Numerical and Analytical Study of Optimal Low-Thrust Limited-Power Transfers between Close Circular Coplanar Orbits

Directory of Open Access Journals (Sweden)

Sandro da Silva Fernandes

2007-01-01

Full Text Available A numerical and analytical study of optimal low-thrust limited-power trajectories for simple transfer (no rendezvous between close circular coplanar orbits in an inverse-square force field is presented. The numerical study is carried out by means of an indirect approach of the optimization problem in which the two-point boundary value problem, obtained from the set of necessary conditions describing the optimal solutions, is solved through a neighboring extremal algorithm based on the solution of the linearized two-point boundary value problem through Riccati transformation. The analytical study is provided by a linear theory which is expressed in terms of nonsingular elements and is determined through the canonical transformation theory. The fuel consumption is taken as the performance criterion and the analysis is carried out considering various radius ratios and transfer durations. The results are compared to the ones provided by a numerical method based on gradient techniques.

Key issues review: numerical studies of turbulence in stars

Science.gov (United States)

Arnett, W. David; Meakin, Casey

2016-10-01

Three major problems of single-star astrophysics are convection, magnetic fields and rotation. Numerical simulations of convection in stars now have sufficient resolution to be truly turbulent, with effective Reynolds numbers of \\text{Re}>{{10}4} , and some turbulent boundary layers have been resolved. Implications of these developments are discussed for stellar structure, evolution and explosion as supernovae. Methods for three-dimensional (3D) simulations of stars are compared and discussed for 3D atmospheres, solar rotation, core-collapse and stellar boundary layers. Reynolds-averaged Navier-Stokes (RANS) analysis of the numerical simulations has been shown to provide a novel and quantitative estimate of resolution errors. Present treatments of stellar boundaries require revision, even for early burning stages (e.g. for mixing regions during He-burning). As stellar core-collapse is approached, asymmetry and fluctuations grow, rendering spherically symmetric models of progenitors more unrealistic. Numerical resolution of several different types of three-dimensional (3D) stellar simulations are compared; it is suggested that core-collapse simulations may be under-resolved. The Rayleigh-Taylor instability in explosions has a deep connection to convection, for which the abundance structure in supernova remnants may provide evidence.

Analytic and numerical studies of Scyllac equilibrium

International Nuclear Information System (INIS)

Barnes, D.C.; Brackbill, J.U.; Dagazian, R.Y.; Freidberg, J.P.; Schneider, W.; Betancourt, O.; Garabedian, P.

1976-01-01

The results of both numerical and analytic studies of the Scyllac equilibria are presented. Analytic expansions are used to derive equilibrium equations appropriate to noncircular cross sections, and compute the stellarator fields which produce toroidal force balance. Numerical algorithms are used to solve both the equilibrium equations and the full system of dynamical equations in three dimensions. Numerical equilibria are found for both l = 1,0 and l= 1,2 systems. It is found that the stellarator fields which produce equilibria in the l = 1.0 system are larger for diffuse than for sharp boundary plasma profiles, and that the stability of the equilibria depends strongly on the harmonic content of the stellarator fields

Numerical studies of fermionic field theories at large-N

International Nuclear Information System (INIS)

Dickens, T.A.

1987-01-01

A description of an algorithm, which may be used to study large-N theories with or without fermions, is presented. As an initial test of the method, the spectrum of continuum QCD in 1 + 1 dimensions is determined and compared to previously obtained results. Exact solutions of 1 + 1 dimensional lattice versions of the free fermion theory, the Gross-Neveu model, and QCD are obtained. Comparison of these exact results with results from the numerical algorithm is used to test the algorithms, and more importantly, to determine the errors incurred from the approximations used in the numerical technique. Numerical studies of the above three lattice theories in higher dimensions are also presented. The results are again compared to exact solutions for free fermions and the Gross-Neveu model; perturbation theory is used to derive expansions with which the numerical results for QCD may be compared. The numerical algorithm may also be used to study the euclidean formulation of lattice gauge theories. Results for 1 + 1 dimensional euclidean lattice QCD are compared to the exact solution of this model

Numerical Study of Traffic Pollutant Dispersion within Different Street Canyon Configurations

Directory of Open Access Journals (Sweden)

Yucong Miao

2014-01-01

Full Text Available The objective of this study is to numerically study flow and traffic exhaust dispersion in urban street canyons with different configurations to find out the urban-planning strategies to ease the air pollution. The Computational Fluid Dynamics (CFD model used in this study—Open Source Field Operation and Manipulation (OpenFOAM software package—was firstly validated against the wind-tunnel experiment data by using three different k-ε turbulence models. And then the patterns of flow and dispersion within three different kinds of street canyon configuration under the perpendicular approaching flow were numerically studied. The result showed that the width and height of building can dramatically affect the pollution level inside the street canyon. As the width or height of building increases, the pollution at the pedestrian level increases. And the asymmetric configuration (step-up or step-down street canyon could provide better ventilation. It is recommended to design a street canyon with nonuniform configurations. And the OpenFOAM software package can be used as a reliable tool to study flows and dispersions around buildings.

Introduction to precise numerical methods

CERN Document Server

Aberth, Oliver

2007-01-01

Precise numerical analysis may be defined as the study of computer methods for solving mathematical problems either exactly or to prescribed accuracy. This book explains how precise numerical analysis is constructed. The book also provides exercises which illustrate points from the text and references for the methods presented. All disc-based content for this title is now available on the Web. · Clearer, simpler descriptions and explanations ofthe various numerical methods· Two new types of numerical problems; accurately solving partial differential equations with the included software and computing line integrals in the complex plane.

Numerical study on lateral wall displacement of deep excavation supported by IPS earth retention system

Directory of Open Access Journals (Sweden)

Tugen Feng

2017-12-01

Full Text Available The objective of this study is to investigate the 3D behavior characteristics of an excavation supported by an innovative prestressed support (IPS earth retention system. A numerical simulation was conducted in order to provide insight into the IPS system behavior by using the FLAC3D package. Prior to the parametric study, validation work was conducted by means of a comparison of the deformation between the field test data and numerical analysis results, and strong agreement was obtained. The reasonable excavation location, layered excavation thickness, and blocked excavation sequence are presented according to variable parameter analysis. In view of the previous findings, certain measurements are proposed in order to control the foundation pit deformation. The results indicate that prestress compensation has a significant effect on the IPS system behavior, while an optimized excavation sequence slightly improves its behavior. With the conclusion proposed based on the numerical results, the aim is to provide reference data for optimization design and the construction sequence. Keywords: FLAC3D, IPS system, Prestress compensation, Layered excavation, Blocked excavation, Deformation control

Numerical case studies of vertical wall fire protection using water spray

Directory of Open Access Journals (Sweden)

L.M. Zhao

2014-11-01

Full Text Available Studies of vertical wall fire protection are evaluated with numerical method. Typical fire cases such as heated dry wall and upward flame spread have been validated. Results predicted by simulations are found to agree with experiment results. The combustion behavior and flame development of vertical polymethylmethacrylate slabs with different water flow rates are explored and discussed. Water spray is found to be capable of strengthening the fire resistance of combustible even under high heat flux radiation. Provided result and data are expected to provide reference for fire protection methods design and development of modern buildings.

Market competition, ownership, payment systems and the performance of health care providers - a panel study among Finnish occupational health services providers.

Science.gov (United States)

Kankaanpää, Eila; Linnosmaa, Ismo; Valtonen, Hannu

2013-10-01

Many health care reforms rely on competition although health care differs in many respects from the assumptions of perfect competition. Finnish occupational health services provide an opportunity to study empirically competition, ownership and payment systems and the performance of providers. In these markets employers (purchasers) choose the provider and prices are market determined. The price regulation of public providers was abolished in 1995. We had data on providers from 1992, 1995, 1997, 2000 and 2004. The unbalanced panel consisted of 1145 providers and 4059 observations. Our results show that in more competitive markets providers in general offered a higher share of medical care compared to preventive services. The association between unit prices and revenues and market environment varied according to the provider type. For-profit providers had lower prices and revenues in markets with numerous providers. The public providers in more competitive regions were more sensitive to react to the abolishment of their price regulation by raising their prices. Employer governed providers had weaker association between unit prices or revenues and competition. The market share of for-profit providers was negatively associated with productivity, which was the only sign of market spillovers we found in our study.

Semi-Numerical Studies of the Three-Meter Spherical Couette Experiment Utilizing Data Assimilation

Science.gov (United States)

Burnett, Sarah; Rojas, Ruben; Perevalov, Artur; Lathrop, Daniel; Ide, Kayo; Schaeffer, Nathanael

2017-11-01

The model of the Earth's magnetic field has been investigated in recent years through experiments and numerical models. At the University of Maryland, experimental studies are implemented in a three-meter spherical Couette device filled with liquid sodium. The inner and outer spheres of this apparatus mimic the planet's inner core and core-mantle boundary, respectively. These experiments incorporate high velocity flows with Reynolds numbers 108 . In spherical Couette geometry, the numerical scheme applied to this work features finite difference methods in the radial direction and pseudospectral spherical harmonic transforms elsewhere. Adding to the numerical model, data assimilation integrates the experimental outer-layer magnetic field measurements. This semi-numerical model can then be compared to the experimental results as well as forecasting magnetic field changes. Data assimilation makes it possible to get estimates of internal motions of the three-meter experiment that would otherwise be intrusive or impossible to obtain in experiments or too computationally expensive with a purely numerical code. If we can provide accurate models of the three-meter device, it is possible to attempt to model the geomagnetic field. We gratefully acknowledge the support of NSF Grant No. EAR1417148 & DGE1322106.

Optimal control approaches for aircraft conflict avoidance using speed regulation : a numerical study

OpenAIRE

Cellier , Loïc; Cafieri , Sonia; Messine , Frederic

2013-01-01

International audience; In this paper a numerical study is provided to solve the aircraft conflict avoidance problem through velocity regulation maneuvers. Starting from optimal controlbased model and approaches in which aircraft accelerations are the controls, and by applying the direct shooting technique, we propose to study two different largescale nonlinear optimization problems. In order to compare different possibilities of implementation, two environments (AMPL and MATLAB) and determin...

Theoretical and numerical study of highly anisotropic turbulent flows

NARCIS (Netherlands)

Biferale, L.; Daumont, I.; Lanotte, A.; Toschi, F.

2004-01-01

We present a detailed numerical study of anisotropic statistical fluctuations in stationary, homogeneous turbulent flows. We address both problems of intermittency in anisotropic sectors, and the relative importance of isotropic and anisotropic fluctuations at different scales on a direct numerical

Experimental and numerical studies on free surface flow of windowless target

International Nuclear Information System (INIS)

Su, G.Y.; Gu, H.Y.; Cheng, X.

2012-01-01

Highlights: ► Experimental and CFD studies on free surface flow have been performed in a scaled windowless target. ► Flow structure inside spallation area can be divided into three typical zones. ► Under large Reynolds number, large scale vortex can be observed. ► CFD studies have been conducted by using both LES and RANS (k-ω SST) turbulence models. ► LES model provides better numerical prediction on free surface behavior and flow transient. - Abstract: The formation and control method of the coolant free surface is one of the key technologies for the design of windowless targets in the accelerator driven system (ADS). In the recent study, experimental and numerical investigations on the free surface flow have been performed in a scaled windowless target by using water as the model fluid. The planar laser induced fluorescence technique has been applied to visualize the free surface flow pattern inside the spallation area. Experiments have been carried out with the Reynolds number in the range of 30,000–50,000. The structure and features of flow vortex have been investigated. The experimental results show that the free surface is vulnerable to the vortex movement. In addition, CFD simulations have been performed under the experimental conditions, using LES and RANS (k-ω SST) turbulence models, respectively. The numerical results of LES model agree qualitatively well with the experimental data related to both flow pattern and free surface behavior.

Preliminary Study of 1D Thermal-Hydraulic System Analysis Code Using the Higher-Order Numerical Scheme

Energy Technology Data Exchange (ETDEWEB)

Lee, Won Woong; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-05-15

The existing nuclear system analysis codes such as RELAP5, TRAC, MARS and SPACE use the first-order numerical scheme in both space and time discretization. However, the first-order scheme is highly diffusive and less accurate due to the first order of truncation error. So, the numerical diffusion problem which makes the gradients to be smooth in the regions where the gradients should be steep can occur during the analysis, which often predicts less conservatively than the reality. Therefore, the first-order scheme is not always useful in many applications such as boron solute transport. RELAP7 which is an advanced nuclear reactor system safety analysis code using the second-order numerical scheme in temporal and spatial discretization is being developed by INL (Idaho National Laboratory) since 2011. Therefore, for better predictive performance of the safety of nuclear reactor systems, more accurate nuclear reactor system analysis code is needed for Korea too to follow the global trend of nuclear safety analysis. Thus, this study will evaluate the feasibility of applying the higher-order numerical scheme to the next generation nuclear system analysis code to provide the basis for the better nuclear system analysis code development. The accuracy is enhanced in the spatial second-order scheme and the numerical diffusion problem is alleviated while indicates significantly lower maximum Courant limit and the numerical dispersion issue which produces spurious oscillation and non-physical results in the higher-order scheme. If the spatial scheme is the first order scheme then the temporal second-order scheme provides almost the same result with the temporal firstorder scheme. However, when the temporal second order scheme and the spatial second-order scheme are applied together, the numerical dispersion can occur more severely. For the more in-depth study, the verification and validation of the NTS code built in MATLAB will be conducted further and expanded to handle two

Numerical study for two phase flow in the near nozzle region of turbine combustors

International Nuclear Information System (INIS)

Pervez, K.; Mushtaq, S.

1999-01-01

In the present study flow conditions in the near nozzle region of the combustion chamber have been investigated. There exists two-phase flow in this region. The overall performance and pollutant formation in the combustion chamber have been investigated. There exists two-phase flow in this region. The overall performance and pollutant formation in the combustion zone largely depends on the spray field in the near nozzle region the studies are conducted to determined the effects of multi jets on the flow pattern in the near nozzle region The phase doppler particle analyzer (PDPA) has been used to measure the velocities and sizes of the droplets. The flow field of two-phase liquid drop-air jets is formed from three injectors arranged in t line. Furthermore the two-phase flow field has been analyzed numerically also. The numerical analysis consists of two computational models, namely (i) 3 non-evaporating two-phase jets, (II) 3 evaporating two phase jets. The Eulerian-Eulerian approach in incorporated in both the numerical models. Since the flow is turbulent, a two-equation model (k-Epsilon) is implemented in the numerical analysis. Numerical solution of the conservation equation is obtained using PHOENICS computer code. Boundary conditions are provided from the experimental measurements. Numerical domain for the two models of the analysis starts at some distance (about 10 diameters of the injector orifice) where the atomization process is complete and droplet size and velocity could be measured experimentally. (author)

Semi-Numerical Studies of the Three-Meter Spherical Couette Experiment Utilizing Data Assimilation

Science.gov (United States)

Burnett, S. C.; Rojas, R.; Perevalov, A.; Lathrop, D. P.

2017-12-01

The model of the Earth's magnetic field has been investigated in recent years through experiments and numerical models. At the University of Maryland, experimental studies are implemented in a three-meter spherical Couette device filled with liquid sodium. The inner and outer spheres of this apparatus mimic the planet's inner core and core-mantle boundary, respectively. These experiments incorporate high velocity flows with Reynolds numbers 108. In spherical Couette geometry, the numerical scheme applied to this work features finite difference methods in the radial direction and pseudospectral spherical harmonic transforms elsewhere [Schaeffer, N. G3 (2013)]. Adding to the numerical model, data assimilation integrates the experimental outer-layer magnetic field measurements. This semi-numerical model can then be compared to the experimental results as well as forecasting magnetic field changes. Data assimilation makes it possible to get estimates of internal motions of the three-meter experiment that would otherwise be intrusive or impossible to obtain in experiments or too computationally expensive with a purely numerical code. If we can provide accurate models of the three-meter device, it is possible to attempt to model the geomagnetic field. We gratefully acknowledge the support of NSF Grant No. EAR1417148 & DGE1322106.

Numerical study of wave propagation around an underground cavity: acoustic case

Science.gov (United States)

Esterhazy, Sofi; Perugia, Ilaria; Schöberl, Joachim; Bokelmann, Götz

2015-04-01

Motivated by the need to detect an underground cavity within the procedure of an On-Site-Inspection (OSI) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), which might be caused by a nuclear explosion/weapon testing, we aim to provide a basic numerical study of the wave propagation around and inside such an underground cavity. The aim of the CTBTO is to ban all nuclear explosions of any size anywhere, by anyone. Therefore, it is essential to build a powerful strategy to efficiently investigate and detect critical signatures such as gas filled cavities, rubble zones and fracture networks below the surface. One method to investigate the geophysical properties of an underground cavity allowed by the Comprehensive Nuclear-test Ban Treaty is referred to as 'resonance seismometry' - a resonance method that uses passive or active seismic techniques, relying on seismic cavity vibrations. This method is in fact not yet entirely determined by the Treaty and there are also only few experimental examples that have been suitably documented to build a proper scientific groundwork. This motivates to investigate this problem on a purely numerical level and to simulate these events based on recent advances in the mathematical understanding of the underlying physical phenomena. Here, we focus our numerical study on the propagation of P-waves in two dimensions. An extension to three dimensions as well as an inclusion of the full elastic wave field is planned in the following. For the numerical simulations of wave propagation we use a high order finite element discretization which has the significant advantage that it can be extended easily from simple toy designs to complex and irregularly shaped geometries without excessive effort. Our computations are done with the parallel Finite Element Library NGSOLVE ontop of the automatic 2D/3D tetrahedral mesh generator NETGEN (http://sourceforge.net/projects/ngsolve/). Using the basic mathematical understanding of the

Experimental and numerical study of a printed circuit heat exchanger

International Nuclear Information System (INIS)

Chen, Minghui; Sun, Xiaodong; Christensen, Richard N.; Shi, Shanbin; Skavdahl, Isaac; Utgikar, Vivek; Sabharwall, Piyush

2016-01-01

temperature increase and the other for helium inlet temperature decrease, were experimentally carried out to assess the applicability of the dynamic model. Comparisons of the numerical results with the experimental data show that the dynamic model is successful in predicting the experimental transient scenarios. Although difference was observed between the numerical results and experimental data, the comparisons suggest that the numerical solutions are sufficiently accurate and conservative and that the applicability of the dynamic model proposed for predicting the steady-state and transient performance of the straight-channel PCHE has been confirmed. Furthermore, both the numerical and experimental studies provide insights into the dynamic performance of the PCHE.

The interior of axisymmetric and stationary black holes: Numerical and analytical studies

International Nuclear Information System (INIS)

Ansorg, Marcus; Hennig, Joerg

2011-01-01

We investigate the interior hyperbolic region of axisymmetric and stationary black holes surrounded by a matter distribution. First, we treat the corresponding initial value problem of the hyperbolic Einstein equations numerically in terms of a single-domain fully pseudo-spectral scheme. Thereafter, a rigorous mathematical approach is given, in which soliton methods are utilized to derive an explicit relation between the event horizon and an inner Cauchy horizon. This horizon arises as the boundary of the future domain of dependence of the event horizon. Our numerical studies provide strong evidence for the validity of the universal relation A + A - (8πJ) 2 where A + and A - are the areas of event and inner Cauchy horizon respectively, and J denotes the angular momentum. With our analytical considerations we are able to prove this relation rigorously.

Numerical Studies of Homogenization under a Fast Cellular Flow

KAUST Repository

Iyer, Gautam

2012-09-13

We consider a two dimensional particle diffusing in the presence of a fast cellular flow confined to a finite domain. If the flow amplitude A is held fixed and the number of cells L 2 →∞, then the problem homogenizes; this has been well studied. Also well studied is the limit when L is fixed and A→∞. In this case the solution averages along stream lines. The double limit as both the flow amplitude A→∞and the number of cells L 2 →∞was recently studied [G. Iyer et al., preprint, arXiv:1108.0074]; one observes a sharp transition between the homogenization and averaging regimes occurring at A = L 2. This paper numerically studies a few theoretically unresolved aspects of this problem when both A and L are large that were left open in [G. Iyer et al., preprint, arXiv:1108.0074] using the numerical method devised in [G. A. Pavliotis, A. M. Stewart, and K. C. Zygalakis, J. Comput. Phys., 228 (2009), pp. 1030-1055]. Our treatment of the numerical method uses recent developments in the theory of modified equations for numerical integrators of stochastic differential equations [K. C. Zygalakis, SIAM J. Sci. Comput., 33 (2001), pp. 102-130]. © 2012 Society for Industrial and Applied Mathematics.

Numerical Studies of Homogenization under a Fast Cellular Flow

KAUST Repository

Iyer, Gautam; Zygalakis, Konstantinos C.

2012-01-01

We consider a two dimensional particle diffusing in the presence of a fast cellular flow confined to a finite domain. If the flow amplitude A is held fixed and the number of cells L 2 →∞, then the problem homogenizes; this has been well studied. Also well studied is the limit when L is fixed and A→∞. In this case the solution averages along stream lines. The double limit as both the flow amplitude A→∞and the number of cells L 2 →∞was recently studied [G. Iyer et al., preprint, arXiv:1108.0074]; one observes a sharp transition between the homogenization and averaging regimes occurring at A = L 2. This paper numerically studies a few theoretically unresolved aspects of this problem when both A and L are large that were left open in [G. Iyer et al., preprint, arXiv:1108.0074] using the numerical method devised in [G. A. Pavliotis, A. M. Stewart, and K. C. Zygalakis, J. Comput. Phys., 228 (2009), pp. 1030-1055]. Our treatment of the numerical method uses recent developments in the theory of modified equations for numerical integrators of stochastic differential equations [K. C. Zygalakis, SIAM J. Sci. Comput., 33 (2001), pp. 102-130]. © 2012 Society for Industrial and Applied Mathematics.

Numerical and Experimental Study of Amplitude Modulated Positive Corona Discharge

Directory of Open Access Journals (Sweden)

Pablo Martín GOMEZ

2014-12-01

Full Text Available The electrical behavior of a modulated positive corona discharge loudspeaker was studied. A coaxial transducer in air was built using a central copper wire of 75 mm radius (inner electrode and a perforated tube of 11 mm (outer electrode. A high voltage DC supply provided the bias current and a sinusoidal signal was superimposed to measure the discharge admittance. The experimental results could not be matched to previously reported equivalent circuits with fixed components. Using the basic equations that describe the ion motion, a numerical model was proposed. The computed values matched well the experimental data and suggested an equivalent circuit composed of frequency dependent conductance and capacitance. This dependence is closely related to the ion travel time between electrodes (transit time. Simulations carried out at several inter-electrode distances could be synthesized in a single plot where the different results overlap and further emphasize the role of the transit time. This numerical model proved to be an efficient tool to simulate and design modulated corona transducers.

Numerical study of the rising of the explosion clouds in different atmosphere

International Nuclear Information System (INIS)

Li Xiaoli; Zheng Yi; Chao Ying; Cao Yitang

2010-01-01

The rising of the explosion clouds in the uniform and normal atmosphere had been studied, the numerical model is based on the assumption that effects the clouds are gravity and buoyancy. The model is testified by Rayleigh-Taylor unsteady problem. The evolution of the density during the rising of the explosion clouds are provided, and the computational results indicates that the effects of the layered atmosphere mains the altitude of the cloud. (authors)

Biofouling in forward osmosis systems: An experimental and numerical study

KAUST Repository

Bucs, Szilard; Valladares Linares, Rodrigo; Vrouwenvelder, Johannes S.; Picioreanu, Cristian

2016-01-01

This study evaluates with numerical simulations supported by experimental data the impact of biofouling on membrane performance in a cross-flow forward osmosis (FO) system. The two-dimensional numerical model couples liquid flow with solute

Prediction of the time course of callus stiffness as a function of mechanical parameters in experimental rat fracture healing studies--a numerical study.

Directory of Open Access Journals (Sweden)

Tim Wehner

Full Text Available Numerous experimental fracture healing studies are performed on rats, in which different experimental, mechanical parameters are applied, thereby prohibiting direct comparison between each other. Numerical fracture healing simulation models are able to predict courses of fracture healing and offer support for pre-planning animal experiments and for post-hoc comparison between outcomes of different in vivo studies. The aims of this study are to adapt a pre-existing fracture healing simulation algorithm for sheep and humans to the rat, to corroborate it using the data of numerous different rat experiments, and to provide healing predictions for future rat experiments. First, material properties of different tissue types involved were adjusted by comparing experimentally measured callus stiffness to respective simulated values obtained in three finite element (FE models. This yielded values for Young's moduli of cortical bone, woven bone, cartilage, and connective tissue of 15,750 MPa, 1,000 MPa, 5 MPa, and 1 MPa, respectively. Next, thresholds in the underlying mechanoregulatory tissue differentiation rules were calibrated by modifying model parameters so that predicted fracture callus stiffness matched experimental data from a study that used rigid and flexible fixators. This resulted in strain thresholds at higher magnitudes than in models for sheep and humans. The resulting numerical model was then used to simulate numerous fracture healing scenarios from literature, showing a considerable mismatch in only 6 of 21 cases. Based on this corroborated model, a fit curve function was derived which predicts the increase of callus stiffness dependent on bodyweight, fixation stiffness, and fracture gap size. By mathematically predicting the time course of the healing process prior to the animal studies, the data presented in this work provides support for planning new fracture healing experiments in rats. Furthermore, it allows one to transfer and

Review of The SIAM 100-Digit Challenge: A Study in High-Accuracy Numerical Computing

International Nuclear Information System (INIS)

Bailey, David

2005-01-01

In the January 2002 edition of SIAM News, Nick Trefethen announced the '$100, 100-Digit Challenge'. In this note he presented ten easy-to-state but hard-to-solve problems of numerical analysis, and challenged readers to find each answer to ten-digit accuracy. Trefethen closed with the enticing comment: 'Hint: They're hard. If anyone gets 50 digits in total, I will be impressed.' This challenge obviously struck a chord in hundreds of numerical mathematicians worldwide, as 94 teams from 25 nations later submitted entries. Many of these submissions exceeded the target of 50 correct digits; in fact, 20 teams achieved a perfect score of 100 correct digits. Trefethen had offered $100 for the best submission. Given the overwhelming response, a generous donor (William Browning, founder of Applied Mathematics, Inc.) provided additional funds to provide a $100 award to each of the 20 winning teams. Soon after the results were out, four participants, each from a winning team, got together and agreed to write a book about the problems and their solutions. The team is truly international: Bornemann is from Germany, Laurie is from South Africa, Wagon is from the USA, and Waldvogel is from Switzerland. This book provides some mathematical background for each problem, and then shows in detail how each of them can be solved. In fact, multiple solution techniques are mentioned in each case. The book describes how to extend these solutions to much larger problems and much higher numeric precision (hundreds or thousands of digit accuracy). The authors also show how to compute error bounds for the results, so that one can say with confidence that one's results are accurate to the level stated. Numerous numerical software tools are demonstrated in the process, including the commercial products Mathematica, Maple and Matlab. Computer programs that perform many of the algorithms mentioned in the book are provided, both in an appendix to the book and on a website. In the process, the

Numerical Study of Electric Field Enhanced Combustion

KAUST Repository

Han, Jie

2016-12-26

Electric fields can be used to change and control flame properties, for example changing flame speed, enhancing flame stability, or reducing pollutant emission. The ions generated in flames are believed to play the primary role. Although experiments have been carried out to study electric field enhanced combustion, they are not sufficient to explain how the ions in a flame are affected by an electric field. It is therefore necessary to investigate the problem through numerical simulations. In the present work, the electric structure of stabilized CH4/air premixed flames at atmospheric pressure within a direct current field is studied using numerical simulations. This study consists of three parts. First, the transport equations are derived from the Boltzmann kinetic equation for each individual species. Second, a general method for computing the diffusivity and mobility of ions in a gas mixture is introduced. Third, the mechanisms for neutral and charged species are improved to give better predictions of the concentrations of charged species, based on experimental data. Following from this, comprehensive numerical results are presented, including the concentrations and fluxes of charged species, the distributions of the electric field and electric potential, and the electric current-voltage relation. Two new concepts introduced with the numerical results are the plasma sheath and dead zone in the premixed flame. A reactive plasma sheath and a Boltzmann relation sheath are discovered in the region near the electrodes. The plasma sheath penetrates into the flame gas when a voltage is applied, and penetrating further if the voltage is higher. The zone outside the region of sheath penetration is defined as the dead zone. With the two concepts, analytical solutions for the electric field, electric potential and current-voltage curve are derived. The solutions directly describe the electric structure of a premixed flame subject to a DC field. These analytical solutions

Numerical study of the characteristics of a dielectric barrier discharge plasma actuator

Science.gov (United States)

Shi, C. A.; Adamiak, K.; Castle, G. S. P.

2018-03-01

A dielectric barrier discharge actuator to control airflow along a flat dielectric plate has been numerically investigated in this paper. In order to avoid large computing times, streamers, Trichel pulses and the ionic reactions involving photons and electrons are neglected. The numerical model assumes two types of generic ions, one positive and one negative, whose drift in the electric field produces the electrohydrodynamic flow. This study provides detailed insights into the physical mechanisms of DBD that include the electric field, space charge transport, surface charge accumulation and air flow motion. The results show the V-I characteristics, velocity profiles and drag force estimates. In addition, the effects of the voltage level, frequency and inlet air velocity on the actuator performance are presented and interpreted. The simulation results show a good agreement with theoretical expectations and experimental data available in literature.

Numerical Model Study of the Tuscarawas River below Dover Dam, Ohio

Science.gov (United States)

2009-09-01

chl.erdc.usace.army.mil/sms). Cross-sections from a ERDC/CHL TR-09-17 7 HEC - RAS model provided by the district, along with aerial photographs for proper alignment...ER D C/ CH L TR -0 9 -1 7 Numerical Model Study of the Tuscarawas River below Dover Dam, Ohio Richard L. Stockstill and Jane M. Vaughan...September 2009 C oa st al a n d H yd ra u lic s La b or at or y Approved for public release; distribution is unlimited. ERDC/CHL TR-09

How Parents Read Counting Books and Non-numerical Books to Their Preverbal Infants: An Observational Study.

Science.gov (United States)

Goldstein, Alison; Cole, Thomas; Cordes, Sara

2016-01-01

Studies have stressed the importance of counting with children to promote formal numeracy abilities; however, little work has investigated when parents begin to engage in this behavior with their young children. In the current study, we investigated whether parents elaborated on numerical information when reading a counting book to their preverbal infants and whether developmental differences in numerical input exist even in the 1st year of life. Parents and their 5-10 months old infants were asked to read, as they would at home, two books to their infants: a counting book and another book that did not have numerical content. Parents' spontaneous statements rarely focused on number and those that did consisted primarily of counting, with little emphasis on labeling the cardinality of the set. However, developmental differences were observed even in this age range, such that parents were more likely to make numerical utterances when reading to older infants. Together, results are the first to characterize naturalistic reading behaviors between parents and their preverbal infants in the context of counting books, suggesting that although counting books promote numerical language in parents, infants still receive very little in the way of numerical input before the end of the 1st year of life. While little is known regarding the impact of number talk on the cognitive development of young infants, the current results may guide future work in this area by providing the first assessment of the characteristics of parental numerical input to preverbal infants.

Numerical analysis

CERN Document Server

Rao, G Shanker

2006-01-01

About the Book: This book provides an introduction to Numerical Analysis for the students of Mathematics and Engineering. The book is designed in accordance with the common core syllabus of Numerical Analysis of Universities of Andhra Pradesh and also the syllabus prescribed in most of the Indian Universities. Salient features: Approximate and Numerical Solutions of Algebraic and Transcendental Equation Interpolation of Functions Numerical Differentiation and Integration and Numerical Solution of Ordinary Differential Equations The last three chapters deal with Curve Fitting, Eigen Values and Eigen Vectors of a Matrix and Regression Analysis. Each chapter is supplemented with a number of worked-out examples as well as number of problems to be solved by the students. This would help in the better understanding of the subject. Contents: Errors Solution of Algebraic and Transcendental Equations Finite Differences Interpolation with Equal Intervals Interpolation with Unequal Int...

Experimental and numerical studies of turbulent flow in an in-line tube bundles

Directory of Open Access Journals (Sweden)

Aounalah Mohamed

2012-04-01

Full Text Available In the present paper an experimental and a numerical simulation of the turbulent flow in an in-line tube bundles have been performed. The experiments were carried out using a subsonic wind tunnel. The pressure distributions along the tubes (22 circumferential pressure taping were determined for a variation of the azimuthal angle from 0 to 360deg. The drag and lift forces are measured using the TE 44 balance. The Navier-Stokes equations of the turbulent flow are solved using Reynolds Stress and K-ε, turbulence models (RANS provided by Fluent CFD code. An adapted grid using static pressure, pressure coefficient and velocity gradient, furthermore, a second order upwind scheme were used. The obtained results from the experimental and numerical studies show a satisfactory agreement.

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 study of effect of oxygen fraction on local entropy ...

Indian Academy of Sciences (India)

This study considers numerical simulation of the combustion of methane with air, including oxygen and nitrogen, in a burner and the numerical solution of local entropy generation rate due to high temperature and velocity gradients in the combustion chamber. The effects of equivalence ratio () and oxygen percentage () ...

How Parents Read Counting Books and Non-Numerical Books to Their Preverbal Infants: An Observational Study

Directory of Open Access Journals (Sweden)

Alison Goldstein

2016-07-01

Full Text Available Studies have stressed the importance of counting with children to promote formal numeracy abilities; however little work has investigated when parents begin to engage in this behavior with their young children. In the current study, we investigated whether parents elaborated on numerical information when reading a counting book to their preverbal infants and whether developmental differences in numerical input exist even in the first year of life. Parents and their 5-10 month old infants were asked to read, as they would at home, two books to their infants: a counting book and another book that did not have numerical content. Parents’ spontaneous statements rarely focused on number and those that did consisted primarily of counting, with little emphasis on labeling the cardinality of the set. However, developmental differences were observed even in this age range, such that parents were more likely to make numerical utterances when reading to older infants. Together, results are the first to characterize naturalistic reading behaviors between parents and their preverbal infants in the context of counting books, suggesting that although counting books promote numerical language in parents, infants still receive very little in the way of numerical input before the end of the first year of life. While little is known regarding the impact of number talk on the cognitive development of young infants, the current results may guide future work in this area by providing the first assessment of the characteristics of parental numerical input to preverbal infants.

Numerical study of impact erosion of multiple solid particle

Science.gov (United States)

Zheng, Chao; Liu, Yonghong; Chen, Cheng; Qin, Jie; Ji, Renjie; Cai, Baoping

2017-11-01

Material erosion caused by continuous particle impingement during hydraulic fracturing results in significant economic loss and increased production risks. The erosion process is complex and has not been clearly explained through physical experiments. To address this problem, a multiple particle model in a 3D configuration was proposed to investigate the dynamic erosion process. This approach can significantly reduce experiment costs. The numerical model considered material damping and elastic-plastic material behavior of target material. The effects of impact parameters on erosion characteristics, such as plastic deformation, contact time, and energy loss rate, were investigated. Based on comprehensive studies, the dynamic erosion mechanism and geometry evolution of eroded crater was obtained. These findings can provide a detailed erosion process of target material and insights into the material erosion caused by multiple particle impingement.

The numerical study the rising of the explosion clouds in the uniform atmosphere

International Nuclear Information System (INIS)

Li Xiaoli; Zheng Yi; Chao Ying

2010-01-01

This paper is to study the rising of the explosion clouds in the uniform atmosphere, the numerical model is based on the assumption that effects the clouds are gravity and buoyancy. The model is testified by Rayleigh-Taylor unsteady problem. The evolution of the density and the velocity during the rising of the explosion clouds are provided, and the computational results are reasonable compared to the rising of the real nuclear explosion cloud. (authors)

Numerical Study of Planar GPR Antenna Measurements

DEFF Research Database (Denmark)

Meincke, Peter; Hansen, Thorkild

2004-01-01

The formulation of planar near-field measurements of GPR antennas determines the plane-wave spectra of the GPR antenna in terms of measurements obtained with a buried probe as the GPR antenna moves over a scan plane on the ground. A numerical study investigates how the formulation is affected by (1...

Numerical Study of Flow Motion and Patterns Driven by a Rotating Permanent Helical Magnetic Field

Science.gov (United States)

Yang, Wenzhi; Wang, Xiaodong; Wang, Bo; Baltaretu, Florin; Etay, Jacqueline; Fautrelle, Yves

2016-10-01

Liquid metal magnetohydrodynamic flow driven by a rotating permanent helical magnetic field in a cylindrical container is numerically studied. A three-dimensional numerical simulation provides insight into the visualization of the physical fields, including the magnetic field, the Lorentz force density, and the flow structures, especially the flow patterns in the meridional plane. Because the screen parameter is sufficiently small, the model is decoupled into electromagnetic and hydrodynamic components. Two flow patterns in the meridional plane, i.e., the global flow and the secondary flow, are discovered and the impact of several system parameters on their transition is investigated. Finally, a verifying model is used for comparison with the previous experiment.

Numerical and Experimental Study of Pump Sump Flows

Directory of Open Access Journals (Sweden)

Wei-Liang Chuang

2014-01-01

Full Text Available The present study analyzes pump sump flows with various discharges and gate submergence. Investigations using a three-dimensional large eddy simulation model and an acoustic Doppler velocimeter are performed. Flow patterns and velocity profiles in the approaching flow are shown to describe the flow features caused by various discharges and gate submergence. The variation of a large-scale spanwise vortex behind a sluice gate is examined and discussed. The suction effect on approaching flow near the pipe column is examined using numerical modeling. To gain more understanding of the vortices variation, a comparison between time-averaged and instantaneous flow patterns is numerically conducted. Additionally, swirl angle, a widely used index for evaluating pump efficiency, is experimentally and numerically examined under various flow conditions. The results indicate that the pump becomes less efficient with increasing discharge and gate submergence. The fluctuation of the free surface over the pump sump is also discussed.

Numerical studies of various Néel-VBS transitions in SU(N) anti-ferromagnets

International Nuclear Information System (INIS)

Kaul, Ribhu K; Block, Matthew S

2015-01-01

In this manuscript we review recent developments in the numerical simulations of bipartite SU(N) spin models by quantum Monte Carlo (QMC) methods. We provide an account of a large family of newly discovered sign-problem free spin models which can be simulated in their ground states on large lattices, containing O(10 5 ) spins, using the stochastic series expansion method with efficient loop algorithms. One of the most important applications so far of these Hamiltonians are to unbiased studies of quantum criticality between Neel and valence bond phases in two dimensions - a summary of this body of work is provided. The article concludes with an overview of the current status of and outlook for future studies of the “designer” Hamiltonians. (paper)

Numerical studies of various Néel-VBS transitions in SU(N) anti-ferromagnets

Science.gov (United States)

Kaul, Ribhu K.; Block, Matthew S.

2015-09-01

In this manuscript we review recent developments in the numerical simulations of bipartite SU(N) spin models by quantum Monte Carlo (QMC) methods. We provide an account of a large family of newly discovered sign-problem free spin models which can be simulated in their ground states on large lattices, containing O(105) spins, using the stochastic series expansion method with efficient loop algorithms. One of the most important applications so far of these Hamiltonians are to unbiased studies of quantum criticality between Neel and valence bond phases in two dimensions - a summary of this body of work is provided. The article concludes with an overview of the current status of and outlook for future studies of the “designer” Hamiltonians.

Numerical study of jets secondary instabilities

International Nuclear Information System (INIS)

Brancher, Pierre

1996-01-01

The work presented in this dissertation is a contribution to the study of the transition to turbulence in open shear flows. Results from direct numerical simulations are interpreted within the framework of hydrodynamic stability theory. The first chapter is an introduction to the primary and secondary instabilities observed in jets and mixing layers. The numerical method used in the present study is detailed in the second chapter. The dynamics of homogeneous circular jets subjected to stream wise and azimuthal perturbations are investigated in the third chapter. A complete scenario describing the evolution of the jet is proposed with emphasis on the dynamics of vorticity within the flow. In the fourth chapter a parametric study reveals a three-dimensional secondary instability mainly controlled in the linear regime by the Strouhal number of the primary instability. In the nonlinear regime the dynamics of the azimuthal harmonies are described by means of model equations and are linked to the formation of stream wise vortices in the braid. The fifth chapter is dedicated to the convective or absolute nature of the secondary instabilities in plane shear layers. It is shown that there are flow configurations for which the two-dimensional secondary instability (pairing) is absolute even though the primary instability (Kelvin-Helmholtz) is convective. Some preliminary results concerning the three-dimensional secondary instabilities arc presented at the end of this chapter. The last chapter summarizes the main results and examines possible extensions of this work. (author) [fr

Experimental and Numerical Study of FRP Encased Composite Concrete Columns

Directory of Open Access Journals (Sweden)

Mohsen Ishaghian

2017-02-01

Full Text Available A new type of composite column is presented and assessed through experimental testing and numerical modeling. The objective of this research is to investigate design options for a composite column without the use of ferrous materials. This is to avoid the current problem of deterioration of concrete due to expansion of rusting reinforcement members. Such a target can be achieved by replacing the steel reinforcement of concrete columns with pultruded I-shape glass FRP structural sections. The composite column utilizes a glass FRP tube that surrounds a pultruded I-section glass FRP, which is subsequently filled with concrete. The GFRP tube acts as a stay-in-place form in addition to providing confinement to the concrete. A total of four composite columns were tested under monotonic axial loading. The experimental ultimate capacity of each of the tested composite column was compared to the predicted numerical capacity using ANSYS program. The comparison showed that the predicted numerical values were in good agreement with the experimental ones.

Numerical study of a hybrid jet impingement/micro-channel cooling scheme

International Nuclear Information System (INIS)

Barrau, Jérôme; Omri, Mohammed; Chemisana, Daniel; Rosell, Joan; Ibañez, Manel; Tadrist, Lounes

2012-01-01

A new hybrid jet impingement/micro-channel cooling scheme is studied numerically for use in high-heat-flux thermal management of electronic and power devices. The device is developed with the objective of improving the temperature uniformity of the cooled object. A numerical model based on the k–ω SST turbulent model is developed and validated experimentally. This model is used to carry out a parametrical characterization of the heat sink. The study shows that variations in key parameters of jet impingement and micro-channel technologies allow for the cooling scheme to obtain a wide range of temperature profiles for the cooled object. - Highlights: ► A new hybrid cooling scheme is numerically studied. ► The cooling scheme combines the benefits of jet impingement and micro-channel flows. ► The numerical model is validated by comparison with experimental results. ► The temperature distribution can be adapted to the needs of the cooled system.

Numerical Simulations of Kinetic Alfvén Waves to Study Spectral ...

Indian Academy of Sciences (India)

Numerical Simulations of Kinetic Alfvén Waves to Study Spectral. Index in Solar Wind Turbulence and Particle Heating. R. P. Sharma. ∗. & H. D. Singh. Center for Energy Studies, Indian Institute of Technology, Delhi 110 016, India. ∗ e-mail: rpsharma@ces.iitd.ernet.in. Abstract. We present numerical simulations of the ...

Analytical and numerical studies of creation probabilities of hierarchical trees

Directory of Open Access Journals (Sweden)

S.S. Borysov

2011-03-01

Full Text Available We consider the creation conditions of diverse hierarchical trees both analytically and numerically. A connection between the probabilities to create hierarchical levels and the probability to associate these levels into a united structure is studied. We argue that a consistent probabilistic picture requires the use of deformed algebra. Our consideration is based on the study of the main types of hierarchical trees, among which both regular and degenerate ones are studied analytically, while the creation probabilities of Fibonacci, scale-free and arbitrary trees are determined numerically.

Numerical study of nonspherical black hole accretion

International Nuclear Information System (INIS)

Hawley, J.F.

1984-01-01

This thesis describes in detail a two-dimensional, axisymmetric computer code for calculating fully relativistic ideal gas hydrodynamics around a Kerr black hole. The aim is to study fully dynamic inviscid fluid accretion onto black holes, as well as to study the evolution and development of nonlinear instabilities in pressure supported accretion disks. In order to fully calibrate and document the code, certain analytic solutions for shock tubes and special accretion flows are derived; these solutions form the basis for code testing. The numerical techniques used are developed and discussed. A variety of alternate differencing schemes are compared on an analytic test bed. Some discussion is devoted to general issues in finite differencing. The working code is calibrated using analytically solvable accretion problems, including the radial accretion of dust and of fluid with pressure (Bondi accretion). Two dimensional test problems include the spiraling infall of low angular momentum fluid, the formation of a pressure supported torus, and the stable evolution of a torus. A series of numerical models are discussed and illustrated with selected plots

Numerical study of thermal test of a cask of transportation for radioactive material

International Nuclear Information System (INIS)

Vieira, Tiago A.S.; Santos, André A.C. dos; Vidal, Guilherme A.M.; Silva Junior, Geraldo E.

2017-01-01

In this study numerical simulations of a transport cask for radioactive material were made and the numerical results were compared with experimental results of tests carried out in two different opportunities. A mesh study was also made regarding the previously designed geometry of the same cask, in order to evaluate its impact in relation to the stability of numerical results for this type of problem. The comparison of the numerical and experimental results allowed to evaluate the need to plan and carry out a new test in order to validate the CFD codes used in the numerical simulations

Study on the groundwater sustainable problem by numerical ...

Indian Academy of Sciences (India)

Pengpeng Zhou

2017-10-07

Oct 7, 2017 ... system in Zhanjiang, China, this paper presents a numerical modelling study to research groundwater sustainability of ... bility is a feasible method for solving the sus- ...... Singh A 2010 Decision support for on-farm water man-.

Numerical Algorithm for Delta of Asian Option

Directory of Open Access Journals (Sweden)

Boxiang Zhang

2015-01-01

Full Text Available We study the numerical solution of the Greeks of Asian options. In particular, we derive a close form solution of Δ of Asian geometric option and use this analytical form as a control to numerically calculate Δ of Asian arithmetic option, which is known to have no explicit close form solution. We implement our proposed numerical method and compare the standard error with other classical variance reduction methods. Our method provides an efficient solution to the hedging strategy with Asian options.

A study on user authentication methodology using numeric password and fingerprint biometric information.

Science.gov (United States)

Ju, Seung-hwan; Seo, Hee-suk; Han, Sung-hyu; Ryou, Jae-cheol; Kwak, Jin

2013-01-01

The prevalence of computers and the development of the Internet made us able to easily access information. As people are concerned about user information security, the interest of the user authentication method is growing. The most common computer authentication method is the use of alphanumerical usernames and passwords. The password authentication systems currently used are easy, but only if you know the password, as the user authentication is vulnerable. User authentication using fingerprints, only the user with the information that is specific to the authentication security is strong. But there are disadvantage such as the user cannot change the authentication key. In this study, we proposed authentication methodology that combines numeric-based password and biometric-based fingerprint authentication system. Use the information in the user's fingerprint, authentication keys to obtain security. Also, using numeric-based password can to easily change the password; the authentication keys were designed to provide flexibility.

Numerical study on discharge process of microcavity plasma

International Nuclear Information System (INIS)

Xia Guangqing; Xue Weihua; Wang Dongxue; Zhu Guoqiang; Zhu Yu

2012-01-01

The evolution of plasma parameters during high pressure discharge in the microcavity with a hollow anode was numerically studied, with a two-dimensional self-consistent fluid model. The simulations were performed with argon at 13.3 kPa. The numerical results show that during the discharge the electric field around the cathode transforms from an axial field to a radial field, the plasma density gets the maximum value on the central line of the cavity and the location of the maximum density moves from the region near anode at the initial stage to the cathode vicinity at the stable stage, and the maximum electron temperature occurs in the ring sheath of cathode. (authors)

Numerical study of time domain analogy applied to noise prediction from rotating blades

Science.gov (United States)

Fedala, D.; Kouidri, S.; Rey, R.

2009-04-01

Aeroacoustic formulations in time domain are frequently used to model the aerodynamic sound of airfoils, the time data being more accessible. The formulation 1A developed by Farassat, an integral solution of the Ffowcs Williams and Hawkings equation, holds great interest because of its ability to handle surfaces in arbitrary motion. The aim of this work is to study the numerical sensitivity of this model to specified parameters used in the calculation. The numerical algorithms, spatial and time discretizations, and approximations used for far-field acoustic simulation are presented. An approach of quantifying of the numerical errors resulting from implementation of formulation 1A is carried out based on Isom's and Tam's test cases. A helicopter blade airfoil, as defined by Farassat to investigate Isom's case, is used in this work. According to Isom, the acoustic response of a dipole source with a constant aerodynamic load, ρ0c02, is equal to the thickness noise contribution. Discrepancies are observed when the two contributions are computed numerically. In this work, variations of these errors, which depend on the temporal resolution, Mach number, source-observer distance, and interpolation algorithm type, are investigated. The results show that the spline interpolating algorithm gives the minimum error. The analysis is then extended to Tam's test case. Tam's test case has the advantage of providing an analytical solution for the first harmonic of the noise produced by a specific force distribution.

Numerical Study on Critical Wedge Angle of Cellular Detonation Reflections

International Nuclear Information System (INIS)

Gang, Wang; Kai-Xin, Liu; De-Liang, Zhang

2010-01-01

The critical wedge angle (CWA) for the transition from regular reflection (RR) to Mach reflection (MR) of a cellular detonation wave is studied numerically by an improved space-time conservation element and solution element method together with a two-step chemical reaction model. The accuracy of that numerical way is verified by simulating cellular detonation reflections at a 19.3° wedge. The planar and cellular detonation reflections over 45°–55° wedges are also simulated. When the cellular detonation wave is over a 50° wedge, numerical results show a new phenomenon that RR and MR occur alternately. The transition process between RR and MR is investigated with the local pressure contours. Numerical analysis shows that the cellular structure is the essential reason for the new phenomenon and the CWA of detonation reflection is not a certain angle but an angle range. (fundamental areas of phenomenology(including applications))

Numerical study of read scheme in one-selector one-resistor crossbar array

Science.gov (United States)

Kim, Sungho; Kim, Hee-Dong; Choi, Sung-Jin

2015-12-01

A comprehensive numerical circuit analysis of read schemes of a one selector-one resistance change memory (1S1R) crossbar array is carried out. Three schemes-the ground, V/2, and V/3 schemes-are compared with each other in terms of sensing margin and power consumption. Without the aid of a complex analytical approach or SPICE-based simulation, a simple numerical iteration method is developed to simulate entire current flows and node voltages within a crossbar array. Understanding such phenomena is essential in successfully evaluating the electrical specifications of selectors for suppressing intrinsic drawbacks of crossbar arrays, such as sneaky current paths and series line resistance problems. This method provides a quantitative tool for the accurate analysis of crossbar arrays and provides guidelines for developing an optimal read scheme, array configuration, and selector device specifications.

Numerical study of MHD supersonic flow control

Science.gov (United States)

Ryakhovskiy, A. I.; Schmidt, A. A.

2017-11-01

Supersonic MHD flow around a blunted body with a constant external magnetic field has been simulated for a number of geometries as well as a range of the flow parameters. Solvers based on Balbas-Tadmor MHD schemes and HLLC-Roe Godunov-type method have been developed within the OpenFOAM framework. The stability of the solution varies depending on the intensity of magnetic interaction The obtained solutions show the potential of MHD flow control and provide insights into for the development of the flow control system. The analysis of the results proves the applicability of numerical schemes, that are being used in the solvers. A number of ways to improve both the mathematical model of the process and the developed solvers are proposed.

Numerical studies on divertor experiments

International Nuclear Information System (INIS)

Ueda, N.; Itoh, K.; Itoh, S.-I.; Tanaka, M.; Hasegawa, M.; Shoji, T.; Sugihara, M.

1988-04-01

Numerical analysis on the divertor experiments such as JFT-2M tokamak is made by use of the two-dimensional time-dependent simulation code. The plasma in the scrape-off layer (SOL) and divertor region is solved for the given particle and heat sources from the main plasma, Γ p and Q T . Effect of the direction of the toroidal magnetic field is studied. It is found that the heat flux which is proportional to b vector x ∇T i has influences on the divertor plasmas, but has a small effect on the parameters on the midplane in the framework of the fluid model. Parameter survey on Γ p and Q T is made. The transient response of the SOL/divertor plasma to the sudden change of Γ p and Q T is studied. Time delay in the SOL and divertor region is calculated. (author)

Numerical and experimental studies of droplet-gas flow

Energy Technology Data Exchange (ETDEWEB)

Joesang, Aage Ingebret

2002-07-01

This thesis considers droplet-gas flow by the use of numerical methods and experimental verification. A commercial vane separator was studied both numerical and by experiment. In addition some efforts are put into the numerical analysis of cyclones. The experimental part contains detailed measurements of the flow field between a pair of vanes in a vane separator and droplet size measurements. LDA (Laser Doppler Anemometry) was used to measure the velocity in two dimensions and corresponding turbulence quantities. The results from the LDA measurements are considered to be of high quality and are compared to numerical results obtained from a CFD (Computational Fluid Dynamics) analysis. The simulation showed good agreement between the numerical and experimental results. Combinations of different turbulence models; the standard k-epsilon model and the Reynold Stress Mode, different schemes; first order and higher order scheme and different near wall treatment of the turbulence; the Law of the wall and the Two-Layer Zonal model were used in the simulations. The Reynold Stress Model together with a higher order scheme performed rather poorly. The recirculation in parts of the separator was overpredicted in this case. For the other cases the overall predictions are satisfactory. PDA (Phase Doppler Anemometry) measurements were used to study the changes in the droplet size distribution through the vane separator. The PDA measurements show that smaller droplets are found at the outlet than present at the inlet. In the literature there exists different mechanisms for explaining the re-entrainment and generation of new droplets. The re-entrainments mechanisms are divided into four groups where droplet-droplet interaction, droplet break-up, splashing of impinging droplet and re-entrainment from the film are defined as the groups of re-entrainment mechanisms. Models for these groups are found in the literature and these models are tested for re-entrainment using the operational

Numerical distance protection

CERN Document Server

Ziegler, Gerhard

2011-01-01

Distance protection provides the basis for network protection in transmission systems and meshed distribution systems. This book covers the fundamentals of distance protection and the special features of numerical technology. The emphasis is placed on the application of numerical distance relays in distribution and transmission systems.This book is aimed at students and engineers who wish to familiarise themselves with the subject of power system protection, as well as the experienced user, entering the area of numerical distance protection. Furthermore it serves as a reference guide for s

The Adriatic response to the bora forcing. A numerical study

International Nuclear Information System (INIS)

Rachev, N.

2001-01-01

This paper deals with the bora wind effect on the Adriatic Sea circulation as simulated by a 3-D numerical code (the DieCAST model). The main result of this forcing is the formation of intense upwelling along the eastern coast in agreement with previous theoretical studies and observations. Different numerical experiments are discussed for various boundary and initial conditions to evaluate their influence on both circulation and upwelling patterns

Numerical study on the selective excitation of Helmholtz-Gauss beams in end-pumped solid-state digital lasers with the control of the laser gain transverse position provided by off-axis end pumping

Science.gov (United States)

Tsai, Ko-Fan; Chu, Shu-Chun

2018-03-01

This study proposes a complete and unified method for selective excitation of any specified nearly nondiffracting Helmholtz-Gauss (HzG) beam in end-pumped solid-state digital lasers. Four types of the HzG beams: cosine-Gauss beams, Bessel-Gauss beams, Mathieu-Gauss beams, and, in particular, parabolic-Gauss beams are successfully demonstrated to be generated with the proposed methods. To the best of the authors’ knowledge, parabolic-Gauss beams have not yet been directly generated from any kind of laser system. The numerical results of this study show that one can successfully achieve any lasing HzG beams directly from the solid-state digital lasers with only added control of the laser gain transverse position provided by off-axis end pumping. This study also presents a practical digital laser set-up for easily manipulating off-axis pumping in order to achieve the control of the laser gain transverse gain position in digital lasers. The reported results in this study provide advancement of digital lasers in dynamically generating nondiffracting beams. The control of the digital laser cavity gain position creates the possibility of achieving real-time selection of more laser modes in digital lasers, and it is worth further investigation in the future.

Experimental and numerical study of an autonomous flap

NARCIS (Netherlands)

Bernhammer, L.O.; Navalkar, S.T.; Sodja, J.; De Breuker, R.; Karpel, M.

2015-01-01

This paper presents the experimental and numerical study of an autonomous load alleviation concept using trailing edge flaps. The flaps are autonomous units, which for instance can be used for gust load alleviation. The unit is self-powered and self-actuated through trailing edge tabs which are

A Study on User Authentication Methodology Using Numeric Password and Fingerprint Biometric Information

Directory of Open Access Journals (Sweden)

Seung-hwan Ju

2013-01-01

Full Text Available The prevalence of computers and the development of the Internet made us able to easily access information. As people are concerned about user information security, the interest of the user authentication method is growing. The most common computer authentication method is the use of alphanumerical usernames and passwords. The password authentication systems currently used are easy, but only if you know the password, as the user authentication is vulnerable. User authentication using fingerprints, only the user with the information that is specific to the authentication security is strong. But there are disadvantage such as the user cannot change the authentication key. In this study, we proposed authentication methodology that combines numeric-based password and biometric-based fingerprint authentication system. Use the information in the user's fingerprint, authentication keys to obtain security. Also, using numeric-based password can to easily change the password; the authentication keys were designed to provide flexibility.

A Study on User Authentication Methodology Using Numeric Password and Fingerprint Biometric Information

Science.gov (United States)

Ju, Seung-hwan; Seo, Hee-suk; Han, Sung-hyu; Ryou, Jae-cheol

2013-01-01

The prevalence of computers and the development of the Internet made us able to easily access information. As people are concerned about user information security, the interest of the user authentication method is growing. The most common computer authentication method is the use of alphanumerical usernames and passwords. The password authentication systems currently used are easy, but only if you know the password, as the user authentication is vulnerable. User authentication using fingerprints, only the user with the information that is specific to the authentication security is strong. But there are disadvantage such as the user cannot change the authentication key. In this study, we proposed authentication methodology that combines numeric-based password and biometric-based fingerprint authentication system. Use the information in the user's fingerprint, authentication keys to obtain security. Also, using numeric-based password can to easily change the password; the authentication keys were designed to provide flexibility. PMID:24151601

Biofouling in forward osmosis systems: An experimental and numerical study.

Science.gov (United States)

Bucs, Szilárd S; Valladares Linares, Rodrigo; Vrouwenvelder, Johannes S; Picioreanu, Cristian

2016-12-01

This study evaluates with numerical simulations supported by experimental data the impact of biofouling on membrane performance in a cross-flow forward osmosis (FO) system. The two-dimensional numerical model couples liquid flow with solute transport in the FO feed and draw channels, in the FO membrane support layer and in the biofilm developed on one or both sides of the membrane. The developed model was tested against experimental measurements at various osmotic pressure differences and in batch operation without and with the presence of biofilm on the membrane active layer. Numerical studies explored the effect of biofilm properties (thickness, hydraulic permeability and porosity), biofilm membrane surface coverage, and biofilm location on salt external concentration polarization and on the permeation flux. The numerical simulations revealed that (i) when biofouling occurs, external concentration polarization became important, (ii) the biofilm hydraulic permeability and membrane surface coverage have the highest impact on water flux, and (iii) the biofilm formed in the draw channel impacts the process performance more than when formed in the feed channel. The proposed mathematical model helps to understand the impact of biofouling in FO membrane systems and to develop possible strategies to reduce and control biofouling. Copyright © 2016 Elsevier Ltd. All rights reserved.

Biofouling in forward osmosis systems: An experimental and numerical study

KAUST Repository

Bucs, Szilard

2016-09-20

This study evaluates with numerical simulations supported by experimental data the impact of biofouling on membrane performance in a cross-flow forward osmosis (FO) system. The two-dimensional numerical model couples liquid flow with solute transport in the FO feed and draw channels, in the FO membrane support layer and in the biofilm developed on one or both sides of the membrane. The developed model was tested against experimental measurements at various osmotic pressure differences and in batch operation without and with the presence of biofilm on the membrane active layer. Numerical studies explored the effect of biofilm properties (thickness, hydraulic permeability and porosity), biofilm membrane surface coverage, and biofilm location on salt external concentration polarization and on the permeation flux. The numerical simulations revealed that (i) when biofouling occurs, external concentration polarization became important, (ii) the biofilm hydraulic permeability and membrane surface coverage have the highest impact on water flux, and (iii) the biofilm formed in the draw channel impacts the process performance more than when formed in the feed channel. The proposed mathematical model helps to understand the impact of biofouling in FO membrane systems and to develop possible strategies to reduce and control biofouling. © 2016 Elsevier Ltd

Analytical and Numerical Studies of Sloshing in Tanks

Energy Technology Data Exchange (ETDEWEB)

Solaas, F

1996-12-31

For oil cargo ship tanks and liquid natural gas carriers, the dimensions of the tanks are often such that the highest resonant sloshing periods and the ship motions are in the same period range, which may cause violent resonant sloshing of the liquid. In this doctoral thesis, linear and non-linear analytical potential theory solutions of the sloshing problem are studied for a two-dimensional rectangular tank and a vertical circular cylindrical tank, using perturbation technique for the non-linear case. The tank is forced to oscillate harmonically with small amplitudes of sway with frequency in the vicinity of the lowest natural frequency of the fluid inside the tank. The method is extended to other tank shapes using a combined analytical and numerical method. A boundary element numerical method is used to determine the eigenfunctions and eigenvalues of the problem. These are used in the non-linear analytical free surface conditions, and the velocity potential and free surface elevation for each boundary value problem in the perturbation scheme are determined by the boundary element method. Both the analytical method and the combined analytical and numerical method are restricted to tanks with vertical walls in the free surface. The suitability of a commercial programme, FLOW-3D, to estimate sloshing is studied. It solves the Navier-Stokes equations by the finite difference method. The free surface as function of time is traced using the fractional volume of fluid method. 59 refs., 54 figs., 37 tabs.

Analytical and Numerical Studies of Sloshing in Tanks

Energy Technology Data Exchange (ETDEWEB)

Solaas, F.

1995-12-31

For oil cargo ship tanks and liquid natural gas carriers, the dimensions of the tanks are often such that the highest resonant sloshing periods and the ship motions are in the same period range, which may cause violent resonant sloshing of the liquid. In this doctoral thesis, linear and non-linear analytical potential theory solutions of the sloshing problem are studied for a two-dimensional rectangular tank and a vertical circular cylindrical tank, using perturbation technique for the non-linear case. The tank is forced to oscillate harmonically with small amplitudes of sway with frequency in the vicinity of the lowest natural frequency of the fluid inside the tank. The method is extended to other tank shapes using a combined analytical and numerical method. A boundary element numerical method is used to determine the eigenfunctions and eigenvalues of the problem. These are used in the non-linear analytical free surface conditions, and the velocity potential and free surface elevation for each boundary value problem in the perturbation scheme are determined by the boundary element method. Both the analytical method and the combined analytical and numerical method are restricted to tanks with vertical walls in the free surface. The suitability of a commercial programme, FLOW-3D, to estimate sloshing is studied. It solves the Navier-Stokes equations by the finite difference method. The free surface as function of time is traced using the fractional volume of fluid method. 59 refs., 54 figs., 37 tabs.

Current status of regional hydrogeological studies and numerical simulations on geological disposal

International Nuclear Information System (INIS)

Nakao, Shinsuke; Kikuchi, Tsuneo; Ishido, Tsuneo

2004-01-01

Current status of regional hydrogeological studies on geological disposal including hydrogeological modeling using numerical simulators is reviewed in this report. A regional scale and boundary conditions of numerical models are summarized mainly from the results of the RHS (regional hydrogeological study) project conducted by Japan Nuclear Cycle Development Institute (JNC) in the Tono area. We also refer to the current conceptual modes of hydrology and numerical models of unsaturated zone flow at Yucca Mountain, Nevada, which is the arid site proposed for consideration as the United States' first underground high-level radioactive waste repository. Understanding behavior of a freshwater-saltwater transition zone seems to play a key role in the hydrogeological modeling in a coastal region. Technical features of a numerical simulator as a tool for geothermal reservoir modeling is also briefly described. (author)

Foundations of children's numerical and mathematical skills: the roles of symbolic and nonsymbolic representations of numerical magnitude.

Science.gov (United States)

Lyons, Ian M; Ansari, Daniel

2015-01-01

Numerical and mathematical skills are critical predictors of academic success. The last three decades have seen a substantial growth in our understanding of how the human mind and brain represent and process numbers. In particular, research has shown that we share with animals the ability to represent numerical magnitude (the total number of items in a set) and that preverbal infants can process numerical magnitude. Further research has shown that similar processing signatures characterize numerical magnitude processing across species and developmental time. These findings suggest that an approximate system for nonsymbolic (e.g., dot arrays) numerical magnitude representation serves as the basis for the acquisition of cultural, symbolic (e.g., Arabic numerals) representations of numerical magnitude. This chapter explores this hypothesis by reviewing studies that have examined the relation between individual differences in nonsymbolic numerical magnitude processing and symbolic math abilities (e.g., arithmetic). Furthermore, we examine the extent to which the available literature provides strong evidence for a link between symbolic and nonsymbolic representations of numerical magnitude at the behavioral and neural levels of analysis. We conclude that claims that symbolic number abilities are grounded in the approximate system for the nonsymbolic representation of numerical magnitude are not strongly supported by the available evidence. Alternative models and future research directions are discussed. © 2015 Elsevier Inc. All rights reserved.

On the Numerical and Experimental Study of Spray Cooling

Directory of Open Access Journals (Sweden)

M.R. Guechi

2013-12-01

Full Text Available The spraying of an impinging jet is an effective way to cool heated surfaces. The objective of this study is to develop a numerical model to predict the heat transfer with phase change between a hot plate surface and a two-phase impinging jet. Different two-phase modeling approaches (Lagrangian and Eulerian methods are compared. The influence of the spray nozzle operating conditions and of the distance between the nozzle exit and the surface impact is analyzed. The numerical results are compared with measurements obtained on an experimental test bench. The confrontation numerical/experimental is carried out by comparing the distribution of temperature at the surface of the plate and the heat transfer coefficient. This comparison shows that it is the Eulerian model which seems most capable to take into account the evaporation of the droplets in contact with the heated plate. However, the simulation performed with this model show a strong dependence of the results to the turbulence model used.

Interdisciplinary Study of Numerical Methods and Power Plants Engineering

Directory of Open Access Journals (Sweden)

Ioana OPRIS

2014-08-01

Full Text Available The development of technology, electronics and computing opened the way for a cross-disciplinary research that brings benefits by combining the achievements of different fields. To prepare the students for their future interdisciplinary approach,aninterdisciplinary teaching is adopted. This ensures their progress in knowledge, understanding and ability to navigate through different fields. Aiming these results, the Universities introduce new interdisciplinary courses which explore complex problems by studying subjects from different domains. The paper presents a problem encountered in designingpower plants. The method of solvingthe problem isused to explain the numerical methods and to exercise programming.The goal of understanding a numerical algorithm that solves a linear system of equations is achieved by using the knowledge of heat transfer to design the regenerative circuit of a thermal power plant. In this way, the outcomes from the prior courses (mathematics and physics are used to explain a new subject (numerical methods and to advance future ones (power plants.

Two systems of non-symbolic numerical cognition

Directory of Open Access Journals (Sweden)

Daniel C. Hyde

2011-11-01

Full Text Available Studies of human adults, infants, and non-human animals demonstrate that non-symbolic numerical cognition is supported by at least two distinct cognitive systems: a ‘parallel individuation system’ that encodes the numerical identity of individual items and an ‘approximate number system’ that encodes the approximate numerical magnitude, or numerosity, of a set. The exact nature of these systems, however, have been debated for over a hundred years. Some argue that the non-symbolic representation of small numbers (< 4 is carried out solely by the parallel individuation system and the non-symbolic representation of large numbers (> 4 is carried out solely by the approximate number system. Others argue that all numbers are represented by the approximate number system. This debate has been fueled largely by some studies showing dissociations in processing and other studies showing similar processing of small and large numbers. Recent work has addressed this debate by showing that the two systems are present and distinct from early infancy, persist despite the acquisition of a symbolic number system, activate distinct cortical networks, and engage differentially based attentional constraints. Based on the recent discoveries, I provide a hypothesis that may explain the puzzling findings and makes testable predictions as to when each system will be engaged. In particular, when items are presented under conditions that allow selection of individuals, they will be represented as distinct mental items through parallel individuation and not as a numerical magnitude. In contrast, when items are presented outside attentional limits (e.g. too many, too close together, under high attentional load, they will be represented as a single mental numerical magnitude and not as distinct mental items. These predictions provide a basis on which researchers can further investigate the role of each system in the development of uniquely human numerical thought.

Precarious Rock Methodology for Seismic Hazard: Physical Testing, Numerical Modeling and Coherence Studies

Energy Technology Data Exchange (ETDEWEB)

Anooshehpoor, Rasool; Purvance, Matthew D.; Brune, James N.; Preston, Leiph A.; Anderson, John G.; Smith, Kenneth D.

2006-09-29

This report covers the following projects: Shake table tests of precarious rock methodology, field tests of precarious rocks at Yucca Mountain and comparison of the results with PSHA predictions, study of the coherence of the wave field in the ESF, and a limited survey of precarious rocks south of the proposed repository footprint. A series of shake table experiments have been carried out at the University of Nevada, Reno Large Scale Structures Laboratory. The bulk of the experiments involved scaling acceleration time histories (uniaxial forcing) from 0.1g to the point where the objects on the shake table overturned a specified number of times. The results of these experiments have been compared with numerical overturning predictions. Numerical predictions for toppling of large objects with simple contact conditions (e.g., I-beams with sharp basal edges) agree well with shake-table results. The numerical model slightly underpredicts the overturning of small rectangular blocks. It overpredicts the overturning PGA for asymmetric granite boulders with complex basal contact conditions. In general the results confirm the approximate predictions of previous studies. Field testing of several rocks at Yucca Mountain has approximately confirmed the preliminary results from previous studies, suggesting that he PSHA predictions are too high, possibly because the uncertainty in the mean of the attenuation relations. Study of the coherence of wavefields in the ESF has provided results which will be very important in design of the canisters distribution, in particular a preliminary estimate of the wavelengths at which the wavefields become incoherent. No evidence was found for extreme focusing by lens-like inhomogeneities. A limited survey for precarious rocks confirmed that they extend south of the repository, and one of these has been field tested.

Cognitive Strategy Use and Measured Numeric Ability in Immediate- and Long-Term Recall of Everyday Numeric Information

Science.gov (United States)

Bermingham, Douglas; Hill, Robert D.; Woltz, Dan; Gardner, Michael K.

2013-01-01

The goals of this study were to assess the primary effects of the use of cognitive strategy and a combined measure of numeric ability on recall of every-day numeric information (i.e. prices). Additionally, numeric ability was assessed as a moderator in the relationship between strategy use and memory for prices. One hundred participants memorized twelve prices that varied from 1 to 6 digits; they recalled these immediately and after 7 days. The use of strategies, assessed through self-report, was associated with better overall recall, but not forgetting. Numeric ability was not associated with either better overall recall or forgetting. A small moderating interaction was found, in which higher levels of numeric ability enhanced the beneficial effects of strategy use on overall recall. Exploratory analyses found two further small moderating interactions: simple strategy use enhanced overall recall at higher levels of numeric ability, compared to complex strategy use; and complex strategy use was associated with lower levels of forgetting, but only at higher levels of numeric ability, compared to the simple strategy use. These results provide support for an objective measure of numeric ability, as well as adding to the literature on memory and the benefits of cognitive strategy use. PMID:23483964

The Use of Numerical Applications in the Study of Dental Contacts

Directory of Open Access Journals (Sweden)

Rodica LUCA

2010-06-01

Full Text Available This paper seeks to explore the numerical analysis methods used in dentistry in general and those regarding teeth contacts, in particular. Typically, such an analysis consists of the following steps: modelling the actual object, mesh generation, numerical modelling and computer programming. The best known and mostly used of all is the finite element method. The paper also presents other more refined methods, for instance: CATIA and fast Fourier transform. The study of the living tissue based on numerical analysis exceeds the limitations of in vivo experiments but computers can never replicate the body adaptation capacity.

Numerical magnitude processing in abacus-trained children with superior mathematical ability: an EEG study.

Science.gov (United States)

Huang, Jian; Du, Feng-lei; Yao, Yuan; Wan, Qun; Wang, Xiao-Song; Chen, Fei-Yan

2015-08-01

Distance effect has been regarded as the best established marker of basic numerical magnitude processes and is related to individual mathematical abilities. A larger behavioral distance effect is suggested to be concomitant with lower mathematical achievement in children. However, the relationship between distance effect and superior mathematical abilities is unclear. One could get superior mathematical abilities by acquiring the skill of abacus-based mental calculation (AMC), which can be used to solve calculation problems with exceptional speed and high accuracy. In the current study, we explore the relationship between distance effect and superior mathematical abilities by examining whether and how the AMC training modifies numerical magnitude processing. Thus, mathematical competencies were tested in 18 abacus-trained children (who accepted the AMC training) and 18 non-trained children. Electroencephalography (EEG) waveforms were recorded when these children executed numerical comparison tasks in both Arabic digit and dot array forms. We found that: (a) the abacus-trained group had superior mathematical abilities than their peers; (b) distance effects were found both in behavioral results and on EEG waveforms; (c) the distance effect size of the average amplitude on the late negative-going component was different between groups in the digit task, with a larger effect size for abacus-trained children; (d) both the behavioral and EEG distance effects were modulated by the notation. These results revealed that the neural substrates of magnitude processing were modified by AMC training, and suggested that the mechanism of the representation of numerical magnitude for children with superior mathematical abilities was different from their peers. In addition, the results provide evidence for a view of non-abstract numerical representation.

Numerical Simulation and Experimental Study of Deep Bed Corn Drying Based on Water Potential

Directory of Open Access Journals (Sweden)

Zhe Liu

2015-01-01

Full Text Available The concept and the model of water potential, which were widely used in agricultural field, have been proved to be beneficial in the application of vacuum drying model and have provided a new way to explore the grain drying model since being introduced to grain drying and storage fields. Aiming to overcome the shortcomings of traditional deep bed drying model, for instance, the application range of this method is narrow and such method does not apply to systems of which pressure would be an influential factor such as vacuum drying system in a way combining with water potential drying model. This study established a numerical simulation system of deep bed corn drying process which has been proved to be effective according to the results of numerical simulation and corresponding experimental investigation and has revealed that desorption and adsorption coexist in deep bed drying.

Comparative Study of Algorithms for the Numerical Simulation of Lattice QCD

International Nuclear Information System (INIS)

Luz, Fernando H. P.; Mendes, Tereza

2010-01-01

Large-scale numerical simulations are the prime method for a nonperturbative study of QCD from first principles. Although the lattice simulation of the pure-gauge (or quenched-QCD) case may be performed very efficiently on parallel machines, there are several additional difficulties in the simulation of the full-QCD case, i.e. when dynamical quark effects are taken into account. We discuss the main aspects of full-QCD simulations, describing the most common algorithms. We present a comparative analysis of performance for two versions of the hybrid Monte Carlo method (the so-called R and RHMC algorithms), as provided in the MILC software package. We consider two degenerate flavors of light quarks in the staggered formulation, having in mind the case of finite-temperature QCD.

Experimental and numerical study of guided wave propagation in a thin metamaterial plate

International Nuclear Information System (INIS)

Zhu, R.; Huang, G.L.; Huang, H.H.; Sun, C.T.

2011-01-01

In this Letter, both in-plane and out-of-plane guided waves in a thin plate with local resonators are studied numerically and experimentally. Through the numerical simulation, a new metamaterial plate design is achieved for a low-frequency bandgap in both in-plane and out-of-plane guided waves. Experiments were conducted to validate the numerical design. In the experiment, piezoelectric transducers were used to generate and receive guided wave signals. The results show that the numerical predictions are in very good agreement with the experimental measurements. Specifically, the connection between the local resonance in the thin plate and its wave attenuation mechanism was discussed. -- Highlights: → Both in-plane and out-of-plane guided waves in a thin plate with local resonators are studied numerically and experimentally. → A new metamaterial plate design is achieved for a low-frequency bandgap in both in-plane and out-of-plane guided waves. → Experiments were conducted to validate the numerical design. → The connection between the local resonance in the thin plate and its wave attenuation mechanism was investigated.

Numerical study of turbulent diffusion

International Nuclear Information System (INIS)

McCoy, M.G.

1975-01-01

The problem of the numerical simulation of turbulent diffusion is studied. The two-dimensional velocity fields are assumed to be incompressible, homogeneous and stationary, and they are represented as stochastic processes. A technique is offered which creates velocity fields accurately representing the input statistics once a two point correlation function or an energy spectrum is given. Various complicated energy spectra may be represented utilizing this model. The program is then used to extract information concerning Gaussian diffusion processes. Various theories of other workers are tested including Taylor's classical representation of dispersion for times long compared with the Lagrangian correlation time. Also, a study is made of the relation between the Lagrangian and the Eulerian correlation function and a hypothesis is advanced and successfully tested. Questions concerning the relation between small eddies and the energy spectrum are considered. A criterion is advanced and successfully tested to decide whether small scale flow can be detected within the large eddies for any given spectrum. A method is developed to determine whether this small scale motion is in any sense periodic. Finally, the relation between two particle dispersion and the energy spectrum is studied anew and various theories are tested

Numerical modelling and experimental study of liquid evaporation during gel formation

Science.gov (United States)

Pokusaev, B. G.; Khramtsov, D. P.

2017-11-01

Gels are promising materials in biotechnology and medicine as a medium for storing cells for bioprinting applications. Gel is a two-phase system consisting of solid medium and liquid phase. Understanding of a gel structure evolution and gel aging during liquid evaporation is a crucial step in developing new additive bioprinting technologies. A numerical and experimental study of liquid evaporation was performed. In experimental study an evaporation process of an agarose gel layer located on Petri dish was observed and mass difference was detected using electronic scales. Numerical model was based on a smoothed particle hydrodynamics method. Gel in a model was represented as a solid-liquid system and liquid evaporation was modelled due to capillary forces and heat transfer. Comparison of experimental data and numerical results demonstrated that model can adequately represent evaporation process in agarose gel.

On the complexity of numerical analysis

DEFF Research Database (Denmark)

Miltersen, Peter Bro; Allender, Eric; Burgisser, Peter

2009-01-01

an integer N, decide whether N>0. • In the Blum-Shub-Smale model, polynomial time computation over the reals (on discrete inputs) is polynomial-time equivalent to PosSLP, when there are only algebraic constants. We conjecture that using transcendental constants provides no additional power, beyond nonuniform...... reductions to PosSLP, and we present some preliminary results supporting this conjecture. • The Generic Task of Numerical Computation is also polynomial-time equivalent to PosSLP. We prove that PosSLP lies in the counting hierarchy. Combining this with work of Tiwari, we obtain that the Euclidean Traveling......We study two quite different approaches to understanding the complexity of fundamental problems in numerical analysis: • The Blum-Shub-Smale model of computation over the reals. • A problem we call the “Generic Task of Numerical Computation,” which captures an aspect of doing numerical computation...

Numerical Gram-Schmidt orthonormalization

International Nuclear Information System (INIS)

Werneth, Charles M; Dhar, Mallika; Maung, Khin Maung; Sirola, Christopher; Norbury, John W

2010-01-01

A numerical Gram-Schmidt orthonormalization procedure is presented for constructing an orthonormal basis function set from a non-orthonormal set, when the number of basis functions is large. This method will provide a pedagogical illustration of the Gram-Schmidt procedure and can be presented in classes on numerical methods or computational physics.

Experimental and numerical study of the pressure drop for ITER blanket shield block

Energy Technology Data Exchange (ETDEWEB)

Ha, Min-Su; Kim, Sawoong; Jung, Hun-Chea; Shim, Hee-Jin; Ahn, Hee-Jae

2016-11-01

Highlights: • The results of the experiment and the numerical analysis are compared. • The numerical analysis results are lower than the experimental results. • The margin of the pressure drop is suggested. - Abstract: The blanket shield block (SB) is located inside the ITER vacuum chamber, and the main function is to provide the thermal and nuclear shielding to the vacuum vessel and external components. The SB is foreseen to undergo a significant heat load which is a body load throughout the whole thickness of the SB under normal operation conditions. Therefore, the cooling configuration in SB should be designed very carefully based on the various experiences. The pressure drop in the cooling design is one of the most important factors to balance a water distribution of overall blanket cooling system. In order to verify the pressure drop characteristic and validate the design methodology of SB, experiment and numerical analysis are performed and compared their results. These results would be a benchmarking of the numerical results with experimental results to assess the gap between calculations and experiments.

Numerical and experimental study of two turbulent opposed plane jets

Energy Technology Data Exchange (ETDEWEB)

Besbes, Sonia; Mhiri, Hatem [Laboratoire de Mecanique des Fluides et Thermique, Ecole Nationale d' Ingenieurs de Monastir, Route de Ouardanine, Monastir (Tunisia); Le Palec, Georges; Bournot, Philippe [Institut de Mecanique de Marseille, UNIMECA, Technopole de Chateau-Gombert, 60 rue Joliot-Curie, 13453 Marseille (France)

2003-09-01

The turbulent interaction between two opposed plane jets separated by a distance H is experimentally studied by using a PIV (Particle Image Velocimetry) method and numerically investigated by means of a finite volume code. Two turbulence models have been tested: the standard k-{epsilon} model and a second-order model. The validation of the numerical study was performed by comparing the results with experimental data obtained for the case of two interacting opposed jets at ambient temperature (isothermal case). The effect of the angle of inclination of the jets is studied. Conclusions of the validation are then used to study the interaction between two jets, one being maintained at ambient temperature whereas the other is heated. Results show that the stagnation point moves towards the heated jet. It is shown that the heating induces a stabilizing effect on the flow. (orig.)

Numerical study of glare spot phase Doppler anemometry

Science.gov (United States)

Hespel, C.; Ren, K. F.; Gréhan, G.; Onofri, F.

2008-03-01

The phase Doppler anemometry has (PDA) been developed to measure simultaneously the velocity and the size of droplets. When the concentration of particles is high, tightly focused beams must be used, as in the dual burst PDA. The latter permits an access to the refractive index of the particle, but the effect of wave front curvature of the incident beams becomes evident. In this paper, we introduce a glare spot phase Doppler anemometry which uses two large beams. The images of the particle formed by the reflected and refracted light, known as glare spots, are separated in space. When a particle passes through the probe volume, the two parts in a signal obtained by a detector in forward direction are then separated in time. If two detectors are used the phase differences and the intensity ratios between two signals, the distance between the reflected and refracted spots can be obtained. These measured values provide information about the particle diameter and its refractive index, as well as its two velocity components. This paper is devoted to the numerical study of such a configuration with two theoretical models: geometrical optics and rigorous electromagnetism solution.

Experimental and numerical study of the flow field around a small car

Directory of Open Access Journals (Sweden)

Dobrev Ivan

2017-01-01

Full Text Available This paper presents the aerodynamic study of a small car, which participated in Shell Ecomarathon Europe competition in the Urban Concept Hydrogen class. The goal is to understand the flow field around the vehicle. First, the flow is studied numerically using computational aerodynamics. The numerical simulation is carried out by means of CFD Fluent in order to obtain the drag force experienced by the vehicle and also the flow field. Then the flow field around the car is studied in a wind tunnel by means of particle image velocimetry (PIV. The comparison of the flow fields obtained numerically and experimentally shows good correspondence. The obtained results are very helpful for future car development and permit to improve the drag and to obtain a good stability.

Numeric invariants from multidimensional persistence

Energy Technology Data Exchange (ETDEWEB)

Skryzalin, Jacek [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Carlsson, Gunnar [Stanford Univ., Stanford, CA (United States)

2017-05-19

In this paper, we analyze the space of multidimensional persistence modules from the perspectives of algebraic geometry. We first build a moduli space of a certain subclass of easily analyzed multidimensional persistence modules, which we construct specifically to capture much of the information which can be gained by using multidimensional persistence over one-dimensional persistence. We argue that the global sections of this space provide interesting numeric invariants when evaluated against our subclass of multidimensional persistence modules. Lastly, we extend these global sections to the space of all multidimensional persistence modules and discuss how the resulting numeric invariants might be used to study data.

Experimental and numerical studies of high-velocity impact fragmentation

Energy Technology Data Exchange (ETDEWEB)

Kipp, M.E.; Grady, D.E.; Swegle, J.W.

1993-08-01

Developments are reported in both experimental and numerical capabilities for characterizing the debris spray produced in penetration events. We have performed a series of high-velocity experiments specifically designed to examine the fragmentation of the projectile during impact. High-strength, well-characterized steel spheres (6.35 mm diameter) were launched with a two-stage light-gas gun to velocities in the range of 3 to 5 km/s. Normal impact with PMMA plates, thicknesses of 0.6 to 11 mm, applied impulsive loads of various amplitudes and durations to the steel sphere. Multiple flash radiography diagnostics and recovery techniques were used to assess size, velocity, trajectory and statistics of the impact-induced fragment debris. Damage modes to the primary target plate (plastic) and to a secondary target plate (aluminum) were also evaluated. Dynamic fragmentation theories, based on energy-balance principles, were used to evaluate local material deformation and fracture state information from CTH, a three-dimensional Eulerian solid dynamics shock wave propagation code. The local fragment characterization of the material defines a weighted fragment size distribution, and the sum of these distributions provides a composite particle size distribution for the steel sphere. The calculated axial and radial velocity changes agree well with experimental data, and the calculated fragment sizes are in qualitative agreement with the radiographic data. A secondary effort involved the experimental and computational analyses of normal and oblique copper ball impacts on steel target plates. High-resolution radiography and witness plate diagnostics provided impact motion and statistical fragment size data. CTH simulations were performed to test computational models and numerical methods.

Numerical study of droplet impact and rebound on superhydrophobic surface

Science.gov (United States)

Cai, Xuan; Wu, Yanchen; Woerner, Martin; Frohnapfel, Bettina

2017-11-01

Droplet impact and rebound on superhydrophobic surface is an important process in many applications; among them are developing self-cleaning or anti-icing materials and limiting liquid film formation of Diesel Exhaust Fluid (DEF) in exhaust gas pipe. In the latter field, rebound of DEF droplet from wall is desired as an effective mean for avoiding or reducing unwanted solid deposition. Our goal is to numerically study influence of surface wettability on DEF droplet impact and rebound behavior. A phase-field method is chosen, which was implemented in OpenFOAM by us and validated for wetting-related interfacial flow problems. In the present contribution we first numerically reproduce relevant experimental studies in literature, to validate the code for droplet impact and rebound problem. There we study droplet-surface contact time, maximum/instantaneous spreading factor and droplet shape evolution. Our numerical results show good agreement with experimental data. Next we investigate for DEF droplets the effects of diameter, impact velocity and surface wettability on rebound behavior and jumping height. Based on Weber number and equilibrium contact angle, two regimes are identified. We show that surface wettability is a deciding factor for achieving rebound event. This work is supported by Foundation ``Friedrich-und-Elisabeth Boysen Stiftung fuer Forschung und Innovation'' (BOY-127-TP1).

Probabilistic numerics and uncertainty in computations.

Science.gov (United States)

Hennig, Philipp; Osborne, Michael A; Girolami, Mark

2015-07-08

We deliver a call to arms for probabilistic numerical methods : algorithms for numerical tasks, including linear algebra, integration, optimization and solving differential equations, that return uncertainties in their calculations. Such uncertainties, arising from the loss of precision induced by numerical calculation with limited time or hardware, are important for much contemporary science and industry. Within applications such as climate science and astrophysics, the need to make decisions on the basis of computations with large and complex data have led to a renewed focus on the management of numerical uncertainty. We describe how several seminal classic numerical methods can be interpreted naturally as probabilistic inference. We then show that the probabilistic view suggests new algorithms that can flexibly be adapted to suit application specifics, while delivering improved empirical performance. We provide concrete illustrations of the benefits of probabilistic numeric algorithms on real scientific problems from astrometry and astronomical imaging, while highlighting open problems with these new algorithms. Finally, we describe how probabilistic numerical methods provide a coherent framework for identifying the uncertainty in calculations performed with a combination of numerical algorithms (e.g. both numerical optimizers and differential equation solvers), potentially allowing the diagnosis (and control) of error sources in computations.

Numerical simulation of trapped dipolar quantum gases: Collapse studies and vortex dynamics

KAUST Repository

Sparber, Christof; Markowich, Peter; Huang, Zhongyi

2010-01-01

We numerically study the three dimensional Gross-Pitaevskii equation for dipolar quantum gases using a time-splitting algorithm. We are mainly concerned with numerical investigations of the possible blow-up of solutions, i.e. collapse of the condensate, and the dynamics of vortices. © American Institute of Mathematical Sciences.

Numerical study of dense adjoint 2-color matter

International Nuclear Information System (INIS)

Hands, S.; Scorzato, L.; Oevers, M.

2000-11-01

We study the global symmetries of SU(2) gauge theory with N flavors of staggered fermions in the presence of a chemical potential. We motivate the special interest of the case N=1 (staggered) with fermions in the adjoint representation of the gauge group. We present results from numerical simulations with both hybrid Monte Carlo and the two-step multi-bosonic algorithm. (orig.)

Numerical study of cosmic censorship in string theory

International Nuclear Information System (INIS)

Gutperle, Michael; Kraus, Per

2004-01-01

Recently Hertog, Horowitz, and Maeda have argued that cosmic censorship can be generically violated in string theory in anti-de Sitter spacetime by considering a collapsing bubble of a scalar field whose mass saturates the Breitenlohner-Freedman bound. We study this system numerically, and find that black holes form rather than naked singularities, implying that cosmic censorship is upheld. (author)

Numerical study of cosmic censorship in string theory

Energy Technology Data Exchange (ETDEWEB)

Gutperle, Michael E-mail: gutperle@physics.ucla.edu; Kraus, Per

2004-04-01

Recently Hertog, Horowitz, and Maeda have argued that cosmic censorship can be generically violated in string theory in anti-de Sitter spacetime by considering a collapsing bubble of a scalar field whose mass saturates the Breitenlohner-Freedman bound. We study this system numerically, and find that black holes form rather than naked singularities, implying that cosmic censorship is upheld. (author)

Experimental and Numerical Study on the Tensile Behaviour of UACS/Al Fibre Metal Laminate

Science.gov (United States)

Xue, Jia; Wang, Wen-Xue; Zhang, Jia-Zhen; Wu, Su-Jun; Li, Hang

2015-10-01

A new fibre metal laminate fabricated with aluminium sheets and unidirectionally arrayed chopped strand (UACS) plies is proposed. The UACS ply is made by cutting parallel slits into a unidirectional carbon fibre prepreg. The UACS/Al laminate may be viewed as aluminium laminate reinforced by highly aligned, discontinuous carbon fibres. The tensile behaviour of UACS/Al laminate, including thermal residual stress and failure progression, is investigated through experiments and numerical simulation. Finite element analysis was used to simulate the onset and propagation of intra-laminar fractures occurring within slits of the UACS plies and delamination along the interfaces. The finite element models feature intra-laminar cohesive elements inserted into the slits and inter-laminar cohesive elements inserted at the interfaces. Good agreement are obtained between experimental results and finite element analysis, and certain limitations of the finite element models are observed and discussed. The combined experimental and numerical studies provide a detailed understanding of the tensile behaviour of UACS/Al laminates.

The Preliminary Study for Numerical Computation of 37 Rod Bundle in CANDU Reactor

International Nuclear Information System (INIS)

Jeon, Yu Mi; Bae, Jun Ho; Park, Joo Hwan

2010-01-01

A typical CANDU 6 fuel bundle consists of 37 fuel rods supported by two endplates and separated by spacer pads at various locations. In addition, the bearing pads are brazed to each outer fuel rod with the aim of reducing the contact area between the fuel bundle and the pressure tube. Although the recent progress of CFD methods has provided opportunities for computing the thermal-hydraulic phenomena inside of a fuel channel, it is yet impossible to reflect the detailed shape of rod bundle on the numerical computation due to a lot of computing mesh and memory capacity. Hence, the previous studies conducted a numerical computation for smooth channels without considering spacers, bearing pads. But, it is well known that these components are an important factor to predict the pressure drop and heat transfer rate in a channel. In this study, the new computational method is proposed to solve the complex geometry such as a fuel rod bundle. In front of applying the method to the problem of 37 rod bundle, the validity and the accuracy of the method are tested by applying the method to the simple geometry. Based on the present result, the calculation for the fully shaped 37-rod bundle is scheduled for the future works

Numerical studies of film formation in context of steel coating

Science.gov (United States)

Aniszewski, Wojciech; Zaleski, Stephane; Popinet, Stephane

2017-11-01

In this work, we present a detailed example of numerical study of film formation in the context of metal coating. Liquid metal is drawn from a reservoir onto a retracting solid sheet, forming a coating film characterized by phenomena such as longitudinal thickness variation (in 3D) or waves akin to that predicted by Kapitza and Kapitza (visible in two dimensions as well). While the industry standard configuration for Zinc coating is marked by coexistence of medium Capillary number (Ca = 0.03) and film Reynolds number above 1000, we present also parametric studies in order to establish more clearly to what degree does the numerical method influence film regimes obtained in the target configuration. The simulations have been performed using Basilisk, a grid-adapting, strongly optimized code derived from Gerris . Mesh adaptation allows for arbitrary precision in relevant regions such as the contact line or the meniscus, while a coarse grid is applied elsewhere. This adaptation strategy, as the results indicate, is the only realistic approach for numerical method to cover the wide range of necessary scales from the predicted film thickness (hundreds of microns) to the domain size (meters).

Advanced Dynamics Analytical and Numerical Calculations with MATLAB

CERN Document Server

Marghitu, Dan B

2012-01-01

Advanced Dynamics: Analytical and Numerical Calculations with MATLAB provides a thorough, rigorous presentation of kinematics and dynamics while using MATLAB as an integrated tool to solve problems. Topics presented are explained thoroughly and directly, allowing fundamental principles to emerge through applications from areas such as multibody systems, robotics, spacecraft and design of complex mechanical devices. This book differs from others in that it uses symbolic MATLAB for both theory and applications. Special attention is given to solutions that are solved analytically and numerically using MATLAB. The illustrations and figures generated with MATLAB reinforce visual learning while an abundance of examples offer additional support. This book also: Provides solutions analytically and numerically using MATLAB Illustrations and graphs generated with MATLAB reinforce visual learning for students as they study Covers modern technical advancements in areas like multibody systems, robotics, spacecraft and des...

Advanced Numerical and Theoretical Methods for Photonic Crystals and Metamaterials

Science.gov (United States)

Felbacq, Didier

2016-11-01

This book provides a set of theoretical and numerical tools useful for the study of wave propagation in metamaterials and photonic crystals. While concentrating on electromagnetic waves, most of the material can be used for acoustic (or quantum) waves. For each presented numerical method, numerical code written in MATLAB® is presented. The codes are limited to 2D problems and can be easily translated in Python or Scilab, and used directly with Octave as well.

Numerical Studies of a Fluidic Diverter for Flow Control

Science.gov (United States)

Gokoglu, Suleyman A.; Kuczmarski, Maria A.; Culley, Dennis E.; Raghu, Surya

2009-01-01

The internal flow structure in a specific fluidic diverter is studied over a range from low subsonic to sonic inlet conditions by a time-dependent numerical analysis. The understanding will aid in the development of fluidic diverters with minimum pressure losses and advanced designs of flow control actuators. The velocity, temperature and pressure fields are calculated for subsonic conditions and the self-induced oscillatory behavior of the flow is successfully predicted. The results of our numerical studies have excellent agreement with our experimental measurements of oscillation frequencies. The acoustic speed in the gaseous medium is determined to be a key factor for up to sonic conditions in governing the mechanism of initiating the oscillations as well as determining its frequency. The feasibility of employing plasma actuation with a minimal perturbation level is demonstrated in steady-state calculations to also produce oscillation frequencies of our own choosing instead of being dependent on the fixed-geometry fluidic device.

A Numerical Modeling for Study Marine Current in the Manado Bay, North Sulawesi

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Parabelem Tinno Dolf Rompas

2018-02-01

Full Text Available This study is investigating about marine currents provided electrical energy through the numerical model. The objective of this study is to know the available power distributions in the Manado Bay, North Sulawesi, Indonesia. The Manado Bay was width 2200 m with 79 m of depth. In computation, we are made grids in x and y horizontal were 7 m respectively, also for z vertical of four layers. The results shown that the available power distributions in the Manado Bay at 0.1 Sv were 0.00-20.00 kW/m2 when low tide currents and when high tide currents were 0.00-105 kW/m2. The values will enable for marine currents power plant in the Manado Bay to future.

Numerical study of magnetic field effect on nano-fluid forced convection in a channel

Energy Technology Data Exchange (ETDEWEB)

Heidary, H., E-mail: Heidary_ha@aut.ac.ir [Department of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran (Iran, Islamic Republic of); Hosseini, R. [Department of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran (Iran, Islamic Republic of); Pirmohammadi, M., E-mail: Pirmohamadi@pardisiau.ac.ir [Department of Mechanical Engineering, Pardis Branch, Islamic Azad University, Pardis New City, Tehran (Iran, Islamic Republic of); Kermani, M.J. [Department of Mechanical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran (Iran, Islamic Republic of)

2015-01-15

In this study heat transfer and fluid flow analysis in a straight channel utilizing nano-fluid is numerically studied, while flow field is under magnetic field. Usage of nano-particles in base fluid and also applying magnetic field transverse to fluid velocity are two ways recommended in this paper to enhance heat exchange in straight duct. The fluid temperature at the channel inlet (T{sub in}) is taken less than that of the walls (T{sub w}). With assuming thermal equilibrium state of both the fluid phase and nano-particles and ignoring the slip velocity between the phases, single phase approach is used for modeling of nano-fluid. The governing equations are numerically solved in the domain by the control volume approach based on the SIMPLE technique. Numerical studies are performed over a range of Reynolds number, nano-fluid volume fraction and Hartmann number. The influence of these parameters is investigated on the local and average Nusselt numbers. Computations show excellent agreement with the literature. From this study, it is concluded that heat transfer in channels can enhance up to 75% due to the presence of nano-particles and magnetic field in channels. In industrial applications for cooling or heating purposes, the recommended ways in this paper, can provide helpful guidelines to the manufacturers to enhance efficiencies without heat exchanger area increase. - Highlights: • Addition of 10% nano-particles (copper here) can enhance the heat exchange by 26%. • Presence of magnetic field with Ha=30 in pure fluid can enhance the heat exchange by 50%. • Presence of magnetic field and nanofluid with Ha=30 and ϕ=0.1, can enhance the heat exchange by 76%. • Increasing Re{sub H} from 50 to 1000, the average Nu number can increase by a factor of ≈3.

Numerical study of two dimensional disordered systems in an external magnetic field

International Nuclear Information System (INIS)

Jana, Debnarayan

2000-01-01

We study here 2d tight-binding disordered model in an external magnetic field. By numerically diagonalizing the Hamiltonian, we characterize the eigenstates by Generalized Inverse Participation Ratio (GIPR). The properties of the eigenstates have been studied in case of random flux model as well as with the strength of disorder. Simple theoretical arguments are given in support of the numerical observation. Finally, we have also studied the multifractality of the eigenstates. All these study may shed light on the eigenstates in the center of the band in case of Integer Quantum Hall Effect (IQHE). (author)

Theoretical and Numerical Study of Seismoelectric Logs for Logging While Drilling (LWD

Directory of Open Access Journals (Sweden)

Sun Xiang-Yang

2017-01-01

Full Text Available When the acoustic field propagates in the porous medium, the electromagnetic wave can be induced by the seismoelectric effects which can be used in the logging. This paper studies the seismoelectric wave field and deduces the formulations of the acoustic and electromagnetic field of the liquid in the well, and gives the acoustic and electromagnetic boundary conditions between the driller collar and the log liquid, when the driller collar is added. We also do the numerical simulation of the seismoelectric wave field excited by monopole source, study the velocity dispersion characteristics of the acoustic and electromagnetic field, and investigate the detective depth of the seismoelectric logs. Through the simulation we know the seismoelectric logs can avoid the interference of drill collar wave. This paper also provides theoretical guidance for the design of receiving antenna.

Numerical studies of unsteady coherent structures and transport in two-dimensional flows

Energy Technology Data Exchange (ETDEWEB)

Hesthaven, J.S.

1995-08-01

The dynamics of unsteady two-dimensional coherent structures in various physical systems is studied through direct numerical solution of the dynamical equations using spectral methods. The relation between the Eulerian and the Lagrangian auto-correlation functions in two-dimensional homogeneous, isotropic turbulence is studied. A simple analytic expression for the Eulerian and Lagrangian auto-correlation function for the fluctuating velocity field is derived solely on the basis of the one-dimensional power spectrum. The long-time evolution of monopolar and dipolar vortices in anisotropic systems relevant for geophysics and plasma physics is studied by direct numerical solution. Transport properties and spatial reorganization of vortical structures are found to depend strongly on the initial conditions. Special attention is given to the dynamics of strong monopoles and the development of unsteady tripolar structures. The development of coherent structures in fluid flows, incompressible as well as compressible, is studied by novel numerical schemes. The emphasis is on the development of spectral methods sufficiently advanced as to allow for detailed and accurate studies of the self-organizing processes. (au) 1 ill., 94 refs.

Numerical study of the heat transfer in wound woven wire matrix of a Stirling regenerator

International Nuclear Information System (INIS)

Costa, S.C.; Barrutia, Harritz; Esnaola, Jon Ander; Tutar, Mustafa

2014-01-01

Highlights: • A correlation equation to characterize regenerator heat transfer is proposed. • Proposed correlation can be used as a effective tool to optimize the heat transfer. • Thermal efficiency can be maximized by optimizing Stirling regenerator heat transfer. • The wound woven wire matrix provides lower Nusselt numbers compared to stacked. • The developed correlation can be used for Reynolds number range from 4 to 400. - Abstract: Nusselt number correlation equations are numerically derived by characterizing the heat transfer phenomena through porous medium of both stacked and wound woven wire matrices of a Stirling engine regenerator over a specified range of Reynolds number, diameter and porosity. A finite volume method (FVM) based numerical approach is proposed and validated against well known experimentally obtained empirical correlations for a random stacking woven wire matrix, the most widely used due to fabrication issues, for Reynolds number up to 400. The results show that the numerically derived correlation equation corresponds well with the experimentally obtained correlations with less than 6% deviation with the exception of low Reynolds numbers. Once the numerical approach is validated, the study is further extended to characterize the heat transfer in a wound woven wire matrix model for a diameter range from 0.08 to 0.11 mm and a porosity range from 0.60 to 0.68 within the same Reynolds number range. Thus, the new correlation equations are numerically derived for different flow configurations of the Stirling engine regenerator. It is believed that the developed correlations can be applied with confidence as a cost effective solution to characterize and hence to optimize stacked and wound woven wire Stirling regenerator in the above specified ranges

Experimental and numerical study of the degradation of radioactive measurements in the filters of airborne radioactive surveillance systems

International Nuclear Information System (INIS)

Geryes, Tony

2009-01-01

The measurement of radioactivity in the filters of airborne radioactive surveillance systems is a major metrology difficulty due to the fact that the absorption of a radiation in the filter media and the mass of aerosols accumulated distort the nuclear counting response. This thesis focuses on the determination of correction factors for the radioactivity loss in the survey filters. In a first step, radioactive filters representing the atmospheric samples have been prepared using the nuclear test bench ICARE. The experimental study on reference filters provided a database to determine correction factors for various filtration conditions. The second part proposes a new numerical method developed to determine the correction factors. It consists of coupling GeoDict for particles filtration simulations and MCNPX simulations for a transport in matter. The good agreement obtained by comparing the numerical and experimental correction factors has permitted to validate the numerical model

Average-case analysis of numerical problems

CERN Document Server

2000-01-01

The average-case analysis of numerical problems is the counterpart of the more traditional worst-case approach. The analysis of average error and cost leads to new insight on numerical problems as well as to new algorithms. The book provides a survey of results that were mainly obtained during the last 10 years and also contains new results. The problems under consideration include approximation/optimal recovery and numerical integration of univariate and multivariate functions as well as zero-finding and global optimization. Background material, e.g. on reproducing kernel Hilbert spaces and random fields, is provided.

Numerical and experimental study on a pulsed-dc plasma jet

Science.gov (United States)

Liu, X. Y.; Pei, X. K.; Lu, X. P.; Liu, D. W.

2014-06-01

A numerical and experimental study of plasma jet propagation in a low-temperature, atmospheric-pressure, helium jet in ambient air is presented. A self-consistent, multi-species, two-dimensional axially symmetric plasma model with detailed finite-rate chemistry of helium-air mixture composition is used to provide insights into the propagation of the plasma jet. The obtained simulation results suggest that the sheath forms near the dielectric tube inner surface and shields the plasma channel from the tube surface. The strong electric field at the edge of the dielectric field enhances the ionization in the air mixing layer; therefore, the streamer head becomes ring-shaped when the streamer runs out of the tube. The avalanche-to-streamer transition is the main mechanism of streamer advancement. Penning ionization dominates the ionization reactions and increases the electrical conductivity of the plasma channel. The simulation results are supported by experimental observations under similar discharge conditions.

Numerical analysis of data in dynamic function studies

International Nuclear Information System (INIS)

Riihimaeki, E.

1975-01-01

Relations between tracer theories, models for organ function and the numerical solution of parameters from tracer experiments are reviewed. A unified presentation is given in terms of systems theory. Dynamic tracer studies should give the flow and volume of the tracer and, possibly, indications of the internal structure of the organ studied. Proper program writing will facilitate the exchange of the programs between the users and thereby avoid duplication of effort. An important attribute in this respect is machine independence of the programs which is achieved by the use of a high-level language. (author)

A student's guide to numerical methods

CERN Document Server

Hutchinson, Ian H

2015-01-01

This concise, plain-language guide for senior undergraduates and graduate students aims to develop intuition, practical skills and an understanding of the framework of numerical methods for the physical sciences and engineering. It provides accessible self-contained explanations of mathematical principles, avoiding intimidating formal proofs. Worked examples and targeted exercises enable the student to master the realities of using numerical techniques for common needs such as solution of ordinary and partial differential equations, fitting experimental data, and simulation using particle and Monte Carlo methods. Topics are carefully selected and structured to build understanding, and illustrate key principles such as: accuracy, stability, order of convergence, iterative refinement, and computational effort estimation. Enrichment sections and in-depth footnotes form a springboard to more advanced material and provide additional background. Whether used for self-study, or as the basis of an accelerated introdu...

Hybrid undulator numerical optimization

Energy Technology Data Exchange (ETDEWEB)

Hairetdinov, A.H. [Kurchatov Institute, Moscow (Russian Federation); Zukov, A.A. [Solid State Physics Institute, Chernogolovka (Russian Federation)

1995-12-31

3D properties of the hybrid undulator scheme arc studied numerically using PANDIRA code. It is shown that there exist two well defined sets of undulator parameters which provide either maximum on-axis field amplitude or minimal higher harmonics amplitude of the basic undulator field. Thus the alternative between higher field amplitude or pure sinusoidal field exists. The behavior of the undulator field amplitude and harmonics structure for a large set of (undulator gap)/(undulator wavelength) values is demonstrated.

Analytical and numerical study of validation test-cases for multi-physic problems: application to magneto-hydro-dynamic

Directory of Open Access Journals (Sweden)

D Cébron

2016-04-01

Full Text Available The present paper is concerned with the numerical simulation of Magneto-Hydro-Dynamic (MHD problems with industrial tools. MHD has receivedattention some twenty to thirty years ago as a possible alternative inpropulsion applications; MHD propelled ships have even been designed forthat purpose. However, such propulsion systems have been proved of lowefficiency and fundamental researches in the area have progressivelyreceived much less attention over the past decades. Numerical simulationof MHD problem could however provide interesting solutions in the field ofturbulent flow control. The development of recent efficient numericaltechniques for multi-physic applications provide promising tool for theengineer for that purpose. In the present paper, some elementary testcases in laminar flow with magnetic forcing terms are analysed; equationsof the coupled problem are exposed, analytical solutions are derived ineach case and are compared to numerical solutions obtained with anumerical tool for multi-physic applications. The present work can be seenas a validation of numerical tools (based on the finite element method foracademic as well as industrial application purposes.

Mathematical study and numerical simulations of bi-kinetic plasma sheaths

International Nuclear Information System (INIS)

Badsi, Mehdi

2016-01-01

This thesis focuses on the construction and the numerical simulation theoretical models of plasmas in interaction with an absorbing wall. These models are based on two species Vlasov-Poisson or Vlasov-Ampere systems in the presence of boundary conditions. The expected stationary solutions must verify the balance of the flux of charges in the orthogonal direction to the wall. This feature is called the ambi-polarity. Through the study of a non linear Poisson equation, we prove the well-posedness of 1d-1v stationary Vlasov-Poisson system, for which we determine incoming particles distributions and a wall potential that induces the ambi-polarity as well as a non negative charge density hold. We also give a quantitative estimates of the thickness of the boundary layer that develops at the wall. These results are illustrated numerically. We prove the linear stability of the electronic stationary solution for a non-stationary Vlasov-Ampere system. Finally, we study a 1d-3v stationary Vlasov-Poisson system in the presence of a constant and parallel to the wall magnetic field. We determine incoming particles distributions and a wall potential so that the ambi-polarity holds. We study a non linear Poisson equation through a non linear functional energy that admits minimizers. We established some bounds on the numerical parameters inside which, our model is relevant and we propose an interpretation of the results. (author)

Experimental and numerical study of light gas dispersion in a ventilated room

Energy Technology Data Exchange (ETDEWEB)

Gelain, Thomas, E-mail: thomas.gelain@irsn.fr; Prévost, Corinne

2015-11-15

Highlights: • Presentation of many experimental local data for different configurations. • Highlight of the influence of numerical parameters used in the CFD code. • Validation of the CFD code ANSYS CFX on the basis of experimental data. - Abstract: The objective of this study is to validate the ANSYS CFX version 12 computational code on the basis of light gas dispersion tests performed in two ventilated rooms. It follows an initial study on heavy gas dispersion carried out by Ricciardi et al. (2008). First, a study of sensitivity to various numerical parameters allows a set of reference data to be developed and the influence of the numerical scheme of advection to be revealed. Second, two helium (simulating hydrogen) dispersion test grids are simulated for the two rooms studied, and the results of the calculations are compared with experimental results. The very good agreement between these results allows the code and its dataset to be validated for this application. In future, a study with higher levels of helium (on the order of 4% vol at equilibrium) is envisaged in the context of safety analyses related to the hydrogen risk, these levels representing the lower explosive limit (LEL) of hydrogen.

Numerical study on flow rate limitation of open capillary channel flow through a wedge

Directory of Open Access Journals (Sweden)

Ting-Ting Zhang

2016-04-01

Full Text Available The flow characteristics of slender-column flow in wedge-shaped channel under microgravity condition are investigated in this work. The one-dimensional theoretical model is applied to predict the critical flow rate and surface contour of stable flow. However, the one-dimensional model overestimates the critical flow rate for not considering the extra pressure loss. Then, we develop a three-dimensional simulation method with OpenFOAM, a computational fluid dynamics tool, to simulate various phenomena in wedge channels with different lengths. The numerical results are verified with the capillary channel flow experimental data on the International Space Station. We find that the three-dimensional simulation perfectly predicts the critical flow rates and surface contours under various flow conditions. Meanwhile, the general behaviors in subcritical, critical, and supercritical flow are studied in three-dimensional simulation considering variations of flow rate and open channel length. The numerical techniques for three-dimensional simulation is validated for a wide range of configurations and is hopeful to provide valuable guidance for capillary channel flow experiment and efficient liquid management in space.

Failure of aluminium self-piercing rivets: An experimental and numerical study

International Nuclear Information System (INIS)

Hoang, N.-H.; Hopperstad, O.S.; Langseth, M.; Westermann, I.

2013-01-01

Highlights: ► We investigated the fracture mechanism of AA7278-T6 aluminium self-piercing rivets. ► Fracture of AA 7278-T6 rivets during the riveting process is a complex phenomenon. ► Microstructure of AA7278-T6 has significant influence on the fracture mechanism. ► Increasing friction will change the deformation mode of the rivet. - Abstract: The present paper investigates the fracture mechanisms of AA7278-T6 aluminium self-piercing rivets under compression during the riveting process. First, a microstructure investigation was conducted to disclose the grain structure and the particle distribution of the extruded aluminium alloy. Transmission electron micrographs revealed precipitate free zones along grain boundaries. Uniaxial tensile tests in three different directions with respect to the extrusion direction revealed anisotropy of the alloy in strength and ductility and a change in fracture mode with tensile direction. The behaviour of the alloy under compression was studied experimentally using upsetting tests and self-piercing riveting tests. Micrographs of the deformed specimens provided insight into the influence of the microstructure on the deformation and fracture of the alloy under compression. Second, numerical analyses were carried out using a 2-D axisymmetric model in LS–DYNA in an attempt to investigate the role of different physical variables on the final failure of the rivet. The numerical results revealed that constituent particles, precipitate free zones, and friction between the rivet and plates are important for strain localisation and fracture in the rivet

Insurer Market Power Lowers Prices In Numerous Concentrated Provider Markets.

Science.gov (United States)

Scheffler, Richard M; Arnold, Daniel R

2017-09-01

Using prices of hospital admissions and visits to five types of physicians, we analyzed how provider and insurer market concentration-as measured by the Herfindahl-Hirschman Index (HHI)-interact and are correlated with prices. We found evidence that in the range of the Department of Justice's and Federal Trade Commission's definition of a moderately concentrated market (HHI of 1,500-2,500), insurers have the bargaining power to reduce provider prices in highly concentrated provider markets. In particular, hospital admission prices were 5 percent lower and cardiologist, radiologist, and hematologist/oncologist visit prices were 4 percent, 7 percent, and 19 percent lower, respectively, in markets with high provider concentration and insurer HHI above 2,000, compared to such markets with insurer HHI below 2,000. We did not find evidence that high insurer concentration reduced visit prices for primary care physicians or orthopedists, however. The policy dilemma that arises from our findings is that there are no insurer market mechanisms that will pass a portion of these price reductions on to consumers in the form of lower premiums. Large purchasers of health insurance such as state and federal governments, as well as the use of regulatory approaches, could provide a solution. Project HOPE—The People-to-People Health Foundation, Inc.

Experimental and numerical studies on super-cavitating flow of axisymmetric cavitators

Directory of Open Access Journals (Sweden)

Byoung-Kwon Ahn

2010-03-01

Full Text Available Recently underwater systems moving at high speed such as a super-cavitating torpedo have been studied for their practical advantage of the dramatic drag reduction. In this study we are focusing our attention on super-cavitating flows around axisymmetric cavitators. A numerical method based on inviscid flow is developed and the results for several shapes of the cavitator are presented. First using a potential based boundary element method, we find the shape of the cavitator yielding a sufficiently large enough cavity to surround the body. Second, numerical predictions of supercavity are validated by comparing with experimental observations carried out in a high speed cavitation tunnel at Chungnam National University (CNU CT.

A numerical study on manoeuvrability of wind turbine installation vessel using OpenFOAM

Directory of Open Access Journals (Sweden)

Sungwook Lee

2015-05-01

Full Text Available In this study, a numerical prediction method on manoeuvrability of Wind Turbine Installation Vessel (WTIV is presented. Planar Motion Mechanism (PMM captive test for the bare hull of WTIV is carried out in the model basin and compared with the numerical results using RANS simulation based on Open-source Field Operation And Manipulation (OpenFOAM calculation to validate the developed method. The manoeuvrability of WTIV with skeg and/or without skeg is investigated using the numerical approach along with the captive model test. In the numerical calculations, the dynamic stability index which indicates the course keeping ability is evaluated and compared for three different hull configurations i.e. bare hull and other two hulls with center skeg and twin skeg. This paper proves that the numerical approach using RANS simulation can be readily applied to estimate the manoeuvrability of WTIV at the initial design stage.

Numerical Studies of Magnetohydrodynamic Activity Resulting from Inductive Transients. Final Report

International Nuclear Information System (INIS)

Sovinec, Carl R.

2005-01-01

This report describes results from numerical studies of transients in magnetically confined plasmas. The work has been performed by University of Wisconsin graduate students James Reynolds and Giovanni Cone and by the Principal Investigator through support from contract DE-FG02-02ER54687, a Junior Faculty in Plasma Science award from the DOE Office of Science. Results from the computations have added significantly to our knowledge of magnetized plasma relaxation in the reversed-field pinch (RFP) and spheromak. In particular, they have distinguished relaxation activity expected in sustained configurations from transient effects that can persist over a significant fraction of the plasma discharge. We have also developed the numerical capability for studying electrostatic current injection in the spherical torus (ST). These configurations are being investigated as plasma confinement schemes in the international effort to achieve controlled thermonuclear fusion for environmentally benign energy production. Our numerical computations have been performed with the NIMROD code (http://nimrodteam.org) using local computing resources and massively parallel computing hardware at the National Energy Research Scientific Computing Center. Direct comparisons of simulation results for the spheromak with laboratory measurements verify the effectiveness of our numerical approach. The comparisons have been published in refereed journal articles by this group and by collaborators at Lawrence Livermore National Laboratory (see Section 4). In addition to the technical products, this grant has supported the graduate education of the two participating students for three years

Methods of numerical relativity

International Nuclear Information System (INIS)

Piran, T.

1983-01-01

Numerical Relativity is an alternative to analytical methods for obtaining solutions for Einstein equations. Numerical methods are particularly useful for studying generation of gravitational radiation by potential strong sources. The author reviews the analytical background, the numerical analysis aspects and techniques and some of the difficulties involved in numerical relativity. (Auth.)

Finger-Based Numerical Skills Link Fine Motor Skills to Numerical Development in Preschoolers.

Science.gov (United States)

Suggate, Sebastian; Stoeger, Heidrun; Fischer, Ursula

2017-12-01

Previous studies investigating the association between fine-motor skills (FMS) and mathematical skills have lacked specificity. In this study, we test whether an FMS link to numerical skills is due to the involvement of finger representations in early mathematics. We gave 81 pre-schoolers (mean age of 4 years, 9 months) a set of FMS measures and numerical tasks with and without a specific finger focus. Additionally, we used receptive vocabulary and chronological age as control measures. FMS linked more closely to finger-based than to nonfinger-based numerical skills even after accounting for the control variables. Moreover, the relationship between FMS and numerical skill was entirely mediated by finger-based numerical skills. We concluded that FMS are closely related to early numerical skill development through finger-based numerical counting that aids the acquisition of mathematical mental representations.

A numerical methodology for the Painlevé equations

KAUST Repository

Fornberg, Bengt

2011-07-01

The six Painlevé transcendents PI-PVI have both applications and analytic properties that make them stand out from most other classes of special functions. Although they have been the subject of extensive theoretical investigations for about a century, they still have a reputation for being numerically challenging. In particular, their extensive pole fields in the complex plane have often been perceived as \\'numerical mine fields\\'. In the present work, we note that the Painlevé property in fact provides the opportunity for very fast and accurate numerical solutions throughout such fields. When combining a Taylor/Padé-based ODE initial value solver for the pole fields with a boundary value solver for smooth regions, numerical solutions become available across the full complex plane. We focus here on the numerical methodology, and illustrate it for the PI equation. In later studies, we will concentrate on mathematical aspects of both the PI and the higher Painlevé transcendents. © 2011 Elsevier Inc.

Numerical linear algebra with applications using Matlab

CERN Document Server

Ford, William

2014-01-01

Designed for those who want to gain a practical knowledge of modern computational techniques for the numerical solution of linear algebra problems, Numerical Linear Algebra with Applications contains all the material necessary for a first year graduate or advanced undergraduate course on numerical linear algebra with numerous applications to engineering and science. With a unified presentation of computation, basic algorithm analysis, and numerical methods to compute solutions, this book is ideal for solving real-world problems. It provides necessary mathematical background information for

Numerical analysis II essentials

CERN Document Server

REA, The Editors of; Staff of Research Education Association

1989-01-01

REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Numerical Analysis II covers simultaneous linear systems and matrix methods, differential equations, Fourier transformations, partial differential equations, and Monte Carlo methods.

Numerical taxonomic studies of some tribes of Brassicaceae from Egypt

NARCIS (Netherlands)

Abdel Khalik, K.; Maesen, van der L.J.G.; Koopman, W.J.M.; Berg, van den R.G.

2002-01-01

A systematic study of 45 taxa belonging to 23 genera of tribes Arabideae, Euclidieae, Hesperideae, Lunarieae, Matthioleae and Sisymbrieae of Brassicaceae from Egypt was conducted by means of numerical analysis based on sixty two morphological characters, including vegetative parts, pollen grains and

An Experimental and numerical Study for squeezing flow

Science.gov (United States)

Nathan, Rungun; Lang, Ji; Wu, Qianhong; Vucbmss Team

2017-11-01

We report an experimental and numerical study to examine the transient squeezing flow driven by sudden external impacts. The phenomenon is widely observed in industrial applications, e.g. squeeze dampers, or in biological systems, i.e. joints lubrication. However, there is a lack of investigation that captures the transient flow feature during the process. An experimental setup was developed that contains a piston instrumented with a laser displacement sensor and a pressure transducer. The heavy piston was released from rest, creating a fast compaction on the thin fluid gap underneath. The motion of the piston and the fluid pressure build-up was recorded. For this dynamic process, a CFD simulation was performed which shows excellent agreement with the experimental data. Both the numerical and experimental results show that, the squeezing flow starts with the inviscid limit when the viscous fluid effect has no time to appear, and thereafter becomes a developing flow, in which the inviscid core flow region decreases and the viscous wall region increases until the entire fluid gap is filled with viscous fluid flow. The study presented herein, filling the gap in the literature, will have broad impacts in industrial and biomedical applications. This research was supported by the National Science Foundation under Award 1511096, and supported by the Seed Grant from The Villanova Center for the Advancement of Sustainability in Engineering (VCASE).

Numerical models for differential problems

CERN Document Server

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...

Rayleigh-Benard convection in a Hele-Shaw cell - a numerical study

International Nuclear Information System (INIS)

Guenther, C.; Mueller, U.

1987-05-01

Free convection in narrow vertical gaps heated from below gives rise to several different flow patterns as has been demonstrated by previous experimental investigations. A numerical study is presented aimed at simulating the observed flow phenomena in Hele-Shaw cells of small lateral extend. The numerical study is based on the assumption that the flow is essentially two-dimensional. This allows an approach using a one-term Galerkin approximation with respect to the direction perpendicular to the gap and a finite difference scheme with regard to the coordinates in the plane of the gap. The calculations result in realistic values of the critical Rayleigh numbers for the onset of steady and oscillatory convection. Most of the observed unsteady flow patterns can be simulated numerically. It is shown that five different stable flow patterns can occur at one particular Rayleigh number. The different stable flow patterns are coupled by a variety of complex transitions. Moreover the calculations show that a realistic description of the observed flow phenomena can not be obtained by a simplified model using the Darcy law in the momentum equation and implying slip flow at the small confining boundaries. (orig.) [de

A numerical study of the eigenvalues in the neutron diffusion theory

International Nuclear Information System (INIS)

Lima Bezerra, J. de.

1982-12-01

A systematic numerical study for the eigenvalue problem in one dimension was carried out. A computer code RED2G was developed to obtain and to discuss a number of numerical solutions concerning eigenvalues problems originating from the discretization of the two groups neutron diffusion equation in one dimension and steady state. The problem of eigenvalues was created from the discretization by the method of finite differences. The solutions were obtained by four different iterative methods, i.e. Power, Wielandt-1, Wielandt-2 and accelerated Power with the Chebyshev polinomials. The numerical results given by the solution of the two test-problems indicate that the RED2G code is fast and efficient in these calculations and the Wielandt-2 method has been found to be the best both in respect of rapidity of calculations as well as programation effort required. (E.G.) [pt

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.

A numerical study of the integral equations for the laser fields in free-electron lasers

International Nuclear Information System (INIS)

Yoo, J. G.; Park, S. H.; Jeong, Y. U.; Lee, B. C.; Rhee, Y. J.; Cho, S. O.

2004-01-01

The dynamics of the radiation fields in free-electron lasers is investigated on the basis of the integro-differential equations in the one-dimensional formulation. For simple cases we solved the integro-differential equations analytically and numerically to test our numerical procedures developed on the basis of the Filon method. The numerical results showed good agreement with the analytical solutions. To confirm the legitimacy of the numerical package, we carried out numerical studies on the inhomogeneous broadening effects, where no analytic solutions are available, due to the energy spread and the emittance of the electron beam.

Numerical study of droplet evaporation in an acoustic levitator

Science.gov (United States)

Bänsch, Eberhard; Götz, Michael

2018-03-01

We present a finite element method for the simulation of all relevant processes of the evaporation of a liquid droplet suspended in an acoustic levitation device. The mathematical model and the numerical implementation take into account heat and mass transfer across the interface between the liquid and gaseous phase and the influence of acoustic streaming on this process, as well as the displacement and deformation of the droplet due to acoustic radiation pressure. We apply this numerical method to several theoretical and experimental examples and compare our results with the well-known d2-law for the evaporation of spherical droplets and with theoretical predictions for the acoustic streaming velocity. We study the influence of acoustic streaming on the distribution of water vapor and temperature in the levitation device, with special attention to the vapor distribution in the emerging toroidal vortices. We also compare the evaporation rate of a droplet with and without acoustic streaming, as well as the evaporation rates in dependence of different temperatures and sound pressure levels. Finally, a simple model of protein inactivation due to heat damage is considered and studied for different evaporation settings and their respective influence on protein damage.

Numerical study of damage evolution and failure in an electromagnetic corner fill operation

International Nuclear Information System (INIS)

Imbert, J.M.; Winkler, S.L.; Worswick, M.J.; Oliveira, D.A.; Golovashchenko, S.

2004-01-01

A numerical study of an electromagnetic corner fill operation using AA5754 aluminum alloy sheet was performed. Conical parts with side angles of 40 and 45 deg. (included angles of 100 and 90 deg.) were modeled. The numerical calculations were performed with an explicit dynamic finite element structural code, using an analytical electromagnetic pressure distribution. Damage evolution was predicted using a damage subroutine based on the Gurson-Tvergaard-Needleman constitutive model. Experiments were performed to validate the numerical results. Damage measurements were made using optical microscopy to determine the actual damage produced by the forming operations. Predicted final shape, failure and damage levels are presented and compared with experimental results. The numerical models were able to accurately predict damage trends. Failure was predicted in general agreement with the experiments

Numerical Modeling of Ablation Heat Transfer

Science.gov (United States)

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 study of extreme-ultra-violet generated plasmas in hydrogen

NARCIS (Netherlands)

Astakhov, Dmitry

2016-01-01

In this thesis, we present the development and study a numerical model of EUV-induced plasma. Understanding of behavior of low pressure low density plasmas is of industrial relevance, because of their potential use for on-line removal of different forms of contaminations from multilayer mirrors,

Mathematical and numerical study of non-linear models used in plasma physics

International Nuclear Information System (INIS)

Ebrard, G.

2005-12-01

We study the interaction of several crossing beams with a plasma in the Laser-Megajoule context. We start from Euler-Maxwell. The formal asymptotic is the Zakharov system. For simplified systems of Klein-Gordon-wave type, we justify an approximation by a Zakharov equation for solutions of large amplitude. We construct a new system that simulates the interaction of 2 beams and present a whole hierarchy of models. We introduce a numerical scheme using the known results on Zakharov-wave equations which are valid for short pulses. We give a scheme which eliminate the backscattering wave. We give some numerical results. Finally, we do several numerical simulations of laser-plasma interaction for the initial value problem and the boundary value problem. (author)

Study for discharge coefficient of flow nozzles. Prediction by using numerical simulation

International Nuclear Information System (INIS)

Ikeda, Hiroshi; Sakai, Norio; Yamamoto, Yasushi; Arai, Kenji; Matsumoto, Masaaki

2008-01-01

In nuclear plant, as water feeding into reactor have much effect on thermal power of plant, it is important to measure accurately the flow rate of water. Flow nozzle is on of typical differential pressure type flow meters and the discharge coefficient is used to calculate the flow rate. This coefficient is given by actual experiment and theory. We studied the theoretical assumption of the discharge coefficient curve using numerical simulation and evaluated the effect of flow nozzle configuration on the coefficient numerically and experimentally. As the result, numerical simulation can predict the discharge coefficient of theoretical curve within 0.3%. And we found that the throat length and throat tapping location of flow nozzle have much effect on the coefficient. (author)

Research status and some results of numerical system to study regional environment: SPEEDI-MP

International Nuclear Information System (INIS)

Chino, Masamichi

2004-01-01

Research status and some results of 'Numerical system to study regional environment: SPEEDI-MP', which reproduces circulations of materials in the atmospheric, oceanic and terrestrial environments, are introduced. The purpose of this system are the development of various environmental models, the connection of atmospheric, oceanic and terrestrial models and the construction of research bases for numerical environmental studies. In addition to the accurate prediction of environmental behavior of radionuclides, the system has been applied to the non-nuclear fields, e.g., numerical analysis of environmental effects to volcanic gases from Miyake Jima, real-time prediction of the migration of rice planthoppers from Eastern Asia. (author)

Experimental and numerical study on inlet and outlet conditions of a bulb turbine with considering free surface

International Nuclear Information System (INIS)

Zhao, Y P; Liao, W L; Feng, H D; Ruan, H; Luo, X Q

2012-01-01

For a bulb turbine, it has a low head and a big runner diameter, and the free surface influences the flow at the inlet and outlet of the turbine, which bring many problems such as vibration, cracks and cavitation to the turbine. Therefore, it is difficult to get the precise internal flow characteristics through a numerical simulation with conventional ideal flow conditions. In this paper, both numerical and experimental methods are adopted to investigate the flow characteristics at the inlet and outlet of the bulb turbine with considering free surface. Firstly, experimental and numerical studies in a low head pressure pipeline are conducted, and the corresponding boundary condition according with reality is obtained through the comparison between the model test result and the CFD simulation result. Then, through an analysis of the velocity and pressure fields at the inlet of the bulb turbine at different heads, the flow characteristics and rules at the entrance of the bulb turbine have been revealed with considering free surface; Finally, the performance predictions for a bulb turbine have been conducted by using the obtained flow rules at the inlet as the boundary condition of a turbine, and the causes that lead to non-uniform forces on blades, cavitation and vibration have been illustrated in this paper, which also provide a theory basis for an accurate numerical simulation and optimization design of a bulb turbine.

Recent results of seismic isolation study in CRIEPI: Numerical activities

International Nuclear Information System (INIS)

Shiojiri, Hiroo; Ishida, Katsuhiko; Yabana, Shurichi; Hirata, Kazuta

1992-01-01

Development of detailed numerical models of a bearing and the related isolation system Is necessary for establishing the rational design of the bearing and the system. The developed numerical models should be validated regarding the physical parameters and the basic assumption by comparing the experimental results with the numerical ones. The numerical work being conducted in CRIEPI consists of the following items: (1) Simple modeling of the behavior of the bearings capable of approximating the tests on bearings, and the validation of the model for the bearing by comparing the numerical results adopting the models with the shaking table tests results; (2) Detailed three-dimensional modeling of single bearings with finite-element codes, and the experimental validation of the model; (3)Simple and detailed three-dimensional modeling of isolation buildings and experimental validation

Experimental and numerical study of micro deep drawing

Directory of Open Access Journals (Sweden)

Luo Liang

2015-01-01

Full Text Available Micro forming is a key technology for an industrial miniaturisation trend, and micro deep drawing (MDD is a typical micro forming method. It has great advantages comparing to other micro manufacturing methods, such as net forming ability, mass production potential, high product quality and complex 3D metal products fabrication capacity. Meanwhile, it is facing difficulties, for example the so-called size effects, once scaled down to micro scale. To investigate and to solve the problems in MDD, a combined micro blanking-drawing machine is employed and an explicit-implicit micro deep drawing model with a voronoi blank model is developed. Through heat treatment different grain sizes can be obtained, which affect material's properties and, consequently, the drawing process parameters, as well as produced cups' quality. Further, a voronoi model can provide detailed material information in simulation, and numerical simulation results are in accordance with experimental results.

Numerical simulation system for environmental studies: SPEEDI-MP

International Nuclear Information System (INIS)

Nagai, Haruyasu; Chino, Masamichi; Terada, Hiroaki; Harayama, Takaya; Kobayashi, Takuya; Tsuduki, Katsunori; Kim, Keyong-Ok; Furuno, Akiko

2006-09-01

A numerical simulation system SPEEDI-MP has been developed to apply for various environmental studies. SPEEDI-MP consists of dynamical models and material transport models for the atmospheric, terrestrial, and oceanic environments, meteorological and geographical database for model inputs, and system utilities for file management, visualization, analysis, etc., using graphical user interfaces (GUIs). As a numerical simulation tool, a model coupling program (model coupler) has been developed. It controls parallel calculations of several models and data exchanges among them to realize the dynamical coupling of the models. A coupled model system for water circulation has been constructed with atmosphere, ocean, wave, hydrology, and land-surface models using the model coupler. System utility GUIs are based on the Web technology, allowing users to manipulate all the functions on the system using their own PCs via the internet. In this system, the source estimation function in the atmospheric transport model can be executed on the grid computer system. Performance tests of the coupled model system for water circulation were also carried out for the flood event at Saudi Arabia in January 2005 and the storm surge case by the hurricane KATRINA in August 2005. (author)

A numerical study for global atmospheric transport-chemistry problems

NARCIS (Netherlands)

E.J. Spee (Edwin); J.G. Verwer (Jan); P.M. de Zeeuw (Paul); J.G. Blom (Joke); W. Hundsdorfer (Willem)

1998-01-01

htmlabstractAtmospheric air quality modeling relies in part on numerical simulation. Required numerical simulations are often hampered by lack of computer capacity and computational speed. This problem is most severe in the field of global modeling where transport and exchange of trace constituents

A numerical study for global atmospheric transport-chemistry problems

NARCIS (Netherlands)

E.J. Spee (Edwin); J.G. Verwer (Jan); P.M. de Zeeuw (Paul); J.G. Blom (Joke); W. Hundsdorfer (Willem)

1997-01-01

textabstractAtmospheric air quality modeling relies in part on numerical simulation. Required numerical simulations are often hampered by lack of computer capacity and computational speed. This problem is most severe in the field of global modeling where transport and exchange of trace constituents

Numerical study of the evolution of a magnetized plasma by means of a hybrid model

Energy Technology Data Exchange (ETDEWEB)

Dinu, L [Institutul de Matematica, Bucharest (Romania); Vlad, M [Institutul de Fizica si Tehnologia Aparatelor cu Radiatii, Bucharest (Romania)

1979-01-01

A numerical solution of the Vlasov-fluid model describing a time and space plasma evolution is presented. This should be compared with J.P. Frjedberg's analysis (1), (2) which provides growth rates for instabilities and some stability criteria.

Numerical approach to one-loop integrals

International Nuclear Information System (INIS)

Fujimoto, Junpei; Shimizu, Yoshimitsu; Kato, Kiyoshi; Oyanagi, Yoshio.

1992-01-01

Two numerical methods are proposed for the calculation of one-loop scalar integrals. In the first method, the singularity is cancelled by the symmetrization of the integrand and the integration is done by a Monte-Carlo method. In the second one, after the transform of the integrand into a standard form, the integral is reduced into a regular numerical integral. These methods provide us practical tools to evaluate one-loop Feynman diagrams with desired numerical accuracy. They are extended to the integral with numerator and the treatment of the one-loop virtual correction to the cross section is also presented. (author)

Numerical computations with GPUs

CERN Document Server

Kindratenko, Volodymyr

2014-01-01

This book brings together research on numerical methods adapted for Graphics Processing Units (GPUs). It explains recent efforts to adapt classic numerical methods, including solution of linear equations and FFT, for massively parallel GPU architectures. This volume consolidates recent research and adaptations, covering widely used methods that are at the core of many scientific and engineering computations. Each chapter is written by authors working on a specific group of methods; these leading experts provide mathematical background, parallel algorithms and implementation details leading to

Numerical study on heat transfer characteristics of thermosyphon heat pipes using nanofluids

International Nuclear Information System (INIS)

Huminic, Gabriela; Huminic, Angel

2013-01-01

Highlights: • Numerical study of nanofluid heat transfer in thermosyphon heat pipes is performed. • Effect of nanoparticle concentration and operating temperature are studied. • Fe 2 O 3 –water nanofluid with 5.3% volume concentration shows the best performance. • Results show the improvement the thermal performances of thermosyphon heat pipe with nanofluids. - Abstract: In this work, a three-dimensional analysis is used to investigate the heat transfer of thermosyphon heat pipe using water and nanofluids as the working fluid. The study focused mainly on the effects of volume concentrations of nanoparticles and the operating temperature on the heat transfer performance of the thermosyphon heat pipe using the nanofluids. The analysis was performed for water and γ-Fe 2 O 3 nanoparticles, three volume concentrations of nanoparticles (0 vol.%, 2 vol.% and 5.3 vol.%) and four operating temperatures (60, 70, 80 and 90 °C). The numerical results show that the volume concentration of nanoparticles had a significant effect in reducing the temperature difference between the evaporator and condenser. Experimental and numerical results show qualitatively that the thermosyphon heat pipe using the nanofluid has better heat transfer characteristics than the thermosyphon heat pipe using water

Numerical and experimental study of a hydrodynamic cavitation tube

Science.gov (United States)

Hu, H.; Finch, J. A.; Zhou, Z.; Xu, Z.

1998-08-01

A numerical analysis of hydrodynamics in a cavitation tube used for activating fine particle flotation is described. Using numerical procedures developed for solving the turbulent k-ɛ model with boundary fitted coordinates, the stream function, vorticity, velocity, and pressure distributions in a cavitation tube were calculated. The calculated pressure distribution was found to be in excellent agreement with experimental results. The requirement of a pressure drop below approximately 10 m water for cavitation to occur was observed experimentally and confirmed by the model. The use of the numerical procedures for cavitation tube design is discussed briefly.

Numerical Study of Velocity Shear Stabilization of 3D and Theoretical Considerations for Centrifugally Confined Plasmas and Other Interchange-Limited Fusion Concepts

Energy Technology Data Exchange (ETDEWEB)

Hassam, Adil [Univ. of Maryland, College Park, MD (United States)

2015-09-21

We studied the feasibility of resonantly driving GAMs in tokamaks. A numerical simulation was carried out and showed the essential features and limitations. It was shown further that GAMs can damp by phase-mixing, from temperature gradients, or nonlinear detuning, thus broadening the resonance. Experimental implications of this were quantified. Theoretical support was provided for the Maryland Centrifugal Experiment, funded in a separate grant by DOE. Plasma diamagnetism from supersonic rotation was established. A theoretical model was built to match the data. Additional support to the experiment in terms of numerical simulation of the interchange turbulence was provided. Spectra from residual turbulence on account of velocity shear suppression were obtained and compared favorably to experiment. A new drift wave, driven solely by the thermal force, was identified.

A numerical study of a supercritical fluid jet

International Nuclear Information System (INIS)

Sierra-Pallares, J.; Garcia-Serna, J.; Cocero, M.J.; Parra-Santos, M.T.; Castro-Ruiz, F.

2009-01-01

This study affords the numerical solution of the mixing of a submerged turbulent jet under supercritical conditions and near-critical conditions. Turbulence plays a very important role in the behaviour of chemical engineering equipment. An accurate prediction of the turbulence at supercritical conditions with low computational cost is crucial in designing new processes such as reactions in supercritical media, high pressure separation processes, nanomaterials processing and heterogeneous catalysis. At high-pressure, the flow cannot be modelled accurately using the ideal-gas assumption. Therefore, the real gas models must be used in order to solve accurately the fluid flow and heat transfer problems where the working fluid behaviour deviate seriously from the ideal-gas assumption. The jet structure has three parts clearly distinguished: the injection, the transition and the fully developed jet. Once the flow is dominated by the turbulent eddies of the shear layer, the flow is fully developed and the radial profiles match a similarity profile. This work reports the state of the project that is not completed and is being processed now. This work is devoted to establish the distance downstream from the injector where the jet become self-preserving and the shape of the similarity profiles. This system is of interest in the design of supercritical reactor inlets, where two streams should be mixed in the shortest length, or mixing conditions strongly affect the behaviour of the processes. The numerical results have been validated with experimental measurements made in the jet mixing region. The radial profiles for average velocity, density and temperature are analyzed. The parameters of the profile that match better the numerical results are summarized in Table 1. The density requires a lower value of n than these for velocity and temperature, which reflect smoother profiles. These conclusions are in good agreement with the results from Oschwald and Schik. (author)

Gyrotactic trapping: A numerical study

Science.gov (United States)

Ghorai, S.

2016-04-01

Gyrotactic trapping is a mechanism proposed by Durham et al. ["Disruption of vertical motility by shear triggers formation of thin Phytoplankton layers," Science 323, 1067-1070 (2009)] to explain the formation of thin phytoplankton layer just below the ocean surface. This mechanism is examined numerically using a rational model based on the generalized Taylor dispersion theory. The crucial role of sedimentation speed in the thin layer formation is demonstrated. The effects of variation in different parameters on the thin layer formation are also investigated.

Study and simulation of a parallel numerical processing machine

International Nuclear Information System (INIS)

Bel Hadj, Slaheddine

1981-12-01

This study has been carried out in the perspective of the implementation on a minicomputer of the NEPTUNIX package (software for the resolution of very large algebra-differential equation systems). Aiming at increasing the system performance, a previous research work has shown the necessity of reducing the execution time of certain numerical computation tasks, which are of frequent use. It has also demonstrated the feasibility of handling these tasks with efficient algorithms of parallel type. The present work deals with the study and simulation of a parallel architecture processor adapted to the fast execution of these algorithms. A minicomputer fitted with a connection to such a parallel processor, has a greatly extended computing power. Then the architecture of a parallel numerical processor, based on the use of VLSI microprocessors and co-processors, is described. Its design aims at the best cost / performance ratio. The last part deals with the simulation processor with the 'CHAMBOR' program. Results show an increasing factor of 30 in speed, in comparison with the execution on a MITRA 15 minicomputer. Moreover the conflicts importance, mainly at the level of access to a shared resource is evaluated. Although this implementation has been designed having in mind a dedicated application, other uses could be envisaged, particularly for the simulation of nuclear reactors: operator guiding system, the behavioural study under accidental circumstances, etc. (author) [fr

Numerical study of microphase separation in gels and random media

International Nuclear Information System (INIS)

Uchida, Nariya

2004-01-01

Microphase separation in gels and random media is numerically studied using a Ginzburg-Landau model. A random field destroys long-range orientational (lamellar) order and gives rise to a disordered bicontinuous morphology. The dependence of the correlation length on the field strength is distinct from that of random-field magnets

A numerical study on the characteristics of gaseous pollutant absorbed by a moving liquid aerosol

International Nuclear Information System (INIS)

Deng, J.J.; Du, Y.G.; Yu, Y.; Ding, J.

2008-01-01

Atmospheric pollution involving aerosols is becoming increasingly problematic. Since aerosols are small in size and have large specific surface areas, they can enhance some chemical reactions. Liquid aerosols in the air can absorb gaseous pollutants to adversely affect air quality and human health. This paper studied the characteristics of liquid aerosols and the absorption process of gaseous pollutants. Specifically, the paper presented a model to depict the characteristic of the absorption process of gaseous pollutant by a liquid aerosol with internal circulation and chemical reaction. The model assumed that liquid aerosols retain a spherical shape while moving freely in air. The finite volume method was used to develop an algorithm used to numerically simulate the experimental work of Walcek. The paper also discussed the numerical evaluation of the transient momentum and mass transfer characteristics of sulphur dioxide into a droplet. It was concluded that the chemical reaction increased the rate of mass transfer and the quasi-saturation time of aerosols, which provided a theoretical basis for the heterogeneous reaction of liquid aerosols. 3 refs., 6 figs

Numerical study of hydrogen absorption in a LM-Ni5 hybride reactor

International Nuclear Information System (INIS)

Altinisik, K.; Tekin, M.; Mat, M. D.; Altinisik, A.; Veziroglu, T. N.

2007-01-01

Metal hydride formation in an Lm-Ni5 storage tank is numerically studied with a continuum mathematical model. The model considers complex heat, and mass transfer and chemical reaction in the reaction bed. It is found that hydride formation enhances at regions with lower equilibrium pressure. Absorbed hydrogen mass increases exponentially at earlier times of hydriding process and slow down after temperature of reaction bed increases due to the heat of reaction. Numerical results agree satisfactorily with the experimental data in the literature

Assessing mental stress from the photoplethysmogram: a numerical study

Science.gov (United States)

Charlton, Peter H; Celka, Patrick; Farukh, Bushra; Chowienczyk, Phil; Alastruey, Jordi

2018-01-01

Abstract Objective: Mental stress is detrimental to cardiovascular health, being a risk factor for coronary heart disease and a trigger for cardiac events. However, it is not currently routinely assessed. The aim of this study was to identify features of the photoplethysmogram (PPG) pulse wave which are indicative of mental stress. Approach: A numerical model of pulse wave propagation was used to simulate blood pressure signals, from which simulated PPG pulse waves were estimated using a transfer function. Pulse waves were simulated at six levels of stress by changing the model input parameters both simultaneously and individually, in accordance with haemodynamic changes associated with stress. Thirty-two feature measurements were extracted from pulse waves at three measurement sites: the brachial, radial and temporal arteries. Features which changed significantly with stress were identified using the Mann–Kendall monotonic trend test. Main results: Seventeen features exhibited significant trends with stress in measurements from at least one site. Three features showed significant trends at all three sites: the time from pulse onset to peak, the time from the dicrotic notch to pulse end, and the pulse rate. More features showed significant trends at the radial artery (15) than the brachial (8) or temporal (7) arteries. Most features were influenced by multiple input parameters. Significance: The features identified in this study could be used to monitor stress in healthcare and consumer devices. Measurements at the radial artery may provide superior performance than the brachial or temporal arteries. In vivo studies are required to confirm these observations. PMID:29658894

Development of numerical processing in children with typical and dyscalculic arithmetic skills—a longitudinal study

Science.gov (United States)

Landerl, Karin

2013-01-01

Numerical processing has been demonstrated to be closely associated with arithmetic skills, however, our knowledge on the development of the relevant cognitive mechanisms is limited. The present longitudinal study investigated the developmental trajectories of numerical processing in 42 children with age-adequate arithmetic development and 41 children with dyscalculia over a 2-year period from beginning of Grade 2, when children were 7; 6 years old, to beginning of Grade 4. A battery of numerical processing tasks (dot enumeration, non-symbolic and symbolic comparison of one- and two-digit numbers, physical comparison, number line estimation) was given five times during the study (beginning and middle of each school year). Efficiency of numerical processing was a very good indicator of development in numerical processing while within-task effects remained largely constant and showed low long-term stability before middle of Grade 3. Children with dyscalculia showed less efficient numerical processing reflected in specifically prolonged response times. Importantly, they showed consistently larger slopes for dot enumeration in the subitizing range, an untypically large compatibility effect when processing two-digit numbers, and they were consistently less accurate in placing numbers on a number line. Thus, we were able to identify parameters that can be used in future research to characterize numerical processing in typical and dyscalculic development. These parameters can also be helpful for identification of children who struggle in their numerical development. PMID:23898310

Examining pitch and numerical magnitude processing in congenital amusia: A quasi-experimental pilot study.

Science.gov (United States)

Nunes-Silva, Marilia; Moura, Ricardo; Lopes-Silva, Júlia Beatriz; Haase, Vitor Geraldi

2016-08-01

Congenital amusia is a developmental disorder associated with deficits in pitch height discrimination or in integrating pitch sequences into melodies. This quasi-experimental pilot study investigated whether there is an association between pitch and numerical processing deficits in congenital amusia. Since pitch height discrimination is considered a form of magnitude processing, we investigated whether individuals with amusia present an impairment in numerical magnitude processing, which would reflect damage to a generalized magnitude system. Alternatively, we investigated whether the numerical processing deficit would reflect a disconnection between nonsymbolic and symbolic number representations. This study was conducted with 11 adult individuals with congenital amusia and a control comparison group of 6 typically developing individuals. Participants performed nonsymbolic and symbolic magnitude comparisons and number line tasks. Results were available from previous testing using the Montreal Battery of Evaluation of Amusia (MBEA) and a pitch change detection task (PCD). Compared to the controls, individuals with amusia exhibited no significant differences in their performance on both the number line and the nonsymbolic magnitude tasks. Nevertheless, they showed significantly worse performance on the symbolic magnitude task. Moreover, individuals with congenital amusia, who presented worse performance in the Meter subtest, also presented less precise nonsymbolic numerical representation. The relationship between meter and nonsymbolic numerical discrimination could indicate a general ratio processing deficit. The finding of preserved nonsymbolic numerical magnitude discrimination and mental number line representations, with impaired symbolic number processing, in individuals with congenital amusia indicates that (a) pitch height and numerical magnitude processing may not share common neural representations, and (b) in addition to pitch processing, individuals with

Residual circulation and freshwater transport in the Dutch Wadden Sea: a numerical modelling study

NARCIS (Netherlands)

Duran-Matute, M.; Gerkema, T.; de Boer, G.J.; Nauw, J.; Grawe, U.

2014-01-01

The Dutch Wadden Sea is a region of intertidal flats located between the chain of Wadden Islands and the Dutch mainland. We present numerical model results on the tidal prisms and residual flows through the tidal inlets and across one of the main watersheds. The model also provides insight into the

Numerical Hydrodynamics in General Relativity

Directory of Open Access Journals (Sweden)

Font José A.

2003-01-01

Full Text Available The current status of numerical solutions for the equations of ideal general relativistic hydrodynamics is reviewed. With respect to an earlier version of the article, the present update provides additional information on numerical schemes, and extends the discussion of astrophysical simulations in general relativistic hydrodynamics. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A large sample of available numerical schemes is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. A comprehensive summary of astrophysical simulations in strong gravitational fields is presented. These include gravitational collapse, accretion onto black holes, and hydrodynamical evolutions of neutron stars. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances on the formulation of the gravitational field and hydrodynamic equations and the numerical methodology designed to solve them.

A numerical study of bubble interactions in Rayleigh--Taylor instability for compressible fluids

International Nuclear Information System (INIS)

Glimm, J.; Li, X.L.; Menikoff, R.; Sharp, D.H.; Zhang, Q.

1990-01-01

The late nonlinear and chaotic stage of Rayleigh--Taylor instability is characterized by the evolution of bubbles of the light fluid and spikes of the heavy fluid, each penetrating into the other phase. This paper is focused on the numerical study of bubble interactions and their effect on the statistical behavior and evolution of the bubble envelope. Compressible fluids described by the two-fluid Euler equations are considered and the front tracking method for numerical simulation of these equations is used. Two major phenomena are studied. One is the dynamics of the bubbles in a chaotic environment and the interaction among neighboring bubbles. Another one is the acceleration of the overall bubble envelope, which is a statistical consequence of the interactions of bubbles. The main result is a consistent analysis, at least in the approximately incompressible case of these two phenomena. The consistency encompasses the analysis of experiments, numerical simulation, simple theoretical models, and variation of parameters. Numerical simulation results that are in quantitative agreement with laboratory experiment for one-and-one-half (1 1/2) generations of bubble merger are presented. To the authors' knowledge, computations of this accuracy have not previously been obtained

Numerical and algebraic studies for the control of finite-dimensional quantum systems

Energy Technology Data Exchange (ETDEWEB)

Sander, Uwe

2010-11-18

In this thesis, two aspects of control theory, namely controllability and optimal control, are applied to quantum systems. The presented results are based on group theoretical techniques and numerical studies. By Lie-algebraic analysis, the controllability properties of systems with an arbitrary topology are described and related to the symmetries existing in these systems. We find that symmetry precludes full controllability. Our work investigates well-known control systems and gives rules for the design of new systems. Furthermore, theoretical and numerical concepts are instrumental to studying quantum channels: Their capacities are optimised using gradient flows on the unitary group in order to find counterexamples to a long-established additivity conjecture. The last part of this thesis presents and benchmarks a modular optimal control algorithm known as GRAPE. Numerical tests show how the interplay of its modules can be optimised for higher performance, and how the algorithm performs in comparison to a Krotov-type optimal control algorithm. It is found that GRAPE performs particularly well when aiming for high qualities. (orig.)

Numerical and algebraic studies for the control of finite-dimensional quantum systems

International Nuclear Information System (INIS)

Sander, Uwe

2010-01-01

In this thesis, two aspects of control theory, namely controllability and optimal control, are applied to quantum systems. The presented results are based on group theoretical techniques and numerical studies. By Lie-algebraic analysis, the controllability properties of systems with an arbitrary topology are described and related to the symmetries existing in these systems. We find that symmetry precludes full controllability. Our work investigates well-known control systems and gives rules for the design of new systems. Furthermore, theoretical and numerical concepts are instrumental to studying quantum channels: Their capacities are optimised using gradient flows on the unitary group in order to find counterexamples to a long-established additivity conjecture. The last part of this thesis presents and benchmarks a modular optimal control algorithm known as GRAPE. Numerical tests show how the interplay of its modules can be optimised for higher performance, and how the algorithm performs in comparison to a Krotov-type optimal control algorithm. It is found that GRAPE performs particularly well when aiming for high qualities. (orig.)

A numerical study of super-resolution through fast 3D wideband algorithm for scattering in highly-heterogeneous media

KAUST Repository

Létourneau, Pierre-David

2016-09-19

We present a wideband fast algorithm capable of accurately computing the full numerical solution of the problem of acoustic scattering of waves by multiple finite-sized bodies such as spherical scatterers in three dimensions. By full solution, we mean that no assumption (e.g. Rayleigh scattering, geometrical optics, weak scattering, Born single scattering, etc.) is necessary regarding the properties of the scatterers, their distribution or the background medium. The algorithm is also fast in the sense that it scales linearly with the number of unknowns. We use this algorithm to study the phenomenon of super-resolution in time-reversal refocusing in highly-scattering media recently observed experimentally (Lemoult et al., 2011), and provide numerical arguments towards the fact that such a phenomenon can be explained through a homogenization theory.

Numerical Study of the Ghost-Ghost-Gluon Vertex on the Lattice

International Nuclear Information System (INIS)

Mihara, A.; Cucchieri, A.; Mendes, T.

2004-01-01

It is well known that, in Landau gauge, the renormalization function of the ghost-ghost-gluon vertex Z-tilde1 (p2) is finite and constant, at least to all orders of perturbation theory. On the other hand, a direct non-perturbative verification of this result using numerical simulations of lattice QCD is still missing. Here we present a preliminary numerical study of the ghost-ghost-gluon vertex and of its corresponding renormalization function using Monte Carlo simulations in SU(2) lattice Landau gauge. Data were obtained in 4 dimensions for lattice couplings β = 2.2, 2.3, 2.4 and lattice sides N = 4, 8, 16

Numerical study of the ghost-ghost-gluon vertex on the lattice

International Nuclear Information System (INIS)

Mihara, A.; Cucchieri, A.; Mendes, T.

2004-01-01

It is well known that, in Landau gauge, the renormalization function of the ghost-ghost-gluon vertex Z∼ 1 1(p 2 ) is finite and constant, at least to all orders of perturbation theory. On the other hand, a direct non-perturbative verification of this result using numerical simulations of lattice QCD is still missing. Here we present a preliminary numerical study of the ghost-ghost-gluon vertex and of its corresponding renormalization function using Monte Carlo simulations in SU(2) lattice Landau gauge. Data were obtained in 4 dimensions for lattice couplings β= 2.2, 2.3, 2.4 and lattice sides N = 4, 8, 16. (author)

Numerical studies on the dynamics of the Northwestern Black Sea shelf

Directory of Open Access Journals (Sweden)

V. KOURAFALOU

2004-06-01

Full Text Available The Northwestern Black Sea shelf dynamics are studied with numerical simulations based on the Princeton Ocean Model. The study focus is on buoyancy and wind driven flows and on the transport and fate of low salinity waters that are introduced through riverine sources (the Danube, Dnestr and Dnepr Rivers, under the seasonal changes in atmospheric forcing. The study is part of the DANUBS project (NUtrient management in the DAnube basin and its impact on the Black Sea. The numerical simulations show that the coastal circulation is greatly influenced by river runoff and especially that of the Danube, which is dominant with monthly averaged values ranging from 5,000 m3 to 10,000 m3. The transport of low-salinity waters associated with the Danube runoff is greatly influenced by wind stress, topographic effects and basin-scale circulation patterns, such as changes in the position of the Rim Current.

Theory and applications of numerical analysis

CERN Document Server

Phillips, G M

1996-01-01

This text is a self-contained Second Edition, providing an introductory account of the main topics in numerical analysis. The book emphasizes both the theorems which show the underlying rigorous mathematics andthe algorithms which define precisely how to program the numerical methods. Both theoretical and practical examples are included.* a unique blend of theory and applications* two brand new chapters on eigenvalues and splines* inclusion of formal algorithms* numerous fully worked examples* a large number of problems, many with solutions

Numerical study of traveling-wave solutions for the Camassa-Holm equation

International Nuclear Information System (INIS)

Kalisch, Henrik; Lenells, Jonatan

2005-01-01

We explore numerically different aspects of periodic traveling-wave solutions of the Camassa-Holm equation. In particular, the time evolution of some recently found new traveling-wave solutions and the interaction of peaked and cusped waves is studied

Numerical study of interfacial flows with immersed solids

International Nuclear Information System (INIS)

Kim, Sung Il; Son, Gi Hun

2003-01-01

A numerical method is presented for computing unsteady incompressible two-phase flows with immersed solids. The method is based on a level set technique for capturing the phase interface, which is modified to satisfy a contact angle condition at the solid-fluid interface as well as to achieve mass conservation during the whole calculation procedure. The modified level set method is applied for numerical simulation of bubble deformation in a micro channel with a cylindrical solid block and liquid jet from a micro nozzle

Experimental and numerical studies of rotating drum grate furnace

Directory of Open Access Journals (Sweden)

Basista Grzegorz

2017-01-01

Full Text Available Waste material from the meat industry can be taken into account as a biofuel. Studies confirm, that calorific value is higher and ash content is lower comparing to some conventional fuels. EU directives regulate details of thermal disposal of the waste material from the meat industry - especially in range of the process temperature and time of the particle presence in area of the combustion zone. The paper describes design of the rotating drum grate stove, dedicated to thermal disposal of the meat wastes as well as solid biomass (pellet, small bricket, wood chips combustion. Device has been developed in frames of cooperation between AGH University of Science and Technology (Krakow, Poland and producer focused on technologies of energy utilization of biomass in distributed generation. Results of measurements of selected operational parameters performed during startup of the furnace have been presented and discussed. Furthermore, numerical model of the combustion process has been developed to complement experimental results in range of the temperature and oxygen distribution in the area of the combustion chamber. ANSYS CFX solver has been applied to perform simulations including rotational domain related with specifics of operation of the device. Results of numerical modelling and experimental studies have been summarized and compared.

A numerical study of adaptive space and time discretisations for Gross-Pitaevskii equations.

Science.gov (United States)

Thalhammer, Mechthild; Abhau, Jochen

2012-08-15

As a basic principle, benefits of adaptive discretisations are an improved balance between required accuracy and efficiency as well as an enhancement of the reliability of numerical computations. In this work, the capacity of locally adaptive space and time discretisations for the numerical solution of low-dimensional nonlinear Schrödinger equations is investigated. The considered model equation is related to the time-dependent Gross-Pitaevskii equation arising in the description of Bose-Einstein condensates in dilute gases. The performance of the Fourier-pseudo spectral method constrained to uniform meshes versus the locally adaptive finite element method and of higher-order exponential operator splitting methods with variable time stepsizes is studied. Numerical experiments confirm that a local time stepsize control based on a posteriori local error estimators or embedded splitting pairs, respectively, is effective in different situations with an enhancement either in efficiency or reliability. As expected, adaptive time-splitting schemes combined with fast Fourier transform techniques are favourable regarding accuracy and efficiency when applied to Gross-Pitaevskii equations with a defocusing nonlinearity and a mildly varying regular solution. However, the numerical solution of nonlinear Schrödinger equations in the semi-classical regime becomes a demanding task. Due to the highly oscillatory and nonlinear nature of the problem, the spatial mesh size and the time increments need to be of the size of the decisive parameter [Formula: see text], especially when it is desired to capture correctly the quantitative behaviour of the wave function itself. The required high resolution in space constricts the feasibility of numerical computations for both, the Fourier pseudo-spectral and the finite element method. Nevertheless, for smaller parameter values locally adaptive time discretisations facilitate to determine the time stepsizes sufficiently small in order that

Numerical and experimental characterization of a batch bread baking oven

International Nuclear Information System (INIS)

Ploteau, J.P.; Nicolas, V.; Glouannec, P.

2012-01-01

This study deals with the thermal characterization of an electrical static oven used for bread baking. The heating is provided by natural convection, infrared radiation and conduction with a cement slab. The paper describes a methodology to apprehend the heat flux which is applied to the products during baking. The oven was experimentally investigated and a finite element numerical model is established. The monitoring of temperatures at various points in the installation and of electrical power is carried out. Then, to characterize thermal exchanges around the bread during curing, thermal responses of a cylindrical sample is also measured. The numerical model made it possible to calculate the heat flux exchanges with the product, while separating the contributions of convection and radiation. The comparison of simulated responses with experimental data shows the relevance of the model. - Highlights: ► This study concerns the thermal characterization of an electric static oven used for bread baking. ► An original, experimental and numerical approach of thermal problem is proposed. ► Contributions by radiation and convection are separated. ► The goal is to provide boundary conditions for numerical models of bread baking. ► Results are encouraging to optimize energy consumption in industrial oven.

A numerical study of granular dam-break flow

Science.gov (United States)

Pophet, N.; Rébillout, L.; Ozeren, Y.; Altinakar, M.

2017-12-01

Accurate prediction of granular flow behavior is essential to optimize mitigation measures for hazardous natural granular flows such as landslides, debris flows and tailings-dam break flows. So far, most successful models for these types of flows focus on either pure granular flows or flows of saturated grain-fluid mixtures by employing a constant friction model or more complex rheological models. These saturated models often produce non-physical result when they are applied to simulate flows of partially saturated mixtures. Therefore, more advanced models are needed. A numerical model was developed for granular flow employing a constant friction and μ(I) rheology (Jop et al., J. Fluid Mech. 2005) coupled with a groundwater flow model for seepage flow. The granular flow is simulated by solving a mixture model using Finite Volume Method (FVM). The Volume-of-Fluid (VOF) technique is used to capture the free surface motion. The constant friction and μ(I) rheological models are incorporated in the mixture model. The seepage flow is modeled by solving Richards equation. A framework is developed to couple these two solvers in OpenFOAM. The model was validated and tested by reproducing laboratory experiments of partially and fully channelized dam-break flows of dry and initially saturated granular material. To obtain appropriate parameters for rheological models, a series of simulations with different sets of rheological parameters is performed. The simulation results obtained from constant friction and μ(I) rheological models are compared with laboratory experiments for granular free surface interface, front position and velocity field during the flows. The numerical predictions indicate that the proposed model is promising in predicting dynamics of the flow and deposition process. The proposed model may provide more reliable insight than the previous assumed saturated mixture model, when saturated and partially saturated portions of granular mixture co-exist.

Numerical Study on Deflection Behaviour of Concrete Beams Reinforced with GFRP Bars

Science.gov (United States)

Mohamed, Osama A.; Khattab, Rania; Hawat, Waddah Al

2017-10-01

Fiber-Reinforced Polymer (FRP) bars are gaining popularity as sustainable alternatives to conventional reinforcing steel bars in reinforced concrete applications. The production of FRP bars has lower environmental impact compared to steel reinforcing bars. In addition, the non-corroding FRP materials can potentially decrease the cost or need for maintenance of reinforced concrete structural elements, especially in harsh environmental conditions that can impact both concrete and reinforcement. FRP bars offer additional favourable properties including high tensile strength and low unit weight. However, the mechanical properties of FRP bars can lead to large crack widths and deflections. The objective of this study is to investigate the deflection behaviour of concrete beams reinforced with Glass FRP (GFRP) bars as a longitudinal main reinforcement. Six concrete beams reinforced with GFRP bars were modelled using the finite element computer program ANSYS. The main variable considered in the study is the reinforcement ratio. The deflection equations in current North American codes including ACI 440.1R-06, ACI 440.1R-15 and CSA S806-12 are used to compute deflections, and these are compared to numerical results. It was concluded in this paper that deflections predicted by ACI 440.1R-06 equations are lower than the numerical analysis results while ACI 440.1R-15 is in agreement with numerical analysis with tendency to be conservative. The values of deflections estimated by CSA S806-12 formulas are consistent with results of numerical analysis.

Proceeding of 1998-workshop on MHD computations. Study on numerical methods related to plasma confinement

International Nuclear Information System (INIS)

Kako, T.; Watanabe, T.

1999-04-01

This is the proceeding of 'Study on Numerical Methods Related to Plasma Confinement' held in National Institute for Fusion Science. In this workshop, theoretical and numerical analyses of possible plasma equilibria with their stability properties are presented. These are also various talks on mathematical as well as numerical analyses related to the computational methods for fluid dynamics and plasma physics. The 14 papers are indexed individually. (J.P.N.)

Proceeding of 1998-workshop on MHD computations. Study on numerical methods related to plasma confinement

Energy Technology Data Exchange (ETDEWEB)

Kako, T.; Watanabe, T. [eds.

1999-04-01

This is the proceeding of 'Study on Numerical Methods Related to Plasma Confinement' held in National Institute for Fusion Science. In this workshop, theoretical and numerical analyses of possible plasma equilibria with their stability properties are presented. These are also various talks on mathematical as well as numerical analyses related to the computational methods for fluid dynamics and plasma physics. The 14 papers are indexed individually. (J.P.N.)

A numerical study of adaptive space and time discretisations for Gross–Pitaevskii equations

Science.gov (United States)

Thalhammer, Mechthild; Abhau, Jochen

2012-01-01

As a basic principle, benefits of adaptive discretisations are an improved balance between required accuracy and efficiency as well as an enhancement of the reliability of numerical computations. In this work, the capacity of locally adaptive space and time discretisations for the numerical solution of low-dimensional nonlinear Schrödinger equations is investigated. The considered model equation is related to the time-dependent Gross–Pitaevskii equation arising in the description of Bose–Einstein condensates in dilute gases. The performance of the Fourier-pseudo spectral method constrained to uniform meshes versus the locally adaptive finite element method and of higher-order exponential operator splitting methods with variable time stepsizes is studied. Numerical experiments confirm that a local time stepsize control based on a posteriori local error estimators or embedded splitting pairs, respectively, is effective in different situations with an enhancement either in efficiency or reliability. As expected, adaptive time-splitting schemes combined with fast Fourier transform techniques are favourable regarding accuracy and efficiency when applied to Gross–Pitaevskii equations with a defocusing nonlinearity and a mildly varying regular solution. However, the numerical solution of nonlinear Schrödinger equations in the semi-classical regime becomes a demanding task. Due to the highly oscillatory and nonlinear nature of the problem, the spatial mesh size and the time increments need to be of the size of the decisive parameter 0Fourier pseudo-spectral and the finite element method. Nevertheless, for smaller parameter values locally adaptive time discretisations facilitate to determine the time stepsizes sufficiently small in order that the numerical approximation captures correctly the behaviour of the analytical solution. Further illustrations for Gross–Pitaevskii equations with a focusing nonlinearity or a sharp Gaussian as initial condition, respectively

Role of vegetation in formation of radiation fog: A numerical study

Czech Academy of Sciences Publication Activity Database

Potužníková, Kateřina; Sedlák, Pavel

2004-01-01

Roč. 23, Suppl. 2 (2004), s. 39-45 ISSN 1335-342X Institutional research plan: CEZ:AV0Z3042911 Keywords : radiation fog * vegetation cover * numerical study Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.078, year: 2004

Numerical Study of Corrosion Crack Opening

DEFF Research Database (Denmark)

Thoft-Christensen, Palle; Frandsen, Henrik Lund; Svensson, Staffan

2008-01-01

is proportional. More recently, the constant of proportionality, the so-called crack-corrosion index, has been studied further with respect to its dependence on the diameter of the reinforcement and the concrete cover. In the present paper the above-mentioned work is presented and extended with more realistic 3D......-models of the cracked concrete beam. The crack-corrosion index is evaluated for a variation of different parameters, i.e. bar diameter, concrete cover, crack length and type of corrosion product. This paper is an extended version of a paper by Thoft-Christensen et al. (2005) presented at the IFIP WG 7.5 Conference...... for the corrosion crack opening. Experiments and theoretical analysis by a numerical method, FEM, support that the relation between the reduction of the reinforcement bar diameter due to corrosion and the corresponding increase in crack width for a given time interval, measured on the surface of a concrete specimen...

Numerical linear algebra theory and applications

CERN Document Server

Beilina, Larisa; Karchevskii, Mikhail

2017-01-01

This book combines a solid theoretical background in linear algebra with practical algorithms for numerical solution of linear algebra problems. Developed from a number of courses taught repeatedly by the authors, the material covers topics like matrix algebra, theory for linear systems of equations, spectral theory, vector and matrix norms combined with main direct and iterative numerical methods, least squares problems, and eigen problems. Numerical algorithms illustrated by computer programs written in MATLAB® are also provided as supplementary material on SpringerLink to give the reader a better understanding of professional numerical software for the solution of real-life problems. Perfect for a one- or two-semester course on numerical linear algebra, matrix computation, and large sparse matrices, this text will interest students at the advanced undergraduate or graduate level.

Experimental and numerical study of waste heat recovery characteristics of direct contact thermoelectric generator

International Nuclear Information System (INIS)

Kim, Tae Young; Negash, Assmelash; Cho, Gyubaek

2017-01-01

Highlights: • Energy harvesting performance of direct contact thermoelectric generator was studied. • Power-current and voltage-current curves were given for various operating conditions. • Output power prediction using numerical results and empirical correlation was verified. • A 1.0–2.0% conversion efficiency and 5.7–11.1% heat recovery efficiency were obtained. • A 0.25% increase in efficiency was found with a 10 K decrease in coolant temperature. - Abstract: In this study, waste heat recovery performance of a direct contact thermoelectric generator (DCTEG) is experimentally investigated on a diesel engine. In order to conduct an insightful analysis of the DCTEG characteristics, three experimental parameters—engine load, rotation speed, and coolant temperature—are chosen to vary over ranges during the experiments. Experimental results show that higher temperature differences across thermoelectric modules (TEM), larger engine loads, and rotation speeds lead to an improved energy conversion efficiency of the DCTEG, which lies in the range of approximately 1.0–2.0%, while the output power ranges approximately 12–45 W. The increase in the conversion efficiency for an increased engine load becomes more noticeable with a higher engine rotation speed. A 10 K decrease in the coolant temperature yields an approximately 0.25% increase in the conversion efficiency for the engine operating conditions tested. In addition, 3D numerical simulations were conducted to investigate the heat transfer and pressure characteristics of the DCTEG. Numerically obtained exhaust gas temperatures exiting the DCTEG were in good agreement with experimental results. It is also revealed that incorporation of the temperature fields from the numerical simulation and an empirical correlation for a temperature-power relationship provides a good predictor for output power from the DCTEG, especially at low engine load conditions, which deviates from experimental results as the

Contribution to the theoretical and numerical study of inertial confinement fusion

International Nuclear Information System (INIS)

Tran Trach-Minh

1983-01-01

After an overview of problems faced for numerical simulations of inertial fusion, this research thesis reports the study of the behaviour of suprathermal ions by using the transport equation as model. The problem is then to find an appropriate numerical method to solve this equation, inspired by well known methods related to the transport of neutral particles (photons and neutrons) which however cannot be directly applied. The calculation scheme is introduced in an existing hydrodynamic code. Models are then proposed to take the partial ionisation of some materials into account in the target thermodynamics and in the slowing down of fast ions. In the next part, the author discusses the ion transport equation, and the calculation of the different coefficients which characterise their interaction with particles of the host medium. Problems faced for numerical processing are addressed. The coupling of ion transport calculation model with a hydrodynamic code is described. Effects of alphas transport during target ignition are analysed, as well as the penetration of external ion beams during the compression phase

Microfluidic emulsification at cross-junction: experimental and numerical study using Blue

Science.gov (United States)

Roumpea, Evangelia; Kovalchuk, Nina M.; Kahouadji, Lyes; Xie, Zhihua; Chinaud, Maxime; Simmons, Mark J. H.; Matar, Omar K.; Angeli, Panagiota

2017-11-01

Liquid-liquid drop formation in a cross-junction device is investigated both experimentally and numerically. Experiments are performed using 5 cSt silicone oil as the continuous phase and 52% glycerol/ 48% water mixture containing surfactants as the dispersed phase. Both a high-speed camera and a two-colour micro-PIV technique were used to obtain the different flow regimes i.e. squeezing, dripping, jetting and threading and to study the velocity fields of the two phases simultaneously. The dependence of the drop size on flow rate follows a power law with different exponents for small and large drops. Numerical simulations using the code Blue, a massive parallel solver for simulations of fully three-dimensional multiphase flows, were also performed taking into account the properties of the liquids used in the experiments and the precise geometry of the microfluidic chips. The simulation results agreed very well with the surfactant-free solution. The numerical simulations taking into account the surfactant are ongoing. EPSRC, UK, MEMPHIS program Grant (EP/K003976/1), RAEng Research Chair (OKM).

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

Sensitivity of a numerical wave model on wind re-analysis datasets

Science.gov (United States)

Lavidas, George; Venugopal, Vengatesan; Friedrich, Daniel

2017-03-01

Wind is the dominant process for wave generation. Detailed evaluation of metocean conditions strengthens our understanding of issues concerning potential offshore applications. However, the scarcity of buoys and high cost of monitoring systems pose a barrier to properly defining offshore conditions. Through use of numerical wave models, metocean conditions can be hindcasted and forecasted providing reliable characterisations. This study reports the sensitivity of wind inputs on a numerical wave model for the Scottish region. Two re-analysis wind datasets with different spatio-temporal characteristics are used, the ERA-Interim Re-Analysis and the CFSR-NCEP Re-Analysis dataset. Different wind products alter results, affecting the accuracy obtained. The scope of this study is to assess different available wind databases and provide information concerning the most appropriate wind dataset for the specific region, based on temporal, spatial and geographic terms for wave modelling and offshore applications. Both wind input datasets delivered results from the numerical wave model with good correlation. Wave results by the 1-h dataset have higher peaks and lower biases, in expense of a high scatter index. On the other hand, the 6-h dataset has lower scatter but higher biases. The study shows how wind dataset affects the numerical wave modelling performance, and that depending on location and study needs, different wind inputs should be considered.

Numerical study of thermoviscous effects in ultrasound-induced acoustic streaming in microchannels

DEFF Research Database (Denmark)

Muller, Peter Barkholt; Bruus, Henrik

2014-01-01

We present a numerical study of thermoviscous effects on the acoustic streaming flow generated by an ultrasound standing-wave resonance in a long straight microfluidic channel containing a Newtonian fluid. These effects enter primarily through the temperature and density dependence of the fluid...... viscosity. The resulting magnitude of the streaming flow is calculated and characterized numerically, and we find that even for thin acoustic boundary layers, the channel height affects the magnitude of the streaming flow. For the special case of a sufficiently large channel height, we have successfully...

Particle Shape Effect on Macroscopic Behaviour of Underground Structures: Numerical and Experimental Study

Directory of Open Access Journals (Sweden)

Szarf Krzysztof

2015-02-01

Full Text Available The mechanical performance of underground flexible structures such as buried pipes or culverts made of plastics depend not only on the properties of the structure, but also on the material surrounding it. Flexible drains can deflect by 30% with the joints staying tight, or even invert. Large deformations of the structure are difficult to model in the framework of Finite Element Method, but straightforward in Discrete Element Methods. Moreover, Discrete Element approach is able to provide information about the grain-grain and grain-structure interactions at the microscale. This paper presents numerical and experimental investigations of flexible buried pipe behaviour with focus placed on load transfer above the buried structure. Numerical modeling was able to reproduce the experimental results. Load repartition was observed, being affected by a number of factors such as particle shape, pipe friction and pipe stiffness.

Numerical Study on Density Gradient Carbon-Carbon Composite for Vertical Launching System

Science.gov (United States)

Yoon, Jin-Young; Kim, Chun-Gon; Lim, Juhwan

2018-04-01

This study presents new carbon-carbon (C/C) composite that has a density gradient within single material, and estimates its heat conduction performance by a numerical method. To address the high heat conduction of a high-density C/C, which can cause adhesion separation in the steel structures of vertical launching systems, density gradient carbon-carbon (DGCC) composite is proposed due to its exhibiting low thermal conductivity as well as excellent ablative resistance. DGCC is manufactured by hybridizing two different carbonization processes into a single carbon preform. One part exhibits a low density using phenolic resin carbonization to reduce heat conduction, and the other exhibits a high density using thermal gradient-chemical vapor infiltration for excellent ablative resistance. Numerical analysis for DGCC is performed with a heat conduction problem, and internal temperature distributions are estimated by the forward finite difference method. Material properties of the transition density layer, which is inevitably formed during DGCC manufacturing, are assumed to a combination of two density layers for numerical analysis. By comparing numerical results with experimental data, we validate that DGCC exhibits a low thermal conductivity, and it can serve as highly effective ablative material for vertical launching systems.

Numerical studies of QCD renormalons in high-order perturbative expansions

International Nuclear Information System (INIS)

Bauer, Clemens

2013-01-01

Perturbative expansions in four-dimensional non-Abelian gauge theories such as Quantum Chromodynamics (QCD) are expected to be divergent, at best asymptotic. One reason is that it is impossible to strictly exclude from the relevant Feynman diagrams those energy regions in which a perturbative treatment is inapplicable. The divergent nature of the series is then signaled by a rapid (factorial) growth of the perturbative expansion coefficients, commonly referred to as a renormalon. In QCD, the most severe divergences occur in the infrared (IR) limit and therefore they are classified as IR renormalons. Their appearance can be understood within the well-accepted Operator Product Expansion (OPE) framework. According to the OPE, the perturbative calculation of a physical observable must be amended by non-perturbative power corrections that come in the form of condensates, universal characteristics of the rich QCD vacuum structure. Adding up perturbative and non-perturbative contributions, the ambiguity due to the renormalon cancels and the physical observable is well-defined. Although the field has made considerable progress in the last twenty years, a proof of renormalon existence is still pending. It has only been tested assuming strong simplifications or in toy models. The aim of this thesis is to provide the first numerical evidence for renormalon existence in the gauge sector of QCD. We use Numerical Stochastic Perturbation Theory (NSPT) to directly obtain perturbative coefficients within lattice regularization, a means to replace continuum spacetime by a four-dimensional hypercubic lattice. A peculiar feature of NSPT are comparatively low simulation costs when reaching high expansion orders. We examine two distinct observables: the static self-energy of an isolated quark and the elementary plaquette. Following the OPE classification, the static quark self-energy is ideally suited for a renormalon study. Taking into account peculiarities of the lattice approach such

Numerical study of two-dimensional moist symmetric instability

Directory of Open Access Journals (Sweden)

M. Fantini

2008-06-01

Full Text Available The 2-D version of the non-hydrostatic fully compressible model MOLOCH developed at ISAC-CNR was used in idealized set-up to study the start-up and finite amplitude evolution of symmetric instability. The unstable basic state was designed by numerical integration of the equation which defines saturated equivalent potential vorticity q_e^*. We present the structure and growth rates of the linear modes both for a supersaturated initial state ("super"-linear mode and for a saturated one ("pseudo"-linear mode and the modifications induced on the base state by their finite amplitude evolution.

Numerical Verification Of Equilibrium Chemistry

International Nuclear Information System (INIS)

Piro, Markus; Lewis, Brent; Thompson, William T.; Simunovic, Srdjan; Besmann, Theodore M.

2010-01-01

A numerical tool is in an advanced state of development to compute the equilibrium compositions of phases and their proportions in multi-component systems of importance to the nuclear industry. The resulting software is being conceived for direct integration into large multi-physics fuel performance codes, particularly for providing boundary conditions in heat and mass transport modules. However, any numerical errors produced in equilibrium chemistry computations will be propagated in subsequent heat and mass transport calculations, thus falsely predicting nuclear fuel behaviour. The necessity for a reliable method to numerically verify chemical equilibrium computations is emphasized by the requirement to handle the very large number of elements necessary to capture the entire fission product inventory. A simple, reliable and comprehensive numerical verification method is presented which can be invoked by any equilibrium chemistry solver for quality assurance purposes.

Numerical calculations on heterogeneity of groundwater flow

International Nuclear Information System (INIS)

Follin, S.

1992-01-01

The upscaling of model parameters is a key issue in many research fields concerned with parameter heterogeneity. The upscaling process allows for fewer model blocks and relaxes the numerical problems caused by high contrasts in the hydraulic conductivity. The trade-offs are dependent on the object but the general drawback is an increasing uncertainty about the representativeness. The present study deals with numerical calculations of heterogeneity of groundwater flow and solute transport in hypothetical blocks of fractured hard rock in a '3m scale' and addresses both conceptual and practical problems in numerical simulation. Evidence that the hydraulic conductivity (K) of the rock mass between major fracture zones is highly heterogeneous in a 3m scale is provided by a large number of field investigations. The present uses the documented heterogeneity and investigates flow and transport in a two-dimensional stochastic continuum characterized by a variance in Y = In(K) of σ y 2 = 16, corresponding to about 12 log 10 cycles in K. The study considers anisotropy, channelling, non-Fickian and Fickian transport, and conditional simulation. The major conclusions are: * heterogeneity gives rise to anisotropy in the upscaling process, * the choice of support scale is crucial for the modelling of solute transport. As a consequence of the obtained results, a two-dimensional stochastic discontinuum model is presented, which provides a tool for linking stochastic continuum models to discrete fracture network models. (au) (14 figs., 136 refs.)

Effect of object functions on tomographic reconstruction a numerical study

International Nuclear Information System (INIS)

Babu Rao, C.; Baldev Raj; Ravichandran, V.S.; Munshi, P.

1996-01-01

Convolution back projection is the most widely used algorithm of computed tomography (CT). Theoretical studies show that under ideal conditions, the error in the reconstruction can be correlated with the second fourier space derivative of filter function and with the Laplacian of the object function. This paper looks into the second aspect of the error function. In this paper a systematic numerical study is presented on the effect to object functions on global and local errors. (author)

Approximate numerical abilities and mathematics: Insight from correlational and experimental training studies.

Science.gov (United States)

Hyde, D C; Berteletti, I; Mou, Y

2016-01-01

Humans have the ability to nonverbally represent the approximate numerosity of sets of objects. The cognitive system that supports this ability, often referred to as the approximate number system (ANS), is present in early infancy and continues to develop in precision over the life span. It has been proposed that the ANS forms a foundation for uniquely human symbolic number and mathematics learning. Recent work has brought two types of evidence to bear on the relationship between the ANS and human mathematics: correlational studies showing individual differences in approximate numerical abilities correlate with individual differences in mathematics achievement and experimental studies showing enhancing effects of nonsymbolic approximate numerical training on exact, symbolic mathematical abilities. From this work, at least two accounts can be derived from these empirical data. It may be the case that the ANS and mathematics are related because the cognitive and brain processes responsible for representing numerical quantity in each format overlap, the Representational Overlap Hypothesis, or because of commonalities in the cognitive operations involved in mentally manipulating the representations of each format, the Operational Overlap hypothesis. The two hypotheses make distinct predictions for future work to test. © 2016 Elsevier B.V. All rights reserved.

Numerical study on boiling heat transfer enhancement in a microchannel heat exchanger

International Nuclear Information System (INIS)

Jeon, Jin Ho; Suh, Young Ho; Son, Gi Hun

2008-01-01

Flow boiling in a microchannel heat exchanger has received attention as an effective heat removal mechanism for high power-density microelectronics. Despite extensive experimental studied, the bubble dynamics coupled with boiling heat transfer in a microchannel heat exchanger is still not well understood due to the technological difficulties in obtaining detailed measurements of microscale two-phase flows. In this study, complete numerical simulations are performed to further clarify the dynamics of flow boiling in a microchannel heat exchanger. The level set method for tracking the liquid-vapor interface is modified to include the effects of phase change and contact angle and to treat an immersed solid surface. Based on the numerical results, the effects of modified channel shape on the bubble growth and heat transfer are quantified

Numerical and experimental study of blowing jet on a high lift airfoil

Science.gov (United States)

Bobonea, A.; Pricop, M. V.

2013-10-01

Active manipulation of separated flows over airfoils at moderate and high angles of attack in order to improve efficiency or performance has been the focus of a number of numerical and experimental investigations for many years. One of the main methods used in active flow control is the usage of blowing devices with constant and pulsed blowing. Through CFD simulation over a 2D high-lift airfoil, this study is trying to highlight the impact of pulsed blowing over its aerodynamic characteristics. The available wind tunnel data from INCAS low speed facility are also beneficial for the validation of the numerical analysis. This study intends to analyze the impact of the blowing jet velocity and slot geometry on the efficiency of an active flow control.

Study of natural convection heat transfer characteristics. (2) Verification for numerical simulation

International Nuclear Information System (INIS)

Ikeda, Hiroshi; Nakada, Kotaro; Ikeda, Tatsumi; Wakamatsu, Mitsuo; Iwaki, Chikako; Morooka, Shinichi; Masaki, Yoshikazu

2008-01-01

In the natural cooling system for waste storage, it is important to evaluate the flow by natural draft enough to remove the decay heat from the waste. In this study, we carried out the fundamental study of natural convection on vertical cylindrical heater by experiment and numerical simulation. The dimension of test facility is about 4m heights with single heater. Heating power is varied in the range of 33-110W, where Rayleigh number is over 10 10 . We surveyed the velocity distribution around heater by some turbulent models, mesh sizes around heated wall and turbulent Prandtl numbers. Results of numerical simulation of the velocity distribution and averaged heat transfer coefficient agreed well with experimental data and references. (author)

The analytical and numerical study of the fluorination of uranium dioxide particles

International Nuclear Information System (INIS)

Sazhin, S.S.

1997-01-01

A detailed analytical study of the equations describing the fluorination of UO 2 particles is presented for some limiting cases assuming that the mass flowrate of these particles is so small that they do not affect the state of the gas. The analytical solutions obtained can be used for approximate estimates of the effect of fluorination on particle diameter and temperature but their major application, however, is probably in the verification of self-consistent numerical solutions. Computational results are presented and discussed for a self-consistent problem in which both the effects of gas on particles and particles on gas are accounted for. It has been shown that in the limiting cases for which analytical solutions have been obtained, the coincidence between numerical and analytical results is almost exact. This can be considered as a verification of both the analytical and numerical solutions. (orig.)

Beach steepness effects on nonlinear infragravity-wave interactions : A numerical study

NARCIS (Netherlands)

de Bakker, A. T M; Tissier, M. F S; Ruessink, B. G.

2016-01-01

The numerical model SWASH is used to investigate nonlinear energy transfers between waves for a diverse set of beach profiles and wave conditions, with a specific focus on infragravity waves. We use bispectral analysis to study the nonlinear triad interactions, and estimate energy transfers to

Numerical study of particle filtration in an induction crucible furnace

International Nuclear Information System (INIS)

Asad, Amjad; Kratzsch, Christoph; Dudczig, Steffen; Aneziris, Christos G.; Schwarze, Rüdiger

2016-01-01

Highlights: • Removing particles from a melt in an induction furnace by using a filter is introduced. • The effect of filter and its permeability on the melt flow is shown. • The impact of filter permeability and particle diameter on filter efficiency is studied. • The filter efficiency depends on filter position and number of the used filter. - Abstract: The present paper deals with a numerical investigation of the turbulent melt flow driven by the electromagnetic force in an induction furnace. The main scope of the paper is to present a new principle to remove non-metallic particles from steel melt in an induction furnace by immersing a porous filter in the melt. The magnetic field acting on the melt is calculated by using the open source software MaxFEM"®, while the turbulent flow is simulated by means of the open source computational fluid dynamics library OpenFOAM"®. The validation of the numerical model is accomplished by using experimental results for the flow without the immersed filter. Here it is shown that the time-averaged flow, obtained numerically is in a good quantitive agreement with the experimental data. Then, the validated numerical model is employed to simulate the melt flow with the immersed filter in the induction furnace of a new type of real steel casting simulator investigated at Technische Universität Bergakademie Freiberg. The considerable effect of the filter on the flow pattern is indicated in the present work. Moreover, it is shown that the filter permeability and its position have a significant influence on the melt flow in the induction furnace. Additionally, particles are injected in the flow domain and tracked by using Lagrangian framework. In this case, the efficiency of the used filter is determined in the present investigation depending on its permeability, its position and the particles diameter.

Numerical methods using Matlab

CERN Document Server

Lindfield, George

2012-01-01

Numerical Methods using MATLAB, 3e, is an extensive reference offering hundreds of useful and important numerical algorithms that can be implemented into MATLAB for a graphical interpretation to help researchers analyze a particular outcome. Many worked examples are given together with exercises and solutions to illustrate how numerical methods can be used to study problems that have applications in the biosciences, chaos, optimization, engineering and science across the board. Numerical Methods using MATLAB, 3e, is an extensive reference offering hundreds of use

Conservative numerical methods for solitary wave interactions

Energy Technology Data Exchange (ETDEWEB)

Duran, A; Lopez-Marcos, M A [Departamento de Matematica Aplicada y Computacion, Facultad de Ciencias, Universidad de Valladolid, Paseo del Prado de la Magdalena s/n, 47005 Valladolid (Spain)

2003-07-18

The purpose of this paper is to show the advantages that represent the use of numerical methods that preserve invariant quantities in the study of solitary wave interactions for the regularized long wave equation. It is shown that the so-called conservative methods are more appropriate to study the phenomenon and provide a dynamic point of view that allows us to estimate the changes in the parameters of the solitary waves after the collision.

A Numerical Study for Robust Active Portfolio Management with Worst-Case Downside Risk Measure

Directory of Open Access Journals (Sweden)

Aifan Ling

2014-01-01

Full Text Available Recently, active portfolio management problems are paid close attention by many researchers due to the explosion of fund industries. We consider a numerical study of a robust active portfolio selection model with downside risk and multiple weights constraints in this paper. We compare the numerical performance of solutions with the classical mean-variance tracking error model and the naive 1/N portfolio strategy by real market data from China market and other markets. We find from the numerical results that the tested active models are more attractive and robust than the compared models.

Analytical and Numerical Studies of Several Fluid Mechanical Problems

Science.gov (United States)

Kong, D. L.

2014-03-01

In this thesis, three parts, each with several chapters, are respectively devoted to hydrostatic, viscous, and inertial fluids theories and applications. Involved topics include planetary, biological fluid systems, and high performance computing technology. In the hydrostatics part, the classical Maclaurin spheroids theory is generalized, for the first time, to a more realistic multi-layer model, establishing geometries of both the outer surface and the interfaces. For one of its astrophysical applications, the theory explicitly predicts physical shapes of surface and core-mantle-boundary for layered terrestrial planets, which enables the studies of some gravity problems, and the direct numerical simulations of dynamo flows in rotating planetary cores. As another application of the figure theory, the zonal flow in the deep atmosphere of Jupiter is investigated for a better understanding of the Jovian gravity field. An upper bound of gravity field distortions, especially in higher-order zonal gravitational coefficients, induced by deep zonal winds is estimated firstly. The oblate spheroidal shape of an undistorted Jupiter resulting from its fast solid body rotation is fully taken into account, which marks the most significant improvement from previous approximation based Jovian wind theories. High viscosity flows, for example Stokes flows, occur in a lot of processes involving low-speed motions in fluids. Microorganism swimming is such a typical case. A fully three dimensional analytic solution of incompressible Stokes equation is derived in the exterior domain of an arbitrarily translating and rotating prolate spheroid, which models a large family of microorganisms such as cocci bacteria. The solution is then applied to the magnetotactic bacteria swimming problem, and good consistency has been found between theoretical predictions and laboratory observations of the moving patterns of such bacteria under magnetic fields. In the analysis of dynamics of planetary

The Numerical Study on the Influence of Prandtl Number and Height of the Enclosure

International Nuclear Information System (INIS)

Moon, Je-Young; Chung, Bum-Jin

2016-01-01

This study investigated numerically the internal flow depending on Prandtl number of fluid and height of enclosure. The two-dimensional numerical simulations were performed for several heights of enclosure in the range between 0.01 m and 0.074 m. It corresponds to the aspect ratio (H/L) ranged from 0.07 to 0.5. Prandtl number was 0.2, 0.7 and 7. Rayleigh number based on the height of enclosure ranged between 8.49x10 3 and 1.20x10 8 . The numerical calculations were carried out using FLUENT 6.3. In order to confirm the influence of Prandtl number and height of side walls on the internal flow and heat transfer of the horizontal enclosure, the numerical study is carried out using the FLUENT 6.3. The numerical results for the condition of top cooling only agree well with Rayleigh-Benard natural convection. When the top and side walls were cooled, the internal flow of enclosure is more complex. The thickness of thermal and velocity boundary layer varies with Prandtl number. For Pr>1 the behavior of cells is unstable and irregular owing to the entrained plume, whereas the internal flow for Pr<1 is stable and regular. Also, the number of cells increases depending on decrease of height. As a result, the heat exchange increases

Mathematical and numerical foundations of turbulence models and applications

CERN Document Server

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 studies of the influence of food ingestion on phytoplankton and zooplankton biomasses

OpenAIRE

Lidia Dzierzbicka-G³owacka

2002-01-01

This paper presents the numerical simulations of the influence of food ingestion by a herbivorous copepod on phytoplankton and zooplankton biomasses (PZB) in the sea. The numerical studies were carried out using the phytoplankton-zooplankton-nutrient-detritus PhyZooNuDe biological upper layer model. This takes account both of fully developed primary production and regeneration mechanisms and of daily migration of zooplankton. In this model the zooplankton is treated not as a 'biomass' but as ...

Numerical Simulation of Hydro-mechanical Deep Drawing — A Study on the Effect of Process Parameters on Drawability and Thickness Variation

Science.gov (United States)

Singh, Swadesh Kumar; Kumar, D. Ravi

2005-08-01

Hydro-mechanical deep drawing is a process for producing cup shaped parts with the assistance of a pressurized fluid. In the present work, numerical simulation of the conventional and counter pressure deep drawing processes has been done with the help of a finite element method based software. Simulation results were analyzed to study the improvement in drawability by using hydro-mechanical processes. The thickness variations in the drawn cups were analyzed and also the effect of counter pressure and oil gap on the thickness distribution was studied. Numerical simulations were also used for the die design, which combines both drawing and ironing processes in a single operation. This modification in the die provides high drawability, facilitates smooth material flow, gives more uniform thickness distribution and corrects the shape distortion.

A mathematical and numerical analysis of the Maxwell-Stefan diffusion equations

OpenAIRE

Boudin , Laurent; Grec , Bérénice; Salvarani , Francesco

2012-01-01

International audience; We consider the Maxwell-Stefan model of diffusion in a multicomponent gaseous mixture. After focusing on the main differences with the Fickian diffusion model, we study the equations governing a three-component gas mixture. We provide a qualitative and quantitative mathematical analysis of the model. The main properties of the standard explicit numerical scheme are also analyzed. We eventually include some numerical simulations pointing out the uphill diffusion phenome...

Infragravity-wave dynamics in a barred coastal region, a numerical study

NARCIS (Netherlands)

Rijnsdorp, Dirk P.; Ruessink, Gerben; Zijlema, Marcel

2015-01-01

This paper presents a comprehensive numerical study into the infragravity-wave dynamics at a field site, characterized by a gently sloping barred beach. The nonhydrostatic wave-flow model SWASH was used to simulate the local wavefield for a range of wave conditions (including mild and storm

Beach steepness effects on nonlinear infragravity-wave interactions : A numerical study

NARCIS (Netherlands)

De Bakker, A. T M; Tissier, M.F.S.; Ruessink, B. G.

2016-01-01

The numerical model SWASH is used to investigate nonlinear energy transfers between waves for a diverse set of beach profiles and wave conditions, with a specific focus on infragravity waves. We use bispectral analysis to study the nonlinear triad interactions, and estimate energy transfers to

A Combined Experimental and Numerical Modeling Study of the Deformation and Rupture of Axisymmetric Liquid Bridges under Coaxial Stretching.

Science.gov (United States)

Zhuang, Jinda; Ju, Y Sungtaek

2015-09-22

The deformation and rupture of axisymmetric liquid bridges being stretched between two fully wetted coaxial disks are studied experimentally and theoretically. We numerically solve the time-dependent Navier-Stokes equations while tracking the deformation of the liquid-air interface using the arbitrary Lagrangian-Eulerian (ALE) moving mesh method to fully account for the effects of inertia and viscous forces on bridge dynamics. The effects of the stretching velocity, liquid properties, and liquid volume on the dynamics of liquid bridges are systematically investigated to provide direct experimental validation of our numerical model for stretching velocities as high as 3 m/s. The Ohnesorge number (Oh) of liquid bridges is a primary factor governing the dynamics of liquid bridge rupture, especially the dependence of the rupture distance on the stretching velocity. The rupture distance generally increases with the stretching velocity, far in excess of the static stability limit. For bridges with low Ohnesorge numbers, however, the rupture distance stay nearly constant or decreases with the stretching velocity within certain velocity windows due to the relative rupture position switching and the thread shape change. Our work provides an experimentally validated modeling approach and experimental data to help establish foundation for systematic further studies and applications of liquid bridges.

Development of numerical processing in children with typical and dyscalculic arithmetic skills – a longitudinal study

Directory of Open Access Journals (Sweden)

Karin eLanderl

2013-07-01

Full Text Available Numerical processing has been demonstrated to be closely associated with arithmetic skills, however, our knowledge on the development of the relevant cognitive mechanisms is limited. The present longitudinal study investigated the developmental trajectories of numerical processing in 42 children with age-adequate arithmetic development and 41 children with dyscalculia over a two-year period from beginning of Grade 2, when children were 7;6 years old, to beginning of Grade 4. A battery of numerical processing tasks (dot enumeration, non-symbolic and symbolic comparison of one- and two-digit numbers, physical comparison, number line estimation was given five times during the study (beginning and middle of each school year. Efficiency of numerical processing was a very good indicator of development in numerical processing while within-task effects remained largely constant and showed low long-term stability before middle of Grade 3. Children with dyscalculia showed less efficient numerical processing reflected in specifically prolonged response times. Importantly, they showed consistently larger slopes for dot enumeration in the subitizing range, an untypically large compatibility effect when processing two-digit numbers, and they were consistently less accurate in placing numbers on a number line. Thus, we were able to identify parameters that can be used in future research to characterize numerical processing in typical and dyscalculic development. These parameters can also be helpful for identification of children who struggle in their numerical development.

Numerical methods for image registration

CERN Document Server

Modersitzki, Jan

2003-01-01

Based on the author's lecture notes and research, this well-illustrated and comprehensive text is one of the first to provide an introduction to image registration with particular emphasis on numerical methods in medical imaging. Ideal for researchers in industry and academia, it is also a suitable study guide for graduate mathematicians, computer scientists, engineers, medical physicists, and radiologists.Image registration is utilised whenever information obtained from different viewpoints needs to be combined or compared and unwanted distortion needs to be eliminated. For example, CCTV imag

a qualitative study of providers' perspectives

African Journals Online (AJOL)

Background: Glaucoma management is challenging to patients as well as to the eye care providers.The study is aimed at describing the challenges faced by providers using qualitative methods. Methods: In-depth interviews were conducted with selected Ophthalmologists and resident doctors in ophthalmology at centres ...

Numerical study on visualization method for material distribution using photothermal effect

International Nuclear Information System (INIS)

Kim, Moo Joong; Yoo, Jai Suk; Kim, Dong Kwon; Kim, Hyun Jung

2015-01-01

Visualization and imaging techniques have become increasingly essential in a wide range of industrial fields. A few imaging methods such as X-ray imaging, computed tomography and magnetic resonance imaging have been developed for medical applications to materials that are basically transparent or X-ray penetrable; however, reliable techniques for optically opaque materials such as semiconductors or metallic circuits have not been suggested yet. The photothermal method has been developed mainly for the measurement of thermal properties using characteristics that exhibit photothermal effects depending on the thermal properties of the materials. This study attempts to numerically investigate the feasibility of using photothermal effects to visualize or measure the material distribution of opaque substances. For this purpose, we conducted numerical analyses of various intaglio patterns with approximate sizes of 1.2-6 mm in stainless steel 0.5 mm below copper. In addition, images of the intaglio patterns in stainless steel were reconstructed by two-dimensional numerical scanning. A quantitative comparison of the reconstructed results and the original geometries showed an average difference of 0.172 mm and demonstrated the possibility of application to experimental imaging.

Experimental-numerical study of heat flow in deep low-enthalpy geothermal conditions

NARCIS (Netherlands)

Saeid, S.; Al-Khoury, R.; Nick, H.M.; Barends, F.

2014-01-01

This paper presents an intensive experimental-numerical study of heat flow in a saturated porous domain. A temperature and a flow rate range compared to that existing in a typical deep low-enthalpy hydrothermal system is studied. Two main issues are examined: the effect of fluid density and

Numerical Study of the Critical Impact Velocity in Shear. Appendix Number 1

National Research Council Canada - National Science Library

Klosak, M

1996-01-01

.... A numerical study of impact shearing of a layer has been performed by the FE code ABAQUS. It was intended to verify available experimental results for VAR 4340 steel 52 HRC, obtained by direct...

A numerical study of three-dimensional droplets spreading on chemically patterned surfaces

KAUST Repository

Zhong, Hua; Wang, Xiao-Ping; Sun, Shuyu

2016-01-01

We study numerically the three-dimensional droplets spreading on physically flat chemically patterned surfaces with periodic squares separated by channels. Our model consists of the Navier-Stokes-Cahn-Hilliard equations with the generalized Navier

Seismic Response Of Masonry Plane Walls: A Numerical Study On Spandrel Strength

International Nuclear Information System (INIS)

Betti, Michele; Galano, Luciano; Vignoli, Andrea

2008-01-01

The paper reports the results of a numerical investigation on masonry walls subjected to in-plane seismic loads. This research aims to verify the formulae of shear and flexural strength of masonry spandrels which are given in the recent Italian Standards. Seismic pushover analyses have been carried out using finite element models of unreinforced walls and strengthened walls introducing reinforced concrete (RC) beams at the floor levels. Two typologies of walls have been considered distinguished for the height to length ratio h/l of the spandrels: a) short beams (h/l = 1.33) and b) slender beams (h/l = 0.5). Results obtained for the unreinforced and the strengthened walls are compared with equations for shear and flexural strength provided in Standards [1]. The numerical analyses show that the reliability of these equations is at least questionable especially for the prediction of the flexural strength. In the cases in which the axial force has not been determined by the structural analysis, Standards seems to overestimate the flexural strength of short spandrels both for the unreinforced and the strengthened wall

Seismic Response Of Masonry Plane Walls: A Numerical Study On Spandrel Strength

Science.gov (United States)

Betti, Michele; Galano, Luciano; Vignoli, Andrea

2008-07-01

The paper reports the results of a numerical investigation on masonry walls subjected to in-plane seismic loads. This research aims to verify the formulae of shear and flexural strength of masonry spandrels which are given in the recent Italian Standards [1]. Seismic pushover analyses have been carried out using finite element models of unreinforced walls and strengthened walls introducing reinforced concrete (RC) beams at the floor levels. Two typologies of walls have been considered distinguished for the height to length ratio h/l of the spandrels: a) short beams (h/l = 1.33) and b) slender beams (h/l = 0.5). Results obtained for the unreinforced and the strengthened walls are compared with equations for shear and flexural strength provided in Standards [1]. The numerical analyses show that the reliability of these equations is at least questionable especially for the prediction of the flexural strength. In the cases in which the axial force has not been determined by the structural analysis, Standards [1] seems to overestimate the flexural strength of short spandrels both for the unreinforced and the strengthened wall.

Parametrical Numerical Study on Breakwater SSG Application

DEFF Research Database (Denmark)

Margheritini, Lucia; Kofoed, Jens Peter

The report presents numerical investigations on the performance of the SSG concept for different tide and wave conditions towards different levels of discretization to an optimal solution. Benefit of extra reservoir utilization and reservoir length has also been investigated. The report must be c...

NUMERICAL STUDY ON COOLING EFFECT POTENTIAL FROM VAPORIZER DEVICE OF LPG VEHICLE

Directory of Open Access Journals (Sweden)

MUJI SETIYO

2017-07-01

Full Text Available Over fuel consumption and increased exhaust gas due to the A/C system have become a serious problem. On the other hand, the LPG-fueled vehicle provides potential cooling from LPG phase changes in the vaporizer. Therefore, this article presents the potential cooling effect calculation from 1998 cm3 spark ignition (SI engine. A numerical study is used to calculate the potential heat absorption of latent and sensible heat transfer during LPG is expanded in the vaporizer. Various LPG compositions are also simulated through the engine speed range from 1000 to 6000 rpm. The result shows that the 1998 cm3 engine capable of generating the potential cooling effect of about 1.0 kW at 1000 rpm and a maximum of up to 1.8 kW at 5600 rpm. The potential cooling effects from the LPG vaporizer contributes about 26% to the A/C system works on eco-driving condition.

Field and numerical studies of flow structure in Lake Shira (Khakassia) in summer

Science.gov (United States)

Yakubaylik, Tatyana; Kompaniets, Lidia

2014-05-01

Investigations of Lake Shira are conducted within a multidisciplinary approach that includes the study of biodiversity, biochemistry, geology of lake sediments, as well as its hydrophysics. Our report focuses on field measurements in the lake during the 2009 - 2013 and numerical modeling of flow structure. The flow velocity, temperature and salinity distribution and fluctuations of the thermocline (density) were measured in summer. An analysis of spatial and temporal variability of the major hydrophysical characteristics leads us to conclusion that certain meteorological conditions may cause internal waves in this lake. Digital terrain model is constructed from measurements of Lake bathymetry allowing us to carry out numerical simulation. Three-dimensional primitive equation numerical model GETM is applied to simulate hydrophysical processes in Lake Shira. The model is hydrostatic and Boussinesq. An algorithm of high order approximation is opted for calculating the equations of heat and salt transfer. Temperature and salinity distributions resulting from field observations are taken as initial data for numerical simulations. Model calculations as well as calculations with appropriate real wind pattern being observed on Lake Shira have been carried out. In the model calculations we follow (1). Significant differences are observed between model calculations with constant wind and calculations with real wind pattern. Unsteady wind pattern leads to the appearance of horizontal vortexes and a significant increase of vertical fluctuations in temperature (density, impurities). It causes lifting of the sediments to the upper layers at the areas where the thermocline contacts the bottom. It is important for understanding the overall picture of the processes occurring in the lake in summer. Comparison of the results of numerical experiments with the field data shows the possibility of such a phenomena in Lake Shira. The work was supported by the Russian Foundation for

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 Boron mixing studies for Loviisa Nuclear Power Plant

Energy Technology Data Exchange (ETDEWEB)

Gango, P. [IVO International Ltd. (Finland)

1995-09-01

A program has been started for studying numerically boron mixing in the downcomer of Loviisa NPP (VVER-440). Mixing during the transport of a diluted slug from the loop to the core might serve as an inherent protection mechanism against severe reactivity accidents in inhomogenous boron dilution scenarios for PWRs. The commercial general purpose Computational Fluid Dynamics (CFD) core PHOENICS is used for solving the governing fluid flow equations in the downcomer geometry of VVER-440. So far numerical analyses have been performed for steady state operation conditions and two different pump driven transients. The steady state analyses focused on model development and validation against existing experimental data. The two pump driven transient scenarios reported are based on slug transport during the start of the sixth and first loop respectively. The results from the two transients show that mixing is case and plant specific; the high and open downcomer geometry of VVER-440 seems to be advantageous from mixing point of view. In addition the analyzing work for the {open_quotes}first pump start{close_quotes} scenario brought up some considerations about flow distribution in the existing experimental facilities.

Numerical study of Taylor bubbles with adaptive unstructured meshes

Science.gov (United States)

Xie, Zhihua; Pavlidis, Dimitrios; Percival, James; Pain, Chris; Matar, Omar; Hasan, Abbas; Azzopardi, Barry

2014-11-01

The Taylor bubble is a single long bubble which nearly fills the entire cross section of a liquid-filled circular tube. This type of bubble flow regime often occurs in gas-liquid slug flows in many industrial applications, including oil-and-gas production, chemical and nuclear reactors, and heat exchangers. The objective of this study is to investigate the fluid dynamics of Taylor bubbles rising in a vertical pipe filled with oils of extremely high viscosity (mimicking the ``heavy oils'' found in the oil-and-gas industry). A modelling and simulation framework is presented here which can modify and adapt anisotropic unstructured meshes to better represent the underlying physics of bubble rise and reduce the computational effort without sacrificing accuracy. The numerical framework consists of a mixed control-volume and finite-element formulation, a ``volume of fluid''-type method for the interface capturing based on a compressive control volume advection method, and a force-balanced algorithm for the surface tension implementation. Numerical examples of some benchmark tests and the dynamics of Taylor bubbles are presented to show the capability of this method. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

Proceeding of 1999-workshop on MHD computations 'study on numerical methods related to plasma confinement'

International Nuclear Information System (INIS)

Kako, T.; Watanabe, T.

2000-06-01

This is the proceeding of 'study on numerical methods related to plasma confinement' held in National Institute for Fusion Science. In this workshop, theoretical and numerical analyses of possible plasma equilibria with their stability properties are presented. There are also various lectures on mathematical as well as numerical analyses related to the computational methods for fluid dynamics and plasma physics. Separate abstracts were presented for 13 of the papers in this report. The remaining 6 were considered outside the subject scope of INIS. (J.P.N.)

Preliminary results of an attempt to provide soil moisture datasets in order to verify numerical weather prediction models

International Nuclear Information System (INIS)

Cassardo, C.; Loglisci, N.

2005-01-01

In the recent years, there has been a significant growth in the recognition of the soil moisture importance in large-scale hydrology and climate modelling. Soil moisture is a lower boundary condition, which rules the partitioning of energy in terms of sensible and latent heat flux. Wrong estimations of soil moisture lead to wrong simulation of the surface layer evolution and hence precipitations and cloud cover forecasts could be consequently affected. This is true for large scale medium-range weather forecasts as well as for local-scale short range weather forecasts, particularly in those situations in which local convection is well developed. Unfortunately; despite the importance of this physical parameter there are only few soil moisture data sets sparse in time and in space around in the world. Due to this scarcity of soil moisture observations, we developed an alternative method to provide soil moisture datasets in order to verify numerical weather prediction models. In this paper are presented the preliminary results of an attempt to verify soil moisture fields predicted by a mesoscale model. The data for the comparison were provided by the simulations of the diagnostic land surface scheme LSPM (Land Surface Process Model), widely used at the Piedmont Regional Weather Service for agro-meteorological purposes. To this end, LSPM was initialized and driven by Synop observations, while the surface (vegetation and soil) parameter values were initialized by ECOCLIMAP global dataset at 1km 2 resolution

The Preliminary Study for Numerical Computation of 37 Rod Bundle in CANDU Reactor

International Nuclear Information System (INIS)

Jeon, Yu Mi; Park, Joo Hwan

2010-09-01

A typical CANDU 6 fuel bundle consists of 37 fuel rods supported by two endplates and separated by spacer pads at various locations. In addition, the bearing pads are brazed to each outer fuel rod with the aim of reducing the contact area between the fuel bundle and the pressure tube. Although the recent progress of CFD methods has provided opportunities for computing the thermal-hydraulic phenomena inside of a fuel channel, it is yet impossible to reflect numerical computations on the detailed shape of rod bundle due to challenges with computing mesh and memory capacity. Hence, the previous studies conducted a numerical computation for smooth channels without considering spacers and bearing pads. But, it is well known that these components are an important factor to predict the pressure drop and heat transfer rate in a channel. In this study, the new computational method is proposed to solve complex geometry such as a fuel rod bundle. Before applying a solution to the problem of the 37 rod bundle, the validity and the accuracy of the method are tested by applying the method to simple geometry. The split channel method has been proposed with the aim of computing the fully shaped CANDU fuel channel with detailed components. The validity was tested by applying the method to the single channel problem. The average temperature have similar values for the considered two methods, while the local temperature shows a slight difference by the effect of conduction heat transfer in the solid region of a rod. Based on the present result, the calculation for the fully shaped 37-rod bundle is scheduled for future work

Catalytically stabilized combustion of lean methane-air-mixtures: a numerical model

Energy Technology Data Exchange (ETDEWEB)

Dogwiler, U; Benz, P; Mantharas, I [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

The catalytically stabilized combustion of lean methane/air mixtures has been studied numerically under conditions closely resembling the ones prevailing in technical devices. A detailed numerical model has been developed for a laminar, stationary, 2-D channel flow with full heterogeneous and homogeneous reaction mechanisms. The computations provide direct information on the coupling between heterogeneous-homogeneous combustion and in particular on the means of homogeneous ignitions and stabilization. (author) 4 figs., 3 refs.

Masonry constructions mechanical models and numerical applications

CERN Document Server

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

A numerical and experimental study of two-phase flow and heat transfer in a porous formation with localized heating from below

International Nuclear Information System (INIS)

Easterday, O.T.; Wang, C.Y.; Cheng, P.

1995-01-01

Understanding and predicting two-phase flow and heat transfer in porous media is of fundamental interest for a number of engineering applications. Examples include thermal technologies for remediation of contaminated subsurfaces, the extraction of geothermal energy from vapor-dominated reservoirs, and the assessment of high-level nuclear waste repositories. A numerical and experimental study is reported for two-phase flow and heat transfer in a horizontal porous formation with water through flow and partial heating from below. Based on a newly developed two-phase mixture model, numerical results of the temperature distribution, liquid saturation, liquid and vapor phase velocity fields are presented for three representative cases with varying inlet velocities. It is found that the resulting two-phase structure and flow patterns are strongly dependent upon the water inlet velocity and the bottom heat flux. The former parameter measures the flow along the horizontal direction, while the latter creates a relative motion between the phases in the vertical direction. Experiments are also performed to measure temperature distributions and to visualize the two-phase flow patterns. Qualitative agreement between experiments and numerical predictions is achieved. Overall, this combined experimental and numerical study has provided new insight into conjugate single- and two-phase flow and heat transfer in porous media, although future research is required if accurate modeling of these complex problems is to be accomplished

An introduction to numerical methods and analysis

CERN Document Server

Epperson, James F

2013-01-01

Praise for the First Edition "". . . outstandingly appealing with regard to its style, contents, considerations of requirements of practice, choice of examples, and exercises.""-Zentralblatt MATH "". . . carefully structured with many detailed worked examples.""-The Mathematical Gazette The Second Edition of the highly regarded An Introduction to Numerical Methods and Analysis provides a fully revised guide to numerical approximation. The book continues to be accessible and expertly guides readers through the many available techniques of numerical methods and analysis. An Introduction to

Numerical study on air turbines with enhanced techniques for OWC wave energy conversion

Science.gov (United States)

Cui, Ying; Hyun, Beom-Soo; Kim, Kilwon

2017-10-01

In recent years, the oscillating water column (OWC) wave energy converter, which can capture wave energy from the ocean, has been widely applied all over the world. As the essential part of the OWC system, the impulse and Wells turbines are capable of converting the low pressure pneumatic energy into the mechanical shaft power. As an enhanced technique, the design of endplate or ring attached to the blade tip is investigated numerically in this paper. 3D numerical models based on a CFD-software FLUENT 12.0 are established and validated by the corresponding experimental results from the reports of Setoguchi et al. (2004) and Takao et al. (2001). Then the flow fields and non-dimensional evaluating coefficients are calculated and analyzed under steady conditions. Results show that the efficiency of impulse turbine with ring can reach up to 0.49 when ϕ=1, which is 4% higher than that in the cases for the endplate-type and the original one. And the ring-type Wells turbine with fixed guide vanes shows the best performance with the maximal efficiency of 0.55, which is 22% higher than that of the original one. In addition, the quasi-steady analysis is used to calculate the mean efficiency and output-work of a wave cycle under sinusoidal flow condition. Taking all together, this study provides support for structural optimization of impulse turbine and Wells turbine in the future.

Case studies in the numerical solution of oscillatory integrals

International Nuclear Information System (INIS)

Adam, G.

1992-06-01

A numerical solution of a number of 53,249 test integrals belonging to nine parametric classes was attempted by two computer codes: EAQWOM (Adam and Nobile, IMA Journ. Numer. Anal. (1991) 11, 271-296) and DO1ANF (Mark 13, 1988) from the NAG library software. For the considered test integrals, EAQWOM was found to be superior to DO1ANF as it concerns robustness, reliability, and friendly user information in case of failure. (author). 9 refs, 3 tabs

Numerical Study of Photoacoustic Pressure for Cancer Therapy

Directory of Open Access Journals (Sweden)

Thomas Grosges

2016-11-01

Full Text Available A commonly used therapy for cancer is based on the necrosis of cells induced by heating through the illumination of nanoparticles embedded in cells. Recently, the photoacoustic pressure shock induced by the illumination pulse was proved and this points to another means of cell destruction. The purpose of this study is to propose a model of the photoacoustic pressure in cells. The numerical resolution of the problem requires the accurate computation of the electromagnetism, the temperature and the pressure around the nanostructures embedded in a cell. Here, the problem of the interaction between an electromagnetic excitation and a gold nanoparticle embedded in a cell domain is solved. The variations of the thermal and photoacoustic pressures are studied in order to analyze the pressure shock wave inducing the collapse of the cell’s membrane in cancer therapy.

Numerical Study of Aeroacoustic Sound on Performance of Bladeless Fan

Science.gov (United States)

Jafari, Mohammad; Sojoudi, Atta; Hafezisefat, Parinaz

2017-03-01

Aeroacoustic performance of fans is essential due to their widespread application. Therefore, the original aim of this paper is to evaluate the generated noise owing to different geometric parameters. In current study, effect of five geometric parameters was investigated on well performance of a Bladeless fan. Airflow through this fan was analyzed simulating a Bladeless fan within a 2 m×2 m×4 m room. Analysis of the flow field inside the fan and evaluating its performance were obtained by solving conservations of mass and momentum equations for aerodynamic investigations and FW-H noise equations for aeroacoustic analysis. In order to design Bladeless fan Eppler 473 airfoil profile was used as the cross section of this fan. Five distinct parameters, namely height of cross section of the fan, outlet angle of the flow relative to the fan axis, thickness of airflow outlet slit, hydraulic diameter and aspect ratio for circular and quadratic cross sections were considered. Validating acoustic code results, we compared numerical solution of FW-H noise equations for NACA0012 with experimental results. FW-H model was selected to predict the noise generated by the Bladeless fan as the numerical results indicated a good agreement with experimental ones for NACA0012. To validate 3-D numerical results, the experimental results of a round jet showed good agreement with those simulation data. In order to indicate the effect of each mentioned parameter on the fan performance, SPL and OASPL diagrams were illustrated.

Numerical study of plasma-wall transition in an oblique magnetic field

International Nuclear Information System (INIS)

Valsaque, Fabrice; Manfredi, Giovanni

2001-01-01

The interaction of a plasma with a fixed wall is investigated numerically. The ions are described by a kinetic model, while the electrons are assumed to be at thermal equilibrium. Finite Debye length effects are taken into account. An Eulerian code is used for the ion dynamics, which enables us to obtain a fine resolution of both position and velocity space. First, we analyse the effect of ionization and collisions, which bring the ion flow to supersonic velocity at the entrance of the Debye sheath (Bohm's criterion). Second, we consider a collisionless sheath with an oblique magnetic field. A magnetic presheath, which has a width of several ion gyroradii, is located between the Debye sheath and the bulk plasma. We perform a systematic numerical study of these sheaths for different incidences of the magnetic field

Numerical methods and modelling for engineering

CERN Document Server

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...

A numerical study of a premixed flame on a slit burner

NARCIS (Netherlands)

Somers, L.M.T.; Goey, de L.P.H.

1995-01-01

A numerical study of a premixed methane/air flame on a 4 mm slit burner is presented. A local grid refinement technique is used to deal with large gradients and curvature of all variables encountered in the flame, keeping the number of grid points within reasonable bounds. The method used here leads

New numerical method to study phase transitions and its applications

International Nuclear Information System (INIS)

Lee, Jooyoung; Kosterlitz, J.M.

1991-11-01

We present a powerful method of identifying the nature of transitions by numerical simulation of finite systems. By studying the finite size scaling properties of free energy barrier between competing states, we can identify unambiguously a weak first order transition even when accessible system sizes are L/ξ < 0.05 as in the five state Potts model in two dimensions. When studying a continuous phase transition we obtain quite accurate estimates of critical exponents by treating it as a field driven first order transition. The method has been successfully applied to various systems

Numerical study of Q-ball formation in gravity mediation

International Nuclear Information System (INIS)

Hiramatsu, Takashi; Kawasaki, Masahiro; Takahashi, Fuminobu

2010-01-01

We study Q-ball formation in the expanding universe on 1D, 2D and 3D lattice simulations. We obtain detailed Q-ball charge distributions, and find that the distribution is peaked at Q 3D peak ≅ 1.9 × 10 −2 (|Φ in |/m) 2 , which is greater than the existing result by about 60%. Based on the numerical simulations, we discuss how the Q-ball formation proceeds. Also we make a comment on possible deviation of the charge distributions from what was conjectured in the past

Numerical study of the grain growth and the thermal properties of ceramics

International Nuclear Information System (INIS)

Shahtahmasebi, N.; Shariaty ghleno, A.M.; Hosaini, M.

2000-04-01

The physical properties of ceramics strongly depends on the grain size, which itself depends on the sintering process. In this work we propose a model for sintering based on the gross features known experimental and the preform numerical study

Numerical ecology with R

CERN Document Server

Borcard, Daniel; Legendre, Pierre

2018-01-01

This new edition of Numerical Ecology with R guides readers through an applied exploration of the major methods of multivariate data analysis, as seen through the eyes of three ecologists. It provides a bridge between a textbook of numerical ecology and the implementation of this discipline in the R language. The book begins by examining some exploratory approaches. It proceeds logically with the construction of the key building blocks of most methods, i.e. association measures and matrices, and then submits example data to three families of approaches: clustering, ordination and canonical ordination. The last two chapters make use of these methods to explore important and contemporary issues in ecology: the analysis of spatial structures and of community diversity. The aims of methods thus range from descriptive to explanatory and predictive and encompass a wide variety of approaches that should provide readers with an extensive toolbox that can address a wide palette of questions arising in contemporary mul...

Theoretical and numerical studies of transonic flow of moist air around a thin airfoil

Energy Technology Data Exchange (ETDEWEB)

Lee, Jang-Chang [School of Mechanical Engineering, Andong National University, Kyongbuk (Korea); Rusak, Zvi [Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, NY (United States)

2002-07-01

Numerical studies of a two-dimensional and steady transonic flow of moist air around a thin airfoil with condensation are presented. The computations are guided by a recent transonic small-disturbance (TSD) theory of Rusak and Lee (2000) on this topic. The asymptotic model provides a simplified framework to investigate the changes in the flow field caused by the heat addition from a nonequilibrium process of condensation of water vapor in the air by homogeneous nucleation. An iterative method which is based on a type-sensitive difference scheme is applied to solve the governing equations. The results demonstrate the similarity rules for transonic flow of moist air and the effects of energy supply by condensation on the flow behavior. They provide a method to formulate various cases with different flow properties that have a sufficiently close behavior and that can be used in future computations, experiments, and design of flow systems operating with moist air. Also, the computations show that the TSD solutions of moist air flows represent the essence of the flow character computed from the inviscid fluid flow equations. (orig.)

Numerical study of non-ideal Vlasov-BGK plasmas

International Nuclear Information System (INIS)

Levchenko, V.D.; Sigov, Y.S.; Premuda, F.

1995-01-01

A relatively simple quasi-classical description of quantum plasmas using as first approximation the Bhatnagar-Gross-Krook (BGK) collision integral, if combined with the modern numerical simulation methods, might be effective tool of a deep study of non-ideal plasma kinetics in a variety of urgent applications as inertial confinement and cold fusion, transport and collective properties of highly condensed plasmas in liquid metals, semi- and superconductors and others. Consider one-dimensional degenerate plasma consisting of thermal electrons and thermal bosons (deuterons) in the vicinity of the equilibrium Fermi- and Bose-type distributions respectively. In the frame of our rough mixed model we solve Vlasov-BGK-Poisson eqs using simplified version of the SUR code

Ring-fault activity at subsiding calderas studied from analogue experiments and numerical modeling

Science.gov (United States)

Liu, Y. K.; Ruch, J.; Vasyura-Bathke, H.; Jonsson, S.

2017-12-01

Several subsiding calderas, such as the ones in the Galápagos archipelago and the Axial seamount in the Pacific Ocean have shown a complex but similar ground deformation pattern, composed of a broad deflation signal affecting the entire volcanic edifice and of a localized subsidence signal focused within the caldera. However, it is still debated how deep processes at subsiding calderas, including magmatic pressure changes, source locations and ring-faulting, relate to this observed surface deformation pattern. We combine analogue sandbox experiments with numerical modeling to study processes involved from initial subsidence to later collapse of calderas. The sandbox apparatus is composed of a motor driven subsiding half-piston connected to the bottom of a glass box. During the experiments the observation is done by five digital cameras photographing from various perspectives. We use Photoscan, a photogrammetry software and PIVLab, a time-resolved digital image correlation tool, to retrieve time-series of digital elevation models and velocity fields from acquired photographs. This setup allows tracking the processes acting both at depth and at the surface, and to assess their relative importance as the subsidence evolves to a collapse. We also use the Boundary Element Method to build a numerical model of the experiment setup, which comprises contracting sill-like source in interaction with a ring-fault in elastic half-space. We then compare our results from these two approaches with the examples observed in nature. Our preliminary experimental and numerical results show that at the initial stage of magmatic withdrawal, when the ring-fault is not yet well formed, broad and smooth deflation dominates at the surface. As the withdrawal increases, narrower subsidence bowl develops accompanied by the upward propagation of the ring-faulting. This indicates that the broad deflation, affecting the entire volcano edifice, is primarily driven by the contraction of the

Numerical capacities as domain-specific predictors beyond early mathematics learning: a longitudinal study.

Science.gov (United States)

Reigosa-Crespo, Vivian; González-Alemañy, Eduardo; León, Teresa; Torres, Rosario; Mosquera, Raysil; Valdés-Sosa, Mitchell

2013-01-01

The first aim of the present study was to investigate whether numerical effects (Numerical Distance Effect, Counting Effect and Subitizing Effect) are domain-specific predictors of mathematics development at the end of elementary school by exploring whether they explain additional variance of later mathematics fluency after controlling for the effects of general cognitive skills, focused on nonnumerical aspects. The second aim was to address the same issues but applied to achievement in mathematics curriculum that requires solutions to fluency in calculation. These analyses assess whether the relationship found for fluency are generalized to mathematics content beyond fluency in calculation. As a third aim, the domain specificity of the numerical effects was examined by analyzing whether they contribute to the development of reading skills, such as decoding fluency and reading comprehension, after controlling for general cognitive skills and phonological processing. Basic numerical capacities were evaluated in children of 3(rd) and 4(th) grades (n=49). Mathematics and reading achievements were assessed in these children one year later. Results showed that the size of the Subitizing Effect was a significant domain-specific predictor of fluency in calculation and also in curricular mathematics achievement, but not in reading skills, assessed at the end of elementary school. Furthermore, the size of the Counting Effect also predicted fluency in calculation, although this association only approached significance. These findings contrast with proposals that the core numerical competencies measured by enumeration will bear little relationship to mathematics achievement. We conclude that basic numerical capacities constitute domain-specific predictors and that they are not exclusively "start-up" tools for the acquisition of Mathematics; but they continue modulating this learning at the end of elementary school.

NUMERICAL STUDY OF ELECTROMAGNETIC WAVES GENERATED BY A PROTOTYPE DIELECTRIC LOGGING TOOL

Science.gov (United States)

To understand the electromagnetic waves generated by a prototype dielectric logging tool, a numerical study was conducted using both the finite-difference, time-domain method and a frequency- wavenumber method. When the propagation velocity in the borehole was greater than th...

Three-dimensional numerical study of heat transfer enhancement in separated flows

Science.gov (United States)

Kumar, Saurav; Vengadesan, S.

2017-11-01

The flow separation appears in a wide range of heat transfer applications and causes poor heat transfer performance. It motivates the study of heat transfer enhancement in laminar as well as turbulent flows over a backward facing step by means of an adiabatic fin mounted on the top wall. Recently, we have studied steady, 2-D numerical simulations in laminar flow and investigated the effect of fin length, location, and orientation. It revealed that the addition of fin causes enhancement of heat transfer and it is very effective to control the flow and thermal behavior. The fin is most effective and sensitive when it is placed exactly above the step. A slight displacement of the fin in upstream of the step causes the complete change of flow and thermal behavior. Based on the obtained 2-D results it is interesting to investigate the side wall effect in three-dimensional simulations. The comparison of two-dimensional and three-dimensional numerical simulations with the available experimental results will be presented. Special attention has to be given to capture unsteadiness in the flow and thermal field.

The State of the Psychology Health Service Provider Workforce

Science.gov (United States)

Michalski, Daniel S.; Kohout, Jessica L.

2011-01-01

Numerous efforts to describe the health service provider or clinical workforce in psychology have been conducted during the past 30 years. The American Psychological Association (APA) has studied trends in the doctoral education pathway and the resultant effects on the broader psychology workforce. During this period, the creation and growth of…

Numerical study of partitions effect on multiplicity of solutions in an infinite channel periodically heated from below

International Nuclear Information System (INIS)

Abourida, B.; Hasnaoui, M.

2005-01-01

Laminar natural convection in an infinite horizontal channel heated periodically from below and provided with thin adiabatic partitions on its lower wall, is investigated numerically. The effect of these partitions on the multiplicity of solutions and heat transfer characteristics in the computational domain is studied. The parameters of the study are the Rayleigh number (10 2 Ra 4.9 x 10 6 ) and the height of the partitions (0 B = h'/H' 1/2). The results obtained in the case of air (Pr = 0.72) as working fluid show that depending on the governing parameters, the existence of multiple solutions is possible. Important differences in terms of heat transfer are observed between two different solutions

High energy gravitational scattering: a numerical study

CERN Document Server

Marchesini, Giuseppe

2008-01-01

The S-matrix in gravitational high energy scattering is computed from the region of large impact parameters b down to the regime where classical gravitational collapse is expected to occur. By solving the equation of an effective action introduced by Amati, Ciafaloni and Veneziano we find that the perturbative expansion around the leading eikonal result diverges at a critical value signalling the onset of a new regime. We then discuss the main features of our explicitly unitary S-matrix down to the Schwarzschild's radius R=2G s^(1/2), where it diverges at a critical value b ~ 2.22 R of the impact parameter. The nature of the singularity is studied with particular attention to the scaling behaviour of various observables at the transition. The numerical approach is validated by reproducing the known exact solution in the axially symmetric case to high accuracy.

Extensible numerical library in JAVA

International Nuclear Information System (INIS)

Aso, T.; Okazawa, H.; Takashimizu, N.

2001-01-01

The authors present the current status of the project for developing the numerical library in JAVA. The authors have presented how object-oriented techniques improve usage and also development of numerical libraries compared with the conventional way at previous conference. The authors need many functions for data analysis which is not provided within JAVA language, for example, good random number generators, special functions and so on. Authors' development strategy is focused on easiness of implementation and adding new features by users themselves not only by developers. In HPC field, there are other focus efforts to develop numerical libraries in JAVA. However, their focus is on the performance of execution, not easiness of extension. Following the strategy, the authors have designed and implemented more classes for random number generators and so on

Numerical study of blow-up in the Davey-Stewartson system

KAUST Repository

Klein, Christian

2013-03-01

Nonlinear dispersive partial differential equations such as the nonlinear Schrödinger equations can have solutions that blow up. We numerically study the long time behavior and potential blow-up of solutions to the focusing Davey-Stewartson II equation by analyzing perturbations of the lump and the Ozawa solutions. It is shown in this way that both are unstable to blow-up and dispersion, and that blow-up in the Ozawa solution is generic.

Numerical study of blow-up in the Davey-Stewartson system

KAUST Repository

Klein, Christian; Muite, Benson; Roidot, Kristelle

2013-01-01

Nonlinear dispersive partial differential equations such as the nonlinear Schrödinger equations can have solutions that blow up. We numerically study the long time behavior and potential blow-up of solutions to the focusing Davey-Stewartson II equation by analyzing perturbations of the lump and the Ozawa solutions. It is shown in this way that both are unstable to blow-up and dispersion, and that blow-up in the Ozawa solution is generic.

A numerical study of variable density flow and mixing in porous media

Science.gov (United States)

Fan, Yin; Kahawita, René

1994-10-01

A numerical study of a negatively buoyant plume intruding into a neutrally stratified porous medium has been undertaken using finite different methods. Of particular interest has been to ascertain whether the experimentally observed gravitational instabilities that form along the lower edge of the plume are reproduced in the numerical model. The model has been found to faithfully reproduce the mean flow as well as the gravitational instabilities in the intruding plume. A linear stability analysis has confirmed the fact that the negatively buoyant plume is in fact gravitationally unstable and that the stability depends on two parameters: a concentration Rayleigh number and a characteristic length scale which is dependent on the transverse dispersivity.

Quantitative study on the statistical properties of fibre architecture of genuine and numerical composite microstructures

DEFF Research Database (Denmark)

Hansen, Jens Zangenberg; Brøndsted, Povl

2013-01-01

A quantitative study is carried out regarding the statistical properties of the fibre architecture found in composite laminates and that generated numerically using Statistical Representative Volume Elements (SRVE’s). The aim is to determine the reliability and consistency of SRVE’s for represent......A quantitative study is carried out regarding the statistical properties of the fibre architecture found in composite laminates and that generated numerically using Statistical Representative Volume Elements (SRVE’s). The aim is to determine the reliability and consistency of SRVE...

A numerical study of non-linear crack tip parameters

Directory of Open Access Journals (Sweden)

F.V. Antunes

2015-07-01

Full Text Available Crack closure concept has been widely used to explain different issues of fatigue crack propagation. However, different authors have questioned the relevance of crack closure and have proposed alternative concepts. The main objective here is to check the effectiveness of crack closure concept by linking the contact of crack flanks with non-linear crack tip parameters. Accordingly, 3D-FE numerical models with and without contact were developed for a wide range of loading scenarios and the crack tip parameters usually linked to fatigue crack growth, namely range of cyclic plastic strain, crack tip opening displacement, size of reversed plastic zone and total plastic dissipation per cycle, were investigated. It was demonstrated that: i LEFM concepts are applicable to the problem under study; ii the crack closure phenomenon has a great influence on crack tip parameters decreasing their values; iii the Keff concept is able to explain the variations of crack tip parameters produced by the contact of crack flanks; iv the analysis of remote compliance is the best numerical parameter to quantify the crack opening level; v without contact there is no effect of stress ratio on crack tip parameters. Therefore it is proved that the crack closure concept is valid.

Experimental and Numerical Study of Twin Underexpanded Impinging Jets

Institute of Scientific and Technical Information of China (English)

Minoru Yaga; Minoru Okano; Masumi Tamashiro; Kenyu Oyakawa

2003-01-01

In this paper, the dual underexpanded impinging jets are experimentally and numerically studied. The experiments were performed by measuring the unsteady and averaged wall static pressures and by visualizing density fields using schlieren method. Numerical calculations were also conducted by solving unsteady three dimensional compressible Navier-Stokes equations with Baldwin-Lomax turbulence model. The main parameters for the dual jets are the non-dimensional distance between the two nozzle centers H/D covering 1.5, 2.0, the nozzle to plate separation L/D 2.0, 3.0,4.0 and 5.0 and the pressure ratio defined by Po/Pb 1.0～6.0, where D is the diameter of each nozzle exit, Po the stagnation pressure and Pb the back pressure. It is found that the agreement between the experiments and the calculations is good. The fountain flow at the middle of the two jets is observed both in the experiments and the calculation. According to FFT analysis of the experiments for the twin jets,relatively low frequency (up to 5 kHz) is dominant for H/D =1.5, L/D =2.0 and pressure ratio Po/Pb =3.0 and 5.0,which is confirmed by the experiments.

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 analysis of bubble rising behavior in a liquid metal using MPS

International Nuclear Information System (INIS)

Chen Ronghua; Tian Wenxi; Zuo Juanli; Su Guanghui; Qiu Suizheng; Xu Jianhui

2011-01-01

Moving Particle Semi-Implicit (MPS) Method has advantages over the traditional mesh-based methods in the accurate capture of the vapor-liquid interface. In the present study, the numerical simulation of single bubble rising behavior in the liquid Pb-Bi alloy had been performed. The numerical results are provided for bubble shape deformation and rising velocity. Numerical simulation results indicate that as the bubble rises, the bubble exhibits in turn spherical, dimpled ellipsoidal, spherical-cap shapes. Terminal velocity of the bubble predicted by MPS agrees well with that predicted by Grace and increases with the initial bubble diameter. (authors)

Numerical relativity

International Nuclear Information System (INIS)

Piran, T.

1982-01-01

There are many recent developments in numerical relativity, but there remain important unsolved theoretical and practical problems. The author reviews existing numerical approaches to solution of the exact Einstein equations. A framework for classification and comparison of different numerical schemes is presented. Recent numerical codes are compared using this framework. The discussion focuses on new developments and on currently open questions, excluding a review of numerical techniques. (Auth.)

Direct numerical simulations of nucleate boiling flows of binary mixtures

International Nuclear Information System (INIS)

Didier Jamet; Celia Fouillet

2005-01-01

Full text of publication follows: Better understand the origin and characteristics of boiling crisis is still a scientific challenge despite many years of valuable studies. One of the reasons why boiling crisis is so difficult to understand is that local and coupled physical phenomena are believed to play a key role in the trigger of instabilities which lead to the dry out of large portions of the heated solid phase. Nucleate boiling of a single bubble is fairly well understood compared to boiling crisis. Therefore, the numerical simulation of a single bubble growth during nucleate boiling is a good candidate to evaluate the capabilities of a numerical method to deal with complex liquid-vapor phenomena with phase-change and eventually to tackle the boiling crisis problem. In this paper, we present results of direct numerical simulations of nucleate boiling. The numerical method used is the second gradient method, which is a diffuse interface method dedicated to liquid vapor flows with phase-change. This study is not intended to provide quantitative results, partly because all the simulations are two-dimensional. However, particular attention is paid to the influence of some parameters on the main features of nucleate boiling, i.e. the radius of departure and the frequency of detachment of bubbles. In particular, we show that, as the contact angle increases, the radius of departure increases whereas the frequency of detachment decreases. Moreover, the influence of the existence of quasi non-condensable gas is studied. Numerical results show an important decrease of the heat exchange coefficient when a small amount of a quasi non-condensable gas is added to the pure liquid-vapor water system. This result is in agreement with experimental observations. Beyond these qualitative results, this numerical study allows to get insight into some important physical phenomena and to confirm that during nucleate boiling, large scale quantities are influenced by small scale

Numerical Study of Transonic Axial Flow Rotating Cascade Aerodynamics – Part 1: 2D Case

Directory of Open Access Journals (Sweden)

Irina Carmen ANDREI

2014-06-01

Full Text Available The purpose of this paper is to present a 2D study regarding the numerical simulation of flow within a transonic highly-loaded rotating cascade from an axial compressor. In order to describe an intricate flow pattern of a complex geometry and given specific conditions of cascade’s loading and operation, an appropriate accurate flow model is a must. For such purpose, the Navier-Stokes equations system was used as flow model; from the computational point of view, the mathematical support is completed by a turbulence model. A numerical comparison has been performed for different turbulence models (e.g. KE, KO, Reynolds Stress and Spallart-Allmaras models. The convergence history was monitored in order to focus on the numerical accuracy. The force vector has been reported in order to express the aerodynamics of flow within the rotating cascade at the running regime, in terms of Lift and Drag. The numerical results, expressed by plots of the most relevant flow parameters, have been compared. It comes out that the selecting of complex flow models and appropriate turbulence models, in conjunction with CFD techniques, allows to obtain the best computational accuracy of the numerical results. This paper aims to carry on a 2D study and a prospective 3D will be intended for the same architecture.

Can numerical simulations accurately predict hydrodynamic instabilities in liquid films?

Science.gov (United States)

Denner, Fabian; Charogiannis, Alexandros; Pradas, Marc; van Wachem, Berend G. M.; Markides, Christos N.; Kalliadasis, Serafim

2014-11-01

Understanding the dynamics of hydrodynamic instabilities in liquid film flows is an active field of research in fluid dynamics and non-linear science in general. Numerical simulations offer a powerful tool to study hydrodynamic instabilities in film flows and can provide deep insights into the underlying physical phenomena. However, the direct comparison of numerical results and experimental results is often hampered by several reasons. For instance, in numerical simulations the interface representation is problematic and the governing equations and boundary conditions may be oversimplified, whereas in experiments it is often difficult to extract accurate information on the fluid and its behavior, e.g. determine the fluid properties when the liquid contains particles for PIV measurements. In this contribution we present the latest results of our on-going, extensive study on hydrodynamic instabilities in liquid film flows, which includes direct numerical simulations, low-dimensional modelling as well as experiments. The major focus is on wave regimes, wave height and wave celerity as a function of Reynolds number and forcing frequency of a falling liquid film. Specific attention is paid to the differences in numerical and experimental results and the reasons for these differences. The authors are grateful to the EPSRC for their financial support (Grant EP/K008595/1).

Numerical modeling for longwall pillar design: a case study from a typical longwall panel in China

Science.gov (United States)

Zhang, Guangchao; Liang, Saijiang; Tan, Yunliang; Xie, Fuxing; Chen, Shaojie; Jia, Hongguo

2018-02-01

This paper presents a new numerical modeling procedure and design principle for longwall pillar design with the assistance of numerical simulation of FLAC3D. A coal mine located in Yanzhou city, Shandong Province, China, was selected for this case study. A meticulously validated numerical model was developed to investigate the stress changes across the longwall pillar with various sizes. In order to improve the reliability of the numerical modeling, a calibration procedure is undertaken to match the Salamon and Munro pillar strength formula for the coal pillar, while a similar calibration procedure is used to estimate the stress-strain response of a gob. The model results demonstrated that when the coal pillar width was 7-8 m, most of the vertical load was carried by the panel rib, whilst the gateroad was overall in a relatively low stress environment and could keep its stability with proper supports. Thus, the rational longwall pillar width was set as 8 m and the field monitoring results confirmed the feasibility of this pillar size. The proposed numerical simulation procedure and design principle presented in this study could be a viable alternative approach for longwall pillar design for other similar projects.

Theoretical and numerical study of heat transfer deterioration in HPLWR

International Nuclear Information System (INIS)

Palko, D.; Anglart, H.

2007-01-01

A numerical investigation of the Heat Transfer Deterioration (HTD) phenomena is performed using the low-Re k - ω turbulence model. Steady state Reynolds-averaged Navier-Stokes equations are solved together with equations for the transport of enthalpy and turbulence. Equations are solved for the supercritical water flow at different pressures, using water properties from the standard IAPWS tables. All cases are extensively validated against experimental data. The influence of buoyancy on the HTD is demonstrated for different mass flow rates in the heated pipes. Numerical results prove that the RANS low-Re turbulence modeling approach is fully capable to simulate the heat transfer in pipes with the water flow at supercritical pressures. A study of buoyancy influence shows that for the low mass flow rates of coolant, the influence of buoyancy forces on the heat transfer in heated pipes is significant. For the high flow rates, buoyancy influence could be neglected and there are clearly other mechanisms causing the decrease in heat transfer at high coolant flow rates. (author)

Numerical Study of Traffic Pollutant Dispersion within Different Street Canyon Configurations

OpenAIRE

Yucong Miao; Shuhua Liu; Yijia Zheng; Shu Wang; Yuan Li

2014-01-01

The objective of this study is to numerically study flow and traffic exhaust dispersion in urban street canyons with different configurations to find out the urban-planning strategies to ease the air pollution. The Computational Fluid Dynamics (CFD) model used in this study—Open Source Field Operation and Manipulation (OpenFOAM) software package—was firstly validated against the wind-tunnel experiment data by using three different k-ε turbulence models. And then the patterns of flow and dispe...

Owl: A General-Purpose Numerical Library in OCaml

OpenAIRE

Wang, Liang

2017-01-01

Owl is a new numerical library developed in the OCaml language. It focuses on providing a comprehensive set of high-level numerical functions so that developers can quickly build up data analytical applications. In this abstract, we will present Owl's design, core components, and its key functionality.

Numerical Capacities as Domain-Specific Predictors beyond Early Mathematics Learning: A Longitudinal Study

Science.gov (United States)

Reigosa-Crespo, Vivian; González-Alemañy, Eduardo; León, Teresa; Torres, Rosario; Mosquera, Raysil; Valdés-Sosa, Mitchell

2013-01-01

The first aim of the present study was to investigate whether numerical effects (Numerical Distance Effect, Counting Effect and Subitizing Effect) are domain-specific predictors of mathematics development at the end of elementary school by exploring whether they explain additional variance of later mathematics fluency after controlling for the effects of general cognitive skills, focused on nonnumerical aspects. The second aim was to address the same issues but applied to achievement in mathematics curriculum that requires solutions to fluency in calculation. These analyses assess whether the relationship found for fluency are generalized to mathematics content beyond fluency in calculation. As a third aim, the domain specificity of the numerical effects was examined by analyzing whether they contribute to the development of reading skills, such as decoding fluency and reading comprehension, after controlling for general cognitive skills and phonological processing. Basic numerical capacities were evaluated in children of 3rd and 4th grades (n=49). Mathematics and reading achievements were assessed in these children one year later. Results showed that the size of the Subitizing Effect was a significant domain-specific predictor of fluency in calculation and also in curricular mathematics achievement, but not in reading skills, assessed at the end of elementary school. Furthermore, the size of the Counting Effect also predicted fluency in calculation, although this association only approached significance. These findings contrast with proposals that the core numerical competencies measured by enumeration will bear little relationship to mathematics achievement. We conclude that basic numerical capacities constitute domain-specific predictors and that they are not exclusively “start-up” tools for the acquisition of Mathematics; but they continue modulating this learning at the end of elementary school. PMID:24255710

Numerical studies of the flux-to-current ratio method in the KIPT neutron source facility

International Nuclear Information System (INIS)

Cao, Y.; Gohar, Y.; Zhong, Z.

2013-01-01

The reactivity of a subcritical assembly has to be monitored continuously in order to assure its safe operation. In this paper, the flux-to-current ratio method has been studied as an approach to provide the on-line reactivity measurement of the subcritical system. Monte Carlo numerical simulations have been performed using the KIPT neutron source facility model. It is found that the reactivity obtained from the flux-to-current ratio method is sensitive to the detector position in the subcritical assembly. However, if multiple detectors are located about 12 cm above the graphite reflector and 54 cm radially, the technique is shown to be very accurate in determining the k eff this facility in the range of 0.75 to 0.975. (authors)

Stable Numerical Approach for Fractional Delay Differential Equations

Science.gov (United States)

Singh, Harendra; Pandey, Rajesh K.; Baleanu, D.

2017-12-01

In this paper, we present a new stable numerical approach based on the operational matrix of integration of Jacobi polynomials for solving fractional delay differential equations (FDDEs). The operational matrix approach converts the FDDE into a system of linear equations, and hence the numerical solution is obtained by solving the linear system. The error analysis of the proposed method is also established. Further, a comparative study of the approximate solutions is provided for the test examples of the FDDE by varying the values of the parameters in the Jacobi polynomials. As in special case, the Jacobi polynomials reduce to the well-known polynomials such as (1) Legendre polynomial, (2) Chebyshev polynomial of second kind, (3) Chebyshev polynomial of third and (4) Chebyshev polynomial of fourth kind respectively. Maximum absolute error and root mean square error are calculated for the illustrated examples and presented in form of tables for the comparison purpose. Numerical stability of the presented method with respect to all four kind of polynomials are discussed. Further, the obtained numerical results are compared with some known methods from the literature and it is observed that obtained results from the proposed method is better than these methods.

Hybrid RANS-LES using high order numerical methods

Science.gov (United States)

Henry de Frahan, Marc; Yellapantula, Shashank; Vijayakumar, Ganesh; Knaus, Robert; Sprague, Michael

2017-11-01

Understanding the impact of wind turbine wake dynamics on downstream turbines is particularly important for the design of efficient wind farms. Due to their tractable computational cost, hybrid RANS/LES models are an attractive framework for simulating separation flows such as the wake dynamics behind a wind turbine. High-order numerical methods can be computationally efficient and provide increased accuracy in simulating complex flows. In the context of LES, high-order numerical methods have shown some success in predictions of turbulent flows. However, the specifics of hybrid RANS-LES models, including the transition region between both modeling frameworks, pose unique challenges for high-order numerical methods. In this work, we study the effect of increasing the order of accuracy of the numerical scheme in simulations of canonical turbulent flows using RANS, LES, and hybrid RANS-LES models. We describe the interactions between filtering, model transition, and order of accuracy and their effect on turbulence quantities such as kinetic energy spectra, boundary layer evolution, and dissipation rate. This work was funded by the U.S. Department of Energy, Exascale Computing Project, under Contract No. DE-AC36-08-GO28308 with the National Renewable Energy Laboratory.

Introduction to the numerical solutions of Markov chains

CERN Document Server

Stewart, Williams J

1994-01-01

A cornerstone of applied probability, Markov chains can be used to help model how plants grow, chemicals react, and atoms diffuse - and applications are increasingly being found in such areas as engineering, computer science, economics, and education. To apply the techniques to real problems, however, it is necessary to understand how Markov chains can be solved numerically. In this book, the first to offer a systematic and detailed treatment of the numerical solution of Markov chains, William Stewart provides scientists on many levels with the power to put this theory to use in the actual world, where it has applications in areas as diverse as engineering, economics, and education. His efforts make for essential reading in a rapidly growing field. Here, Stewart explores all aspects of numerically computing solutions of Markov chains, especially when the state is huge. He provides extensive background to both discrete-time and continuous-time Markov chains and examines many different numerical computing metho...

Numerical study of emergency cryogenics gas relief into confined spaces

CERN Multimedia

CERN. Geneva

2016-01-01

The presented work focuses on the risk analysis and the consequences of the unexpected leak to the tunnel of cryogenics gases. Formation of the gas mixture and its propagation along tunnels is an important issue for the safe operation of cryogenic machines, including superconducting accelerators or free electron lasers. As the cryogenics gas the helium and argon will be considered. A minimal numerical model will be presented and discussed. Series of numerical results related to emergency helium relief to the CERN tunnel and related to unexpected leak of the argon to an underground tunnel, will be shown. The numerical results will show temperature distribution, oxygen deficiency and gas cloud propagation in function of intensity of the leak and intensity of the ventilation.

A Numerical Study of Aerodynamic Performance and Noise of a Bionic Airfoil Based on Owl Wing

Directory of Open Access Journals (Sweden)

Xiaomin Liu

2014-08-01

Full Text Available Noise reduction and efficiency enhancement are the two important directions in the development of the multiblade centrifugal fan. In this study, we attempt to develop a bionic airfoil based on the owl wing and investigate its aerodynamic performance and noise-reduction mechanism at the relatively low Reynolds number. Firstly, according to the geometric characteristics of the owl wing, a bionic airfoil is constructed as the object of study at Reynolds number of 12,300. Secondly, the large eddy simulation (LES with the Smagorinsky model is adopted to numerically simulate the unsteady flow fields around the bionic airfoil and the standard NACA0006 airfoil. And then, the acoustic sources are extracted from the unsteady flow field data, and the Ffowcs Williams-Hawkings (FW-H equation based on Lighthill's acoustic theory is solved to predict the propagation of these acoustic sources. The numerical results show that the lift-to-drag ratio of bionic airfoil is higher than that of the traditional NACA 0006 airfoil because of its deeply concave lower surface geometry. Finally, the sound field of the bionic airfoil is analyzed in detail. The distribution of the A-weighted sound pressure levels, the scaled directivity of the sound, and the distribution of dP/dt on the airfoil surface are provided so that the characteristics of the acoustic sources could be revealed.

Asymptotic and numerical studies of a differential-delay system

Science.gov (United States)

Semak, Matthew Richard

A singularly-perturbed differential-delay equation is studied the form of which is seen in various fields. Relaxation effects are combined with nonlinear driving from the past in this system. Having an infinite dimensional phase space, this flow is capable of very interesting behavior. Among the rich aspects of the dynamics of such a relation, period doubling can be observed as parameters are varied. Rigorous proofs concerning the existence of such periodic solutions can be found in the literature. Attention is given to the (first) Hopf bifurcation as the periodic structure is born. Key questions concern the limit of fast relaxation. In this limit, one can analytically understand the development of the periodic solution in the neighborhood of the bifurcation along with the frequency shift which is encountered. This limit also reveals the underlying mapping structure present. In the model studied, this is the logistic map the behavior of which is well-known. Convergence of periodic solutions to the mapping's square wave involves central issues in this work. An analogue to Gibb's phenomenon presents itself as the mapping structure is approached for a certain range of parameters. Transition layers also exist and, together with the latter, present a challenge to various computational approaches. A highly accurate and efficient spectral numerical technique is introduced to properly resolve such behavior in the limit studied. This scheme is used to measure the period's dependence on the relaxation rate in this region of parameter space. Also, numerically assisted asymptotic analysis develops relations for the layers. Moreover, regimes of parameter values have been identified for which there exist extremely long-lived transient states of arbitrarily complex form. Finally, initial interval states are designed which lead to specific long-lived multi-layer patterns of significant complexity. Layer-layer interactions are considered concerning the formation and lifetime of

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 studies of non-linear evolution of kink and tearing modes in tokamaks

International Nuclear Information System (INIS)

White, R.; Monticello, D.; Rosenbluth, M.N.; Strauss, H.; Kadomtsev, B.B.

1975-01-01

A set of numerical techniques for investigating the full nonlinear unstable behavior of low β kink modes of given helical symmetry in Tokamaks is presented. Uniform current density plasmas display complicated deformations including the formation of large vacuum bubbles provided that the safety factor q is sufficiently close to integral. Fairly large m = 1 deformations, but not bubble formation, persist for a plasma with a parabolic current density profile (and hence shear). Deformations for m greater than or equal to 2 are, however, greatly suppressed. (auth)

Experimental and numerical study of an evaporatively-cooled condenser of air-conditioning systems

International Nuclear Information System (INIS)

Islam, M.R.; Jahangeer, K.A.; Chua, K.J.

2015-01-01

The performance of an air-conditioning unit with evaporately-cooled condenser coil is studied experimentally and numerically. An experimental setup is fabricated by retrofitting a commercially available air-conditioning unit and installing comprehensive measuring sensors and controllers. Experimental result shows that the COP (Coefficient of Performance) of the evaporately-cooled air-conditioning unit increases by about 28% compared to the conventional air cooled air-conditioning unit. To analyze the heat and mass transfer processes involved in the evaporately-cooled condenser, a detailed theoretical model has been developed based on the fluid flow characteristics of the falling film and the thermodynamic aspect of the evaporation process. Simulated results agree well with experimental data. The numerical model provides new insights into the intrinsic links between operating variables and heat transfer characteristics of water film in evaluating the performance of evaporatively-cooled condenser system. Two heat transfer coefficients, namely, wall to bulk and bulk to interface are introduced and computed from the simulation results under different operating conditions. Finally, the overall heat transfer coefficient for the water film is computed and presented as a function of dimensionless variables which can conveniently be employed by engineers to design and analyze high performance evaporatively-cooled heat exchangers. - Highlights: • Performance of evaporatively-cooled condenser is investigated. • Local convective heat transfer coefficients of water film are determined. • Thermal resistance of water film is negligible. • Heat transfer with evaporated vapor plays significant role on performance. • Better condenser performance translates to an improvement in COP

Numerical calculation of elastohydrodynamic lubrication methods and programs

CERN Document Server

Huang, Ping

2015-01-01

The book not only offers scientists and engineers a clear inter-disciplinary introduction and orientation to all major EHL problems and their solutions but, most importantly, it also provides numerical programs on specific application in engineering. A one-stop reference providing equations and their solutions to all major elastohydrodynamic lubrication (EHL) problems, plus numerical programs on specific applications in engineering offers engineers and scientists a clear inter-disciplinary introduction and a concise program for practical engineering applications to most important EHL problems

Numerical Study of Shock-Cylinder Banks Interactions

International Nuclear Information System (INIS)

Wang, S.P.; Anderson, M.H.; Oakley, J.G.; Bonazza, R.

2003-01-01

A numerical parametric study of shock-cylinder banks interactions is presented using a high resolution Euler solver. Staggered cylinder banks of five rows are chosen with the purpose of modeling IFE reactor cooling tube banks. The effect of the aspect ratio of the intercylinder pitch to the distance between successive cylinder rows on the vertical pressure forces acting on the cylinders with different geometries is investigated. Preliminary results show that the largest vertical force develops on the cylinders of the second or third row. This peak pressure force increases with decreasing values of the aspect ratio. It is shown that an increasing second force peak also appears on the successive rows, starting with the second one, with decreasing aspect ratio. It is also observed that the force on the last-row cylinders basically decreases to the level of that on the first row. The results are useful for the optimal design of the cooling tubes system of IFE reactors

A Numerical Matrix-Based method in Harmonic Studies in Wind Power Plants

DEFF Research Database (Denmark)

Dowlatabadi, Mohammadkazem Bakhshizadeh; Hjerrild, Jesper; Kocewiak, Łukasz Hubert

2016-01-01

In the low frequency range, there are some couplings between the positive- and negative-sequence small-signal impedances of the power converter due to the nonlinear and low bandwidth control loops such as the synchronization loop. In this paper, a new numerical method which also considers...... these couplings will be presented. The numerical data are advantageous to the parametric differential equations, because analysing the high order and complex transfer functions is very difficult, and finally one uses the numerical evaluation methods. This paper proposes a numerical matrix-based method, which...

Numerical simulation support to the ESA/THOR mission

Science.gov (United States)

Valentini, F.; Servidio, S.; Perri, S.; Perrone, D.; De Marco, R.; Marcucci, M. F.; Daniele, B.; Bruno, R.; Camporeale, E.

2016-12-01

THOR is a spacecraft concept currently undergoing study phase as acandidate for the next ESA medium size mission M4. THOR has been designedto solve the longstanding physical problems of particle heating andenergization in turbulent plasmas. It will provide high resolutionmeasurements of electromagnetic fields and particle distribution functionswith unprecedented resolution, with the aim of exploring the so-calledkinetic scales. We present the numerical simulation framework which is supporting the THOR mission during the study phase. The THOR teamincludes many scientists developing and running different simulation codes(Eulerian-Vlasov, Particle-In-Cell, Gyrokinetics, Two-fluid, MHD, etc.),addressing the physics of plasma turbulence, shocks, magnetic reconnectionand so on.These numerical codes are being used during the study phase, mainly withthe aim of addressing the following points:(i) to simulate the response of real particle instruments on board THOR, byemploying an electrostatic analyser simulator which mimics the response ofthe CSW, IMS and TEA instruments to the particle velocity distributions ofprotons, alpha particle and electrons, as obtained from kinetic numericalsimulations of plasma turbulence.(ii) to compare multi-spacecraft with single-spacecraft configurations inmeasuring current density, by making use of both numerical models ofsynthetic turbulence and real data from MMS spacecraft.(iii) to investigate the validity of the Taylor hypothesis indifferent configurations of plasma turbulence

A two-dimensional numerical study of the flow inside the combustion chamber of a motored rotary engine

Science.gov (United States)

Shih, T. I-P.; Yang, S. L.; Schock, H. J.

1986-01-01

A numerical study was performed to investigate the unsteady, multidimensional flow inside the combustion chambers of an idealized, two-dimensional, rotary engine under motored conditions. The numerical study was based on the time-dependent, two-dimensional, density-weighted, ensemble-averaged conservation equations of mass, species, momentum, and total energy valid for two-component ideal gas mixtures. The ensemble-averaged conservation equations were closed by a K-epsilon model of turbulence. This K-epsilon model of turbulence was modified to account for some of the effects of compressibility, streamline curvature, low-Reynolds number, and preferential stress dissipation. Numerical solutions to the conservation equations were obtained by the highly efficient implicit-factored method of Beam and Warming. The grid system needed to obtain solutions were generated by an algebraic grid generation technique based on transfinite interpolation. Results of the numerical study are presented in graphical form illustrating the flow patterns during intake, compression, gaseous fuel injection, expansion, and exhaust.

A two-dimensional numerical study of the flow inside the combustion chambers of a motored rotary engine

Science.gov (United States)

Shih, T. I. P.; Yang, S. L.; Schock, H. J.

1986-01-01

A numerical study was performed to investigate the unsteady, multidimensional flow inside the combustion chambers of an idealized, two-dimensional, rotary engine under motored conditions. The numerical study was based on the time-dependent, two-dimensional, density-weighted, ensemble-averaged conservation equations of mass, species, momentum, and total energy valid for two-component ideal gas mixtures. The ensemble-averaged conservation equations were closed by a K-epsilon model of turbulence. This K-epsilon model of turbulence was modified to account for some of the effects of compressibility, streamline curvature, low-Reynolds number, and preferential stress dissipation. Numerical solutions to the conservation equations were obtained by the highly efficient implicit-factored method of Beam and Warming. The grid system needed to obtain solutions were generated by an algebraic grid generation technique based on transfinite interpolation. Results of the numerical study are presented in graphical form illustrating the flow patterns during intake, compression, gaseous fuel injection, expansion, and exhaust.

Handbook of numerical analysis

CERN Document Server

Ciarlet, Philippe G

Mathematical finance is a prolific scientific domain in which there exists a particular characteristic of developing both advanced theories and practical techniques simultaneously. Mathematical Modelling and Numerical Methods in Finance addresses the three most important aspects in the field: mathematical models, computational methods, and applications, and provides a solid overview of major new ideas and results in the three domains. Coverage of all aspects of quantitative finance including models, computational methods and applications Provides an overview of new ideas an

Health care providers' attitudes towards termination of pregnancy: A qualitative study in South Africa

Directory of Open Access Journals (Sweden)

Orner Phyllis

2009-08-01

Full Text Available Abstract Background Despite changes to the abortion legislation in South Africa in 1996, barriers to women accessing abortion services still exist including provider opposition to abortions and a shortage of trained and willing abortion care providers. The dearth of abortion providers undermines the availability of safe, legal abortion, and has serious implications for women's access to abortion services and health service planning. In South Africa, little is known about the personal and professional attitudes of individuals who are currently working in abortion service provision. Exploring the factors which determine health care providers' involvement or disengagement in abortion services may facilitate improvement in the planning and provision of future services. Methods Qualitative research methods were used to collect data. Thirty four in-depth interviews and one focus group discussion were conducted during 2006 and 2007 with health care providers who were involved in a range of abortion provision in the Western Cape Province, South Africa. Data were analysed using a thematic analysis approach. Results Complex patterns of service delivery were prevalent throughout many of the health care facilities, and fragmented levels of service provision operated in order to accommodate health care providers' willingness to be involved in different aspects of abortion provision. Related to this was the need expressed by many providers for dedicated, stand-alone abortion clinics thereby creating a more supportive environment for both clients and providers. Almost all providers were concerned about the numerous difficulties women faced in seeking an abortion and their general quality of care. An overriding concern was poor pre and post abortion counselling including contraceptive counselling and provision. Conclusion This is the first known qualitative study undertaken in South Africa exploring providers' attitudes towards abortion and adds to the body of

Numerical study of free convection in an enclosure with two vertical isothermal walls

International Nuclear Information System (INIS)

Barletta, A.; Rossi di Schio, E.; Zanchini, E.; Nobile, E.; Pinto, F.

2005-01-01

In this paper, natural convection is studied in a 2D-cavity with two vertical isothermal walls, kept at different temperatures, and two adiabatic walls which are either straight (rectangular cavity) or elliptic (modified rectangular cavity). The local mass, momentum and energy balance equations are written in a dimensionless form and solved numerically, by means of two different software packages based on Galerkin finite element methods. With reference to a Prandtl number of 0.71, two rectangular cavities are studied: a square one and a cavity with height double than width. Then, for each value of the ratio between height and width, two cavities with elliptic boundaries are investigated. The numerical solution shows that the elliptic boundaries enhance the mean Nusselt number and the dimensionless mean kinetic energy of the fluid. (authors)

Numerical relativity

CERN Document Server

Shibata, Masaru

2016-01-01

This book is composed of two parts: First part describes basics in numerical relativity, that is, the formulations and methods for a solution of Einstein's equation and general relativistic matter field equations. This part will be helpful for beginners of numerical relativity who would like to understand the content of numerical relativity and its background. The second part focuses on the application of numerical relativity. A wide variety of scientific numerical results are introduced focusing in particular on the merger of binary neutron stars and black holes.

Numerical analysis

CERN Document Server

Khabaza, I M

1960-01-01

Numerical Analysis is an elementary introduction to numerical analysis, its applications, limitations, and pitfalls. Methods suitable for digital computers are emphasized, but some desk computations are also described. Topics covered range from the use of digital computers in numerical work to errors in computations using desk machines, finite difference methods, and numerical solution of ordinary differential equations. This book is comprised of eight chapters and begins with an overview of the importance of digital computers in numerical analysis, followed by a discussion on errors in comput

Numeric data services and sources for the general reference librarian

CERN Document Server

Kellam, Lynda

2011-01-01

The proliferation of online access to social science statistical and numeric data sources, such as the U.S. Census Bureau's American Fact Finder, has lead to an increased interest in supporting these sources in academic libraries. Many large libraries have been able to devote staff to data services for years, and recently smaller academic libraries have recognized the need to provide numeric data services and support. This guidebook serves as a primer to developing and supporting social science statistical and numerical data sources in the academic library. It provides strategies for the estab

Relational complexity modulates activity in the prefrontal cortex during numerical inductive reasoning: an fMRI study.

Science.gov (United States)

Feng, Xiao; Peng, Li; Chang-Quan, Long; Yi, Lei; Hong, Li

2014-09-01

Most previous studies investigating relational reasoning have used visuo-spatial materials. This fMRI study aimed to determine how relational complexity affects brain activity during inductive reasoning, using numerical materials. Three numerical relational levels of the number series completion task were adopted for use: 0-relational (e.g., "23 23 23"), 1-relational ("32 30 28") and 2-relational ("12 13 15") problems. The fMRI results revealed that the bilateral dorsolateral prefrontal cortex (DLPFC) showed enhanced activity associated with relational complexity. Bilateral inferior parietal lobule (IPL) activity was greater during the 1- and 2-relational level problems than during the 0-relational level problems. In addition, the left fronto-polar cortex (FPC) showed selective activity during the 2-relational level problems. The bilateral DLPFC may be involved in the process of hypothesis generation, whereas the bilateral IPL may be sensitive to calculation demands. Moreover, the sensitivity of the left FPC to the multiple relational problems may be related to the integration of numerical relations. The present study extends our knowledge of the prefrontal activity pattern underlying numerical relational processing. Copyright © 2014 Elsevier B.V. All rights reserved.

Mechanical Behaviour of 3D Multi-layer Braided Composites: Experimental, Numerical and Theoretical Study

Science.gov (United States)

Deng, Jian; Zhou, Guangming; Ji, Le; Wang, Xiaopei

2017-12-01

Mechanical properties and failure mechanisms of a newly designed 3D multi-layer braided composites are evaluated by experimental, numerical and theoretical studies. The microstructure of the composites is introduced. The unit cell technique is employed to address the periodic arrangement of the structure. The volume averaging method is used in theoretical solutions while FEM with reasonable periodic boundary conditions and meshing technique in numerical simulations. Experimental studies are also conducted to verify the feasibility of the proposed models. Predicted elastic properties agree well with the experimental data, indicating the feasibility of the proposed models. Numerical evaluation is more accurate than theoretical assessment. Deformations and stress distributions of the unit cell under tension shows displacement and traction continuity, guaranteeing the rationality of the applied periodic boundary conditions. Although compression and tension modulus are close, the compressive strength only reaches 70% of the tension strength. This indicates that the composites can be weakened in compressive loading. Additionally, by analysing the micrograph of fracture faces and strain-stress curves, a brittle failure mechanism is observed both in composites under tension and compression.

Experimental and numerical study of MILD combustion in a lab-scale furnace

NARCIS (Netherlands)

Huang, X.; Tummers, M.J.; Roekaerts, D.J.E.M.; Scherer, Viktor; Fricker, Neil; Reis, Albino

2017-01-01

Mild combustion in a lab-scale furnace has been experimentally and numerically studied. The furnace was operated with Dutch natural gas (DNG) at 10 kW and at an equivalence ratio of 0.8. OH∗chemiluminescence images were taken to characterize the reaction zone. The chemiluminescence intensity is

Numerical study of extreme-ultra-violet generated plasmas in hydrogen

OpenAIRE

Astakhov, Dmitry

2016-01-01

In this thesis, we present the development and study a numerical model of EUV-induced plasma. Understanding of behavior of low pressure low density plasmas is of industrial relevance, because of their potential use for on-line removal of different forms of contaminations from multilayer mirrors, which will help increase the throughput of EUV lithography. The model is 2D axially symmetric particle-in-cell code, hence it allows the full geometry of an axially symmetric chamber to be taken into...

Dispersion of helically corrugated waveguides: Analytical, numerical, and experimental study

International Nuclear Information System (INIS)

Burt, G.; Ronald, K.; Young, A.R.; Phelps, A.D.R.; Cross, A.W.; Konoplev, I.V.; He, W.; Thomson, J.; Whyte, C.G.; Samsonov, S.V.; Denisov, G.G.; Bratman, V.L.

2004-01-01

Helically corrugated waveguides have recently been studied for use in various applications such as interaction regions in gyrotron traveling-wave tubes and gyrotron backward-wave oscillators and as a dispersive medium for passive microwave pulse compression. The paper presents a summary of various methods that can be used for analysis of the wave dispersion of such waveguides. The results obtained from an analytical approach, simulations with the three-dimensional numerical code MAGIC, and cold microwave measurements are analyzed and compared

Study on applicability of numerical simulation to evaluation of gas entrainment due to free surface vortex

International Nuclear Information System (INIS)

Ito, Kei; Kunugi, Tomoaki; Ohshima, Hiroyuki

2008-01-01

An onset condition of gas entrainment (GE) due to free surface vortex has been studied to establish a design of sodium-cooled fast reactor with a higher coolant velocity than conventional designs. Numerous investigations have been conducted experimentally and theoretically; however, the universal onset condition of the GE has not been determined yet due to the nonlinear characteristics of the GE. Recently, we have been studying numerical simulation methods as a promising method to evaluate GE, instead of the reliable but costly real-scale tests. In this paper, the applicability of the numerical simulation methods to the evaluation of the GE is discussed. For the purpose, a quasi-steady vortex in a cylindrical tank and a wake vortex (unsteady vortex) in a rectangular channel were numerically simulated using the volume-of-fluid type two-phase flow calculation method. The simulated velocity distributions and free surface shapes of the quasi-steady vortex showed good (not perfect, however) agreements with experimental results when a fine mesh subdivision and a high-order discretization scheme were employed. The unsteady behavior of the wake vortex was also simulated with high accuracy. Although the onset condition of the GE was slightly underestimated in the simulation results, the applicability of the numerical simulation methods to the GE evaluation was confirmed. (author)

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

A New Language Design for Prototyping Numerical Computation

Directory of Open Access Journals (Sweden)

Thomas Derby

1996-01-01

Full Text Available To naturally and conveniently express numerical algorithms, considerable expressive power is needed in the languages in which they are implemented. The language Matlab is widely used by numerical analysts for this reason. Expressiveness or ease-of-use can also result in a loss of efficiency, as is the case with Matlab. In particular, because numerical analysts are highly interested in the performance of their algorithms, prototypes are still often implemented in languages such as Fortran. In this article we describe a language design that is intended to both provide expressiveness for numerical computation, and at the same time provide performance guarantees. In our language, EQ, we attempt to include both syntactic and semantic features that correspond closely to the programmer's model of the problem, including unordered equations, large-granularity state transitions, and matrix notation. The resulting language does not fit into standard language categories such as functional or imperative but has features of both paradigms. We also introduce the notion of language dependability, which is the idea that a language should guarantee that certain program transformations are performed by all implementations. We first describe the interesting features of EQ, and then present three examples of algorithms written using it. We also provide encouraging performance results from an initial implementation of our language.

Functional imaging of numerical processing in adults and 4-y-old children.

Directory of Open Access Journals (Sweden)

Jessica F Cantlon

2006-05-01

development, prior to sophisticated symbolic numerical experience. More broadly, this is also, to our knowledge, the first cognitive fMRI study to test healthy children as young as 4 y, providing new insights into the neurophysiology of human cognitive development.

Numerical studies of transverse curvature effects on transonic flow stability

Science.gov (United States)

Macaraeg, M. G.; Daudpota, Q. I.

1992-01-01

A numerical study of transverse curvature effects on compressible flow temporal stability for transonic to low supersonic Mach numbers is presented for axisymmetric modes. The mean flows studied include a similar boundary-layer profile and a nonsimilar axisymmetric boundary-layer solution. The effect of neglecting curvature in the mean flow produces only small quantitative changes in the disturbance growth rate. For transonic Mach numbers (1-1.4) and aerodynamically relevant Reynolds numbers (5000-10,000 based on displacement thickness), the maximum growth rate is found to increase with curvature - the maximum occurring at a nondimensional radius (based on displacement thickness) between 30 and 100.

Numerical study on drop formation through a micro nozzle

International Nuclear Information System (INIS)

Kim, Sung Il; Son, Gi Hun

2005-01-01

The drop ejection process from a micro nozzle is investigated by numerically solving the conservation equations for mass and momentum. The liquid-gas interface is tracked by a level set method which is extended for two-fluid flows with irregular solid boundaries. Based on the numerical results, the liquid jet breaking and droplet formation behavior is found to depend strongly on the pulse type of forcing pressure and the contact angle at the gas-liquid-solid interline. The negative pressure forcing can be used to control the formation of satelite droplets. Also, various nozzle shapes are tested to investigate their effect on droplet formation

How Parents Read Counting Books and Non-Numerical Books to Their Preverbal Infants: An Observational Study

OpenAIRE

Alison Goldstein; Thomas Cole; Sara Cordes

2016-01-01

Studies have stressed the importance of counting with children to promote formal numeracy abilities; however little work has investigated when parents begin to engage in this behavior with their young children. In the current study, we investigated whether parents elaborated on numerical information when reading a counting book to their preverbal infants and whether developmental differences in numerical input exist even in the first year of life. Parents and their 5-10 month old infants wer...

Numerical simulation of damage evolution for ductile materials and mechanical properties study

Science.gov (United States)

El Amri, A.; Hanafi, I.; Haddou, M. E. Y.; Khamlichi, A.

2015-12-01

This paper presents results of a numerical modelling of ductile fracture and failure of elements made of 5182H111 aluminium alloys subjected to dynamic traction. The analysis was performed using Johnson-Cook model based on ABAQUS software. The modelling difficulty related to prediction of ductile fracture mainly arises because there is a tremendous span of length scales from the structural problem to the micro-mechanics problem governing the material separation process. This study has been used the experimental results to calibrate a simple crack propagation criteria for shell elements of which one has often been used in practical analyses. The performance of the proposed model is in general good and it is believed that the presented results and experimental-numerical calibration procedure can be of use in practical finite-element simulations.

Numerical simulation of damage evolution for ductile materials and mechanical properties study

International Nuclear Information System (INIS)

Amri, A El; Haddou, M E Y; Hanafi, I; Khamlichi, A

2015-01-01

This paper presents results of a numerical modelling of ductile fracture and failure of elements made of 5182H111 aluminium alloys subjected to dynamic traction. The analysis was performed using Johnson-Cook model based on ABAQUS software. The modelling difficulty related to prediction of ductile fracture mainly arises because there is a tremendous span of length scales from the structural problem to the micro-mechanics problem governing the material separation process. This study has been used the experimental results to calibrate a simple crack propagation criteria for shell elements of which one has often been used in practical analyses. The performance of the proposed model is in general good and it is believed that the presented results and experimental-numerical calibration procedure can be of use in practical finite-element simulations. (paper)

An experimental and numerical study on the improvement of the performance of Savonius wind rotor

International Nuclear Information System (INIS)

Altan, Burcin Deda; Atilgan, Mehmet

2008-01-01

In the present study, a curtain has been designed to increase the low performance of the Savonius wind rotor, a type of vertical-axis wind rotor, and the effect of this curtain on the static rotor performance has been analyzed both experimentally and numerically. Designed to prevent the torque that occurs on the convex blade of the rotor in the negative direction, this curtain has been placed in front of the rotor. Experimental measurements and numerical analysis have been conducted when the Savonius wind rotor is with and without curtain. The static torque values of the rotor have been measured by experiments and calculated by numerical analysis, and finally they have been compared. The best results have been obtained by means of the rotor with curtain. Low static torque values have been obtained with the short curtain dimensions, while a considerable increase has been acquired in the static torque values with the long curtain dimensions. Fluent 6.0 trade software has been used as the numerical method

Numerical and experimental study on laminar round free jet of Ar discharging into stagnant air

International Nuclear Information System (INIS)

Fumizawa, Motoo; Hishida, Makoto; Kunugi, Tomoaki

1990-01-01

The objective of the present study is to investigate numerically and experimentally the behavior of the fluid flow and the mass transfer of argon gas (Ar) laminar round jet discharging into stagnant air along the gravity force. The SIMPLE method and two differential numerical schemes of PLDS and QUICK are used in the TEAM code modified by adding the binary diffusion equation. The solution domain is comprised of 80X40 grids of uniform size. As the result, the following were obtained: The half radius of Ar mass fraction obtained by QUICK was in good agreement with experimental result. The half radii of axial velocity and Ar mass fraction obtained by PLDS were larger than those by QUICK due to numerical viscosity. Numerical analyses by PLDS and QUICK schemes agreed well with experimental results on centerline Ar mass fraction. Computational times of PLDS and QUICK are about 40 min. and 120 min. respectively by FACOM VP100 computer in JAERI. (author)

Spurious Numerical Solutions Of Differential Equations

Science.gov (United States)

Lafon, A.; Yee, H. C.

1995-01-01

Paper presents detailed study of spurious steady-state numerical solutions of differential equations that contain nonlinear source terms. Main objectives of this study are (1) to investigate how well numerical steady-state solutions of model nonlinear reaction/convection boundary-value problem mimic true steady-state solutions and (2) to relate findings of this investigation to implications for interpretation of numerical results from computational-fluid-dynamics algorithms and computer codes used to simulate reacting flows.

Numerical Analysis of Partial Differential Equations

CERN Document Server

Lui, S H

2011-01-01

A balanced guide to the essential techniques for solving elliptic partial differential equations Numerical Analysis of Partial Differential Equations provides a comprehensive, self-contained treatment of the quantitative methods used to solve elliptic partial differential equations (PDEs), with a focus on the efficiency as well as the error of the presented methods. The author utilizes coverage of theoretical PDEs, along with the nu merical solution of linear systems and various examples and exercises, to supply readers with an introduction to the essential concepts in the numerical analysis

Experimental and Numerical Study of Water Entry Supercavity Influenced by Turbulent Drag-Reducing Additives

Directory of Open Access Journals (Sweden)

Chen-Xing Jiang

2014-04-01

Full Text Available The configurational and dynamic characteristics of water entry supercavities influenced by turbulent drag-reducing additives were studied through supercavitating projectile approach, experimentally and numerically. The projectile was projected vertically into water and aqueous solution of CTAC with weight concentrations of 100, 500, and 1000 ppm, respectively, using a pneumatic nail gun. The trajectories of the projectile and the supercavity configuration were recorded by a high-speed CCD camera. Besides, water entry supercavities in water and CTAC solution were numerically simulated based on unsteady RANS scheme, together with application of VOF multiphase model. The Cross viscosity model was adopted to represent the fluid property of CTAC solution. It was obtained that the numerical simulation results are in consistence with experimental data. Numerical and experimental results all show that the length and diameter of supercavity in drag-reducing solution are larger than those in water, and the drag coefficient is smaller than that in water; the maintaining time of supercavity is longer in solution as well. The surface tension plays an important role in maintaining the cavity. Turbulent drag-reducing additives have the potential in enhancement of supercavitation and drag reduction.

Study on numerical methods for transient flow induced by speed-changing impeller of fluid machinery

International Nuclear Information System (INIS)

Wu, Dazhuan; Chen, Tao; Wang, Leqin; Cheng, Wentao; Sun, Youbo

2013-01-01

In order to establish a reliable numerical method for solving the transient rotating flow induced by a speed-changing impeller, two numerical methods based on finite volume method (FVM) were presented and analyzed in this study. Two-dimensional numerical simulations of incompressible transient unsteady flow induced by an impeller during starting process were carried out respectively by using DM and DSR methods. The accuracy and adaptability of the two methods were evaluated by comprehensively comparing the calculation results. Moreover, an intensive study on the application of DSR method was conducted subsequently. The results showed that transient flow structure evolution and transient characteristics of the starting impeller are obviously affected by the starting process. The transient flow can be captured by both two methods, and the DSR method shows a higher computational efficiency. As an application example, the starting process of a mixed-flow pump was simulated by using DSR method. The calculation results were analyzed by comparing with the experiment data.

Experimental and numerical study of temperature fields and flows in flame during the diffusion combustion of certain liquid fuels

Science.gov (United States)

Loboda, E. L.; Matvienko, O. V.; Agafontsev, M. V.; Reyno, V. V.

2017-11-01

The paper represents experimental studying the pulsations of temperature fields and the structure of a flow in the flame formed during the combustion of certain fuels. Also, the paper provides the mathematical modeling of a flow in the flame formed during the combustion of diesel fuels, as well as the comparison with experimental data and the estimation of the scale for turbulent vortices in flame. The experimental results are in satisfactory agreement with numerical modeling, which confirms the hypothesis of similarity for the pulsations of hydrodynamic and thermodynamic parameters.

Numerical simulation study for atomic-resolution x-ray fluorescence holography

International Nuclear Information System (INIS)

Xie Honglan; Gao Hongyi; Chen Jianwen; Xiong Shisheng; Xu Zhizhan; Wang Junyue; Zhu Peiping; Xian Dingchang

2003-01-01

Based on the principle of x-ray fluorescence holography, an iron single crystal model of a body-centred cubic lattice is numerically simulated. From the fluorescence hologram produced numerically, the Fe atomic images were reconstructed. The atomic images of the (001), (100), (010) crystallographic planes were consistent with the corresponding atomic positions of the model. The result indicates that one can obtain internal structure images of single crystals at atomic-resolution by using x-ray fluorescence holography

A review on functional and structural brain connectivity in numerical cognition

Directory of Open Access Journals (Sweden)

Korbinian eMoeller

2015-05-01

Full Text Available Only recently has the complex anatomo-functional system underlying numerical cognition become accessible to evaluation in the living brain. We identified 26 studies investigating brain connectivity in numerical cognition. Despite considerable heterogeneity regarding methodological approaches, populations investigated, and assessment procedures implemented, the results provided largely converging evidence regarding the underlying brain connectivity involved in numerical cognition. Analyses of both functional/effective as well as structural connectivity have consistently corroborated the assumption that numerical cognition is subserved by a fronto-parietal network including (intraparietal as well as (prefrontal cortex sites. Evaluation of structural connectivity has indicated the involvement of fronto-parietal association fibers encompassing the superior longitudinal fasciculus dorsally and the external capsule/extreme capsule system ventrally. Additionally, commissural fibers seem to connect the bilateral intraparietal sulci when number magnitude information is processed. Finally, the identification of projection fibers such as the superior corona radiata indicates connections between cortex and basal ganglia as well as the thalamus in numerical cognition. Studies on functional/effective connectivity further indicated a specific role of the hippocampus. These specifications of brain connectivity augment the triple-code model of number processing and calculation with respect to how grey matter areas associated with specific number-related representations may work together.

EXPERIMENTAL STUDIES AND NUMERICAL ANALYSIS FOR THE DEFORMATIONSTRENGTH CHARACTERISTICS OF RAMMED MICRO-PILES WITH A BROADENED AGGREGATE BASE

Directory of Open Access Journals (Sweden)

V. S. Alekhin

2016-01-01

Full Text Available Objectives. Experimental and theoretical determination of dependencies of strength characteristics of bored micropiles with a pedestal formed by rammed rubble on: casing diameter, fraction, and volume of crushed stone for collapsing macroporous clays. Method. Laboratory and field experiments were carried out; numerical calculations in two-dimensional and threedimensional arrangement for the determination of strain-stress analysis of the foundation using a MIDAS GTS_NX software system, implementing the finite element method and developed for complex geotechnical problems; some recommendations for implementation are provided. Results The dependence of the load-bearing capacity of bored micropiles on a broadened base of rammed aggregate with vertical loading is determined. At the maximum broadening diameter of 3.5 of the micropiles shaft the load-bearing capacity of the subsoil is increased by between 1.8 and 6 times compared with micropiles without broadening depending on the diameter of the pile shaft. During the experimental and numerical studies of the dependencies of deformation-strength parameters of the deep foundation works consisting of a bored micropile with a broadened base, namely the pile diameter, aggregate particle size and volume, seal diameter of the subsoil soil half-space, as well as the development of the theory of formation of the end broadening geometry of rammed aggregate in the form of an ellipsoid of revolution were established. Conclusion The full-scale measurements of the broadening of bored micropiles showed that their shape is close to an ellipsoid of revolution, and the ratio of semi-axes is directly dependent on the characteristics of soil and gravel volume, which was taken into account in the construction of the finite element model in the numerical simulation experiment.The results of numerical studies of the bored micropile loading with broadened base on the MIDAS GTS show good agreement with the results of the

Numerical study of on-fiber metal film geometry on behavior of dual parameter SFBG sensors

International Nuclear Information System (INIS)

Goodarzy, Behnam; Foroozmehr, Ehsan; Alemohammad, Hamidreza

2016-01-01

In this paper, a numerical model for simulating a dual parameter super-structure FBG (SFBG) with on-fiber deposited thin films is developed. A periodic on-fiber thin coating of silver on FBG sensors provides the ability of measuring two parameters of strain and temperature simultaneously. The model consists of a mechanical model to determine the strain of the sensor caused by different loading conditions, coupled with an optical model to calculate the reflected spectrum of the SFBG sensor. A guideline is introduced for designing a SFBG by studying the effect of coating period, coating duty cycle, and coating thickness. The results show that the sideband spacing in such SFBGs is only affected by the coating period while the Bragg peak sensitivity does not depend on coating period. Also the coating duty cycle and the coating thickness can affect both sensitivity of the Bragg peak and the measuring range of a sensor. The validity of the results was studied by comparing with previously reported data. (paper)

The Influence of Sensor Size on Acoustic Emission Waveforms—A Numerical Study

Directory of Open Access Journals (Sweden)

Eleni Tsangouri

2018-01-01

Full Text Available The performance of Acoustic Emission technique is governed by the measuring efficiency of the piezoelectric sensors usually mounted on the structure surface. In the case of damage of bulk materials or plates, the sensors receive the acoustic waveforms of which the frequency and shape are correlated to the damage mode. This numerical study measures the waveforms received by point, medium and large size sensors and evaluates the effect of sensor size on the acoustic emission signals. Simulations are the only way to quantify the effect of sensor size ensuring that the frequency response of the different sensors is uniform. The cases of horizontal (on the same surface, vertical and diagonal excitation are numerically simulated, and the corresponding elastic wave displacement is measured for different sizes of sensors. It is shown that large size sensors significantly affect the wave magnitude and content in both time and frequency domains and especially in the case of surface wave excitation. The coherence between the original and received waveform is quantified and the numerical findings are experimentally supported. It is concluded that sensors with a size larger than half the size of the excitation wavelength start to seriously influence the accuracy of the AE waveform.

Complex blood flow patterns in an idealized left ventricle: A numerical study

Science.gov (United States)

Tagliabue, Anna; Dedè, Luca; Quarteroni, Alfio

2017-09-01

In this paper, we study the blood flow dynamics in a three-dimensional (3D) idealized left ventricle of the human heart whose deformation is driven by muscle contraction and relaxation in coordination with the action of the mitral and aortic valves. We propose a simplified but realistic mathematical treatment of the valves function based on mixed time-varying boundary conditions (BCs) for the Navier-Stokes equations modeling the flow. These switchings in time BCs, from natural to essential and vice versa, model either the open or the closed configurations of the valves. At the numerical level, these BCs are enforced by means of the extended Nitsche's method (Tagliabue et al., Int. J. Numer. Methods Fluids, 2017). Numerical results for the 3D idealized left ventricle obtained by means of Isogeometric Analysis are presented, discussed in terms of both instantaneous and phase-averaged quantities of interest and validated against those available in the literature, both experimental and computational. The complex blood flow patterns are analysed to describe the characteristic fluid properties, to show the transitional nature of the flow, and to highlight its main features inside the left ventricle. The sensitivity of the intraventricular flow patterns to the mitral valve properties is also investigated.

Numerical Study of Motion of Falling Conical Graupel

Science.gov (United States)

Chueh, Chih-Che; Wang, Pao K.; Hashino, Tempei

2018-01-01

In the present study, the attitudes of freely-falling conical graupel with a realistic range of densities are investigated numerically by solving the transient Navier-Stokes equations and the body dynamics equations representing the 6-degrees-of-freedom motion. This framework allows us to determine the position and orientation of the graupel in response to the hydrodynamic force of the flow fields. The results show more significant horizontal movements than those cases with a fixed bulk density of ice assumed in our previous study. This is because the real graupel particles possess the density less than the bulk density of ice, which, in turn, leads to a relatively small mass and a relatively small set of moments of inertia. We demonstrate that, with the six degrees of freedom considered together, when Reynolds number is small, a typical damped oscillation occurs, whereas when Reynolds number is high, amplifying oscillation may occur which leads to more complicated and unpredictable flying attitudes such as tumbling. The drag coefficients obtained in the present study agree with the previous studies and can be approximated by that of spheres of the same Reynolds numbers. We also show that conical graupel can perform significant horizontal translations which can be on the order of 1 km in 1 h.

Numerical precision control and GRACE

International Nuclear Information System (INIS)

Fujimoto, J.; Hamaguchi, N.; Ishikawa, T.; Kaneko, T.; Morita, H.; Perret-Gallix, D.; Tokura, A.; Shimizu, Y.

2006-01-01

The control of the numerical precision of large-scale computations like those generated by the GRACE system for automatic Feynman diagram calculations has become an intrinsic part of those packages. Recently, Hitachi Ltd. has developed in FORTRAN a new library HMLIB for quadruple and octuple precision arithmetic where the number of lost-bits is made available. This library has been tested with success on the 1-loop radiative correction to e + e - ->e + e - τ + τ - . It is shown that the approach followed by HMLIB provides an efficient way to track down the source of numerical significance losses and to deliver high-precision results yet minimizing computing time

Numerical and experimental approaches to study soil transport and clogging in granular filters

Science.gov (United States)

Kanarska, Y.; Smith, J. J.; Ezzedine, S. M.; Lomov, I.; Glascoe, L. G.

2012-12-01

Failure of a dam by erosion ranks among the most serious accidents in civil engineering. The best way to prevent internal erosion is using adequate granular filters in the transition areas where important hydraulic gradients can appear. In case of cracking and erosion, if the filter is capable of retaining the eroded particles, the crack will seal and the dam safety will be ensured. Numerical modeling has proved to be a cost-effective tool for improving our understanding of physical processes. Traditionally, the consideration of flow and particle transport in porous media has focused on treating the media as continuum. Practical models typically address flow and transport based on the Darcy's law as a function of a pressure gradient and a medium-dependent permeability parameter. Additional macroscopic constitutes describe porosity, and permeability changes during the migration of a suspension through porous media. However, most of them rely on empirical correlations, which often need to be recalibrated for each application. Grain-scale modeling can be used to gain insight into scale dependence of continuum macroscale parameters. A finite element numerical solution of the Navier-Stokes equations for fluid flow together with Lagrange multiplier technique for solid particles was applied to the simulation of soil filtration in the filter layers of gravity dam. The numerical approach was validated through comparison of numerical simulations with the experimental results of base soil particle clogging in the filter layers performed at ERDC. The numerical simulation correctly predicted flow and pressure decay due to particle clogging. The base soil particle distribution was almost identical to those measured in the laboratory experiment. It is believed that the agreement between simulations and experimental data demonstrates the applicability of the proposed approach for prediction of the soil transport and clogging in embankment dams. To get more precise understanding of

A numerical study of bulk evaporation and condensation problem

International Nuclear Information System (INIS)

Ding, Z.; Anghaie, S.

1996-01-01

A numerical model is developed to simulate the dynamic behavior of bulk evaporation and condensation process in an encapsulated container with internal heat generation at micro-gravity level. Thermal performance of a multi-phase system with internal heat generation is investigated. The numerical simulation yields the evolution of the bulk liquid-vapor phase change process. This includes the evolution of the liquid-vapor interface, the formation and development of the liquid film covering the side wall surface, the temperature distribution and the convection flow field. An example of such systems is a phase change nuclear fuel element which was first introduced by Ding and Anghaie with application in high temperature space nuclear power and propulsion systems

Numerical Study of Surfactant Dynamics during Emulsification in a T-Junction Microchannel.

Science.gov (United States)

Riaud, Antoine; Zhang, Hao; Wang, Xueying; Wang, Kai; Luo, Guangsheng

2018-04-18

Microchannel emulsification requires large amounts of surfactant to prevent coalescence and improve emulsions lifetime. However, most numerical studies have considered surfactant-free mixtures as models for droplet formation in microchannels, without taking into account the distribution of surfactant on the droplet surface. In this paper, we investigate the effects of nonuniform surfactant coverage on the microfluidic flow pattern using an extended lattice-Boltzmann model. This numerical study, supported by micro-particle image velocimetry experiments, reveals the likelihood of uneven distribution of surfactant during the droplet formation and the appearance of a stagnant cap. The Marangoni effect affects the droplet breakup by increasing the shear rate. According to our results, surfactant-free and surfactant-rich droplet formation processes are qualitatively different, such that both the capillary number and the Damköhler number should be considered when modeling the droplet generation in microfluidic devices. The limitations of traditional volume and pressure estimation methods for determining the dynamic interfacial tension are also discussed on the basis of the simulation results.

Numerical studies of pair creation in counterpropagating laser fields

Energy Technology Data Exchange (ETDEWEB)

Ruf, Matthias

2009-05-27

Pair creation from vacuum induced by electromagnetic fields is probably one of the most intriguing phenomena in physics. If the fields are sufficiently strong, the QED vacuum become unstable. Due to the remarkable progress in laser technology during recent years an experimental investigation of pair creation by pure laser light is coming into reach. The focus of this thesis is on pair creation in counterpropagating laser beams. The pair creation probability is calculated employing the numerically obtained solutions of the Dirac equation. This numerical ansatz has the capability of calculating the momentum distribution of the created pairs in a single propagation, for pure time dependent field configurations. Furthermore, it allows to take the magnetic component of the laser fields into account, which is usually neglected. The latter strongly affects the creation process at high laser frequency. The involved numerical calculations are rather time consuming, therefore the second project of this thesis was to develop a highly efficient code for solving relativistic quantum mechanical problems. This is accomplished by adopting the split-operator method to the Klein-Gordon equation. Here the possibility arises to use parallel computing. However the corresponding spin-statistics becomes crucial in the case of pair creation, demonstrated in several examples. (orig.)

Numerical studies of pair creation in counterpropagating laser fields

International Nuclear Information System (INIS)

Ruf, Matthias

2009-01-01

Pair creation from vacuum induced by electromagnetic fields is probably one of the most intriguing phenomena in physics. If the fields are sufficiently strong, the QED vacuum become unstable. Due to the remarkable progress in laser technology during recent years an experimental investigation of pair creation by pure laser light is coming into reach. The focus of this thesis is on pair creation in counterpropagating laser beams. The pair creation probability is calculated employing the numerically obtained solutions of the Dirac equation. This numerical ansatz has the capability of calculating the momentum distribution of the created pairs in a single propagation, for pure time dependent field configurations. Furthermore, it allows to take the magnetic component of the laser fields into account, which is usually neglected. The latter strongly affects the creation process at high laser frequency. The involved numerical calculations are rather time consuming, therefore the second project of this thesis was to develop a highly efficient code for solving relativistic quantum mechanical problems. This is accomplished by adopting the split-operator method to the Klein-Gordon equation. Here the possibility arises to use parallel computing. However the corresponding spin-statistics becomes crucial in the case of pair creation, demonstrated in several examples. (orig.)

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.

Numerical study of the stopping of aura during migraine

Directory of Open Access Journals (Sweden)

Moussa A.

2010-12-01

Full Text Available This work is devoted to the study of migraine with aura in the human brain. Following [6], we class migraine as a propagation of a wave of depolarization through the cells. The mathematical model used, based on a reaction-diffusion equation, is briefly presented. The equation is considered in a duct containing a bend, in order to model one of the numerous circumvolutions of the brain. For a wide set of parameters, one can establish the existence of a critical radius below which the wave stops. The approximation scheme used for the simulations is first described and then a numerical study is realized, precising the dependence of the critical radius with respect to the different parameters of the model. Ce travail est consacré à l’étude de l’évolution d’une migraine avec aura dans le cerveau humain. Suivant [6], nous assimilons la migraine à une onde de dépolarisation attaquant les cellules du cerveau. Le modèle mathématique retenu, basé sur une équation de réaction-diffusion, est brièvement rappelé. Le domaine d’espace utilisé est constitué d’un conduit présentant un coude, afin de représenter l’une des nombreuses circonvolutions cérébrales. Pour une importante classe de paramètres, il est possible de mettre en évidence l’existence d’un rayon critique au delà duquel le front d’onde n’arrive pas à dépasser le coude. Après une description du schéma d’approximation utilisé, une étude numérique a été réalisée, visant à préciser la dépendance du rayon critique en fonction des différents paramètres du modèle.

Problem-Oriented Simulation Packages and Computational Infrastructure for Numerical Studies of Powerful Gyrotrons

International Nuclear Information System (INIS)

Damyanova, M; Sabchevski, S; Vasileva, E; Balabanova, E; Zhelyazkov, I; Dankov, P; Malinov, P

2016-01-01

Powerful gyrotrons are necessary as sources of strong microwaves for electron cyclotron resonance heating (ECRH) and electron cyclotron current drive (ECCD) of magnetically confined plasmas in various reactors (most notably ITER) for controlled thermonuclear fusion. Adequate physical models and efficient problem-oriented software packages are essential tools for numerical studies, analysis, optimization and computer-aided design (CAD) of such high-performance gyrotrons operating in a CW mode and delivering output power of the order of 1-2 MW. In this report we present the current status of our simulation tools (physical models, numerical codes, pre- and post-processing programs, etc.) as well as the computational infrastructure on which they are being developed, maintained and executed. (paper)

Numerical Study on the 1682 Tainan Historic Tsunami Event

Science.gov (United States)

Tsai, Y.; Wu, T.; Lee, C.; KO, L.; Chuang, M.

2013-12-01

We intend to reconstruct the tsunami source of the 1682/1782 tsunami event in Tainan, Taiwan, based on the numerical method. According to Soloviev and Go (1974), a strong earthquake shook the Tainan and caused severe damage, followed by tsunami waves. Almost the whole island was flooded by tsunami for over 120 km. More than 40,000 inhabitants were killed. Forts Zealand and Pigchingi were washed away. 1682/1782 event was the highest death toll in the Pacific Ocean regarded by Bryant (2001). However, the year is ambiguous in 1682 or 1782, and death toll is doubtful. We tend to believe that this event was happened in 1682 based on the evolution of the harbor name. If the 1682 tsunami event does exist, the hazard mitigation plan has to be modified, and restoring the 1682 event becomes important. In this study, we adopted the tsunami reverse tracking method (TRTM) to examine the possible tsunami sources. A series of numerical simulations were carried out by using COMCOT (Cornell Multi-grid Coupled Tsunami model), and nested grid with 30 m resolution was applied to the study area. According to the result of TRTM, the 1682 tsunami is most likely sourcing from the north segment of Manila Trench. From scenario study, we concluded that the 1682 event was triggered by an Mw >= 8.8 earthquake in north segment of Manila Trench, and 4 m wave height was observed in Tainan and its inundation range is agreeable with historical records. If this scenario occurred again, sever damage and death toll will be seen many high population cities, such as Tainan city, Kaohsiung city and Kenting, where No. 3 nuclear power plant is located. Detailed results will be presented in the full paper. Figure 1. Map of Tsunami Reverse Tracking Method (TRTM) in Tainan. Black arrow indicates direction of possible tsunami direction. The color bar denotes the magnitude of the maximum moment flux. Figure 2. Scenario result of Mw 8.8 in northern segment of Manila Trench. (Left: Initial free surface elevation

Numerical analysis of electromagnetic fields

CERN Document Server

Zhou Pei Bai

1993-01-01

Numerical methods for solving boundary value problems have developed rapidly. Knowledge of these methods is important both for engineers and scientists. There are many books published that deal with various approximate methods such as the finite element method, the boundary element method and so on. However, there is no textbook that includes all of these methods. This book is intended to fill this gap. The book is designed to be suitable for graduate students in engineering science, for senior undergraduate students as well as for scientists and engineers who are interested in electromagnetic fields. Objective Numerical calculation is the combination of mathematical methods and field theory. A great number of mathematical concepts, principles and techniques are discussed and many computational techniques are considered in dealing with practical problems. The purpose of this book is to provide students with a solid background in numerical analysis of the field problems. The book emphasizes the basic theories ...

Numerical studies on helium cooled divertor finger mock up with sectorial extended surfaces

International Nuclear Information System (INIS)

Rimza, Sandeep; Satpathy, Kamalakanta; Khirwadkar, Samir; Velusamy, Karupanna

2014-01-01

Highlights: • Studies on heat transfer enhancement for divertor finger mock-up. • Heat transfer characteristics of jet impingement with extended surfaces have been investigated. • Effect of critical parameters that influence the thermal performance of the finger mock-up by CFD approach. • Effect of extended surface in enhancing heat removal potential with pumping power assessed. • Practicability of the chosen design is verified by structural analysis. - Abstract: Jet impinging technique is an advance divertor concept for the design of future fusion power plants. This technique is extensively used due to its high heat removal capability with reasonable pumping power and for safe operation. In this design, plasma-facing components are fabricated with numerous fingers cooled by helium jets to reduce the thermal stresses. The present study is focused towards finding an optimum performance of one such finger mock-up through systematic computational fluid dynamics (CFD) studies. Heat transfer characteristics of jet impingement have been numerically investigated with sectorial extended surfaces (SES). The result shows that addition of SES enhances heat removal potential with minimum pumping power. Detailed parametric studies on critical parameters that influence thermal performance of the finger mock-up have been analyzed. Thermo-mechanical analysis has been carried out through finite element based approach to know the state of stress in the assembly as a result of large temperature gradients. It is seen that the stresses are within the permissible limits for the present design. The whole numerical simulation has been carried out using general-purpose CFD software (ANSYS FLUENT, Release 14.0, User Guide, Ansys, Inc., 2011). Benchmark validation studies have been performed against high-heat flux experiments (B. Končar, P. Norajitra, K. Oblak, Appl. Therm. Eng., 30, 697–705, 2010) and a good agreement is noticed between the present simulation and the reported

Numerical study of circular synthetic jets at low Reynolds numbers

International Nuclear Information System (INIS)

Xia, Qingfeng; Lei, Shenghui; Ma, Jieyan; Zhong, Shan

2014-01-01

Highlights: • Parameter maps depicting different flow regimes of synthetic jets are produced. • Boundaries separating these regimes are defined using quantitative criteria. • The Reynolds number is most appropriate for classifying different flow regimes. • A use of high suction cycle factors enhances the effectiveness of synthetic jets. - Abstract: In this paper, the flow patterns of circular synthetic jets issuing into a quiescent flow at low Reynolds numbers are studied numerically. The results confirm the presence of the three jet flow regimes, i.e. no jet formation, jet flow without rollup and jet flow with rollup reported in the literature. The boundaries of the different jet flow regimes are determined by tracking the structures produced by the synthetic jets in the near field of the jet orifice over several actuation cycles and examining the cycle-averaged streamwise velocity profiles along the jet central axis. When the Stokes number is above a certain threshold value appropriate for the corresponding flow regime, a good correlation between the flow patterns and the jet Reynolds number defined using the jet orifice diameter, Re Do , is also found. Furthermore, the flow structures of synthetic jets with different suction duty cycle factors are compared. The use of a high suction duty cycle factor strengthens the synthetic jet resulting in a greater penetration depth into the surrounding fluid. Overall, the finding from this study enables the flow regimes, in which a synthetic jet actuator with a circular orifice operates, to be determined. It also provides a way of designing more effective synthetic jet actuators for enhancing mass and momentum transfer at very low Reynolds numbers

Numerical Methods for Partial Differential Equations

CERN Document Server

Guo, Ben-yu

1987-01-01

These Proceedings of the first Chinese Conference on Numerical Methods for Partial Differential Equations covers topics such as difference methods, finite element methods, spectral methods, splitting methods, parallel algorithm etc., their theoretical foundation and applications to engineering. Numerical methods both for boundary value problems of elliptic equations and for initial-boundary value problems of evolution equations, such as hyperbolic systems and parabolic equations, are involved. The 16 papers of this volume present recent or new unpublished results and provide a good overview of current research being done in this field in China.

Ferrofluids: Modeling, numerical analysis, and scientific computation

Science.gov (United States)

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

Integrating inventory control and capacity management at a maintenance service provider

NARCIS (Netherlands)

Buyukkaramikli, N.C.; Ooijen, van H.P.G.; Bertrand, J.W.M.

2015-01-01

In this paper, we study the capacity flexibility problem of a maintenance service provider, who is running a repair shop and is responsible for the availability of numerous specialized systems which contain a critical component that is prone to failure. Upon a critical component failure, the

Comparative numerical and experimental study of two combined wind and wave energy concepts

Directory of Open Access Journals (Sweden)

Zhen Gao

2016-01-01

Full Text Available With a successful and rapid development of offshore wind industry and increased research activities on wave energy conversion in recent years, there is an interest in investigating the technological and economic feasibility of combining offshore wind turbines (WTs with wave energy converters (WECs. In the EU FP7 MARINA Platform project, three floating combined concepts, namely the spar torus combination (STC, the semi-submersible flap combination (SFC and the oscillating water column (OWC array with a wind turbine, were selected and studied in detail by numerical and experimental methods. This paper summarizes the numerical modeling and analysis of the two concepts: STC and SFC, the model tests at a 1:50 scale under simultaneous wave and wind excitation, as well as the comparison between the numerical and experimental results. Both operational and survival wind and wave conditions were considered. The numerical analysis was based on a time-domain global model using potential flow theory for hydrodynamics and blade element momentum theory (for SFC or simplified thrust force model (for STC for aerodynamics. Different techniques for model testing of combined wind and wave concepts were discussed with focus on modeling of wind turbines by disk or redesigned small-scale rotor and modeling of power take-off (PTO system for wave energy conversion by pneumatic damper or hydraulic rotary damper. In order to reduce the uncertainty due to scaling, the numerical analysis was performed at model scale and both the numerical and experimental results were then up-scaled to full scale for comparison. The comparison shows that the current numerical model can well predict the responses (motions, PTO forces, power production of the combined concepts for most of the cases. However, the linear hydrodynamic model is not adequate for the STC concept in extreme wave conditions with the torus fixed to the spar at the mean water level for which the wave slamming on the

Combustion behaviour of pulverised wood - Numerical and experimental studies

Energy Technology Data Exchange (ETDEWEB)

Lixin Tao [TPS Termiska Processer AB, Nykoeping (Sweden)

2002-05-01

analysers. Gas-phase measurements included CO and CO{sub 2} (NDIR), O{sub 2} (paramagnetic analyser), NO (chemiluminescent detector), light hydrocarbons (THC-FID) and H{sub 2} (gas chromatography). The liquid solutions were analysed for HCN and NH{sub 3} using ion-specific electrodes. The amount of tar (heavy hydrocarbons) was determined through the measurement of TOC in the quench liquor. Solid samples were separated from the quench liquor by filtration and then analysed for their elementary fractions of C, H, O, N and ash. The experimental results are presented and discussed in this report. The presented results show that the experimental furnace and measurement facilities used in this work are generally adequate for study of pulverised wood combustion in controlled environment and provide necessary in-flame measured experimental data to support and validate the numerical models that are developed for simulation of pulverised wood combustion in furnaces and boilers. The problems occurred during the experiment are identified and future improvements are discussed.

Numerical study of drop spreading on a flat surface

Science.gov (United States)

Wang, Sheng; Desjardins, Olivier

2017-11-01

In this talk, we perform a numerical study of a droplet on a flat surface with special emphasis on capturing the spreading dynamics. The computational methodology employed is tailored for simulating large-scale two-phase flows within complex geometries. It combines a conservative level-set method to capture the liquid-gas interface, a conservative immersed boundary method to represent the solid-fluid interface, and a sub-grid curvature model at the triple-point to implicitly impose the contact angle of the liquid-gas interface. The performance of the approach is assessed in the inertial droplet spreading regime, the viscous spreading regime of high viscosity drops, and with the capillary oscillation of low viscosity droplets.

Numerical simulation of small scale soft impact tests

International Nuclear Information System (INIS)

Varpasuo, Pentti

2008-01-01

This paper describes the small scale soft missile impact tests. The purpose of the test program is to provide data for the calibration of the numerical simulation models for impact simulation. In the experiments, both dry and fluid filled missiles are used. The tests with fluid filled missiles investigate the release speed and the droplet size of the fluid release. This data is important in quantifying the fire hazard of flammable liquid after the release. The spray release velocity and droplet size are also input data for analytical and numerical simulation of the liquid spread in the impact. The behaviour of the impact target is the second investigative goal of the test program. The response of reinforced and pre-stressed concrete walls is studied with the aid of displacement and strain monitoring. (authors)

Numerical studies of the influence of food ingestion on phytoplankton and zooplankton biomasses

Directory of Open Access Journals (Sweden)

Lidia Dzierzbicka-G³owacka

2002-03-01

Full Text Available This paper presents the numerical simulations of the influence of food ingestion by a herbivorous copepod on phytoplankton and zooplankton biomasses (PZB in the sea. The numerical studies were carried out using the phytoplankton-zooplankton-nutrient-detritus PhyZooNuDe biological upper layer model. This takes account both of fully developed primary production and regeneration mechanisms and of daily migration of zooplankton. In this model the zooplankton is treated not as a 'biomass' but as organisms having definite patterns of growth, reproduction and mortality. Assuming also that {Zoop} is composed ofi cohorts of copepods with weights Wi and numbers Zi, then {Zoop} = WiZi. The PhyZooNuDe model consists of three coupled, partial second-order differential equations of the diffusion type for phytoplankton, zooplankton and nutrients, and one ordinary first-order differential equation for the benthic detritus pool, together with initial and boundary conditions. The calculations were made during 90 days (April, May and June for the study area P1 (Gdansk Deep in an area 0z<=20 m with a vertical space step of 0.1 m and a time step of 300 s. The simulation given here demonstrated the importance of food ingestion by zooplankton in that it can alter the nature of the interactions of plants and herbivores. The analysis of these numerical studies indicate that the maximal ingestion rate and the half-saturation constant for grazing strongly affect the magnitude of the spring bloom and the cyanobacterial bloom, and also the total zooplankton biomass.

Numerical study on aerodynamics of banked wing in ground effect

Directory of Open Access Journals (Sweden)

Qing Jia

2016-03-01

Full Text Available Unlike conventional airplane, a WIG craft experiences righting moment and adverse yaw moment in banked turning in ground effect. Numerical simulations are carried out to study the aerodynamics of banked wing in ground effect. Configurations of rectangular wing and delta wing are considered, and performance of endplates and ailerons during banking are also studied. The study shows that righting moment increase nonlinearly with heeling angle, and endplates enhance the righting. The asymmetric aerodynamic distribution along span of wing with heeling angle introduces adverse yaw moment. Heeling in ground effect with small ground clearance increases the vertical aerodynamic force and makes WIG craft climb. Deflections of ailerons introduce lift decrease and a light pitching motion. Delta wing shows advantage in banked turning for smaller righting moment and adverse yaw moment during banking.

A Numerical Approach to Solving an Inverse Heat Conduction Problem Using the Levenberg-Marquardt Algorithm

Directory of Open Access Journals (Sweden)

Tao Min

2014-01-01

Full Text Available This paper is intended to provide a numerical algorithm involving the combined use of the Levenberg-Marquardt algorithm and the Galerkin finite element method for estimating the diffusion coefficient in an inverse heat conduction problem (IHCP. In the present study, the functional form of the diffusion coefficient is unknown a priori. The unknown diffusion coefficient is approximated by the polynomial form and the present numerical algorithm is employed to find the solution. Numerical experiments are presented to show the efficiency of the proposed method.

Observations and numerical studies of gamma-ray emission in colliding-wind binaries

International Nuclear Information System (INIS)

Reitberger, K.

2014-01-01

Massive stars in binary systems have long been regarded as potential sources of high-energy gamma rays. The emission is thought to arise in the region where the stellar winds collide, thereby producing accelerated particles which subsequently emit gamma rays.This scenario is supported by observations with the Fermi Large Area Telescope presented in this thesis. To address the underlying emission mechanisms in a quantitative way, numerical simulations that incorporate hydrodynamics, the acceleration of charged particles as well as the subsequent gamma-ray emission were found to be needed.This thesis presents the analysis of a high-energy gamma-ray source and its identification with the particle-accelerating colliding-wind binary system Eta Carinae. In order to go beyond the present understanding of such objects, this work provides detailed description of a new 3D-hydrodynamical model, which incorporates the line-driven acceleration of the winds, gravity, orbital motion and the radiative cooling of the shocked plasma, as well as the diffusive shock acceleration of charged particles in the wind collision region. In a subsequent step we simulate and study the resulting gamma-ray emission via relativistic bremsstrahlung, anisotropic inverse Compton radiation and neutral pion decay. (author) [de

Buckling and Fracture Investigation of Debonded Sandwich Columns: An Experimental and Numerical Study

DEFF Research Database (Denmark)

Berggreen, Christian; Carlsson, Leif A.; Avilés, F.

2008-01-01

An experimental and numerical study of in-plane compression of foam core sandwich columns with implanted trough width face/core debond is presented. Experiments were conducted for columns with two different face thicknesses over different cores and debond lengths. The debonded region was monitore...

Analysis of the Numerical Diffusion in Anisotropic Mediums: Benchmarks for Magnetic Field Aligned Meshes in Space Propulsion Simulations

Directory of Open Access Journals (Sweden)

Daniel Pérez-Grande

2016-11-01

Full Text Available This manuscript explores numerical errors in highly anisotropic diffusion problems. First, the paper addresses the use of regular structured meshes in numerical solutions versus meshes aligned with the preferential directions of the problem. Numerical diffusion in structured meshes is quantified by solving the classical anisotropic diffusion problem; the analysis is exemplified with the application to a numerical model of conducting fluids under magnetic confinement, where rates of transport in directions parallel and perpendicular to a magnetic field are quite different. Numerical diffusion errors in this problem promote the use of magnetic field aligned meshes (MFAM. The generation of this type of meshes presents some challenges; several meshing strategies are implemented and analyzed in order to provide insight into achieving acceptable mesh regularity. Second, Gradient Reconstruction methods for magnetically aligned meshes are addressed and numerical errors are compared for the structured and magnetically aligned meshes. It is concluded that using the latter provides a more correct and straightforward approach to solving problems where anisotropicity is present, especially, if the anisotropicity level is high or difficult to quantify. The conclusions of the study may be extrapolated to the study of anisotropic flows different from conducting fluids.

Numerical semigroups and applications

CERN Document Server

Assi, Abdallah

2016-01-01

This work presents applications of numerical semigroups in Algebraic Geometry, Number Theory, and Coding Theory. Background on numerical semigroups is presented in the first two chapters, which introduce basic notation and fundamental concepts and irreducible numerical semigroups. The focus is in particular on free semigroups, which are irreducible; semigroups associated with planar curves are of this kind. The authors also introduce semigroups associated with irreducible meromorphic series, and show how these are used in order to present the properties of planar curves. Invariants of non-unique factorizations for numerical semigroups are also studied. These invariants are computationally accessible in this setting, and thus this monograph can be used as an introduction to Factorization Theory. Since factorizations and divisibility are strongly connected, the authors show some applications to AG Codes in the final section. The book will be of value for undergraduate students (especially those at a higher leve...

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.

Experimental study and numerical optimization of tensegrity domes - A case study

Science.gov (United States)

Winkelmann, Karol; Kłos, Filip; Rąpca, Mateusz

2018-01-01

The paper deals with the design, experimental analysis and numerical optimization of tensegrity dome models. Two structures are analyzed - a Geiger system dome (preliminary dome), with PVC-U bars and PA6/PP/PET tendons and a Fuller system dome (target dome), with wooden bars and steel cables as tendons. All used materials are experimentally tested in terms of Young's modulus and yield stress values, the compressed bars are also tested for the limit length demarcating the elastic buckling from plastic failure. The data obtained in experiments is then implemented in SOFiSTiK commercial software FE model. The model's geometrical parameters are considered uniform random variables. Geometrically and materially nonlinear analysis is carried out. Based on the obtained structural response (displacements), a Monte Carlo simulation - based approach is incorporated for both structural design point formulation and the SLS requirements fulfillment analysis. Finally, an attempt is made to erect the Fuller dome model in order to compare the numerical results of an experimentally-derived model with the in situ measurements of an actual structure.

Numerical study on xenon positive column discharges of mercury-free lamp

International Nuclear Information System (INIS)

Ouyang, Jiting; He, Feng; Miao, Jinsong; Wang, Jianqi; Hu, Wenbo

2007-01-01

In this paper, the numerical study has been performed on the xenon positive column discharges of mercury-free fluorescent lamp. The plasma discharge characteristics are analyzed by numerical simulation based on two-dimensional fluid model. The effects of cell geometry, such as the dielectric layer, the electrode width, the electrode gap, and the cell height, and the filling gas including the pressure and the xenon percentage are investigated in terms of discharge current and discharge efficiency. The results show that a long transient positive column will form in the xenon lamp when applying ac sinusoidal power and the lamp can operate in a large range of voltage and frequency. The front dielectric layer of the cell plays an important role in the xenon lamp while the back layer has little effect. The ratio of electrode gap to cell height should be large to achieve a long positive column xenon lamp and higher efficiency. Increase of pressure or xenon concentration results in an increase of discharge efficiency and voltage. The discussions will be helpful for the design of commercial xenon lamp cells

Numerical Study of Compact Plate-Fin Heat Exchanger for Rotary-Vane Gas Refrigeration Machine

Directory of Open Access Journals (Sweden)

V. V. Trandafilov

2017-10-01

Full Text Available Plate-fin heat exchangers are widely used in refrigeration technique. They are popular because of their compactness and excellent heat transfer performance. Here we present a numerical model for the development, research and optimization of a plate-fin heat exchanger for a rotary-vane gas refrigeration machine. The method of analysis by graphic method of plate - fin heat exchanger is proposed. The model describes the effects of secondary parameters such as axial thermal conductivity through a metal matrix of the heat exchanger. The influence of geometric parameters and heat transfer coefficient is studied. Graphs of dependences of length, efficiency of a fin and pressure drop in a heat exchanger on the thickness of the fin and the number of fins per meter are obtained. To analyze the results of numerical simulation, the heat exchanger was designed in the Aspen HYSYS program. The simulation results show that the total deviation from the proposed numerical model is not more than 15%. 

Proceeding of 1999-workshop on MHD computations 'study on numerical methods related to plasma confinement'

Energy Technology Data Exchange (ETDEWEB)

Kako, T.; Watanabe, T. [eds.

2000-06-01

This is the proceeding of 'study on numerical methods related to plasma confinement' held in National Institute for Fusion Science. In this workshop, theoretical and numerical analyses of possible plasma equilibria with their stability properties are presented. There are also various lectures on mathematical as well as numerical analyses related to the computational methods for fluid dynamics and plasma physics. Separate abstracts were presented for 13 of the papers in this report. The remaining 6 were considered outside the subject scope of INIS. (J.P.N.)

Numerical study of the bubbly flow regime in micro-channel flow boiling

Science.gov (United States)

Bhuvankar, Pramod; Dabiri, Sadegh

2017-11-01

Two-phase flow accompanied by boiling in micro-channel heat sinks is an effective means for heat removal from computer chips. We present a numerical study of flow boiling in micro-channels with conjugate heat transfer with a focus on the bubbly flow regime. The bubbles are assumed to nucleate at a pre-determined location and frequency. The Navier Stokes equations are solved using a single fluid formulation with the Front tracking method. Phase change is implemented using the deficit in heat flux across the bubble interface. The analytical solution for bubble growth in a superheated liquid is used as a benchmark to validate the mentioned numerical method. Water and FC-72 are studied as the operating fluids in a micro-channel made of Copper with a focus on hotspot mitigation. The micro-channel of cross-section 231 μm × 1000 μm , is used to study the effects of vertical up-flow, vertical down-flow and horizontal flow of the mentioned fluids on the heat transfer coefficients. A simple film model accounting for mass and energy conservation is applied wherever the bubble approaches closer than a cell width to the wall. The results of the simulation are compared with existing experimental data for bubble growth rates and heat transfer coefficients.

Hydration of mineral shrinkage-compensating admixture for concrete : an experimental and numerical study

NARCIS (Netherlands)

Chen, Wei; Brouwers, H.J.H.

2012-01-01

The use of shrinkage-compensating admixture in concrete has been proven to be an effective way to mitigate the shrinkage of concrete. The hydration of a shrinkage-compensating admixture in cement paste and concrete is investigated in this paper with numerical simulation and experimental study. An

A Numerical Study on Premixed Bluff Body Flame of Different Bluff Apex Angle

Directory of Open Access Journals (Sweden)

Gelan Yang

2013-01-01

Full Text Available In order to investigate effects of apex angle (α on chemically reacting turbulent flow and thermal fields in a channel with a bluff body V-gutter flame holder, a numerical study has been carried out in this paper. With a basic geometry used in a previous experimental study, the apex angle was varied from 45° to 150°. Eddy dissipation concept (EDC combustion model was used for air and propane premixed flame. LES-Smagorinsky model was selected for turbulence. The gird-dependent learning and numerical model verification were done. Both nonreactive and reactive conditions were analyzed and compared. The results show that as α increases, recirculation zone becomes bigger, and Strouhal number increases a little in nonreactive cases while decreases a little in reactive cases, and the increase of α makes the flame shape wider, which will increase the chamber volume heat release ratio and enhance the flame stability.

Numerical taxonomic study of some tribes of composite (subfamily asteroideae) from Egypt

Energy Technology Data Exchange (ETDEWEB)

Osman, A K [South Valley University, Faculty of Science, Qena (Egypt). Dept. of Botany

2011-02-15

A systematic study of 25 taxa belonging to 12 genera of tribes Gnaphalieae, Helenieae, Plucheeae and Senecioneae of Compositae from Egypt was conducted by means of numerical analysis based on 19 main pollen grains characters. On the basis of UPGMA (Unpaired Group Method off Averaging) clustering and PCO (Principal Component Analysis), two main groups and five subgroups are recognized. (author)

Numerical taxonomic study of some tribes of composite (subfamily asteroideae) from Egypt

International Nuclear Information System (INIS)

Osman, A.K.

2011-01-01

A systematic study of 25 taxa belonging to 12 genera of tribes Gnaphalieae, Helenieae, Plucheeae and Senecioneae of Compositae from Egypt was conducted by means of numerical analysis based on 19 main pollen grains characters. On the basis of UPGMA (Unpaired Group Method off Averaging) clustering and PCO (Principal Component Analysis), two main groups and five subgroups are recognized. (author)

Developmental specialization of the left parietal cortex for the semantic representation of Arabic numerals: An fMR-adaptation study

Directory of Open Access Journals (Sweden)

Stephan E. Vogel

2015-04-01

Full Text Available The way the human brain constructs representations of numerical symbols is poorly understood. While increasing evidence from neuroimaging studies has indicated that the intraparietal sulcus (IPS becomes increasingly specialized for symbolic numerical magnitude representation over developmental time, the extent to which these changes are associated with age-related differences in symbolic numerical magnitude representation or with developmental changes in non-numerical processes, such as response selection, remains to be uncovered. To address these outstanding questions we investigated developmental changes in the cortical representation of symbolic numerical magnitude in 6- to 14-year-old children using a passive functional magnetic resonance imaging adaptation design, thereby mitigating the influence of response selection. A single-digit Arabic numeral was repeatedly presented on a computer screen and interspersed with the presentation of novel digits deviating as a function of numerical ratio (smaller/larger number. Results demonstrated a correlation between age and numerical ratio in the left IPS, suggesting an age-related increase in the extent to which numerical symbols are represented in the left IPS. Brain activation of the right IPS was modulated by numerical ratio but did not correlate with age, indicating hemispheric differences in IPS engagement during the development of symbolic numerical representation.

Numerical study of a mathematical model of internal erosion of soil

Science.gov (United States)

Sibin, A.

2017-10-01

The process of internal erosion in a three-phase saturated soil is studied. A mathematical model describing the process consists of the equations of mass conservation, Darcy’s law and equation for capillary pressure. The original system of equations is reduced to a system of three equations for porosity, pressure and water saturation. Obtained equation for the water saturation is degenerate. The degenerate problem in an one-dimensional domain is solved numerically using the finite-difference method.

Continuous modelling study of numerical volumes - Applications to the visualization of anatomical structures

International Nuclear Information System (INIS)

Goret, C.

1990-12-01

Several technics of imaging (IRM, image scanners, tomoscintigraphy, echography) give numerical informations presented by means of a stack of parallel cross-sectional images. Since many years, 3-D mathematical tools have been developed and allow the 3 D images synthesis of surfaces. In first part, we give the technics of numerical volume exploitation and their medical applications to diagnosis and therapy. The second part is about a continuous modelling of the volume with a tensor product of cubic splines. We study the characteristics of this representation and its clinical validation. Finally, we treat of the problem of surface visualization of objects contained in the volume. The results show the interest of this model and allow to propose specifications for 3-D workstation realization [fr

Numerical study on the hydrodynamic characteristics of biofouled full-scale net cage

Science.gov (United States)

Bi, Chun-wei; Zhao, Yun-peng; Dong, Guo-hai

2015-06-01

The effect of biofouling on the hydrodynamic characteristics of the net cage is of particular interest as biofouled nettings can significantly reduce flow of well-oxygenated water reaching the stocked fish. For computational efficiency, the porous-media fluid model is proposed to simulate flow through the biofouled plane net and full-scale net cage. The porous coefficients of the porous-media fluid model can be determined from the quadratic-function relationship between the hydrodynamic forces on a plane net and the flow velocity using the least squares method. In this study, drag forces on and flow fields around five plane nets with different levels of biofouling are calculated by use of the proposed model. The numerical results are compared with the experimental data of Swift et al. (2006) and the effectiveness of the numerical model is presented. On that basis, flow through full-scale net cages with the same level of biofouling as the tested plane nets are modeled. The flow fields inside and around biofouled net cages are analyzed and the drag force acting on a net cage is estimated by a control volume analysis method. According to the numerical results, empirical formulas of reduction in flow velocity and load on a net cage are derived as function of drag coefficient of the corresponding biofouled netting.

Numerical study of the Columbia high-beta device: Torus-II

Energy Technology Data Exchange (ETDEWEB)

Izzo, R.

1981-01-01

The ionization, heating and subsequent long-time-scale behavior of the helium plasma in the Columbia fusion device, Torus-II, is studied. The purpose of this work is to perform numerical simulations while maintaining a high level of interaction with experimentalists. The device is operated as a toroidal z-pinch to prepare the gas for heating. This ionization of helium is studied using a zero-dimensional, two-fluid code. It is essentially an energy balance calculation that follows the development of the various charge states of the helium and any impurities (primarily silicon and oxygen) that are present. The code is an atomic physics model of Torus-II. In addition to ionization, we include three-body and radiative recombination processes.

Numerical study of the Columbia high-beta device: Torus-II

International Nuclear Information System (INIS)

Izzo, R.

1981-01-01

The ionization, heating and subsequent long-time-scale behavior of the helium plasma in the Columbia fusion device, Torus-II, is studied. The purpose of this work is to perform numerical simulations while maintaining a high level of interaction with experimentalists. The device is operated as a toroidal z-pinch to prepare the gas for heating. This ionization of helium is studied using a zero-dimensional, two-fluid code. It is essentially an energy balance calculation that follows the development of the various charge states of the helium and any impurities (primarily silicon and oxygen) that are present. The code is an atomic physics model of Torus-II. In addition to ionization, we include three-body and radiative recombination processes

Numerical study of a PCM-air heat exchanger's thermal performance

Science.gov (United States)

Herbinger, F.; Bhouri, M.; Groulx, D.

2016-09-01

In this paper, the use of PCMs in HVAC applications is investigated by studying numerically the thermal performance of a PCM-air heat exchanger. The PCM used in this study is dodecanoic acid. A symmetric 3D model, incorporating conductive and convective heat transfer (air only) as well as laminar flow, was created in COMSOL Multiphysics 5.0. Simulations examined the dependence of the heat transfer rate on the temperature and velocity of the incoming air as well as the size of the channels in the heat exchanger. Results indicated that small channels size lead to a higher heat transfer rates. A similar trend was also obtained for high incoming air temperature, whereas the heat transfer rate was less sensitive to the incoming air velocity.

Numerical Simulation of Cyclic Thermodynamic Processes

DEFF Research Database (Denmark)

Andersen, Stig Kildegård

2006-01-01

This thesis is on numerical simulation of cyclic thermodynamic processes. A modelling approach and a method for finding periodic steady state solutions are described. Examples of applications are given in the form of four research papers. Stirling machines and pulse tube coolers are introduced...... and a brief overview of the current state of the art in methods for simulating such machines is presented. It was found that different simulation approaches, which model the machines with different levels of detail, currently coexist. Methods using many simplifications can be easy to use and can provide...... models flexible and easy to modify, and to make simulations fast. A high level of accuracy was achieved for integrations of a model created using the modelling approach; the accuracy depended on the settings for the numerical solvers in a very predictable way. Selection of fast numerical algorithms...

Introduction to numerical methods for time dependent differential equations

CERN Document Server

Kreiss, Heinz-Otto

2014-01-01

Introduces both the fundamentals of time dependent differential equations and their numerical solutions Introduction to Numerical Methods for Time Dependent Differential Equations delves into the underlying mathematical theory needed to solve time dependent differential equations numerically. Written as a self-contained introduction, the book is divided into two parts to emphasize both ordinary differential equations (ODEs) and partial differential equations (PDEs). Beginning with ODEs and their approximations, the authors provide a crucial presentation of fundamental notions, such as the t

Numerical study of turbulent flow in a rectangular T-junction

Science.gov (United States)

Georgiou, Michail; Papalexandris, Miltiadis V.

2017-06-01

In this paper, we report on a numerical study of the interaction and merging of a turbulent crossflow with an incoming turbulent jet in a T-junction with rectangular cross section. Our study is based on wall-resolved and experimentally validated large eddy simulations. The bulk Reynolds number of the crossflow is 15 000. Further, we consider cases with two different momentum ratios, namely, MR = 2 and MR = 0.5. In the presentation of the results, we elaborate on the main features of the flow, namely, the shear layers that emanate from the corners of the entry of the jet, the large recirculation bubble downstream the incoming jet, and the mixing process beyond the reattachment point. For validation purposes, we compare our simulations with existing experimental data. This comparison shows a good agreement between our numerical predictions and the measurements. First- and second-order statistics of the flow are also presented and analyzed in detail. Our simulations reveal two features of the flow that have not been reported before in studies of T-junctions. The first one is a secondary small-scale recirculation region between the entry of the jet and the large recirculation bubble. The second one is the negative turbulent kinetic energy production that occurs in the recirculation bubble and close to the reattachment of the flow. The analysis of our results further reveals that just across the entry of the jet, the boundary layer in the wall opposite to the jet experiences a favourable pressure gradient due to a Venturi effect induced by the incoming jet. In turn, this favourable pressure gradient contributes to the local relaminarization of the flow. On the other hand, the boundary layer downstream the recirculation bubble experiences an adverse pressure gradient. In both cases, a significant deviation from the universal law of the wall is confirmed.

Numerical investigation on exterior conformal mappings with application to airfoils

International Nuclear Information System (INIS)

Mohamad Rashidi Md Razali; Hu Laey Nee

2000-01-01

A numerical method is described in computing a conformal map from an exterior region onto the exterior of the unit disk. The numerical method is based on a boundary integral equation which is similar to the Kerzman-Stein integral equation for interior mapping. Some examples show that numerical results of high accuracy can be obtained provided that the boundaries are smooth. This numerical method has been applied to the mapping airfoils. However, due to the fact that the parametric representation of an air foil is not known, a cubic spline interpolation method has been used. Some numerical examples with satisfying results have been obtained for the symmetrical and cambered airfoils. (Author)

Numerical simulation of laser resonators

International Nuclear Information System (INIS)

Yoo, J. G.; Jeong, Y. U.; Lee, B. C.; Rhee, Y. J.; Cho, S. O.

2004-01-01

We developed numerical simulation packages for laser resonators on the bases of a pair of integral equations. Two numerical schemes, a matrix formalism and an iterative method, were programmed for finding numeric solutions to the pair of integral equations. The iterative method was tried by Fox and Li, but it was not applicable for high Fresnel numbers since the numerical errors involved propagate and accumulate uncontrollably. In this paper, we implement the matrix method to extend the computational limit further. A great number of case studies are carried out with various configurations of stable and unstable r;esonators to compute diffraction losses, phase shifts, intensity distributions and phases of the radiation fields on mirrors. Our results presented in this paper show not only a good agreement with the results previously obtained by Fox and Li, but also the legitimacy of our numerical procedures for high Fresnel numbers.

A numerical study of the Regge calculus and smooth lattice methods on a Kasner cosmology

International Nuclear Information System (INIS)

Brewin, Leo

2015-01-01

Two lattice based methods for numerical relativity, the Regge calculus and the smooth lattice relativity, will be compared with respect to accuracy and computational speed in a full 3+1 evolution of initial data representing a standard Kasner cosmology. It will be shown that both methods provide convergent approximations to the exact Kasner cosmology. It will also be shown that the Regge calculus is of the order of 110 times slower than the smooth lattice method. (paper)

Numerical calculations in quantum field theories

International Nuclear Information System (INIS)

Rebbi, C.

1984-01-01

Four lecture notes are included: (1) motivation for numerical calculations in Quantum Field Theory; (2) numerical simulation methods; (3) Monte Carlo studies of Quantum Chromo Dynamics; and (4) systems with fermions. 23 references

Experimental and numerical studies in a vortex tube

International Nuclear Information System (INIS)

Sohn, Chang Hyun; Kim, Chang Soo; Gowda, B. H. L Lakshmana; Jung, Ui Hyun

2006-01-01

The present investigation deals with the study of the internal flow phenomena of the counter-flow type vortex tube using experimental testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure was varied from 0.1 MPa to 0.3 MPa. The experimentally visualized results on the tube show that there is an apparent sudden changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar to that observed in experiments

Numerical modeling and experimental validation of thermoplastic composites induction welding

Science.gov (United States)

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.

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...

Interferometric and numerical study of the temperature field in the boundary layer and heat transfer in subcooled flow boiling

Energy Technology Data Exchange (ETDEWEB)

Lucic, Anita; Emans, Maximilian; Mayinger, Franz; Zenger, Christoph

2004-04-01

An interferometric study and a numerical simulation are presented of the combined process of the bulk turbulent convection and the dynamic of a vapor bubble which is formed in the superheated boundary layer of a subcooled flowing liquid, in order to determine the heat transfer to the flowing subcooled liquid. In this investigation focus has been given on a single vapor bubble at a defined cavity site to provide reproducible conditions. In the experimental study single bubbles were generated at a single artificial cavity by means of a CO{sub 2}-laser as a spot heater at a uniformly heated wall of a vertical rectangular channel with water as the test fluid. The experiments were performed at various degrees of subcooling and mass flow rates. The bubble growth and the temporal decrease of the bubble volume were captured by means of the high-speed cinematography. The thermal boundary layer and the temperature field at the phase-interface between fluid and bubble were visualized by means of the optical measurement method holographic interferometry with a high temporal and spatial resolution, and thus the local and temporal heat transfer could be quantified. The experimental results form a significant data basis for the description of the mean as well as the local heat transfer as a function of the flow conditions. According to the experimental configuration and the obtained data the numerical simulations were performed. A numerical method has been developed to simulate the influence of single bubbles on the surrounding fluid which is based on a Lagrangian approach to describe the motion of the bubbles. The method is coupled to a large-eddy simulations by the body force term which is locally evaluated based on the density field. The obtained experimental data correspond well with the numerical predictions, both of which demonstrate the thermo- and fluiddynamic characteristics of the interaction between the vapor bubble and the subcooled liquid.

Interferometric and numerical study of the temperature field in the boundary layer and heat transfer in subcooled flow boiling

International Nuclear Information System (INIS)

Lucic, Anita; Emans, Maximilian; Mayinger, Franz; Zenger, Christoph

2004-01-01

An interferometric study and a numerical simulation are presented of the combined process of the bulk turbulent convection and the dynamic of a vapor bubble which is formed in the superheated boundary layer of a subcooled flowing liquid, in order to determine the heat transfer to the flowing subcooled liquid. In this investigation focus has been given on a single vapor bubble at a defined cavity site to provide reproducible conditions. In the experimental study single bubbles were generated at a single artificial cavity by means of a CO 2 -laser as a spot heater at a uniformly heated wall of a vertical rectangular channel with water as the test fluid. The experiments were performed at various degrees of subcooling and mass flow rates. The bubble growth and the temporal decrease of the bubble volume were captured by means of the high-speed cinematography. The thermal boundary layer and the temperature field at the phase-interface between fluid and bubble were visualized by means of the optical measurement method holographic interferometry with a high temporal and spatial resolution, and thus the local and temporal heat transfer could be quantified. The experimental results form a significant data basis for the description of the mean as well as the local heat transfer as a function of the flow conditions. According to the experimental configuration and the obtained data the numerical simulations were performed. A numerical method has been developed to simulate the influence of single bubbles on the surrounding fluid which is based on a Lagrangian approach to describe the motion of the bubbles. The method is coupled to a large-eddy simulations by the body force term which is locally evaluated based on the density field. The obtained experimental data correspond well with the numerical predictions, both of which demonstrate the thermo- and fluiddynamic characteristics of the interaction between the vapor bubble and the subcooled liquid

Experimental and Numerical Investigation of Ablation Kinetics

Data.gov (United States)

National Aeronautics and Space Administration — The University of Vermont (UVM) and the University of Michigan (UMI) propose a 2-year experimental and numerical research effort aimed at providing critically needed...

Study on the wind field and pollutant dispersion in street canyons using a stable numerical method.

Science.gov (United States)

Xia, Ji-Yang; Leung, Dennis Y C

2005-01-01

A stable finite element method for the time dependent Navier-Stokes equations was used for studying the wind flow and pollutant dispersion within street canyons. A three-step fractional method was used to solve the velocity field and the pressure field separately from the governing equations. The Streamline Upwind Petrov-Galerkin (SUPG) method was used to get stable numerical results. Numerical oscillation was minimized and satisfactory results can be obtained for flows at high Reynolds numbers. Simulating the flow over a square cylinder within a wide range of Reynolds numbers validates the wind field model. The Strouhal numbers obtained from the numerical simulation had a good agreement with those obtained from experiment. The wind field model developed in the present study is applied to simulate more complex flow phenomena in street canyons with two different building configurations. The results indicated that the flow at rooftop of buildings might not be assumed parallel to the ground as some numerical modelers did. A counter-clockwise rotating vortex may be found in street canyons with an inflow from the left to right. In addition, increasing building height can increase velocity fluctuations in the street canyon under certain circumstances, which facilitate pollutant dispersion. At high Reynolds numbers, the flow regimes in street canyons do not change with inflow velocity.

Numerical Study of Instabilities Driven by Energetic Neutral Beam Ions in NSTX

International Nuclear Information System (INIS)

Belova, E.V.; Gorelenkov, N.N.; Cheng, C.Z.; Fredrickson, E.D.

2003-01-01

Recent experimental observations from NSTX [National Spherical Torus Experiment] suggest that many modes in a subcyclotron frequency range are excited during neutral-beam injection (NBI). These modes have been identified as Compressional Alfven Eigenmodes (CAEs) and Global Alfven Eigenmodes (GAEs), which are driven unstable through the Doppler-shifted cyclotron resonance with the beam ions. The injection velocities of the NBI ions in NSTX are large compared to Alfven velocity, V(sub)0 > 3V(sub)A, and a strong anisotropy in the fast-ion pitch-angle distribution provides the energy source for the instabilities. Recent interest in the excitation of Alfven Eigenmodes in the frequency range omega less than or approximately equal to omega(sub)ci, where omega(sub)ci is the ion cyclotron frequency, is related to the possibility that these modes can provide a mechanism for direct energy transfer from super-Alfvenic beam ions to thermal ions. Numerical simulations are required in order to find a self-consistent mode structure, and to include the effects of finite-Larmor radius (FLR), the nonlinear effects, and the thermal plasma kinetic effects

Analytical and numerical study of microswimming using the 'bead-spring model'

OpenAIRE

Pande, Jayant

2016-01-01

In this thesis we use the bead-spring microswimmer design as a model system to study mechanical microswimming. The basic form of such a swimmer was introduced as the 'three-sphere swimmer' in Najafi & Golestanian, Phys. Rev. E (2004) and has found wide use in theoretical, numerical and experimental research. In our work, we have modified and extended the model in various ways, which, as explained in this thesis, allow us to gain insight into many general principles of microswimming, for insta...

Numerical and experimental study on the steady cone-jet mode of electro-centrifugal spinning

Science.gov (United States)

Hashemi, Ali Reza; Pishevar, Ahmad Reza; Valipouri, Afsaneh; Pǎrǎu, Emilian I.

2018-01-01

This study focuses on a numerical investigation of an initial stable jet through the air-sealed electro-centrifugal spinning process, which is known as a viable method for the mass production of nanofibers. A liquid jet undergoing electric and centrifugal forces, as well as other forces, first travels in a stable trajectory and then goes through an unstable curled path to the collector. In numerical modeling, hydrodynamic equations have been solved using the perturbation method—and the boundary integral method has been implemented to efficiently solve the electric potential equation. Hydrodynamic equations have been coupled with the electric field using stress boundary conditions at the fluid-fluid interface. Perturbation equations were discretized by a second order finite difference method, and the Newton method was implemented to solve the discretized non-linear system. Also, the boundary element method was utilized to solve electrostatic equations. In the theoretical study, the fluid was described as a leaky dielectric with charges only on the surface of the jet traveling in dielectric air. The effect of the electric field induced around the nozzle tip on the jet instability and trajectory deviation was also experimentally studied through plate-plate geometry as well as point-plate geometry. It was numerically found that the centrifugal force prevails on electric force by increasing the rotational speed. Therefore, the alteration of the applied voltage does not significantly affect the jet thinning profile or the jet trajectory.

Numerical Relativity for Space-Based Gravitational Wave Astronomy

Science.gov (United States)

Baker, John G.

2011-01-01

In the next decade, gravitational wave instruments in space may provide high-precision measurements of gravitational-wave signals from strong sources, such as black holes. Currently variations on the original Laser Interferometer Space Antenna mission concepts are under study in the hope of reducing costs. Even the observations of a reduced instrument may place strong demands on numerical relativity capabilities. Possible advances in the coming years may fuel a new generation of codes ready to confront these challenges.

A delta-rule model of numerical and non-numerical order processing.

Science.gov (United States)

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.

Numerical Simulation of Polynomial-Speed Convergence Phenomenon

Science.gov (United States)

Li, Yao; Xu, Hui

2017-11-01

We provide a hybrid method that captures the polynomial speed of convergence and polynomial speed of mixing for Markov processes. The hybrid method that we introduce is based on the coupling technique and renewal theory. We propose to replace some estimates in classical results about the ergodicity of Markov processes by numerical simulations when the corresponding analytical proof is difficult. After that, all remaining conclusions can be derived from rigorous analysis. Then we apply our results to seek numerical justification for the ergodicity of two 1D microscopic heat conduction models. The mixing rate of these two models are expected to be polynomial but very difficult to prove. In both examples, our numerical results match the expected polynomial mixing rate well.

Numerical study and ex vivo assessment of HIFU treatment time reduction through optimization of focal point trajectory

Science.gov (United States)

Grisey, A.; Yon, S.; Pechoux, T.; Letort, V.; Lafitte, P.

2017-03-01

Treatment time reduction is a key issue to expand the use of high intensity focused ultrasound (HIFU) surgery, especially for benign pathologies. This study aims at quantitatively assessing the potential reduction of the treatment time arising from moving the focal point during long pulses. In this context, the optimization of the focal point trajectory is crucial to achieve a uniform thermal dose repartition and avoid boiling. At first, a numerical optimization algorithm was used to generate efficient trajectories. Thermal conduction was simulated in 3D with a finite difference code and damages to the tissue were modeled using the thermal dose formula. Given an initial trajectory, the thermal dose field was first computed, then, making use of Pontryagin's maximum principle, the trajectory was iteratively refined. Several initial trajectories were tested. Then, an ex vivo study was conducted in order to validate the efficicency of the resulting optimized strategies. Single pulses were performed at 3MHz on fresh veal liver samples with an Echopulse and the size of each unitary lesion was assessed by cutting each sample along three orthogonal planes and measuring the dimension of the whitened area based on photographs. We propose a promising approach to significantly shorten HIFU treatment time: the numerical optimization algorithm was shown to provide a reliable insight on trajectories that can improve treatment strategies. The model must now be improved in order to take in vivo conditions into account and extensively validated.

An experimental and numerical study of confined non-reacting and reacting turbulent jets to facilitate homogeneous combustion in industrial furnaces

Science.gov (United States)

Lee, Insu

Confined non-reacting turbulent jets are ideal for recirculating the hot flue gas back into the furnace from an external exhaust duct. Such jets are also used inside the furnace to internally entrain and recirculate the hot flue gas to preheat and dilute the reactants. Both internal and external implementation of confined turbulent jets increase the furnace thermal efficiency. For external implementation, depending on the circumstances, the exhaust gas flow may be co- or counter-flow relative to the jet flow. Inside the furnaces, fuel and air jets are injected separately. To create a condition which can facilitate near homogeneous combustion, these jets have to first mix with the burned gas inside the furnace and simultaneously being heated and diluted prior to combustion. Clearly, the combustion pattern and emissions from reacting confined turbulent jets are affected by jet interactions, mixing and entrainment of hot flue gas. In this work, the flow and mixing characteristics of a non-reacting and reacting confined turbulent jet are investigated experimentally and numerically. This work consists of two parts: (i) A study of flow and mixing characteristics of non-reacting confined turbulent jets with co- or counter-flowing exhaust/flue gas. Here the axial and radial distributions of temperature, velocity and NO concentration (used as a tracer gas) were measured. FLUENT was used to numerically simulate the experimental results. This work provides the basic understanding of the flow and mixing characteristics of confined turbulent jets and develops some design considerations for recirculating flue gas back into the furnace as expressed by the recirculation zone and the stagnation locations. (ii) Numerical calculations of near homogeneous combustion are performed for the existing furnace. The exact geometry of the furnace in the lab is used and the real dimensional boundary conditions are considered. The parameters such as air nozzle diameter (dair), fuel nozzle

Drag Reduction by Riblets & Sharkskin Denticles: A Numerical Study

Science.gov (United States)

Boomsma, Aaron

Riblet films are a passive method of turbulent boundary layer control that can reduce viscous drag. They have been studied with great detail for over 30 years. Although common riblet applications include flows with Adverse Pressure Gradients (APG), nearly all research thus far has been performed in channel flows. Recent research has provided motivation to study riblets in more complicated turbulent flows with claims that riblet drag reduction can double in mild APG common to airfoils at moderate angles of attack. Therefore, in this study, we compare drag reduction by scalloped riblet films between riblets in a zero pressure gradient and those in a mild APG using high-resolution large eddy simulations. In order to gain a fundamental understanding of the relationship between drag reduction and pressure gradient, we simulated several different riblet sizes that encompassed a broad range of s + (riblet width in wall units), similarly to many experimental studies. We found that there was only a slight improvement in drag reduction for riblets in the mild APG. We also observed that peak values of streamwise turbulence intensity, turbulent kinetic energy, and streamwise vorticity scale with riblet width. Primary Reynolds shear stresses and turbulence kinetic energy production however scale with the ability of the riblet to reduce skin-friction. Another turbulent roughness of similar shape and size to riblets is sharkskin. The hydrodynamic function of sharkskin has been under investigation for the past 30 years. Current literature conflicts on whether sharkskin is able to reduce skin friction similarly to riblets. To contribute insights toward reconciling these conflicting views, Direct Numerical Simulations (DNS) are carried out to obtain detailed flow fields around realistic denticles. A sharp interface immersed boundary method is employed to simulate two arrangements of actual sharkskin denticles (from Isurus oxyrinchus) in a turbulent boundary layer at Retau ≈ 180

Experimental and numerical study of flow deflection effects on electronic air-cooling

International Nuclear Information System (INIS)

Arfaoui, Ahlem; Ben Maad, Rejeb; Hammami, Mahmoud; Rebay, Mourad; Padet, Jacques

2009-01-01

This work present a numerical and experimental investigation of the influence of transversal flow deflector on the cooling of a heated block mounted on a flat plate. The deflector is inclined and therefore it guides the air flow to the upper surface of the block. This situation is simulating the air-cooling of a rectangular integrated circuit or a current converter mounted on an electronic board. The electronic component are assumed dissipating a low or medium heat flux (with a density lower than 5000 W/m 2 ), as such the forced convection air cooling without fan or heat sink is still sufficient. The study details the effects of the angle of deflector on the temperature and the heat transfer coefficient along the surface of the block and around it. The results of the numerical simulations and the InfraRed camera measurements show that the deviation caused by deflector may significantly enhance the heat transfer on the top face of block

Atmospheric models in the numerical simulation system (SPEEDI-MP) for environmental studies

International Nuclear Information System (INIS)

Nagai, Haruyasu; Terada, Hiroaki

2007-01-01

As a nuclear emergency response system, numerical models to predict the atmospheric dispersion of radionuclides have been developed at Japan Atomic Energy Agency (JAEA). Evolving these models by incorporating new schemes for physical processes and up-to-date computational technologies, a numerical simulation system, which consists of dynamical models and material transport models for the atmospheric, terrestrial, and oceanic environments, has been constructed to apply for various environmental studies. In this system, the combination of a non-hydrostatic atmospheric dynamic model and Lagrangian particle dispersion model is used for the emergency response system. The utilization of detailed meteorological field by the atmospheric model improves the model performance for diffusion and deposition calculations. It also calculates a large area domain with coarse resolution and local area domain with high resolution simultaneously. The performance of new model system was evaluated using measurements of surface deposition of 137 Cs over Europe during the Chernobyl accident. (author)

Numerical study of corner separation in a linear compressor cascade using various turbulence models

Directory of Open Access Journals (Sweden)

Liu Yangwei

2016-06-01

Full Text Available Three-dimensional corner separation is a common phenomenon that significantly affects compressor performance. Turbulence model is still a weakness for RANS method on predicting corner separation flow accurately. In the present study, numerical study of corner separation in a linear highly loaded prescribed velocity distribution (PVD compressor cascade has been investigated using seven frequently used turbulence models. The seven turbulence models include Spalart–Allmaras model, standard k–ɛ model, realizable k–ɛ model, standard k–ω model, shear stress transport k–ω model, v2–f model and Reynolds stress model. The results of these turbulence models have been compared and analyzed in detail with available experimental data. It is found the standard k–ɛ model, realizable k–ɛ model, v2–f model and Reynolds stress model can provide reasonable results for predicting three dimensional corner separation in the compressor cascade. The Spalart–Allmaras model, standard k–ω model and shear stress transport k–ω model overestimate corner separation region at incidence of 0°. The turbulence characteristics are discussed and turbulence anisotropy is observed to be stronger in the corner separating region.

Numerical and experimental study of actuator performance on piezoelectric microelectromechanical inkjet print head.

Science.gov (United States)

Van So, Pham; Jun, Hyun Woo; Lee, Jaichan

2013-12-01

We have investigated the actuator performance of a piezoelectrically actuated inkjet print head via the numerical and experimental analysis. The actuator consisting of multi-layer membranes, such as piezoelectric, elastic and other buffer layers, and ink chamber was fabricated by MEMS processing. The maximum displacement of the actuator membrane obtained in the experiment is explained by numerical analysis. A simulation of the actuator performance with fluidic damping shows that the resonant frequency of the membrane in liquid is reduced from its resonant frequency in air by a factor of three, which was also verified in the experiment. These simulation and experimental studies demonstrate how much "dynamic force," in terms of a membrane's maximum displacement, maximum force and driving frequency, can be produced by an actuator membrane interacting with fluid.

Two-Dimensional Numerical Study on the Migration of Particle in a Serpentine Channel

Directory of Open Access Journals (Sweden)

Yi Liu

2018-01-01

Full Text Available In this work, the momentum exchange scheme-based lattice Boltzmann method is adopted to numerically study the migration of a circular particle in a serpentine channel for the range of 20 ≤ Re ≤ 120. The effects of the Reynolds number, particle density, and the initial particle position are taken into account. Numerical results include the streamlines, particle trajectories, and final equilibrium positions. Close attention is also paid to the time it takes for the particle to travel in the channel. It has been found that the particle is likely to migrate to a similar equilibrium position irrespective of its initial position when Re is large. Furthermore, there exists a critical solid-to-fluid density ratio for which the particle travels fastest in the channel.

Numerical simulation of realistic high-temperature superconductors

International Nuclear Information System (INIS)

1997-01-01

One of the main obstacles in the development of practical high-temperature superconducting (HTS) materials is dissipation, caused by the motion of magnetic flux quanta called vortices. Numerical simulations provide a promising new approach for studying these vortices. By exploiting the extraordinary memory and speed of massively parallel computers, researchers can obtain the extremely fine temporal and spatial resolution needed to model complex vortex behavior. The results may help identify new mechanisms to increase the current-capability capabilities and to predict the performance characteristics of HTS materials intended for industrial applications

Numerical analysis of anisotropic diffusion effect on ICF hydrodynamic instabilities

Directory of Open Access Journals (Sweden)

Olazabal-Loumé M.

2013-11-01

Full Text Available The effect of anisotropic diffusion on hydrodynamic instabilities in the context of Inertial Confinement Fusion (ICF flows is numerically assessed. This anisotropy occurs in indirect-drive when laminated ablators are used to modify the lateral transport [1,2]. In direct-drive, non-local transport mechanisms and magnetic fields may modify the lateral conduction [3]. In this work, numerical simulations obtained with the code PERLE [4], dedicated to linear stability analysis, are compared with previous theoretical results [5]. In these approaches, the diffusion anisotropy can be controlled by a characteristic coefficient which enables a comprehensive study. This work provides new results on the ablative Rayleigh-Taylor (RT, ablative Richtmyer-Meshkov (RM and Darrieus-Landau (DL instabilities.

Playing Linear Numerical Board Games Promotes Low-Income Children's Numerical Development

Science.gov (United States)

Siegler, Robert S.; Ramani, Geetha B.

2008-01-01

The numerical knowledge of children from low-income backgrounds trails behind that of peers from middle-income backgrounds even before the children enter school. This gap may reflect differing prior experience with informal numerical activities, such as numerical board games. Experiment 1 indicated that the numerical magnitude knowledge of…

Data Shuffling--A New Masking Approach for Numerical Data

OpenAIRE

Krishnamurty Muralidhar; Rathindra Sarathy

2006-01-01

This study discusses a new procedure for masking confidential numerical data--a procedure called data shuffling--in which the values of the confidential variables are "shuffled" among observations. The shuffled data provides a high level of data utility and minimizes the risk of disclosure. From a practical perspective, data shuffling overcomes reservations about using perturbed or modified confidential data because it retains all the desirable properties of perturbation methods and performs ...

Dry powder segregation and flowability: Experimental and numerical studies

Science.gov (United States)

Ely, David R.

Dry powder blending is a very important industrial and physical process used in the production of numerous pharmaceutical dosage forms such as tablets, capsules, and dry powder aerosols. Key aspects of this unit operation are process monitoring and control. Process control is particularly difficult due to the complexity of particle-particle interactions, which arise from the adhesion/cohesion characteristics of interfaces and morphological characteristics such as particle size, shape, and dispersity. The effects of such characteristics need to be understood in detail in order to correlate individual particle properties to bulk powder properties. The present dissertation numerically and experimentally quantifies the mixing process to rationalize particle-particle interactions. In particular, near infrared spectroscopy (NIRS) was used to non-invasively characterize in real-time the blending processes and thus investigate the dynamics of blending under different operating conditions. A novel image analysis technique was developed to quantify the scale of segregation from images obtained non-destructively via near infrared chemical imaging (NIR-CI). Although NIR-CI data acquisition times are too long for real-time data collection, NIR-CI has an advantage, in that it provides the spatial distribution of the drug. Therefore, NIRS and NIR-CI are complementary techniques for investigating the complex process of blending dry powders and assessing end-product quality. Additionally, the discrete element method was used to investigate the effect of powder cohesion on the packing fraction. Simulations indicated an exponential relationship between the random loose packing fraction and cohesive forces. Specifically, the packing fraction decreased asymptotically with increased ratio of cohesive force to particle weight. Thus, increasing this force ratio above a critical value has negligible impact on the packing fraction. Such result directly impacts the Hausner ratio flowability

Improving the seismic small-scale modelling by comparison with numerical methods

Science.gov (United States)

Pageot, Damien; Leparoux, Donatienne; Le Feuvre, Mathieu; Durand, Olivier; Côte, Philippe; Capdeville, Yann

2017-10-01

The potential of experimental seismic modelling at reduced scale provides an intermediate step between numerical tests and geophysical campaigns on field sites. Recent technologies such as laser interferometers offer the opportunity to get data without any coupling effects. This kind of device is used in the Mesures Ultrasonores Sans Contact (MUSC) measurement bench for which an automated support system makes possible to generate multisource and multireceivers seismic data at laboratory scale. Experimental seismic modelling would become a great tool providing a value-added stage in the imaging process validation if (1) the experimental measurement chain is perfectly mastered, and thus if the experimental data are perfectly reproducible with a numerical tool, as well as if (2) the effective source is reproducible along the measurement setup. These aspects for a quantitative validation concerning devices with piezoelectrical sources and a laser interferometer have not been yet quantitatively studied in published studies. Thus, as a new stage for the experimental modelling approach, these two key issues are tackled in the proposed paper in order to precisely define the quality of the experimental small-scale data provided by the bench MUSC, which are available in the scientific community. These two steps of quantitative validation are dealt apart any imaging techniques in order to offer the opportunity to geophysicists who want to use such data (delivered as free data) of precisely knowing their quality before testing any imaging technique. First, in order to overcome the 2-D-3-D correction usually done in seismic processing when comparing 2-D numerical data with 3-D experimental measurement, we quantitatively refined the comparison between numerical and experimental data by generating accurate experimental line sources, avoiding the necessity of geometrical spreading correction for 3-D point-source data. The comparison with 2-D and 3-D numerical modelling is based on

The Behaviour of Fracture Growth in Sedimentary Rocks: A Numerical Study Based on Hydraulic Fracturing Processes

Directory of Open Access Journals (Sweden)

Lianchong Li

2016-03-01

Full Text Available To capture the hydraulic fractures in heterogeneous and layered rocks, a numerical code that can consider the coupled effects of fluid flow, damage, and stress field in rocks is presented. Based on the characteristics of a typical thin and inter-bedded sedimentary reservoir, China, a series of simulations on the hydraulic fracturing are performed. In the simulations, three points, i.e., (1 confining stresses, representing the effect of in situ stresses, (2 strength of the interfaces, and (3 material properties of the layers on either side of the interface, are crucial in fracturing across interfaces between two adjacent rock layers. Numerical results show that the hydrofracture propagation within a layered sequence of sedimentary rocks is controlled by changing in situ stresses, interface properties, and lithologies. The path of the hydraulic fracture is characterized by numerous deflections, branchings, and terminations. Four types of potential interaction, i.e., penetration, arrest, T-shaped branching, and offset, between a hydrofracture and an interface within the layered rocks are formed. Discontinuous composite fracture segments resulting from out-of-plane growth of fractures provide a less permeable path for fluids, gas, and oil than a continuous planar composite fracture, which are one of the sources of the high treating pressures and reduced fracture volume.

Numerical and Experimental Study of Electromagnetically Driven Vortical Flows

NARCIS (Netherlands)

Kenjeres, S.; Verdoold, J.; Tummers, M.J.; Hanjalic, K.; Kleijn, C.R.

2009-01-01

The paper reports on numerical and experimental investigations of electromagnetically driven vortical flows of an electrically conductive fluid in a generic setup. Two different configurations of permanent magnets are considered: a 3-magnet configuration in which the resulting Lorentz force is

Numerical study on transient local entropy generation in pulsating ...

Indian Academy of Sciences (India)

- soidal flow, step flow, and saw-down flow) and for varying periods. The flow and temperature fields are computed numerically with the help of the Fluent compu- tational fluid dynamics (CFD) code, and a computer program developed by us by.

Cortical bone drilling: An experimental and numerical study.

Science.gov (United States)

Alam, Khurshid; Bahadur, Issam M; Ahmed, Naseer

2014-12-16

Bone drilling is a common surgical procedure in orthopedics, dental and neurosurgeries. In conventional bone drilling process, the surgeon exerts a considerable amount of pressure to penetrate the drill into the bone tissue. Controlled penetration of drill in the bone is necessary for safe and efficient drilling. Development of a validated Finite Element (FE) model of cortical bone drilling. Drilling experiments were conducted on bovine cortical bone. The FE model of the bone drilling was based on mechanical properties obtained from literature data and additionally conducted microindentation tests on the cortical bone. The magnitude of stress in bone was found to decrease exponentially away from the lips of the drill in simulations. Feed rate was found to be the main influential factor affecting the force and torque in the numerical simulations and experiments. The drilling thrust force and torque were found to be unaffected by the drilling speed in numerical simulations. Simulated forces and torques were compared with experimental results for similar drilling conditions and were found in good agreement.CONCLUSIONS: FE schemes may be successfully applied to model complex kinematics of bone drilling process.

Combined free-stream disturbance measurements and receptivity studies in hypersonic wind tunnels by means of a slender wedge probe and direct numerical simulation

Science.gov (United States)

Wagner, Alexander; Schülein, Erich; Petervari, René; Hannemann, Klaus; Ali, Syed R. C.; Cerminara, Adriano; Sandham, Neil D.

2018-05-01

Combined free-stream disturbance measurements and receptivity studies in hypersonic wind tunnels were conducted by means of a slender wedge probe and direct numerical simulation. The study comprises comparative tunnel noise measurements at Mach 3, 6 and 7.4 in two Ludwieg tube facilities and a shock tunnel. Surface pressure fluctuations were measured over a wide range of frequencies and test conditions including harsh test environments not accessible to measurement techniques such as pitot probes and hot-wire anemometry. Quantitative results of the tunnel noise are provided in frequency ranges relevant for hypersonic boundary layer transition. In combination with the experimental studies, direct numerical simulations of the leading-edge receptivity to fast and slow acoustic waves were performed for the slender wedge probe at conditions corresponding to the experimental free-stream conditions. The receptivity to fast acoustic waves was found to be characterized by an early amplification of the induced fast mode. For slow acoustic waves an initial decay was found close to the leading edge. At all Mach numbers, and for all considered frequencies, the leading-edge receptivity to fast acoustic waves was found to be higher than the receptivity to slow acoustic waves. Further, the effect of inclination angles of the acoustic wave with respect to the flow direction was investigated. The combined numerical and experimental approach in the present study confirmed the previous suggestion that the slow acoustic wave is the dominant acoustic mode in noisy hypersonic wind tunnels.

Experimental and numerical study of a flapping tidal stream generator

Science.gov (United States)

Kim, Jihoon; Le, Tuyen Quang; Ko, Jin Hwan; Sitorus, Patar Ebenezer; Tambunan, Indra Hartarto; Kang, Taesam

2017-11-01

The tidal stream turbine is one of the systems that extract kinetic energy from tidal stream, and there are several types of the tidal stream turbine depending on its operating motion. In this research, we conduct experimental and consecutive numerical analyses of a flapping tidal stream generator with a dual configuration flappers. An experimental analysis of a small-scale prototype is conducted in a towing tank, and a numerical analysis is conducted using two-dimensional computational fluid dynamics simulations with an in-house code. Through an experimental analysis conducted while varying these factors, a high applied load and a high input arm angle were found to be advantageous. In consecutive numerical investigations with the kinematics selected from the experiments, it was found that a rear-swing flapper contributes to the total amount of power more than a front-swing flapper with a distance of two times the chord length and with a 90-degree phase difference between the two. This research was a part of the project titled `R&D center for underwater construction robotics', funded by the Ministry of Oceans and Fisheries(MOF), Korea Institute of Marine Science & Technology Promotion(KIMST,PJT200539), and Pohang City in Korea.

A Qualitative Study of Multidisciplinary Providers' Experiences With the Transfer Process for Injured Children and Ideas for Improvement.

Science.gov (United States)

Gawel, Marcie; Emerson, Beth; Giuliano, John S; Rosenberg, Alana; Minges, Karl E; Feder, Shelli; Violano, Pina; Morrell, Patricia; Petersen, Judy; Christison-Lagay, Emily; Auerbach, Marc

2018-02-01

Most injured children initially present to a community hospital, and many will require transfer to a regional pediatric trauma center. The purpose of this study was 1) to explore multidisciplinary providers' experiences with the process of transferring injured children and 2) to describe proposed ideas for process improvement. This qualitative study involved 26 semistructured interviews. Subjects were recruited from 6 community hospital emergency departments and the trauma and transport teams of a level I pediatric trauma center in New Haven, Conn. Participants (n = 34) included interprofessional providers from sending facilities, transport teams, and receiving facilities. Using the constant comparative method, a multidisciplinary team coded transcripts and collectively refined codes to generate recurrent themes across interviews until theoretical saturation was achieved. Participants reported that the transfer process for injured children is complex, stressful, and necessitates collaboration. The transfer process was perceived to involve numerous interrelated components, including professions, disciplines, and institutions. The 5 themes identified as areas to improve this transfer process included 1) Creation of a unified standard operating procedure that crosses institutions/teams, 2) Enhancing 'shared sense making' of all providers, 3) Improving provider confidence, expertise, and skills in caring for pediatric trauma transfer cases, 4) Addressing organization and environmental factors that may impede/delay transfer, and 5) Fostering institutional and personal relationships. Efforts to improve the transfer process for injured children should be guided by the experiences of and input from multidisciplinary frontline emergency providers.

Numerical study of criticality of the slab reactors with three regions in one-group transport theory

International Nuclear Information System (INIS)

Santos, A. dos.

1979-01-01

The criticality of slab reactors consisting of core, blanket, and reflector is studied numerically based on the singular-eigenfunction-expansion method in one-group transport theory. The purpose of this work is three-fold: (1) it is shown that the three-media problem can be converted, using a recently developed method, to a set of regular integral equations for the expansion coefficients, such that numerical solutions can be obtained for the first time based on an exact theory; (2) highly accurate numerical results that can serve as standards of comparison for various approximate methods are reported for representative sets of parameters; and (3) the accuracy of the P sub(N) approximation, one of the more often used methods, is analyzed compared to the exact results [pt

Experimental and Numerical Investigation of Flow Properties of Supersonic Helium-Air Jets

Science.gov (United States)

Miller, Steven A. E.; Veltin, Jeremy

2010-01-01

Heated high speed subsonic and supersonic jets operating on- or off-design are a source of noise that is not yet fully understood. Helium-air mixtures can be used in the correct ratio to simulate the total temperature ratio of heated air jets and hence have the potential to provide inexpensive and reliable flow and acoustic measurements. This study presents a combination of flow measurements of helium-air high speed jets and numerical simulations of similar helium-air mixture and heated air jets. Jets issuing from axisymmetric convergent and convergent-divergent nozzles are investigated, and the results show very strong similarity with heated air jet measurements found in the literature. This demonstrates the validity of simulating heated high speed jets with helium-air in the laboratory, together with the excellent agreement obtained in the presented data between the numerical predictions and the experiments. The very close match between the numerical and experimental data also validates the frozen chemistry model used in the numerical simulation.

Numerical study on non-locally reacting behavior of nacelle liners incorporating drainage slots

Science.gov (United States)

Chen, Chao; Li, Xiaodong; Thiele, Frank

2018-06-01

For acoustic liners used in current commercial nacelles, in order to prevent any liquid accumulating in the resonators, drainage slots are incorporated on the partition walls between closely packed cavities. Recently, an experimental study conducted by Busse-Gerstengarbe et al. shown that the cell interaction introduced by drainage slots causes an additional dissipation peak which increases with the size of the slot. However, the variation of damping process due to drainage slots is still not fully understood. Therefore, a numerical study based on computational aeroacoustic methods is carried out to investigate the mechanism of the changed attenuation characteristics due to drainage slots in presence of grazing incident sound waves with low or high intensities. Different slot configurations are designed based on the generic non-locally reacting liner model adopted in the experimental investigation. Both 2-D and 3-D numerical simulations of only slit resonators are carried out. Numerical results indicate that the extra peak is a result of a resonance excited in the second cavity at specific frequency. Under high sound pressure level incoming waves, the basic characteristics of the acoustic performance remain. However, vortex shedding transpires at the resonances around both the slits and the drainage slot. Vorticity contours show that the connection of two coupled cavities decreases the strength of vortex shedding around the basic Helmholtz resonance due to a higher energy reflection. Meanwhile, the cell interaction significantly increases the vorticity magnitude near the extra resonant frequency. Finally, a semi-empirical model is derived to predict the extra attenuation peak frequency.

Numerical studies of temperature effect on the extrusion fracture and swell of plastic micro-pipe

Science.gov (United States)

Ren, Zhong; Huang, Xingyuan; Xiong, Zhihua

2018-03-01

Temperature is a key factor that impacts extrusion forming quality of plastic micro-pipe. In this study, the effect of temperature on extrusion fracture and swell of plastic micro-pipe was investigated by numerical method. Under a certain of the melt’s flow volume, the extrusion pattern, extrusion swelling ratio of melt are obtained under different temperatures. Results show that the extrusion swelling ratio of plastic micro-pipe decreases with increasing of temperature. In order to study the reason of temperature effect, the physical distributions of plastic micro-pipe are gotten. Numerical results show that the viscosity, pressure, stress value of melt are all decreased with the increasing of temperature, which leads to decrease the extrusion swell and fracture phenomenon for the plastic micro-pipe.

Numerical studies of time-independent and time-dependent scattering by several elliptical cylinders

Science.gov (United States)

Nigsch, Martin

2007-07-01

A numerical solution to the problem of time-dependent scattering by an array of elliptical cylinders with parallel axes is presented. The solution is an exact one, based on the separation-of-variables technique in the elliptical coordinate system, the addition theorem for Mathieu functions, and numerical integration. Time-independent solutions are described by a system of linear equations of infinite order which are truncated for numerical computations. Time-dependent solutions are obtained by numerical integration involving a large number of these solutions. First results of a software package generating these solutions are presented: wave propagation around three impenetrable elliptical scatterers. As far as we know, this method described has never been used for time-dependent multiple scattering.

Experimental and numerical approaches to studying hot cracking in stainless steel welds

International Nuclear Information System (INIS)

Le, Minh

2014-01-01

This work concerns experimental and numerical approaches to studying hot cracking in welds in stainless steel. Metallurgical weldability of two filler products used for the welding of an AISI-316L(N) austenitic stainless steel grade is evaluated. These filler metals are distinguished by their solidification microstructures: austeno-ferritic for the 19Cr-12Ni-2Mo grade and austenitic for the 19-15H Thermanit grade. The study of weldability concerns the assessment of the susceptibility to hot cracking of these three alloys, the proposition of a hot cracking criterion, and the evaluation of its transferability to structure-scale tests. Hot cracks are material separations occurring at high temperatures along the grain boundaries (dendrite boundaries), when the level of strain and the strain rate exceed a certain level. The hot cracks studied are formed during solidification from the liquid phase of weld metals. The bibliography study brings to the fore the complexity of initiation and propagation mechanisms of these material separations. Three types of tests are studied in this work: hot cracking tests, such as trapezoidal and Varestraint tests, allowing to initiate the phenomenon in controlled experimental conditions, and tests on the Gleeble thermomechanical simulator for thermomechanical (materials behavior laws, fracture properties) and metallurgical (brittle temperature range (BTR), evolution of delta ferrite) characterizations of the alloys. All these tests on the three materials were analyzed via numerical modeling and simulations implemented in the Cast3M finite element code in order to bring out a thermomechanical hot cracking criterion. (author) [fr

Numerical study of agglomerate abrasion in a tumbling mixer

NARCIS (Netherlands)

Thanh Nguyen, [No Value; Willemsz, Tofan; Frijlink, Henderik; Maarschalk, Kees van der Voort

2014-01-01

A numerical simulation using the Discrete Element Method (DEM) was performed to investigate the phenomena concerning the abrasion and breakage of agglomerates in a diffusion powder mixer. Agglomerates were created by defining a single structure of particles with bonds of different strengths using

A Numerical Study of Hydrodynamics and Sediment Transport in Fourleague Bay, Louisiana

Science.gov (United States)

Hu, K.; Chen, Q. J.; Xu, K.; Bentley, S. J.; WANG, J.

2017-12-01

Fourleague Bay is a shallow and vertically well-mixed estuary in south-central Louisiana. This estuary is highly impacted by wind (e.g., cold fronts and tropical storms), river discharge from the Atchafalaya River and tides from the Gulf of Mexico, and is being used as an analog site to study impacts of sediment-diversion restoration strategies in the Mississippi River Delta. In this study, a coupled flow-wave Delft3D model was setup and applied to study hydrodynamics and sediment transport in this area. The model grid size is 1071x631 with a 50-m resolution in the bay. Vegetation is considered by rigid cylinders in both flow and wave modules. The offshore water level boundary conditions were provided by a Gulf-scale Delft3D model. Model parameters, especially for cohesive sediment transport such as settling velocity, erosion rate and critical bottom shear stress, were calibrated using the field observation data during three seasons from May 2015 to March 2016. The modeled water levels, currents, significant wave heights and suspended sediment concentrations agreed fairly well with measurements, which suggests a reasonable model performance. Seasonal variations were analyzed based on different scenarios. A series of numerical experiments were set up to quantify the contributions of different factors, such as river discharge, tides and waves to sediment transport in this area. This model will be further applied to be part of a landscape ecosystem model to test landscape and population change over time with manipulations to sediment delivery. This study was funded by the National Science Foundation (SEES-1427389 and CCF-1539567).

Numerical studies of the g-hartree density functional in the Thomas-Fermi scaling limit

International Nuclear Information System (INIS)

Millack, T.; Weymans, G.

1986-02-01

Methods of finite temperature quantum field theory are used to construct the g-Hartree density functional for atoms. Low and high temperature expansions are discussed in detail. Numerical studies for atomic ground-state configurations are presented in the Thomas-Fermi-Scaling limit. (orig.)

An analytical and numerical study of solar chimney use for room natural ventilation

Energy Technology Data Exchange (ETDEWEB)

Bassiouny, Ramadan; Koura, Nader S.A. [Department of Mechanical Power Engineering and Energy, Minia University, Minia 61111 (Egypt)

2008-07-01

The solar chimney concept used for improving room natural ventilation was analytically and numerically studied. The study considered some geometrical parameters such as chimney inlet size and width, which are believed to have a significant effect on space ventilation. The numerical analysis was intended to predict the flow pattern in the room as well as in the chimney. This would help optimizing design parameters. The results were compared with available published experimental and theoretical data. There was an acceptable trend match between the present analytical results and the published data for the room air change per hour, ACH. Further, it was noticed that the chimney width has a more significant effect on ACH compared to the chimney inlet size. The results showed that the absorber average temperature could be correlated to the intensity as: (T{sub w} = 3.51I{sup 0.461}) with an accepted range of approximation error. In addition the average air exit velocity was found to vary with the intensity as ({nu}{sub ex} = 0.013I{sup 0.4}). (author)

Numerical study on hygroscopic material drying in packed bed

Directory of Open Access Journals (Sweden)

M. Stakić

2011-06-01

Full Text Available The paper addresses numerical simulation for the case of convective drying of hygroscopic material in a packed bed, analyzing agreement between the simulated and the corresponding experimental results. In the simulation model of unsteady simultaneous one-dimensional heat and mass transfer between gas phase and dried material, it is assumed that the gas-solid interface is at thermodynamic equilibrium, while the drying rate of the specific product is calculated by applying the concept of a "drying coefficient". Model validation was done on the basis of the experimental data obtained with potato cubes. The obtained drying kinetics, both experimental and numerical, show that higher gas (drying agent velocities (flow-rates, as well as lower equivalent grain diameters, induce faster drying. This effect is more pronounced for deeper beds, because of the larger amount of wet material to be dried using the same drying agent capacity.

A numerical test method of California bearing ratio on graded crushed rocks using particle flow modeling

Directory of Open Access Journals (Sweden)

Yingjun Jiang

2015-04-01

Full Text Available In order to better understand the mechanical properties of graded crushed rocks (GCRs and to optimize the relevant design, a numerical test method based on the particle flow modeling technique PFC2D is developed for the California bearing ratio (CBR test on GCRs. The effects of different testing conditions and micro-mechanical parameters used in the model on the CBR numerical results have been systematically studied. The reliability of the numerical technique is verified. The numerical results suggest that the influences of the loading rate and Poisson's ratio on the CBR numerical test results are not significant. As such, a loading rate of 1.0–3.0 mm/min, a piston diameter of 5 cm, a specimen height of 15 cm and a specimen diameter of 15 cm are adopted for the CBR numerical test. The numerical results reveal that the CBR values increase with the friction coefficient at the contact and shear modulus of the rocks, while the influence of Poisson's ratio on the CBR values is insignificant. The close agreement between the CBR numerical results and experimental results suggests that the numerical simulation of the CBR values is promising to help assess the mechanical properties of GCRs and to optimize the grading design. Besides, the numerical study can provide useful insights on the mesoscopic mechanism.

Using a familiar risk comparison within a risk ladder to improve risk understanding by low numerates: a study of visual attention.

Science.gov (United States)

Keller, Carmen

2011-07-01

Previous experimental research provides evidence that a familiar risk comparison within a risk ladder is understood by low- and high-numerate individuals. It especially helps low numerates to better evaluate risk. In the present study, an eye tracker was used to capture individuals' visual attention to a familiar risk comparison, such as the risk associated with smoking. Two parameters of information processing-efficiency and level-were derived from visual attention. A random sample of participants from the general population (N= 68) interpreted a given risk level with the help of the risk ladder. Numeracy was negatively correlated with overall visual attention on the risk ladder (r(s) =-0.28, p= 0.01), indicating that the lower the numeracy, the more the time spent looking at the whole risk ladder. Numeracy was positively correlated with the efficiency of processing relevant frequency (r(s) = 0.34, p improving risk communication formats. © 2011 Society for Risk Analysis.

Numerical and Experimental Study of an Ambient Air Vaporizer Coupled with a Compact Heat Exchanger

Science.gov (United States)

Kimura, Randon

The University of Washington was tasked with designing a "21st century engine" that will make use of the thermal energy available in cryogenic gasses due to their coldness. There are currently large quantities of cryogenic gases stored throughout the U.S. at industrial facilities whereupon the regasification process, the potential for the fluid to do work is wasted. The engine proposed by the University of Washington will try to capture some of that wasted energy. One technical challenge that must be overcome during the regasification process is providing frost free operation. This thesis presents the numerical analysis and experimental testing of a passive heat exchange system that uses ambient vaporizers coupled with compact heat exchangers to provide frost free operation while minimizing pressure drop.

A numerical study of two interacting coronal mass ejections

Directory of Open Access Journals (Sweden)

J. M. Schmidt

2004-06-01

Full Text Available The interaction in the solar wind between two coronal mass ejections (CMEs is investigated using numerical simulations. We show that the nature of the interaction depends on whether the CME magnetic structures interact, but in all cases the result is an equilisation of the speed of the two CMEs. In the absence of magnetic interaction, the forward shock of the faster trailing CME interacts with the slow leading CME, and accelerates it. When the two CMEs have magnetic fields with the same sense of rotation, magnetic reconnection occurs between the two CMEs, leading to the formation of a single magnetic structure: in the most extreme cases, one CME "eats" the other. When the senses of rotation are opposite, reconnection does not occur, but the CMEs collide in a highly non-elastic manner, again forming a single structure. The possibility of enhanced particle acceleration in such processes is assessed. The presence of strong magnetic reconnection provides excellent opportunities for the acceleration of thermal particles, which then form a seed population for further acceleration at the CME shocks. The presence of a large population of seed particles will thus lead to an overall increase in energetic particle fluxes, as suggested by some observations.

Analytical and Numerical solutions of a nonlinear alcoholism model via variable-order fractional differential equations

Science.gov (United States)

Gómez-Aguilar, J. F.

2018-03-01

In this paper, we analyze an alcoholism model which involves the impact of Twitter via Liouville-Caputo and Atangana-Baleanu-Caputo fractional derivatives with constant- and variable-order. Two fractional mathematical models are considered, with and without delay. Special solutions using an iterative scheme via Laplace and Sumudu transform were obtained. We studied the uniqueness and existence of the solutions employing the fixed point postulate. The generalized model with variable-order was solved numerically via the Adams method and the Adams-Bashforth-Moulton scheme. Stability and convergence of the numerical solutions were presented in details. Numerical examples of the approximate solutions are provided to show that the numerical methods are computationally efficient. Therefore, by including both the fractional derivatives and finite time delays in the alcoholism model studied, we believe that we have established a more complete and more realistic indicator of alcoholism model and affect the spread of the drinking.

Theoretical and numerical studies of TWR based on ESFR core design

International Nuclear Information System (INIS)

Zhang, Dalin; Chen, Xue-Nong; Flad, Michael; Rineiski, Andrei; Maschek, Werner

2013-01-01

Highlights: • The traveling wave reactor (TWR) is studied based on the core design of the European Sodium-cooled Fast Reactor (ESFR). • The conventional fuel shuffling technique is used to produce a continuous radial fuel movement. • A stationary self sustainable nuclear fission power can be established asymptotically by only loading natural or depleted uranium. • The multi-group deterministic neutronic code ERANOS is applied. - Abstract: This paper deals with the so-called traveling wave reactor (TWR) based on the core design of the European Sodium-cooled Fast Reactor (ESFR). The current concept of TWR is to use the conventional radial fuel shuffling technique to produce a continuous radial fuel movement so that a stationary self sustainable nuclear fission power can be established asymptotically by only loading fertile material consisting of natural or depleted uranium. The core design of ESFR loaded with metallic uranium fuel without considering the control mechanism is used as a practical application example. The theoretical studies focus mainly on qualitative feasibility analyses, i.e. to identify out in general essential parameter dependences of such a kind of reactor. The numerical studies are carried out more specifically on a certain core design. The multi-group deterministic neutronic code ERANOS with the JEFF3.1 data library is applied as a basic tool to perform the neutronics and burn-up calculations. The calculations are performed in a 2-D R-Z geometry, which is sufficient for the current core layout. Numerical results of radial fuel shuffling indicate that the asymptotic k eff parabolically varies with the shuffling period, while the burn-up increases linearly. Typical shuffling periods investigated in this study are in the range of 300–1000 days. The important parameters, e.g. k eff , the burn-up, the power peaking factor, and safety coefficients are calculated

Extraction of gravitational waves in numerical relativity.

Science.gov (United States)

Bishop, Nigel T; Rezzolla, Luciano

2016-01-01

A numerical-relativity calculation yields in general a solution of the Einstein equations including also a radiative part, which is in practice computed in a region of finite extent. Since gravitational radiation is properly defined only at null infinity and in an appropriate coordinate system, the accurate estimation of the emitted gravitational waves represents an old and non-trivial problem in numerical relativity. A number of methods have been developed over the years to "extract" the radiative part of the solution from a numerical simulation and these include: quadrupole formulas, gauge-invariant metric perturbations, Weyl scalars, and characteristic extraction. We review and discuss each method, in terms of both its theoretical background as well as its implementation. Finally, we provide a brief comparison of the various methods in terms of their inherent advantages and disadvantages.

Determination of Solution Accuracy of Numerical Schemes as Part of Code and Calculation Verification

Energy Technology Data Exchange (ETDEWEB)

Blottner, F.G.; Lopez, A.R.

1998-10-01

This investigation is concerned with the accuracy of numerical schemes for solving partial differential equations used in science and engineering simulation codes. Richardson extrapolation methods for steady and unsteady problems with structured meshes are presented as part of the verification procedure to determine code and calculation accuracy. The local truncation error de- termination of a numerical difference scheme is shown to be a significant component of the veri- fication procedure as it determines the consistency of the numerical scheme, the order of the numerical scheme, and the restrictions on the mesh variation with a non-uniform mesh. Genera- tion of a series of co-located, refined meshes with the appropriate variation of mesh cell size is in- vestigated and is another important component of the verification procedure. The importance of mesh refinement studies is shown to be more significant than just a procedure to determine solu- tion accuracy. It is suggested that mesh refinement techniques can be developed to determine con- sistency of numerical schemes and to determine if governing equations are well posed. The present investigation provides further insight into the conditions and procedures required to effec- tively use Richardson extrapolation with mesh refinement studies to achieve confidence that sim- ulation codes are producing accurate numerical solutions.

Zdeněk Kopal: Numerical Analyst

Science.gov (United States)

Křížek, M.

2015-07-01

We give a brief overview of Zdeněk Kopal's life, his activities in the Czech Astronomical Society, his collaboration with Vladimír Vand, and his studies at Charles University, Cambridge, Harvard, and MIT. Then we survey Kopal's professional life. He published 26 monographs and 20 conference proceedings. We will concentrate on Kopal's extensive monograph Numerical Analysis (1955, 1961) that is widely accepted to be the first comprehensive textbook on numerical methods. It describes, for instance, methods for polynomial interpolation, numerical differentiation and integration, numerical solution of ordinary differential equations with initial or boundary conditions, and numerical solution of integral and integro-differential equations. Special emphasis will be laid on error analysis. Kopal himself applied numerical methods to celestial mechanics, in particular to the N-body problem. He also used Fourier analysis to investigate light curves of close binaries to discover their properties. This is, in fact, a problem from mathematical analysis.

Testing gravitational-wave searches with numerical relativity waveforms: results from the first Numerical INJection Analysis (NINJA) project

International Nuclear Information System (INIS)

Aylott, Benjamin; Baker, John G; Camp, Jordan; Centrella, Joan; Boggs, William D; Buonanno, Alessandra; Boyle, Michael; Buchman, Luisa T; Chu, Tony; Brady, Patrick R; Brown, Duncan A; Bruegmann, Bernd; Cadonati, Laura; Campanelli, Manuela; Faber, Joshua; Chatterji, Shourov; Christensen, Nelson; Diener, Peter; Dorband, Nils; Etienne, Zachariah B

2009-01-01

The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational-wave data analysis communities. The purpose of NINJA is to study the sensitivity of existing gravitational-wave search algorithms using numerically generated waveforms and to foster closer collaboration between the numerical relativity and data analysis communities. We describe the results of the first NINJA analysis which focused on gravitational waveforms from binary black hole coalescence. Ten numerical relativity groups contributed numerical data which were used to generate a set of gravitational-wave signals. These signals were injected into a simulated data set, designed to mimic the response of the initial LIGO and Virgo gravitational-wave detectors. Nine groups analysed this data using search and parameter-estimation pipelines. Matched filter algorithms, un-modelled-burst searches and Bayesian parameter estimation and model-selection algorithms were applied to the data. We report the efficiency of these search methods in detecting the numerical waveforms and measuring their parameters. We describe preliminary comparisons between the different search methods and suggest improvements for future NINJA analyses.

Numerical studies of the MHD spectrum of an elliptic plasma column

International Nuclear Information System (INIS)

Chance, M.S.; Greene, J.M.; Grimm, R.C.; Johnson, J.L.

1976-05-01

A numerical procedure is described for determining the MHD spectrum associated with small perturbations about an analytic equilibrium. This configuration has magnetic flux surfaces which are nested similar elliptical cylinders generated by a uniform axial current. Since the system is periodic, it models the essential features of a toroid. The code is used to study the properties of modes in the continuous shear Alfven and slow acoustic spectra as well as the discrete modes associated with the fast magnetosonic waves and kinks. Modes where the interchange criterion is violated, or nearly violated, are investigated

Cross-Validation of Numerical and Experimental Studies of Transitional Airfoil Performance

DEFF Research Database (Denmark)

Frere, Ariane; Hillewaert, Koen; Sarlak, Hamid

2015-01-01

The aerodynamic performance characteristic of airfoils are the main input for estimating wind turbine blade loading as well as annual energy production of wind farms. For transitional flow regimes these data are difficult to obtain, both experimentally as well as numerically, due to the very high...... sensitivity of the flow to perturbations, large scale separation and performance hysteresis. The objective of this work is to improve the understanding of the transitional airfoil flow performance by studying the S826 NREL airfoil at low Reynolds numbers (Re = 4:104 and 1:105) with two inherently different...

Numerical study of a gridded E-GUN with a very small cathode-grid distance (150 {mu}m) using EGN2

Energy Technology Data Exchange (ETDEWEB)

Ronsivalle, C. [ENEA, Centro Ricerche Frascati, Rome (Italy). Dip. Innovazione

1997-01-01

A numerical study of a triode gun with a very small cathode-grid distance (150 {mu}m) which allows to evaluate with great accuracy the effect of the grid and of the temperature on the final beam emittance is presented. The simulation uses a modified version of the bidimensional code EGUN for PC that simulates the grid with a set of concentric rings and allows to define several regions of different mesh size, providing the way to connect results between adjacent regions. The calculation procedure is described in detail together with the results of the simulation for different values of the grid potential.

A numerical study of the stabilitiy of helical vortices using vortex methods

International Nuclear Information System (INIS)

Walther, J H; Guenot, M; Machefaux, E; Rasmussen, J T; Chatelain, P; Okulov, V L; Soerensen, J N; Bergdorf, M; Koumoutsakos, P

2007-01-01

We present large-scale parallel direct numerical simulations using particle vortex methods of the instability of the helical vortices. We study the instability of a single helical vortex and find good agreement with inviscid theory. We outline equilibrium configurations for three double helical vortices-similar to those produced by three blade wind turbines. The simulations confirm the stability of the inviscid model, but predict a breakdown of the vortical system due to viscosity