics inside a fuel tank in a hypersonic aircraft is presented. The model simulates a rapid draining of the tank by modeling the ullage vapor and the cryogenic liquid with a moving interface. A mathematical transformation was developed and applied to the Navier-Stokes equations to account for the moving interface. The formulation of the numerical method is a transient hybrid explicit-implicit technique where the pressure term in the momentum equations is approximated to first order in time by combining the continuity equation with an ideal equation of state.
Development of Numerical Grids for UZ Flow and Transport Modeling
International Nuclear Information System (INIS)
P. Dobson
2003-01-01
This Scientific Analysis report describes the methods used to develop numerical grids of the unsaturated hydrogeologic system beneath Yucca Mountain. Numerical grid generation is an integral part of the development of the Unsaturated Zone Flow and Transport Model (UZ Model), a complex, three-dimensional (3-D) model of Yucca Mountain. This revision incorporates changes made to both the geologic framework model and the proposed repository layout. The resulting numerical grids, developed using current geologic, hydrogeologic, and mineralogic data, provide the necessary framework to: (1) develop calibrated hydrogeologic property sets and flow fields, (2) test conceptual hypotheses of flow and transport, and (3) predict flow and transport behavior under a variety of climatic and thermal-loading conditions. The technical scope, content, and management of this Scientific Analysis report was initially controlled by the planning document, ''Technical Work Plan (TWP) for: Unsaturated Zone Sections of License Application Chapters 8 and 12'' (BSC 2002 [159051], Section 1.6.4). This TWP was later superseded by ''Technical Work Plan for: Performance Assessment Unsaturated Zone'' (BSC 2002 [160819]), which contains the Data Qualification Plan used to qualify the DTN: MO0212GWLSSPAX.000 [161271] (See Attachment IV). Grids generated and documented in this report supersede those documented in previous versions of this report (BSC 2001 [159356]). The constraints, assumptions, and limitations associated with this report are discussed in the appropriate sections that follow. There were no deviations from the TWP scope of work in this report. Two software packages not listed in Table IV-2 of the TWP (BSC 2002 [159051]), ARCINFO V7.2.1 (CRWMS M and O 2000 [157019]; USGS 2000 [148304]) and 2kgrid8.for V1.0 (LBNL 2002 [154787]), were utilized in the development of the numerical grids; the use of additional software is accounted for in the TWP (BSC 2002 [159051], Section 13). The use of
Numerical model of operation of the Langmuir probe under intermediate pressure
International Nuclear Information System (INIS)
Dudin, S.V.
1996-01-01
The technique of a Langmuir probe is known reasonably well. However, despite plenty of work devoted to calculation of currents on the probe inserted into plasma, a theory does not at present exist which would allow calculation of plasma parameters at any size of the probe and pressure of the working gas. While the theory of a probe in absence of collisions is developed rather in detail by Bernstain and Rabinovich, Laframboise, Allen, and others, there is no rigorous theory which describes a probe under high pressure of a gas. As for intermediate pressure, the theories are absent. Solution of the problem is in this case considerably complicated because of non-local dependence of density of charged particles on potential or electric field strength that means unusability of hydrodynamic approach and necessity of application of the kinetic theory. To fill in this gap the author has developed a numerical model of ion kinetics in a near-boundary layer of a Langmuir probe, inserted into a weakly-ionized gas-discharge plasma, in a range of intermediate pressure of a neutral gas as well as at any ratio between thickness of the layer of space charge and radius of the probe. On the base of results of modeling, practical technique of processing of pore characteristics at intermediate pressure is developed: (i) a technique of calculation of density of ions; (2) a technique of division of a probe current on electron and ion part
International Nuclear Information System (INIS)
Li Shun; Zhang Sijiong
2014-01-01
A numerical model is presented to simulate the influence function of deformable mirror actuators. The numerical model is formed by Bessel Fourier orthogonal functions, which are constituted of Bessel orthogonal functions and a Fourier basis. A detailed comparison is presented between the new Bessel Fourier model, the Zernike model, the Gaussian influence function and the modified Gaussian influence function. Numerical experiments indicate that the new numerical model is easy to use and more accurate compared with other numerical models. The new numerical model can be used for describing deformable mirror performances and numerical simulations of adaptive optics systems. (research papers)
Benchmark problems for numerical implementations of phase field models
International Nuclear Information System (INIS)
Jokisaari, A. M.; Voorhees, P. W.; Guyer, J. E.; Warren, J.; Heinonen, O. G.
2016-01-01
Here, we present the first set of benchmark problems for phase field models that are being developed by the Center for Hierarchical Materials Design (CHiMaD) and the National Institute of Standards and Technology (NIST). While many scientific research areas use a limited set of well-established software, the growing phase field community continues to develop a wide variety of codes and lacks benchmark problems to consistently evaluate the numerical performance of new implementations. Phase field modeling has become significantly more popular as computational power has increased and is now becoming mainstream, driving the need for benchmark problems to validate and verify new implementations. We follow the example set by the micromagnetics community to develop an evolving set of benchmark problems that test the usability, computational resources, numerical capabilities and physical scope of phase field simulation codes. In this paper, we propose two benchmark problems that cover the physics of solute diffusion and growth and coarsening of a second phase via a simple spinodal decomposition model and a more complex Ostwald ripening model. We demonstrate the utility of benchmark problems by comparing the results of simulations performed with two different adaptive time stepping techniques, and we discuss the needs of future benchmark problems. The development of benchmark problems will enable the results of quantitative phase field models to be confidently incorporated into integrated computational materials science and engineering (ICME), an important goal of the Materials Genome Initiative.
A simplified model for TIG-dressing numerical simulation
Ferro, P.; Berto, F.; James, M. N.
2017-04-01
Irrespective of the mechanical properties of the alloy to be welded, the fatigue strength of welded joints is primarily controlled by the stress concentration associated with the weld toe or weld root. In order to reduce the effects of such notch defects in welds, which are influenced by tensile properties of the alloy, post-weld improvement techniques have been developed. The two most commonly used techniques are weld toe grinding and TIG dressing, which are intended to both remove toe defects such as non-metallic intrusions and to re-profile the weld toe region to give a lower stress concentration. In the case of TIG dressing the weld toe is re-melted to provide a smoother transition between the plate and the weld crown and to beneficially modify the residual stress redistribution. Assessing the changes to weld stress state arising from TIG-dressing is most easily accomplished through a complex numerical simulation that requires coupled thermo-fluid dynamics and solid mechanics. However, this can be expensive in terms of computational cost and time needed to reach a solution. The present paper therefore proposes a simplified numerical model that overcomes such drawbacks and which simulates the remelted toe region by means of the activation and deactivation of elements in the numerical model.
Numerical Cerebrospinal System Modeling in Fluid-Structure Interaction.
Garnotel, Simon; Salmon, Stéphanie; Balédent, Olivier
2018-01-01
Cerebrospinal fluid (CSF) stroke volume in the aqueduct is widely used to evaluate CSF dynamics disorders. In a healthy population, aqueduct stroke volume represents around 10% of the spinal stroke volume while intracranial subarachnoid space stroke volume represents 90%. The amplitude of the CSF oscillations through the different compartments of the cerebrospinal system is a function of the geometry and the compliances of each compartment, but we suspect that it could also be impacted be the cardiac cycle frequency. To study this CSF distribution, we have developed a numerical model of the cerebrospinal system taking into account cerebral ventricles, intracranial subarachnoid spaces, spinal canal and brain tissue in fluid-structure interactions. A numerical fluid-structure interaction model is implemented using a finite-element method library to model the cerebrospinal system and its interaction with the brain based on fluid mechanics equations and linear elasticity equations coupled in a monolithic formulation. The model geometry, simplified in a first approach, is designed in accordance with realistic volume ratios of the different compartments: a thin tube is used to mimic the high flow resistance of the aqueduct. CSF velocity and pressure and brain displacements are obtained as simulation results, and CSF flow and stroke volume are calculated from these results. Simulation results show a significant variability of aqueduct stroke volume and intracranial subarachnoid space stroke volume in the physiological range of cardiac frequencies. Fluid-structure interactions are numerous in the cerebrospinal system and difficult to understand in the rigid skull. The presented model highlights significant variations of stroke volumes under cardiac frequency variations only.
Chrystal and Proudman resonances simulated with three numerical models
Bubalo, Maja; Janeković, Ivica; Orlić, Mirko
2018-05-01
The aim of this work was to study Chrystal and Proudman resonances in a simple closed basin and to explore and compare how well the two resonant mechanisms are reproduced with different, nowadays widely used, numerical ocean models. The test case was based on air pressure disturbances of two commonly used shapes (a sinusoidal and a boxcar), having various wave lengths, and propagating at different speeds. Our test domain was a closed rectangular basin, 300 km long with a uniform depth of 50 m, with the theoretical analytical solution available for benchmark. In total, 2250 simulations were performed for each of the three different numerical models: ADCIRC, SCHISM and ROMS. During each of the simulations, we recorded water level anomalies and computed the integral of the energy density spectrum for a number of points distributed along the basin. We have successfully documented the transition from Proudman to Chrystal resonance that occurs for a sinusoidal air pressure disturbance having a wavelength between one and two basin lengths. An inter-model comparison of the results shows that different models represent the two resonant phenomena in a slightly different way. For Chrystal resonance, all the models showed similar behavior; however, ADCIRC model providing slightly higher values of the mean resonant period than the other two models. In the case of Proudman resonance, the most consistent results, closest to the analytical solution, were obtained using ROMS model, which reproduced the mean resonant speed equal to 22.00 m/s— i.e., close to the theoretical value of 22.15 m/s. ADCIRC and SCHISM models showed small deviations from that value, with the mean speed being slightly lower—21.97 m/s (ADCIRC) and 21.93 m/s (SCHISM). The findings may seem small but could play an important role when resonance is a crucial process producing enhancing effects by two orders of magnitude (i.e., meteotsunamis).
Numerical modelling of multimode fibre-optic communication lines
Energy Technology Data Exchange (ETDEWEB)
Sidelnikov, O S; Fedoruk, M P [Novosibirsk State University, Novosibirsk (Russian Federation); Sygletos, S; Ferreira, F [Aston University, England, Birmingham, B4 7ET (United Kingdom)
2016-01-31
The results of numerical modelling of nonlinear propagation of an optical signal in multimode fibres with a small differential group delay are presented. It is found that the dependence of the error vector magnitude (EVM) on the differential group delay can be reduced by increasing the number of ADC samples per symbol in the numerical implementation of the differential group delay compensation algorithm in the receiver. The possibility of using multimode fibres with a small differential group delay for data transmission in modern digital communication systems is demonstrated. It is shown that with increasing number of modes the strong coupling regime provides a lower EVM level than the weak coupling one. (fibre-optic communication lines)
Induction and direct resistance heating theory and numerical modeling
Lupi, Sergio; Aliferov, Aleksandr
2015-01-01
This book offers broad, detailed coverage of theoretical developments in induction and direct resistance heating and presents new material on the solution of problems in the application of such heating. The physical basis of induction and conduction heating processes is explained, and electromagnetic phenomena in direct resistance and induction heating of flat workpieces and cylindrical bodies are examined in depth. The calculation of electrical and energetic characteristics of induction and conduction heating systems is then thoroughly reviewed. The final two chapters consider analytical solutions and numerical modeling of problems in the application of induction and direct resistance heating, providing industrial engineers with the knowledge needed in order to use numerical tools in the modern design of installations. Other engineers, scientists, and technologists will find the book to be an invaluable reference that will assist in the efficient utilization of electrical energy.
Numerical methods for the Lévy LIBOR model
DEFF Research Database (Denmark)
Papapantoleon, Antonis; Skovmand, David
2010-01-01
but the methods are generally slow. We propose an alternative approximation scheme based on Picard iterations. Our approach is similar in accuracy to the full numerical solution, but with the feature that each rate is, unlike the standard method, evolved independently of the other rates in the term structure....... This enables simultaneous calculation of derivative prices of different maturities using parallel computing. We include numerical illustrations of the accuracy and speed of our method pricing caplets.......The aim of this work is to provide fast and accurate approximation schemes for the Monte-Carlo pricing of derivatives in the L\\'evy LIBOR model of Eberlein and \\"Ozkan (2005). Standard methods can be applied to solve the stochastic differential equations of the successive LIBOR rates...
Numerical Methods for the Lévy LIBOR Model
DEFF Research Database (Denmark)
Papapantoleon, Antonis; Skovmand, David
are generally slow. We propose an alternative approximation scheme based on Picard iterations. Our approach is similar in accuracy to the full numerical solution, but with the feature that each rate is, unlike the standard method, evolved independently of the other rates in the term structure. This enables...... simultaneous calculation of derivative prices of different maturities using parallel computing. We include numerical illustrations of the accuracy and speed of our method pricing caplets.......The aim of this work is to provide fast and accurate approximation schemes for the Monte-Carlo pricing of derivatives in the Lévy LIBOR model of Eberlein and Özkan (2005). Standard methods can be applied to solve the stochastic differential equations of the successive LIBOR rates but the methods...
Numerical modelling of extreme waves by Smoothed Particle Hydrodynamics
Directory of Open Access Journals (Sweden)
M. H. Dao
2011-02-01
Full Text Available The impact of extreme/rogue waves can lead to serious damage of vessels as well as marine and coastal structures. Such extreme waves in deep water are characterized by steep wave fronts and an energetic wave crest. The process of wave breaking is highly complex and, apart from the general knowledge that impact loadings are highly impulsive, the dynamics of the breaking and impact are still poorly understood. Using an advanced numerical method, the Smoothed Particle Hydrodynamics enhanced with parallel computing is able to reproduce well the extreme waves and their breaking process. Once the waves and their breaking process are modelled successfully, the dynamics of the breaking and the characteristics of their impact on offshore structures could be studied. The computational methodology and numerical results are presented in this paper.
Mathematical modelling and numerical simulation of oil pollution problems
2015-01-01
Written by outstanding experts in the fields of marine engineering, atmospheric physics and chemistry, fluid dynamics and applied mathematics, the contributions in this book cover a wide range of subjects, from pure mathematics to real-world applications in the oil spill engineering business. Offering a truly interdisciplinary approach, the authors present both mathematical models and state-of-the-art numerical methods for adequately solving the partial differential equations involved, as well as highly practical experiments involving actual cases of ocean oil pollution. It is indispensable that different disciplines of mathematics, like analysis and numerics, together with physics, biology, fluid dynamics, environmental engineering and marine science, join forces to solve today’s oil pollution problems. The book will be of great interest to researchers and graduate students in the environmental sciences, mathematics and physics, showing the broad range of techniques needed in order to solve these poll...
NATO Advanced Study Institute on Advanced Physical Oceanographic Numerical Modelling
1986-01-01
This book is a direct result of the NATO Advanced Study Institute held in Banyuls-sur-mer, France, June 1985. The Institute had the same title as this book. It was held at Laboratoire Arago. Eighty lecturers and students from almost all NATO countries attended. The purpose was to review the state of the art of physical oceanographic numerical modelling including the parameterization of physical processes. This book represents a cross-section of the lectures presented at the ASI. It covers elementary mathematical aspects through large scale practical aspects of ocean circulation calculations. It does not encompass every facet of the science of oceanographic modelling. We have, however, captured most of the essence of mesoscale and large-scale ocean modelling for blue water and shallow seas. There have been considerable advances in modelling coastal circulation which are not included. The methods section does not include important material on phase and group velocity errors, selection of grid structures, advanc...
A numerical model for buoyant oil jets and smoke plumes
International Nuclear Information System (INIS)
Zheng, L.; Yapa, P. D.
1997-01-01
Development of a 3-D numerical model to simulate the behaviour of buoyant oil jets from underwater accidents and smoke plumes from oil burning was described. These jets/plumes can be oil-in-water, oil/gas mixture in water, gas in water, or gas in air. The ambient can have a 3-D flow structure, and spatially/temporally varying flow conditions. The model is based on the Lagrangian integral technique. The model formulation of oil jet includes the diffusion and dissolution of oil from the jet to the ambient environment. It is suitable to simulate well blowout accidents that can occur in deep waters, including that of the North Sea. The model has been thoroughly tested against a variety of data, including data from both laboratory and field experiments. In all cases the simulation data compared very well with experimental data. 26 refs., 10 figs
Automated smoother for the numerical decoupling of dynamics models.
Vilela, Marco; Borges, Carlos C H; Vinga, Susana; Vasconcelos, Ana Tereza R; Santos, Helena; Voit, Eberhard O; Almeida, Jonas S
2007-08-21
Structure identification of dynamic models for complex biological systems is the cornerstone of their reverse engineering. Biochemical Systems Theory (BST) offers a particularly convenient solution because its parameters are kinetic-order coefficients which directly identify the topology of the underlying network of processes. We have previously proposed a numerical decoupling procedure that allows the identification of multivariate dynamic models of complex biological processes. While described here within the context of BST, this procedure has a general applicability to signal extraction. Our original implementation relied on artificial neural networks (ANN), which caused slight, undesirable bias during the smoothing of the time courses. As an alternative, we propose here an adaptation of the Whittaker's smoother and demonstrate its role within a robust, fully automated structure identification procedure. In this report we propose a robust, fully automated solution for signal extraction from time series, which is the prerequisite for the efficient reverse engineering of biological systems models. The Whittaker's smoother is reformulated within the context of information theory and extended by the development of adaptive signal segmentation to account for heterogeneous noise structures. The resulting procedure can be used on arbitrary time series with a nonstationary noise process; it is illustrated here with metabolic profiles obtained from in-vivo NMR experiments. The smoothed solution that is free of parametric bias permits differentiation, which is crucial for the numerical decoupling of systems of differential equations. The method is applicable in signal extraction from time series with nonstationary noise structure and can be applied in the numerical decoupling of system of differential equations into algebraic equations, and thus constitutes a rather general tool for the reverse engineering of mechanistic model descriptions from multivariate experimental
Numerical modeling of hydrodynamic in southwestern Johor, Malaysia
Jusoh, Wan Hasliza Wan; Tangang, Fredolin; Juneng, Liew; Hamid, Mohd. Radzi Abdul
2014-09-01
Tanjung Piai located at the southwest of Johor, Malaysia faces severe erosion since a few decades ago. Considering the condition in this particular area, understanding of its hydrodynamic behaviour should be clearly explained. Thus, a numerical modelling has been applied in this study in order to investigate the hydrodynamic of current flow along the study area. Hydrodynamic study was carried out by applying a numerical modelling of MIKE 21 software based on flexible mesh grids. The model generally described the current flow pattern in the study area corresponding to the several flows from surrounding water regime which are Malacca Strait, Singapore Strait and Java Sea. The interaction of various water flows in the area of Tanjung Piai which is located in the middle part of the meeting of the currents to have a very complicated hydrodynamic conditions. The study area generally experienced two tidal phase in a day as the water flows is greatly influenced by the adjacent water flow from Malacca and Singapore Straits. During first tidal cycle, the most dominant flow is influenced by a single water flow which is Malacca Strait for both ebbing and flooding event. The current velocity was generally higher during this first tidal phase particularly at the tips of Tanjung Piai where severe erosion is spotted. However, the second tidal phase gives different stress to the study area as the flow is relatively dominated by both Malacca and Singapore Straits. During this phase, the meeting of current from both straits can be discovered near to the Tanjung Piai as this occurrence makes relatively slower current velocity around the study area. Basically, the numerical modelling result in this study can be considered as basic information in describing the condition of study area as it would be very useful for extensive study especially the study of sediment transport and morphological processes in the coastal area.
Multiphysics Numerical Modeling of a Fin and Tube Heat Exchanger
DEFF Research Database (Denmark)
Singh, Shobhana; Sørensen, Kim; Condra, Thomas Joseph
2015-01-01
In the present research work, a modeling effort to predict the performance of a liquid-gas type fin and tube heat exchanger design is made. Three dimensional (3D) steady state numerical model is developed using commercial software COMSOL Multiphysics based on finite element method (FEM......). For the purposes here, only gas flowing over the fin side is simulated assuming constant inner tube wall temperature. The study couples conjugate heat transfer mechanism with turbulent flow in order to describe the temperature and velocity profile. In addition, performance characteristics of the heat exchanger...... design in terms of heat transfer and pressure loss are determined by parameters such as overall heat transfer coefficient, Colburn j-factor, flow resistance factor, and efficiency index. The model provides useful insights necessary for optimization of heat exchanger design....
Rigorous simulations of a helical core fiber by the use of transformation optics formalism.
Napiorkowski, Maciej; Urbanczyk, Waclaw
2014-09-22
We report for the first time on rigorous numerical simulations of a helical-core fiber by using a full vectorial method based on the transformation optics formalism. We modeled the dependence of circular birefringence of the fundamental mode on the helix pitch and analyzed the effect of a birefringence increase caused by the mode displacement induced by a core twist. Furthermore, we analyzed the complex field evolution versus the helix pitch in the first order modes, including polarization and intensity distribution. Finally, we show that the use of the rigorous vectorial method allows to better predict the confinement loss of the guided modes compared to approximate methods based on equivalent in-plane bending models.
Numerical cell model investigating cellular carbon fluxes in Emiliania huxleyi.
Holtz, Lena-Maria; Wolf-Gladrow, Dieter; Thoms, Silke
2015-01-07
Coccolithophores play a crucial role in the marine carbon cycle and thus it is interesting to know how they will respond to climate change. After several decades of research the interplay between intracellular processes and the marine carbonate system is still not well understood. On the basis of experimental findings given in literature, a numerical cell model is developed that describes inorganic carbon fluxes between seawater and the intracellular sites of calcite precipitation and photosynthetic carbon fixation. The implemented cell model consists of four compartments, for each of which the carbonate system is resolved individually. The four compartments are connected to each other via H(+), CO2, and HCO3(-) fluxes across the compartment-confining membranes. For CO2 accumulation around RubisCO, an energy-efficient carbon concentrating mechanism is proposed that relies on diffusive CO2 uptake. At low external CO2 concentrations and high light intensities, CO2 diffusion does not suffice to cover the carbon demand of photosynthesis and an additional uptake of external HCO3(-) becomes essential. The model is constrained by data of Emiliania huxleyi, the numerically most abundant coccolithophore species in the present-day ocean. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.
Modelling and numerical simulation of liquid-vapor phase transitions
International Nuclear Information System (INIS)
Caro, F.
2004-11-01
This work deals with the modelling and numerical simulation of liquid-vapor phase transition phenomena. The study is divided into two part: first we investigate phase transition phenomena with a Van Der Waals equation of state (non monotonic equation of state), then we adopt an alternative approach with two equations of state. In the first part, we study the classical viscous criteria for selecting weak solutions of the system used when the equation of state is non monotonic. Those criteria do not select physical solutions and therefore we focus a more recent criterion: the visco-capillary criterion. We use this criterion to exactly solve the Riemann problem (which imposes solving an algebraic scalar non linear equation). Unfortunately, this step is quite costly in term of CPU which prevent from using this method as a ground for building Godunov solvers. That is why we propose an alternative approach two equations of state. Using the least action principle, we propose a phase changing two-phase flow model which is based on the second thermodynamic principle. We shall then describe two equilibrium submodels issued from the relaxations processes when instantaneous equilibrium is assumed. Despite the weak hyperbolicity of the last sub-model, we propose stable numerical schemes based on a two-step strategy involving a convective step followed by a relaxation step. We show the ability of the system to simulate vapor bubbles nucleation. (author)
Numerical solution of a model for a superconductor field problem
International Nuclear Information System (INIS)
Alsop, L.E.; Goodman, A.S.; Gustavson, F.G.; Miranker, W.L.
1979-01-01
A model of a magnetic field problem occurring in connection with Josephson junction devices is derived, and numerical solutions are obtained. The model is of mathematical interest, because the magnetic vector potential satisfies inhomogeneous Helmholtz equations in part of the region, i.e., the superconductors, and the Laplace equation elsewhere. Moreover, the inhomogeneities are the guage constants for the potential, which are different for each superconductor, and their magnitudes are proportional to the currents flowing in the superconductors. These constants are directly related to the self and mutual inductances of the superconducting elements in the device. The numerical solution is obtained by the iterative use of a fast Poisson solver. Chebyshev acceleration is used to reduce the number of iterations required to obtain a solution. A typical problem involves solving 100,000 simultaneous equations, which the algorithm used with this model does in 20 iterations, requiring three minutes of CPU time on an IBM VM/370/168. Excellent agreement is obtained between calculated and observed values for the inductances
Black-hole kicks from numerical-relativity surrogate models
Gerosa, Davide; Hébert, François; Stein, Leo C.
2018-05-01
Binary black holes radiate linear momentum in gravitational waves as they merge. Recoils imparted to the black-hole remnant can reach thousands of km /s , thus ejecting black holes from their host galaxies. We exploit recent advances in gravitational waveform modeling to quickly and reliably extract recoils imparted to generic, precessing, black-hole binaries. Our procedure uses a numerical-relativity surrogate model to obtain the gravitational waveform given a set of binary parameters; then, from this waveform we directly integrate the gravitational-wave linear momentum flux. This entirely bypasses the need for fitting formulas which are typically used to model black-hole recoils in astrophysical contexts. We provide a thorough exploration of the black-hole kick phenomenology in the parameter space, summarizing and extending previous numerical results on the topic. Our extraction procedure is made publicly available as a module for the Python programming language named surrkick. Kick evaluations take ˜0.1 s on a standard off-the-shelf machine, thus making our code ideal to be ported to large-scale astrophysical studies.
Determination of Volumetric Losses in Hydrodynamic Pump Using Numerical Modelling
Directory of Open Access Journals (Sweden)
Lukáš ZAVADIL
2012-06-01
Full Text Available This paper deals with the numerical modelling of the flow in the single-stage centrifugal pump. The main objective is to determine leakage losses through annular seals at the suction side of the pump. Leakage through a shaft seal is not included in the simulation. The amount of liquid that circulates from the impeller discharge back to suction of the pump is determined in dependence on the flow rate. Losses in the pump are further discussed as well as the possibility of their prediction.
Experimental and numerical modeling of sulfur plugging in carbonate reservoirs
Energy Technology Data Exchange (ETDEWEB)
Abou-Kassem, J.H. [Chemical and Petroleum Engineering Department, UAE University, PO Box 17555, Al-Ain (United Arab Emirates)
2000-05-01
Sour gas, mainly in the form of hydrogen sulfide, is produced in large amounts from many oil and gas reservoirs in the United Arab Emirates. In addition to creating problems in production lines, the precipitation of elemental sulfur in vicinity of the wellbore is often reported to cause wellbore damage. While there have been several studies performed on the role of solid deposition in gas reservoirs, the role of sulfur deposition in oil reservoirs has not been investigated. This paper presents experimental results along with a comprehensive wellbore model that predicts sulfur precipitation as well as plugging. Two separate sets of experiments, one for a gas phase system and another for a crude oil system, were conducted to investigate the deposition of elemental sulfur in (linear) carbonate cores. The gas flow tests were conducted with elemental sulfur being carried with nitrogen through limestone cores. Changes in gas flow rate were monitored while the injection pressure was held constant. A series of experiments generated valuable data for plugging with elemental sulfur. X-ray diffraction tests provided evidence of sulfur deposition along the cores. The oil flow tests were carried out to observe sulfur precipitation and plugging in a carbonate core. The crude oil was de-asphalted before conducting these tests in order to isolate the effect of asphaltene plugging. Significant plugging was observed and was found to be dependent on flow rate and initial sulfur concentration. This information was used in a phenomenological model that was incorporated in the wellbore numerical model. The data for the numerical model were obtained from both test tube and oil flow experiments. By using a phenomenological model, the wellbore plugging was modeled with an excellent match (with experimental results)
Modeling and numerical study of two phase flow
International Nuclear Information System (INIS)
Champmartin, A.
2011-01-01
This thesis describes the modelization and the simulation of two-phase systems composed of droplets moving in a gas. The two phases interact with each other and the type of model to consider directly depends on the type of simulations targeted. In the first part, the two phases are considered as fluid and are described using a mixture model with a drift relation (to be able to follow the relative velocity between the two phases and take into account two velocities), the two-phase flows are assumed at the equilibrium in temperature and pressure. This part of the manuscript consists of the derivation of the equations, writing a numerical scheme associated with this set of equations, a study of this scheme and simulations. A mathematical study of this model (hyperbolicity in a simplified framework, linear stability analysis of the system around a steady state) was conducted in a frame where the gas is assumed baro-tropic. The second part is devoted to the modelization of the effect of inelastic collisions on the particles when the time of the simulation is shorter and the droplets can no longer be seen as a fluid. We introduce a model of inelastic collisions for droplets in a spray, leading to a specific Boltzmann kernel. Then, we build caricatures of this kernel of BGK type, in which the behavior of the first moments of the solution of the Boltzmann equation (that is mass, momentum, directional temperatures, variance of the internal energy) are mimicked. The quality of these caricatures is tested numerically at the end. (author) [fr
Numerical simulation and experimental validation of aircraft ground deicing model
Directory of Open Access Journals (Sweden)
Bin Chen
2016-05-01
Full Text Available Aircraft ground deicing plays an important role of guaranteeing the aircraft safety. In practice, most airports generally use as many deicing fluids as possible to remove the ice, which causes the waste of the deicing fluids and the pollution of the environment. Therefore, the model of aircraft ground deicing should be built to establish the foundation for the subsequent research, such as the optimization of the deicing fluid consumption. In this article, the heat balance of the deicing process is depicted, and the dynamic model of the deicing process is provided based on the analysis of the deicing mechanism. In the dynamic model, the surface temperature of the deicing fluids and the ice thickness are regarded as the state parameters, while the fluid flow rate, the initial temperature, and the injection time of the deicing fluids are treated as control parameters. Ignoring the heat exchange between the deicing fluids and the environment, the simplified model is obtained. The rationality of the simplified model is verified by the numerical simulation and the impacts of the flow rate, the initial temperature and the injection time on the deicing process are investigated. To verify the model, the semi-physical experiment system is established, consisting of the low-constant temperature test chamber, the ice simulation system, the deicing fluid heating and spraying system, the simulated wing, the test sensors, and the computer measure and control system. The actual test data verify the validity of the dynamic model and the accuracy of the simulation analysis.
Numerical modeling of hybrid fiber-reinforced concrete (hyfrc)
International Nuclear Information System (INIS)
Hameed, R.; Turatsinze, A.
2015-01-01
A model for numerical simulation of mechanical response of concrete reinforced with slipping and non slipping metallic fibers in hybrid form is presented in this paper. Constitutive law used to model plain concrete behaviour is based on plasticity and damage theories, and is capable to determine localized crack opening in three dimensional (3-D) systems. Behaviour law used for slipping metallic fibers is formulated based on effective stress carried by these fibers after when concrete matrix is cracked. A continuous approach is proposed to model the effect of addition of non-slipping metallic fibers in plain concrete. This approach considers the constitutive law of concrete matrix with increased fracture energy in tension obtained experimentally in direct tension tests on Fiber Reinforced Concrete (FRC). To simulate the mechanical behaviour of hybrid fiber-reinforced concrete (HyFRC), proposed approaches to model non-slipping metallic fibers and constitutive law of plain concrete and slipping fibers are used simultaneously without any additive equation. All the parameters used by the proposed model have physical meanings and are determined through experiments or drawn from literature. The model was implemented in Finite Element (FE) Code CASTEM and tested on FRC prismatic notched specimens in flexure. Model prediction showed good agreement with experimental results. (author)
Energy Technology Data Exchange (ETDEWEB)
Park, Ju Yeop; In, Wang Kee; Chun, Tae Hyun; Oh, Dong Seok [Korea Atomic Energy Research Institute, Taejeon (Korea)
2000-02-01
The development of orthogonal 2-dimensional numerical code is made. The present code contains 9 kinds of turbulence models that are widely used. They include a standard k-{epsilon} model and 8 kinds of low Reynolds number ones. They also include 6 kinds of numerical schemes including 5 kinds of low order schemes and 1 kind of high order scheme such as QUICK. To verify the present numerical code, pipe flow, channel flow and expansion pipe flow are solved by this code with various options of turbulence models and numerical schemes and the calculated outputs are compared to experimental data. Furthermore, the discretization error that originates from the use of standard k-{epsilon} turbulence model with wall function is much more diminished by introducing a new grid system than a conventional one in the present code. 23 refs., 58 figs., 6 tabs. (Author)
Numerical modeling of coanda effect in a novel propulsive system
Directory of Open Access Journals (Sweden)
S Das
2016-09-01
Full Text Available Coanda effect (adhesion of jet flow over curved surface is fundamental characteristics of jet flow. In the present paper, we carried out numerical simulations to investigate Coanda flow over a curved surface and its application in a newly proposed Propulsive system "A.C.H.E.O.N" (Aerial Coanda High Efficiency Orienting jet Nozzle which supports thrust vectoring. The ACHEON system is presently being proposed for propelling a new V/STOL airplane in European Union. This system is based on cumulative effects of three physical effects such as (1 High speed jet mixing speeds (2 Coanda effect control by electrostatic fields (3 Coanda effect adhesion of an high speed jet to a convex surface. The performance of this nozzle can be enhanced by increasing the jet deflection angle of synthetic jet over the Coanda surface. This newly proposed nozzle has wide range of applications. It can be used in industrial sector such as plasma spray gun and for direct injection in combustion chamber to enhance the efficiency of the combustion chamber. Also, we studied the effect of Dielectric barrier discharge (DBD plasma actuators on A.C.H.E.O.N system. Dielectric barrier discharge (DBD plasma actuators are active control devices for controlling boundary layer and to delay the flow separation over any convex surfaces. Computations were performed under subsonic condition. Two dimensional CFD calculations were carried out using Reynolds averaged Navier stokes equations (RANS. A numerical method based on finite volume formulation (FVM was used. SST k-ω model was considered to model turbulent flow inside nozzle. DBD model was used to model the plasma. Moreover, a body force treatment was devised to model the effect of plasma and its coupling with the fluid. This preliminary result shows that, the presence of plasma near Coanda surface accelerates the flow and delays the separation and enhances the efficiency of the nozzle.
Explosion localization and characterization via infrasound using numerical modeling
Fee, D.; Kim, K.; Iezzi, A. M.; Matoza, R. S.; Jolly, A. D.; De Angelis, S.; Diaz Moreno, A.; Szuberla, C.
2017-12-01
Numerous methods have been applied to locate, detect, and characterize volcanic and anthropogenic explosions using infrasound. Far-field localization techniques typically use back-azimuths from multiple arrays (triangulation) or Reverse Time Migration (RTM, or back-projection). At closer ranges, networks surrounding a source may use Time Difference of Arrival (TDOA), semblance, station-pair double difference, etc. However, at volcanoes and regions with topography or obstructions that block the direct path of sound, recent studies have shown that numerical modeling is necessary to provide an accurate source location. A heterogeneous and moving atmosphere (winds) may also affect the location. The time reversal mirror (TRM) application of Kim et al. (2015) back-propagates the wavefield using a Finite Difference Time Domain (FDTD) algorithm, with the source corresponding to the location of peak convergence. Although it provides high-resolution source localization and can account for complex wave propagation, TRM is computationally expensive and limited to individual events. Here we present a new technique, termed RTM-FDTD, which integrates TRM and FDTD. Travel time and transmission loss information is computed from each station to the entire potential source grid from 3-D Green's functions derived via FDTD. The wave energy is then back-projected and stacked at each grid point, with the maximum corresponding to the likely source. We apply our method to detect and characterize thousands of explosions from Yasur Volcano, Vanuatu and Etna Volcano, Italy, which both provide complex wave propagation and multiple source locations. We compare our results with those from more traditional methods (e.g. semblance), and suggest our method is preferred as it is computationally less expensive than TRM but still integrates numerical modeling. RTM-FDTD could be applied to volcanic other anthropogenic sources at a wide variety of ranges and scenarios. Kim, K., Lees, J.M., 2015. Imaging
Numerical modeling for an electric-field hyperthermia applicator
Wu, Te-Kao; Chou, C. K.; Chan, K. W.; Mcdougall, J.
1993-01-01
Hyperthermia, in conjunction with radiation and chemotherapy for treatment of cancers, is an area of current concern. Experiments have shown that hyperthermia can increase the potency of many chemotherapy drugs and the effectiveness of radiation for treating cancer. A combination of whole body or regional hyperthermia with chemotherapy or radiation should improve treatment results. Conventional methods for inducing whole body hyperthermia, such as exposing a patient in a radiant cabinet or under a hot water blanket, conduct heat very slowly from the skin to the body core. Thus a more efficient system, such as the three-plate electric-field hyperthermia applicator (EHA), is developed. This three-plate EHA has one top plate over and two lower plates beneath the patient. It is driven at 27.12 MHz with 500 Watts through a matching circuit. Using this applicator, a 50 kg pig was successfully heated to 42 C within 45 minutes. However, phantom and animal studies have indicated non-uniform heating near the side of the body. In addition, changes in the size and distance between the electrode plates can affect the heating (or electromagnetic field) pattern. Therefore, numerical models using the method of moments (MOM) or the finite difference time domain (FDTD) technique are developed to optimize the heating pattern of this EHA before it is used for human trials. The accuracy of the numerical modeling has been achieved by the good agreement between the MOM and FDTD results for the three-plate EHA without a biological body. The versatile FDTD technique is then applied to optimize the EHA design with a human body. Both the numerical and measured data in phantom blocks will be presented. The results of this study will be used to design an optimized system for whole body or regional hyperthermia.
Numerical models for prestressing tendons in containment structures
International Nuclear Information System (INIS)
Kwak, Hyo-Gyoung; Kim, Jae Hong
2006-01-01
Two modified stress-strain relations for bonded and unbonded internal tendons are proposed. The proposed relations can simulate the post-cracking behavior and tension stiffening effect in prestressed concrete containment structures. In the case of the bonded tendon, tensile forces between adjacent cracks are transmitted from a bonded tendon to concrete by bond forces. Therefore, the constitutive law of a bonded tendon stiffened by grout needs to be determined from the bond-slip relationship. On the other hand, a stress increase beyond the effective prestress in an unbonded tendon is not section-dependent but member-dependent. It means that the tendon stress unequivocally represents a uniform distribution along the length when the friction loss is excluded. Thus, using a strain reduction factor, the modified stress-strain curve of an unbonded tendon is derived by successive iterations. In advance, the prediction of cracking behavior and ultimate resisting capacity of prestressed concrete containment structures using the introduced numerical models are succeeded, and the need for the consideration of many influencing factors such as the tension stiffening effect, plastic hinge length and modification of stress-strain relation of tendon is emphasized. Finally, the developed numerical models are applied to prestressed concrete containment structures to verify the efficiency and applicability in simulating the structural behavior with bonded and/or unbonded tendons
Numerical modeling of ultrasonic cavitation in ionic liquids
Calvisi, Michael L.; Elder, Ross M.
2017-11-01
Ionic liquids have favorable properties for sonochemistry applications in which the high temperatures and pressures achieved by cavitation bubbles are important drivers of chemical processes. Two different numerical models are presented to simulate ultrasonic cavitation in ionic liquids, each with different capabilities and physical assumptions. A model based on a compressible form of the Rayleigh-Plesset equation (RPE) simulates ultrasonic cavitation of a spherical bubble with a homogeneous interior, incorporating evaporation and condensation at the bubble surface, and temperature-varying thermodynamic properties in the interior. A second, more computationally intensive model of a spherical bubble uses the finite element method (FEM) and accounts for spatial variations in pressure and temperature throughout the flow domain. This model provides insight into heat transfer across the bubble surface and throughout the bubble interior and exterior. Parametric studies are presented for sonochemistry applications involving ionic liquids as a solvent, examining a range of realistic ionic liquid properties and initial conditions to determine their effect on temperature and pressure. Results from the two models are presented for parametric variations including viscosity, thermal conductivity, water content of the ionic liquid solvent, acoustic frequency, and initial bubble pressure. An additional study performed with the FEM model examines thermal penetration into the surrounding ionic liquid during bubble oscillation. The results suggest the prospect of tuning ionic liquid properties for specific applications.
Numerical modeling of the hydrogeological effects of ONKALO in 2009
International Nuclear Information System (INIS)
Raemae, T.
2011-10-01
The underground rock characterization facility ONKALO is currently being excavated in the bedrock of the Olkiluoto Island. The construction work of the ONKALO begun in 2004 and the tunnel will remain open for the whole period of the operation of the planned repository for spent nuclear fuel. The open tunnels cause a disturbance on the local groundwater system. The leakage water flowing into the open tunnels withdraw water from the bedrock and locally alter the natural flow routes. One of the possible consequences of the convergent flow towards the ONKALO is that the highly saline deeper groundwater might be drawn towards the ONKALO, this process is called upconing. The purpose of this work is to estimate the possible upconing of the deep saline waters up to the repository level. A numerical flow and transport simulation is conducted with conservative approach to ensure overestimation of the effects of the ONKALO. In this study a 3D model of the hydrogeological system of the Olkiluoto is used as the basis for numerical flow and transport modeling of the saline groundwater movement in the bedrock of Olkiluoto. The numerical modelling is conducted using the commercial Comsol 3.5a code. The modelled geometry of the ONKALO includes the already excavated ONKALO and the extension according to the layout plan used in this work. The ONKALO and the hydrogeological zones are simplified for this study. In addition the used hydrogeological zones are modelled as 3D blocks with constant thickness of 50 meters. With the used boundary conditions upconing occurs even with the lowest leakage values. The influence of the leakage water is small on the maximum TDS-value at the depth near ONKALO. In this work this phenomenon is explained by the increase in the fresh water infiltration rate as the leakage water is increased, since the low density fresh water is transported more easily downwards than the high density saline water transported upwards towards the ONKALO. Further away from
Monte Carlo Numerical Models for Nuclear Logging Applications
Directory of Open Access Journals (Sweden)
Fusheng Li
2012-06-01
Full Text Available Nuclear logging is one of most important logging services provided by many oil service companies. The main parameters of interest are formation porosity, bulk density, and natural radiation. Other services are also provided from using complex nuclear logging tools, such as formation lithology/mineralogy, etc. Some parameters can be measured by using neutron logging tools and some can only be measured by using a gamma ray tool. To understand the response of nuclear logging tools, the neutron transport/diffusion theory and photon diffusion theory are needed. Unfortunately, for most cases there are no analytical answers if complex tool geometry is involved. For many years, Monte Carlo numerical models have been used by nuclear scientists in the well logging industry to address these challenges. The models have been widely employed in the optimization of nuclear logging tool design, and the development of interpretation methods for nuclear logs. They have also been used to predict the response of nuclear logging systems for forward simulation problems. In this case, the system parameters including geometry, materials and nuclear sources, etc., are pre-defined and the transportation and interactions of nuclear particles (such as neutrons, photons and/or electrons in the regions of interest are simulated according to detailed nuclear physics theory and their nuclear cross-section data (probability of interacting. Then the deposited energies of particles entering the detectors are recorded and tallied and the tool responses to such a scenario are generated. A general-purpose code named Monte Carlo N– Particle (MCNP has been the industry-standard for some time. In this paper, we briefly introduce the fundamental principles of Monte Carlo numerical modeling and review the physics of MCNP. Some of the latest developments of Monte Carlo Models are also reviewed. A variety of examples are presented to illustrate the uses of Monte Carlo numerical models
Numerical schemes for one-point closure turbulence models
International Nuclear Information System (INIS)
Larcher, Aurelien
2010-01-01
First-order Reynolds Averaged Navier-Stokes (RANS) turbulence models are studied in this thesis. These latter consist of the Navier-Stokes equations, supplemented with a system of balance equations describing the evolution of characteristic scalar quantities called 'turbulent scales'. In so doing, the contribution of the turbulent agitation to the momentum can be determined by adding a diffusive coefficient (called 'turbulent viscosity') in the Navier-Stokes equations, such that it is defined as a function of the turbulent scales. The numerical analysis problems, which are studied in this dissertation, are treated in the frame of a fractional step algorithm, consisting of an approximation on regular meshes of the Navier-Stokes equations by the nonconforming Crouzeix-Raviart finite elements, and a set of scalar convection-diffusion balance equations discretized by the standard finite volume method. A monotone numerical scheme based on the standard finite volume method is proposed so as to ensure that the turbulent scales, like the turbulent kinetic energy (k) and its dissipation rate (ε), remain positive in the case of the standard k - ε model, as well as the k - ε RNG and the extended k - ε - ν 2 models. The convergence of the proposed numerical scheme is then studied on a system composed of the incompressible Stokes equations and a steady convection-diffusion equation, which are both coupled by the viscosities and the turbulent production term. This reduced model allows to deal with the main difficulty encountered in the analysis of such problems: the definition of the turbulent production term leads to consider a class of convection-diffusion problems with an irregular right-hand side belonging to L 1 . Finally, to step towards the unsteady problem, the convergence of the finite volume scheme for a model convection-diffusion equation with L 1 data is proved. The a priori estimates on the solution and on its time derivative are obtained in discrete norms, for
Numerical modelling of glass dissolution: gel layer morphology
Energy Technology Data Exchange (ETDEWEB)
Devreux, F. E-mail: fd@pmc.polytechnique.fr; Barboux, P
2001-09-01
Numerical simulations of glass dissolution are presented. The glass is modelized as a random binary mixture composed of two species representing silica and soluble oxides, such as boron and alkali oxides. The soluble species are dissolved immediately when they are in contact with the solution. For the species which represents silica, one introduces dissolution and condensation probabilities. It is shown that the morphology and the thickness of the surface hydration layer (the gel) are highly dependent on the dissolution model, especially on the parameter which controls the surface tension. Simulations with different glass surface area to solution volume ratio (S/V) show that this experimental parameter has important effects on both the shrinkage and the gel layer thickness.
Advanced Combustion Numerics and Modeling - FY18 First Quarter Report
Energy Technology Data Exchange (ETDEWEB)
Whitesides, R. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Killingsworth, N. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); McNenly, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Petitpas, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2018-01-05
This project is focused on early stage research and development of numerical methods and models to improve advanced engine combustion concepts and systems. The current focus is on development of new mathematics and algorithms to reduce the time to solution for advanced combustion engine design using detailed fuel chemistry. The research is prioritized towards the most time-consuming workflow bottlenecks (computer and human) and accuracy gaps that slow ACS program members. Zero-RK, the fast and accurate chemical kinetics solver software developed in this project, is central to the research efforts and continues to be developed to address the current and emerging needs of the engine designers, engine modelers and fuel mechanism developers.
Numerical modeling of keyhole dynamics in laser welding
Zhang, Wen-Hai; Zhou, Jun; Tsai, Hai-Lung
2003-03-01
Mathematical models and the associated numerical techniques have been developed to study the following cases: (1) the formation and collapse of a keyhole, (2) the formation of porosity and its control strategies, (3) laser welding with filler metals, and (4) the escape of zinc vapor in laser welding of galvanized steel. The simulation results show that the formation of porosity in the weld is caused by two competing mechanisms: one is the solidification rate of the molten metal and the other is the speed that molten metal backfills the keyhole after laser energy is terminated. The models have demonstrated that porosity can be reduced or eliminated by adding filler metals, controlling laser tailing power, or applying an electromagnetic force during keyhole collapse process. It is found that a uniform composition of weld pool is difficult to achieve by filler metals due to very rapid solidification of the weld pool in laser welding, as compared to that in gas metal arc welding.
Numerical modeling and optimization of machining duplex stainless steels
Directory of Open Access Journals (Sweden)
Rastee D. Koyee
2015-01-01
Full Text Available The shortcomings of the machining analytical and empirical models in combination with the industry demands have to be fulfilled. A three-dimensional finite element modeling (FEM introduces an attractive alternative to bridge the gap between pure empirical and fundamental scientific quantities, and fulfill the industry needs. However, the challenging aspects which hinder the successful adoption of FEM in the machining sector of manufacturing industry have to be solved first. One of the greatest challenges is the identification of the correct set of machining simulation input parameters. This study presents a new methodology to inversely calculate the input parameters when simulating the machining of standard duplex EN 1.4462 and super duplex EN 1.4410 stainless steels. JMatPro software is first used to model elastic–viscoplastic and physical work material behavior. In order to effectively obtain an optimum set of inversely identified friction coefficients, thermal contact conductance, Cockcroft–Latham critical damage value, percentage reduction in flow stress, and Taylor–Quinney coefficient, Taguchi-VIKOR coupled with Firefly Algorithm Neural Network System is applied. The optimization procedure effectively minimizes the overall differences between the experimentally measured performances such as cutting forces, tool nose temperature and chip thickness, and the numerically obtained ones at any specified cutting condition. The optimum set of input parameter is verified and used for the next step of 3D-FEM application. In the next stage of the study, design of experiments, numerical simulations, and fuzzy rule modeling approaches are employed to optimize types of chip breaker, insert shapes, process conditions, cutting parameters, and tool orientation angles based on many important performances. Through this study, not only a new methodology in defining the optimal set of controllable parameters for turning simulations is introduced, but also
Advanced numerical modelling of a fire. Final report
International Nuclear Information System (INIS)
Heikkilae, L.; Keski-Rahkonen, O.
1996-03-01
Experience and probabilistic risk assessments show that fires present a major hazard in a nuclear power plant (NPP). The PALOME project (1988-92) improved the quality of numerical simulation of fires to make it a useful tool for fire safety analysis. Some of the most advanced zone model fire simulation codes were acquired. The performance of the codes was studied through literature and personal interviews in earlier studies and BRI2 code from the Japanese Building Research Institute was selected for further use. In PALOME 2 project this work was continued. Information obtained from large-scale fire tests at the German HDR facility allowed reliable prediction of the rate of heat release and was used for code validation. BRI2 code was validated particularly by participation in the CEC standard problem 'Prediction of effects caused by a cable fire experiment within the HDR-facility'. Participation in the development of a new field model code SOFIE specifically for fire applications as British-Swedish-Finnish cooperation was one of the goals of the project. SOFIE code was implemented at VTT and the first results of validation simulations were obtained. Well instrumented fire tests on electronic cabinets were carried out to determine source terms for simulation of room fires and to estimate fire spread to adjacent cabinets. The particular aim of this study was to measure the rate of heat release from a fire in an electronic cabinet. From the three tests, differing mainly in the amount of the fire load, data was obtained for source terms in numerical modelling of fires in rooms containing electronic cabinets. On the basis of these tests also a simple natural ventilation model was derived. (19 refs.)
Numerical explorations of R. M. Goodwin's business cycle model.
Jakimowicz, Aleksander
2010-01-01
Goodwin's model, which was formulated in , still attracts economists' attention. The model possesses numerous interesting properties that have been discovered only recently due to the development of the chaos theory and the complexity theory. The first numerical explorations of the model were conducted in the early s by Strotz, McAnulty and Naines (1953). They discovered the coexistence of attractors that are well-known today, two properties of chaotic systems: the sensitive dependence on the initial conditions and the sensitive dependence on parameters. The occurrence of periodic and chaotic attractors is dependent on the value of parameters in a system. In case of certain parametric values fractal basin boundaries exist which results in enormous system sensitivity to external noise. If periodic attractors are placed in the neighborhood of the fractal basin boundaries, then even a low external noise can move the trajectory into the region in which the basin's structure is tangled. This leads to a kind of movement that resembles a chaotic movement on a strange attractor. In Goodwin's model, apart from typical chaotic behavior, there exists yet another kind of complex movements - transient chaotic behavior that is caused by the occurrence of invariant chaotic sets that are not attracting. Such sets are represented by chaotic saddles. Some of the latest observation methods of trajectories lying on invariant chaotic sets that are not attracting are straddle methods. This article provides examples of the basin boundary straddle trajectory and the saddle straddle trajectory. These cases were studied by Lorenz and Nusse (2002). I supplement the results they acquired with calculations of capacity dimension and correlation dimension.
Mechanical Interaction in Pressurized Pipe Systems: Experiments and Numerical Models
Directory of Open Access Journals (Sweden)
Mariana Simão
2015-11-01
Full Text Available The dynamic interaction between the unsteady flow occurrence and the resulting vibration of the pipe are analyzed based on experiments and numerical models. Waterhammer, structural dynamic and fluid–structure interaction (FSI are the main subjects dealt with in this study. Firstly, a 1D model is developed based on the method of characteristics (MOC using specific damping coefficients for initial components associated with rheological pipe material behavior, structural and fluid deformation, and type of anchored structural supports. Secondly a 3D coupled complex model based on Computational Fluid Dynamics (CFD, using a Finite Element Method (FEM, is also applied to predict and distinguish the FSI events. Herein, a specific hydrodynamic model of viscosity to replicate the operation of a valve was also developed to minimize the number of mesh elements and the complexity of the system. The importance of integrated analysis of fluid–structure interaction, especially in non-rigidity anchored pipe systems, is equally emphasized. The developed models are validated through experimental tests.
Numerical modeling of buoyancy-driven turbulent flows in enclosures
International Nuclear Information System (INIS)
Hsieh, K.J.; Lien, F.S.
2004-01-01
Modeling turbulent natural convection in enclosures with differentially heated vertical walls is numerically challenging, in particular, when low-Reynolds-number (low-Re) models are adopted. When the turbulence level in the core region of cavity is low, most low-Re models, particular those showing good performance for bypass transitional flows, tend to relaminarize the flow and, as a consequence, significantly underpredict the near-wall turbulence intensities and boundary-layer thickness. Another challenge associated with low-turbulence buoyancy-driven flows in enclosures is its inherent unsteadiness, which can pose convergence problems when a steady Reynolds-averaged Navier-Stokes (RANS) equation is solved. In the present study, an unsteady RANS approach in conjunction with the low-Re k-ε model of Lien and Leschziner [Int. J. Comput. Fluid Dyn. 12 (1999) 1] is initially adopted and the predicted flow field is found effectively relaminarized. To overcome this difficulty, likely caused by the low-Re functions in the ε-equation, the two-layer approach is attempted, in which ε is prescribed algebraically using the one-equation k-l model of Wolfshtein [Int. J. Heat Mass Transfer 12 (1969) 301]. The two-layer approach combined with a quadratic stress-strain relation gives overall the best performance in terms of mean velocities, temperature and turbulence quantities
Numerical approaches to model perturbation fire in turing pattern formations
Campagna, R.; Brancaccio, M.; Cuomo, S.; Mazzoleni, S.; Russo, L.; Siettos, K.; Giannino, F.
2017-11-01
Turing patterns were observed in chemical, physical and biological systems described by coupled reaction-diffusion equations. Several models have been formulated proposing the water as the causal mechanism of vegetation pattern formation, but this isn't an exhaustive hypothesis in some natural environments. An alternative explanation has been related to the plant-soil negative feedback. In Marasco et al. [1] the authors explored the hypothesis that both mechanisms contribute in the formation of regular and irregular vegetation patterns. The mathematical model consists in three partial differential equations (PDEs) that take into account for a dynamic balance between biomass, water and toxic compounds. A numerical approach is mandatory also to investigate on the predictions of this kind of models. In this paper we start from the mathematical model described in [1], set the model parameters such that the biomass reaches a stable spatial pattern (spots) and present preliminary studies about the occurrence of perturbing events, such as wildfire, that can affect the regularity of the biomass configuration.
Numerical modeling of laser assisted tape winding process
Zaami, Amin; Baran, Ismet; Akkerman, Remko
2017-10-01
Laser assisted tape winding (LATW) has become more and more popular way of producing new thermoplastic products such as ultra-deep sea water riser, gas tanks, structural parts for aerospace applications. Predicting the temperature in LATW has been a source of great interest since the temperature at nip-point plays a key role for mechanical interface performance. Modeling the LATW process includes several challenges such as the interaction of optics and heat transfer. In the current study, numerical modeling of the optical behavior of laser radiation on circular surfaces is investigated based on a ray tracing and non-specular reflection model. The non-specular reflection is implemented considering the anisotropic reflective behavior of the fiber-reinforced thermoplastic tape using a bidirectional reflectance distribution function (BRDF). The proposed model in the present paper includes a three-dimensional circular geometry, in which the effects of reflection from different ranges of the circular surface as well as effect of process parameters on temperature distribution are studied. The heat transfer model is constructed using a fully implicit method. The effect of process parameters on the nip-point temperature is examined. Furthermore, several laser distributions including Gaussian and linear are examined which has not been considered in literature up to now.
Numerical modeling of an estuary: A comprehensive skill assessment
Warner, J.C.; Geyer, W.R.; Lerczak, J.A.
2005-01-01
Numerical simulations of the Hudson River estuary using a terrain-following, three-dimensional model (Regional Ocean Modeling System (ROMS)) are compared with an extensive set of time series and spatially resolved measurements over a 43 day period with large variations in tidal forcing and river discharge. The model is particularly effective at reproducing the observed temporal variations in both the salinity and current structure, including tidal, spring neap, and river discharge-induced variability. Large observed variations in stratification between neap and spring tides are captured qualitatively and quantitatively by the model. The observed structure and variations of the longitudinal salinity gradient are also well reproduced. The most notable discrepancy between the model and the data is in the vertical salinity structure. While the surface-to-bottom salinity difference is well reproduced, the stratification in the model tends to extend all the way to the water surface, whereas the observations indicate a distinct pycnocline and a surface mixed layer. Because the southern boundary coindition is located near the mouth the estuary, the salinity within the domain is particularly sensitive to the specification of salinity at the boundary. A boundary condition for the horizontal salinity gradient, based on the local value of salinity, is developed to incorporate physical processes beyond the open boundary not resolved by the model. Model results are sensitive to the specification of the bottom roughness length and vertical stability functions, insofar as they influence the intensity of vertical mixing. The results only varied slightly between different turbulence closure methods of k-??, k-??, and k-kl. Copyright 2005 by the American Geophysical Union.
A numerical strategy for modelling rotating stall in core compressors
Vahdati, M.
2007-03-01
The paper will focus on one specific core-compressor instability, rotating stall, because of the pressing industrial need to improve current design methods. The determination of the blade response during rotating stall is a difficult problem for which there is no reliable procedure. During rotating stall, the blades encounter the stall cells and the excitation depends on the number, size, exact shape and rotational speed of these cells. The long-term aim is to minimize the forced response due to rotating stall excitation by avoiding potential matches between the vibration modes and the rotating stall pattern characteristics. Accurate numerical simulations of core-compressor rotating stall phenomena require the modelling of a large number of bladerows using grids containing several tens of millions of points. The time-accurate unsteady-flow computations may need to be run for several engine revolutions for rotating stall to get initiated and many more before it is fully developed. The difficulty in rotating stall initiation arises from a lack of representation of the triggering disturbances which are inherently present in aeroengines. Since the numerical model represents a symmetric assembly, the only random mechanism for rotating stall initiation is provided by numerical round-off errors. In this work, rotating stall is initiated by introducing a small amount of geometric mistuning to the rotor blades. Another major obstacle in modelling flows near stall is the specification of appropriate upstream and downstream boundary conditions. Obtaining reliable boundary conditions for such flows can be very difficult. In the present study, the low-pressure compression (LPC) domain is placed upstream of the core compressor. With such an approach, only far field atmospheric boundary conditions are specified which are obtained from aircraft speed and altitude. A chocked variable-area nozzle, placed after the last compressor bladerow in the model, is used to impose boundary
Estimation of the breaking of rigor mortis by myotonometry.
Vain, A; Kauppila, R; Vuori, E
1996-05-31
Myotonometry was used to detect breaking of rigor mortis. The myotonometer is a new instrument which measures the decaying oscillations of a muscle after a brief mechanical impact. The method gives two numerical parameters for rigor mortis, namely the period and decrement of the oscillations, both of which depend on the time period elapsed after death. In the case of breaking the rigor mortis by muscle lengthening, both the oscillation period and decrement decreased, whereas, shortening the muscle caused the opposite changes. Fourteen h after breaking the stiffness characteristics of the right and left m. biceps brachii, or oscillation periods, were assimilated. However, the values for decrement of the muscle, reflecting the dissipation of mechanical energy, maintained their differences.
Comparison of Laboratory Experimental Data to XBeach Numerical Model Output
Demirci, Ebru; Baykal, Cuneyt; Guler, Isikhan; Sogut, Erdinc
2016-04-01
Coastal zones are living and constantly changing environments where both the natural events and the human-interaction results come into picture regarding to the shoreline behavior. Both the nature of the coastal zone and the human activities shape together the resultants of the interaction with oceans and coasts. Natural extreme events may result in the need of human interference, such as building coastal structures in order to prevent from disasters or any man-made structure throughout a coastline may affect the hydrodynamics and morphology in the nearshore. In order to understand and cope with this cycle of cause and effect relationship, the numerical models developed. XBeach is an open-source, 2DH, depth average numerical model including the hydrodynamic processes of short wave transformation (refraction, shoaling and breaking), long wave (infragravity wave) transformation (generation, propagation and dissipation), wave-induced setup and unsteady currents, as well as overwash and inundation and morphodynamic processes of bed load and suspended sediment transport, dune face avalanching, bed update and breaching (Roelvink et al., 2010). Together with XBeach numerical model, it is possible to both verify and visualize the resultant external effects to the initial shorelines in coastal zones. Recently, Baykal et al. (2015) modelled the long term morphology changes with XBeach near Kızılırmak river mouth consisting of one I-shaped and one Y-shaped groins. In order to investigate the nature of the shoreline and near shore hydrodynamic conditions and morphology, the five laboratory experiments are conducted in the Largescale Sediment Transport Facility at the U.S. Army Engineer Research and Development Center in order to be used to improve longshore sand transport relationships under the combined influence of waves and currents and the enhancement of predictive numerical models of beach morphology evolution. The first series of the experiments were aimed at
Numerical Analysis of Ginzburg-Landau Models for Superconductivity.
Coskun, Erhan
Thin film conventional, as well as High T _{c} superconductors of various geometric shapes placed under both uniform and variable strength magnetic field are studied using the universially accepted macroscopic Ginzburg-Landau model. A series of new theoretical results concerning the properties of solution is presented using the semi -discrete time-dependent Ginzburg-Landau equations, staggered grid setup and natural boundary conditions. Efficient serial algorithms including a novel adaptive algorithm is developed and successfully implemented for solving the governing highly nonlinear parabolic system of equations. Refinement technique used in the adaptive algorithm is based on modified forward Euler method which was also developed by us to ease the restriction on time step size for stability considerations. Stability and convergence properties of forward and modified forward Euler schemes are studied. Numerical simulations of various recent physical experiments of technological importance such as vortes motion and pinning are performed. The numerical code for solving time-dependent Ginzburg-Landau equations is parallelized using BlockComm -Chameleon and PCN. The parallel code was run on the distributed memory multiprocessors intel iPSC/860, IBM-SP1 and cluster of Sun Sparc workstations, all located at Mathematics and Computer Science Division, Argonne National Laboratory.
CDIAC catalog of numeric data packages and computer model packages
International Nuclear Information System (INIS)
Boden, T.A.; Stoss, F.W.
1993-05-01
The Carbon Dioxide Information Analysis Center acquires, quality-assures, and distributes to the scientific community numeric data packages (NDPs) and computer model packages (CMPs) dealing with topics related to atmospheric trace-gas concentrations and global climate change. These packages include data on historic and present atmospheric CO 2 and CH 4 concentrations, historic and present oceanic CO 2 concentrations, historic weather and climate around the world, sea-level rise, storm occurrences, volcanic dust in the atmosphere, sources of atmospheric CO 2 , plants' response to elevated CO 2 levels, sunspot occurrences, and many other indicators of, contributors to, or components of climate change. This catalog describes the packages presently offered by CDIAC, reviews the processes used by CDIAC to assure the quality of the data contained in these packages, notes the media on which each package is available, describes the documentation that accompanies each package, and provides ordering information. Numeric data are available in the printed NDPs and CMPs, in CD-ROM format, and from an anonymous FTP area via Internet. All CDIAC information products are available at no cost
Numerical modelling of diesel spray using the Eulerian multiphase approach
International Nuclear Information System (INIS)
Vujanović, Milan; Petranović, Zvonimir; Edelbauer, Wilfried; Baleta, Jakov; Duić, Neven
2015-01-01
Highlights: • Numerical model for fuel disintegration was presented. • Fuel liquid and vapour were calculated. • Good agreement with experimental data was shown for various combinations of injection and chamber pressure. - Abstract: This research investigates high pressure diesel fuel injection into the combustion chamber by performing computational simulations using the Euler–Eulerian multiphase approach. Six diesel-like conditions were simulated for which the liquid fuel jet was injected into a pressurised inert environment (100% N 2 ) through a 205 μm nozzle hole. The analysis was focused on the liquid jet and vapour penetration, describing spatial and temporal spray evolution. For this purpose, an Eulerian multiphase model was implemented, variations of the sub-model coefficients were performed, and their impact on the spray formation was investigated. The final set of sub-model coefficients was applied to all operating points. Several simulations of high pressure diesel injections (50, 80, and 120 MPa) combined with different chamber pressures (5.4 and 7.2 MPa) were carried out and results were compared to the experimental data. The predicted results share a similar spray cloud shape for all conditions with the different vapour and liquid penetration length. The liquid penetration is shortened with the increase in chamber pressure, whilst the vapour penetration is more pronounced by elevating the injection pressure. Finally, the results showed good agreement when compared to the measured data, and yielded the correct trends for both the liquid and vapour penetrations under different operating conditions
Merging AI and numerical modeling for accelerator control
International Nuclear Information System (INIS)
Schultz, D.E.; Silbar, R.R.
1987-01-01
The authors report the beginnings of an experiment to evaluate the power and limitations of artificial intelligence techniques combined with beam-line modeling for solving problems in accelerator control. Using the Knowledge Engineering Environment (KEE) system, they have built a knowledge base that describes the characteristics and the relationships of about 30 devices in a typical accelerator beam line. Each device in the line is categorized and pertinent attributes for each category are defined. Specific values for each device are assigned in the knowledge base to represent static characteristics. Device-specific slots are also provided for dynamic attributes. The definition of these slots reflects the data type and any limitations or restrictions on the range of the data. The authors model relationships between the various beam-line devices using the techniques of rules, active values, and object-oriented models. The knowledge base provides a framework for analyzing faults and offering suggestions to assist in tuning, based on information provided by the accelerator physicists (domain experts) responsible for designing and tuning this beam line. Our knowledge base has a powerful graphical interface. It allows the operator to mouse on an icon for a particular icon in the schematic of the beam line and obtain device-specific information and control over that device. The beam optics code Transport is used to model the beam line numerically. 11 refs., 7 figs
Numerical Modeling of Electrical Contact Conductance of Rough Bodies
Directory of Open Access Journals (Sweden)
M. V. Murashov
2015-01-01
Full Text Available Since the beginning of the 20th century to the present time, efforts have been made to develop a model of the electrical contact conductance. The development of micro- and nanotechnologies make contact conductance problem more essential. To conduct borrowing from a welldeveloped thermal contact conductance models on the basis of thermal and electrical conductivity analogy is often not possible due to a number of fundamental differences. While some 3Dmodels of rough bodies deformation have been developed in one way or another, a 3D-model of the electrical conductance through rough bodies contact is still not. A spatial model of electrical contact of rough bodies is proposed, allows one to calculate the electrical contact conductance as a function of the contact pressure. Representative elements of the bodies are parallelepipeds with deterministic roughness on the contacting surfaces. First the non-linear elastic-plastic deformation of rough surface under external pressure is solved using the finite element software ANSYS. Then the solution of electrostatic problem goes on the same finite element mesh. Aluminum AD1 is used as the material of the contacting bodies with properties that account for cold work hardening of the surface. The numerical model is built within the continuum mechanics and nanoscale effects are not taken into account. The electrical contact conductance was calculated on the basis of the concept of electrical resistance of the model as the sum of the electrical resistances of the contacting bodies and the contact itself. It was assumed that there is no air in the gap between the bodies. The dependence of the electrical contact conductance on the contact pressure is calculated as well as voltage and current density distributions in the contact bodies. It is determined that the multi-asperity contact mode, adequate to real roughness, is achieved at pressures higher than 3MPa, while results within the single contact spot are
Integrated numerical modeling of a laser gun injector
International Nuclear Information System (INIS)
Liu, H.; Benson, S.; Bisognano, J.; Liger, P.; Neil, G.; Neuffer, D.; Sinclair, C.; Yunn, B.
1993-06-01
CEBAF is planning to incorporate a laser gun injector into the linac front end as a high-charge cw source for a high-power free electron laser and nuclear physics. This injector consists of a DC laser gun, a buncher, a cryounit and a chicane. The performance of the injector is predicted based on integrated numerical modeling using POISSON, SUPERFISH and PARMELA. The point-by-point method incorporated into PARMELA by McDonald is chosen for space charge treatment. The concept of ''conditioning for final bunching'' is employed to vary several crucial parameters of the system for achieving highest peak current while maintaining low emittance and low energy spread. Extensive parameter variation studies show that the design will perform beyond the specifications for FEL operations aimed at industrial applications and fundamental scientific research. The calculation also shows that the injector will perform as an extremely bright cw electron source
Numerical Model based Reliability Estimation of Selective Laser Melting Process
DEFF Research Database (Denmark)
Mohanty, Sankhya; Hattel, Jesper Henri
2014-01-01
Selective laser melting is developing into a standard manufacturing technology with applications in various sectors. However, the process is still far from being at par with conventional processes such as welding and casting, the primary reason of which is the unreliability of the process. While...... of the selective laser melting process. A validated 3D finite-volume alternating-direction-implicit numerical technique is used to model the selective laser melting process, and is calibrated against results from single track formation experiments. Correlation coefficients are determined for process input...... parameters such as laser power, speed, beam profile, etc. Subsequently, uncertainties in the processing parameters are utilized to predict a range for the various outputs, using a Monte Carlo method based uncertainty analysis methodology, and the reliability of the process is established....
Numerical modelling of flow pattern for high swirling flows
Directory of Open Access Journals (Sweden)
Parra Teresa
2015-01-01
Full Text Available This work focuses on the interaction of two coaxial swirling jets. High swirl burners are suitable for lean flames and produce low emissions. Computational Fluid Dynamics has been used to study the isothermal behaviour of two confined jets whose setup and operating conditions are those of the benchmark of Roback and Johnson. Numerical model is a Total Variation Diminishing and PISO is used to pressure velocity coupling. Transient analysis let identify the non-axisymmetric region of reverse flow. The center of instantaneous azimuthal velocities is not located in the axis of the chamber. The temporal sampling evidences this center spins around the axis of the device forming the precessing vortex core (PVC whose Strouhal numbers are more than two for Swirl numbers of one. Influence of swirl number evidences strong swirl numbers are precursor of large vortex breakdown. Influence of conical diffusers evidence the reduction of secondary flows associated to boundary layer separation.
Numerical model of electron cyclotron resonance ion source
Directory of Open Access Journals (Sweden)
V. Mironov
2015-12-01
Full Text Available Important features of the electron cyclotron resonance ion source (ECRIS operation are accurately reproduced with a numerical code. The code uses the particle-in-cell technique to model the dynamics of ions in ECRIS plasma. It is shown that a gas dynamical ion confinement mechanism is sufficient to provide the ion production rates in ECRIS close to the experimentally observed values. Extracted ion currents are calculated and compared to the experiment for a few sources. Changes in the simulated extracted ion currents are obtained with varying the gas flow into the source chamber and the microwave power. Empirical scaling laws for ECRIS design are studied and the underlying physical effects are discussed.
Experimental and numerical investigation of a simplified exhaust model
Directory of Open Access Journals (Sweden)
Balázs Vehovszky
2016-10-01
Full Text Available A simplified experimental equipment was built to investigate heat radiation and free convection around hot exhaust pipe. Temperatures were measured on the surface of the pipe as like as on heat insulating and -reflecting aluminum shield. Special care was taken to the temperature measuring method: result proved that inappropriate fixing of measuring thermocouples lead to an error of up to 30 % in the temperature-increase values. A detailed 1D numerical model was set up and parametrized so as to the calculation results can be fitted to measured temperature values. In this way thermal properties of the surfaces – as emissivities, absorption coefficients and convective heat transfer coefficients – were determined for temperature sweeps and stationary state cases. The used methods are to be further improved for real automotive parts and higher temperatures.
Numerical model for dendritic solidification of binary alloys
Felicelli, S. D.; Heinrich, J. C.; Poirier, D. R.
1993-01-01
A finite element model capable of simulating solidification of binary alloys and the formation of freckles is presented. It uses a single system of equations to deal with the all-liquid region, the dendritic region, and the all-solid region. The dendritic region is treated as an anisotropic porous medium. The algorithm uses the bilinear isoparametric element, with a penalty function approximation and a Petrov-Galerkin formulation. Numerical simulations are shown in which an NH4Cl-H2O mixture and a Pb-Sn alloy melt are cooled. The solidification process is followed in time. Instabilities in the process can be clearly observed and the final compositions obtained.
Modelling of cardiovascular system: development of a hybrid (numerical-physical) model.
Ferrari, G; Kozarski, M; De Lazzari, C; Górczyńska, K; Mimmo, R; Guaragno, M; Tosti, G; Darowski, M
2003-12-01
Physical models of the circulation are used for research, training and for testing of implantable active and passive circulatory prosthetic and assistance devices. However, in comparison with numerical models, they are rigid and expensive. To overcome these limitations, we have developed a model of the circulation based on the merging of a lumped parameter physical model into a numerical one (producing therefore a hybrid). The physical model is limited to the barest essentials and, in this application, developed to test the principle, it is a windkessel representing the systemic arterial tree. The lumped parameters numerical model was developed in LabVIEW environment and represents pulmonary and systemic circulation (except the systemic arterial tree). Based on the equivalence between hydraulic and electrical circuits, this prototype was developed connecting the numerical model to an electrical circuit--the physical model. This specific solution is valid mainly educationally but permits the development of software and the verification of preliminary results without using cumbersome hydraulic circuits. The interfaces between numerical and electrical circuits are set up by a voltage controlled current generator and a voltage controlled voltage generator. The behavior of the model is analyzed based on the ventricular pressure-volume loops and on the time course of arterial and ventricular pressures and flow in different circulatory conditions. The model can represent hemodynamic relationships in different ventricular and circulatory conditions.
Numerical Modelling of Extreme Natural Hazards in the Russian Seas
Arkhipkin, Victor; Dobrolyubov, Sergey; Korablina, Anastasia; Myslenkov, Stanislav; Surkova, Galina
2017-04-01
Storm surges and extreme waves are severe natural sea hazards. Due to the almost complete lack of natural observations of these phenomena in the Russian seas (Caspian, Black, Azov, Baltic, White, Barents, Okhotsk, Kara), especially about their formation, development and destruction, they have been studied using numerical simulation. To calculate the parameters of wind waves for the seas listed above, except the Barents Sea, the spectral model SWAN was applied. For the Barents and Kara seas we used WAVEWATCH III model. Formation and development of storm surges were studied using ADCIRC model. The input data for models - bottom topography, wind, atmospheric pressure and ice cover. In modeling of surges in the White and Barents seas tidal level fluctuations were used. They have been calculated from 16 harmonic constant obtained from global atlas tides FES2004. Wind, atmospheric pressure and ice cover was taken from the NCEP/NCAR reanalysis for the period from 1948 to 2010, and NCEP/CFSR reanalysis for the period from 1979 to 2015. In modeling we used both regular and unstructured grid. The wave climate of the Caspian, Black, Azov, Baltic and White seas was obtained. Also the extreme wave height possible once in 100 years has been calculated. The statistics of storm surges for the White, Barents and Azov Seas were evaluated. The contribution of wind and atmospheric pressure in the formation of surges was estimated. The technique of climatic forecast frequency of storm synoptic situations was developed and applied for every sea. The research was carried out with financial support of the RFBR (grant 16-08-00829).
Numerical and physical modelling of oil spreading in broken ice
International Nuclear Information System (INIS)
Gjoesteen, Janne K. Oekland
2002-01-01
The present work focuses on oil spreading in broken ice and the content of this thesis falls into three categories: 1) The physical and numerical modelling of oil spreading in ice. 2) Ice models and parameters describing the ice cover. 3) Experiments on oil spreading in broken ice. A background study was carried out to investigate existing models for simulating oil in broken ice. Most of them describe motion of oil simply as a function of the ice motion and do not take advantage of the possibilities that recent ice models provide. We decided to choose another direction, starting from scratch with equations describing the flow of oil on top of a water surface. The equations were implemented numerically, including proper boundary conditions to account for the presence of physical restrictions in the form of ice floes in the simulation area. The implementation was designed to be able to apply data on ice motion calculated by an existing dynamic ice model. A first validation of the model was carried out using existing experimental data. As those data were obtained in a different setting, the recorded parameters and set-up of the experiment were not ideal for our purpose. However, we were able to conclude that our model behaviour was reasonable. We have carried out statistical analysis on meteorological data of wind speeds, temperatures, flow sizes and ice thickness to obtain probability distributions describing the parameters. Those data has been collected in the Pechora Sea. Wind and temperature had been recorded for a period of 30-40 years. For this region we also had available Argos satellite data from four buoys drifting in the ice in April-June 1998. The Argos data were carefully analysed to suggest probability distributions and return periods for certain speeds. (Indoor basin tests were carried out to obtain data on spreading of oil in broken ice. A set of 20 tests was conducted, each with different type of oil, ice concentration, slush concentration or ice
Numerical and physical modelling of oil spreading in broken ice
Energy Technology Data Exchange (ETDEWEB)
Gjoesteen, Janne K. Oekland
2002-07-01
The present work focuses on oil spreading in broken ice and the content of this thesis falls into three categories: 1) The physical and numerical modelling of oil spreading in ice. 2) Ice models and parameters describing the ice cover. 3) Experiments on oil spreading in broken ice. A background study was carried out to investigate existing models for simulating oil in broken ice. Most of them describe motion of oil simply as a function of the ice motion and do not take advantage of the possibilities that recent ice models provide. We decided to choose another direction, starting from scratch with equations describing the flow of oil on top of a water surface. The equations were implemented numerically, including proper boundary conditions to account for the presence of physical restrictions in the form of ice floes in the simulation area. The implementation was designed to be able to apply data on ice motion calculated by an existing dynamic ice model. A first validation of the model was carried out using existing experimental data. As those data were obtained in a different setting, the recorded parameters and set-up of the experiment were not ideal for our purpose. However, we were able to conclude that our model behaviour was reasonable. We have carried out statistical analysis on meteorological data of wind speeds, temperatures, flow sizes and ice thickness to obtain probability distributions describing the parameters. Those data has been collected in the Pechora Sea. Wind and temperature had been recorded for a period of 30-40 years. For this region we also had available Argos satellite data from four buoys drifting in the ice in April-June 1998. The Argos data were carefully analysed to suggest probability distributions and return periods for certain speeds. (Indoor basin tests were carried out to obtain data on spreading of oil in broken ice. A set of 20 tests was conducted, each with different type of oil, ice concentration, slush concentration or ice
Description of Supply Openings in Numerical Models for Room Air Distribution
DEFF Research Database (Denmark)
Nielsen, Peter V.
This paper discusses various possibilities for describing supply openings in numerical models of room air distribution.......This paper discusses various possibilities for describing supply openings in numerical models of room air distribution....
Numerical modeling of rapidly varying flows using HEC-RAS and WSPG models.
Rao, Prasada; Hromadka, Theodore V
2016-01-01
The performance of two popular hydraulic models (HEC-RAS and WSPG) for modeling hydraulic jump in an open channel is investigated. The numerical solutions are compared with a new experimental data set obtained for varying channel bottom slopes and flow rates. Both the models satisfactorily predict the flow depths and location of the jump. The end results indicate that the numerical models output is sensitive to the value of chosen roughness coefficient. For this application, WSPG model is easier to implement with few input variables.
Atlas : A library for numerical weather prediction and climate modelling
Deconinck, Willem; Bauer, Peter; Diamantakis, Michail; Hamrud, Mats; Kühnlein, Christian; Maciel, Pedro; Mengaldo, Gianmarco; Quintino, Tiago; Raoult, Baudouin; Smolarkiewicz, Piotr K.; Wedi, Nils P.
2017-11-01
The algorithms underlying numerical weather prediction (NWP) and climate models that have been developed in the past few decades face an increasing challenge caused by the paradigm shift imposed by hardware vendors towards more energy-efficient devices. In order to provide a sustainable path to exascale High Performance Computing (HPC), applications become increasingly restricted by energy consumption. As a result, the emerging diverse and complex hardware solutions have a large impact on the programming models traditionally used in NWP software, triggering a rethink of design choices for future massively parallel software frameworks. In this paper, we present Atlas, a new software library that is currently being developed at the European Centre for Medium-Range Weather Forecasts (ECMWF), with the scope of handling data structures required for NWP applications in a flexible and massively parallel way. Atlas provides a versatile framework for the future development of efficient NWP and climate applications on emerging HPC architectures. The applications range from full Earth system models, to specific tools required for post-processing weather forecast products. The Atlas library thus constitutes a step towards affordable exascale high-performance simulations by providing the necessary abstractions that facilitate the application in heterogeneous HPC environments by promoting the co-design of NWP algorithms with the underlying hardware.
Numerical study of similarity in prototype and model pumped turbines
International Nuclear Information System (INIS)
Li, Z J; Wang, Z W; Bi, H L
2014-01-01
Similarity study of prototype and model pumped turbines are performed by numerical simulation and the partial discharge case is analysed in detail. It is found out that in the RSI (rotor-stator interaction) region where the flow is convectively accelerated with minor flow separation, a high level of similarity in flow patterns and pressure fluctuation appear with relative pressure fluctuation amplitude of model turbine slightly higher than that of prototype turbine. As for the condition in the runner where the flow is convectively accelerated with severe separation, similarity fades substantially due to different topology of flow separation and vortex formation brought by distinctive Reynolds numbers of the two turbines. In the draft tube where the flow is diffusively decelerated, similarity becomes debilitated owing to different vortex rope formation impacted by Reynolds number. It is noted that the pressure fluctuation amplitude and characteristic frequency of model turbine are larger than those of prototype turbine. The differences in pressure fluctuation characteristics are discussed theoretically through dimensionless Navier-Stokes equation. The above conclusions are all made based on simulation without regard to the penstock response and resonance
Modeling multiscale evolution of numerous voids in shocked brittle material.
Yu, Yin; Wang, Wenqiang; He, Hongliang; Lu, Tiecheng
2014-04-01
The influence of the evolution of numerous voids on macroscopic properties of materials is a multiscale problem that challenges computational research. A shock-wave compression model for brittle material, which can obtain both microscopic evolution and macroscopic shock properties, was developed using discrete element methods (lattice model). Using a model interaction-parameter-mapping procedure, qualitative features, as well as trends in the calculated shock-wave profiles, are shown to agree with experimental results. The shock wave splits into an elastic wave and a deformation wave in porous brittle materials, indicating significant shock plasticity. Void collapses in the deformation wave were the natural reason for volume shrinkage and deformation. However, media slippage and rotation deformations indicated by complex vortex patterns composed of relative velocity vectors were also confirmed as an important source of shock plasticity. With increasing pressure, the contribution from slippage deformation to the final plastic strain increased. Porosity was found to determine the amplitude of the elastic wave; porosity and shock stress together determine propagation speed of the deformation wave, as well as stress and strain on the final equilibrium state. Thus, shock behaviors of porous brittle material can be systematically designed for specific applications.
A numerical model for etching through a circular hole
International Nuclear Information System (INIS)
Rath, P; Chai, J C; Zheng, H; Lam, Y C; Murukeshan, V M
2006-01-01
A numerical model based on the total concentration of etchant is proposed to model the wet chemical etching through a circular hole. The reaction at the etchant-substrate interface is assumed to be infinitely fast i.e. etching is controlled by the diffusion of etchant to the interface. The proposed model is based on a fixed-grid approach analogous to the enthalpy method. The total concentration of etchant is the sum of the unreacted etchant concentration and the reacted etchant concentration. The reacted concentration of etchant is a measure of the etchfront position during etching. The governing mass diffusion equation based on the total concentration of etchant includes the interface condition. The etchfront position is found implicitly using the proposed approach. The computational domain is fixed, which includes the whole etchant and substrate domain including the mask region. For demonstration purposes, the finite volume method is used to solve the governing mass diffusion equation with prescribed initial and boundary conditions. The effect of mask thickness and initial etchant concentration on the shape evolution of etchfront is studied
A numerical two layer model for blood oxygenation in lungs
International Nuclear Information System (INIS)
Aminatai, A.
2001-01-01
In the modelling of the simultaneous transport of O 2 and CO 2 in the pulmonary circulation described in our earlier studies, the blood has been treated as a homogeneous layer of haemoglobin solution. Since the size of the erythrocyte is not negligible in comparison with that of the capillary, the blood can no longer be considered as a homogeneous fluid and hence, It is worthwhile to consider the blood flow as a two-phase flow consisting of cells and plasma. In the present study, the heterogeneous nature of blood has been proposed by considering the axial train model for the flow [whitmore (1967)], in order to analyze the effect of cell free plasma layer on the process of blood oxygenation in pulmonary capillaries. The proposed model consists of a core of suspended erythrocytes surrounded by a cell free plasma layer near the wall. The coupled system of convective diffusion equaions together with the physiologically relevant boundary, entrance and interface conditions is solved numerically by a four-point semi-implicit scheme to gether with a fixed point iterative technique. The distance traversed by the blood before getting fully oxygenated is computed. It is shown that the core haematocrit and the thickness of the cell depleted layer affect the oxygenation process significantly. It is found that (i) oxygen takes longest and carbondioxide is the fastest to attain equilibraton, (ii) the blood is completely oxygenated within one-fifth part of its transit and (iii) the rate of oxygenation is smaller in case of homogeneous model than that in heterogenous model in the capillary. Finally, the effect of various physiological parameters on the rate of oxygenation has been examined
Axisymmetric Numerical Modeling of Pulse Detonation Rocket Engines
Morris, Christopher I.
2005-01-01
Pulse detonation rocket engines (PDREs) have generated research interest in recent years as a chemical propulsion system potentially offering improved performance and reduced complexity compared to conventional rocket engines. The detonative mode of combustion employed by these devices offers a thermodynamic advantage over the constant-pressure deflagrative combustion mode used in conventional rocket engines and gas turbines. However, while this theoretical advantage has spurred considerable interest in building PDRE devices, the unsteady blowdown process intrinsic to the PDRE has made realistic estimates of the actual propulsive performance problematic. The recent review article by Kailasanath highlights some of the progress that has been made in comparing the available experimental measurements with analytical and numerical models. In recent work by the author, a quasi-one-dimensional, finite rate chemistry CFD model was utilized to study the gasdynamics and performance characteristics of PDREs over a range of blowdown pressure ratios from 1-1000. Models of this type are computationally inexpensive, and enable first-order parametric studies of the effect of several nozzle and extension geometries on PDRE performance over a wide range of conditions. However, the quasi-one-dimensional approach is limited in that it cannot properly capture the multidimensional blast wave and flow expansion downstream of the PDRE, nor can it resolve nozzle flow separation if present. Moreover, the previous work was limited to single-pulse calculations. In this paper, an axisymmetric finite rate chemistry model is described and utilized to study these issues in greater detail. Example Mach number contour plots showing the multidimensional blast wave and nozzle exhaust plume are shown. The performance results are compared with the quasi-one-dimensional results from the previous paper. Both Euler and Navier-Stokes solutions are calculated in order to determine the effect of viscous
Numerical Study of Wind Turbine Wake Modeling Based on a Actuator Surface Model
DEFF Research Database (Denmark)
Zhou, Huai-yang; Xu, Chang; Han, Xing Xing
2017-01-01
In the Actuator Surface Model (ALM), the turbine blades are represented by porous surfaces of velocity and pressure discontinuities to model the action of lifting surfaces on the flow. The numerical simulation is implemented on FLUENT platform combined with N-S equations. This model is improved o...
Stratified flows with variable density: mathematical modelling and numerical challenges.
Murillo, Javier; Navas-Montilla, Adrian
2017-04-01
Stratified flows appear in a wide variety of fundamental problems in hydrological and geophysical sciences. They may involve from hyperconcentrated floods carrying sediment causing collapse, landslides and debris flows, to suspended material in turbidity currents where turbulence is a key process. Also, in stratified flows variable horizontal density is present. Depending on the case, density varies according to the volumetric concentration of different components or species that can represent transported or suspended materials or soluble substances. Multilayer approaches based on the shallow water equations provide suitable models but are not free from difficulties when moving to the numerical resolution of the governing equations. Considering the variety of temporal and spatial scales, transfer of mass and energy among layers may strongly differ from one case to another. As a consequence, in order to provide accurate solutions, very high order methods of proved quality are demanded. Under these complex scenarios it is necessary to observe that the numerical solution provides the expected order of accuracy but also converges to the physically based solution, which is not an easy task. To this purpose, this work will focus in the use of Energy balanced augmented solvers, in particular, the Augmented Roe Flux ADER scheme. References: J. Murillo , P. García-Navarro, Wave Riemann description of friction terms in unsteady shallow flows: Application to water and mud/debris floods. J. Comput. Phys. 231 (2012) 1963-2001. J. Murillo B. Latorre, P. García-Navarro. A Riemann solver for unsteady computation of 2D shallow flows with variable density. J. Comput. Phys.231 (2012) 4775-4807. A. Navas-Montilla, J. Murillo, Energy balanced numerical schemes with very high order. The Augmented Roe Flux ADER scheme. Application to the shallow water equations, J. Comput. Phys. 290 (2015) 188-218. A. Navas-Montilla, J. Murillo, Asymptotically and exactly energy balanced augmented flux
Dispersion of conservative properties for SGD effects by numerical modeling
Gallegos, G.; Marino-Tapia, I.; Enriquez, C.
2013-05-01
The submarine groundwater discharges around de coasts of theYucatán Peninsula are very common because of its karstic nature. These discharges of fresh water into the sea can change the thermohaline conditions of the region. There are several studies that demonstrate that point submarine groundwater discharges can change the superficial temperature and haline conditions near the point-SGD. Furthermore, there is evidence that considerable concentrations of nutrients are transported to the sea via SGDs. In order to quantify the area of influence of a point-SGD and the ability of the coastal system to dissipate the ground water, this study presents a numerical simulation of a point-SGD on the north coast of Yucatán, Dzilam Bravo. Teh flow recorded for this SGD is ~1m^3/s and it is located 200m offshore in waters of less than 2m detph.. The numerical simulation was carried out in the model DELFT-3D which has been calibrated with water level and hydrodynamics data for the region with a grid of 486 x 243 nodes that cover an area of 6 km alongshore by 2 km crosshore with a resolution of 14 m. Three ideal numerical scenarios were simulated: only wind forcing, only tidal forcing and wind-tide forcing. The real cases are for two different wind conditions, the first is a southeast wind, and the second is a breeze with an easterly component; the dominant winds in the region are easterly. Seasonal variation was also simulated; the two conditions that exist in the region are the rainy and dry seasons. The extreme events of ENSO and northerly storms locally known as "nortes" were also simulated. The results of the ideal set of scenarios shows wind as the principal forcing for dispersion and it governs the direction of the salinity gradient. The seasonal variations show that the area of influence in terms of salinity is also a function of the contrast between fresh and sea water, and finally the set of extreme condition simulations shows, in case of the northerly storms, that the
Numerical modelling of an oil spill in the northern Adriatic
Directory of Open Access Journals (Sweden)
Marin Paladin
2012-04-01
Full Text Available Hypothetical cases of oil spills, caused by ship failure in the northern Adriatic, are analysed with the aim of producing three-dimensional models of sea circulation and oil contaminant transport. Sea surface elevations, sea temperature and salinity fields are applied as a forcing argument on the model's open boundaries.The Aladin-HR model with a spatial resolution of 8 km and a time interval of 3 hours is used for atmospheric forcing. River discharges along the coastline in question are introduced as point source terms and are assumed to have zero salinity at their respective locations. The results of the numerical modelling of physical oceanography parameters are validated by measurements carried out in the ‘Adriatic Sea monitoring programme’ in a series of current meter and CTD stations in the period from 1 January 2008 to 15 November 2008.The oil spill model uses the current field obtained from a circulation model.Besides the convective dispersive transport of oil pollution (Lagrangian model of discrete particles, the model takes into account a number of reactive processes such as emulsification, dissolution, evaporation and heat balance between the oil,sea and atmosphere. An actual event took place on 6 February 2008,when the ship `Und Adriyatik' caught fire in the vicinity of the town of Rovinj (Croatia en route from Istanbul (Turkey to Trieste (Italy. At the time the fire broke out, the ship was carrying around 800 tons of oil. Thanks to the rapid intervention of the firedepartment, the fire was extinguished during the following 12 hours,preventing possible catastrophic environmental consequences. Based on this occurrence, five hypothetical scenarios of ship failure with a consequent spill of 800 tons of oil over 12 hours were analysed. The main distinction between the simulated scenarios is the time of the start of the oil spill, corresponding to the times when stronger winds were blowing (>7 m s-1 with a minimum duration of 24 h
Comparing Numerical Spall Simulations with a Nonlinear Spall Formation Model
Ong, L.; Melosh, H. J.
2012-12-01
Spallation accelerates lightly shocked ejecta fragments to speeds that can exceed the escape velocity of the parent body. We present high-resolution simulations of nonlinear shock interactions in the near surface. Initial results show the acceleration of near-surface material to velocities up to 1.8 times greater than the peak particle velocity in the detached shock, while experiencing little to no shock pressure. These simulations suggest a possible nonlinear spallation mechanism to produce the high-velocity, low show pressure meteorites from other planets. Here we pre-sent the numerical simulations that test the production of spall through nonlinear shock interactions in the near sur-face, and compare the results with a model proposed by Kamegai (1986 Lawrence Livermore National Laboratory Report). We simulate near-surface shock interactions using the SALES_2 hydrocode and the Murnaghan equation of state. We model the shock interactions in two geometries: rectangular and spherical. In the rectangular case, we model a planar shock approaching the surface at a constant angle phi. In the spherical case, the shock originates at a point below the surface of the domain and radiates spherically from that point. The angle of the shock front with the surface is dependent on the radial distance of the surface point from the shock origin. We model the target as a solid with a nonlinear Murnaghan equation of state. This idealized equation of state supports nonlinear shocks but is tem-perature independent. We track the maximum pressure and maximum velocity attained in every cell in our simula-tions and compare them to the Hugoniot equations that describe the material conditions in front of and behind the shock. Our simulations demonstrate that nonlinear shock interactions in the near surface produce lightly shocked high-velocity material for both planar and cylindrical shocks. The spall is the result of the free surface boundary condi-tion, which forces a pressure gradient
Realizing rigor in the mathematics classroom
Hull, Ted H (Henry); Balka, Don S
2014-01-01
Rigor put within reach! Rigor: The Common Core has made it policy-and this first-of-its-kind guide takes math teachers and leaders through the process of making it reality. Using the Proficiency Matrix as a framework, the authors offer proven strategies and practical tools for successful implementation of the CCSS mathematical practices-with rigor as a central objective. You'll learn how to Define rigor in the context of each mathematical practice Identify and overcome potential issues, including differentiating instruction and using data
Numerical Modeling of Conjugate Heat Transfer in Fluid Network
Majumdar, Alok
2004-01-01
Fluid network modeling with conjugate heat transfer has many applications in Aerospace engineering. In modeling unsteady flow with heat transfer, it is important to know the variation of wall temperature in time and space to calculate heat transfer between solid to fluid. Since wall temperature is a function of flow, a coupled analysis of temperature of solid and fluid is necessary. In cryogenic applications, modeling of conjugate heat transfer is of great importance to correctly predict boil-off rate in propellant tanks and chill down of transfer lines. In TFAWS 2003, the present author delivered a paper to describe a general-purpose computer program, GFSSP (Generalized Fluid System Simulation Program). GFSSP calculates flow distribution in complex flow circuit for compressible/incompressible, with or without heat transfer or phase change in all real fluids or mixtures. The flow circuit constitutes of fluid nodes and branches. The mass, energy and specie conservation equations are solved at the nodes where as momentum conservation equations are solved at the branches. The proposed paper describes the extension of GFSSP to model conjugate heat transfer. The network also includes solid nodes and conductors in addition to fluid nodes and branches. The energy conservation equations for solid nodes solves to determine the temperatures of the solid nodes simultaneously with all conservation equations governing fluid flow. The numerical scheme accounts for conduction, convection and radiation heat transfer. The paper will also describe the applications of the code to predict chill down of cryogenic transfer line and boil-off rate of cryogenic propellant storage tank.
Numerical modeling of underground storage system for natural gas
Ding, J.; Wang, S.
2017-12-01
Natural gas is an important type of base-load energy, and its supply needs to be adjusted according to different demands in different seasons. For example, since natural gas is increasingly used to replace coal for winter heating, the demand for natural gas in winter is much higher than that in other seasons. As storage systems are the essential tools for balancing seasonal supply and demand, the design and simulation of natural gas storage systems form an important research direction. In this study, a large-scale underground storage system for natural gas is simulated based on theoretical analysis and finite element modeling.It is proven that the problem of axi-symmetric Darcy porous flow of ideal gas is governed by the Boussinesq equation. In terms of the exact solution to the Boussinesq equation, the basic operating characteristics of the underground storage system is analyzed, and it is demonstrated that the propagation distance of the pore pressure is proportional to the 1/4 power of the mass flow rate and to the 1/2 power of the propagation time. This quantitative relationship can be used to guide the overall design of natural gas underground storage systems.In order to fully capture the two-way coupling between pore pressure and elastic matrix deformation, a poro-elastic finite element model for natural gas storage is developed. Based on the numerical model, the dynamic processes of gas injection, storage and extraction are simulated, and the corresponding time-dependent surface deformations are obtained. The modeling results not only provide a theoretical basis for real-time monitoring for the operating status of the underground storage system through surface deformation measurements, but also demonstrate that a year-round balance can be achieved through periodic gas injection and extraction.This work is supported by the CAS "100 talents" Program and the National Natural Science Foundation of China (41371090).
Numerical Simulations of a Multiscale Model of Stratified Langmuir Circulation
Malecha, Ziemowit; Chini, Gregory; Julien, Keith
2012-11-01
Langmuir circulation (LC), a prominent form of wind and surface-wave driven shear turbulence in the ocean surface boundary layer (BL), is commonly modeled using the Craik-Leibovich (CL) equations, a phase-averaged variant of the Navier-Stokes (NS) equations. Although surface-wave filtering renders the CL equations more amenable to simulation than are the instantaneous NS equations, simulations in wide domains, hundreds of times the BL depth, currently earn the ``grand challenge'' designation. To facilitate simulations of LC in such spatially-extended domains, we have derived multiscale CL equations by exploiting the scale separation between submesoscale and BL flows in the upper ocean. The numerical algorithm for simulating this multiscale model resembles super-parameterization schemes used in meteorology, but retains a firm mathematical basis. We have validated our algorithm and here use it to perform multiscale simulations of the interaction between LC and upper ocean density stratification. ZMM, GPC, KJ gratefully acknowledge funding from NSF CMG Award 0934827.
Global numerical modeling of magnetized plasma in a linear device
DEFF Research Database (Denmark)
Magnussen, Michael Løiten
Understanding the turbulent transport in the plasma-edge in fusion devices is of utmost importance in order to make precise predictions for future fusion devices. The plasma turbulence observed in linear devices shares many important features with the turbulence observed in the edge of fusion dev...... with simulations performed at different ionization levels, using a simple model for plasma interaction with neutrals. It is found that the steady state and the saturated state of the system bifurcates when the neutral interaction dominates the electron-ion collisions.......Understanding the turbulent transport in the plasma-edge in fusion devices is of utmost importance in order to make precise predictions for future fusion devices. The plasma turbulence observed in linear devices shares many important features with the turbulence observed in the edge of fusion...... devices, and are easier to diagnose due to lower temperatures and a better access to the plasma. In order to gain greater insight into this complex turbulent behavior, numerical simulations of plasma in a linear device are performed in this thesis. Here, a three-dimensional drift-fluid model is derived...
Numerical modeling of thermal conductive heating in fractured bedrock.
Baston, Daniel P; Falta, Ronald W; Kueper, Bernard H
2010-01-01
Numerical modeling was employed to study the performance of thermal conductive heating (TCH) in fractured shale under a variety of hydrogeological conditions. Model results show that groundwater flow in fractures does not significantly affect the minimum treatment zone temperature, except near the beginning of heating or when groundwater influx is high. However, fracture and rock matrix properties can significantly influence the time necessary to remove all liquid water (i.e., reach superheated steam conditions) in the treatment area. Low matrix permeability, high matrix porosity, and wide fracture spacing can contribute to boiling point elevation in the rock matrix. Consequently, knowledge of these properties is important for the estimation of treatment times. Because of the variability in boiling point throughout a fractured rock treatment zone and the absence of a well-defined constant temperature boiling plateau in the rock matrix, it may be difficult to monitor the progress of thermal treatment using temperature measurements alone. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.
A numerical model for meltwater channel evolution in glaciers
Directory of Open Access Journals (Sweden)
A. H. Jarosch
2012-04-01
Full Text Available Meltwater channels form an integral part of the hydrological system of a glacier. Better understanding of how meltwater channels develop and evolve is required to fully comprehend supraglacial and englacial meltwater drainage. Incision of supraglacial stream channels and subsequent roof closure by ice deformation has been proposed in recent literature as a possible englacial conduit formation process. Field evidence for supraglacial stream incision has been found in Svalbard and Nepal. In Iceland, where volcanic activity provides meltwater with temperatures above 0 °C, rapid enlargement of supraglacial channels has been observed. Supraglacial channels provide meltwater through englacial passages to the subglacial hydrological systems of big ice sheets, which in turn affects ice sheet motion and their contribution to eustatic sea level change. By coupling, for the first time, a numerical ice dynamic model to a hydraulic model which includes heat transfer, we investigate the evolution of meltwater channels and their incision behaviour. We present results for different, constant meltwater fluxes, different channel slopes, different meltwater temperatures, different melt rate distributions in the channel as well as temporal variations in meltwater flux. The key parameters governing incision rate and depth are channel slope, meltwater temperature loss to the ice and meltwater flux. Channel width and geometry are controlled by melt rate distribution along the channel wall. Calculated Nusselt numbers suggest that turbulent mixing is the main heat transfer mechanism in the meltwater channels studied.
Numerical modeling of accelerated, pre-compressed CTs in RACE
International Nuclear Information System (INIS)
Eddleman, J.L.; Hammer, J.H.; Hartman, C.W.; Logan, B.G.; McLean, H.S.; Molvik, A.W.
1990-01-01
Numerical modeling of accelerated compact toroids in the RACE experiment has motivated the development and application of a wide range of computational tools. These tools have included the zero-dimensional RAC code for fast parameter and design studies, and the two-dimensional, Eulerian, axisymmetric, magneto-hydrodynamic code, HAM, used to model plasma ring formation in magnetized plasma guns and acceleration in straight cylindrical electrodes. Extension of the RACE geometry to include converging conical electrodes motivated the development of a new two-dimensional, Lagrangian, axisymmetric, magnetohydrodynamic code, TRAC. The code includes optional initialization of the ring magnetic fields to a Taylor-equilibrium profile as well as self-consistent external capacitor bank driving circuit. Stability of initial field configurations with toroidal mode number > 0 may also be determined. The new code is particularly suited for predicting the behavior of accelerated plasma rings in arbitrarily shaped conical electrodes, since the restriction to a rectilinear mesh is removed. In particular, application of the code to the new pre-compression geometry in the RACE experiment is discussed and compared with experimental results
Evaluation of deconvolution modelling applied to numerical combustion
Mehl, Cédric; Idier, Jérôme; Fiorina, Benoît
2018-01-01
A possible modelling approach in the large eddy simulation (LES) of reactive flows is to deconvolve resolved scalars. Indeed, by inverting the LES filter, scalars such as mass fractions are reconstructed. This information can be used to close budget terms of filtered species balance equations, such as the filtered reaction rate. Being ill-posed in the mathematical sense, the problem is very sensitive to any numerical perturbation. The objective of the present study is to assess the ability of this kind of methodology to capture the chemical structure of premixed flames. For that purpose, three deconvolution methods are tested on a one-dimensional filtered laminar premixed flame configuration: the approximate deconvolution method based on Van Cittert iterative deconvolution, a Taylor decomposition-based method, and the regularised deconvolution method based on the minimisation of a quadratic criterion. These methods are then extended to the reconstruction of subgrid scale profiles. Two methodologies are proposed: the first one relies on subgrid scale interpolation of deconvolved profiles and the second uses parametric functions to describe small scales. Conducted tests analyse the ability of the method to capture the chemical filtered flame structure and front propagation speed. Results show that the deconvolution model should include information about small scales in order to regularise the filter inversion. a priori and a posteriori tests showed that the filtered flame propagation speed and structure cannot be captured if the filter size is too large.
Numerically modelling the large scale coronal magnetic field
Panja, Mayukh; Nandi, Dibyendu
2016-07-01
The solar corona spews out vast amounts of magnetized plasma into the heliosphere which has a direct impact on the Earth's magnetosphere. Thus it is important that we develop an understanding of the dynamics of the solar corona. With our present technology it has not been possible to generate 3D magnetic maps of the solar corona; this warrants the use of numerical simulations to study the coronal magnetic field. A very popular method of doing this, is to extrapolate the photospheric magnetic field using NLFF or PFSS codes. However the extrapolations at different time intervals are completely independent of each other and do not capture the temporal evolution of magnetic fields. On the other hand full MHD simulations of the global coronal field, apart from being computationally very expensive would be physically less transparent, owing to the large number of free parameters that are typically used in such codes. This brings us to the Magneto-frictional model which is relatively simpler and computationally more economic. We have developed a Magnetofrictional Model, in 3D spherical polar co-ordinates to study the large scale global coronal field. Here we present studies of changing connectivities between active regions, in response to photospheric motions.
International Nuclear Information System (INIS)
Olofsson, Isabelle; Fredriksson, Anders
2005-05-01
The Swedish Nuclear and Fuel Management Company (SKB) is conducting Preliminary Site Investigations at two different locations in Sweden in order to study the possibility of a Deep Repository for spent fuel. In the frame of these Site Investigations, Site Descriptive Models are achieved. These products are the result of an interaction of several disciplines such as geology, hydrogeology, and meteorology. The Rock Mechanics Site Descriptive Model constitutes one of these models. Before the start of the Site Investigations a numerical method using Discrete Fracture Network (DFN) models and the 2D numerical software UDEC was developed. Numerical simulations were the tool chosen for applying the theoretical approach for characterising the mechanical rock mass properties. Some shortcomings were identified when developing the methodology. Their impacts on the modelling (in term of time and quality assurance of results) were estimated to be so important that the improvement of the methodology with another numerical tool was investigated. The theoretical approach is still based on DFN models but the numerical software used is 3DEC. The main assets of the programme compared to UDEC are an optimised algorithm for the generation of fractures in the model and for the assignment of mechanical fracture properties. Due to some numerical constraints the test conditions were set-up in order to simulate 2D plane strain tests. Numerical simulations were conducted on the same data set as used previously for the UDEC modelling in order to estimate and validate the results from the new methodology. A real 3D simulation was also conducted in order to assess the effect of the '2D' conditions in the 3DEC model. Based on the quality of the results it was decided to update the theoretical model and introduce the new methodology based on DFN models and 3DEC simulations for the establishment of the Rock Mechanics Site Descriptive Model. By separating the spatial variability into two parts, one
Gras, Laure-Lise; Laporte, Sébastien; Viot, Philippe; Mitton, David
2014-10-01
In models developed for impact biomechanics, muscles are usually represented with one-dimensional elements having active and passive properties. The passive properties of muscles are most often obtained from experiments performed on animal muscles, because limited data on human muscle are available. The aim of this study is thus to characterize the passive response of a human muscle in tension. Tensile tests at different strain rates (0.0045, 0.045, and 0.45 s⁻¹) were performed on 10 extensor carpi ulnaris muscles. A model composed of a nonlinear element defined with an exponential law in parallel with one or two Maxwell elements and considering basic geometrical features was proposed. The experimental results were used to identify the parameters of the model. The results for the first- and second-order model were similar. For the first-order model, the mean parameters of the exponential law are as follows: Young's modulus E (6.8 MPa) and curvature parameter α (31.6). The Maxwell element mean values are as follows: viscosity parameter η (1.2 MPa s) and relaxation time τ (0.25 s). Our results provide new data on a human muscle tested in vitro and a simple model with basic geometrical features that represent its behavior in tension under three different strain rates. This approach could be used to assess the behavior of other human muscles. © IMechE 2014.
Wind field near complex terrain using numerical weather prediction model
Chim, Kin-Sang
The PennState/NCAR MM5 model was modified to simulate an idealized flow pass through a 3D obstacle in the Micro- Alpha Scale domain. The obstacle used were the idealized Gaussian obstacle and the real topography of Lantau Island of Hong Kong. The Froude number under study is ranged from 0.22 to 1.5. Regime diagrams for both the idealized Gaussian obstacle and Lantau island were constructed. This work is divided into five parts. The first part is the problem definition and the literature review of the related publications. The second part briefly discuss as the PennState/NCAR MM5 model and a case study of long- range transport is included. The third part is devoted to the modification and the verification of the PennState/NCAR MM5 model on the Micro-Alpha Scale domain. The implementation of the Orlanski (1976) open boundary condition is included with the method of single sounding initialization of the model. Moreover, an upper dissipative layer, Klemp and Lilly (1978), is implemented on the model. The simulated result is verified by the Automatic Weather Station (AWS) data and the Wind Profiler data. Four different types of Planetary Boundary Layer (PBL) parameterization schemes have been investigated in order to find out the most suitable one for Micro-Alpha Scale domain in terms of both accuracy and efficiency. Bulk Aerodynamic type of PBL parameterization scheme is found to be the most suitable PBL parameterization scheme. Investigation of the free- slip lower boundary condition is performed and the simulated result is compared with that with friction. The fourth part is the use of the modified PennState/NCAR MM5 model for an idealized flow simulation. The idealized uniform flow used is nonhydrostatic and has constant Froude number. Sensitivity test is performed by varying the Froude number and the regime diagram is constructed. Moreover, nondimensional drag is found to be useful for regime identification. The model result is also compared with the analytic
Numerical Modeling of the 2014 Oso, Washington, Landslide.
George, D. L.; Iverson, R. M.
2014-12-01
Numerical simulations of alternative scenarios that could have transpired during the Oso, Washington, landslide of 22 March 2014 provide insight into factors responsible for the landslide's devastating high-speed runout.We performed these simulations using D-Claw, a numerical model we recently developed to simulate landslide and debris-flow motion from initiation to deposition. D-Claw solves a hyperbolic system of five partial differential equations that describe simultaneous evolution of the thickness,solid volume fraction, basal pore-fluid pressure, and two components of momentum of the moving mass. D-Claw embodies the concept ofstate-dependent dilatancy, which causes the solid volume fraction m to evolve toward a value that is equilibrated to the ambient stress state andshear rate. As the value of m evolves, basal pore-fluid pressure coevolves,and thereby causes an evolution in frictional resistance to motion. Our Oso simulations considered alternative scenarios in which values of all model parameters except the initial solid volume fraction m0 were held constant.These values were: basal friction angle = 36°; static critical-state solidvolume fraction = 0.64; initial sediment permeability = 10-8 m2; pore-fluid density = 1100 kg/m3; sediment grain density = 2700 kg/m3; pore-fluid viscosity = 0.005 Pa-s; and dimensionless sediment compressibility coefficient = 0.03. Simulations performed using these values and m0 = 0.62 produced widespread landslide liquefaction, runaway acceleration, andlandslide runout distances, patterns and speeds similar to those observed or inferred for the devastating Oso event. Alternative simulations that usedm0 = 0.64 produced a much slower landslide that did not liquefy and that traveled only about 100 m before stopping. This relatively benign behavioris similar to that of several landslides at the Oso site prior to 2014. Our findings illustrate a behavioral bifurcation that is highly sensitive to the initial solid volume fraction
Numerical modeling of the Indo-Australian intraplate deformation
Brandon, Vincent; Royer, Jean-Yves
2014-05-01
The Indo-Australian plate is perhaps the best example of wide intraplate deformation within an oceanic plate. The deformation is expressed by an unusual level of intraplate seismicity, including magnitude Mw > 8 events, large-scale folding and deep faulting of the oceanic lithosphere and reactivation of extinct fracture zones. The deformation pattern and kinematic data inversions suggest that the Indo-Australian plate can be viewed as a composite plate made of three rigid component plates - India, Capricorn, Australia - separated by wide and diffuse boundaries undergoing either extensional or compressional deformation. We tested this model using the SHELLS numerical code (Kong & Bird, 1995). The Indo-Australian plate is modeled by a mesh of 5281 spherical triangular finite elements. Mesh edges parallel the major extinct fracture zones so that they can be reactivated by reducing their friction rates. Strength of the plate is defined by the age of the lithosphere and seafloor topography. Model boundary conditions are only defined by the plate velocities predicted by the rotation vectors between rigid components of the Indo-Australian plate and their neighboring plates. Since the mesh limits all belong to rigid plates with fully defined Euler vectors, no conditions are imposed on the location, extent and limits of the diffuse and deforming zones. Using MORVEL plate velocities (DeMets et al., 2010), predicted deformation patterns are very consistent with that observed. Pre-existing structures of the lithosphere play an important role in the intraplate deformation and its distribution. The Chagos Bank focuses most of the extensional deformation between the Indian and Capricorn plates. Agreement between models and observation improves by weakening fossil fracture zones relative to the surrounding crust; however only limited sections of FZ's accommodate deformation. The reactivation of the Eocene FZ's in the Central Indian Basin (CIB) and Wharton Basin (WB) explains the
Numerical modelling of volatiles in the deep mantle
Eichheimer, Philipp; Thielmann, Marcel; Golabek, Gregor J.
2017-04-01
The transport and storage of water in the mantle significantly affects several material properties of mantle rocks and thus water plays a key role in a variety of geodynamical processes (tectonics, magmatism etc.). The processes driving transport and circulation of H2O in subduction zones remain a debated topic. Geological and seismological observations suggest different inflow mechanisms of water e.g. slab bending, thermal cracking and serpentinization (Faccenda et al., 2009; Korenaga, 2017), followed by dehydration of the slab. On Earth both shallow and steep subduction can be observed (Li et al., 2011). However most previous models (van Keken et al., 2008; Wilson et al., 2014) did not take different dip angles and subduction velocities of slabs into account. To which extent these parameters and processes influence the inflow of water still remains unclear. We present 2D numerical models simulating the influence of the various water inflow mechanisms on the mantle with changing dip angle and subduction velocity of the slab over time. The results are used to make predictions regarding the rheological behavior of the mantle wedge, dehydration regimes and volcanism at the surface. References: van Keken, P. E., et al. A community benchmark for subduction zone modeling. Phys. Earth Planet. Int. 171, 187-197 (2008). Faccenda, M., T.V. Gerya, and L. Burlini. Deep slab hydration induced by bending-related variations in tectonic pressure. Nat. Geosci. 2, 790-793 (2009). Korenaga, J. On the extent of mantle hydration caused by plate bending. Earth Planet. Sci. Lett. 457, 1-9 (2017). Wilson, C. R., et al. Fluid flow in subduction zones: The role of solid rheology and compaction pressure. Earth Planet. Sci. Lett. 401, 261-274 (2014). Li, Z. H., Z. Q. Xu, and T. V. Gerya. Flat versus steep subduction: Contrasting modes for the formation and exhumation of high- to ultrahigh-pressure rocks in continental collision zones. Earth Planet. Sci. Lett. 301, 65-77 (2011).
Ambient vibrations of unstable rock slopes - insights from numerical modeling
Burjanek, Jan; Kleinbrod, Ulrike; Fäh, Donat
2017-04-01
The recent events in Nepal (2015 M7.8 Gorkha) and New Zealand (2016 M7.8 Kaikoura) highlighted the importance of earthquake-induced landslides, which caused significant damages. Moreover, landslide created dams present a potential developing hazard. In order to reduce the costly consequences of such events it is important to detect and characterize earthquake susceptible rock slope instabilities before an event, and to take mitigation measures. For the characterisation of instable slopes, acquisition of ambient vibrations might be a new alternative to the already existing methods. We present both observations and 3D numerical simulations of the ambient vibrations of unstable slopes. In particular, models of representative real sites have been developed based on detailed terrain mapping and used for the comparison between synthetics and observations. A finite-difference code has been adopted for the seismic wave propagation in a 3D inhomogeneous visco-elastic media with irregular free surface. It utilizes a curvilinear grid for a precise modeling of curved topography and local mesh refinement to make computational mesh finer near the free surface. Topographic site effects, controlled merely by the shape of the topography, do not explain the observed seismic response. In contrast, steeply-dipping compliant fractures have been found to play a key role in fitting observations. Notably, the synthetized response is controlled by inertial mass of the unstable rock, and by stiffness, depth and network density of the fractures. The developed models fit observed extreme amplification levels (factors of 70!) and show directionality as well. This represents a possibility to characterize slope structure and infer depth or volume of the slope instability from the ambient noise recordings in the future.
Supporting Current Energy Conversion Projects through Numerical Modeling
James, S. C.; Roberts, J.
2016-02-01
The primary goals of current energy conversion (CEC) technology being developed today are to optimize energy output and minimize environmental impact. CEC turbines generate energy from tidal and current systems and create wakes that interact with turbines located downstream of a device. The placement of devices can greatly influence power generation and structural reliability. CECs can also alter the environment surrounding the turbines, such as flow regimes, sediment dynamics, and water quality. These alterations pose potential stressors to numerous environmental receptors. Software is needed to investigate specific CEC sites to simulate power generation and hydrodynamic responses of a flow through a CEC turbine array so that these potential impacts can be evaluated. Moreover, this software can be used to optimize array layouts that yield the least changes to the environmental (i.e., hydrodynamics, sediment dynamics, and water quality). Through model calibration exercises, simulated wake profiles and turbulence intensities compare favorably to the experimental data and demonstrate the utility and accuracy of a fast-running tool for future siting and analysis of CEC arrays in complex domains. The Delft3D modeling tool facilitates siting of CEC projects through optimization of array layouts and evaluation of potential environmental effect all while provide a common "language" for academics, industry, and regulators to be able to discuss the implications of marine renewable energy projects. Given the enormity of any full-scale marine renewable energy project, it necessarily falls to modeling to evaluate how array operations must be addressed in an environmental impact statement in a way that engenders confidence in the assessment of the CEC array to minimize environmental effects.
Numerical Modeling of Large-Scale Rocky Coastline Evolution
Limber, P.; Murray, A. B.; Littlewood, R.; Valvo, L.
2008-12-01
Seventy-five percent of the world's ocean coastline is rocky. On large scales (i.e. greater than a kilometer), many intertwined processes drive rocky coastline evolution, including coastal erosion and sediment transport, tectonics, antecedent topography, and variations in sea cliff lithology. In areas such as California, an additional aspect of rocky coastline evolution involves submarine canyons that cut across the continental shelf and extend into the nearshore zone. These types of canyons intercept alongshore sediment transport and flush sand to abyssal depths during periodic turbidity currents, thereby delineating coastal sediment transport pathways and affecting shoreline evolution over large spatial and time scales. How tectonic, sediment transport, and canyon processes interact with inherited topographic and lithologic settings to shape rocky coastlines remains an unanswered, and largely unexplored, question. We will present numerical model results of rocky coastline evolution that starts with an immature fractal coastline. The initial shape is modified by headland erosion, wave-driven alongshore sediment transport, and submarine canyon placement. Our previous model results have shown that, as expected, an initial sediment-free irregularly shaped rocky coastline with homogeneous lithology will undergo smoothing in response to wave attack; headlands erode and mobile sediment is swept into bays, forming isolated pocket beaches. As this diffusive process continues, pocket beaches coalesce, and a continuous sediment transport pathway results. However, when a randomly placed submarine canyon is introduced to the system as a sediment sink, the end results are wholly different: sediment cover is reduced, which in turn increases weathering and erosion rates and causes the entire shoreline to move landward more rapidly. The canyon's alongshore position also affects coastline morphology. When placed offshore of a headland, the submarine canyon captures local sediment
Numerical Modeling of Hydrokinetic Turbines and their Environmental Effects
Javaherchi, T.; Seydel, J.; Aliseda, A.
2010-12-01
The search for predictable renewable energy has led research into marine hydrokinetic energy. Electricity can be generated from tidally-induced currents through turbines located in regions of high current speed and relatively low secondary flow intensity. Although significant technological challenges exist, the main obstacle in the development and commercial deployment of marine hydrokinetic (MHK) turbines is the uncertainty in the environmental effect of devices. The velocity deficit in the turbulent wake of the turbine might enhance the sedimentation process of suspended particles in the water column and lead to deposition into artificial patterns that alter the benthic ecosystem. Pressure fluctuations across turbine blades and in blade tip vortices can damage internal organs of marine species as they swim through the device. These are just a few examples of the important potential environmental effects of MHK turbines that need to be addressed and investigated a priori before pilot and large scale deployment. We have developed a hierarchy of numerical models to simulate the turbulent wake behind a well characterized two bladed turbine. The results from these models (Sliding Mesh, Rotating Reference Frame, Virtual Blade Model and Actuator Disk Model) have been validated and are been used to investigate the efficiency and physical changes introduced in the environment by single or multiple MHK turbines. We will present results from sedimenting particles and model juvenile fish, with relative densities of 1.2 and 0.95, respectively. The settling velocity and terminal location on the bottom of the tidal channel is computed and compared to the simulated flow in a channel without turbines. We have observed an enhanced sedimentation, and we will quantify the degree of enhancement and the parameter range within which it is significant. For the slightly buoyant particles representing fish, the pressure history is studied statistically with particular attention to the
Miniaturized inertial impactor for personal airborne particulate monitoring: Numerical model
Cortelezzi, Luca; Pasini, Silvia; Bianchi, Elena; Dubini, Gabriele
2017-11-01
The rising level of fine particle matter's (PM10, PM2.5 and PM1) pollution in the world has increased the interest in developing portable personal air-qualitity monitoring systems. To answer this need, we conceived a miniaturized inertial impactor. The development of such an impactor becomes more challenging as the diameter of the particles to be collected becomes smaller, since the velocities required to induce the impact of finer particulate matter become higher. To overcome these challenges, we modeled numerically the fluid dynamics and particles transport within the impactor. Our simulations show that the fluid flow within the impactor becomes unstable as the Reynolds number is increased to capture finer particles. Furthermore, the onset of these instabilities depends not only on the Reynolds number but also on the geometry of the impactor. The unsteady flow within the impactor influences the trajectories of the particles to be collected, especially the smaller particles. The particles trajectories shows that the impaction location varies substantially as the Reynolds number increases and, consequently, the efficiency of the impactor deteriorates. Finally, we optimize the design of our impactor to maximize its collection efficiency. CARIPLO Fundation - project MINUTE (Grant No. 2011-2118).
Two-dimensional numerical modeling of the cosmic ray storm
International Nuclear Information System (INIS)
Kadokura, A.; Nishida, A.
1986-01-01
A numerical model of the cosmic ray storm in the two-dimensional heliosphere is constructed incorporating the drift effect. We estimate the effect of a flare-associated interplanetary shock and the disturbed region behind it (characterized by enhancement in velocity and magnetic field, and decrease in mean free path) on the density and anisotropy of cosmic rays in the heliosphere. As the disturbance propagates outward, a density enhancement appears on the front side, and a density depression region is produced on the rear side. The effect of drift on the cosmic ray storm appears most clearly in the higher-latitude region. For the parallel (antiparallel) state of the solar magnetic field which corresponds to the pre(post-) 1980 period, the density in the higher-latitude region decreases (increases) before the shock arrival. The maximum density depression near the earth for the parallel state is greater than for the antiparallel state, and the energy spectrum of the density depression in percentage is softer for the parallel state than for the antiparallel state. Prior to the arrival of the shock, the phase of solar diurnal anisotropy begins to shift to the earlier hours, and its amplitude becomes greater for both polarity states. North-south anisotropy also becomes greater because of the enhanced drift for both polarity states
Numerical modeling of NI-monitored 3D infiltration experiment
Dohnal, Michal; Dusek, Jaromir; Snehota, Michal; Sacha, Jan; Vogel, Tomas; Votrubova, Jana
2014-05-01
It is well known that the temporal changes of saturated hydraulic conductivity caused by the occurrence of air phase discontinuities often play an important role in water flow and solute transport experiments. In the present study, a series of infiltration-outflow experiments was conducted to test several working hypotheses about the mechanism of air phase trapping. The experiments were performed on a porous sample with artificial internal structure, using three sandy materials with contrasting hydraulic properties. The sample was axially symmetric with continuous preferential pathways and separate porous matrix blocks (the sample was 3.4 cm in diameter and 8.8 cm high). The infiltration experiments were monitored by neutron imaging (NI). The NI data were then used to quantify the water content of the selected sample regions. The flow regime in the sample was studied using a three-dimensional model based on Richards' equation. The equation was solved by the finite element method. The results of the numerical simulations of the infiltration experiments were compared with the measured outflow rates and with the spatial distribution of water content determined by NI. The research was supported by the Czech Science Foundation Project No. 14-03691S.
[New approaches in pharmacology: numerical modelling and simulation].
Boissel, Jean-Pierre; Cucherat, Michel; Nony, Patrice; Dronne, Marie-Aimée; Kassaï, Behrouz; Chabaud, Sylvie
2005-01-01
The complexity of pathophysiological mechanisms is beyond the capabilities of traditional approaches. Many of the decision-making problems in public health, such as initiating mass screening, are complex. Progress in genomics and proteomics, and the resulting extraordinary increase in knowledge with regard to interactions between gene expression, the environment and behaviour, the customisation of risk factors and the need to combine therapies that individually have minimal though well documented efficacy, has led doctors to raise new questions: how to optimise choice and the application of therapeutic strategies at the individual rather than the group level, while taking into account all the available evidence? This is essentially a problem of complexity with dimensions similar to the previous ones: multiple parameters with nonlinear relationships between them, varying time scales that cannot be ignored etc. Numerical modelling and simulation (in silico investigations) have the potential to meet these challenges. Such approaches are considered in drug innovation and development. They require a multidisciplinary approach, and this will involve modification of the way research in pharmacology is conducted.
Numerical modelling of GPR electromagnetic fields for locating burial sites
Directory of Open Access Journals (Sweden)
Carcione José M.
2017-01-01
Full Text Available Ground-penetrating radar (GPR is commonly used for locating burial sites. In this article, we acquired radargrams at a site where a domestic pig cadaver was buried. The measurements were conducted with the ProEx System GPR manufactured by the Swedish company Mala Geoscience with an antenna of 500MHz. The event corresponding to the pig can be clearly seen in the measurements. In order to improve the interpretation, the electromagnetic field is compared to numerical simulations computed with the pseudo-spectral Fourier method. A geological model has been defined on the basis of assumed electromagnetic properties (permittivity, conductivity and magnetic permeability. The results, when compared with the GPR measurements, show a dissimilar amplitude behaviour, with a stronger reflection event from the bottom of the pit. We have therefore performed another simulation by decreasing the electrical conductivity of the body very close to that of air. The comparison improved, showing more reflections, which could be an indication that the body contains air or has been degraded to a certain extent that the electrical resistivity has greatly increased.
Classroom Talk for Rigorous Reading Comprehension Instruction
Wolf, Mikyung Kim; Crosson, Amy C.; Resnick, Lauren B.
2004-01-01
This study examined the quality of classroom talk and its relation to academic rigor in reading-comprehension lessons. Additionally, the study aimed to characterize effective questions to support rigorous reading comprehension lessons. The data for this study included 21 reading-comprehension lessons in several elementary and middle schools from…
Contribution to the numerical modeling of inertial confinement fusion
International Nuclear Information System (INIS)
Maire, P.H.
2011-02-01
This work was realized by writing the CHIC code, which is a software for designing and restoring experience in the field of inertial confinement fusion. The theoretical model describing the implosion of a laser target is a system of partial differential equations in the center of which is the Euler equations written in Lagrangian formalism, coupled with diffusion equations modeling the nonlinear transport of energy by electrons and photons. After a brief review of the physical context, we describe two novel methods which constitute the backbone of the CHIC code. These are 2 high-order finite volume schemes respectively dedicated to solving the equations of Lagrangian hydrodynamics and the anisotropic diffusion equations on bi-dimensional unstructured grids. The first scheme, called EUCCLHYD (Explicit Unstructured Lagrangian Hydrodynamics), solves the equations of gas dynamics on a moving mesh that moves at the speed of light. It is obtained from a general formalism based on the concept of sub-cell forces. In this context, the numerical fluxes are expressed in terms of the sub-cell force and the nodal velocity. Their determination is based on 3 basic principles: geometric compatibility between the movement of nodes and the volume change of mesh (geometric conservation law), compatibility with the second law of thermodynamics and conservation of total energy and momentum. The high-order extension is performed using a method based on solving a generalized Riemann problem in the acoustic approximation. The second scheme, called CCLAD (Cell-Centered Lagrangian Diffusion), solves the anisotropic heat equation. The corresponding discretization relies on a discrete variational formulation based on the sub-cell that allows to build a multipoint approximation of heat flux. This high-order discretization makes possible the resolution of the equations of anisotropic diffusion with satisfactory accuracy on highly distorted Lagrangian meshes. (author)
Numerical modelling of pulsation and convection in cepheids
International Nuclear Information System (INIS)
Mundprecht, E.
2011-01-01
In order to simulate the pulsation convection coupling in a Cepheid the ANTARES-code was equipped with a polar and moving grid. The numerical cost of a fully parallelized, sufficiently large, and fully resolved section would be immense. Thus it was not only necessary to find a suitable model, but also save to costs for parallelisation and grid refinement. The equations governing the hydrodynamics were derived for this particular grid and implemented in the code. The grey short characteristics method for the radiative transfer equation was also adjusted. Different methods of parallelisation for the radiative transfer were tested. Abstract Within ANTARES shocks are treated with an essentially non oscillatory (ENO) scheme with Marquina flux splitting. As this method is only valid for grids that are equidistant or uniformly stretched in all directions two differnt sets of ENO-coefficients were implemented and tested. It was found that the traditional approach is indeed no longer valid and the system is not conservative when the original set of coefficients is used. In the upper or hydrogen ionisation zone the gradient of density, temperature etc. is very steep, therefore a finer resolution with a minimum of additional time steps is needed. In order to resolve these few points a co-moving grid refinement was developed. Simulations in one and two dimensions were performed, a comparison between them helps to better understand the effects of convection on the e.c. light curve. Analysis of the fluxes and the work integral was done for the helium ionisation zone. The effects of subgrid modelling were tested on the hydrogen convection zone and compared with a resolved simulation of this zone. (author) [de
Numerical Experiments Based on the Catastrophe Model of Solar Eruptions
Xie, X. Y.; Ziegler, U.; Mei, Z. X.; Wu, N.; Lin, J.
2017-11-01
On the basis of the catastrophe model developed by Isenberg et al., we use the NIRVANA code to perform the magnetohydrodynamics (MHD) numerical experiments to look into various behaviors of the coronal magnetic configuration that includes a current-carrying flux rope used to model the prominence levitating in the corona. These behaviors include the evolution in equilibrium heights of the flux rope versus the change in the background magnetic field, the corresponding internal equilibrium of the flux rope, dynamic properties of the flux rope after the system loses equilibrium, as well as the impact of the referential radius on the equilibrium heights of the flux rope. In our calculations, an empirical model of the coronal density distribution given by Sittler & Guhathakurta is used, and the physical diffusion is included. Our experiments show that the deviation of simulations in the equilibrium heights from the theoretical results exists, but is not apparent, and the evolutionary features of the two results are similar. If the flux rope is initially locate at the stable branch of the theoretical equilibrium curve, the flux rope will quickly reach the equilibrium position in the simulation after several rounds of oscillations as a result of the self-adjustment of the system; and the flux rope lose the equilibrium if the initial location of the flux rope is set at the critical point on the theoretical equilibrium curve. Correspondingly, the internal equilibrium of the flux rope can be reached as well, and the deviation from the theoretical results is somewhat apparent since the approximation of the small radius of the flux rope is lifted in our experiments, but such deviation does not affect the global equilibrium in the system. The impact of the referential radius on the equilibrium heights of the flux rope is consistent with the prediction of the theory. Our calculations indicate that the motion of the flux rope after the loss of equilibrium is consistent with which
3-D Numerical Modelling of Oblique Continental Collisions with ASPECT
Karatun, L.; Pysklywec, R.
2017-12-01
Among the fundamental types of tectonic plate boundaries, continent-continent collision is least well understood. Deformation of the upper and middle crustal layers can be inferred from surface structures and geophysical imaging, but the fate of lower crustal rocks and mantle lithosphere is not well resolved. Previous research suggests that shortening of mantle lithosphere generally may be occurring by either: 1) a distributed thickening with a formation of a Raleigh-Tailor (RT) type instability (possibly accompanied with lithospheric folding); or 2) plate-like subduction, which can be one- or two-sided, with or without delamination and slab break-off; a combination of both could be taking place too. 3-D features of the orogens such as along-trench material transfer, bounding subduction zones can influence the evolution of the collision zone significantly. The current study was inspired by South Island of New Zealand - a young collision system where a block of continental crust is being shortened by the relative Australian-Pacific plate motion. The collision segment of the plate boundary is relatively small ( 800 km), and is bounded by oppositely verging subduction zones to the North and South. Here, we present results of 3-D forward numerical modelling of continental collision to investigate some of these processes. To conduct the simulations, we used ASPECT - a highly parallel community-developed code based on the Finite Element method. Model setup for three different sets of models featured 2-D vertical across strike, 3-D with periodic front and back walls, and 3-D with open front and back walls, with velocities prescribed on the left and right faces. We explored the importance of values of convergent velocity, strike-slip velocity and their ratio, which defines the resulting velocity direction relative to the plate boundary (obliquity). We found that higher strike-slip motion promotes strain localization, weakens the lithosphere close to the plate boundary and
Numerical modeling of Thermal Response Tests in Energy Piles
Franco, A.; Toledo, M.; Moffat, R.; Herrera, P. A.
2013-05-01
conductivity of the soil is the most determinant parameter that affects the estimated thermal conductivity. For example, we observed differences of up to 50% from the expected value at the end of 100 hours of simulation for values of thermal conductivity of the soil in the range of 1 to 6 W/mK. Additionally, we observed that the results of the synthetic TRT depend upon several other parameters such as the boundary conditions used to model the interaction of the top face of the pile with the surrounding media. For example, Simulations with a constant temperature boundary condition tended to overestimate the total thermal conductivity of the whole system. This analysis demonstrates that numerical modeling is a useful tool to model energy pile systems and to interpret and design tests to evaluate their performance. Furthermore, it also reveals that the results of thermal response tests interpreted with analytical models must be evaluated with care for the assessment of the potential of low enthalpy systems, because their results depend upon a variety of factors which are neglected in the analytical models.
Zhu, Guangpu
2018-04-17
In this paper, we consider the numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow. The nonlinearly coupled model consists of two Cahn-Hilliard type equations and incompressible Navier-Stokes equations. Using the Invariant Energy Quadratization (IEQ) approach, the governing system is transformed into an equivalent form, which allows the nonlinear potentials to be treated efficiently and semi-explicitly. we construct a first and a second-order time marching schemes, which are extremely efficient and easy-to-implement, for the transformed governing system. At each time step, the schemes involve solving a sequence of linear elliptic equations, and computations of phase variables, velocity and pressure are totally decoupled. We further establish a rigorous proof of unconditional energy stability for the semi-implicit schemes. Numerical results in both two and three dimensions are obtained, which demonstrate that the proposed schemes are accurate, efficient and unconditionally energy stable. Using our schemes, we investigate the effect of surfactants on droplet deformation and collision under a shear flow. The increase of surfactant concentration can enhance droplet deformation and inhibit droplet coalescence.
Zhu, Guangpu; Kou, Jisheng; Sun, Shuyu; Yao, Jun; Li, Aifen
2018-01-01
In this paper, we consider the numerical approximation of a binary fluid-surfactant phase field model of two-phase incompressible flow. The nonlinearly coupled model consists of two Cahn-Hilliard type equations and incompressible Navier-Stokes equations. Using the Invariant Energy Quadratization (IEQ) approach, the governing system is transformed into an equivalent form, which allows the nonlinear potentials to be treated efficiently and semi-explicitly. we construct a first and a second-order time marching schemes, which are extremely efficient and easy-to-implement, for the transformed governing system. At each time step, the schemes involve solving a sequence of linear elliptic equations, and computations of phase variables, velocity and pressure are totally decoupled. We further establish a rigorous proof of unconditional energy stability for the semi-implicit schemes. Numerical results in both two and three dimensions are obtained, which demonstrate that the proposed schemes are accurate, efficient and unconditionally energy stable. Using our schemes, we investigate the effect of surfactants on droplet deformation and collision under a shear flow. The increase of surfactant concentration can enhance droplet deformation and inhibit droplet coalescence.
Carrillo, J. A.; Desvillettes, L.; Fellner, K.
2009-01-01
Weak solutions of the spatially inhomogeneous (diffusive) Aizenmann-Bak model of coagulation-breakup within a bounded domain with homogeneous Neumann boundary conditions are shown to converge, in the fast reaction limit, towards local equilibria determined by their mass. Moreover, this mass is the solution of a nonlinear diffusion equation whose nonlinearity depends on the (size-dependent) diffusion coefficient. Initial data are assumed to have integrable zero order moment and square integrable first order moment in size, and finite entropy. In contrast to our previous result [5], we are able to show the convergence without assuming uniform bounds from above and below on the number density of clusters. © Taylor & Francis Group, LLC.
Carrillo, J. A.
2009-10-30
Weak solutions of the spatially inhomogeneous (diffusive) Aizenmann-Bak model of coagulation-breakup within a bounded domain with homogeneous Neumann boundary conditions are shown to converge, in the fast reaction limit, towards local equilibria determined by their mass. Moreover, this mass is the solution of a nonlinear diffusion equation whose nonlinearity depends on the (size-dependent) diffusion coefficient. Initial data are assumed to have integrable zero order moment and square integrable first order moment in size, and finite entropy. In contrast to our previous result [5], we are able to show the convergence without assuming uniform bounds from above and below on the number density of clusters. © Taylor & Francis Group, LLC.
Energy Technology Data Exchange (ETDEWEB)
Follin, Sven (SF GeoLogic AB, Taeby (Sweden)); Hartley, Lee; Jackson, Peter; Roberts, David (Serco TAP (United Kingdom)); Marsic, Niko (Kemakta Konsult AB, Stockholm (Sweden))
2008-05-15
Three versions of a site descriptive model (SDM) have been completed for the Forsmark area. Version 0 established the state of knowledge prior to the start of the site investigation programme. Version 1.1 was essentially a training exercise and was completed during 2004. Version 1.2 was a preliminary site description and concluded the initial site investigation work (ISI) in June 2005. Three modelling stages are planned for the complete site investigation work (CSI). These are labelled stage 2.1, 2.2 and 2.3, respectively. An important component of each of these stages is to address and continuously try to resolve discipline-specific uncertainties of importance for repository engineering and safety assessment. Stage 2.1 included an updated geological model for Forsmark and aimed to provide a feedback from the modelling working group to the site investigation team to enable completion of the site investigation work. Stage 2.2 described the conceptual understanding and the numerical modelling of the bedrock hydrogeology in the Forsmark area based on data freeze 2.2. The present report describes the modelling based on data freeze 2.3, which is the final data freeze in Forsmark. In comparison, data freeze 2.3 is considerably smaller than data freeze 2.2. Therefore, stage 2.3 deals primarily with model confirmation and uncertainty analysis, e.g. verification of important hypotheses made in stage 2.2 and the role of parameter uncertainty in the numerical modelling. On the whole, the work reported here constitutes an addendum to the work reported in stage 2.2. Two changes were made to the CONNECTFLOW code in stage 2.3. These serve to: 1) improve the representation of the hydraulic properties of the regolith, and 2) improve the conditioning of transmissivity of the deformation zones against single-hole hydraulic tests. The changes to the modelling of the regolith were made to improve the consistency with models made with the MIKE SHE code, which involved the introduction
Molnar, I. L.; Krol, M.; Mumford, K. G.
2017-12-01
Developing numerical models for subsurface thermal remediation techniques - such as Electrical Resistive Heating (ERH) - that include multiphase processes such as in-situ water boiling, gas production and recovery has remained a significant challenge. These subsurface gas generation and recovery processes are driven by physical phenomena such as discrete and unstable gas (bubble) flow as well as water-gas phase mass transfer rates during bubble flow. Traditional approaches to multiphase flow modeling soil remain unable to accurately describe these phenomena. However, it has been demonstrated that Macroscopic Invasion Percolation (MIP) can successfully simulate discrete and unstable gas transport1. This has lead to the development of a coupled Electro Thermal-MIP Model2 (ET-MIP) capable of simulating multiple key processes in the thermal remediation and gas recovery process including: electrical heating of soil and groundwater, water flow, geological heterogeneity, heating-induced buoyant flow, water boiling, gas bubble generation and mobilization, contaminant mass transport and removal, and additional mechanisms such as bubble collapse in cooler regions. This study presents the first rigorous validation of a coupled ET-MIP model against two-dimensional water boiling and water/NAPL co-boiling experiments3. Once validated, the model was used to explore the impact of water and co-boiling events and subsequent gas generation and mobilization on ERH's ability to 1) generate, expand and mobilize gas at boiling and NAPL co-boiling temperatures, 2) efficiently strip contaminants from soil during both boiling and co-boiling. In addition, a quantification of the energy losses arising from steam generation during subsurface water boiling was examined with respect to its impact on the efficacy of thermal remediation. While this study specifically targets ERH, the study's focus on examining the fundamental mechanisms driving thermal remediation (e.g., water boiling) renders
Assessing numerical methods used in nuclear aerosol transport models
International Nuclear Information System (INIS)
McDonald, B.H.
1987-01-01
Several computer codes are in use for predicting the behaviour of nuclear aerosols released into containment during postulated accidents in water-cooled reactors. Each of these codes uses numerical methods to discretize and integrate the equations that govern the aerosol transport process. Computers perform only algebraic operations and generate only numbers. It is in the numerical methods that sense can be made of these numbers and where they can be related to the actual solution of the equations. In this report, the numerical methods most commonly used in the aerosol transport codes are examined as special cases of a general solution procedure, the Method of Weighted Residuals. It would appear that the numerical methods used in the codes are all capable of producing reasonable answers to the mathematical problem when used with skill and care. 27 refs
Rigorous vector wave propagation for arbitrary flat media
Bos, Steven P.; Haffert, Sebastiaan Y.; Keller, Christoph U.
2017-08-01
Precise modelling of the (off-axis) point spread function (PSF) to identify geometrical and polarization aberrations is important for many optical systems. In order to characterise the PSF of the system in all Stokes parameters, an end-to-end simulation of the system has to be performed in which Maxwell's equations are rigorously solved. We present the first results of a python code that we are developing to perform multiscale end-to-end wave propagation simulations that include all relevant physics. Currently we can handle plane-parallel near- and far-field vector diffraction effects of propagating waves in homogeneous isotropic and anisotropic materials, refraction and reflection of flat parallel surfaces, interference effects in thin films and unpolarized light. We show that the code has a numerical precision on the order of 10-16 for non-absorbing isotropic and anisotropic materials. For absorbing materials the precision is on the order of 10-8. The capabilities of the code are demonstrated by simulating a converging beam reflecting from a flat aluminium mirror at normal incidence.
NUMERICAL MODELLING OF THE SOIL BEHAVIOUR BY USING NEWLY DEVELOPED ADVANCED MATERIAL MODEL
Directory of Open Access Journals (Sweden)
Jan Veselý
2017-02-01
Full Text Available This paper describes a theoretical background, implementation and validation of the newly developed Jardine plastic hardening-softening model (JPHS model, which can be used for numerical modelling of the soils behaviour. Although the JPHS model is based on the elasto-plastic theory, like the Mohr-Coulomb model that is widely used in geotechnics, it contains some improvements, which removes the main disadvantages of the MC model. The presented model is coupled with an isotopically hardening and softening law, non-linear elastic stress-strain law, non-associated elasto-plastic material description and a cap yield surface. The validation of the model is done by comparing the numerical results with real measured data from the laboratory tests and by testing of the model on the real project of the tunnel excavation. The 3D numerical analysis is performed and the comparison between the JPHS, Mohr-Coulomb, Modified Cam-Clay, Hardening small strain model and monitoring in-situ data is done.
Odessa Tsunami of 27 June 2014: Observations and Numerical Modelling
Šepić, Jadranka; Rabinovich, Alexander B.; Sytov, Victor N.
2018-04-01
On 27 June, a 1-2-m high wave struck the beaches of Odessa, the third largest Ukrainian city, and the neighbouring port-town Illichevsk (northwestern Black Sea). Throughout the day, prominent seiche oscillations were observed in several other ports of the Black Sea. Tsunamigenic synoptic conditions were found over the Black Sea, stretching from Romania in the west to the Crimean Peninsula in the east. Intense air pressure disturbances and convective thunderstorm clouds were associated with these conditions; right at the time of the event, a 1.5-hPa air pressure jump was recorded at Odessa and a few hours earlier in Romania. We have utilized a barotropic ocean numerical model to test two hypotheses: (1) a tsunami-like wave was generated by an air pressure disturbance propagating directly over Odessa ("Experiment 1"); (2) a tsunami-like wave was generated by an air pressure disturbance propagating offshore, approximately 200 km to the south of Odessa, and along the shelf break ("Experiment 2"). Both experiments decisively confirm the meteorological origin of the tsunami-like waves on the coast of Odessa and imply that intensified long ocean waves in this region were generated via the Proudman resonance mechanism while propagating over the northwestern Black Sea shelf. The "Odessa tsunami" of 27 June 2014 was identified as a "beach meteotsunami", similar to events regularly observed on the beaches of Florida, USA, but different from the "harbour meteotsunamis", which occurred 1-3 days earlier in Ciutadella (Baleares, Spain), Mazara del Vallo (Sicily, Italy) and Vela Luka (Croatia) in the Mediterranean Sea, despite that they were associated with the same atmospheric system moving over the Mediterranean/Black Sea region on 23-27 June 2014.
Creating safer coastal and port infrastructure with innovative physical and numerical modelling
CSIR Research Space (South Africa)
Tulsi, K
2015-10-01
Full Text Available Infrastructure with Innovative Physical and Numerical Modelling Kishan Tulsi Physical and Numerical modelling Breakwater Monitoring Armour track Vessel manoeuvring simulations for safe port design and operations Simflex software... – Integrated Port Operations Support System Virtual Buoy Physical modelling Numerical modelling Armour Track Armour Track Armour Track Armour Track Armour track using 3D data points Ship manoeuvring simulations: Ship Manoeuvring simulations Port...
Xing, F.; Masson, R.; Lopez, S.
2017-09-01
This paper introduces a new discrete fracture model accounting for non-isothermal compositional multiphase Darcy flows and complex networks of fractures with intersecting, immersed and non-immersed fractures. The so called hybrid-dimensional model using a 2D model in the fractures coupled with a 3D model in the matrix is first derived rigorously starting from the equi-dimensional matrix fracture model. Then, it is discretized using a fully implicit time integration combined with the Vertex Approximate Gradient (VAG) finite volume scheme which is adapted to polyhedral meshes and anisotropic heterogeneous media. The fully coupled systems are assembled and solved in parallel using the Single Program Multiple Data (SPMD) paradigm with one layer of ghost cells. This strategy allows for a local assembly of the discrete systems. An efficient preconditioner is implemented to solve the linear systems at each time step and each Newton type iteration of the simulation. The numerical efficiency of our approach is assessed on different meshes, fracture networks, and physical settings in terms of parallel scalability, nonlinear convergence and linear convergence.
Rigorous Science: a How-To Guide
Directory of Open Access Journals (Sweden)
Arturo Casadevall
2016-11-01
Full Text Available Proposals to improve the reproducibility of biomedical research have emphasized scientific rigor. Although the word “rigor” is widely used, there has been little specific discussion as to what it means and how it can be achieved. We suggest that scientific rigor combines elements of mathematics, logic, philosophy, and ethics. We propose a framework for rigor that includes redundant experimental design, sound statistical analysis, recognition of error, avoidance of logical fallacies, and intellectual honesty. These elements lead to five actionable recommendations for research education.
Numerical vs. turbulent diffusion in geophysical flow modelling
International Nuclear Information System (INIS)
D'Isidoro, M.; Maurizi, A.; Tampieri, F.
2008-01-01
Numerical advection schemes induce the spreading of passive tracers from localized sources. The effects of changing resolution and Courant number are investigated using the WAF advection scheme, which leads to a sub-diffusive process. The spreading rate from an instantaneous source is compared with the physical diffusion necessary to simulate unresolved turbulent motions. The time at which the physical diffusion process overpowers the numerical spreading is estimated, and is shown to reduce as the resolution increases, and to increase as the wind velocity increases.
Numerical modeling of continental lithospheric weak zone over plume
Perepechko, Y. V.; Sorokin, K. E.
2011-12-01
The work is devoted to the development of magmatic systems in the continental lithosphere over diffluent mantle plumes. The areas of tension originating over them are accompanied by appearance of fault zones, and the formation of permeable channels, which are distributed magmatic melts. The numerical simulation of the dynamics of deformation fields in the lithosphere due to convection currents in the upper mantle, and the formation of weakened zones that extend up to the upper crust and create the necessary conditions for the formation of intermediate magma chambers has been carried out. Thermodynamically consistent non-isothermal model simulates the processes of heat and mass transfer of a wide class of magmatic systems, as well as the process of strain localization in the lithosphere and their influence on the formation of high permeability zones in the lower crust. The substance of the lithosphere is a rheologic heterophase medium, which is described by a two-velocity hydrodynamics. This makes it possible to take into account the process of penetration of the melt from the asthenosphere into the weakened zone. The energy dissipation occurs mainly due to interfacial friction and inelastic relaxation of shear stresses. The results of calculation reveal a nonlinear process of the formation of porous channels and demonstrate the diversity of emerging dissipative structures which are determined by properties of both heterogeneous lithosphere and overlying crust. Mutual effect of a permeable channel and the corresponding filtration process of the melt on the mantle convection and the dynamics of the asthenosphere have been studied. The formation of dissipative structures in heterogeneous lithosphere above mantle plumes occurs in accordance with the following scenario: initially, the elastic behavior of heterophase lithosphere leads to the formation of the narrow weakened zone, though sufficiently extensive, with higher porosity. Further, the increase in the width of
International Nuclear Information System (INIS)
Sada, Koichi; Michioka, Takenobu; Ichikawa, Yoichi
2002-01-01
Because effluent gas is sometimes released from low positions, viz., near the ground surface and around buildings, the effects caused by buildings within the site area are not negligible for gas diffusion predictions. For these reasons, the effects caused by buildings for gas diffusion are considered under the terrain following calculation coordinate system in this report. Numerical calculation meshes on the ground surface are treated as the building with the adaptation of wall function techniques of turbulent quantities in the flow calculations using a turbulence closure model. The reflection conditions of released particles on building surfaces are taken into consideration in the diffusion calculation using the Lagrangian particle model. Obtained flow and diffusion calculation results are compared with those of wind tunnel experiments around the building. It was apparent that features observed in a wind tunnel, viz., the formation of cavity regions behind the building and the gas diffusion to the ground surface behind the building, are also obtained by numerical calculation. (author)
Numerical modeling of the pulsar wind interaction with ISM
Bogovalov, S. V.; Chechetkin, V. M.; Koldoba, A. V.; Ustyugova, G. V.; Battiston, R; Shea, MA; Rakowski, C; Chatterjee, S
2006-01-01
Time dependent numerical simulation of relativistic wind interaction with interstellar medium was performed. The winds are ejected from magnetosphere of rotation powered pulsars. The particle flux in the winds is assumed to be isotropic. The energy flux is taken as strongly anisotropic in accordance
Numerical modeling of fine particle fractal aggregates in turbulent flow
Directory of Open Access Journals (Sweden)
Cao Feifeng
2015-01-01
Full Text Available A method for prediction of fine particle transport in a turbulent flow is proposed, the interaction between particles and fluid is studied numerically, and fractal agglomerate of fine particles is analyzed using Taylor-expansion moment method. The paper provides a better understanding of fine particle dynamics in the evolved flows.
Merging of coronal and heliospheric numerical two dimensional MHD models
Czech Academy of Sciences Publication Activity Database
Odstrčil, Dušan; Linker, J. A.; Lionello, R.; Mikic, Z.; Riley, P.; Pizzo, J. V.; Luhmann, J. G.
2002-01-01
Roč. 107, A12 (2002), s. SSH14-1 - SSH14-11 ISSN 0148-0227 R&D Projects: GA AV ČR IAA3003003 Institutional research plan: CEZ:AV0Z1003909 Keywords : coronal mass ejection * interplanetary shock * numerical MHD simulation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 2.245, year: 2002
Numerical Modeling of Fluid Flow in the Tape Casting Process
DEFF Research Database (Denmark)
Jabbari, Masoud; Hattel, Jesper Henri
2011-01-01
The flow behavior of the fluid in the tape casting process is analyzed. A simple geometry is assumed for running the numerical calculations in ANSYS Fluent and the main parameters are expressed in non-dimensional form. The effect of different values for substrate velocity and pressure force...
Numerical modelling of random walk one-dimensional diffusion
International Nuclear Information System (INIS)
Vamos, C.; Suciu, N.; Peculea, M.
1996-01-01
The evolution of a particle which moves on a discrete one-dimensional lattice, according to a random walk low, approximates better the diffusion process smaller the steps of the spatial lattice and time are. For a sufficiently large assembly of particles one can assume that their relative frequency at lattice knots approximates the distribution function of the diffusion process. This assumption has been tested by simulating on computer two analytical solutions of the diffusion equation: the Brownian motion and the steady state linear distribution. To evaluate quantitatively the similarity between the numerical and analytical solutions we have used a norm given by the absolute value of the difference of the two solutions. Also, a diffusion coefficient at any lattice knots and moment of time has been calculated, by using the numerical solution both from the diffusion equation and the particle flux given by Fick's low. The difference between diffusion coefficient of analytical solution and the spatial lattice mean coefficient of numerical solution constitutes another quantitative indication of the similarity of the two solutions. The results obtained show that the approximation depends first on the number of particles at each knot of the spatial lattice. In conclusion, the random walk is a microscopic process of the molecular dynamics type which permits simulations precision of the diffusion processes with given precision. The numerical method presented in this work may be useful both in the analysis of real experiments and for theoretical studies
Numerical experiment with modelled return echo of a satellite
Indian Academy of Sciences (India)
Abstract. We have simulated the return echo of a satellite altimeter from a rough ocean surface using an analytical formula and have studied its sensitivity with respect to various oceanic and altimeter parameters. Our numerical expcriment shows that for normally observed significant wave heights (SWFI) the effect of ...
Optimized numerical annular flow dryout model using the drift-flux model in tube geometry
International Nuclear Information System (INIS)
Chun, Ji Han; Lee, Un Chul
2008-01-01
Many experimental analyses for annular film dryouts, which is one of the Critical Heat Flux (CHF) mechanisms, have been performed because of their importance. Numerical approaches must also be developed in order to assess the results from experiments and to perform pre-tests before experiments. Various thermal-hydraulic codes, such as RELAP, COBRATF, MARS, etc., have been used in the assessment of the results of dryout experiments and in experimental pre-tests. These thermal-hydraulic codes are general tools intended for the analysis of various phenomena that could appear in nuclear power plants, and many models applying these codes are unnecessarily complex for the focused analysis of dryout phenomena alone. In this study, a numerical model was developed for annular film dryout using the drift-flux model from uniform heated tube geometry. Several candidates of models that strongly affect dryout, such as the entrainment model, deposition model, and the criterion for the dryout point model, were tested as candidates for inclusion in an optimized annular film dryout model. The optimized model was developed by adopting the best combination of these candidate models, as determined through comparison with experimental data. This optimized model showed reasonable results, which were better than those of MARS code
Numerical investigation of the recruitment process in open marine population models
International Nuclear Information System (INIS)
Angulo, O; López-Marcos, J C; López-Marcos, M A; Martínez-Rodríguez, J
2011-01-01
The changes in the dynamics, produced by the recruitment process in an open marine population model, are investigated from a numerical point of view. The numerical method considered, based on the representation of the solution along the characteristic lines, approximates properly the steady states of the model, and is used to analyze the asymptotic behavior of the solutions of the model
Free surface modelling with two-fluid model and reduced numerical diffusion of the interface
International Nuclear Information System (INIS)
Strubelj, Luka; Tiselj, Izrok
2008-01-01
Full text of publication follows: The free surface flows are successfully modelled with one of existing free surface models, such as: level set method, volume of fluid method (with/without surface reconstruction), front tracking, two-fluid model (two momentum equations) with modified interphase force and others. The main disadvantage of two-fluid model used for simulations of free surface flows is numerical diffusion of the interface, which can be significantly reduced using the method presented in this paper. Several techniques for reduction of numerical diffusion of the interface have been implemented in the volume of fluid model and are based on modified numerical schemes for advection of volume fraction near the interface. The same approach could be used also for two-fluid method, but according to our experience more successful reduction of numerical diffusion of the interface can be achieved with conservative level set method. Within the conservative level set method, continuity equation for volume fraction is solved and after that the numerical diffusion of the interface is reduced in such a way that the thickness of the interface is kept constant during the simulation. Reduction of the interface diffusion can be also called interface sharpening. In present paper the two-fluid model with interface sharpening is validated on Rayleigh-Taylor instability. Under assumptions of isothermal and incompressible flow of two immiscible fluids, we simulated a system with the fluid of higher density located above the fluid of smaller density in two dimensions. Due to gravity in the system, fluid with higher density moves below the fluid with smaller density. Initial condition is not a flat interface between the fluids, but a sine wave with small amplitude, which develops into a mushroom-like structure. Mushroom-like structure in simulation of Rayleigh-Taylor instability later develops to small droplets as result of numerical dispersion of interface (interface sharpening
Numerical simulations and mathematical models of flows in complex geometries
DEFF Research Database (Denmark)
Hernandez Garcia, Anier
The research work of the present thesis was mainly aimed at exploiting one of the strengths of the Lattice Boltzmann methods, namely, the ability to handle complicated geometries to accurately simulate flows in complex geometries. In this thesis, we perform a very detailed theoretical analysis...... and through the Chapman-Enskog multi-scale expansion technique the dependence of the kinetic viscosity on each scheme is investigated. Seeking for optimal numerical schemes to eciently simulate a wide range of complex flows a variant of the finite element, off-lattice Boltzmann method [5], which uses...... the characteristic based integration is also implemented. Using the latter scheme, numerical simulations are conducted in flows of different complexities: flow in a (real) porous network and turbulent flows in ducts with wall irregularities. From the simulations of flows in porous media driven by pressure gradients...
Numerical modelling of passively Q-switched intracavity Raman lasers
International Nuclear Information System (INIS)
Ding Shuanghong; Zhang Xingyu; Wang Qingpu; Zhang Jun; Wang Shumei; Liu Yuru; Zhang Xuehui
2007-01-01
Assuming intracavity photon densities to be of Gaussian spatial distributions, the space-dependent rate equations of passively Q-switched intracavity Raman lasers are deduced for the first time for the pumping beams of Gaussian and top-head spatial distributions, respectively. The new rate equations are normalized and solved numerically to investigate the influences of the normalized initial population inversion density, normalized Raman gain coefficient, saturable absorber parameter, beam size ratio of pump to fundamental laser and loss ratio of the first Stokes to fundamental laser on the pulse parameters of the first Stokes. The results of the Gaussian and top-head pumpings show similar trends despite some discrepancies. The new theories and numerical results will help design passively Q-switched intracavity Raman lasers of high performance
Fractional Calculus in Hydrologic Modeling: A Numerical Perspective
Energy Technology Data Exchange (ETDEWEB)
David A. Benson; Mark M. Meerschaert; Jordan Revielle
2012-01-01
Fractional derivatives can be viewed either as a handy extension of classical calculus or, more deeply, as mathematical operators defined by natural phenomena. This follows the view that the diffusion equation is defined as the governing equation of a Brownian motion. In this paper, we emphasize that fractional derivatives come from the governing equations of stable Levy motion, and that fractional integration is the corresponding inverse operator. Fractional integration, and its multi-dimensional extensions derived in this way, are intimately tied to fractional Brownian (and Levy) motions and noises. By following these general principles, we discuss the Eulerian and Lagrangian numerical solutions to fractional partial differential equations, and Eulerian methods for stochastic integrals. These numerical approximations illuminate the essential nature of the fractional calculus.
Heterogeneous agent model and numerical analysis of learning
Czech Academy of Sciences Publication Activity Database
Vošvrda, Miloslav; Vácha, Lukáš
2002-01-01
Roč. 9, č. 17 (2002), s. 15-22 ISSN 1212-074X R&D Projects: GA ČR GA402/01/0034; GA ČR GA402/01/0539; GA AV ČR IAA7075202 Institutional research plan: CEZ:AV0Z1075907 Keywords : efficient markets hypothesis * technical trading rules * numerical analysis of learning Subject RIV: AH - Economics
International Nuclear Information System (INIS)
Okazaki, Motoaki
1997-11-01
In the previous report, the usefulness of a new numerical method to achieve a rigorous numerical calculation using a simple explicit method with the volume-junction model was presented with the verification calculation for the depressurization of a saturated two-phase mixture. In this report, on the basis of solution method above, a numerical method for general condition of two-phase flow in non-equilibrium states is presented. In general condition of two-phase flow, the combinations of saturated and non-saturated conditions of each phase are considered in the each flow of volume and junction. Numerical evaluation programs are separately prepared for each combination of flow condition. Several numerical calculations of various kinds of non-equilibrium two-phase flow are made to examine the validity of the numerical method. Calculated results showed that the thermodynamic states obtained in different solution schemes were consistent with each other. In the first scheme, the states are determined by using the steam table as a function of pressure and specific enthalpy which are obtained as the solutions of simultaneous equations. In the second scheme, density and specific enthalpy of each phase are directly calculated by using conservation equations of mass and enthalpy of each phase, respectively. Further, no accumulation of error in mass and energy was found. As for the specific enthalpy, two cases of using energy equations for the volume are examined. The first case uses total energy conservation equation and the second case uses the type of the first law of thermodynamics. The results of both cases agreed well. (author)
Physiological studies of muscle rigor mortis in the fowl
International Nuclear Information System (INIS)
Nakahira, S.; Kaneko, K.; Tanaka, K.
1990-01-01
A simple system was developed for continuous measurement of muscle contraction during nor mortis. Longitudinal muscle strips dissected from the Peroneus Longus were suspended in a plastic tube containing liquid paraffin. Mechanical activity was transmitted to a strain-gauge transducer which is connected to a potentiometric pen-recorder. At the onset of measurement 1.2g was loaded on the muscle strip. This model was used to study the muscle response to various treatments during nor mortis. All measurements were carried out under the anaerobic condition at 17°C, except otherwise stated. 1. The present system was found to be quite useful for continuous measurement of muscle rigor course. 2. Muscle contraction under the anaerobic condition at 17°C reached a peak about 2 hours after the onset of measurement and thereafter it relaxed at a slow rate. In contrast, the aerobic condition under a high humidity resulted in a strong rigor, about three times stronger than that in the anaerobic condition. 3. Ultrasonic treatment (37, 000-47, 000Hz) at 25°C for 10 minutes resulted in a moderate muscle rigor. 4. Treatment of muscle strip with 2mM EGTA at 30°C for 30 minutes led to a relaxation of the muscle. 5. The muscle from the birds killed during anesthesia with pentobarbital sodium resulted in a slow rate of rigor, whereas the birds killed one day after hypophysectomy led to a quick muscle rigor as seen in intact controls. 6. A slight muscle rigor was observed when muscle strip was placed in a refrigerator at 0°C for 18.5 hours and thereafter temperature was kept at 17°C. (author)
Numerical modeling and optimization of the Iguassu gas centrifuge
Bogovalov, S. V.; Borman, V. D.; Borisevich, V. D.; Tronin, V. N.; Tronin, I. V.
2017-07-01
The full procedure of the numerical calculation of the optimized parameters of the Iguassu gas centrifuge (GC) is under discussion. The procedure consists of a few steps. On the first step the problem of a hydrodynamical flow of the gas in the rotating rotor of the GC is solved numerically. On the second step the problem of diffusion of the binary mixture of isotopes is solved. The separation power of the gas centrifuge is calculated after that. On the last step the time consuming procedure of optimization of the GC is performed providing us the maximum of the separation power. The optimization is based on the BOBYQA method exploring the results of numerical simulations of the hydrodynamics and diffusion of the mixture of isotopes. Fast convergence of calculations is achieved due to exploring of a direct solver at the solution of the hydrodynamical and diffusion parts of the problem. Optimized separative power and optimal internal parameters of the Iguassu GC with 1 m rotor were calculated using the developed approach. Optimization procedure converges in 45 iterations taking 811 minutes.
An extension of clarke's model with stochastic amplitude flip processes
Hoel, Hakon; Nyberg, Henrik
2014-01-01
. By rigorous analysis and numerical studies, we show that in many settings, signal realizations are generated more efficiently by Gaussian process algorithms than by the MFC model's algorithm. Numerical examples that strengthen these observations are also
Numerical implementation of a transverse-isotropic inelastic, work-hardening constitutive model
International Nuclear Information System (INIS)
Baladi, G.Y.
1978-01-01
The numerical implementation of a transverse-isotropic inelastic, work-hardening plastic constitutive model is documented. A brief review of the model is presented first to facilitate the understanding of its numerical implementation. This model is formulated in terms of 'pseudo' stress invariants, so that the incremental stress-strain relationship can be readily incorporated into existing finite-difference or infinite-element computer codes. The anisotropic model reduces to its isotropic counterpart without any changes in the mathematical formulation or in the numerical implementation (algorithm) of the model. A typical example of the model and its behavior in uniaxial strain and triaxial compression is presented. (Auth.)
Rigorous simulation: a tool to enhance decision making
Energy Technology Data Exchange (ETDEWEB)
Neiva, Raquel; Larson, Mel; Baks, Arjan [KBC Advanced Technologies plc, Surrey (United Kingdom)
2012-07-01
The world refining industries continue to be challenged by population growth (increased demand), regional market changes and the pressure of regulatory requirements to operate a 'green' refinery. Environmental regulations are reducing the value and use of heavy fuel oils, and leading to convert more of the heavier products or even heavier crude into lighter products while meeting increasingly stringent transportation fuel specifications. As a result actions are required for establishing a sustainable advantage for future success. Rigorous simulation provides a key advantage improving the time and efficient use of capital investment and maximizing profitability. Sustainably maximizing profit through rigorous modeling is achieved through enhanced performance monitoring and improved Linear Programme (LP) model accuracy. This paper contains examples on these two items. The combination of both increases overall rates of return. As refiners consider optimizing existing assets and expanding projects, the process agreed to achieve these goals is key for a successful profit improvement. The benefit of rigorous kinetic simulation with detailed fractionation allows for optimizing existing asset utilization while focusing the capital investment in the new unit(s), and therefore optimizing the overall strategic plan and return on investment. Individual process unit's monitoring works as a mechanism for validating and optimizing the plant performance. Unit monitoring is important to rectify poor performance and increase profitability. The key to a good LP relies upon the accuracy of the data used to generate the LP sub-model data. The value of rigorous unit monitoring are that the results are heat and mass balanced consistently, and are unique for a refiners unit / refinery. With the improved match of the refinery operation, the rigorous simulation models will allow capturing more accurately the non linearity of those process units and therefore provide correct
Krompecher, T
1981-01-01
Objective measurements were carried out to study the evolution of rigor mortis on rats at various temperatures. Our experiments showed that: (1) at 6 degrees C rigor mortis reaches full development between 48 and 60 hours post mortem, and is resolved at 168 hours post mortem; (2) at 24 degrees C rigor mortis reaches full development at 5 hours post mortem, and is resolved at 16 hours post mortem; (3) at 37 degrees C rigor mortis reaches full development at 3 hours post mortem, and is resolved at 6 hours post mortem; (4) the intensity of rigor mortis grows with increase in temperature (difference between values obtained at 24 degrees C and 37 degrees C); and (5) and 6 degrees C a "cold rigidity" was found, in addition to and independent of rigor mortis.
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....
International Nuclear Information System (INIS)
Greenly, G.D.; Dickerson, M.H.
1983-03-01
Numerical models on several levels of complexity should be available to the emergency response planner. They are a basic tool but must be used in conjunction with both measurements and experience. When these tools are used in a complimentary fashion they greatly enhance the capability of the consequence manager to respond in an emergency situation. Because each accident or incident develops it's own characteristics and requirements the system must be capable of a flexible response. Interaction and feedback between model results from a suite of models and measurements (including airborne measurements) serve the emergency response planner's spectrum of needs, ranging from planning exercises and emergency precalculations to a real-time emergency response
Numerical Modeling and Mechanical Analysis of Flexible Risers
Li, J. Y.; Qiu, Z. X.; Ju, J. S.
2015-01-01
ABAQUS is used to create a detailed finite element model for a 10-layer unbonded flexible riser to simulate the riser’s mechanical behavior under three load conditions: tension force and internal and external pressure. It presents a technique to create detailed finite element model and to analyze flexible risers. In FEM model, all layers are modeled separately with contact interfaces; interaction between steel trips in certain layers has been considered as well. FEM model considering contact ...
Numerical modelling of the atmospheric mixing-layer diurnal evolution
International Nuclear Information System (INIS)
Molnary, L. de.
1990-03-01
This paper introduce a numeric procedure to determine the temporal evolution of the height, potential temperature and mixing ratio in the atmospheric mixing layer. The time and spatial derivatives were evaluated via forward in time scheme to predict the local evolution of the mixing-layer parameters, and a forward in time, upstream in space scheme to predict the evolution of the mixing-layer over a flat region with a one-dimensional advection component. The surface turbulent fluxes of sensible and latent heat were expressed using a simple sine wave that is function of the hour day and kind of the surface (water or country). (author) [pt
Numerical modelling: where will we be in ten years
International Nuclear Information System (INIS)
Caseau, P.
1993-01-01
Computer hardware power is increasing following a regular curve since 30 years; the 2000-2005 horizon is easy to extrapolate. But interactions between machine capacity, processing speed, working memory and memory store, pre- and post-processing/stations capacity, process communications/stations capacity, etc. are more difficult to assess, such as the place of one-Teraflop machines in an architecture. The needs for an one Teraflop capacity for various applications are discussed: numerical simulation of diffusion and transport in neutronics, of poly-phasic and reactive flows, of large electric utility networks, of physico-chemistry at molecular levels; artificial intelligence may play a major role. 2 figs
Numerical modelling of tissue-equivalent proportional counters
International Nuclear Information System (INIS)
Segur, P.; Colautti, P.
1995-01-01
In this paper a survey is given of the various numerical techniques employed to study the transport of ionising particles inside a TEPC. The first part is devoted to the description of the general concept of particle transport calculations. Thereafter, the different methods available to study transport phenomena and energy deposition in the sensitive volume and in counter walls are described. Finally, the basic ionisation mechanisms which may occur in a counter are described, and the non-equilibrium phenomena which play an important role mainly for counters that are to be used in measurements at the nanodosemeter level are studied. (author)
Prediction of hydroxyl concentrations in cement pore water using a numerical cement hydration model
Eijk, van R.J.; Brouwers, H.J.H.
2000-01-01
In this paper, a 3D numerical cement hydration model is used for predicting alkali and hydroxyl concentrations in cement pore water. First, this numerical model is calibrated for Dutch cement employing both chemical shrinkage and calorimetric experiments. Secondly, the strength development of some
Climate change and high-resolution whole-building numerical modelling
Blocken, B.J.E.; Briggen, P.M.; Schellen, H.L.; Hensen, J.L.M.
2010-01-01
This paper briefly discusses the need of high-resolution whole-building numerical modelling in the context of climate change. High-resolution whole-building numerical modelling can be used for detailed analysis of the potential consequences of climate change on buildings and to evaluate remedial
A review of recent advances in numerical modelling of local scour problems
DEFF Research Database (Denmark)
Sumer, B. Mutlu
2014-01-01
A review is presented of recent advances in numerical modelling of local scour problems. The review is organized in five sections: Highlights of numerical modelling of local scour; Influence of turbulence on scour; Backfilling of scour holes; Scour around complex structures; and Scour protection ...
How to Overcome Numerical Challenges to Modeling Stirling Engines
Dyson, Rodger W.; Wilson, Scott D.; Tew, Roy C.
2004-01-01
Nuclear thermal to electric power conversion carries the promise of longer duration missions and higher scientific data transmission rates back to Earth for a range of missions, including both Mars rovers and deep space missions. A free-piston Stirling convertor is a candidate technology that is considered an efficient and reliable power conversion device for such purposes. While already very efficient, it is believed that better Stirling engines can be developed if the losses inherent in current designs could be better understood. However, they are difficult to instrument and so efforts are underway to simulate a complete Stirling engine numerically. This has only recently been attempted and a review of the methods leading up to and including such computational analysis is presented. And finally it is proposed that the quality and depth of Stirling loss understanding may be improved by utilizing the higher fidelity and efficiency of recently developed numerical methods. One such method, the Ultra HI-FI technique is presented in detail.
Scott, L Ridgway
2011-01-01
Computational science is fundamentally changing how technological questions are addressed. The design of aircraft, automobiles, and even racing sailboats is now done by computational simulation. The mathematical foundation of this new approach is numerical analysis, which studies algorithms for computing expressions defined with real numbers. Emphasizing the theory behind the computation, this book provides a rigorous and self-contained introduction to numerical analysis and presents the advanced mathematics that underpin industrial software, including complete details that are missing from most textbooks. Using an inquiry-based learning approach, Numerical Analysis is written in a narrative style, provides historical background, and includes many of the proofs and technical details in exercises. Students will be able to go beyond an elementary understanding of numerical simulation and develop deep insights into the foundations of the subject. They will no longer have to accept the mathematical gaps that ex...
Numerical Modeling of Diesel Spray Formation and Combustion
Bekdemir, C.; Somers, L.M.T.; Goey, de L.P.H.
2009-01-01
A study is presented on the modeling of fuel sprays in diesel engines. The objective of this study is in the first place to accurately and efficiently model non-reacting diesel spray formation, and secondly to include ignition and combustion. For that an efficient 1D Euler-Euler spray model [21] is
"Rigor mortis" in a live patient.
Chakravarthy, Murali
2010-03-01
Rigor mortis is conventionally a postmortem change. Its occurrence suggests that death has occurred at least a few hours ago. The authors report a case of "Rigor Mortis" in a live patient after cardiac surgery. The likely factors that may have predisposed such premortem muscle stiffening in the reported patient are, intense low cardiac output status, use of unusually high dose of inotropic and vasopressor agents and likely sepsis. Such an event may be of importance while determining the time of death in individuals such as described in the report. It may also suggest requirement of careful examination of patients with muscle stiffening prior to declaration of death. This report is being published to point out the likely controversies that might arise out of muscle stiffening, which should not always be termed rigor mortis and/ or postmortem.
[Rigor mortis -- a definite sign of death?].
Heller, A R; Müller, M P; Frank, M D; Dressler, J
2005-04-01
In the past years an ongoing controversial debate exists in Germany, regarding quality of the coroner's inquest and declaration of death by physicians. We report the case of a 90-year old female, who was found after an unknown time following a suicide attempt with benzodiazepine. The examination of the patient showed livores (mortis?) on the left forearm and left lower leg. Moreover, rigor (mortis?) of the left arm was apparent which prevented arm flexion and extension. The hypothermic patient with insufficient respiration was intubated and mechanically ventilated. Chest compressions were not performed, because central pulses were (hardly) palpable and a sinus bradycardia 45/min (AV-block 2 degrees and sole premature ventricular complexes) was present. After placement of an intravenous line (17 G, external jugular vein) the hemodynamic situation was stabilized with intermittent boli of epinephrine and with sodium bicarbonate. With improved circulation livores and rigor disappeared. In the present case a minimal central circulation was noted, which could be stabilized, despite the presence of certain signs of death ( livores and rigor mortis). Considering the finding of an abrogated peripheral perfusion (livores), we postulate a centripetal collapse of glycogen and ATP supply in the patients left arm (rigor), which was restored after resuscitation and reperfusion. Thus, it appears that livores and rigor are not sensitive enough to exclude a vita minima, in particular in hypothermic patients with intoxications. Consequently a careful ABC-check should be performed even in the presence of apparently certain signs of death, to avoid underdiagnosing a vita minima. Additional ECG- monitoring is required to reduce the rate of false positive declarations of death. To what extent basic life support by paramedics should commence when rigor and livores are present until physician DNR order, deserves further discussion.
Continuum-Kinetic Models and Numerical Methods for Multiphase Applications
Nault, Isaac Michael
This thesis presents a continuum-kinetic approach for modeling general problems in multiphase solid mechanics. In this context, a continuum model refers to any model, typically on the macro-scale, in which continuous state variables are used to capture the most important physics: conservation of mass, momentum, and energy. A kinetic model refers to any model, typically on the meso-scale, which captures the statistical motion and evolution of microscopic entitites. Multiphase phenomena usually involve non-negligible micro or meso-scopic effects at the interfaces between phases. The approach developed in the thesis attempts to combine the computational performance benefits of a continuum model with the physical accuracy of a kinetic model when applied to a multiphase problem. The approach is applied to modeling a single particle impact in Cold Spray, an engineering process that intimately involves the interaction of crystal grains with high-magnitude elastic waves. Such a situation could be classified a multiphase application due to the discrete nature of grains on the spatial scale of the problem. For this application, a hyper elasto-plastic model is solved by a finite volume method with approximate Riemann solver. The results of this model are compared for two types of plastic closure: a phenomenological macro-scale constitutive law, and a physics-based meso-scale Crystal Plasticity model.
Numerical Analysis of Modeling Based on Improved Elman Neural Network
Directory of Open Access Journals (Sweden)
Shao Jie
2014-01-01
Full Text Available A modeling based on the improved Elman neural network (IENN is proposed to analyze the nonlinear circuits with the memory effect. The hidden layer neurons are activated by a group of Chebyshev orthogonal basis functions instead of sigmoid functions in this model. The error curves of the sum of squared error (SSE varying with the number of hidden neurons and the iteration step are studied to determine the number of the hidden layer neurons. Simulation results of the half-bridge class-D power amplifier (CDPA with two-tone signal and broadband signals as input have shown that the proposed behavioral modeling can reconstruct the system of CDPAs accurately and depict the memory effect of CDPAs well. Compared with Volterra-Laguerre (VL model, Chebyshev neural network (CNN model, and basic Elman neural network (BENN model, the proposed model has better performance.
An Integrated Numerical Model of the Spray Forming Process
DEFF Research Database (Denmark)
Pryds, Nini; Hattel, Jesper; Pedersen, Trine Bjerre
2002-01-01
of the deposition model is accomplished using a 2D cylindrical heat flow model. This model is now coupled with an atomization model via a log-normal droplet size distribution. The coupling between the atomization and the deposition is accomplished by ensuring that the total droplet size distribution of the spray......In this paper, an integrated approach for modelling the entire spray forming process is presented. The basis for the analysis is a recently developed model which extents previous studies and includes the interaction between an array of droplets and the enveloping gas. The formulation...... is in fact the summation of 'local' droplet size distributions along the r-axis. A key parameter, which determines the yield and the shape of the deposit material, is the sticking efficiency. The sticking phenomenon is therefore incorporated into the deposition model. (C) 2002 Acta Materialia Inc. Published...
Theoretical and Numerical Modeling of Acoustic Metamaterials for Aeroacoustic Applications
Directory of Open Access Journals (Sweden)
Umberto Iemma
2016-05-01
Full Text Available The advent, during the first decade of the 21st century, of the concept of acoustic metamaterial has disclosed an incredible potential of development for breakthrough technologies. Unfortunately, the extension of the same concepts to aeroacoustics has turned out to be not a trivial task, because of the different structure of the governing equations, characterized by the presence of the background aerodynamic convection. Some of the approaches recently introduced to circumvent the problem are biased by a fundamental assumption that makes the actual realization of devices extremely unlikely: the metamaterial should guarantee an adapted background aerodynamic convection in order to modify suitably the acoustic field and obtain the desired effect, thus implying the porosity of the cloaking device. In the present paper, we propose an interpretation of the metamaterial design that removes this unlikely assumption, focusing on the identification of an aerodynamically-impermeable metamaterial capable of reproducing the surface impedance profile required to achieve the desired scattering abatement. The attention is focused on a moving obstacle impinged by an acoustic perturbation induced by a co-moving source. The problem is written in a frame of reference rigidly connected to the moving object to couple the convective wave equation in the hosting medium with the inertially-anisotropic wave operator within the cloak. The problem is recast in an integral form and numerically solved through a boundary-field element method. The matching of the local wave vector is used to derive a convective design of the metamaterial applicable to the specific problem analyzed. Preliminary numerical results obtained under the simplifying assumption of a uniform aerodynamic flow reveal a considerable enhancement of the masking capability of the convected design. The numerical method developed shows a remarkable computational efficiency, completing a simulation of the entire
An ultramicroscopic study on rigor mortis.
Suzuki, T
1976-01-01
Gastrocnemius muscles taken from decapitated mice at various intervals after death and from mice killed by 2,4-dinitrophenol or mono-iodoacetic acid injection to induce rigor mortis soon after death, were observed by electron microscopy. The prominent appearance of many fine cross striations in the myofibrils (occurring about every 400 A) was considered to be characteristic of rigor mortis. These striations were caused by minute granules studded along the surfaces of both thick and thin filaments and appeared to be the bridges connecting the 2 kinds of filaments and accounted for the hardness and rigidity of the muscle.
Directory of Open Access Journals (Sweden)
John (Jack P. Riegel III
2016-04-01
Full Text Available Historically, there has been little correlation between the material properties used in (1 empirical formulae, (2 analytical formulations, and (3 numerical models. The various regressions and models may each provide excellent agreement for the depth of penetration into semi-infinite targets. But the input parameters for the empirically based procedures may have little in common with either the analytical model or the numerical model. This paper builds on previous work by Riegel and Anderson (2014 to show how the Effective Flow Stress (EFS strength model, based on empirical data, can be used as the average flow stress in the analytical Walker–Anderson Penetration model (WAPEN (Anderson and Walker, 1991 and how the same value may be utilized as an effective von Mises yield strength in numerical hydrocode simulations to predict the depth of penetration for eroding projectiles at impact velocities in the mechanical response regime of the materials. The method has the benefit of allowing the three techniques (empirical, analytical, and numerical to work in tandem. The empirical method can be used for many shot line calculations, but more advanced analytical or numerical models can be employed when necessary to address specific geometries such as edge effects or layering that are not treated by the simpler methods. Developing complete constitutive relationships for a material can be costly. If the only concern is depth of penetration, such a level of detail may not be required. The effective flow stress can be determined from a small set of depth of penetration experiments in many cases, especially for long penetrators such as the L/D = 10 ones considered here, making it a very practical approach. In the process of performing this effort, the authors considered numerical simulations by other researchers based on the same set of experimental data that the authors used for their empirical and analytical assessment. The goals were to establish a
Numerical modelling of the Concorde wake during ZEBRE
Energy Technology Data Exchange (ETDEWEB)
Gierens, K. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere
1997-12-31
Numerical simulations of the Concorde contrail during the ZEBRE experiment have been performed. The main goal of the simulations is to reproduce the fast vanishing of the contrail which disappeared 20-30 s after exhaust. It is difficult to evaporate ice crystals during the jet and vortex phase of the aircraft wake, when the exhaust products are trapped in the vortex cores. The trapping also excludes spatial dispersion of the ice crystals as an explanation of the short contrail lifetime. The disappearance of the contrail within 20-30 s requires that a substantial part of the exhaust gases escapes from the region that is later on trapped in the vortex cores. (author) 10 refs.
Numerical modelling of the Concorde wake during ZEBRE
Energy Technology Data Exchange (ETDEWEB)
Gierens, K [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Oberpfaffenhofen (Germany). Inst. fuer Physik der Atmosphaere
1998-12-31
Numerical simulations of the Concorde contrail during the ZEBRE experiment have been performed. The main goal of the simulations is to reproduce the fast vanishing of the contrail which disappeared 20-30 s after exhaust. It is difficult to evaporate ice crystals during the jet and vortex phase of the aircraft wake, when the exhaust products are trapped in the vortex cores. The trapping also excludes spatial dispersion of the ice crystals as an explanation of the short contrail lifetime. The disappearance of the contrail within 20-30 s requires that a substantial part of the exhaust gases escapes from the region that is later on trapped in the vortex cores. (author) 10 refs.
Modelling of functionally graded materials by numerical homogenization
Energy Technology Data Exchange (ETDEWEB)
Schmauder, S.; Weber, U. [Stuttgart Univ. (Germany). Staatliche Materialpruefungsanstalt
2001-03-01
In this contribution, the mechanical behaviour of different ZrO{sub 2}/NiCr 80 20 compositions is analysed and compared with experimental findings. The microwave-sintered material is found to possess a slightly dominant ceramic matrix for intermediate volume fractions. Its thermal expansion coefficient deviates from the rule of mixture. The modulus and the stress strain behaviour can be simulated by a numerical homogenization procedure, and the influence of residual stresses is found to be negligible. A newly introduced parameter (matricity) describes the mutual circumvention of the phases and is found to strongly control the stress level of the composite, globally as well as locally. Finally, a graded component and a metal/ceramic bi-material are compared for thermal as well as mechanical loading. (orig.)
Numerical Three-Dimensional Model of Airport Terminal Drainage System
Directory of Open Access Journals (Sweden)
Strzelecki Michał
2014-03-01
Full Text Available During the construction of an airport terminal it was found that as a result of the hydrostatic pressure of underground water the foundation plate of the building had dangerously shifted in the direction opposite to that of the gravitational forces. The only effective measure was to introduce a drainage system on the site. The complex geology of the area indicated that two independent drainage systems, i.e., a horizontal system in the Quaternary beds and a vertical system in the Tertiary water-bearing levels, were necessary. This paper presents numerical FEM calculations of the two drainage systems being part of the airport terminal drainaged esign. The computer simulation which was carried out took into consideration the actual effect of the drainage systems and their impact on the depression cone being formed in the two aquifers.
Holistic simulation of geotechnical installation processes numerical and physical modelling
2015-01-01
The book provides suitable methods for the simulations of boundary value problems of geotechnical installation processes with reliable prediction for the deformation behavior of structures in static or dynamic interaction with the soil. It summarizes the basic research of a research group from scientists dealing with constitutive relations of soils and their implementations as well as contact element formulations in FE-codes. Numerical and physical experiments are presented providing benchmarks for future developments in this field. Boundary value problems have been formulated and solved with the developed tools in order to show the effectivity of the methods. Parametric studies of geotechnical installation processes in order to identify the governing parameters for the optimization of the process are given in such a way that the findings can be recommended to practice for further use. For many design engineers in practice the assessment of the serviceability of nearby structures due to geotechnical installat...
Numerical modeling of pyrolysis of sawdust in a packed bed
Energy Technology Data Exchange (ETDEWEB)
Meng, Qingmin; Chen, Xiaoping [Southeast Univ., Nanjing (China). School of Energy and Environment
2013-07-01
An unsteady, one-dimensional mathematical model has been developed to describe the pyrolysis of sawdust in a packed bed. The sawdust bed was pyrolyzed using the hot gas and an electric heater outside the bed as the source of energy. The developed model includes mass, momentum and energy conservations of gas and solid within the bed. The gas flow in the bed is modeled using Darcy's law for fluid through a porous medium. The heat transfer model includes heat conduction inside the bed and convection between the bed and the hot gas. The kinetic model consists of primary pyrolysis reaction. A finite volume fully implicit scheme is employed for solving the heat and mass transfer model equations. A Runge-Kutta fourth order method is used for the chemical kinetics model equations. The model predictions of mass loss history and temperature were validated with published experimental results, showing a good agreement. The effects of inlet temperature on the pyrolysis process have been analyzed with model simulation. A sensitivity analysis using the model suggests that the predictions could be improved by considering the second reaction which could generate volatile flowing in the void.
Waves and particles in the Fermi accelerator model. Numerical simulation
International Nuclear Information System (INIS)
Meplan, O.
1996-01-01
This thesis is devoted to a numerical study of the quantum dynamics of the Fermi accelerator which is classically chaotic: it is particle in a one dimensional box with a oscillating wall. First, we study the classical dynamics: we show that the time of impact of the particle with the moving wall and its energy in the wall frame are conjugated variables and that Poincare surface of sections in these variables are more understandable than the usual stroboscopic sections. Then, the quantum dynamics of this systems is studied by the means of two numerical methods. The first one is a generalization of the KKR method in the space-time; it is enough to solve an integral equation on the boundary of a space-time billiard. The second method is faster and is based on successive free propagations and kicks of potential. This allows us to obtain Floquet states which we can on one hand, compare to the classical dynamics with the help of Husimi distributions and on the other hand, study as a function of parameters of the system. This study leads us to nice illustrations of phenomenons such as spatial localizations of a wave packet in a vibrating well or tunnel effects. In the adiabatic situation, we give a formula for quasi-energies which exhibits a phase term independent of states. In this regime, there exist some particular situations where the quasi-energy spectrum presents a total quasi-degeneracy. Then, the wave packet energy can increase significantly. This phenomenon is quite surprising for smooth motion of the wall. The third part deals with the evolution of a classical wave in the Fermi accelerator. Using generalized KKR method, we show a surprising phenomenon: in most of situations (so long as the wall motion is periodic), a wave is localized exponentially in the well and its energy increases in a geometric way. (author). 107 refs., 66 figs., 5 tabs. 2 appends
Numerical simulation of interior flow field of nuclear model pump
International Nuclear Information System (INIS)
Wang Chunlin; Peng Na; Kang Can; Zhao Baitong; Zhang Hao
2009-01-01
Reynolds time-averaged N-S equations and the standard k-ε turbulent model were adopted, and three-dimensional non-structural of tetrahedral mesh division was used for modeling. Multiple reference frame model of rotating fluid mechanical model was used, under the design condition, the three-dimensional incompressible turbulent flow of nuclear model pump was simulated, and the results preferably post the characteristics of the interior flow field. This paper first analyzes the total pressure and velocity distribution in the flow field, and then describes the interior flow field characteristics of each part such as the impeller, diffuser and spherical shell, and also discusses the reasons that cause these characteristics. The study results can be used to estimate the performance of nuclear model pump, and will provide some useful references for its hydraulic optimized design. (authors)
Numerical modeling of the deflagration-to-detonation transition
International Nuclear Information System (INIS)
Forest, C.A.
1978-01-01
The effect of a confined porous bed of burning explosive in contact with a solid explosive is studied by computer simulation. The burning is modeled using a bulk burn model that is a function of the surface area and the pressure. Once pressure excursions occur from the confined burning the transition to detonation is modeled using a pressure-dependent heterogeneous explosive shock decomposition model called Forest Fire. The occurrence of detonation in the solid explosive is shown to be dependent upon the surface-to-volume ratio, the confinement of the porous bed, and the geometry of the system
Ultrasonic-assisted manufacturing processes: Variational model and numerical simulations
Siddiq, Amir
2012-04-01
We present a computational study of ultrasonic assisted manufacturing processes including sheet metal forming, upsetting, and wire drawing. A fully variational porous plasticity model is modified to include ultrasonic softening effects and then utilized to account for instantaneous softening when ultrasonic energy is applied during deformation. Material model parameters are identified via inverse modeling, i.e. by using experimental data. The versatility and predictive ability of the model are demonstrated and the effect of ultrasonic intensity on the manufacturing process at hand is investigated and compared qualitatively with experimental results reported in the literature. © 2011 Elsevier B.V. All rights reserved.
Numerical Investigation of Turbulence Models for a Superlaminar Journal Bearing
Directory of Open Access Journals (Sweden)
Aoshuang Ding
2018-01-01
Full Text Available With rotating machineries working at high speeds, oil flow in bearings becomes superlaminar. Under superlaminar conditions, flow exhibits between laminar and fully developed turbulence. In this study, superlaminar oil flow in an oil-lubricated tilting-pad journal bearing is analyzed through computational fluid dynamics (CFD. A three-dimensional bearing model is established. CFD results from the laminar model and 14 turbulence models are compared with experimental findings. The laminar simulation results of pad-side pressure are inconsistent with the experimental data. Thus, the turbulence effects on superlaminar flow should be considered. The simulated temperature and pressure distributions from the classical fully developed turbulence models cannot correctly fit the experimental data. As such, turbulence models should be corrected for superlaminar flow. However, several corrections, such as transition correction, are unsuitable. Among all the flow models, the SST model with low-Re correction exhibits the best pressure distribution and turbulence viscosity ratio. Velocity profile analysis confirms that a buffer layer plays an important role in the superlaminar boundary layer. Classical fully developed turbulence models cannot accurately predict the buffer layer, but this problem can be resolved by initiating an appropriate low-Re correction. Therefore, the SST model with low-Re correction yields suitable results for superlaminar flows in bearings.
Numerical study of the spin-1 Ashkin-Teller model
International Nuclear Information System (INIS)
Bekhechi, S.; Badehdah, M.; Benyoussef, A.; Ettaki, B.
1998-07-01
Two non perturbative methods by means of the Transfer-Matrix Finite-Size-Scaling (TMFSS) and Monte Carlo (MC) simulations are used to investigate the spin-1 Ashkin-Teller model (A.T.M.). We have obtained rich phase diagrams with first and second order phase transitions with several multicritical points of higher order. Also this model exhibits a new partially ordered phase PO2 which does not exist in the spin-1/2 Ashkin-Teller model (A.T.M.). Finally, the critical behaviour of this model is discussed. (author)
A numerical shoreline model for shorelines with large curvature
DEFF Research Database (Denmark)
Kærgaard, Kasper Hauberg; Fredsøe, Jørgen
2013-01-01
orthogonal horizontal directions are used. The volume error in the sediment continuity equation which is thereby introduced is removed through an iterative procedure. The model treats the shoreline changes by computing the sediment transport in a 2D coastal area model, and then integrating the sediment...
Numerical Modelling of Drawbeads for Forming of Aluminium Alloys
DEFF Research Database (Denmark)
Joshi, Y; Christiansen, Peter; Masters, I
2016-01-01
from different semi-circular drawbead geometries commonly encountered in automotive dies and compares them to those obtained from Stoughton’s analytical drawbead model and the 2D plane strain drawbead model set up using LS-DYNA.The study was conducted on lubricated NG5754 strips. The results presented...
Numerical modeling of shoreline undulations part 1: Constant wave climate
DEFF Research Database (Denmark)
Kærgaard, Kasper Hauberg; Fredsøe, Jørgen
2013-01-01
integrated flow model, a wave-phase resolving sediment transport description and a one-line shoreline model.First the length of the shoreline undulations is determined in the linear regime using a stability analysis. Next the further evolution from the linear to the fully non-linear regime is described...
The Rigor Mortis of Education: Rigor Is Required in a Dying Educational System
Mixon, Jason; Stuart, Jerry
2009-01-01
In an effort to answer the "Educational Call to Arms", our national public schools have turned to Advanced Placement (AP) courses as the predominate vehicle used to address the lack of academic rigor in our public high schools. Advanced Placement is believed by many to provide students with the rigor and work ethic necessary to…
Evaluation of kinetic uncertainty in numerical models of petroleum generation
Peters, K.E.; Walters, C.C.; Mankiewicz, P.J.
2006-01-01
Oil-prone marine petroleum source rocks contain type I or type II kerogen having Rock-Eval pyrolysis hydrogen indices greater than 600 or 300-600 mg hydrocarbon/g total organic carbon (HI, mg HC/g TOC), respectively. Samples from 29 marine source rocks worldwide that contain mainly type II kerogen (HI = 230-786 mg HC/g TOC) were subjected to open-system programmed pyrolysis to determine the activation energy distributions for petroleum generation. Assuming a burial heating rate of 1??C/m.y. for each measured activation energy distribution, the calculated average temperature for 50% fractional conversion of the kerogen in the samples to petroleum is approximately 136 ?? 7??C, but the range spans about 30??C (???121-151??C). Fifty-two outcrop samples of thermally immature Jurassic Oxford Clay Formation were collected from five locations in the United Kingdom to determine the variations of kinetic response for one source rock unit. The samples contain mainly type I or type II kerogens (HI = 230-774 mg HC/g TOC). At a heating rate of 1??C/m.y., the calculated temperatures for 50% fractional conversion of the Oxford Clay kerogens to petroleum differ by as much as 23??C (127-150??C). The data indicate that kerogen type, as defined by hydrogen index, is not systematically linked to kinetic response, and that default kinetics for the thermal decomposition of type I or type II kerogen can introduce unacceptable errors into numerical simulations. Furthermore, custom kinetics based on one or a few samples may be inadequate to account for variations in organofacies within a source rock. We propose three methods to evaluate the uncertainty contributed by kerogen kinetics to numerical simulations: (1) use the average kinetic distribution for multiple samples of source rock and the standard deviation for each activation energy in that distribution; (2) use source rock kinetics determined at several locations to describe different parts of the study area; and (3) use a weighted
Roles that numerical models can play in emergency response
International Nuclear Information System (INIS)
Dickerson, M.H.
1982-03-01
Four points are presented with regard to a perspective on modeling for emergency preparedness. First, and probably foremost, modeling should be considered a tool, along with measurements and experience when used for emergency preparedness. The second point is that the potential for large errors associated with knowing the source term during an accident should not be used as a guide for determining the level of the model development and application. There are many other uses for models than estimating consequences, given the source term. These uses range from estimating the source term to bracketing the problem at hand. The third point is that several levels of model complexity should be considered when addressing emergency response. These levels can vary from the simple Gaussian calculation to the more complex three-dimensional transport and diffusion calculations where terrain and vertical and horizontal shears in the wind fields can be modeled. Lastly, proper interaction and feedback between model results and measurements enhances the capabilities of each if they were applied independently for emergency response purposes
Numerical modelling of present and future hydrology at Laxemar- Simpevarp
International Nuclear Information System (INIS)
Sassner, Mona; Sabel, Ulrika; Bosson, Emma; Berglund, Sten
2011-04-01
The Swedish Nuclear Fuel and Waste Management Company (SKB) has performed site investigations at two potential sites for a final repository for spent nuclear fuel. This report presents results of water flow modelling of the Laxemar area. The modelling reported in this document is focused on the near-surface groundwater, i.e. groundwater in Quaternary deposits and shallow rock, and surface water systems, and was performed using the MIKE SHE tool. The main objective of the modelling was to provide input to the radionuclide transport and dose calculations that were carried out as a part of the comparison between the Laxemar and Forsmark sites
Numerical modelling of present and future hydrology at Laxemar- Simpevarp
Energy Technology Data Exchange (ETDEWEB)
Sassner, Mona; Sabel, Ulrika (DHI Sverige AB (Sweden)); Bosson, Emma; Berglund, Sten (Svensk Kaernbraenslehantering AB (Sweden))
2011-04-15
The Swedish Nuclear Fuel and Waste Management Company (SKB) has performed site investigations at two potential sites for a final repository for spent nuclear fuel. This report presents results of water flow modelling of the Laxemar area. The modelling reported in this document is focused on the near-surface groundwater, i.e. groundwater in Quaternary deposits and shallow rock, and surface water systems, and was performed using the MIKE SHE tool. The main objective of the modelling was to provide input to the radionuclide transport and dose calculations that were carried out as a part of the comparison between the Laxemar and Forsmark sites
Approximate deconvolution models of turbulence analysis, phenomenology and numerical analysis
Layton, William J
2012-01-01
This volume presents a mathematical development of a recent approach to the modeling and simulation of turbulent flows based on methods for the approximate solution of inverse problems. The resulting Approximate Deconvolution Models or ADMs have some advantages over more commonly used turbulence models – as well as some disadvantages. Our goal in this book is to provide a clear and complete mathematical development of ADMs, while pointing out the difficulties that remain. In order to do so, we present the analytical theory of ADMs, along with its connections, motivations and complements in the phenomenology of and algorithms for ADMs.
Improved numerical solutions for chaotic-cancer-model
Directory of Open Access Journals (Sweden)
Muhammad Yasir
2017-01-01
Full Text Available In biological sciences, dynamical system of cancer model is well known due to its sensitivity and chaoticity. Present work provides detailed computational study of cancer model by counterbalancing its sensitive dependency on initial conditions and parameter values. Cancer chaotic model is discretized into a system of nonlinear equations that are solved using the well-known Successive-Over-Relaxation (SOR method with a proven convergence. This technique enables to solve large systems and provides more accurate approximation which is illustrated through tables, time history maps and phase portraits with detailed analysis.
Improved numerical solutions for chaotic-cancer-model
Yasir, Muhammad; Ahmad, Salman; Ahmed, Faizan; Aqeel, Muhammad; Akbar, Muhammad Zubair
2017-01-01
In biological sciences, dynamical system of cancer model is well known due to its sensitivity and chaoticity. Present work provides detailed computational study of cancer model by counterbalancing its sensitive dependency on initial conditions and parameter values. Cancer chaotic model is discretized into a system of nonlinear equations that are solved using the well-known Successive-Over-Relaxation (SOR) method with a proven convergence. This technique enables to solve large systems and provides more accurate approximation which is illustrated through tables, time history maps and phase portraits with detailed analysis.
Trends: Rigor Mortis in the Arts.
Blodget, Alden S.
1991-01-01
Outlines how past art education provided a refuge for students from the rigors of other academic subjects. Observes that in recent years art education has become "discipline based." Argues that art educators need to reaffirm their commitment to a humanistic way of knowing. (KM)
Numerical Modeling of Transient Heat Transfer in Longitudinal Fin
Directory of Open Access Journals (Sweden)
Farshad Panahizadeh
2017-11-01
Full Text Available The main objective of the present numerical study is to investigate the transient heat transfer in one kind of all-purpose longitudinal fin with the triangular profile. The lateral surface of the concerned fin and the tip of it are subjected to general situations included heat flux at the base and insulation on the tip. For this study developed a one dimensional in house code written by Fortran 90 programming language by using finite difference method with an implicit scheme in unsteady state condition. Generally, the result of this study in time variation state after 700 seconds is steady. The results also show the fin efficiency by increasing the time of study decreases due to a reduction in the total heat transfer which is happened in the fin. The grid independence study shows that for the number of nodes greater than 20 the result will not be changed and same as before. Finally, the result of Fortran code verified by commercial CFD code which relies on finite difference method and it was shown have a consistent agreement
Numerical modeling of isothermal compositional grading by convex splitting methods
Li, Yiteng
2017-04-09
In this paper, an isothermal compositional grading process is simulated based on convex splitting methods with the Peng-Robinson equation of state. We first present a new form of gravity/chemical equilibrium condition by minimizing the total energy which consists of Helmholtz free energy and gravitational potential energy, and incorporating Lagrange multipliers for mass conservation. The time-independent equilibrium equations are transformed into a system of transient equations as our solution strategy. It is proved our time-marching scheme is unconditionally energy stable by the semi-implicit convex splitting method in which the convex part of Helmholtz free energy and its derivative are treated implicitly and the concave parts are treated explicitly. With relaxation factor controlling Newton iteration, our method is able to converge to a solution with satisfactory accuracy if a good initial estimate of mole compositions is provided. More importantly, it helps us automatically split the unstable single phase into two phases, determine the existence of gas-oil contact (GOC) and locate its position if GOC does exist. A number of numerical examples are presented to show the performance of our method.
Global and Arctic climate engineering: numerical model studies.
Caldeira, Ken; Wood, Lowell
2008-11-13
We perform numerical simulations of the atmosphere, sea ice and upper ocean to examine possible effects of diminishing incoming solar radiation, insolation, on the climate system. We simulate both global and Arctic climate engineering in idealized scenarios in which insolation is diminished above the top of the atmosphere. We consider the Arctic scenarios because climate change is manifesting most strongly there. Our results indicate that, while such simple insolation modulation is unlikely to perfectly reverse the effects of greenhouse gas warming, over a broad range of measures considering both temperature and water, an engineered high CO2 climate can be made much more similar to the low CO2 climate than would be a high CO2 climate in the absence of such engineering. At high latitudes, there is less sunlight deflected per unit albedo change but climate system feedbacks operate more powerfully there. These two effects largely cancel each other, making the global mean temperature response per unit top-of-atmosphere albedo change relatively insensitive to latitude. Implementing insolation modulation appears to be feasible.
Numerical Model for Solidification Zones Selection in the Large Ingots
Directory of Open Access Journals (Sweden)
Wołczyński W.
2015-12-01
Full Text Available A vertical cut at the mid-depth of the 15-ton forging steel ingot has been performed by curtesy of the CELSA - Huta Ostrowiec plant. Some metallographic studies were able to reveal not only the chilled undersized grains under the ingot surface but columnar grains and large equiaxed grains as well. Additionally, the structural zone within which the competition between columnar and equiaxed structure formation was confirmed by metallography study, was also revealed. Therefore, it seemed justified to reproduce some of the observed structural zones by means of numerical calculation of the temperature field. The formation of the chilled grains zone is the result of unconstrained rapid solidification and was not subject of simulation. Contrary to the equiaxed structure formation, the columnar structure or columnar branched structure formation occurs under steep thermal gradient. Thus, the performed simulation is able to separate both discussed structural zones and indicate their localization along the ingot radius as well as their appearance in term of solidification time.
Observations and Numerical Modeling of the Jovian Ribbon
Cosentino, R. G.; Simon, A.; Morales-Juberias, R.; Sayanagi, K. M.
2015-01-01
Multiple wavelength observations made by the Hubble Space Telescope in early 2007 show the presence of a wavy, high-contrast feature in Jupiter's atmosphere near 30 degrees North. The "Jovian Ribbon," best seen at 410 nanometers, irregularly undulates in latitude and is time-variable in appearance. A meridional intensity gradient algorithm was applied to the observations to track the Ribbon's contour. Spectral analysis of the contour revealed that the Ribbon's structure is a combination of several wavenumbers ranging from k equals 8-40. The Ribbon is a dynamic structure that has been observed to have spectral power for dominant wavenumbers which vary over a time period of one month. The presence of the Ribbon correlates with periods when the velocity of the westward jet at the same location is highest. We conducted numerical simulations to investigate the stability of westward jets of varying speed, vertical shear, and background static stability to different perturbations. A Ribbon-like morphology was best reproduced with a 35 per millisecond westward jet that decreases in amplitude for pressures greater than 700 hectopascals and a background static stability of N equals 0.005 per second perturbed by heat pulses constrained to latitudes south of 30 degrees North. Additionally, the simulated feature had wavenumbers that qualitatively matched observations and evolved throughout the simulation reproducing the Jovian Ribbon's dynamic structure.
Numerical modelling of CIGS/CdS solar cell
Devi, Nisha; Aziz, Anver; Datta, Shouvik
2018-05-01
In this work, we design and analyze the Cu(In,Ga)Se2 (CIGS) solar cell using simulation software "Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D)". The conventional CIGS solar cell uses various layers, like intrinsic ZnO/Aluminium doped ZnO as transparent oxide, antireflection layer MgF2, and electron back reflection (EBR) layer at CIGS/Mo interface for good power conversion efficiency. We replace this conventional model by a simple model which is easy to fabricate and also reduces the cost of this cell because of use of lesser materials. The new designed model of CIGS solar cell is ITO/CIGS/OVC/CdS/Metal contact, where OVC is ordered vacancy compound. From this simple structure, even at very low illumination we are getting good results. We simulate this CIGS solar cell model by varying various physical parameters of CIGS like thickness, carrier density, band gap and temperature.
Numerical modelling of cold compaction of metal powder
DEFF Research Database (Denmark)
Redanz, Pia
1998-01-01
A finite element programme has been developed for the analysis of porosity and stress distributions in a powder compact, based on rate-independent finite strain plasticity theory. The strain hardening versions of the Gurson model (J. Engng. Mater. Technol., 1977, 99, 2-15), the more recent FKM...... friction is not realistic at high normal pressures. The finite element programme has been used to study the effects of friction, compaction method, and material parameters. Analyses for powder compacts of various geometries are presented to illustrate the method. (C) 1998 Elsevier Science Ltd. All rights...... model (J. Mech. Phys. Solids, 1992, 40(5), 1139-1162), developed by Fleck, Kuhr. and McMeeking, and a combination of the two models are used. The friction between the mould wall and the metal powder is modelled by a combination of Coulomb friction and a constant friction shear stress, since Coulomb...
Ultrasonic-assisted manufacturing processes: Variational model and numerical simulations
Siddiq, Amir; El Sayed, Tamer
2012-01-01
We present a computational study of ultrasonic assisted manufacturing processes including sheet metal forming, upsetting, and wire drawing. A fully variational porous plasticity model is modified to include ultrasonic softening effects
Numerical Speadsheet Modeling of Natural Attenuation for Groundwater Contaminant Plumes
National Research Council Canada - National Science Library
Twesme, Troy
1999-01-01
.... The model was used to evaluate natural attenuation for removal of a trichloroethylene (TCE) plume from a surficial aquifer containing three regions with distinctly different processes for degradation of TCE...
A numerical storm surge forecast model with Kalman filter
Institute of Scientific and Technical Information of China (English)
Yu Fujiang; Zhang Zhanhai; Lin Yihua
2001-01-01
Kalman filter data assimilation technique is incorporated into a standard two-dimensional linear storm surge model. Imperfect model equation and imperfect meteorological forcimg are accounted for by adding noise terms to the momentum equations. The deterministic model output is corrected by using the available tidal gauge station data. The stationary Kalman filter algorithm for the model domain is calculated by an iterative procedure using specified information on the inaccuracies in the momentum equations and specified error information for the observations. An application to a real storm surge that occurred in the summer of 1956 in the East China Sea is performed by means of this data assimilation technique. The result shows that Kalman filter is useful for storm surge forecast and hindcast.
Mathematical modelling and numerical simulation of forces in milling process
Turai, Bhanu Murthy; Satish, Cherukuvada; Prakash Marimuthu, K.
2018-04-01
Machining of the material by milling induces forces, which act on the work piece material, tool and which in turn act on the machining tool. The forces involved in milling process can be quantified, mathematical models help to predict these forces. A lot of research has been carried out in this area in the past few decades. The current research aims at developing a mathematical model to predict forces at different levels which arise machining of Aluminium6061 alloy. Finite element analysis was used to develop a FE model to predict the cutting forces. Simulation was done for varying cutting conditions. Different experiments was designed using Taguchi method. A L9 orthogonal array was designed and the output was measure for the different experiments. The same was used to develop the mathematical model.
Numerical modelling of seawater intrusion in Shenzhen (China ...
Indian Academy of Sciences (India)
obtained by a manual trial-and-error method. ... model researchers and managers. Due to its ... social development at the coastal area in Shenzhen city. ..... The qualitative measure com- ... analysis and the quantitative one in a regression.
Concept of a cognitive-numeric plant and process modelizer
International Nuclear Information System (INIS)
Vetterkind, D.
1990-01-01
To achieve automatic modeling of plant distrubances and failure limitation procedures, first the system's hardware and the present media (water, steam, coolant fluid) are formalized into fully computable matrices, called topographies. Secondly a microscopic cellular automation model, using lattice gases and state transition rules, is combined with a semi - microscopic cellular process model and with a macroscopic model, too. In doing this, at semi-microscopic level there are acting a cellular data compressor, a feature detection device and the Intelligent Physical Element's process dynamics. At macroscopic level the Walking Process Elements, a process evolving module, a test-and-manage device and abstracting process net are involved. Additionally, a diagnosis-coordinating and a counter measurements coordinating device are used. In order to automatically get process insights, object transformations, elementary process functions and associative methods are used. Developments of optoelectronic hardware language components are under consideration
Numerical modeling of aluminium foam on two scales
Czech Academy of Sciences Publication Activity Database
Němeček, J.; Denk, F.; Zlámal, Petr
Roč. 267, September (2015), s. 506-516 ISSN 0096-3003 R&D Projects: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : closed-cell aluminium foam * Alporas * multiscale modeling * homogenization * FFT * finite element modeling Subject RIV: JI - Composite Materials Impact factor: 1.345, year: 2015 http://www.sciencedirect.com/science/article/pii/S0096300315001162
Numerical Analysis of Fractional Order Epidemic Model of Childhood Diseases
Directory of Open Access Journals (Sweden)
Fazal Haq
2017-01-01
Full Text Available The fractional order Susceptible-Infected-Recovered (SIR epidemic model of childhood disease is considered. Laplace–Adomian Decomposition Method is used to compute an approximate solution of the system of nonlinear fractional differential equations. We obtain the solutions of fractional differential equations in the form of infinite series. The series solution of the proposed model converges rapidly to its exact value. The obtained results are compared with the classical case.