Numerical method for three dimensional steady-state two-phase flow calculations
International Nuclear Information System (INIS)
Raymond, P.; Toumi, I.
1992-01-01
This paper presents the numerical scheme which was developed for the FLICA-4 computer code to calculate three dimensional steady state two phase flows. This computer code is devoted to steady state and transient thermal hydraulics analysis of nuclear reactor cores 1,3 . The first section briefly describes the FLICA-4 flow modelling. Then in order to introduce the numerical method for steady state computations, some details are given about the implicit numerical scheme based upon an approximate Riemann solver which was developed for calculation of flow transients. The third section deals with the numerical method for steady state computations, which is derived from this previous general scheme and its optimization. We give some numerical results for steady state calculations and comparisons on required CPU time and memory for various meshing and linear system solvers
Numerical analysis of steady and transient natural convection in an enclosed cavity
Mehedi, Tanveer Hassan; Tahzeeb, Rahat Bin; Islam, A. K. M. Sadrul
2017-06-01
The paper presents the numerical simulation of natural convection heat transfer of air inside an enclosed cavity which can be helpful to find out the critical width of insulation in air insulated walls seen in residential buildings and industrial furnaces. Natural convection between two walls having different temperatures have been simulated using ANSYS FLUENT 12.0 in both steady and transient conditions. To simulate different heat transfer and fluid flow conditions, Rayleigh number ranging from 103 to 105 has been maintained (i.e. Laminar flow.) In case of steady state analysis, the CFD predictions were in very good agreement with the reviewed literature. Transient simulation process has been performed by using User Defined Functions, where the temperature of the hot wall varies with time linearly. To obtain and compare the heat transfer properties, Nusselt number has been calculated at the hot wall at different conditions. The buoyancy driven flow characteristics have been investigated by observing the flow pattern in a graphical manner. The characteristics of the system at different temperature differences between the wall has been observed and documented.
Numerical investigation of steady-state thermal behavior of an infrared detector cryo chamber
Directory of Open Access Journals (Sweden)
Singhal Mayank
2017-01-01
Full Text Available An infrared (IR detector is simply a transducer of radiant energy, converting radiant energy into a measurable form. Since radiation does not rely on visible light, it offers the possibility of seeing in the dark or through obscured conditions, by detecting the IR energy emitted by objects. One of the prime applications of IR detector systems for military use is in target acquisition and tracking of projectile systems. The IR detectors also have great potential in commercial market. Typically, IR detectors perform best when cooled to cryogenic temperatures in the range of nearly 120 K. However, the necessity to operate in such cryogenic regimes makes the application of IR detectors extremely complex. Further, prior to proceeding on to a full blown transient thermal analysis it is worthwhile to perform a steady-state numerical analysis for ascertaining the effect of variation in viz., material, gas conduction coefficient, h, emissivity, ε, on the temperature profile along the cryo chamber length. This would enable understanding the interaction between the cryo chamber and its environment. Hence, the present work focuses on the development of steady-state numerical models for thermal analysis of IR cryo chamber using MATLAB. The numerical results show that gas conduction coefficient has marked influence on the temperature profile of the cryo chamber whereas the emissivity has a weak effect. The experimental validation of numerical results has also been presented.
Directory of Open Access Journals (Sweden)
Victor ANJO
2012-08-01
Full Text Available The solidification of molten metal during the casting process involves heat transfer from the molten metal to the mould, then to the atmosphere. The mechanical properties and grain size of metals are determined by the heat transfer process during solidification. The aim of this study is to numerically stimulate the steady conduction heat transfer during the solidification of aluminum in green sand mould using finite difference analysis 2D. The properties of materials used are industrial AI 50/60 AFS green sand mould, pure aluminum and MATLAB 7.0.1. for the numerical simulation. The method includes; the finite difference analysis of the heat conduction equation in steady (Laplaces and transient states and using MATLAB to numerically stimulate the thermal flow and cooling curve. The results obtained are: the steady state thermal flow in 2D and transient state cooling curve of casting. The results obtain were consider relevant in the control of the grain size and mechanical properties of the casting.
International Nuclear Information System (INIS)
Zhou, Xiafeng; Guo, Jiong; Li, Fu
2015-01-01
Highlights: • NEMs are innovatively applied to solve convection diffusion equation. • Stability, accuracy and numerical diffusion for NEM are analyzed for the first time. • Stability and numerical diffusion depend on the NEM expansion order and its parity. • NEMs have higher accuracy than both second order upwind and QUICK scheme. • NEMs with different expansion orders are integrated into a unified discrete form. - Abstract: The traditional finite difference method or finite volume method (FDM or FVM) is used for HTGR thermal-hydraulic calculation at present. However, both FDM and FVM require the fine mesh sizes to achieve the desired precision and thus result in a limited efficiency. Therefore, a more efficient and accurate numerical method needs to be developed. Nodal expansion method (NEM) can achieve high accuracy even on the coarse meshes in the reactor physics analysis so that the number of spatial meshes and computational cost can be largely decreased. Because of higher efficiency and accuracy, NEM can be innovatively applied to thermal-hydraulic calculation. In the paper, NEMs with different orders of basis functions are successfully developed and applied to multi-dimensional steady convection diffusion equation. Numerical results show that NEMs with three or higher order basis functions can track the reference solutions very well and are superior to second order upwind scheme and QUICK scheme. However, the false diffusion and unphysical oscillation behavior are discovered for NEMs. To explain the reasons for the above-mentioned behaviors, the stability, accuracy and numerical diffusion properties of NEM are analyzed by the Fourier analysis, and by comparing with exact solutions of difference and differential equation. The theoretical analysis results show that the accuracy of NEM increases with the expansion order. However, the stability and numerical diffusion properties depend not only on the order of basis functions but also on the parity of
Energy Technology Data Exchange (ETDEWEB)
Zhou, Xiafeng, E-mail: zhou-xf11@mails.tsinghua.edu.cn; Guo, Jiong, E-mail: guojiong12@tsinghua.edu.cn; Li, Fu, E-mail: lifu@tsinghua.edu.cn
2015-12-15
Highlights: • NEMs are innovatively applied to solve convection diffusion equation. • Stability, accuracy and numerical diffusion for NEM are analyzed for the first time. • Stability and numerical diffusion depend on the NEM expansion order and its parity. • NEMs have higher accuracy than both second order upwind and QUICK scheme. • NEMs with different expansion orders are integrated into a unified discrete form. - Abstract: The traditional finite difference method or finite volume method (FDM or FVM) is used for HTGR thermal-hydraulic calculation at present. However, both FDM and FVM require the fine mesh sizes to achieve the desired precision and thus result in a limited efficiency. Therefore, a more efficient and accurate numerical method needs to be developed. Nodal expansion method (NEM) can achieve high accuracy even on the coarse meshes in the reactor physics analysis so that the number of spatial meshes and computational cost can be largely decreased. Because of higher efficiency and accuracy, NEM can be innovatively applied to thermal-hydraulic calculation. In the paper, NEMs with different orders of basis functions are successfully developed and applied to multi-dimensional steady convection diffusion equation. Numerical results show that NEMs with three or higher order basis functions can track the reference solutions very well and are superior to second order upwind scheme and QUICK scheme. However, the false diffusion and unphysical oscillation behavior are discovered for NEMs. To explain the reasons for the above-mentioned behaviors, the stability, accuracy and numerical diffusion properties of NEM are analyzed by the Fourier analysis, and by comparing with exact solutions of difference and differential equation. The theoretical analysis results show that the accuracy of NEM increases with the expansion order. However, the stability and numerical diffusion properties depend not only on the order of basis functions but also on the parity of
A asymptotic numerical method for the steady-state convection diffusion equation
International Nuclear Information System (INIS)
Wu Qiguang
1988-01-01
In this paper, A asymptotic numerical method for the steady-state Convection diffusion equation is proposed, which need not take very fine mesh size in the neighbourhood of the boundary layer. Numerical computation for model problem show that we can obtain the numerical solution in the boundary layer with moderate step size
International Nuclear Information System (INIS)
Nagarajan, Vijaisri; Chen, Yitung; Wang, Qiuwang; Ma, Ting
2014-01-01
Highlights: • Rip saw fin design is considered to be the best because it has thin fins and has higher heat transfer coefficient. • Minimum principal stress and maximum safety factor are obtained for the inverted bolt fin design. • Maximum principal stress and minimum safety factor are obtained for triangular fin design. • Thermal stress has significant impact than mechanical stress. • High principal stress is found at the startup and shutdown stage. - Abstract: In this study three-dimensional model of ceramic plate-fin high temperature heat exchanger with different fin designs and arrangements is analyzed numerically using ANSYS FLUENT and ANSYS structural module. The ability of ceramics to withstand high temperature and corrosion makes silicon carbide (SiC) suitable candidate material to be used in high temperature heat exchanger. The operating temperature of heat exchanger is 950 °C and the operating pressure is 1.5 MPa. The working fluids are helium, sulfur trioxide, sulfur dioxide, oxygen and the water vapor. Fluid flow and heat transfer analysis are carried out for steady and transient state in FLUENT. The obtained thermal and pressure load for the steady and transient state from ANSYS FLUENT are imported to ANSYS structural module to obtain the principal stress and the factor of safety. Different arrangements of rectangular fins, triangular fins, inverted bolt fins and ripsaw fins are studied. From the results it is found that the minimum stress and the maximum safety factor are obtained for inverted bolt fins. The triangular fins have the maximum principal stress and minimum factor of safety. However, the fluid flow and heat transfer analysis show inverted bolt fins and triangular fins produce higher pressure drop and friction factor. The steady state maximum principal stress is 10.08 MPa, 9.90 MPa and 11.43 MPa for straight, staggered and top and bottom ripsaw fin arrangement. The corresponding safety factors are 21.80, 21.95 and 19
Dawid, H.; Keoula, M.Y.; Kort, Peter
2017-01-01
This paper presents a numerical method for the characterization of Markov-perfect equilibria of symmetric differential games exhibiting coexisting stable steady states. The method relying on the calculation of ‘local value functions’ through collocation in overlapping parts of the state space, is
Zhao, Enjin; Shi, Bing; Qu, Ke; Dong, Wenbin; Zhang, Jing
2018-04-01
As a new type of submarine pipeline, the piggyback pipeline has been gradually adopted in engineering practice to enhance the performance and safety of submarine pipelines. However, limited simulation work and few experimental studies have been published on the scour around the piggyback pipeline under steady current. This study numerically and experimentally investigates the local scour of the piggyback pipe under steady current. The influence of prominent factors such as pipe diameter, inflow Reynolds number, and gap between the main and small pipes, on the maximum scour depth have been examined and discussed in detail. Furthermore, one formula to predict the maximum scour depth under the piggyback pipeline has been derived based on the theoretical analysis of scour equilibrium. The feasibility of the proposed formula has been effectively calibrated by both experimental data and numerical results. The findings drawn from this study are instructive in the future design and application of the piggyback pipeline.
Reliable and Efficient Procedure for Steady-State Analysis of Nonautonomous and Autonomous Systems
Directory of Open Access Journals (Sweden)
J. Dobes
2012-04-01
Full Text Available The majority of contemporary design tools do not still contain steady-state algorithms, especially for the autonomous systems. This is mainly caused by insufficient accuracy of the algorithm for numerical integration, but also by unreliable steady-state algorithms themselves. Therefore, in the paper, a very stable and efficient procedure for the numerical integration of nonlinear differential-algebraic systems is defined first. Afterwards, two improved methods are defined for finding the steady state, which use this integration algorithm in their iteration loops. The first is based on the idea of extrapolation, and the second utilizes nonstandard time-domain sensitivity analysis. The two steady-state algorithms are compared by analyses of a rectifier and a C-class amplifier, and the extrapolation algorithm is primarily selected as a more reliable alternative. Finally, the method based on the extrapolation naturally cooperating with the algorithm for solving the differential-algebraic systems is thoroughly tested on various electronic circuits: Van der Pol and Colpitts oscillators, fragment of a large bipolar logical circuit, feedback and distributed microwave oscillators, and power amplifier. The results confirm that the extrapolation method is faster than a classical plain numerical integration, especially for larger circuits with complicated transients.
Steady-state transport equation resolution by particle methods, and numerical results
International Nuclear Information System (INIS)
Mercier, B.
1985-10-01
A method to solve steady-state transport equation has been given. Principles of the method are given. The method is studied in two different cases; estimations given by the theory are compared to numerical results. Results got in 1-D (spherical geometry) and in 2-D (axisymmetric geometry) are given [fr
Numerical analysis of flow fields generated by accelerating flames
Energy Technology Data Exchange (ETDEWEB)
Kurylo, J.
1977-12-01
Presented here is a numerical technique for the analysis of non-steady flow fields generated by accelerating flames in gaseous media. Of particular interest in the study is the evaluation of the non-steady effects on the flow field and the possible transition of the combustion process to detonation caused by an abrupt change in the burning speed of an initially steady flame propagating in an unconfined combustible gas mixture. Optically recorded observations of accelerating flames established that the flow field can be considered to consist of non-steady flow fields associated with an assembly of interacting shock waves, contact discontinuities, deflagration and detonation fronts. In the analysis, these flow fields are treated as spatially one-dimensional, the influence of transport phenomena is considered to be negligible, and unburned and burned substances are assumed to behave as perfect gases with constant, but different, specific heats. The basis of the numerical technique is an explicit, two step, second order accurate, finite difference scheme employed to integrate the flow field equations expressed in divergence form. The burning speed, governing the motion of the deflagration, is expressed in the form of a power law dependence on pressure and temperature immediately ahead of its front. The steady wave solution is obtained by the vector polar interaction technique, that is, by determining the point of intersection between the loci of end states in the plane of the two interaction invariants, pressure and particle velocity. The technique is illustrated by a numerical example in which a steady flame experiences an abrupt change in its burning speed. Solutions correspond either to the eventual reestablishment of a steady state flow field commensurate with the burning speed or to the transition to detonation. The results are in satisfactory agreement with experimental observations.
Numerical simulation of steady cavitating flow of viscous fluid in a Francis hydroturbine
Panov, L. V.; Chirkov, D. V.; Cherny, S. G.; Pylev, I. M.; Sotnikov, A. A.
2012-09-01
Numerical technique was developed for simulation of cavitating flows through the flow passage of a hydraulic turbine. The technique is based on solution of steady 3D Navier—Stokes equations with a liquid phase transfer equation. The approch for setting boundary conditions meeting the requirements of cavitation testing standard was suggested. Four different models of evaporation and condensation were compared. Numerical simulations for turbines of different specific speed were compared with experiment.
International Nuclear Information System (INIS)
Li Jian; Ning Jian-Guo; Zhao Hui; Wang Cheng; Hao Li
2015-01-01
The propagation mechanism of steady cellular detonations in curved channels is investigated numerically with a detailed chemical reaction mechanism. The numerical results demonstrate that as the radius of the curvature decreases, detonation fails near the inner wall due to the strong expansion effect. As the radius of the curvature increases, the detonation front near the inner wall can sustain an underdriven detonation. In the case where detonation fails, a transverse detonation downstream forms and re-initiates the quenched detonation as it propagates toward the inner wall. Two kinds of propagation modes exist as the detonation is propagating in the curved channel. One is that the detonation fails first, and then a following transverse detonation initiates the quenched detonation and this process repeats itself. The other one is that without detonation failure and re-initiation, a steady detonation exists which consists of an underdriven detonation front near the inner wall subject to the diffraction and an overdriven detonation near the outer wall subject to the compression. (paper)
Directory of Open Access Journals (Sweden)
Jilian Wu
2013-01-01
Full Text Available We discuss several stabilized finite element methods, which are penalty, regular, multiscale enrichment, and local Gauss integration method, for the steady incompressible flow problem with damping based on the lowest equal-order finite element space pair. Then we give the numerical comparisons between them in three numerical examples which show that the local Gauss integration method has good stability, efficiency, and accuracy properties and it is better than the others for the steady incompressible flow problem with damping on the whole. However, to our surprise, the regular method spends less CPU-time and has better accuracy properties by using Crout solver.
Reliability importance analysis of Markovian systems at steady state using perturbation analysis
Energy Technology Data Exchange (ETDEWEB)
Phuc Do Van [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France); Barros, Anne [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France)], E-mail: anne.barros@utt.fr; Berenguer, Christophe [Institut Charles Delaunay - FRE CNRS 2848, Systems Modeling and Dependability Group, Universite de technologie de Troyes, 12, rue Marie Curie, BP 2060-10010 Troyes cedex (France)
2008-11-15
Sensitivity analysis has been primarily defined for static systems, i.e. systems described by combinatorial reliability models (fault or event trees). Several structural and probabilistic measures have been proposed to assess the components importance. For dynamic systems including inter-component and functional dependencies (cold spare, shared load, shared resources, etc.), and described by Markov models or, more generally, by discrete events dynamic systems models, the problem of sensitivity analysis remains widely open. In this paper, the perturbation method is used to estimate an importance factor, called multi-directional sensitivity measure, in the framework of Markovian systems. Some numerical examples are introduced to show why this method offers a promising tool for steady-state sensitivity analysis of Markov processes in reliability studies.
Reliability importance analysis of Markovian systems at steady state using perturbation analysis
International Nuclear Information System (INIS)
Phuc Do Van; Barros, Anne; Berenguer, Christophe
2008-01-01
Sensitivity analysis has been primarily defined for static systems, i.e. systems described by combinatorial reliability models (fault or event trees). Several structural and probabilistic measures have been proposed to assess the components importance. For dynamic systems including inter-component and functional dependencies (cold spare, shared load, shared resources, etc.), and described by Markov models or, more generally, by discrete events dynamic systems models, the problem of sensitivity analysis remains widely open. In this paper, the perturbation method is used to estimate an importance factor, called multi-directional sensitivity measure, in the framework of Markovian systems. Some numerical examples are introduced to show why this method offers a promising tool for steady-state sensitivity analysis of Markov processes in reliability studies
Steady-state numerical modeling of size effects in micron scale wire drawing
DEFF Research Database (Denmark)
Juul, Kristian Jørgensen; Nielsen, Kim Lau; Niordson, Christian Frithiof
2017-01-01
Wire drawing processes at the micron scale have received increased interest as micro wires are increasingly required in electrical components. It is well-established that size effects due to large strain gradient effects play an important role at this scale and the present study aims to quantify...... these effects for the wire drawing process. Focus will be on investigating the impact of size effects on the most favourable tool geometry (in terms of minimizing the drawing force) for various conditions between the wire/tool interface. The numerical analysis is based on a steady-state framework that enables...... convergence without dealing with the transient regime, but still fully accounts for the history dependence as-well as the elastic unloading. Thus, it forms the basis for a comprehensive parameter study. During the deformation process in wire drawing, large plastic strain gradients evolve in the contact region...
International Nuclear Information System (INIS)
Guerreiro, J.N.C.; Loula, A.F.D.
1988-12-01
The mixed Petrov-Galerkin finite element formulation is applied to transiente and steady state creep problems. Numerical analysis has shown additional stability of this method compared to classical Galerkin formulations. The accuracy of the new formulation is confirmed in some representative examples of two dimensional and axisymmetric problems. (author) [pt
Directory of Open Access Journals (Sweden)
Lun Yang
2018-04-01
Full Text Available The existing studies on probabilistic steady-state analysis of integrated energy systems (IES are limited to integrated electricity and gas networks or integrated electricity and heating networks. This paper proposes a probabilistic steady-state analysis of integrated electricity, gas and heating networks (EGH-IES. Four typical operation modes of an EGH-IES are presented at first. The probabilistic energy flow problem of the EGS-IES considering its operation modes and correlated uncertainties in wind/solar power and electricity/gas/heat loads is then formulated and solved by the Monte Carlo method based on Latin hypercube sampling and Nataf transformation. Numerical simulations are conducted on a sample EGH-IES working in the “electricity/gas following heat” mode to verify the probabilistic analysis proposed in this paper and to study the effects of uncertainties and correlations on the operation of the EGH-IES, especially uncertainty transmissions among the subnetworks.
Numerical Analysis of Dusty-Gas Flows
Saito, T.
2002-02-01
This paper presents the development of a numerical code for simulating unsteady dusty-gas flows including shock and rarefaction waves. The numerical results obtained for a shock tube problem are used for validating the accuracy and performance of the code. The code is then extended for simulating two-dimensional problems. Since the interactions between the gas and particle phases are calculated with the operator splitting technique, we can choose numerical schemes independently for the different phases. A semi-analytical method is developed for the dust phase, while the TVD scheme of Harten and Yee is chosen for the gas phase. Throughout this study, computations are carried out on SGI Origin2000, a parallel computer with multiple of RISC based processors. The efficient use of the parallel computer system is an important issue and the code implementation on Origin2000 is also described. Flow profiles of both the gas and solid particles behind the steady shock wave are calculated by integrating the steady conservation equations. The good agreement between the pseudo-stationary solutions and those from the current numerical code validates the numerical approach and the actual coding. The pseudo-stationary shock profiles can also be used as initial conditions of unsteady multidimensional simulations.
Comparison of Numerical Approaches to a Steady-State Landscape Equation
Bachman, S.; Peckham, S.
2008-12-01
A mathematical model of an idealized fluvial landscape has been developed, in which a land surface will evolve to preserve dendritic channel networks as the surface is lowered. The physical basis for this model stems from the equations for conservation of mass for water and sediment. These equations relate the divergence of the 2D vector fields showing the unit-width discharge of water and sediment to the excess rainrate and tectonic uplift on the land surface. The 2D flow direction is taken to be opposite to the water- surface gradient vector. These notions are combined with a generalized Manning-type flow resistance formula and a generalized sediment transport law to give a closed mathematical system that can, in principle, be solved for all variables of interest: discharge of water and sediment, land surface height, vertically- averaged flow velocity, water depth, and shear stress. The hydraulic geometry equations (Leopold et. al, 1964, 1995) are used to incorporate width, depth, velocity, and slope of river channels as powers of the mean-annual river discharge. Combined, they give the unit- width discharge of the stream as a power, γ, of the water surface slope. The simplified steady-state model takes into account three components among those listed above: conservation of mass for water, flow opposite the gradient, and a slope-discharge exponent γ = -1 to reflect mature drainage networks. The mathematical representation of this model appears as a second-order hyperbolic partial differential equation (PDE) where the diffusivity is inversely proportional to the square of the local surface slope. The highly nonlinear nature of this PDE has made it very difficult to solve both analytically and numerically. We present simplistic analytic solutions to this equation which are used to test the validity of the numerical algorithms. We also present three such numerical approaches which have been used in solving the differential equation. The first is based on a
Numerical bifurcation analysis of delay differential equations arising from physiological modeling.
Engelborghs, K; Lemaire, V; Bélair, J; Roose, D
2001-04-01
This paper has a dual purpose. First, we describe numerical methods for continuation and bifurcation analysis of steady state solutions and periodic solutions of systems of delay differential equations with an arbitrary number of fixed, discrete delays. Second, we demonstrate how these methods can be used to obtain insight into complex biological regulatory systems in which interactions occur with time delays: for this, we consider a system of two equations for the plasma glucose and insulin concentrations in a diabetic patient subject to a system of external assistance. The model has two delays: the technological delay of the external system, and the physiological delay of the patient's liver. We compute stability of the steady state solution as a function of two parameters, compare with analytical results and compute several branches of periodic solutions and their stability. These numerical results allow to infer two categories of diabetic patients for which the external system has different efficiency.
Directory of Open Access Journals (Sweden)
Antonio Bracale
2010-04-01
Full Text Available Distribution networks are undergoing radical changes due to the high level of penetration of dispersed generation. Dispersed generation systems require particular attention due to their incorporation of uncertain energy sources, such as wind farms, and due to the impacts that such sources have on the planning and operation of distribution networks. In particular, the foreseeable, extensive use of wind turbine generator units in the future requires that distribution system engineers properly account for their impacts on the system. Many new technical considerations must be addressed, including protection coordination, steady-state analysis, and power quality issues. This paper deals with the very short-term, steady-state analysis of a distribution system with wind farms, for which the time horizon of interest ranges from one hour to a few hours ahead. Several wind-forecasting methods are presented in order to obtain reliable input data for the steady-state analysis. Both deterministic and probabilistic methods were considered and used in performing deterministic and probabilistic load-flow analyses. Numerical applications on a 17-bus, medium-voltage, electrical distribution system with various wind farms connected at different busbars are presented and discussed.
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
Numerical flow analysis of axial flow compressor for steady and unsteady flow cases
Prabhudev, B. M.; Satish kumar, S.; Rajanna, D.
2017-07-01
Performance of jet engine is dependent on the performance of compressor. This paper gives numerical study of performance characteristics for axial compressor. The test rig is present at CSIR LAB Bangalore. Flow domains are meshed and fluid dynamic equations are solved using ANSYS package. Analysis is done for six different speeds and for operating conditions like choke, maximum efficiency & before stall point. Different plots are compared and results are discussed. Shock displacement, vortex flows, leakage patterns are presented along with unsteady FFT plot and time step plot.
Steady flow in a rotating sphere with strong precession
Kida, Shigeo
2018-04-01
The steady flow in a rotating sphere is investigated by asymptotic analysis in the limit of strong precession. The whole spherical body is divided into three regions in terms of the flow characteristics: the critical band, which is the close vicinity surrounding the great circle perpendicular to the precession axis, the boundary layer, which is attached to the whole sphere surface and the inviscid region that occupies the majority of the sphere. The analytic expressions, in the leading order of the asymptotic expansion, of the velocity field are obtained in the former two, whereas partial differential equations for the velocity field are derived in the latter, which are solved numerically. This steady flow structure is confirmed by the corresponding direct numerical simulation.
Steady-state and transient heat transfer through fins of complex geometry
Directory of Open Access Journals (Sweden)
Taler Dawid
2014-06-01
Full Text Available Various methods for steady-state and transient analysis of temperature distribution and efficiency of continuous-plate fins are presented. For a constant heat transfer coefficient over the fin surface, the plate fin can be divided into imaginary rectangular or hexangular fins. At first approximate methods for determining the steady-state fin efficiency like the method of equivalent circular fin and the sector method are discussed. When the fin geometry is complex, thus transient temperature distribution and fin efficiency can be determined using numerical methods. A numerical method for transient analysis of fins with complex geometry is developed. Transient temperature distributions in continuous fins attached to oval tubes is computed using the finite volume - finite element methods. The developed method can be used in the transient analysis of compact heat exchangers to calculate correctly the heat flow rate transferred from the finned tubes to the fluid.
Liakos, Anastasios; Malamataris, Nikolaos
2014-11-01
The topology and evolution of flow around a surface mounted cubical object in three dimensional channel flow is examined for low to moderate Reynolds numbers. Direct numerical simulations were performed via a home made parallel finite element code. The computational domain has been designed according to actual laboratory experimental conditions. Analysis of the results is performed using the three dimensional theory of separation. Our findings indicate that a tornado-like vortex by the side of the cube is present for all Reynolds numbers for which flow was simulated. A horse-shoe vortex upstream from the cube was formed at Reynolds number approximately 1266. Pressure distributions are shown along with three dimensional images of the tornado-like vortex and the horseshoe vortex at selected Reynolds numbers. Finally, and in accordance to previous work, our results indicate that the upper limit for the Reynolds number for which steady state results are physically realizable is roughly 2000. Financial support of author NM from the Office of Naval Research Global (ONRG-VSP, N62909-13-1-V016) is acknowledged.
Iler, H. Darrell; Brown, Amber; Landis, Amanda; Schimke, Greg; Peters, George
2014-01-01
A numerical analysis of the free radical addition polymerization system is described that provides those teaching polymer, physical, or advanced organic chemistry courses the opportunity to introduce students to numerical methods in the context of a simple but mathematically stiff chemical kinetic system. Numerical analysis can lead students to an…
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...
International Nuclear Information System (INIS)
Kim, Duk Sang; Cho, Yong Seok
2004-01-01
Results from an experimental study of flow distribution in a Close-coupled Catalytic Converter (CCC) are presented. The experiments were carried out with a flow measurement system specially designed for this study under steady and transient flow conditions. A pitot tube was a tool for measuring flow distribution at the exit of the first monolith. The flow distribution of the CCC was also measured by LDV system and flow visualization. Results from numerical analysis are also presented. Experimental results showed that the flow uniformity index decreases as flow Reynolds number increases. In steady flow conditions, the flow through each exhaust pipe made some flow concentrations on a specific region of the CCC inlet. The transient test results showed that the flow through each exhaust pipe in the engine firing order, interacted with each other to ensure that the flow distribution was uniform. The results of numerical analysis were qualitatively accepted with experimental results. They supported and helped explain the flow in the entry region of CCC
Contour analysis of steady state tokamak reactor performance
International Nuclear Information System (INIS)
Devoto, R.S.; Fenstermacher, M.E.
1990-01-01
A new method of analysis for presenting the possible operating space for steady state, non-ignited tokamak reactors is proposed. The method uses contours of reactor performance and plasma characteristics, fusion power gain, wall neutron flux, current drive power, etc., plotted on a two-dimensional grid, the axes of which are the plasma current I p and the normalized beta, β n = β/(I p /aB 0 ), to show possible operating points. These steady state operating contour plots are called SOPCONS. This technique is illustrated in an application to a design for the International Thermonuclear Experimental Reactor (ITER) with neutral beam, lower hybrid and bootstrap current drive. The utility of the SOPCON plots for pointing out some of the non-intuitive considerations in steady state reactor design is shown. (author). Letter-to-the-editor. 16 refs, 3 figs, 1 tab
Steady and Unsteady Analysis of NACA 0018 Airfoil in Vertical-Axis Wind Turbine
DEFF Research Database (Denmark)
Rogowski, Krzysztof; Hansen, Martin Otto Laver; Maronski, Ryszard
2018-01-01
Numerical results are presented for aerodynamic unsteady and steady airfoil characteristtcs of the NACA 0018 airfoil of a two-dimensional vertical-axis wind turbine. A geometrical model of the Darrieus-type wind turbine and the rotor operating parameters used for nurnerieal simulation are taken...
An efficient and general numerical method to compute steady uniform vortices
Luzzatto-Fegiz, Paolo; Williamson, Charles H. K.
2011-07-01
Steady uniform vortices are widely used to represent high Reynolds number flows, yet their efficient computation still presents some challenges. Existing Newton iteration methods become inefficient as the vortices develop fine-scale features; in addition, these methods cannot, in general, find solutions with specified Casimir invariants. On the other hand, available relaxation approaches are computationally inexpensive, but can fail to converge to a solution. In this paper, we overcome these limitations by introducing a new discretization, based on an inverse-velocity map, which radically increases the efficiency of Newton iteration methods. In addition, we introduce a procedure to prescribe Casimirs and remove the degeneracies in the steady vorticity equation, thus ensuring convergence for general vortex configurations. We illustrate our methodology by considering several unbounded flows involving one or two vortices. Our method enables the computation, for the first time, of steady vortices that do not exhibit any geometric symmetry. In addition, we discover that, as the limiting vortex state for each flow is approached, each family of solutions traces a clockwise spiral in a bifurcation plot consisting of a velocity-impulse diagram. By the recently introduced "IVI diagram" stability approach [Phys. Rev. Lett. 104 (2010) 044504], each turn of this spiral is associated with a loss of stability for the steady flows. Such spiral structure is suggested to be a universal feature of steady, uniform-vorticity flows.
Scott, L Ridgway
2011-01-01
Computational science is fundamentally changing how technological questions are addressed. The design of aircraft, automobiles, and even racing sailboats is now done by computational simulation. The mathematical foundation of this new approach is numerical analysis, which studies algorithms for computing expressions defined with real numbers. Emphasizing the theory behind the computation, this book provides a rigorous and self-contained introduction to numerical analysis and presents the advanced mathematics that underpin industrial software, including complete details that are missing from most textbooks. Using an inquiry-based learning approach, Numerical Analysis is written in a narrative style, provides historical background, and includes many of the proofs and technical details in exercises. Students will be able to go beyond an elementary understanding of numerical simulation and develop deep insights into the foundations of the subject. They will no longer have to accept the mathematical gaps that ex...
Investigation on steady and unsteady performance of a SCO2 centrifugal compressor with splitters
Directory of Open Access Journals (Sweden)
Guo Ding
2017-01-01
Full Text Available Supercritical carbon dioxide (SCO2 is widely concerned with its excellent physical properties. Its high density helps to achieve a compact mechanical structure, especially in all kinds of turbomachinery. In this paper, a SCO2 centrifugal compressor with splitter blades is displayed and numerically investigated. A thorough numerical analysis of the steady and unsteady performance of this SCO2 centrifugal compressor is performed in ANSYS-CFX with SST turbulence model. Streamlines, pressure and temperature under steady- and unsteady-state are compared and analyzed. Moreover, the trans-critical phenomenon at the leading edge of the rotor blade and the aerodynamic performance are covered. The results in this paper provide the foundation for the design and numerical investigation of SCO2 centrifugal compressors.
Single-channel model for steady thermal-hydraulic analysis in nuclear reactor
International Nuclear Information System (INIS)
Zhang Xiaoying; Huang Yuanyuan
2010-01-01
This article established a single-channel model for steady analysis in the reactor and an example of thermal-hydraulic analysis was made by using this model, including the Maximum heat flux density of fuel element, enthalpy, Coolant flow, various kinds of pressure drop, enthalpy increase in average tube and thermal tube. I also got the Coolant temperature distribution and the fuel element temperature distribution and analysis of the final result. The results show that some relevant parameters which we got in this paper are well coincide with the actual operating parameters. It is also show that the single-channel model can be used to the steady thermal-hydraulic analysis. (authors)
International Nuclear Information System (INIS)
Wnek, W.J.; Ramshaw, J.D.; Trapp, J.A.; Hughes, E.D.; Solbrig, C.W.
1975-11-01
A mathematical model and a numerical solution scheme for thermal-hydraulic analysis of fuel rod arrays are given. The model alleviates the two major deficiencies associated with existing rod array analysis models, that of a correct transverse momentum equation and the capability of handling reversing and circulatory flows. Possible applications of the model include steady state and transient subchannel calculations as well as analysis of flows in heat exchangers, other engineering equipment, and porous media
International Nuclear Information System (INIS)
Eoh, Jae-Hyuk; Jeong, Ji-Young; Kim, Seong-O; Hahn, Dohee; Park, Nam-Cook
2005-01-01
A quasi-steady system analysis of the sodium-water reaction (SWR) phenomena in a liquid-metal reactor (LMR) was performed using the Sodium-water reaction Event Later Phase System Transient Analyzer (SELPSTA) computer simulation code. The code has been formulated by implementing various physical assumptions to simplify the complex SWR phenomena, and it adopts the long-term mass and energy transfer (LMET) model developed in the present study. The LMET model is based on the hypothesis that the system transient can be described by the pressure and temperature transient of the cover gas space, and it can be applied only to the reaction period characterized by bulk motion. To evaluate the feasibility of the physical model and its assumptions, a scale-down mock-up test was carried out, and it was demonstrated that the numerical simulation using the LMET model adequately replicates the overall phenomena of the experiment with reasonable understanding. Based on the findings, as a numerical example, the long-term system transient responses during the SWR event of the Korea Advanced LIquid MEtal Reactor (KALIMER) were investigated, and it was found that the long-term dynamic responses are strongly dependent on the design parameters and operational strategies. As a result, the numerical simulation method developed in the present study is practicable; furthermore, the SELPSTA code is useful to resolve the risk for the SWR event
Spurious Numerical Solutions Of Differential Equations
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.
Steady ablation on the surface of a two-layer composite
Energy Technology Data Exchange (ETDEWEB)
Lin, Wen-Shan [Chung Shan Institute of Science and Technology, P.O. Box 90008-15-3, Lung-Tan, Tao-Yuan, 32526 Taiwan (China)
2005-12-01
Discovered is a quasi-steady ablation phenomenon on the surface of a two-layer composite which is formed by a layer of ablative material and another layer of non-ablative substrate. Theoretical exact solutions of quasi-steady ablation rate, the associated temperature distribution and end-of-ablation time of this two-layer composite are derived. A criterion for the occurrence of quasi-steady ablation is presented also. A one-dimensional transient numerical model is developed to perform a number of numerical experiments and hence to verify the correctness of the above theoretical solutions for the current quasi-steady ablation phenomenon. Based on the current results, a new method of measuring the ablation (or sublimation) heat is also proposed. (author)
Energy Technology Data Exchange (ETDEWEB)
Zhou, Shengcheng; Wu, Hongchun; Cao, Liangzhi; Zheng, Youqi, E-mail: yqzheng@mail.xjtu.edu.cn; Huang, Kai; He, Mingtao; Li, Xunzhao
2014-10-15
Highlights: • A new code system for design studies of accelerator driven subcritical reactors (ADSRs) is developed. • S{sub N} transport solver in triangular-z meshes, fine deletion analysis and multi-channel thermal-hydraulics analysis are coupled in the code. • Numerical results indicate that the code is reliable and efficient for design studies of ADSRs. - Abstract: Accelerator driven subcritical reactors (ADSRs) have been proposed and widely investigated for the transmutation of transuranics (TRUs). ADSRs have several special characteristics, such as the subcritical core driven by spallation neutrons, anisotropic neutron flux distribution and complex geometry etc. These bring up requirements for development or extension of analysis codes to perform design studies. A code system named LAVENDER has been developed in this paper. It couples the modules for spallation target simulation and subcritical core analysis. The neutron transport-depletion calculation scheme is used based on the homogenized cross section from assembly calculations. A three-dimensional S{sub N} nodal transport code based on triangular-z meshes is employed and a multi-channel thermal-hydraulics analysis model is integrated. In the depletion calculation, the evolution of isotopic composition in the core is evaluated using the transmutation trajectory analysis algorithm (TTA) and fine depletion chains. The new code is verified by several benchmarks and code-to-code comparisons. Numerical results indicate that LAVENDER is reliable and efficient to be applied for the steady-state analysis and reactor core design of ADSRs.
Advanced numerical methods for three dimensional two-phase flow calculations in PWR
International Nuclear Information System (INIS)
Toumi, I.; Gallo, D.; Royer, E.
1997-01-01
This paper is devoted to new numerical methods developed for three dimensional two-phase flow calculations. These methods are finite volume numerical methods. They are based on an extension of Roe's approximate Riemann solver to define convective fluxes versus mean cell quantities. To go forward in time, a linearized conservative implicit integrating step is used, together with a Newton iterative method. We also present here some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. This kind of numerical method, which is widely used for fluid dynamic calculations, is proved to be very efficient for the numerical solution to two-phase flow problems. This numerical method has been implemented for the three dimensional thermal-hydraulic code FLICA-4 which is mainly dedicated to core thermal-hydraulic transient and steady-state analysis. Hereafter, we will also find some results obtained for the EPR reactor running in a steady-state at 60% of nominal power with 3 pumps out of 4, and a thermal-hydraulic core analysis for a 1300 MW PWR at low flow steam-line-break conditions. (author)
Brezinski, C
2012-01-01
Numerical analysis has witnessed many significant developments in the 20th century. This book brings together 16 papers dealing with historical developments, survey papers and papers on recent trends in selected areas of numerical analysis, such as: approximation and interpolation, solution of linear systems and eigenvalue problems, iterative methods, quadrature rules, solution of ordinary-, partial- and integral equations. The papers are reprinted from the 7-volume project of the Journal of Computational and Applied Mathematics on '/homepage/sac/cam/na2000/index.html<
Numerical analysis of laminar forced convection in a spherical annulus
International Nuclear Information System (INIS)
Tuft, D.B.
1980-01-01
Calculations of steady laminar incompressible fluid-flow and heat transfer in a spherical annulus are presented. Steady pressures, temperatures, velocities, and heat transfer coefficients are calculated for an insulated outer sphere and a 0 0 C isothermal inner sphere with 50 0 C heated water flowing in the annulus. The inner sphere radius is 13.97 cm, the outer sphere radius is 16.83 cm and the radius ratio is 1.2. The transient axisymmetric equations of heat, mass, and momentum conservation are solved numerically in spherical coordinates. The transient solution is carried out in time until steady state is achieved. A variable mesh is used to improve resolution near the inner sphere where temperature and velocity gradients are steep. It is believed that this is the first fully two-dimensional analysis of forced flow in a spherical annulus. Local and bulk Nusselt numbers are presented for Reynolds numbers from 4.4 to 440. Computed bulk Nusselt numbers ranged from 2 to 50 and are compared to experimental results from the literature. Inlet flow jetting off the inner sphere and flow separation are predicted by the analysis. The location of wall jet separation was found to be a function of Reynolds number, indicating the location of separation depends upon the ratio of inertia to viscous forces. Wall jet separation has a pronounced effect on the distribution of local heat flux. The area between inlet and separation was found to be the most significant area for heat transfer. Radial distributions of azimuthal velocity and temperature are presented for various angles beginning at the inlet. Inner sphere pressure distribution is presented and the effect on flow separation is discussed
Yee, H. C.; Sweby, P. K.; Griffiths, D. F.
1990-01-01
Spurious stable as well as unstable steady state numerical solutions, spurious asymptotic numerical solutions of higher period, and even stable chaotic behavior can occur when finite difference methods are used to solve nonlinear differential equations (DE) numerically. The occurrence of spurious asymptotes is independent of whether the DE possesses a unique steady state or has additional periodic solutions and/or exhibits chaotic phenomena. The form of the nonlinear DEs and the type of numerical schemes are the determining factor. In addition, the occurrence of spurious steady states is not restricted to the time steps that are beyond the linearized stability limit of the scheme. In many instances, it can occur below the linearized stability limit. Therefore, it is essential for practitioners in computational sciences to be knowledgeable about the dynamical behavior of finite difference methods for nonlinear scalar DEs before the actual application of these methods to practical computations. It is also important to change the traditional way of thinking and practices when dealing with genuinely nonlinear problems. In the past, spurious asymptotes were observed in numerical computations but tended to be ignored because they all were assumed to lie beyond the linearized stability limits of the time step parameter delta t. As can be seen from the study, bifurcations to and from spurious asymptotic solutions and transitions to computational instability not only are highly scheme dependent and problem dependent, but also initial data and boundary condition dependent, and not limited to time steps that are beyond the linearized stability limit.
Theoretical numerical analysis a functional analysis framework
Atkinson, Kendall
2005-01-01
This textbook prepares graduate students for research in numerical analysis/computational mathematics by giving to them a mathematical framework embedded in functional analysis and focused on numerical analysis. This helps the student to move rapidly into a research program. The text covers basic results of functional analysis, approximation theory, Fourier analysis and wavelets, iteration methods for nonlinear equations, finite difference methods, Sobolev spaces and weak formulations of boundary value problems, finite element methods, elliptic variational inequalities and their numerical solu
Steady and dynamic states analysis of induction motor: FEA approach
African Journals Online (AJOL)
This paper deals with the steady and dynamic states analysis of induction motor using finite element analysis (FEA) approach. The motor has aluminum rotor bars and is designed for direct-on-line operation at 50 Hz. A study of the losses occurring in the motor performed at operating frequency of 50Hz showed that stator ...
Application of numerical analysis techniques to eddy current testing for steam generator tubes
International Nuclear Information System (INIS)
Morimoto, Kazuo; Satake, Koji; Araki, Yasui; Morimura, Koichi; Tanaka, Michio; Shimizu, Naoya; Iwahashi, Yoichi
1994-01-01
This paper describes the application of numerical analysis to eddy current testing (ECT) for steam generator tubes. A symmetrical and three-dimensional sinusoidal steady state eddy current analysis code was developed. This code is formulated by future element method-boundary element method coupling techniques, in order not to regenerate the mesh data in the tube domain at every movement of the probe. The calculations were carried out under various conditions including those for various probe types, defect orientations and so on. Compared with the experimental data, it was shown that it is feasible to apply this code to actual use. Furthermore, we have developed a total eddy current analysis system which consists of an ECT calculation code, an automatic mesh generator for analysis, a database and display software for calculated results. ((orig.))
Analysis of steady state creep of southeastern New Mexico bedded salt
International Nuclear Information System (INIS)
Herrmann, W.; Wawersik, W.R.; Lauson, H.S.
1980-03-01
Steady state creep rates have been obtained from a large suite of existing experimental creep data relating to bedded rock salt from the Salado formation of S.E. New Mexico. Experimental conditions covered an intermediate temperature range from 22 0 C to 200 0 C, and shear stresses from 1000 psi (7 MPa) to 6000 psi (31 MPa). An expression, based on a single diffusion controlled dislocation climb mechanism, has been found to fit the observed dependence of steady state creep rate on shear stress and temperature, yielding an activation energy of 12 kcal/mole (50 kJ/mole) and a stress exponent of 4.9. Multiple regression analysis revealed a dependence on stratigraphy, but no statistically significant dependence on pressure of specimen size. No consistent dilatancy or compaction associated with steady state creep was found, although some individual specimens dilated or compacted during creep. The steady state creep data were found to agree very well with creep data for both bedded and dome salt from a variety of other locations
Energy Technology Data Exchange (ETDEWEB)
Lee, Su Ryong [Seoul National University of Technology, Seoul (Korea, Republic of)
2014-06-15
Nonlinear characteristics of cellular counterflow diffusion flame near the radiative extinction limit at large Damköhler number are numerically investigated. Lewis number is assumed to be 0.5 and flame evolution is calculated by imposing an infinitesimal disturbance to a one-dimensional(1-D) steady state flame. The early stage of nonlinear development is very similar to that predicted in a linear stability analysis. The disturbance with the wavenumber of the fastest growing mode emerges and grows gradually. Eventual, an alternating pattern of reacting and quenching stripes is developed. The cellular flame temperature is higher than that of 1-D flame because of the gain of the total enthalpy. As the Damköhler number is further increased, the shape of the cell becomes circular to increase the surface area per unit reacting volume. The cellular flames do not extinguish but survive even above the 1-D steady state extinction condition.
Do's and don'ts in Fourier analysis of steady-state potentials.
Bach, M; Meigen, T
1999-01-01
Fourier analysis is a powerful tool in signal analysis that can be very fruitfully applied to steady-state evoked potentials (flicker ERG, pattern ERG, VEP, etc.). However, there are some inherent assumptions in the underlying discrete Fourier transform (DFT) that are not necessarily fulfilled in typical electrophysiological recording and analysis conditions. Furthermore, engineering software-packages may be ill-suited and/or may not fully exploit the information of steady-state recordings. Specifically: * In the case of steady-state stimulation we know more about the stimulus than in standard textbook situations (exact frequency, phase stability), so 'windowing' and calculation of the 'periodogram' are not necessary. * It is mandatory to choose an integer relationship between sampling rate and frame rate when employing a raster-based CRT stimulator. * The analysis interval must comprise an exact integer number (e.g., 10) of stimulus periods. * The choice of the number of stimulus periods per analysis interval needs a wise compromise: A high number increases the frequency resolution, but makes artifact removal difficult; a low number 'spills' noise into the response frequency. * There is no need to feel tied to a power-of-two number of data points as required by standard FFT, 'resampling' is an easy and efficient alternative. * Proper estimates of noise-corrected Fourier magnitude and statistical significance can be calculated that take into account the non-linear superposition of signal and noise. These aspects are developed in an intuitive approach with examples using both simulations and recordings. Proper use of Fourier analysis of our electrophysiological records will reduce recording time and/or increase the reliability of physiologic or pathologic interpretations.
International Nuclear Information System (INIS)
Li, Baoren; Gao, Longlong; Yang, Gang
2013-01-01
Highlights: ► A novel energy saving high-pressure electro-pneumatic servo valve is presented. ► An evaluated method for steady gas flow forces on pneumatic valves is proposed. ► Gas jet angles at the orifices for the valve are larger than 69° commonly used. ► The steady gas flow force is strongly nonlinear with valve opening. ► The steady gas flow force is compensated and the aim at energy saving is realized. - Abstract: A novel voice coil motor (VCM) direct drive single stage high-pressure pneumatic servo valve is designed, and then the steady gas flow force acting on the spool of the servo valve is investigated by numerical simulation and experimental methods in this paper. At present, many studies about flow force are concentrated mainly on hydraulic valves, but rarely on pneumatic valves. However, the velocity of gas is up to sonic when high-pressure gas flows through the servo valve orifice. And therefore, the steady gas flow force, generated by high pressure and high speed gas flow, cannot be neglected and is an important disturbance for the VCM direct-drive single stage high-pressure pneumatic servo valve. Consequently, the numerical simulation with computational fluid dynamics (CFD) is adopted to analyze the flow filed, jet angles, and steady gas flow forces for the servo valve with different valve openings and inlet pressures. The experimental study is performed to evaluate and confirm the numerical analysis. Then the compensated approach is proposed to reduce the steady gas flow force for the servo valve, changing the angle of non-metering port designed in the valve sleeve to the spool axis. The results demonstrate that the presented numerical analysis method is validated, the gas jet angle for the servo valve orifice is more than 69° and varies with different spool openings, and the steady gas flow force is nonlinear with valve opening and linear with inlet pressure when the outlet boundary is atmospheric pressure. Moreover, the steady gas
Thermodynamic Analysis of Closed Steady or Cyclic Systems
Directory of Open Access Journals (Sweden)
Jim McGovern
2015-09-01
Full Text Available Closed, steady or cyclic thermodynamic systems, which have temperature variations over their boundaries, can represent an extremely large range of plants, devices or natural objects, such as combined heating, cooling and power plants, computers and data centres, and planets. Energy transfer rates can occur across the boundary, which are characterized as heat or work. We focus on the finite time thermodynamics aspects, on energy-based performance parameters, on rational efficiency and on the environmental reference temperature. To do this, we examine the net work rate of a closed, steady or cyclic system bounded by thermal resistances linked to isothermal reservoirs in terms of the first and second laws of thermodynamics. Citing relevant references from the literature, we propose a methodology that can improve the thermodynamic analysis of an energy-transforming or an exergy-destroying plant. Through the reflections and analysis presented, we have found an explanation of the second law that clarifies the link between the Clausius integral of heat over temperature and the reference temperature of the Gouy–Stodola theorem. With this insight and approach, the specification of the environmental reference temperature in exergy analysis becomes more solid. We have explained the relationship between the Curzon Ahlborn heat engine and an irreversible Carnot heat engine. We have outlined the nature of subsystem rational efficiencies and have found Rant’s anergy to play an important role. We postulate that heat transfer through thermal resistance is the sole basis of irreversibility.
Numerical analysis of mixing process of two component gases in vertical fluid layer
International Nuclear Information System (INIS)
Hatori, Hirofumi; Takeda, Tetsuaki; Funatani, Shumpei
2015-01-01
When the depressurization accident occurs in the Very-High-Temperature Reactor (VHTR), it is expected that air enter into the reactor core. Therefore, it is important to know a mixing process of different kind of gases in the stable or unstable stratified fluid layer. Especially, it is also important to examine an influence of localized natural convection and molecular diffusion on mixing process from a viewpoint of safety. In order to research the mixing process of two component gases and flow characteristics of the localized natural convection, we have carried out numerical analysis using three dimensional CFD code. The numerical model was consisted of a storage tank and a reverse U-shaped vertical slot. They were separated by a partition plate. One side of the left vertical fluid layer was heated and the other side was cooled. The right vertical fluid layer was also cooled. The procedure of numerical analysis is as follows. Firstly, the storage tank was filled with heavy gas and the reverse U-shaped vertical slot was filled with light gas. In the left vertical fluid layer, the localized natural convection was generated by the temperature difference between the vertical walls. The flow characteristics were obtained by a steady state analysis. The unsteady state analysis was started when the partition plate was opened. The gases were mixed by molecular diffusion and natural convection. After the time elapsed, natural circulation occurred. The result obtained in this numerical analysis is as follows. The temperature difference of the left vertical fluid layer was set to 100 K. The combination of the mixed gas was nitrogen and argon. After 76 minutes elapsed, natural circulation occurred. (author)
Directory of Open Access Journals (Sweden)
Zhentao Wang
2014-07-01
Full Text Available A model based on the volume of fluid (VOF method and leaky dielectric theory is established to predict the deformation and internal flow of the droplet suspended in another vicious fluid under the influence of the electric field. Through coupling with hydrodynamics and electrostatics, the rate of deformation and internal flow of the single droplet are simulated and obtained under the different operating parameters. The calculated results show that the direction of deformation and internal flow depends on the physical properties of fluids. The numerical results are compared with Taylor's theory and experimental results by Torza et al. When the rate of deformation is small, the numerical results are consistent with theory and experimental results, and when the rate is large the numerical results are consistent with experimental results but are different from Taylor's theory. In addition, fluid viscosity hardly affects the deformation rate and mainly dominates the deformation velocity. For high viscosity droplet spends more time to attain the steady state. The conductivity ratio and permittivity ratio of two different liquids affect the direction of deformation. When fluid electric properties change, the charge distribution at the interface is various, which leads to the droplet different deformation shapes.
Steady Method for the Analysis of Evaporation Dynamics.
Günay, A Alperen; Sett, Soumyadip; Oh, Junho; Miljkovic, Nenad
2017-10-31
Droplet evaporation is an important phenomenon governing many man-made and natural processes. Characterizing the rate of evaporation with high accuracy has attracted the attention of numerous scientists over the past century. Traditionally, researchers have studied evaporation by observing the change in the droplet size in a given time interval. However, the transient nature coupled with the significant mass-transfer-governed gas dynamics occurring at the droplet three-phase contact line makes the classical method crude. Furthermore, the intricate balance played by the internal and external flows, evaporation kinetics, thermocapillarity, binary-mixture dynamics, curvature, and moving contact lines makes the decoupling of these processes impossible with classical transient methods. Here, we present a method to measure the rate of evaporation of spatially and temporally steady droplets. By utilizing a piezoelectric dispenser to feed microscale droplets (R ≈ 9 μm) to a larger evaporating droplet at a prescribed frequency, we can both create variable-sized droplets on any surface and study their evaporation rate by modulating the piezoelectric droplet addition frequency. Using our steady technique, we studied water evaporation of droplets having base radii ranging from 20 to 250 μm on surfaces of different functionalities (45° ≤ θ a,app ≤ 162°, where θ a,app is the apparent advancing contact angle). We benchmarked our technique with the classical unsteady method, showing an improvement of 140% in evaporation rate measurement accuracy. Our work not only characterizes the evaporation dynamics on functional surfaces but also provides an experimental platform to finally enable the decoupling of the complex physics governing the ubiquitous droplet evaporation process.
Introductory numerical analysis
Pettofrezzo, Anthony J
2006-01-01
Written for undergraduates who require a familiarity with the principles behind numerical analysis, this classical treatment encompasses finite differences, least squares theory, and harmonic analysis. Over 70 examples and 280 exercises. 1967 edition.
Anastassiou, George A
2015-01-01
This is the first numerical analysis text to use Sage for the implementation of algorithms and can be used in a one-semester course for undergraduates in mathematics, math education, computer science/information technology, engineering, and physical sciences. The primary aim of this text is to simplify understanding of the theories and ideas from a numerical analysis/numerical methods course via a modern programming language like Sage. Aside from the presentation of fundamental theoretical notions of numerical analysis throughout the text, each chapter concludes with several exercises that are oriented to real-world application. Answers may be verified using Sage. The presented code, written in core components of Sage, are backward compatible, i.e., easily applicable to other software systems such as Mathematica®. Sage is open source software and uses Python-like syntax. Previous Python programming experience is not a requirement for the reader, though familiarity with any programming language is a p...
Numerical Simulation of Steady Supercavitating Flows
Ali Jafarian; Ahmad-Reza Pishevar
2016-01-01
In this research, the Supercavitation phenomenon in compressible liquid flows is simulated. The one-fluid method based on a new exact two-phase Riemann solver is used for modeling. The cavitation is considered as an isothermal process and a consistent equation of state with the physical behavior of the water is used. High speed flow of water over a cylinder and a projectile are simulated and the results are compared with the previous numerical and experimental results. The cavitation bubble p...
Well balancing of the SWE schemes for moving-water steady flows
Caleffi, Valerio; Valiani, Alessandro
2017-08-01
In this work, the exact reproduction of a moving-water steady flow via the numerical solution of the one-dimensional shallow water equations is studied. A new scheme based on a modified version of the HLLEM approximate Riemann solver (Dumbser and Balsara (2016) [18]) that exactly preserves the total head and the discharge in the simulation of smooth steady flows and that correctly dissipates mechanical energy in the presence of hydraulic jumps is presented. This model is compared with a selected set of schemes from the literature, including models that exactly preserve quiescent flows and models that exactly preserve moving-water steady flows. The comparison highlights the strengths and weaknesses of the different approaches. In particular, the results show that the increase in accuracy in the steady state reproduction is counterbalanced by a reduced robustness and numerical efficiency of the models. Some solutions to reduce these drawbacks, at the cost of increased algorithm complexity, are presented.
Directory of Open Access Journals (Sweden)
Qian Hong
2008-05-01
Full Text Available Abstract Background: Several approaches, including metabolic control analysis (MCA, flux balance analysis (FBA, correlation metric construction (CMC, and biochemical circuit theory (BCT, have been developed for the quantitative analysis of complex biochemical networks. Here, we present a comprehensive theory of linear analysis for nonequilibrium steady-state (NESS biochemical reaction networks that unites these disparate approaches in a common mathematical framework and thermodynamic basis. Results: In this theory a number of relationships between key matrices are introduced: the matrix A obtained in the standard, linear-dynamic-stability analysis of the steady-state can be decomposed as A = SRT where R and S are directly related to the elasticity-coefficient matrix for the fluxes and chemical potentials in MCA, respectively; the control-coefficients for the fluxes and chemical potentials can be written in terms of RT BS and ST BS respectively where matrix B is the inverse of A; the matrix S is precisely the stoichiometric matrix in FBA; and the matrix eAt plays a central role in CMC. Conclusion: One key finding that emerges from this analysis is that the well-known summation theorems in MCA take different forms depending on whether metabolic steady-state is maintained by flux injection or concentration clamping. We demonstrate that if rate-limiting steps exist in a biochemical pathway, they are the steps with smallest biochemical conductances and largest flux control-coefficients. We hypothesize that biochemical networks for cellular signaling have a different strategy for minimizing energy waste and being efficient than do biochemical networks for biosynthesis. We also discuss the intimate relationship between MCA and biochemical systems analysis (BSA.
Quasi-steady state natural convection in a tilted porous layer
Energy Technology Data Exchange (ETDEWEB)
Robillard, L.; Vasseur, P. (Ecole Polytechnique, Montreal, PQ (Canada))
1992-12-01
Natural convection in an inclined porous layer heated or cooled on one side, when its other walls are insulated, has several important engineering applications. These include solar power collection, regenerative heat exchangers, and high performance insulation for buildings and cold storage. Although the problem is basically an unsteady state one, it is known that if the heating (or cooling) process is maintained for a sufficiently long time, a quasi-steady state is approached. Quasi-steady state laminar natural convection in an inclined porous layer is studied analytically and numerically. On the basis of the Darcy-Oberbeck-Boussinesq equations, the problem is solved analytically in the limit of a thin porous layer heated on one side by a heat flux while the other boundaries are maintained adiabatic. For quasi-steady state, the flow and temperature fields overall heat transfer rates are obtained in terms of the controlling parameters and the onset of convection in a bottom heated horizantal system is predicted. It is also demonstrated for the case of a bottom-heated layer that for sufficiently small inclinations, multiple unicellular quasi-steady states exist, some of which are unstable. A numerical study of the same phenomenon, obtained by solving the complete set of governing equations, is conducted. Good agreement is found between the analytical predictions and the numerical simulation. 22 refs., 6 figs.
Analysis on the steady-state coherent synchrotron radiation with strong shielding
International Nuclear Information System (INIS)
Li, R.; Bohn, C.L.; Bisognano, J.J.
1997-01-01
There are several papers concerning shielding of coherent synchrotron radiation (CSR) emitted by a Gaussian line charge on a circular orbit centered between two parallel conducting plates. Previous asymptotic analyses in the frequency domain show that shielded steady-state CSR mainly arises from harmonics in the bunch frequency exceeding the threshold harmonic for satisfying the boundary conditions at the plates. In this paper the authors extend the frequency-domain analysis into the regime of strong shielding, in which the threshold harmonic exceeds the characteristic frequency of the bunch. The result is then compared to the shielded steady-state CSR power obtained using image charges
International Nuclear Information System (INIS)
Kaminaga, Masanori
1997-03-01
JRR-3 is a light water moderated and cooled, beryllium and heavy water reflected pool type research reactor using low enriched uranium (LEU) plate-type fuels. Its thermal power is 20 MW. The core conversion program from uranium-aluminum (UAl x -Al) dispersion type fuel (aluminide fuel) to uranium-silicon-aluminum (U 3 Si 2 -Al) dispersion type fuel (silicide fuel) is currently conducted at the JRR-3. This report describes about the steady-state thermal hydraulic analysis results and the flow channel blockage accident analysis result. In JRR-3, there are two operation mode. One is high power operation mode up to 20 MW, under forced convection cooling using the primary and the secondary cooling systems. The other is low power operation mode up to 200 kW, under natural circulation cooling between the reactor core and the reactor pool without the primary and the secondary cooling systems. For the analysis of the flow channel blockage accident, COOLOD code was used. On the other hand, steady-state thermal hydraulic analysis for both of the high power operation mode under forced convection cooling and low power operation under natural convection cooling, COOLOD-N2 code was used. From steady-state thermal hydraulic analysis results of both forced and natural convection cooling, fuel temperature, minimum DNBR etc. meet the design criteria and JRR-3 LEU silicide core has enough safety margin under normal operation conditions. Furthermore, flow channel blockage accident analysis results show that one channel flow blockage accident meet the safety criteria for accident conditions which have been established for JRR-3 LEU silicide core. (author)
Energy Technology Data Exchange (ETDEWEB)
Dhole, S.D.; Chhabra, R.P. [Department of Chemical Engineering, Indian Institute of Technology, Kanpur 208 016 (India); Eswaran, V. [Department of Mechanical Engineering, Indian Institute of Technology, Kanpur 208 016 (India)
2006-03-15
The effects of Reynolds and Prandtl numbers on the heat transfer characteristics of an unconfined sphere for different thermal boundary conditions (isothermal and isoflux) on the sphere surface have been investigated numerically by using a finite volume method for the range of conditions as 5=
Steady 3D Numerical Simulation of the Evaporator and Compensation Chamber of a Loop Heat Pipe
Directory of Open Access Journals (Sweden)
A. V. Nedayvozov
2017-01-01
Full Text Available The paper presents results of a steady three-dimensional numerical simulation of a flat evaporator and compensation chamber (CC of a loop heat pipe (LHP and describes a procedure of the thermal state calculation of the evaporator and the compensation chamber.The LHP is an efficient heat transfer device operating on the principle of evaporation-condensation cycle. It is successfully used in space technology and also to cool the heat-stressed components of electronic devices and computer equipment. The authors carried out a numerical study of the influence of the condensate pipeline length, immersed in water, on the thermal state of the evaporator and the compensation chamber. The paper shows the influence of the mass forces field on the calculation results. Presents all the numerical studies carried out by the authors for a brass flat evaporator with a thermal load of 80 W. Water is used as a LHP heat-transfer fluid. Fields of temperature, pressure and velocity are presented for each design option.Based on the calculation results, the authors came to the following conclusions:Influence of the mass forces field for the LHP of this type is significant and leads to arising water vortex flow in the condensate pipeline and CC, thereby mixing and equalizing the water temperature in the CC and in the porous element, reducing the maximum temperature of the porous element;The increasing section length of the condensate pipeline in the CC leads to increasing velocity of the heat-transfer fluid in the CC and in the porous element, decreasing mixing zone of the condensate in the CC, and increasing temperature non-uniformity of the porous element.
Bosma, T; Pikkemaat, MG; Kingma, Jacob; Dijk, J; Janssen, DB
2003-01-01
Haloalkane dehalogenase from Rhodococcus rhodochrous NCIMB 13064 (DhaA) catalyzes the hydrolysis of carbon-halogen bonds in a wide range of haloalkanes. We examined the steady-state and pre-steady-state kinetics of halopropane conversion by DhaA to illuminate mechanistic details of the
Dynamic optimization of a FCC converter unit: numerical analysis
Directory of Open Access Journals (Sweden)
E. Almeida Nt
2011-03-01
Full Text Available Fluidized-bed Catalytic Cracking (FCC is a process subject to frequent variations in the operating conditions (including feed quality and feed rate. The production objectives usually are the maximization of LPG and gasoline production. This fact makes the FCC converter unit an excellent opportunity for real-time optimization. The present work aims to apply a dynamic optimization in an industrial FCC converter unit, using a mechanistic dynamic model, and to carry out a numerical analysis of the solution procedure. A simultaneous approach was used to discretize the system of differential-algebraic equations and the resulting large-scale NLP problem was solved using the IPOPT solver. This study also does a short comparison between the results obtained by a potential dynamic real-time optimization (DRTO against a possible steady-state real-time optimization (RTO application. The results demonstrate that the application of dynamic real-time optimization of a FCC converter unit can bring significant benefits in production.
Steady State Thermo-Hydrodynamic Analysis of Two-Axial groove and Multilobe Hydrodynamic Bearings
Directory of Open Access Journals (Sweden)
C. Bhagat
2014-12-01
Full Text Available Steady state thermo-hydrodynamic analysis of two axial groove and multi lobe oil journal bearings is performed in this paper. To study the steady state thermo-hydrodynamic characteristics Reynolds equation is solved simultaneously along with the energy equation and heat conduction equation in bush and shaft. The effect of groove geometry, cavitation in the fluid film, the recirculation of lubricant, shaft speed has also been taken into account. Film temperature in case of three-lobe bearing is found to be high as compared to other studied bearing configurations. The data obtained from this analysis can be used conveniently in the design of such bearings, which are presented in dimensionless form.
Numerical analysis of an air condenser working with the refrigerant fluid R407C
International Nuclear Information System (INIS)
Aprea, Ciro; Maiorino, Angelo
2007-01-01
As CFC (clorofluorocarbon) and HCFC (hydrochlorofluorocarbon) refrigerants which have been used as refrigerants in a vapour compression refrigeration system were know to provide a principal cause to ozone depletion and global warming, production and use of these refrigerants have been restricted. Therefore, new alternative refrigerants should be searched for, which fit to the requirements in an air conditioner or a heat pump, and refrigerant mixtures which are composed of HFC (hydrofluorocarbon) refrigerants having zero ODP (ozone depletion potential) are now being suggested as drop-in or mid-term replacement. However also these refrigerants, as the CFC and HCFC refrigerants, present a greenhouse effect. The zeotropic mixture designated as R407C (R32/R125/R134a 23/25/52% in mass) represents a substitute of the HCFC22 for high evaporation temperature applications as the air-conditioning. Aim of the paper is a numerical-experimental analysis for an air condenser working with the non azeotropic mixture R407C in steady-state conditions. A homogeneous model for the condensing refrigerant is considered to forecast the performances of the condenser; this model is capable of predicting the distributions of the refrigerant temperature, the velocity, the void fraction, the tube wall temperature and the air temperature along the test condenser. Obviously in the refrigerant de-superheating phase the numerical analysis becomes very simple. A comparison with the measurements on an air condenser mounted in an air channel linked to a vapour compression plant is discussed. The results show that the simplified model provides a reasonable estimation of the steady-state response and that this model is useful to design purposes
The quasi-steady state of all-vanadium redox flow batteries: A scale analysis
International Nuclear Information System (INIS)
Sharma, A.K.; Vynnycky, M.; Ling, C.Y.; Birgersson, E.; Han, M.
2014-01-01
Highlights: • We present a transient 2D model for a VRFB (conservation of species and charge); • Carry out scale analysis of the species conservation equation; • Derive the condition characterizing the quasi-steadiness of VRFB operation; • Verify it by comparing charge-discharge curve with transient simulations. - Abstract: In general, mathematical models for all-vanadium redox flow batteries (VRFB) that seek to capture the transport phenomena are transient in nature. In this paper, we carry out scale analysis of VRFB operation and derive the conditions when it can be assumed to be quasi-steady state in nature, i.e., time-dependence only through a boundary condition. We find that it is true for typical tank volume and flow rate employed for VRFBs. The proposed analysis is generic and can also be employed for other types of redox flow batteries
Steady and unsteady experimental analysis of a turbocharger for automotive applications
International Nuclear Information System (INIS)
Bontempo, R.; Cardone, M.; Manna, M.; Vorraro, G.
2015-01-01
Highlights: • Steady and unsteady characteristics of a turbocharger are analysed by experimental means. • The steady state characteristic maps are obtained for both the compressor and the turbine. • The validity of the classical adiabatic assumption is questioned. • The compressor efficiency evaluated through the adiabatic assumption may lead to a 5–10% relative error. • The mild and deep compressor surge phenomena have been experimentally investigated. - Abstract: The paper describes the steady and unsteady performance characteristics of a small size turbocharger typically employed in automotive downsized engine applications. The analysis is carried out by experimental means using an innovative hot gas generator system specifically designed for turbocharger testing which is capable of delivering a wide range of flow rates with adequate thermodynamic characteristics. More in detail, the gas generator consists of a medium size direct injection compression ignition Internal Combustion Engine (ICE) feeding the turbine of the test article. To independently set the hot gas mass flow rate and the turbine inlet temperature, the operating parameters of the aforementioned ICE are specified through an electronic control unit in a fully automated manner. Compared to previously presented data [1] (Energy Procedia, vol. 45, pp 1116-1125, 2014), those reported herein have been collected with the help of newly installed equipment and controlling software allowing for the estimation of the thermal power transferred from the turbocharger to the environment. In particular, thanks to a first law analysis, the collected measurements have shown that the algebraic sum of the thermal power transferred to the lubricating oil as well as to the environment is roughly speaking 20–30% of the compressor total enthalpy change per unit time. Moreover, it has been shown that evaluating the compressor efficiency through classical expression based on the adiabatic assumption leads to
Theoretical analysis of steady state operating forces in control valves
Directory of Open Access Journals (Sweden)
Basavaraj Hubballi
2018-01-01
Full Text Available The controlling components, such as valves are used to regulate controlled fluid power. It is not always possible to calculate valve forces accurately, and with some types of valves even the existence of certain types of forces cannot be predicted with certainty. In many cases, however, the analysis can be made fairly completely and accurately. The assumption of steady state conditions is valid for the valve alone, but transient effects in the rest of the system may be large. These effects are particularly important with regard to the instability of valves, where the system may react on the valve in such a way as to make it squeal or oscillate, sometimes with large amplitude. The origin of the steady state flow force understood from a brief qualitative explanation. The following paper will summarize much of what is known about valve forces in the spool type controlling element.
York, B. J.; Sinha, N.; Dash, S. M.; Hosangadi, A.; Kenzakowski, D. C.; Lee, R. A.
1992-07-01
The analysis of steady and transient aerodynamic/propulsive/plume flowfield interactions utilizing several state-of-the-art computer codes (PARCH, CRAFT, and SCHAFT) is discussed. These codes have been extended to include advanced turbulence models, generalized thermochemistry, and multiphase nonequilibrium capabilities. Several specialized versions of these codes have been developed for specific applications. This paper presents a brief overview of these codes followed by selected cases demonstrating steady and transient analyses of conventional as well as advanced missile systems. Areas requiring upgrades include turbulence modeling in a highly compressible environment and the treatment of particulates in general. Recent progress in these areas are highlighted.
Theory of steady state plasma flow and confinement in a periodic magnetic field
International Nuclear Information System (INIS)
Brown, M.G.
1981-02-01
The steady flow of plasmas through spatially periodic magnetic fields is examined, and a theoretical model is developed for the case of axisymmetric geometry. The externally applied magnetic fields can be cusps or mirrors joined end to end; electrons are then localised by these fields because of their small Larmor radius, while the ions can traverse the magnetic mirrors. The properties of the model equations are studied and dimensionless parameters which appear are interpreted. Numerical methods used in steady flow applications are reviewed, and some techniques of solution for the model equations are discussed. A solution method involving numerical integration of time-dependent equations is described, which approaches the steady state asymptotically; results from this method are presented and compared with the results from perturbation theory. (author)
MI-Sim: A MATLAB package for the numerical analysis of microbial ecological interactions.
Directory of Open Access Journals (Sweden)
Matthew J Wade
Full Text Available Food-webs and other classes of ecological network motifs, are a means of describing feeding relationships between consumers and producers in an ecosystem. They have application across scales where they differ only in the underlying characteristics of the organisms and substrates describing the system. Mathematical modelling, using mechanistic approaches to describe the dynamic behaviour and properties of the system through sets of ordinary differential equations, has been used extensively in ecology. Models allow simulation of the dynamics of the various motifs and their numerical analysis provides a greater understanding of the interplay between the system components and their intrinsic properties. We have developed the MI-Sim software for use with MATLAB to allow a rigorous and rapid numerical analysis of several common ecological motifs. MI-Sim contains a series of the most commonly used motifs such as cooperation, competition and predation. It does not require detailed knowledge of mathematical analytical techniques and is offered as a single graphical user interface containing all input and output options. The tools available in the current version of MI-Sim include model simulation, steady-state existence and stability analysis, and basin of attraction analysis. The software includes seven ecological interaction motifs and seven growth function models. Unlike other system analysis tools, MI-Sim is designed as a simple and user-friendly tool specific to ecological population type models, allowing for rapid assessment of their dynamical and behavioural properties.
MI-Sim: A MATLAB package for the numerical analysis of microbial ecological interactions.
Wade, Matthew J; Oakley, Jordan; Harbisher, Sophie; Parker, Nicholas G; Dolfing, Jan
2017-01-01
Food-webs and other classes of ecological network motifs, are a means of describing feeding relationships between consumers and producers in an ecosystem. They have application across scales where they differ only in the underlying characteristics of the organisms and substrates describing the system. Mathematical modelling, using mechanistic approaches to describe the dynamic behaviour and properties of the system through sets of ordinary differential equations, has been used extensively in ecology. Models allow simulation of the dynamics of the various motifs and their numerical analysis provides a greater understanding of the interplay between the system components and their intrinsic properties. We have developed the MI-Sim software for use with MATLAB to allow a rigorous and rapid numerical analysis of several common ecological motifs. MI-Sim contains a series of the most commonly used motifs such as cooperation, competition and predation. It does not require detailed knowledge of mathematical analytical techniques and is offered as a single graphical user interface containing all input and output options. The tools available in the current version of MI-Sim include model simulation, steady-state existence and stability analysis, and basin of attraction analysis. The software includes seven ecological interaction motifs and seven growth function models. Unlike other system analysis tools, MI-Sim is designed as a simple and user-friendly tool specific to ecological population type models, allowing for rapid assessment of their dynamical and behavioural properties.
A new coupled map car-following model considering drivers' steady desired speed
International Nuclear Information System (INIS)
Zhou Tong; Sun Di-Hua; Li Hua-Min; Liu Wei-Ning
2014-01-01
Based on the pioneering work of Konishi et al., in consideration of the influence of drivers' steady desired speed effect on the traffic flow, we develop a new coupled map car-following model in the real world. By use of the control theory, the stability condition of our model is derived. The validity of the present theoretical scheme is verified via numerical simulation, confirming the correctness of our theoretical analysis. (general)
Calculation analysis on steady state natural circulation characteristics
International Nuclear Information System (INIS)
Wang Fei; Nie Changhua; Huang Yanping
2005-01-01
The calculation results of single-phase steady state natural circulation characteristics by using Retran02 code have been presented, good agreement is achieved between the verified calculation result and the experimental data which were conducted at a test facility. Based on the calculation model, some sensibility analyses were made and much deeper understanding for single-phase steady state natural circulation characteristics was obtained. (author)
Identification of Steady and Non-Steady Gait of Humanexoskeleton Walking System
Żur, K. K.
2013-08-01
In this paper a method of analysis of exoskeleton multistep locomotion was presented by using a computer with the preinstalled DChC program. The paper also presents a way to analytically calculate the ",motion indicator", as well as the algorithm calculating its two derivatives. The algorithm developed by the author processes data collected from the investigation and then a program presents the obtained final results. Research into steady and non-steady multistep locomotion can be used to design two-legged robots of DAR type and exoskeleton control system
Hanoca, P.; Ramakrishna, H. V.
2018-03-01
This work is related to develop a methodology to model and simulate the TEHD using the sequential application of CFD and CSD. The FSI analyses are carried out using ANSYS Workbench. In this analysis steady state, 3D Navier-Stoke equations along with energy equation are solved. Liquid properties are introduced where the viscosity and density are the function of pressure and temperature. The cavitation phenomenon is adopted in the analysis. Numerical analysis has been carried at different speeds and surfaces temperatures. During the analysis, it was found that as speed increases, hydrodynamic pressures will also increases. The pressure profile obtained from the Roelands equation is more sensitive to the temperature as compared to the Barus equation. The stress distributions specify the significant positions in the bearing structure. The developed method is capable of giving latest approaching into the physics of elasto hydrodynamic lubrication.
International Nuclear Information System (INIS)
Lenarcic, M; Eichhorn, M; Schoder, S J; Bauer, Ch
2015-01-01
In this work the incompressible turbulent flow in a high head Francis turbine under steady operating conditions is investigated using the open source CFD software package FOAM-extend- 3.1. By varying computational domains (cyclic model, full model), coupling methods between stationary and rotating frames (mixing-plane, frozen-rotor) and turbulence models (kω-SST, κε), numerical flow simulations are performed at the best efficiency point as well as at operating points in part load and high load. The discretization is adjusted according the y + -criterion with y + mean > 30. A grid independence study quantifies the discretization error and the corresponding computational costs for the appropriate simulations, reaching a GCI < 1% for the chosen grid. Specific quantities such as efficiency, head, runner shaft torque as well as static pressure and velocity components are computed and compared with experimental data and commercial code. Focusing on the computed results of integral quantities and static pressures, the highest level of accuracy is obtained using FOAM in combination with the full model discretization, the mixing-plane coupling method and the κω-SST turbulence model. The corresponding relative deviations regarding the efficiency reach values of Δη rel ∼ 7% at part load, Δη rel ∼ 0.5% at best efficiency point and Δη rel ∼ 5.6% at high load. The computed static pressures deviate from the measurements by a maximum of Δp rel = 9.3% at part load, Δp rel = 4.3% at best efficiency point and Δp rel = 6.7% at high load. Commercial code in turn yields slightly better predictions for the velocity components in the draft tube cone, reaching a good accordance with the measurements at part load. Although FOAM also shows an adequate correspondence to the experimental data at part load, local effects near the runner hub are captured less accurate at best efficiency point and high load. Nevertheless, FOAM is a reasonable alternative to commercial code
Numerical Analysis of Turbulent Flow around Tube Bundle by Applying CAD Best Practice Guideline
International Nuclear Information System (INIS)
Lee, Gong Hee; Bang, Young Seok; Woo, Sweng Woong; Cheng, Ae Ju
2013-01-01
In this study, the numerical analysis of a turbulent flow around both a staggered and an incline tube bundle was conducted using Annoys Cfx V. 13, a commercial CAD software. The flow was assumed to be steady, incompressible, and isothermal. According to the CAD Best Practice Guideline, the sensitivity study for grid size, accuracy of the discretization scheme for convection term, and turbulence model was conducted, and its result was compared with the experimental data to estimate the applicability of the CAD Best Practice Guideline. It was concluded that the CAD Best Practice Guideline did not always guarantee an improvement in the prediction performance of the commercial CAD software in the field of tube bundle flow
Steady-State and Transient Analysis for Design Validation of SMART-ITL Secondary System
Energy Technology Data Exchange (ETDEWEB)
Yun, Eunkoo; Bae, Hwang; Ryu, Sung Uk; Jeon, Byong-Guk; Yang, Jin-Hwa; Yi, Sung-Jae; Park, Hyun-Sik [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2016-10-15
SMART can prevent large-break loss of coolant accident (LBLOCA) inherently. SMART-ITL is an experimental simulation facility designed to perform integral effect tests for the SMART plant. In terms of the secondary system of SMART-ITL, the design has been simplified from that of reference plant by replacing several components, such as expansion device and condenser, with an appropriate device to be functional as the alternatives. In this paper, in order to understand the operational characteristics as well as design concept, the secondary system of SMRAT-ITL is analyzed in steady-state and transient aspects, and the results are compared with relevant experimental results. This study focuses on the understanding of thermal-hydraulic behavior of SMART-ITL secondary system, which is simplified from that of reference plant. To identify the behaviors of the secondary system, the steady-state and transient analysis were conducted based on experimental results. In steady-state analysis, the results clearly showed that the system pressure is related to the temperature of condensation tank which varies depending on mixture enthalpy. In transient analysis, the dynamic behavior during heat-up process has been investigated. The results reveal that we can reasonably assume the fluid filled in TK-CD-01 be in a saturated condition. The results showed that the design of SMART-ITL secondary system is appropriate, and the system is being properly operated to match the design intent.
Integrated stoichiometric, thermodynamic and kinetic modelling of steady state metabolism.
Fleming, R M T; Thiele, I; Provan, G; Nasheuer, H P
2010-06-07
The quantitative analysis of biochemical reactions and metabolites is at frontier of biological sciences. The recent availability of high-throughput technology data sets in biology has paved the way for new modelling approaches at various levels of complexity including the metabolome of a cell or an organism. Understanding the metabolism of a single cell and multi-cell organism will provide the knowledge for the rational design of growth conditions to produce commercially valuable reagents in biotechnology. Here, we demonstrate how equations representing steady state mass conservation, energy conservation, the second law of thermodynamics, and reversible enzyme kinetics can be formulated as a single system of linear equalities and inequalities, in addition to linear equalities on exponential variables. Even though the feasible set is non-convex, the reformulation is exact and amenable to large-scale numerical analysis, a prerequisite for computationally feasible genome scale modelling. Integrating flux, concentration and kinetic variables in a unified constraint-based formulation is aimed at increasing the quantitative predictive capacity of flux balance analysis. Incorporation of experimental and theoretical bounds on thermodynamic and kinetic variables ensures that the predicted steady state fluxes are both thermodynamically and biochemically feasible. The resulting in silico predictions are tested against fluxomic data for central metabolism in Escherichia coli and compare favourably with in silico prediction by flux balance analysis. Copyright (c) 2010 Elsevier Ltd. All rights reserved.
Numerical analysis of bifurcations
International Nuclear Information System (INIS)
Guckenheimer, J.
1996-01-01
This paper is a brief survey of numerical methods for computing bifurcations of generic families of dynamical systems. Emphasis is placed upon algorithms that reflect the structure of the underlying mathematical theory while retaining numerical efficiency. Significant improvements in the computational analysis of dynamical systems are to be expected from more reliance of geometric insight coming from dynamical systems theory. copyright 1996 American Institute of Physics
Alias, M. S.; Rafie, A. S. Mohd; Marzuki, O. F.; Hamid, M. F. Abdul; Chia, C. C.
2017-12-01
Over the years, many studies have demonstrated the feasibility of the Magnus effect on spinning cylinder to improve lift production, which can be much higher than the traditional airfoil shape. With this characteristic, spinning cylinder might be used as a lifting device for short take-off distance aircraft or unmanned aerial vehicle (UAV). Nonetheless, there is still a gap in research to explain the use of spinning cylinder as a good lifting device. Computational method is used for this study to analyse the Magnus effect, in which two-dimensional finite element numerical analysis method is applied using ANSYS FLUENT software to examine the coefficients of lift and drag, and to investigate the flow field around the rotating cylinder surface body. Cylinder size of 30mm is chosen and several configurations in steady and concentrated air flows have been evaluated. All in all, it can be concluded that, with the right configuration of the concentrated air flow setup, the rotating cylinder can be used as a lifting device for very short take-off since it can produce very high coefficient of lift (2.5 times higher) compared with steady air flow configuration.
Computation of tokamak equilibria with steady flow
International Nuclear Information System (INIS)
Kerner, W.; Tokuda, Shinji
1987-08-01
The equations for ideal MHD equilibria with stationary flow are reexamined and addressed as numerically applied to tokamak configurations with a free plasma boundary. Both the isothermal (purely toroidal flow) and the poloidal flow cases are treated. Experiment-relevant states with steady flow (so far only in the toroidal direction) are computed by the modified SELENE40 code. (author)
Robust periodic steady state analysis of autonomous oscillators based on generalized eigenvalues
Mirzavand, R.; Maten, ter E.J.W.; Beelen, T.G.J.; Schilders, W.H.A.; Abdipour, A.
2011-01-01
In this paper, we present a new gauge technique for the Newton Raphson method to solve the periodic steady state (PSS) analysis of free-running oscillators in the time domain. To find the frequency a new equation is added to the system of equations. Our equation combines a generalized eigenvector
Robust periodic steady state analysis of autonomous oscillators based on generalized eigenvalues
Mirzavand, R.; Maten, ter E.J.W.; Beelen, T.G.J.; Schilders, W.H.A.; Abdipour, A.; Michielsen, B.; Poirier, J.R.
2012-01-01
In this paper, we present a new gauge technique for the Newton Raphson method to solve the periodic steady state (PSS) analysis of free-running oscillators in the time domain. To find the frequency a new equation is added to the system of equations. Our equation combines a generalized eigenvector
International Nuclear Information System (INIS)
McKee, S.; Elliott, C.M.
1986-01-01
The applications of mathematics to industrial problems involves the formulation of problems which are amenable to mathematical investigation, mathematical modelling, the solution of the mathematical problem and the inter-pretation of the results. There are 12 chapters describing industrial problems where mathematics and numerical analysis can be applied. These range from the numerical assessment of the flatness of engineering surfaces and plates, the design of chain links, control problems in tidal power generation and low thrust satellite trajectory optimization to mathematical models in welding. One chapter, on the ageing of stainless steels, is indexed separately. (UK)
International Nuclear Information System (INIS)
Almeida, P G C; Benilov, M S; Cunha, M D; Faria, M J
2009-01-01
Bifurcations and/or their consequences are frequently encountered in numerical modelling of current transfer to cathodes of gas discharges, also in apparently simple situations, and a failure to recognize and properly analyse a bifurcation may create difficulties in the modelling and hinder the understanding of numerical results and the underlying physics. This work is concerned with analysis of bifurcations that have been encountered in the modelling of steady-state current transfer to cathodes of glow and arc discharges. All basic types of steady-state bifurcations (fold, transcritical, pitchfork) have been identified and analysed. The analysis provides explanations to many results obtained in numerical modelling. In particular, it is shown that dramatic changes in patterns of current transfer to cathodes of both glow and arc discharges, described by numerical modelling, occur through perturbed transcritical bifurcations of first- and second-order contact. The analysis elucidates the reason why the mode of glow discharge associated with the falling section of the current-voltage characteristic in the solution of von Engel and Steenbeck seems not to appear in 2D numerical modelling and the subnormal and normal modes appear instead. A similar effect has been identified in numerical modelling of arc cathodes and explained.
SUPERENERGY-2: a multiassembly, steady-state computer code for LMFBR core thermal-hydraulic analysis
Energy Technology Data Exchange (ETDEWEB)
Basehore, K.L.; Todreas, N.E.
1980-08-01
Core thermal-hydraulic design and performance analyses for Liquid Metal Fast Breeder Reactors (LMFBRs) require repeated detailed multiassembly calculations to determine radial temperature profiles and subchannel outlet temperatures for various core configurations and subassembly structural analyses. At steady-state, detailed core-wide temperature profiles are required for core restraint calculations and subassembly structural analysis. In addition, sodium outlet temperatures are routinely needed for each reactor operating cycle. The SUPERENERGY-2 thermal-hydraulic code was designed specifically to meet these designer needs. It is applicable only to steady-state, forced-convection flow in LMFBR core geometries.
SUPERENERGY-2: a multiassembly, steady-state computer code for LMFBR core thermal-hydraulic analysis
International Nuclear Information System (INIS)
Basehore, K.L.; Todreas, N.E.
1980-08-01
Core thermal-hydraulic design and performance analyses for Liquid Metal Fast Breeder Reactors (LMFBRs) require repeated detailed multiassembly calculations to determine radial temperature profiles and subchannel outlet temperatures for various core configurations and subassembly structural analyses. At steady-state, detailed core-wide temperature profiles are required for core restraint calculations and subassembly structural analysis. In addition, sodium outlet temperatures are routinely needed for each reactor operating cycle. The SUPERENERGY-2 thermal-hydraulic code was designed specifically to meet these designer needs. It is applicable only to steady-state, forced-convection flow in LMFBR core geometries
Energy Technology Data Exchange (ETDEWEB)
Luna, N. [Secretaria de Energia, Direccion de Operacion Petrolera, Mexico DF (Mexico); Mendez, F. [UNAM, Facultad de Ingenieria, Mexico DF (Mexico); Bautista, O. [ITESM, Division de Ingenieria y Arquitectura, Mexico DF (Mexico)
2005-05-01
We treat numerically in this paper, the transient analysis of a conjugated heat transfer process in the thermal entrance region of a circular tube with a fully developed laminar power-law fluid flow. We apply the quasi-steady approximation for the power-law fluid, identifying the suitable time scales of the process. Thus, the energy equation in the fluids is solved analytically using the well-known integral boundary layer technique. This solution is coupled to the transient energy equation for the solid where the transverse and longitudinal heat conduction effects are taken into account. The numerical results for the temporal evolution of the average temperature of the tube wall, {theta}{sub av,} is plotted for different nondimensional parameters such as conduction parameter, {alpha}, the aspect ratios of the tube, {epsilon} and {epsilon}{sub 0} and the index of power-law fluid, n. (orig.)
International Nuclear Information System (INIS)
Hussain, M.; Khan, J.A.
2004-01-01
A numerical study of flow in distributor of Francis Turbine is carried out by using two different techniques of flow zone generation. Distributor of GAMM Francis Turbine is used for present calculation. In present work, flow is assumed to be periodic around the distributor in steady state conditions, therefore computational domain consists of only one blade channel (one stay vane and one guide vane). The distributor computational domain is bounded up stream by cylindrical and downstream by conical patches. The first one corresponds to the spiral casing outflow section, while the second one is considered to be the distributor outlet or runner inlet. Upper and lower surfaces are generated by the revolution of hub and shroud edges. Single connected and multiple connected techniques are considered to generate distributor flow zone for numerical flow analysis of GAMM Francis turbine. The tetrahedral meshes are generated in both the flow zones. Same boundary conditions are applied for both the equivalent flow zones. The three dimensional, laminar flow analysis for both the distributor flow zones of the GAMM Francis turbine operating at the best efficiency point is performed. Gambit and G- Turbo are used as a preprocessor while calculations are done by using Fluent. Finally, numerical results obtained on the distributor outlet are compared with the available experimental data to validate the two different methodologies and examine their accuracy. (author)
Analysis of the steady state hydraulic behaviour of the ITER blanket cooling system
Energy Technology Data Exchange (ETDEWEB)
Di Maio, P.A., E-mail: pietroalessandro.dimaio@unipa.it [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Dell’Orco, G.; Furmanek, A. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Garitta, S. [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Merola, M.; Mitteau, R.; Raffray, R. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Spagnuolo, G.A.; Vallone, E. [Dipartimento di Energia, Ingegneria dell’Informazione e Modelli Matematici, Università di Palermo, Viale delle Scienze, 90128 Palermo (Italy)
2015-10-15
Highlights: • Nominal steady state hydraulic behaviour of ITER blanket standard sector cooling system has been investigated. • Numerical simulations have been run adopting a qualified thermal-hydraulic system code. • Hydraulic characteristic functions and coolant mass flow rates, velocities and pressure drops have been assessed. • Most of the considered circuits are able to effectively cool blanket modules, meeting ITER requirements. - Abstract: The blanket system is the ITER reactor component devoted to providing a physical boundary for plasma transients and contributing to thermal and nuclear shielding of vacuum vessel, magnets and external components. It is expected to be subjected to significant heat loads under nominal conditions and its cooling system has to ensure an adequate cooling, preventing any risk of critical heat flux occurrence while complying with pressure drop limits. At the University of Palermo a study has been performed, in cooperation with the ITER Organization, to investigate the steady state hydraulic behaviour of the ITER blanket standard sector cooling system. A theoretical–computational approach based on the finite volume method has been followed, adopting the RELAP5 system code. Finite volume models of the most critical blanket cooling circuits have been set-up, realistically simulating the coolant flow domain. The steady state hydraulic behaviour of each cooling circuit has been investigated, determining its hydraulic characteristic function and assessing the spatial distribution of coolant mass flow rates, velocities and pressure drops under reference nominal conditions. Results obtained have indicated that the investigated cooling circuits are able to provide an effective cooling to blanket modules, generally meeting ITER requirements in term of pressure drop and velocity distribution, except for a couple of circuits that are being revised.
Simulation of the Francis-99 Hydro Turbine During Steady and Transient Operation
Dewan, Yuvraj; Custer, Chad; Ivashchenko, Artem
2017-01-01
Numerical simulation of the Francis-99 hydroturbine with correlation to experimental measurements are presented. Steady operation of the hydroturbine is analyzed at three operating conditions: the best efficiency point (BEP), high load (HL), and part load (PL). It is shown that global quantities such as net head, discharge and efficiency are well predicted. Additionally, time-averaged velocity predictions compare well with PIV measurements obtained in the draft tube immediately downstream of the runner. Differences in vortex rope structure between operating points are discussed. Unsteady operation of the hydroturbine from BEP to HL and from BEP to PL are modeled. It is shown that simulation methods used to model the steady operation produce predictions that correlate well with experiment for transient operation. Time-domain unsteady simulation is used for both steady and unsteady operation. The full-fidelity geometry including all components is meshed using an unstructured polyhedral mesh with body-fitted prism layers. Guide vane rotation for transient operation is imposed using fully-conservative, computationally efficient mesh morphing. The commercial solver STAR-CCM+ is used for all portions of the analysis including meshing, solving and post-processing.
X-Ray Spectral Analysis of the Steady States of GRS1915+105
Peris, Charith S.; Remillard, Ronald A.; Steiner, James F.; Vrtilek, Saeqa D.; Varnière, Peggy; Rodriguez, Jerome; Pooley, Guy
2016-05-01
We report on the X-ray spectral behavior within the steady states of GRS1915+105. Our work is based on the full data set of the source obtained using the Proportional Counter Array (PCA) on the Rossi X-ray Timing Explorer (RXTE) and 15 GHz radio data obtained using the Ryle Telescope. The steady observations within the X-ray data set naturally separated into two regions in the color-color diagram and we refer to these regions as steady-soft and steady-hard. GRS1915+105 displays significant curvature in the coronal component in both the soft and hard data within the RXTE/PCA bandpass. A majority of the steady-soft observations displays a roughly constant inner disk radius ({R}{{in}}), while the steady-hard observations display an evolving disk truncation which is correlated to the mass accretion rate through the disk. The disk flux and coronal flux are strongly correlated in steady-hard observations and very weakly correlated in the steady-soft observations. Within the steady-hard observations, we observe two particular circumstances when there are correlations between the coronal X-ray flux and the radio flux with log slopes η ˜ 0.68+/- 0.35 and η ˜ 1.12+/- 0.13. They are consistent with the upper and lower tracks of Gallo et al. (2012), respectively. A comparison of the model parameters to the state definitions shows that almost all of the steady-soft observations match the criteria of either a thermal or steep power-law state, while a large portion of the steady-hard observations match the hard-state criteria when the disk fraction constraint is neglected.
Incorporation of wind generation to the Mexican power grid: Steady state analysis
Energy Technology Data Exchange (ETDEWEB)
Tovar, J.H.; Guardado, J.L.; Cisneros, F. [Inst. Tecnologico de Morelia (Mexico); Cadenas, R.; Lopez, S. [Comision Federal de Electricidad, Morelia (Mexico)
1997-09-01
This paper describes a steady state analysis related with the incorporation of large amounts of eolic generation into the Mexican power system. An equivalent node is used to represent individual eolic generators in the wind farm. Possible overloads, losses, voltage and reactive profiles and estimated severe contingencies are analyzed. Finally, the conclusions of this study are presented.
Statistical steady states in turbulent droplet condensation
Bec, Jeremie; Krstulovic, Giorgio; Siewert, Christoph
2017-11-01
We investigate the general problem of turbulent condensation. Using direct numerical simulations we show that the fluctuations of the supersaturation field offer different conditions for the growth of droplets which evolve in time due to turbulent transport and mixing. This leads to propose a Lagrangian stochastic model consisting of a set of integro-differential equations for the joint evolution of the squared radius and the supersaturation along droplet trajectories. The model has two parameters fixed by the total amount of water and the thermodynamic properties, as well as the Lagrangian integral timescale of the turbulent supersaturation. The model reproduces very well the droplet size distributions obtained from direct numerical simulations and their time evolution. A noticeable result is that, after a stage where the squared radius simply diffuses, the system converges exponentially fast to a statistical steady state independent of the initial conditions. The main mechanism involved in this convergence is a loss of memory induced by a significant number of droplets undergoing a complete evaporation before growing again. The statistical steady state is characterised by an exponential tail in the droplet mass distribution.
Numerical simulation of pulse-tube refrigerators
Lyulina, I.A.; Mattheij, R.M.M.; Tijsseling, A.S.; Waele, de A.T.A.M.
2004-01-01
A new numerical model has been introduced to study steady oscillatory heat and mass transfer in the tube section of a pulse-tube refrigerator. Conservation equations describing compressible gas flow in the tube are solved numerically, using high resolution schemes. The equation of conservation of
Efficient steady-state solver for hierarchical quantum master equations
Zhang, Hou-Dao; Qiao, Qin; Xu, Rui-Xue; Zheng, Xiao; Yan, YiJing
2017-07-01
Steady states play pivotal roles in many equilibrium and non-equilibrium open system studies. Their accurate evaluations call for exact theories with rigorous treatment of system-bath interactions. Therein, the hierarchical equations-of-motion (HEOM) formalism is a nonperturbative and non-Markovian quantum dissipation theory, which can faithfully describe the dissipative dynamics and nonlinear response of open systems. Nevertheless, solving the steady states of open quantum systems via HEOM is often a challenging task, due to the vast number of dynamical quantities involved. In this work, we propose a self-consistent iteration approach that quickly solves the HEOM steady states. We demonstrate its high efficiency with accurate and fast evaluations of low-temperature thermal equilibrium of a model Fenna-Matthews-Olson pigment-protein complex. Numerically exact evaluation of thermal equilibrium Rényi entropies and stationary emission line shapes is presented with detailed discussion.
Average-case analysis of numerical problems
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.
Veliz-Cuba, Alan; Aguilar, Boris; Hinkelmann, Franziska; Laubenbacher, Reinhard
2014-06-26
A key problem in the analysis of mathematical models of molecular networks is the determination of their steady states. The present paper addresses this problem for Boolean network models, an increasingly popular modeling paradigm for networks lacking detailed kinetic information. For small models, the problem can be solved by exhaustive enumeration of all state transitions. But for larger models this is not feasible, since the size of the phase space grows exponentially with the dimension of the network. The dimension of published models is growing to over 100, so that efficient methods for steady state determination are essential. Several methods have been proposed for large networks, some of them heuristic. While these methods represent a substantial improvement in scalability over exhaustive enumeration, the problem for large networks is still unsolved in general. This paper presents an algorithm that consists of two main parts. The first is a graph theoretic reduction of the wiring diagram of the network, while preserving all information about steady states. The second part formulates the determination of all steady states of a Boolean network as a problem of finding all solutions to a system of polynomial equations over the finite number system with two elements. This problem can be solved with existing computer algebra software. This algorithm compares favorably with several existing algorithms for steady state determination. One advantage is that it is not heuristic or reliant on sampling, but rather determines algorithmically and exactly all steady states of a Boolean network. The code for the algorithm, as well as the test suite of benchmark networks, is available upon request from the corresponding author. The algorithm presented in this paper reliably determines all steady states of sparse Boolean networks with up to 1000 nodes. The algorithm is effective at analyzing virtually all published models even those of moderate connectivity. The problem for
Stratified steady and unsteady two-phase flows between two parallel plates
International Nuclear Information System (INIS)
Sim, Woo Gun
2006-01-01
To understand fluid dynamic forces acting on a structure subjected to two-phase flow, it is essential to get detailed information about the characteristics of two-phase flow. Stratified steady and unsteady two-phase flows between two parallel plates have been studied to investigate the general characteristics of the flow related to flow-induced vibration. Based on the spectral collocation method, a numerical approach has been developed for the unsteady two-phase flow. The method is validated by comparing numerical result to analytical one given for a simple harmonic two-phase flow. The flow parameters for the steady two-phase flow, such as void fraction and two-phase frictional multiplier, are evaluated. The dynamic characteristics of the unsteady two-phase flow, including the void fraction effect on the complex unsteady pressure, are illustrated
Numerical analysis on acoustic impulse response for watermelon
International Nuclear Information System (INIS)
Kim, Yong Sul; Yang, Dong Hoon; Choi, Young Jae; Bae, Tas Joo; So, Chul Ho; Lee, Yun Ho
2002-01-01
In this study, we conducted both analysis on impact pulse signal and acoustic impulse response method using numerical analysistic finite element method. Considering its velocity, density, Young's Modulus, and Poisson's Ratio, we extracted featured parameters and compared both results of analysis on impact pulse signal and numerical analysis on acoustic impulse response then we found the feature of generated acoustic sound signal by way of numerical analysis varying featured parameters and consequently intended to extract feature indices influenced on its internal maturity through analysis of acoustic impulse response. As we analyzed impact pulse signal and extracted featured parameters concerned with evaluation of its ripeness, we found the plausibility of progress on nondestructive evaluation of ripeness and adoption of numerical analysis on acoustic impulse response.
Direct numerical simulation of electrokinetic instability and transition to chaotic motion
Demekhin, E. A.; Nikitin, N. V.; Shelistov, V. S.
2013-12-01
A new type of instability—electrokinetic instability—and an unusual transition to chaotic motion near a charge-selective surface (semiselective electric membrane, electrode, or system of micro-/nanochannels) was studied by the numerical integration of the Nernst-Planck-Poisson-Stokes system and a weakly nonlinear analysis near the threshold of instability. A special finite-difference method was used for the space discretization along with a semi-implicit 31/3-step Runge-Kutta scheme for the integration in time. Two kinds of initial conditions were considered: (a) white-noise initial conditions to mimic "room disturbances" and subsequent natural evolution of the solution, and (b) an artificial monochromatic ion distribution with a fixed wave number to simulate regular wave patterns. The results were studied from the viewpoint of hydrodynamic stability and bifurcation theory. The threshold of electroconvective movement was found by the linear spectral stability theory, the results of which were confirmed by numerical simulation of the entire system. Our weakly nonlinear analysis and numerical integration of the entire system predict possibility of both kinds of bifurcations at the critical point, supercritical and subcritical, depending on the system parameters. The following regimes, which replace each other as the potential drop between the selective surfaces increases, were obtained: one-dimensional steady solution, two-dimensional steady electroconvective vortices (stationary point in a proper phase space), unsteady vortices aperiodically changing their parameters (homoclinic contour), periodic motion (limit cycle), and chaotic motion. The transition to chaotic motion does not include Hopf bifurcation. The numerical resolution of the thin concentration polarization layer showed spike-like charge profiles along the surface, which could be, depending on the regime, either steady or aperiodically coalescent. The numerical investigation confirmed the
Direct numerical simulation of electrokinetic instability and transition to chaotic motion
International Nuclear Information System (INIS)
Demekhin, E. A.; Nikitin, N. V.; Shelistov, V. S.
2013-01-01
A new type of instability—electrokinetic instability—and an unusual transition to chaotic motion near a charge-selective surface (semiselective electric membrane, electrode, or system of micro-/nanochannels) was studied by the numerical integration of the Nernst-Planck-Poisson-Stokes system and a weakly nonlinear analysis near the threshold of instability. A special finite-difference method was used for the space discretization along with a semi-implicit 31/3 -step Runge-Kutta scheme for the integration in time. Two kinds of initial conditions were considered: (a) white-noise initial conditions to mimic “room disturbances” and subsequent natural evolution of the solution, and (b) an artificial monochromatic ion distribution with a fixed wave number to simulate regular wave patterns. The results were studied from the viewpoint of hydrodynamic stability and bifurcation theory. The threshold of electroconvective movement was found by the linear spectral stability theory, the results of which were confirmed by numerical simulation of the entire system. Our weakly nonlinear analysis and numerical integration of the entire system predict possibility of both kinds of bifurcations at the critical point, supercritical and subcritical, depending on the system parameters. The following regimes, which replace each other as the potential drop between the selective surfaces increases, were obtained: one-dimensional steady solution, two-dimensional steady electroconvective vortices (stationary point in a proper phase space), unsteady vortices aperiodically changing their parameters (homoclinic contour), periodic motion (limit cycle), and chaotic motion. The transition to chaotic motion does not include Hopf bifurcation. The numerical resolution of the thin concentration polarization layer showed spike-like charge profiles along the surface, which could be, depending on the regime, either steady or aperiodically coalescent. The numerical investigation confirmed the
Direct numerical simulation of electrokinetic instability and transition to chaotic motion
Energy Technology Data Exchange (ETDEWEB)
Demekhin, E. A., E-mail: edemekhi@gmail.com [Laboratory of Micro- and Nanofluidics, Moscow State University, Moscow 119192 (Russian Federation); Department of Computation Mathematics and Computer Science, Kuban State University, Krasnodar 350040 (Russian Federation); Institute of Mechanics, Moscow State University, Moscow 117192 (Russian Federation); Nikitin, N. V. [Institute of Mechanics, Moscow State University, Moscow 117192 (Russian Federation); Shelistov, V. S. [Institute of Mechanics, Moscow State University, Moscow 117192 (Russian Federation); Scientific Research Department, Kuban State University, Krasnodar 350040 (Russian Federation)
2013-12-15
A new type of instability—electrokinetic instability—and an unusual transition to chaotic motion near a charge-selective surface (semiselective electric membrane, electrode, or system of micro-/nanochannels) was studied by the numerical integration of the Nernst-Planck-Poisson-Stokes system and a weakly nonlinear analysis near the threshold of instability. A special finite-difference method was used for the space discretization along with a semi-implicit 31/3 -step Runge-Kutta scheme for the integration in time. Two kinds of initial conditions were considered: (a) white-noise initial conditions to mimic “room disturbances” and subsequent natural evolution of the solution, and (b) an artificial monochromatic ion distribution with a fixed wave number to simulate regular wave patterns. The results were studied from the viewpoint of hydrodynamic stability and bifurcation theory. The threshold of electroconvective movement was found by the linear spectral stability theory, the results of which were confirmed by numerical simulation of the entire system. Our weakly nonlinear analysis and numerical integration of the entire system predict possibility of both kinds of bifurcations at the critical point, supercritical and subcritical, depending on the system parameters. The following regimes, which replace each other as the potential drop between the selective surfaces increases, were obtained: one-dimensional steady solution, two-dimensional steady electroconvective vortices (stationary point in a proper phase space), unsteady vortices aperiodically changing their parameters (homoclinic contour), periodic motion (limit cycle), and chaotic motion. The transition to chaotic motion does not include Hopf bifurcation. The numerical resolution of the thin concentration polarization layer showed spike-like charge profiles along the surface, which could be, depending on the regime, either steady or aperiodically coalescent. The numerical investigation confirmed the
Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow
Tsvelodub, O. Yu; Bocharov, A. A.
2017-09-01
The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. The paper studies nonlinear waves on a liquid film, flowing under the action of gravity in a known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. The periodic and soliton steady-state traveling solutions of this equation have been numerically found. The analysis of branching of new families of steady-state traveling solutions has been performed. In particular, it is shown that this model equation has solutions in the form of solitons-humps.
International Nuclear Information System (INIS)
Yoo, Y. J.; Hwnag, T. H.; Kim, K. K.; Ji, S. K.
2001-01-01
The numerical instability at low-pressure and low-flow conditions has been confirmed to be the common problem of the existing COBRA-series subchannel analysis codes. In addition, the range of operating conditions at which the analyses by the codes are impossible has been evaluated. To evaluate the MATRA's inapplicable range of operating conditions of the SMART core that is to be operated at the low flow condition, i.e. about 30% of the flow of the existing commercial pressurized water reactors at the steady-state condition, the analyses of various operating conditions were performed by using several representative COBRA-series subchannel analysis codes including MATRA. TORC of CE, COBRA3CP of Siemens/KWU, COBRA4I of PNL, and MATRA of KAERI were chosen as the subchannel analysis codes to be evaluated. The various operating conditions used in the CHF tests carried out at the Winfrith Establishment of UKAEA were chosen as the conditions to be analyzed. As the result, the numerical instabilities at low-pressure and low-flow conditions occurred in the analyses by all of the codes. It was revealed that the MATRA code, which numerically more stable thatn the other codes, was not able to analyze the conditions of the pressure not more than 100 bar and the mass velocity not more than 300 kg/sec-m 2 . Hereafter it is required to find out the exact reason for the numerical instability of the existing COBRA-series subchannel analysis codes at low-pressure and low-flow conditions and to devise the new method to get over that numerical problem
Analysis of steady state and transient two-phase flows in downwardly inclined lines
International Nuclear Information System (INIS)
Crawford, T.J.
1983-01-01
A study of steady-state and transient two-phase flows in downwardly inclined lines is described. Steady-state flow patterns maps are presented using Freon-113 as the working fluid to provide new high density vapors. These flow maps with high density vapor serve to significantly extend the investigations of steady-state downward two-phase flow patterns. Physical models developed which successfully predicted the onset or location of various flow pattern transitions. A new simplified criterion that would be useful to designers and experimenters is offered for the onset of dispersed flow. A new empirical holdup correlation and a new bubble diameter/flow rate correlation are also proposed. Flow transients in vertical downward lines were studied to investigate the possible formation of intermediate or spurious flow patterns that would not be seen at steady-state conditions. Void fraction behavior during the transients was modeled by using the dynamic slip equation from the transient analysis code RETRAN. Physical models of interfacial area were developed and compared with models and data from literature. There was satisfactory agreement between the models of the present study and the literature models and data. The concentration parameter of the drift flux model was evaluated for vertical downward flow. These new values of the flow dependent parameter were different from those previously proposed in the literature for use in upward flows, and made the drift flux model suitable for use in upward or downward flow lines
Numerical analysis on acoustic impulse response for watermelon
Energy Technology Data Exchange (ETDEWEB)
Kim, Yong Sul; Yang, Dong Hoon; Choi, Young Jae; Bae, Tas Joo; So, Chul Ho [Dongshin University, Naju (Korea, Republic of); Lee, Yun Ho [Korea Inspection and Engineering CO.,LTD., Seoul (Korea, Republic of)
2002-11-15
In this study, we conducted both analysis on impact pulse signal and acoustic impulse response method using numerical analysistic finite element method. Considering its velocity, density, Young's Modulus, and Poisson's Ratio, we extracted featured parameters and compared both results of analysis on impact pulse signal and numerical analysis on acoustic impulse response then we found the feature of generated acoustic sound signal by way of numerical analysis varying featured parameters and consequently intended to extract feature indices influenced on its internal maturity through analysis of acoustic impulse response. As we analyzed impact pulse signal and extracted featured parameters concerned with evaluation of its ripeness, we found the plausibility of progress on nondestructive evaluation of ripeness and adoption of numerical analysis on acoustic impulse response.
A method for statistical steady state thermal analysis of reactor cores
International Nuclear Information System (INIS)
Whetton, P.A.
1981-01-01
In a previous publication the author presented a method for undertaking statistical steady state thermal analyses of reactor cores. The present paper extends the technique to an assessment of confidence limits for the resulting probability functions which define the probability that a given thermal response value will be exceeded in a reactor core. Establishing such confidence limits is considered an integral part of any statistical thermal analysis and essential if such analysis are to be considered in any regulatory process. In certain applications the use of a best estimate probability function may be justifiable but it is recognised that a demonstrably conservative probability function is required for any regulatory considerations. (orig.)
Fiedler, Anna; Raeth, Sebastian; Theis, Fabian J; Hausser, Angelika; Hasenauer, Jan
2016-08-22
Ordinary differential equation (ODE) models are widely used to describe (bio-)chemical and biological processes. To enhance the predictive power of these models, their unknown parameters are estimated from experimental data. These experimental data are mostly collected in perturbation experiments, in which the processes are pushed out of steady state by applying a stimulus. The information that the initial condition is a steady state of the unperturbed process provides valuable information, as it restricts the dynamics of the process and thereby the parameters. However, implementing steady-state constraints in the optimization often results in convergence problems. In this manuscript, we propose two new methods for solving optimization problems with steady-state constraints. The first method exploits ideas from optimization algorithms on manifolds and introduces a retraction operator, essentially reducing the dimension of the optimization problem. The second method is based on the continuous analogue of the optimization problem. This continuous analogue is an ODE whose equilibrium points are the optima of the constrained optimization problem. This equivalence enables the use of adaptive numerical methods for solving optimization problems with steady-state constraints. Both methods are tailored to the problem structure and exploit the local geometry of the steady-state manifold and its stability properties. A parameterization of the steady-state manifold is not required. The efficiency and reliability of the proposed methods is evaluated using one toy example and two applications. The first application example uses published data while the second uses a novel dataset for Raf/MEK/ERK signaling. The proposed methods demonstrated better convergence properties than state-of-the-art methods employed in systems and computational biology. Furthermore, the average computation time per converged start is significantly lower. In addition to the theoretical results, the
Numerical methods in software and analysis
Rice, John R
1992-01-01
Numerical Methods, Software, and Analysis, Second Edition introduces science and engineering students to the methods, tools, and ideas of numerical computation. Introductory courses in numerical methods face a fundamental problem-there is too little time to learn too much. This text solves that problem by using high-quality mathematical software. In fact, the objective of the text is to present scientific problem solving using standard mathematical software. This book discusses numerous programs and software packages focusing on the IMSL library (including the PROTRAN system) and ACM Algorithm
Poiseuille flow of soft glasses in narrow channels: from quiescence to steady state.
Chaudhuri, Pinaki; Horbach, Jürgen
2014-10-01
Using numerical simulations, the onset of Poiseuille flow in a confined soft glass is investigated. Starting from the quiescent state, steady flow sets in at a time scale which increases with a decrease in applied forcing. At this onset time scale, a rapid transition occurs via the simultaneous fluidization of regions having different local stresses. In the absence of steady flow at long times, creep is observed even in regions where the local stress is larger than the bulk yielding threshold. Finally, we show that the time scale to attain steady flow depends strongly on the history of the initial state.
Jacques, Ian
1987-01-01
This book is primarily intended for undergraduates in mathematics, the physical sciences and engineering. It introduces students to most of the techniques forming the core component of courses in numerical analysis. The text is divided into eight chapters which are largely self-contained. However, with a subject as intricately woven as mathematics, there is inevitably some interdependence between them. The level of difficulty varies and, although emphasis is firmly placed on the methods themselves rather than their analysis, we have not hesitated to include theoretical material when we consider it to be sufficiently interesting. However, it should be possible to omit those parts that do seem daunting while still being able to follow the worked examples and to tackle the exercises accompanying each section. Familiarity with the basic results of analysis and linear algebra is assumed since these are normally taught in first courses on mathematical methods. For reference purposes a list of theorems used in the t...
Energy Technology Data Exchange (ETDEWEB)
Sevilgen, Goekhan; Kilic, Muhsin [Uludag University, Faculty of Engineering and Architecture, Department of Mechanical Engineering, TR-16059 Bursa (Turkey)
2011-01-15
A three-dimensional steady-state numerical analysis was performed in a room heated by two-panel radiators. A virtual sitting manikin with real dimensions and physiological shape was added to the model of the room, and it was assumed that the manikin surfaces were subjected to constant temperature. Two different heat transfer coefficients for the outer wall and for the window were considered. Heat interactions between the human body surfaces and the room environment, the air flow, the temperature, the humidity, and the local heat transfer characteristics of the manikin and the room surfaces were computed numerically under different environmental conditions. Comparisons of the results are presented and discussed. The results show that energy consumption can be significantly reduced while increasing the thermal comfort by using better-insulated outer wall materials and windows. (author)
International Nuclear Information System (INIS)
Gou Junli; Qiu Suizheng; Su Guanghui; Jia Dounan
2006-01-01
This article presents a theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor. Through numerically solving the one-dimensional steady-state single-phase conservative equations for the primary circuit and the steady-state two-phase drift-flux conservative equations for the secondary side of the steam generator, the natural circulation characteristics were studied. On the basis of the preliminary calculation analysis, it was found that natural circulation mass flow rate was proportional to the exponential function of the power and that the value of the exponent is related to the operating conditions of the secondary side of the steam generator. The higher the outlet pressure of the secondary side of the steam generator, the higher the primary natural circulation mass flow rate. The larger height difference between the core center and the steam generator center is favorable for the heat removal capacity of the natural circulation. (authors)
Steady state and linear stability analysis of a supercritical water natural circulation loop
International Nuclear Information System (INIS)
Sharma, Manish; Pilkhwal, D.S.; Vijayan, P.K.; Saha, D.; Sinha, R.K.
2010-01-01
Supercritical water (SCW) has excellent heat transfer characteristics as a coolant for nuclear reactors. Besides it results in high thermal efficiency of the plant. However, the flow can experience instabilities in supercritical water reactors, as the density change is very large for the supercritical fluids. A computer code SUCLIN using supercritical water properties has been developed to carry out the steady state and linear stability analysis of a SCW natural circulation loop. The conservation equations of mass, momentum and energy have been linearized by imposing small perturbation in flow rate, enthalpy, pressure and specific volume. The equations have been solved analytically to generate the characteristic equation. The roots of the equation determine the stability of the system. The code has been qualitatively assessed with published results and has been extensively used for studying the effect of diameter, height, heater inlet temperature, pressure and local loss coefficients on steady state and stability behavior of a Supercritical Water Natural Circulation Loop (SCWNCL). The present paper describes the linear stability analysis model and the results obtained in detail.
An introduction to numerical methods and analysis
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 Solution of Compressible Steady Flows around the RAE 2822 Airfoil
Kryštůfek, P.; Kozel, K.
2014-03-01
The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil.
Numerical Solution of Compressible Steady Flows around the NACA 0012 Airfoil
Directory of Open Access Journals (Sweden)
Kozel K
2013-04-01
Full Text Available The article presents results of a numerical solution of subsonic and transonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the NACA 0012 airfoil. Authors used Runge-Kutta method to numerically solve the flows around the NACA 0012 airfoil.
Steady-state and dynamic models for particle engulfment during solidification
Tao, Yutao; Yeckel, Andrew; Derby, Jeffrey J.
2016-06-01
Steady-state and dynamic models are developed to study the physical mechanisms that determine the pushing or engulfment of a solid particle at a moving solid-liquid interface. The mathematical model formulation rigorously accounts for energy and momentum conservation, while faithfully representing the interfacial phenomena affecting solidification phase change and particle motion. A numerical solution approach is developed using the Galerkin finite element method and elliptic mesh generation in an arbitrary Lagrangian-Eulerian implementation, thus allowing for a rigorous representation of forces and dynamics previously inaccessible by approaches using analytical approximations. We demonstrate that this model accurately computes the solidification interface shape while simultaneously resolving thin fluid layers around the particle that arise from premelting during particle engulfment. We reinterpret the significance of premelting via the definition an unambiguous critical velocity for engulfment from steady-state analysis and bifurcation theory. We also explore the complicated transient behaviors that underlie the steady states of this system and posit the significance of dynamical behavior on engulfment events for many systems. We critically examine the onset of engulfment by comparing our computational predictions to those obtained using the analytical model of Rempel and Worster [29]. We assert that, while the accurate calculation of van der Waals repulsive forces remains an open issue, the computational model developed here provides a clear benefit over prior models for computing particle drag forces and other phenomena needed for the faithful simulation of particle engulfment.
International Nuclear Information System (INIS)
Chiem, Kok Siong; Zhao Yong
2004-01-01
In this study, a high-resolution characteristic-based finite-volume (FV) method on unstructured grids [Int. J. Numer. Method Eng. 50 (2001) 11; Int. J. Heat Fluid Flow 21 (2000) 432] is extended by a matrix-free implicit dual-time stepping scheme for the numerical simulation of steady and unsteady flow and heat transfer with porous media. The method has been used to study the characteristics of a complex problem: flow and heat transfer in a channel with multiple discrete porous blocks, which was originally proposed by Huang and Vafai [J. Thermophys. Heat Transfer 8 (3) (1994) 563]. In addition, flow and heat transfer in a channel partially or fully filled with porous layers and containing solid protruding blocks with constant heat flux on its lower surface are also investigated in details. Hydrodynamic and heat transfer results are reported for both steady and transient flow cases. In particular, the effects of Darcy and Reynolds numbers on heat transfer augmentation and pressure loss are studied. An in-depth discussion of the formation and variation of recirculation is presented and the existence of optimum porous insert is demonstrated. At high Reynolds numbers the flow in the porous channel exhibits a cyclic characteristics although unlike the non-porous channel flow, the cyclic vortex development is only restricted to a small area behind the last solid block, while temperature changes more slowly and does not exhibit cyclic variations over a long period of time. It is shown that for all the cases studied altering some parametric values can have significant and interesting effects on both flow pattern as well as heat transfer characteristics
Numerical Solution of Compressible Steady Flows around the RAE 2822 Airfoil
Directory of Open Access Journals (Sweden)
Kryštůfek P.
2014-03-01
Full Text Available The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Navier-Stokes equations in 2D laminar compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil.
Henderson, Michael
1997-08-01
The Numerical Analysis Objects project (NAO) is a project in the Mathematics Department of IBM's TJ Watson Research Center. While there are plenty of numerical tools available today, it is not an easy task to combine them into a custom application. NAO is directed at the dual problems of building applications from a set of tools, and creating those tools. There are several "reuse" projects, which focus on the problems of identifying and cataloging tools. NAO is directed at the specific context of scientific computing. Because the type of tools is restricted, problems such as tools with incompatible data structures for input and output, and dissimilar interfaces to tools which solve similar problems can be addressed. The approach we've taken is to define interfaces to those objects used in numerical analysis, such as geometries, functions and operators, and to start collecting (and building) a set of tools which use these interfaces. We have written a class library (a set of abstract classes and implementations) in C++ which demonstrates the approach. Besides the classes, the class library includes "stub" routines which allow the library to be used from C or Fortran, and an interface to a Visual Programming Language. The library has been used to build a simulator for petroleum reservoirs, using a set of tools for discretizing nonlinear differential equations that we have written, and includes "wrapped" versions of packages from the Netlib repository. Documentation can be found on the Web at "http://www.research.ibm.com/nao". I will describe the objects and their interfaces, and give examples ranging from mesh generation to solving differential equations.
Molecular control of steady-state dendritic cell maturation and immune homeostasis.
Hammer, Gianna Elena; Ma, Averil
2013-01-01
Dendritic cells (DCs) are specialized sentinels responsible for coordinating adaptive immunity. This function is dependent upon coupled sensitivity to environmental signs of inflammation and infection to cellular maturation-the programmed alteration of DC phenotype and function to enhance immune cell activation. Although DCs are thus well equipped to respond to pathogens, maturation triggers are not unique to infection. Given that immune cells are exquisitely sensitive to the biological functions of DCs, we now appreciate that multiple layers of suppression are required to restrict the environmental sensitivity, cellular maturation, and even life span of DCs to prevent aberrant immune activation during the steady state. At the same time, steady-state DCs are not quiescent but rather perform key functions that support homeostasis of numerous cell types. Here we review these functions and molecular mechanisms of suppression that control steady-state DC maturation. Corruption of these steady-state operatives has diverse immunological consequences and pinpoints DCs as potent drivers of autoimmune and inflammatory disease.
DEFF Research Database (Denmark)
Kwok, Kawai; Boccaccini, Dino; Persson, Åsa Helen
2016-01-01
The effective steady-state creep response of porous metals is studied by numerical homogenization and analytical modeling in this paper. The numerical homogenization is based on finite element models of three-dimensional microstructures directly reconstructed from tomographic images. The effects ...... model, and closely matched by the Gibson-Ashby compression and the Ramakrishnan-Arunchalam creep models. [All rights reserved Elsevier]....
Numerical Analysis of Partial Differential Equations
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 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
Highlights: • A dynamic model is developed for transient analysis of the straight-channel PCHE. • Transient scenarios of the straight-channel PCHE subject to helium temperature and mass flow rate variations are numerically investigated. • Steady-state temperature distribution inside the straight-channel PCHE is obtained in calculation. • Experiments are conducted to study the dynamic behavior of the straight-channel PCHE. - Abstract: Printed circuit heat exchangers (PCHEs) are promising to be employed in very-high-temperature gas-cooled reactors (VHTRs) due to their high robustness for high-temperature, high-pressure applications and high compactness. PCHEs typically serve as intermediate heat exchangers (IHXs) that isolate the secondary loop from the reactor’s primary system and hence must be sufficiently robust to maintain the system integrity during normal and off-normal conditions. In addition, the performance of the PCHE-type IHX could considerably affect the nuclear power plant overall operation since any transients on the secondary side would be propagated back to the reactor’s primary coolant system via the IHX. It is therefore imperative to understand how the PCHE would dynamically respond to a variety of transients. In the current study, experiments were first conducted to examine the steady-state thermal performance of a reduced-scale straight-channel PCHE. A dynamic model benchmarked in a previous study was then used to predict the steady-state and transient behavior of the PCHE. The steady-state temperature profiles of the working fluids on both the hot and cold sides and in the solid plates of the heat exchanger were obtained, which served as the initial condition for the transient simulations. The detailed dynamic response of the straight-channel PCHE, subject to inlet temperature variations, helium mass flow variations, and combinations of the two, was simulated and analyzed. In addition, two sets of transient tests, one for helium inlet
Theory and applications of numerical analysis
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
Steady State Analysis of Stochastic Systems with Multiple Time Delays
Xu, W.; Sun, C. Y.; Zhang, H. Q.
In this paper, attention is focused on the steady state analysis of a class of nonlinear dynamic systems with multi-delayed feedbacks driven by multiplicative correlated Gaussian white noises. The Fokker-Planck equations for delayed variables are at first derived by Novikov's theorem. Then, under small delay assumption, the approximate stationary solutions are obtained by the probability density approach. As a special case, the effects of multidelay feedbacks and the correlated additive and multiplicative Gaussian white noises on the response of a bistable system are considered. It is shown that the obtained analytical results are in good agreement with experimental results in Monte Carlo simulations.
Optimal control of transitions between nonequilibrium steady states.
Directory of Open Access Journals (Sweden)
Patrick R Zulkowski
Full Text Available Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines.
Comparison of Models for the Steady-State Analysis of Tilting-Pad Thrust Bearings
DEFF Research Database (Denmark)
Heinrichson, Niels; Santos, Ilmar
2005-01-01
Prediction of the minimum oil film thickness and the maximum temperature on the surface of the bearing pad is crucial in the design and dimensioning of bearings. Friction loss, oil bath temperature and pad deflection are other parameters of interest. Depending on the desired information a numerical...... for the groove between pads and the oil bath temperature from energy equilibrium for the entire bearing. The main theoretical contribution of this paper is the elaboration and comparison of 7 different mathematical models of increasing complexity. The results are compared to experimental data for steady......-state operation of a 228 mm outer diameter bearing. It is found that for the given bearing a two dimensional model is sufficient to estimate the minimum oil film thickness and the maximum temperature on the pad surface. Three dimensional modelling does not improve the quality of the results....
Characteristics of steady vibration in a rotating hub-beam system
Zhao, Zhen; Liu, Caishan; Ma, Wei
2016-02-01
A rotating beam features a puzzling character in which its frequencies and modal shapes may vary with the hub's inertia and its rotating speed. To highlight the essential nature behind the vibration phenomena, we analyze the steady vibration of a rotating Euler-Bernoulli beam with a quasi-steady-state stretch. Newton's law is used to derive the equations governing the beam's elastic motion and the hub's rotation. A combination of these equations results in a nonlinear partial differential equation (PDE) that fully reflects the mutual interaction between the two kinds of motion. Via the Fourier series expansion within a finite interval of time, we reduce the PDE into an infinite system of a nonlinear ordinary differential equation (ODE) in spatial domain. We further nondimensionalize the ODE and discretize it via a difference method. The frequencies and modal shapes of a general rotating beam are then determined numerically. For a low-speed beam where the ignorance of geometric stiffening is feasible, the beam's vibration characteristics are solved analytically. We validate our numerical method and the analytical solutions by comparing with either the past experiments or the past numerical findings reported in existing literature. Finally, systematic simulations are performed to demonstrate how the beam's eigenfrequencies vary with the hub's inertia and rotating speed.
Isaacson, Eugene
1994-01-01
This excellent text for advanced undergraduates and graduate students covers norms, numerical solution of linear systems and matrix factoring, iterative solutions of nonlinear equations, eigenvalues and eigenvectors, polynomial approximation, and other topics. It offers a careful analysis and stresses techniques for developing new methods, plus many examples and problems. 1966 edition.
Sensitivity analysis of numerical solutions for environmental fluid problems
International Nuclear Information System (INIS)
Tanaka, Nobuatsu; Motoyama, Yasunori
2003-01-01
In this study, we present a new numerical method to quantitatively analyze the error of numerical solutions by using the sensitivity analysis. If a reference case of typical parameters is one calculated with the method, no additional calculation is required to estimate the results of the other numerical parameters such as more detailed solutions. Furthermore, we can estimate the strict solution from the sensitivity analysis results and can quantitatively evaluate the reliability of the numerical solution by calculating the numerical error. (author)
Breden, Maxime; Castelli, Roberto
2018-05-01
In this paper, we present and apply a computer-assisted method to study steady states of a triangular cross-diffusion system. Our approach consist in an a posteriori validation procedure, that is based on using a fixed point argument around a numerically computed solution, in the spirit of the Newton-Kantorovich theorem. It allows to prove the existence of various non homogeneous steady states for different parameter values. In some situations, we obtain as many as 13 coexisting steady states. We also apply the a posteriori validation procedure to study the linear stability of the obtained steady states, proving that many of them are in fact unstable.
Erpelding, Marion; Sinha, Santanu; Tallakstad, Ken Tore; Hansen, Alex; Flekkøy, Eirik Grude; Måløy, Knut Jørgen
2013-11-01
It is well known that the transient behavior during drainage or imbibition in multiphase flow in porous media strongly depends on the history and initial condition of the system. However, when the steady-state regime is reached and both drainage and imbibition take place at the pore level, the influence of the evolution history and initial preparation is an open question. Here, we present an extensive experimental and numerical work investigating the history dependence of simultaneous steady-state two-phase flow through porous media. Our experimental system consists of a Hele-Shaw cell filled with glass beads which we model numerically by a network of disordered pores transporting two immiscible fluids. From measurements of global pressure evolution, histograms of saturation, and cluster-size distributions, we find that when both phases are flowing through the porous medium, the steady state does not depend on the initial preparation of the system or on the way it has been reached.
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.
Acoustic metacages for sound shielding with steady air flow
Shen, Chen; Xie, Yangbo; Li, Junfei; Cummer, Steven A.; Jing, Yun
2018-03-01
Conventional sound shielding structures typically prevent fluid transport between the exterior and interior. A design of a two-dimensional acoustic metacage with subwavelength thickness which can shield acoustic waves from all directions while allowing steady fluid flow is presented in this paper. The structure is designed based on acoustic gradient-index metasurfaces composed of open channels and shunted Helmholtz resonators. In-plane sound at an arbitrary angle of incidence is reflected due to the strong parallel momentum on the metacage surface, which leads to low sound transmission through the metacage. The performance of the proposed metacage is verified by numerical simulations and measurements on a three-dimensional printed prototype. The acoustic metacage has potential applications in sound insulation where steady fluid flow is necessary or advantageous.
The quasi-steady state of the valley wind system
Directory of Open Access Journals (Sweden)
Juerg eSchmidli
2015-12-01
Full Text Available The quasi-steady-state limit of the diurnal valley wind system is investigated overidealized three-dimensional topography. Although this limit is rarely attained inreality due to ever-changing forcings, the investigation of this limit canprovide valuable insight, in particular on the mass and heat fluxes associatedwith the along-valley wind. We derive a scaling relation for the quasi-steady-state along-valleymass flux as a function of valley geometry, valley size, atmospheric stratification,and surface sensible heat flux forcing. The scaling relation is tested by comparisonwith the mass flux diagnosed from numerical simulations of the valleywind system. Good agreement is found. The results also provide insight into the relationbetween surface friction and the strength of the along-valley pressure gradient.
Matlab programming for numerical analysis
Lopez, Cesar
2014-01-01
MATLAB is a high-level language and environment for numerical computation, visualization, and programming. Using MATLAB, you can analyze data, develop algorithms, and create models and applications. The language, tools, and built-in math functions enable you to explore multiple approaches and reach a solution faster than with spreadsheets or traditional programming languages, such as C/C++ or Java. Programming MATLAB for Numerical Analysis introduces you to the MATLAB language with practical hands-on instructions and results, allowing you to quickly achieve your goals. You will first become
Air sparging for subsurface remediation: Numerical analysis using T2VOC
Energy Technology Data Exchange (ETDEWEB)
McCray, J.E.; Falta, R.W. [Clemson Univ. SC (United States)
1995-03-01
Air sparging is under active investigation as a promising remediation technology for aquifers contaminated with folatile organic dense nonaqueous phase liquids (DNAPLs). A theoretical study for the removal of DNAPLs from the subsurface using this technology is presented. T2VOC is used to conduct multiphase numerical simulations of DNAPL removal utilizing a model aquifer with a radially-symmetric geometry. Both homogeneous and macroscale heterogeneous systems are considered. These simulations suggest that DNAPLs are efficiently removed in a zone of contaminant cleanup at relatively low gas saturations within the injected air plume. The zone of effective removal may be referred to as the radius of influence (ROI). The sparging-induced pressure increase below the water table, which may be measured in the field, is recommended as the best method for determining the ROI. Multiphase numerical simulations are used to support this recommendation, to relate the injected gas ROI to the zone of NAPL cleanup, and to illustrate the transient and steady-state aquifer behavior.
Exploration of one-dimensional plasma current density profile for K-DEMO steady-state operation
Energy Technology Data Exchange (ETDEWEB)
Kang, J.S. [Seoul National University, Seoul 151-742 (Korea, Republic of); Jung, L. [National Fusion Research Institute, Daejeon (Korea, Republic of); Byun, C.-S.; Na, D.H.; Na, Y.-S. [Seoul National University, Seoul 151-742 (Korea, Republic of); Hwang, Y.S., E-mail: yhwang@snu.ac.kr [Seoul National University, Seoul 151-742 (Korea, Republic of)
2016-11-01
Highlights: • One-dimensional current density and its optimization for the K-DEMO are explored. • Plasma current density profile is calculated with an integrated simulation code. • The impact of self and external heating profiles is considered self-consistently. • Current density is identified as a reference profile by minimizing heating power. - Abstract: Concept study for Korean demonstration fusion reactor (K-DEMO) is in progress, and basic design parameters are proposed by targeting high magnetic field operation with ITER-sized machine. High magnetic field operation is a favorable approach to enlarge relative plasma performance without increasing normalized beta or plasma current. Exploration of one-dimensional current density profile and its optimization process for the K-DEMO steady-state operation are reported in this paper. Numerical analysis is conducted with an integrated plasma simulation code package incorporating a transport code with equilibrium and current drive modules. Operation regimes are addressed with zero-dimensional system analysis. One-dimensional plasma current density profile is calculated based on equilibrium, bootstrap current analysis, and thermal transport analysis. The impact of self and external heating profiles on those parameters is considered self-consistently, where thermal power balance and 100% non-inductive current drive are the main constraints during the whole exploration procedure. Current and pressure profiles are identified as a reference steady-state profile by minimizing the external heating power with desired fusion power.
Transient and Steady-State Analysis of Nonlinear RF and Microwave Circuits
Directory of Open Access Journals (Sweden)
Zhu Lei(Lana
2006-01-01
Full Text Available This paper offers a review of simulation methods currently available for the transient and steady-state analysis of nonlinear RF and microwave circuits. The most general method continues to be the time-marching approach used in Spice, but more recent methods based on multiple time dimensions are particularly effective for RF and microwave circuits. We derive nodal formulations for the most widely used multiple time dimension methods. We put special emphasis on methods for the analysis of oscillators based in the warped multitime partial differential equations (WaMPDE approach. Case studies of a Colpitts oscillator and a voltage controlled Clapp-Gouriet oscillator are presented and discussed. The accuracy of the amplitude and phase of these methods is investigated. It is shown that the exploitation of frequency-domain latency reduces the computational effort.
Structure of a steady drain-hole vortex in a viscous fluid
DEFF Research Database (Denmark)
Bøhling, Lasse; Andersen, Anders Peter; Fabre, D.
2010-01-01
We use direct numerical simulations to study a steady bathtub vortex in a cylindrical tank with a central drain-hole, a fiat stress-free surface and velocity prescribed at the inlet. We find that the qualitative structure of the meridional flow does not depend on the radial Reynolds number, where...
Steady State Crack Propagation in Layered Material Systems Displaying Visco-plastic Behaviour
DEFF Research Database (Denmark)
Nielsen, Kim Lau
2012-01-01
The steady state fracture toughness of elastic visco-plastic materials is studied numerically, using both a conventional and a higher order model. Focus is on the combined effect of strain hardening, strain gradient hardening and strain rate hardening on cracking in layered material systems...
Trade-offs between forest carbon stocks and harvests in a steady state - A multi-criteria analysis.
Pingoud, Kim; Ekholm, Tommi; Sievänen, Risto; Huuskonen, Saija; Hynynen, Jari
2018-03-15
This paper provides a perspective for comparing trade-offs between harvested wood flows and forest carbon stocks with different forest management regimes. A constant management regime applied to a forest area with an even age-class distribution leads to a steady state, in which the annual harvest and carbon stocks remain constant over time. As both are desirable - carbon stocks for mitigating climate change and harvests for the economic use of wood and displacing fossil fuels - an ideal strategy should be chosen from a set of management regimes that are Pareto-optimal in the sense of multi-criteria decision-making. When choosing between Pareto-optimal alternatives, the trade-off between carbon stock and harvests is unavoidable. This trade-off can be described e.g. in terms of carbon payback times or carbon returns. As numerical examples, we present steady-state harvest levels and carbon stocks in a Finnish boreal forest region for different rotation periods, thinning intensities and collection patterns for harvest residues. In the set of simulated management practices, harvest residue collection presents the most favorable trade-off with payback times around 30-40 years; while Pareto-optimal changes in rotation or thinnings exhibited payback times over 100 years, or alternatively carbon returns below 1%. By extending the rotation period and using less-intensive thinnings compared to current practices, the steady-state carbon stocks could be increased by half while maintaining current harvest levels. Additional cases with longer rotation periods should be also considered, but were here excluded due to the lack of reliable data on older forest stands. Copyright © 2018 Elsevier Ltd. All rights reserved.
Nonlinear dynamics and numerical uncertainties in CFD
Yee, H. C.; Sweby, P. K.
1996-01-01
The application of nonlinear dynamics to improve the understanding of numerical uncertainties in computational fluid dynamics (CFD) is reviewed. Elementary examples in the use of dynamics to explain the nonlinear phenomena and spurious behavior that occur in numerics are given. The role of dynamics in the understanding of long time behavior of numerical integrations and the nonlinear stability, convergence, and reliability of using time-marching, approaches for obtaining steady-state numerical solutions in CFD is explained. The study is complemented with spurious behavior observed in CFD computations.
Kitazumi, Yuki; Hamamoto, Katsumi; Noda, Tatsuo; Shirai, Osamu; Kano, Kenji
2015-01-01
The fabrication of ultrathin-ring electrodes with a diameter of 2 mm and a thickness of 100 nm is established. The ultrathin-ring electrodes provide a large density of pseudo-steady-state currents, and realize pseudo-steady-state amperometry under quiescent conditions without a Faraday cage. Under the limiting current conditions, the current response at the ultrathin-ring electrode can be well explained by the theory of the microband electrode response. Cyclic voltammograms at the ultrathin-ring electrode show sigmoidal characteristics with some hysteresis. Numerical simulation reveals that the hysteresis can be ascribed to the time-dependence of pseudo-steady-state current. The performance of amperometry with the ultrathin-ring electrode has been verified in its application to redox enzyme kinetic measurements.
Two-group numerical analysis of one dimensional table nuclear reactor
International Nuclear Information System (INIS)
Osusky, F.; Vrban, B.; Cerba, S.; Lueley, J.; Hascik, J.
2014-01-01
Due to the complexity of Boltzmann transport equation, for the computational modelling there is a need to simplify operators in the equation. One well known approximation is diffusion theory, which is often used for numerical calculations. This approximation describes the migration of neutrons in space. It also eliminates few challenging variables, such as neutrons angular distribution and in our case energy variability (only two energy groups of neutrons are considered). This simplification has also its limitations and the diffusion theory is applicable in the environment without large local absorbers. The limitations are: environment is homogeneous, steady state type of analysis (∂φ/∂t = 0), neutron scattering is isotropic. The influence of heterogeneousness is decreasing with larger migration area of neutrons and therefore. Diffusion theory is very suitable for fast calculations and it is used during development of theoretical reactor design. The successful application of program code was demonstrated. It has also its limitations but it provides relevant information when these limitations are taken into account by researcher. Development of such program codes helps to increase knowledge level and it directly influences nuclear safety. It also allows solving specific issues which are irresolvable by commercial codes. In the future, we have a plan to enlarge geometry into 2 dimensions. (authors)
Research in applied mathematics, numerical analysis, and computer science
1984-01-01
Research conducted at the Institute for Computer Applications in Science and Engineering (ICASE) in applied mathematics, numerical analysis, and computer science is summarized and abstracts of published reports are presented. The major categories of the ICASE research program are: (1) numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; (2) control and parameter identification; (3) computational problems in engineering and the physical sciences, particularly fluid dynamics, acoustics, and structural analysis; and (4) computer systems and software, especially vector and parallel computers.
Steady state magnetic field configurations for the earth's magnetotail
Hau, L.-N.; Wolf, R. A.; Voigt, G.-H.; Wu, C. C.
1989-01-01
A two-dimensional, force-balance magnetic field model is presented. The theoretical existence of a steady state magnetic field configuration that is force-balanced and consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD is demonstrated. A numerical solution is obtained for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The results are consistent with the convection time sequences reported by Erickson (1985).
Discretizations in isogeometric analysis of Navier-Stokes flow
DEFF Research Database (Denmark)
Nielsen, Peter Nørtoft; Gersborg, Allan Roulund; Gravesen, Jens
2011-01-01
This paper deals with isogeometric analysis of 2-dimensional, steady state, incompressible Navier-Stokes flow subjected to Dirichlet boundary conditions. We present a detailed description of the numerical method used to solve the boundary value problem. Numerical inf-sup stability tests...
NASA Lewis Steady-State Heat Pipe Code Architecture
Mi, Ye; Tower, Leonard K.
2013-01-01
NASA Glenn Research Center (GRC) has developed the LERCHP code. The PC-based LERCHP code can be used to predict the steady-state performance of heat pipes, including the determination of operating temperature and operating limits which might be encountered under specified conditions. The code contains a vapor flow algorithm which incorporates vapor compressibility and axially varying heat input. For the liquid flow in the wick, Darcy s formula is employed. Thermal boundary conditions and geometric structures can be defined through an interactive input interface. A variety of fluid and material options as well as user defined options can be chosen for the working fluid, wick, and pipe materials. This report documents the current effort at GRC to update the LERCHP code for operating in a Microsoft Windows (Microsoft Corporation) environment. A detailed analysis of the model is presented. The programming architecture for the numerical calculations is explained and flowcharts of the key subroutines are given
International Nuclear Information System (INIS)
Dogan, M.; Sivrioglu, Mecit; Yılmaz, Onder
2014-01-01
Highlights: • Optimum fin shape is determined for natural convection and radiation heat transfer. • Fin array with the optimum shape has a much greater average heat transfer coefficient. • The most important factors affecting the heat transfer coefficient are determined. - Abstract: Steady state natural convection and radiation heat transfer from various shaped thin fin-arrays on a horizontal base plate has been numerically investigated. A conjugate analysis has been carried out in which the conservation equations of mass, momentum and energy for the fluid in the two fin enclosure are solved together with the heat conduction equation in the fin and the base plate. Heat transfer by radiation is also considered in analysis. The heat transfer coefficient has been determined for each of the fin array considered in the present study at the same base and the same total area. The results of the analysis show that there are some important geometrical factors affecting the design of fin arrays. Taking into consideration these factors, an optimum fin shape that yields the highest average heat transfer coefficient has been determined
International Nuclear Information System (INIS)
Shuchi, S.; Shimada, K.; Kamiyama, S.; Yamaguchi, H.
2002-01-01
We clarify numerically the wall friction coefficient, the distributions of velocity and shear rate, and the number of aggregated particles on steady magnetic fluid flow in a straight tube by taking into account the non-uniform distribution of mass concentration (DMC). Also the effect of DMC is clarified under the uniform and non-uniform transverse steady magnetic field. In comparison with the published data, the numerical results show good agreement with the experimental data
Advanced numerical methods for three dimensional two-phase flow calculations
Energy Technology Data Exchange (ETDEWEB)
Toumi, I. [Laboratoire d`Etudes Thermiques des Reacteurs, Gif sur Yvette (France); Caruge, D. [Institut de Protection et de Surete Nucleaire, Fontenay aux Roses (France)
1997-07-01
This paper is devoted to new numerical methods developed for both one and three dimensional two-phase flow calculations. These methods are finite volume numerical methods and are based on the use of Approximate Riemann Solvers concepts to define convective fluxes versus mean cell quantities. The first part of the paper presents the numerical method for a one dimensional hyperbolic two-fluid model including differential terms as added mass and interface pressure. This numerical solution scheme makes use of the Riemann problem solution to define backward and forward differencing to approximate spatial derivatives. The construction of this approximate Riemann solver uses an extension of Roe`s method that has been successfully used to solve gas dynamic equations. As far as the two-fluid model is hyperbolic, this numerical method seems very efficient for the numerical solution of two-phase flow problems. The scheme was applied both to shock tube problems and to standard tests for two-fluid computer codes. The second part describes the numerical method in the three dimensional case. The authors discuss also some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. Such a scheme is not implemented in a thermal-hydraulic computer code devoted to 3-D steady-state and transient computations. Some results obtained for Pressurised Water Reactors concerning upper plenum calculations and a steady state flow in the core with rod bow effect evaluation are presented. In practice these new numerical methods have proved to be stable on non staggered grids and capable of generating accurate non oscillating solutions for two-phase flow calculations.
Advanced numerical methods for three dimensional two-phase flow calculations
International Nuclear Information System (INIS)
Toumi, I.; Caruge, D.
1997-01-01
This paper is devoted to new numerical methods developed for both one and three dimensional two-phase flow calculations. These methods are finite volume numerical methods and are based on the use of Approximate Riemann Solvers concepts to define convective fluxes versus mean cell quantities. The first part of the paper presents the numerical method for a one dimensional hyperbolic two-fluid model including differential terms as added mass and interface pressure. This numerical solution scheme makes use of the Riemann problem solution to define backward and forward differencing to approximate spatial derivatives. The construction of this approximate Riemann solver uses an extension of Roe's method that has been successfully used to solve gas dynamic equations. As far as the two-fluid model is hyperbolic, this numerical method seems very efficient for the numerical solution of two-phase flow problems. The scheme was applied both to shock tube problems and to standard tests for two-fluid computer codes. The second part describes the numerical method in the three dimensional case. The authors discuss also some improvements performed to obtain a fully implicit solution method that provides fast running steady state calculations. Such a scheme is not implemented in a thermal-hydraulic computer code devoted to 3-D steady-state and transient computations. Some results obtained for Pressurised Water Reactors concerning upper plenum calculations and a steady state flow in the core with rod bow effect evaluation are presented. In practice these new numerical methods have proved to be stable on non staggered grids and capable of generating accurate non oscillating solutions for two-phase flow calculations
Numerical Solution of Inviscid Compressible Steady Flows around the RAE 2822 Airfoil
Kryštůfek, P.; Kozel, K.
2015-05-01
The article presents results of a numerical solution of subsonic, transonic and supersonic flows described by the system of Euler equations in 2D compressible flows around the RAE 2822 airfoil. Authors used FVM multistage Runge-Kutta method to numerically solve the flows around the RAE 2822 airfoil. The results are compared with the solution using the software Ansys Fluent 15.0.7.
2012-09-03
27] introduced a new smoothness indicator, which removed the slight post- shock oscillations and improved the convergence . A Newton- iteration method... Gauss - Seidel algorithm for steady Euler equation on unstructured grids, Numer. Math. Theor. Meth. Appl., Vol. 1, pp. 92–112, (2008). [14] G.-S. Jiang...was adopted to solve the steady two dimensional Euler equations [10, 11, 13]. The matrix-free Squared Preconditioning is applied to a Newton iteration
Numerical methods and analysis of multiscale problems
Madureira, Alexandre L
2017-01-01
This book is about numerical modeling of multiscale problems, and introduces several asymptotic analysis and numerical techniques which are necessary for a proper approximation of equations that depend on different physical scales. Aimed at advanced undergraduate and graduate students in mathematics, engineering and physics – or researchers seeking a no-nonsense approach –, it discusses examples in their simplest possible settings, removing mathematical hurdles that might hinder a clear understanding of the methods. The problems considered are given by singular perturbed reaction advection diffusion equations in one and two-dimensional domains, partial differential equations in domains with rough boundaries, and equations with oscillatory coefficients. This work shows how asymptotic analysis can be used to develop and analyze models and numerical methods that are robust and work well for a wide range of parameters.
Majeed, Muhammad Usman
2017-07-19
Steady-state elliptic partial differential equations (PDEs) are frequently used to model a diverse range of physical phenomena. The source and boundary data estimation problems for such PDE systems are of prime interest in various engineering disciplines including biomedical engineering, mechanics of materials and earth sciences. Almost all existing solution strategies for such problems can be broadly classified as optimization-based techniques, which are computationally heavy especially when the problems are formulated on higher dimensional space domains. However, in this dissertation, feedback based state estimation algorithms, known as state observers, are developed to solve such steady-state problems using one of the space variables as time-like. In this regard, first, an iterative observer algorithm is developed that sweeps over regular-shaped domains and solves boundary estimation problems for steady-state Laplace equation. It is well-known that source and boundary estimation problems for the elliptic PDEs are highly sensitive to noise in the data. For this, an optimal iterative observer algorithm, which is a robust counterpart of the iterative observer, is presented to tackle the ill-posedness due to noise. The iterative observer algorithm and the optimal iterative algorithm are then used to solve source localization and estimation problems for Poisson equation for noise-free and noisy data cases respectively. Next, a divide and conquer approach is developed for three-dimensional domains with two congruent parallel surfaces to solve the boundary and the source data estimation problems for the steady-state Laplace and Poisson kind of systems respectively. Theoretical results are shown using a functional analysis framework, and consistent numerical simulation results are presented for several test cases using finite difference discretization schemes.
International Nuclear Information System (INIS)
Witkowski, W.R.; Eldred, M.S.; Harding, D.C.
1994-01-01
The use of state-of-the-art numerical analysis tools to determine the optimal design of a radioactive material (RAM) transportation container is investigated. The design of a RAM package's components involves a complex coupling of structural, thermal, and radioactive shielding analyses. The final design must adhere to very strict design constraints. The current technique used by cask designers is uncoupled and involves designing each component separately with respect to its driving constraint. With the use of numerical optimization schemes, the complex couplings can be considered directly, and the performance of the integrated package can be maximized with respect to the analysis conditions. This can lead to more efficient package designs. Thermal and structural accident conditions are analyzed in the shape optimization of a simplified cask design. In this paper, details of the integration of numerical analysis tools, development of a process model, nonsmoothness difficulties with the optimization of the cask, and preliminary results are discussed
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 analysis of electromagnetic fields
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 ...
International Nuclear Information System (INIS)
Tagliafico, Luca A.; Scarpa, Federico; Valsuani, Federico
2014-01-01
Traditional thermal solar panel technologies have limited efficiency and the required economic investments make them noncompetitive in the space heating market. The greatest limit to the diffusion of thermal solar systems is the characteristic temperatures they can reach: the strong connection between the user temperature and the collector temperature makes it possible to achieve high thermal (collector) efficiency only at low, often useless, user temperatures. By using solar collectors as thermal exchange units (evaporators) in a heat pump system (direct expansion solar assisted heat pump, DX-SAHP), the overall efficiency greatly increases with a significative cut of the associated investment in terms of pay-back time. In this study, an approach is proposed to the steady state analysis of DX-SAHP, which is based on the simplified inverse Carnot cycle and on the second law efficiency concept. This method, without the need of calculating the refrigerant fluid properties and the detailed processes occurring in the refrigeration device, allows us to link the main features of the plant to its relevant interactions with the surroundings. The very nature of the proposed method makes the relationship explicit and meaningful among all the involved variables. The paper, after the description of the method, presents an explanatory application of this technique by reviewing various aspects of the performance of a typical DX-SAHP in which the savings on primary energy consumption is regarded as the main feature of the plant and highlighted in a monthly averaged analysis. Results agree to those coming from a common standard steady state thermodynamic analysis. The application to a typical DX-SAHP system demonstrates that a mean saved primary energy of about 50% with respect to standard gas burner can be achieved for the same user needs. Such a result is almost independent from the type of flat plate solar panel used (double or single glazed, or even bare panels) as a result of
Steady state behavior of rotating plasmas in a vacuum-arc centrifuge
International Nuclear Information System (INIS)
Bittencourt, J.A.; Ludwig, G.O.
1987-01-01
The steady state behaviour of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is shown that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed in light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (author)
Steady state behavior of rotating plasmas in a vacuum-arc centrifuge
International Nuclear Information System (INIS)
Bittencourt, J.A.; Ludwig, G.O.
1986-06-01
The steady state behavior of the fully ionized, multiple species, rotating, magnetized plasma in a vacuum-arc plasma centrifuge is described in detail. The analysis is based on a multiple species fluid model which includes electromagnetic, pressure gradient, centrifugal and collisional forces, for each species, in cylindrical geometry. It is showm that there is a family of theoretically possible dynamical equilibrium configurations, which can be achieved by different combinations of ion rotation velocity, radial ion density distribution and radial dependence of internal electric potential. The parametric dependences of the various plasma parameters under equilibrium conditions, including the ion separation factor, are presented for a nickel-copper plasma. The numerical results are analysed and discussed on light of experimentally measured plasma characteristics in a vacuum-arc plasma centrifuge. (Author) [pt
Fast Virtual Fractional Flow Reserve Based Upon Steady-State Computational Fluid Dynamics Analysis
Directory of Open Access Journals (Sweden)
Paul D. Morris, PhD
2017-08-01
Full Text Available Fractional flow reserve (FFR-guided percutaneous intervention is superior to standard assessment but remains underused. The authors have developed a novel “pseudotransient” analysis protocol for computing virtual fractional flow reserve (vFFR based upon angiographic images and steady-state computational fluid dynamics. This protocol generates vFFR results in 189 s (cf >24 h for transient analysis using a desktop PC, with <1% error relative to that of full-transient computational fluid dynamics analysis. Sensitivity analysis demonstrated that physiological lesion significance was influenced less by coronary or lesion anatomy (33% and more by microvascular physiology (59%. If coronary microvascular resistance can be estimated, vFFR can be accurately computed in less time than it takes to make invasive measurements.
Steady State Analysis of LCLC Resonant Converter with Capacitive Output Filter
Directory of Open Access Journals (Sweden)
Navid Shafiyi
2010-01-01
Full Text Available This paper presents the mathematical analysis and modeling of a 4th order LCLC resonant converter with capacitive output filter in steady-state condition. Due to the nonlinearity of the LCLC resonant circuit with capacitive output filter, the conventional modeling procedure cannot thoroughly describe the behavior of the converter. In this paper, a mathematical model is proposed that can accommodate the absence of the output inductor and predict the converter performance for a wide range of operating conditions. A 2.25KW prototype converter is provided to evaluate the accuracy of the proposed model. Experimental results show that the proposed model can precisely predict the behavior of the converter for a wide range of operating conditions.
HYDRA-II: A hydrothermal analysis computer code: Volume 1, Equations and numerics
International Nuclear Information System (INIS)
McCann, R.A.
1987-04-01
HYDRA-II is a hydrothermal computer code capable of three-dimensional analysis of coupled conduction, convection, and thermal radiation problems. This code is especially appropriate for simulating the steady-state performance of spent fuel storage systems. The code has been evaluated for this application for the US Department of Energy's Commercial Spent Fuel Management Program. HYDRA-II provides a finite difference solution in Cartesian coordinates to the equations governing the conservation of mass, momentum, and energy. A cylindrical coordinate system may also be used to enclose the Cartesian coordinate system. This exterior coordinate system is useful for modeling cylindrical cask bodies. The difference equations for conservation of momentum are enhanced by the incorporation of directional porosities and permeabilities that aid in modeling solid structures whose dimensions may be smaller than the computational mesh. The equation for conservation of energy permits of modeling of orthotropic physical properties and film resistances. Several automated procedures are available to model radiation transfer within enclosures and from fuel rod to fuel rod. The documentation of HYDRA-II is presented in three separate volumes. This volume, Volume I - Equations and Numerics, describes the basic differential equations, illustrates how the difference equations are formulated, and gives the solution procedures employed. Volume II - User's Manual contains code flow charts, discusses the code structure, provides detailed instructions for preparing an input file, and illustrates the operation of the code by means of a model problem. The final volume, Volume III - Verification/Validation Assessments, presents results of numerical simulations of single- and multiassembly storage systems and comparisons with experimental data. 4 refs
Development of steady thermal-hydraulic analysis code for China advanced research reactor
International Nuclear Information System (INIS)
Tian Wenxi; Qiu Suizheng; Guo Yun; Su Guanghui; Jia Dounan; Liu Tiancai; Zhang Jianwei
2006-01-01
A multi-channel model steady-state thermal-hydraulic analysis code was developed for China Advanced Research Reactor (CARR). By simulating the whole reactor core, the detailed flow distribution in the core was obtained. The result shows that the structure size plays the most important role in flow distribution and the influence of core power could be neglected under single-phase flow. The temperature field of fuel element under unsymmetrical cooling condition was also obtained, which is necessary for the further study such as stress analysis etc. of the fuel element. At the same time, considering the hot channel effect including engineering factor and nuclear factor, calculation of hot channel was carried out and it is proved that all thermal-hydraulic parameters accord with the Safety Regulation of CARR. (authors)
Multiple solutions and stability of the steady transonic small-disturbance equation
Directory of Open Access Journals (Sweden)
Ya Liu
2017-09-01
Full Text Available Numerical solutions of the steady transonic small-disturbance (TSD potential equation are computed using the conservative Murman−Cole scheme. Multiple solutions are discovered and mapped out for the Mach number range at zero angle of attack and the angle of attack range at Mach number 0.85 for the NACA 0012 airfoil. We present a linear stability analysis method by directly assembling and evaluating the Jacobian matrix of the nonlinear finite-difference equation of the TSD equation. The stability of all the discovered multiple solutions are then determined by the proposed eigen analysis. The relation of stability to convergence of the iterative method for solving the TSD equation is discussed. Computations and the stability analysis demonstrate the possibility of eliminating the multiple solutions and stabilizing the remaining unique solution by adding a sufficiently long splitter plate downstream the airfoil trailing edge. Finally, instability of the solution of the TSD equation is shown to be closely connected to the onset of transonic buffet by comparing with experimental data.
How should we understand non-equilibrium many-body steady states?
Maghrebi, Mohammad; Gorshkov, Alexey
: Many-body systems with both coherent dynamics and dissipation constitute a rich class of models which are nevertheless much less explored than their dissipationless counterparts. The advent of numerous experimental platforms that simulate such dynamics poses an immediate challenge to systematically understand and classify these models. In particular, nontrivial many-body states emerge as steady states under non-equilibrium dynamics. In this talk, I use a field-theoretic approach based on the Keldysh formalism to study nonequilibrium phases and phase transitions in such models. I show that an effective temperature generically emerges as a result of dissipation, and the universal behavior including the dynamics near the steady state is described by a thermodynamic universality class. In the end, I will also discuss possibilities that go beyond the paradigm of an effective thermodynamic behavior.
International Nuclear Information System (INIS)
Verfondern, K.
1983-01-01
This work presents a computer model determining the steady-state temperature- and flow field in 3 dimensions in the core of a pebble bed high temperature reactor. The numerical sprinkler method, basind on the Thermix-model, allows to describe the thermo-hydraulics of a non-rotational-symmetric core-geometry. The AVR-reactor in Juelich, in operation since 1967, represents a suitable investigation-object for the computer model of Thermix-3D. It is in a 3D-mesh-structure to reproduce very precisely the so called ''graphite noses'', in which the shut-down rods are conducted as well as the filling cones in the inner and outer area. The results of the final calculation of the normal operation condition for the AVR-reactor unambiguously show, that within the core reproduced in 3 dimensions there are evident deviations in the flow profile and in the temperatures of the cooling gas in contrast to a 2D-handling. (orig.) [de
DEFF Research Database (Denmark)
Andersen, Lars; Nielsen, Søren R. K.
2003-01-01
The paper deals with the boundary element method formulation of the steady-state wave propagation through elastic media due to a source moving with constant velocity. The Greens' function for the three-dimensional full-space is formulated in a local frame of reference following the source...... is approximated, but the error which is introduced in this way is insignificant. Numerical examples are given for a moving rectangular load on an elastic half-space. The result from a boundary element code based on the derived Green's function are compared with a semi-analytic solution....
Three-dimensional stellarator equilibrium as an ohmic steady state
International Nuclear Information System (INIS)
Park, W.; Monticello, D.A.; Strauss, H.; Manickam, J.
1985-07-01
A stable three-dimensional stellarator equilibrium can be obtained numerically by a time-dependent relaxation method using small values of dissipation. The final state is an ohmic steady state which approaches an ohmic equilibrium in the limit of small dissipation coefficients. We describe a method to speed up the relaxation process and a method to implement the B vector . del p = 0 condition. These methods are applied to obtain three-dimensional heliac equilibria using the reduced heliac equations
Directory of Open Access Journals (Sweden)
Zhong Chen
2017-08-01
Full Text Available A conventional steady-state power flow security check only implements point-by-point assessment, which cannot provide a security margin for system operation. The concept of a steady-state security region is proposed to effectively tackle this problem. Considering that the commissioning of the increasing number of HVDC (High Voltage Direct Current and the fluctuation of renewable energy have significantly affected the operation and control of a conventional AC system, the definition of the steady-state security region of the AC/DC power system is proposed in this paper based on the AC/DC power flow calculation model including LCC/VSC (Line Commutated Converter/Voltage Sourced Converter-HVDC transmission and various AC/DC constraints, and hence the application of the security region is extended. In order to ensure that the proposed security region can accurately provide global security information of the power system under the fluctuations of renewable energy, this paper presents four methods (i.e., a screening method of effective boundary surfaces, a fitting method of boundary surfaces, a safety judging method, and a calculation method of distances and corrected distance between the steady-state operating point and the effective boundary surfaces based on the relation analysis between the steady-state security region geometry and constraints. Also, the physical meaning and probability analysis of the corrected distance are presented. Finally, a case study is demonstrated to test the feasibility of the proposed methods.
Low Mach number analysis of idealized thermoacoustic engines with numerical solution.
Hireche, Omar; Weisman, Catherine; Baltean-Carlès, Diana; Le Quéré, Patrick; Bauwens, Luc
2010-12-01
A model of an idealized thermoacoustic engine is formulated, coupling nonlinear flow and heat exchange in the heat exchangers and stack with a simple linear acoustic model of the resonator and load. Correct coupling results in an asymptotically consistent global model, in the small Mach number approximation. A well-resolved numerical solution is obtained for two-dimensional heat exchangers and stack. The model assumes that the heat exchangers and stack are shorter than the overall length by a factor of the order of a representative Mach number. The model is well-suited for simulation of the entire startup process, whereby as a result of some excitation, an initially specified temperature profile in the stack evolves toward a near-steady profile, eventually reaching stationary operation. A validation analysis is presented, together with results showing the early amplitude growth and approach of a stationary regime. Two types of initial excitation are used: Random noise and a small periodic wave. The set of assumptions made leads to a heat-exchanger section that acts as a source of volume but is transparent to pressure and to a local heat-exchanger model characterized by a dynamically incompressible flow to which a locally spatially uniform acoustic pressure fluctuation is superimposed.
Incomplete augmented Lagrangian preconditioner for steady incompressible Navier-Stokes equations.
Tan, Ning-Bo; Huang, Ting-Zhu; Hu, Ze-Jun
2013-01-01
An incomplete augmented Lagrangian preconditioner, for the steady incompressible Navier-Stokes equations discretized by stable finite elements, is proposed. The eigenvalues of the preconditioned matrix are analyzed. Numerical experiments show that the incomplete augmented Lagrangian-based preconditioner proposed is very robust and performs quite well by the Picard linearization or the Newton linearization over a wide range of values of the viscosity on both uniform and stretched grids.
International Nuclear Information System (INIS)
Mbagwu, J.S.C.
1993-10-01
A knowledge of physical properties influencing the steady-state infiltration rates (ic) of soils is needed for the hydrologic modelling of the infiltration process. In this study evidence is provided to show that effective porosity (Pe) (i.e. the proportion of macro pore spaces with equivalent radius of > 15 μm) and dry bulk density are the most important soil physical properties controlling the steady-state infiltration rates on a tropical savannah with varying land use histories. At a macro porosity value of ≤ 5.0% the steady-state infiltration rate is zero. Total porosity and the proportion of water-retaining pores explained only a small fraction of the variation in this property. Steady-state infiltration rates can also be estimated from either the saturated hydraulic conductivity (Ks) by the equation, i c = 31.1 + 1.06 (Ks), (R 2 = 0.8104, p ≤ 0.001) or the soil water transmissivity (A) by the equation, i c = 30.0 + 29.9(A), (R 2 = 0.8228, ρ ≤ 0.001). The Philip two-parameter model under predicted steady-state infiltration rates generally. Considering the ease of determination and reliability it is suggested that effective porosity be used to estimate the steady-state infiltration rates of these other soils with similar characteristics. The model is, i c 388.7(Pe) - 10.8(R 2 = 0.7265, p ≤ 0.001) where i c is in (cm/hr) and Pe in (cm 3 /cm 3 ). (author). 20 refs, 3 figs, 4 tabs
International Nuclear Information System (INIS)
Ayazuddin, S.K.; Qureshi, A.A.; Hayat, T.
1997-11-01
The Primary Water Inlet Pipeline (PW-IPL) is of stainless steel conveying demineralized water from hold-up tank to the reactor pool of Pakistan Research Reactor-1 (PARR-1). The section of the pipeline from heat exchangers to the valve pit is hanger supported in the pump room and the rest of the section from valve pit to the reactor pool is embedded. The PW-IPL is subjected to steady state and transient vibrations. The reactor pumps, which drive the coolant through various circuits mainly contribute the steady state vibrations, while transient vibrations arise due to instant closure of the check valve (water hammer). The ASME Boiler and Pressure Vessel code provides data about the acceptable limits of stresses related to the primary static stress due to steady state vibrations. However, due to complexity in the pipe structure, stresses related to the transient vibrations are neglected in the code. In this report attempt has been made to analyzed both steady state and transient vibrations of PW-IPL of PARR-1. Since, both the steady state and transient vibrations affect the hanger-supported section of the PW-IPL, therefore, it was selected for vibration test measurements. In the analysis vibration data was compared with the allowable limits and estimations of maximum pressure build-up, eflection, natural frequency, tensile and shear load on hanger support, and the ratio of maximum combine stress to the allowable load were made. (author)
Steady state thermal hydraulic analysis of LMR core using COBRA-K code
Energy Technology Data Exchange (ETDEWEB)
Kim, Eui Kwang; Kim, Young Gyun; Kim Young In; Kim Young Cheol
1997-02-01
A thermal hydraulics analysis code COBRA-K is being developed by the KAERI LMR core design technology development team. COBRA-K is a part of the integrated computation system for LMR core design and analysis, the K-CORE system. COBRA-K is supposed to predict the flow and temperature distributions in LMR core. COBRA-K is an extension of the previously published COBRA-IV-I code with several functional improvements. Specially COBRA-K has been improved to analyze single and multi-assembly, and whole-core in the transient condition. This report describes the overall features of COBRA-K and gives general input descriptions. The 19 pin assembly experimental data of ORNL were used to verify the accuracy of this code for the steady state analysis. The comparative results show good agreements between the calculated and the measured data. And COBRA-K can be used to predict flow and temperature distributions for the LMR core design. (author). 7 refs., 6 tabs., 13 figs.
SAFE: A computer code for the steady-state and transient thermal analysis of LMR fuel elements
International Nuclear Information System (INIS)
Hayes, S.L.
1993-12-01
SAFE is a computer code developed for both the steady-state and transient thermal analysis of single LMR fuel elements. The code employs a two-dimensional control-volume based finite difference methodology with fully implicit time marching to calculate the temperatures throughout a fuel element and its associated coolant channel for both the steady-state and transient events. The code makes no structural calculations or predictions whatsoever. It does, however, accept as input structural parameters within the fuel such as the distributions of porosity and fuel composition, as well as heat generation, to allow a thermal analysis to be performed on a user-specified fuel structure. The code was developed with ease of use in mind. An interactive input file generator and material property correlations internal to the code are available to expedite analyses using SAFE. This report serves as a complete design description of the code as well as a user's manual. A sample calculation made with SAFE is included to highlight some of the code's features. Complete input and output files for the sample problem are provided
International Nuclear Information System (INIS)
Pal, G.; MaarKandeya, S.G.; Raj, V.V.
1991-01-01
This paper deals with the calculation of radiative heat exchange in a rod array exposed to stagnant gaseous environment. a computer code has been developed for this purpose and has been used for predicting the steady state temperature distribution in a nuclear fuel sub-assembly. Nuclear fuels continue to generate heat even after their removal from the core. During the transfer of the nuclear fuel sub-assemblies from the core to the storage bay, they pass through stagnant gaseous environment and may remain there for extended periods under abnormal conditions. Radiative heat exchange will be the dominant mode within the sub-assembly involved, since axial heat conduction through the fuel pins needs to be accounted for. a computer code RHEINA-3D (Radiative Heat Exchange In Nuclear Assemblies -3D) has been developed based on a simplified numerical model which considers both the above-mentioned phenomena. The analytical model and the results obtained are briefly discussed in this paper
Numerical model for two-dimensional hydrodynamics and energy transport. [VECTRA code
Energy Technology Data Exchange (ETDEWEB)
Trent, D.S.
1973-06-01
The theoretical basis and computational procedure of the VECTRA computer program are presented. VECTRA (Vorticity-Energy Code for TRansport Analysis) is designed for applying numerical simulation to a broad range of intake/discharge flows in conjunction with power plant hydrological evaluation. The code computational procedure is based on finite-difference approximation of the vorticity-stream function partial differential equations which govern steady flow momentum transport of two-dimensional, incompressible, viscous fluids in conjunction with the transport of heat and other constituents.
Steady state likelihood ratio sensitivity analysis for stiff kinetic Monte Carlo simulations.
Núñez, M; Vlachos, D G
2015-01-28
Kinetic Monte Carlo simulation is an integral tool in the study of complex physical phenomena present in applications ranging from heterogeneous catalysis to biological systems to crystal growth and atmospheric sciences. Sensitivity analysis is useful for identifying important parameters and rate-determining steps, but the finite-difference application of sensitivity analysis is computationally demanding. Techniques based on the likelihood ratio method reduce the computational cost of sensitivity analysis by obtaining all gradient information in a single run. However, we show that disparity in time scales of microscopic events, which is ubiquitous in real systems, introduces drastic statistical noise into derivative estimates for parameters affecting the fast events. In this work, the steady-state likelihood ratio sensitivity analysis is extended to singularly perturbed systems by invoking partial equilibration for fast reactions, that is, by working on the fast and slow manifolds of the chemistry. Derivatives on each time scale are computed independently and combined to the desired sensitivity coefficients to considerably reduce the noise in derivative estimates for stiff systems. The approach is demonstrated in an analytically solvable linear system.
DEFF Research Database (Denmark)
Rasmussen, Filip Salling; Sonne, Mads Rostgaard; Larsen, Martin
In the present study, a two-dimensional (2D) transient Eulerian thermo-chemical analysis of a carbon fibre epoxy thermosetting Resin Injection Pultrusion (RIP) process is carried out. The numerical model is implemented using the well known unconditionally stable Alternating Direction Implicit (ADI......) scheme. The total heat of reaction and the cure kinetics of the epoxy thermosetting are determined using Differential Scanning Calorimetry (DSC). A very good agreement is observed between the fitted cure kinetic model and the experimental measurements. The numerical steady state temperature predictions...
Numerical analysis II essentials
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.
Comparing Interval Management Control Laws for Steady-State Errors and String Stability
Weitz, Lesley A.; Swieringa, Kurt A.
2018-01-01
Interval Management (IM) is a future airborne spacing concept that leverages avionics to provide speed guidance to an aircraft to achieve and maintain a specified spacing interval from another aircraft. The design of a speed control law to achieve the spacing goal is a key aspect in the research and development of the IM concept. In this paper, two control laws that are used in much of the contemporary IM research are analyzed and compared to characterize steady-state errors and string stability. Numerical results are used to illustrate how the choice of control laws gains impacts the size of steady-state errors and string performance and the potential trade-offs between those performance characteristics.
Mathematical theory of compressible viscous fluids analysis and numerics
Feireisl, Eduard; Pokorný, Milan
2016-01-01
This book offers an essential introduction to the mathematical theory of compressible viscous fluids. The main goal is to present analytical methods from the perspective of their numerical applications. Accordingly, we introduce the principal theoretical tools needed to handle well-posedness of the underlying Navier-Stokes system, study the problems of sequential stability, and, lastly, construct solutions by means of an implicit numerical scheme. Offering a unique contribution – by exploring in detail the “synergy” of analytical and numerical methods – the book offers a valuable resource for graduate students in mathematics and researchers working in mathematical fluid mechanics. Mathematical fluid mechanics concerns problems that are closely connected to real-world applications and is also an important part of the theory of partial differential equations and numerical analysis in general. This book highlights the fact that numerical and mathematical analysis are not two separate fields of mathematic...
Identification of the Diffusion Parameter in Nonlocal Steady Diffusion Problems
Energy Technology Data Exchange (ETDEWEB)
D’Elia, M., E-mail: mdelia@fsu.edu, E-mail: mdelia@sandia.gov [Sandia National Laboratories (United States); Gunzburger, M. [Florida State University (United States)
2016-04-15
The problem of identifying the diffusion parameter appearing in a nonlocal steady diffusion equation is considered. The identification problem is formulated as an optimal control problem having a matching functional as the objective of the control and the parameter function as the control variable. The analysis makes use of a nonlocal vector calculus that allows one to define a variational formulation of the nonlocal problem. In a manner analogous to the local partial differential equations counterpart, we demonstrate, for certain kernel functions, the existence of at least one optimal solution in the space of admissible parameters. We introduce a Galerkin finite element discretization of the optimal control problem and derive a priori error estimates for the approximate state and control variables. Using one-dimensional numerical experiments, we illustrate the theoretical results and show that by using nonlocal models it is possible to estimate non-smooth and discontinuous diffusion parameters.
Helmi Manggala Putri, Arum; Subekti, Retno; Binatari, Nikenasih
2017-06-01
Dr Yap Eye Hospital Yogyakarta is one of the most popular reference eye hospitals in Yogyakarta. There are so many patients coming from other cities and many of them are BPJS (Badan Penyelenggara Jaminan Sosial, Social Security Administrative Bodies) patients. Therefore, it causes numerous BPJS patients were in long queue at counter C of the registration section so that it needs to be analysed using queue system. Queue system analysis aims to give queue model overview and determine its effectiveness measure. The data collecting technique used in this research are by interview and observation. After getting the arrival data and the service data of BPJS patients per 5 minutes, the next steps are investigating steady-state condition, examining the Poisson distribution, determining queue models, and counting the effectiveness measure. Based on the result of data observation on Tuesday, February 16th, 2016, it shows that the queue system at counter C has (M/M/1):(GD/∞/∞) queue model. The analysis result in counter C shows that the queue system is a non-steady-state condition. Three ways to cope a non-steady-state problem on queue system are proposed in this research such as bounding the capacity of queue system, adding the servers, and doing Monte Carlo simulation. The queue system in counter C will reach steady-state if the capacity of patients is not more than 52 BPJS patients or adding one more server. By using Monte Carlo simulation, it shows that the effectiveness measure of the average waiting time for BPJS patients in counter C is 36 minutes 65 seconds. In addition, the average queue length of BPJS patients is 11 patients.
Rosenblatt, Marcus; Timmer, Jens; Kaschek, Daniel
2016-01-01
Ordinary differential equation models have become a wide-spread approach to analyze dynamical systems and understand underlying mechanisms. Model parameters are often unknown and have to be estimated from experimental data, e.g., by maximum-likelihood estimation. In particular, models of biological systems contain a large number of parameters. To reduce the dimensionality of the parameter space, steady-state information is incorporated in the parameter estimation process. For non-linear models, analytical steady-state calculation typically leads to higher-order polynomial equations for which no closed-form solutions can be obtained. This can be circumvented by solving the steady-state equations for kinetic parameters, which results in a linear equation system with comparatively simple solutions. At the same time multiplicity of steady-state solutions is avoided, which otherwise is problematic for optimization. When solved for kinetic parameters, however, steady-state constraints tend to become negative for particular model specifications, thus, generating new types of optimization problems. Here, we present an algorithm based on graph theory that derives non-negative, analytical steady-state expressions by stepwise removal of cyclic dependencies between dynamical variables. The algorithm avoids multiple steady-state solutions by construction. We show that our method is applicable to most common classes of biochemical reaction networks containing inhibition terms, mass-action and Hill-type kinetic equations. Comparing the performance of parameter estimation for different analytical and numerical methods of incorporating steady-state information, we show that our approach is especially well-tailored to guarantee a high success rate of optimization.
Voytek, E. B.; Drenkelfuss, A.; Day-Lewis, F. D.; Healy, R. W.; Lane, J. W.; Werkema, D. D.
2012-12-01
Temperature is a naturally occurring tracer, which can be exploited to infer the movement of water through the vadose and saturated zones, as well as the exchange of water between aquifers and surface-water bodies, such as estuaries, lakes, and streams. One-dimensional (1D) vertical temperature profiles commonly show thermal amplitude attenuation and increasing phase lag of diurnal or seasonal temperature variations with propagation into the subsurface. This behavior is described by the heat-transport equation (i.e., the convection-conduction-dispersion equation), which can be solved analytically in 1D under certain simplifying assumptions (e.g., sinusoidal or steady-state boundary conditions and homogeneous hydraulic and thermal properties). Analysis of 1D temperature profiles using analytical models provides estimates of vertical groundwater/surface-water exchange. The utility of these estimates can be diminished when the model assumptions are violated, as is common in field applications. Alternatively, analysis of 1D temperature profiles using numerical models allows for consideration of more complex and realistic boundary conditions. However, such analyses commonly require model calibration and the development of input files for finite-difference or finite-element codes. To address the calibration and input file requirements, a new computer program, 1DTempPro, is presented that facilitates numerical analysis of vertical 1D temperature profiles. 1DTempPro is a graphical user interface (GUI) to the USGS code VS2DH, which numerically solves the flow- and heat-transport equations. Pre- and post-processor features within 1DTempPro allow the user to calibrate VS2DH models to estimate groundwater/surface-water exchange and hydraulic conductivity in cases where hydraulic head is known. This approach improves groundwater/ surface-water exchange-rate estimates for real-world data with complexities ill-suited for examination with analytical methods. Additionally, the code
Mathematical and numerical analysis of PN models for photons transport problems
International Nuclear Information System (INIS)
Valentin, Xavier
2015-01-01
Computational costs for direct numerical simulations of photon transport problems are very high in terms of CPU time and memory. One way to tackle this issue is to develop reduced models that a cheaper to solve numerically. There exists number of these models: moments models, discrete ordinates models (S N ), diffusion-like models... In this thesis, we focus on P N models in which the transport operator is approached by mean of a truncated development on the spherical harmonics basis. These models are arbitrary accurate in the angular dimension and are rotationally invariants (in multiple space dimensions). The latter point is fundamental when one wants to simulate inertial confinement fusion (ICF) experiments where the spherical symmetry plays an important part in the accuracy of the numerical solutions. We study the mathematical structure of the PN models and construct a new numerical method in the special case of a one dimensional space dimension with spherical symmetry photon transport problems. We first focus on a linear transport problem in the vacuum. Even in this simple case, it appears in the P N equations geometrical source terms that are stiff in the neighborhood of r = 0 and thus hard to discretize. Existing numerical methods are not satisfactory for multiple reasons: (1) inaccuracy in the neighborhood of r = 0 ('flux-dip'), (2) do not capture steady states (well-balanced scheme), (3) no stability proof. Following recent works, we develop a new well-balanced scheme for which we show the L 2 stability. We then extend the scheme for photon transport problems within a no moving media, the linear Boltzmann equation, and interest ourselves on its behavior in the diffusion limit (asymptotic-preserving property). In a second part, we consider radiation hydrodynamics problems. Since modelization of these problems is still under discussion in the literature, we compare a set of existing models by mean of mathematical analysis and establish a hierarchy
Numerical prediction of Pelton turbine efficiency
Energy Technology Data Exchange (ETDEWEB)
Jott, D; Mez' nar, P; Lipej, A, E-mail: dragicajost@turboinstitut.s [Turbointtitut, Rovtnikova 7, Ljubljana, 1210 (Slovenia)
2010-08-15
This paper presents a numerical analysis of flow in a 2 jet Pelton turbine with horizontal axis. The analysis was done for the model at several operating points in different operating regimes. The results were compared to the results of a test of the model. Analysis was performed using ANSYS CFX-12.1 computer code. A k-{omega} SST turbulent model was used. Free surface flow was modelled by two-phase homogeneous model. At first, a steady state analysis of flow in the distributor with two injectors was performed for several needle strokes. This provided us with data on flow energy losses in the distributor and the shape and velocity of jets. The second step was an unsteady analysis of the runner with jets. Torque on the shaft was then calculated from pressure distribution data. Averaged torque values are smaller than measured ones. Consequently, calculated turbine efficiency is also smaller than the measured values, the difference is about 4 %. The shape of the efficiency diagram conforms well to the measurements.
Numerical prediction of Pelton turbine efficiency
Jošt, D.; Mežnar, P.; Lipej, A.
2010-08-01
This paper presents a numerical analysis of flow in a 2 jet Pelton turbine with horizontal axis. The analysis was done for the model at several operating points in different operating regimes. The results were compared to the results of a test of the model. Analysis was performed using ANSYS CFX-12.1 computer code. A k-ω SST turbulent model was used. Free surface flow was modelled by two-phase homogeneous model. At first, a steady state analysis of flow in the distributor with two injectors was performed for several needle strokes. This provided us with data on flow energy losses in the distributor and the shape and velocity of jets. The second step was an unsteady analysis of the runner with jets. Torque on the shaft was then calculated from pressure distribution data. Averaged torque values are smaller than measured ones. Consequently, calculated turbine efficiency is also smaller than the measured values, the difference is about 4 %. The shape of the efficiency diagram conforms well to the measurements.
Numerical prediction of Pelton turbine efficiency
International Nuclear Information System (INIS)
Jott, D; Mez'nar, P; Lipej, A
2010-01-01
This paper presents a numerical analysis of flow in a 2 jet Pelton turbine with horizontal axis. The analysis was done for the model at several operating points in different operating regimes. The results were compared to the results of a test of the model. Analysis was performed using ANSYS CFX-12.1 computer code. A k-ω SST turbulent model was used. Free surface flow was modelled by two-phase homogeneous model. At first, a steady state analysis of flow in the distributor with two injectors was performed for several needle strokes. This provided us with data on flow energy losses in the distributor and the shape and velocity of jets. The second step was an unsteady analysis of the runner with jets. Torque on the shaft was then calculated from pressure distribution data. Averaged torque values are smaller than measured ones. Consequently, calculated turbine efficiency is also smaller than the measured values, the difference is about 4 %. The shape of the efficiency diagram conforms well to the measurements.
International Nuclear Information System (INIS)
Liu, Y B; Su, Y M; Ju, L; Huang, S L
2012-01-01
A new numerical method was developed for predicting the steady hydrodynamic performance of propeller-rudder-bulb system. In the calculation, the rudder and bulb was taken into account as a whole, the potential based surface panel method was applied both to propeller and rudder-bulb system. The interaction between propeller and rudder-bulb was taken into account by velocity potential iteration in which the influence of propeller rotation was considered by the average influence coefficient. In the influence coefficient computation, the singular value should be found and deleted. Numerical results showed that the method presented is effective for predicting the steady hydrodynamic performance of propeller-rudder system and propeller-rudder-bulb system. Comparing with the induced velocity iterative method, the method presented can save programming and calculation time. Changing dimensions, the principal parameter—bulb size that affect energy-saving effect was studied, the results show that the bulb on rudder have a optimal size at the design advance coefficient.
Rubinato, Matteo; Martins, Ricardo; Kesserwani, Georges; Leandro, Jorge; Djordjević, Slobodan; Shucksmith, James
2017-09-01
The linkage between sewer pipe flow and floodplain flow is recognised to induce an important source of uncertainty within two-dimensional (2D) urban flood models. This uncertainty is often attributed to the use of empirical hydraulic formulae (the one-dimensional (1D) weir and orifice steady flow equations) to achieve data-connectivity at the linking interface, which require the determination of discharge coefficients. Because of the paucity of high resolution localised data for this type of flows, the current understanding and quantification of a suitable range for those discharge coefficients is somewhat lacking. To fulfil this gap, this work presents the results acquired from an instrumented physical model designed to study the interaction between a pipe network flow and a floodplain flow. The full range of sewer-to-surface and surface-to-sewer flow conditions at the exchange zone are experimentally analysed in both steady and unsteady flow regimes. Steady state measured discharges are first analysed considering the relationship between the energy heads from the sewer flow and the floodplain flow; these results show that existing weir and orifice formulae are valid for describing the flow exchange for the present physical model, and yield new calibrated discharge coefficients for each of the flow conditions. The measured exchange discharges are also integrated (as a source term) within a 2D numerical flood model (a finite volume solver to the 2D Shallow Water Equations (SWE)), which is shown to reproduce the observed coefficients. This calibrated numerical model is then used to simulate a series of unsteady flow tests reproduced within the experimental facility. Results show that the numerical model overestimated the values of mean surcharge flow rate. This suggests the occurrence of additional head losses in unsteady conditions which are not currently accounted for within flood models calibrated in steady flow conditions.
Numerical analysis of steady state fluid flow in a two-dimensional wavy channel
International Nuclear Information System (INIS)
Gorji, M.; Hosseinzadeh, E.
2007-01-01
A simple geometry of the flow passage that may be used to enhance the heat transfer rate is called wavy and periodic channel. Wavy channel can provide significant heat transfer augmentation and was always important for heat transfer engineering and so far many researches have been done in this field. In this paper, the effects of channel geometry and Reynolds number on the heat transfer coefficient, heat flux and pressure drop for the laminar fully developed flow in a two dimensional channel whereas the walls are considered fix temperature is numerically investigated. The problem is solved for channel with one and two wavy walls and comparisons with the straight channel, in the same flow rate, have been performed. Results indicate that, by decreasing the channel wave length and the distance between the channel walls the pressure drop, heat flux and heat transfer coefficient increase. Results and Conclusions: The following conclusion may be drawn: 1. In a specified channel, for the fluid flow with the constant Reynolds number, by decreasing the wave length from 0.2 m to 0.1 m, the pressure drop, heat flux and heat transfer coefficient increase by 37% , 54% and 29% respectively, whereas by decreasing the wave length from the same value the above mentioned parameters decrease to 108% , 143% and 47% respectively. 2. In a specified wave length, where the amplitude and the Reynolds number is constant, by increasing the distance between the walls from 0.15 m to 0.25 m, the pressure drop, heat flux and heat transfer coefficient decrease by 41% ,8% and 7.8% respectively. References [1] J.C. Burns, T. Parks, J. Fluid Mesh, 29(1967), 405-416. [2] J.L. Goldestein, E.M. Sparrow, ASME J. Heat Transfer, 99 (1977), 187. [3] J.E.O. Brain, E.M. Sparrow, ASME J. Heat Transfer, 104 (1982), 410 [4] N. Sanie, S. Dini, ASME J. Heat Transfer, 115 (1993), 788. [5] G. Wang, P. Vanka, Int. J. Heat Mass Transfer, 38 (17) (1995), 3219. [6] T.A. Rush, T.A. Newell, A.M. Jacobi, Int, J. Heat Mass
Importance sampling large deviations in nonequilibrium steady states. I
Ray, Ushnish; Chan, Garnet Kin-Lic; Limmer, David T.
2018-03-01
Large deviation functions contain information on the stability and response of systems driven into nonequilibrium steady states and in such a way are similar to free energies for systems at equilibrium. As with equilibrium free energies, evaluating large deviation functions numerically for all but the simplest systems is difficult because by construction they depend on exponentially rare events. In this first paper of a series, we evaluate different trajectory-based sampling methods capable of computing large deviation functions of time integrated observables within nonequilibrium steady states. We illustrate some convergence criteria and best practices using a number of different models, including a biased Brownian walker, a driven lattice gas, and a model of self-assembly. We show how two popular methods for sampling trajectory ensembles, transition path sampling and diffusion Monte Carlo, suffer from exponentially diverging correlations in trajectory space as a function of the bias parameter when estimating large deviation functions. Improving the efficiencies of these algorithms requires introducing guiding functions for the trajectories.
Importance sampling large deviations in nonequilibrium steady states. I.
Ray, Ushnish; Chan, Garnet Kin-Lic; Limmer, David T
2018-03-28
Large deviation functions contain information on the stability and response of systems driven into nonequilibrium steady states and in such a way are similar to free energies for systems at equilibrium. As with equilibrium free energies, evaluating large deviation functions numerically for all but the simplest systems is difficult because by construction they depend on exponentially rare events. In this first paper of a series, we evaluate different trajectory-based sampling methods capable of computing large deviation functions of time integrated observables within nonequilibrium steady states. We illustrate some convergence criteria and best practices using a number of different models, including a biased Brownian walker, a driven lattice gas, and a model of self-assembly. We show how two popular methods for sampling trajectory ensembles, transition path sampling and diffusion Monte Carlo, suffer from exponentially diverging correlations in trajectory space as a function of the bias parameter when estimating large deviation functions. Improving the efficiencies of these algorithms requires introducing guiding functions for the trajectories.
Institute of Scientific and Technical Information of China (English)
ZHANG Da-Lin; QIU Sui-Zheng; LIU Chang-Liang; SU Guang-Hui
2008-01-01
The Molten Salt Reactor (MSR),one of the‘Generation Ⅳ'concepts,is a liquid-fuel reactor,which is different from the conventional reactors using solid fissile materials due to the flow effect of fuel salt.The study on its neutronice considering the fuel salt flow,which is the base of the thermal-hydraulic calculation and safety analysis,must be done.In this paper,the theoretical model on neutronics under steady condition for a single-liquid-fueled MSR is conducted and calculated by numerical method.The neutronics model consists of two group neutron diffusion equations for fast and thermal neutron fluxes,and balance equations for six-group delayed neutron precursors considering the flow effect of fuel salt. The spatial discretization of the above models is based on the finite volume method,and the discretization equations are computed by the source iteration method.The distributions of neutron fluxes and the distributions of the delayed neutron precursors in the core are obtained.The numerical calculated results show that,the fuel salt flow has little effect on the distribution of fast and thermal neutron fluxes and the effective multiplication factor;however,it affects the distribution of the delayed neutron precursors significantly,especially the long-lived one.In addition,it could be found that the delayed neutron precursors influence the nentronics slightly under the steady condition.
International Nuclear Information System (INIS)
Zhang Dalin; Qiu Suizheng; Su Guanghui; Liu Changliang
2008-01-01
The Molten Salt Reactor (MSR), one of the 'Generation IV' concepts, is a liquid-fuel reactor, which is different from the conventional reactors using solid fissile materials due to the flow effect of fuel salt. The study on its neutronics considering the fuel salt flow, which is the base of the thermal-hydraulic calculation and safety analysis, must be done. In this paper, the theoretical model on neutronics under steady condition for a single-liquid-fueled MSR is conducted and calculated by numerical method. The neutronics model consists of two group neutron diffusion equations for fast and thermal neutron fluxes, and balance equations for six-group delayed neutron precursors considering the flow effect of fuel salt. The spatial discretization of the above models is based on the finite volume method, and the discretization equations are computed by the source iteration method. The distributions of neutron fluxes and the distributions of the delayed neutron precursors in the core are obtained. The numerical calculated results show that, the fuel salt flow has little effect on the distribution of fast and thermal neutron fluxes and the effective multiplication factor; however, it affects the distribution of the delayed neutron precursors significantly, especially the long-lived one. In addition, it could be found that the delayed neutron precursors influence the neutronics slightly under the steady condition. (authors)
Directory of Open Access Journals (Sweden)
C. Nagarajan
2012-09-01
Full Text Available This paper presents a Closed Loop CLL-T (capacitor inductor inductor Series Parallel Resonant Converter (SPRC has been simulated and the performance is analysised. A three element CLL-T SPRC working under load independent operation (voltage type and current type load is presented in this paper. The Steady state Stability Analysis of CLL-T SPRC has been developed using State Space technique and the regulation of output voltage is done by using Fuzzy controller. The simulation study indicates the superiority of fuzzy control over the conventional control methods. The proposed approach is expected to provide better voltage regulation for dynamic load conditions. A prototype 300 W, 100 kHz converter is designed and built to experimentally demonstrate, dynamic and steady state performance for the CLL-T SPRC are compared from the simulation studies.
Numerical investigation of Rayleigh–Bénard convection in a cylinder of unit aspect ratio
Energy Technology Data Exchange (ETDEWEB)
Wang, Bo-Fu; Jiang, Jin [School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China); Zhou, Lin [Institute of Structural Mechanics, Chinese Academy of Engineering Physics, Mianyang, 621900 (China); Sun, De-Jun, E-mail: jinjiang@whu.edu.cn [Department of Modern Mechanics, University of Science and Technology of China, Hefei 230027 (China)
2016-02-15
Thermal convection in a vertical cylindrical cavity with a heated bottom, cooled top and insulated sidewall is investigated numerically. The radius to height ratio (Γ = height/radius) is fixed to unity and the Prandtl number is varied from 0.04 to 1. Rayleigh numbers up to 16 000 are considered in this study. Ten different kinds of flow regime have been identified, including both steady and unsteady patterns. The transition from steady to oscillatory flow occurs at a much lower Rayleigh number for small Prandtl number flow than for large Prandtl number flow. A bifurcation analysis shows the coexistence of two flow patterns in a certain parameter regime. The effect of flow structure on heat transfer is studied for a Prandtl number of unity. (paper)
International Nuclear Information System (INIS)
Oukaci, R.; Blackmond, D.G.; Goodwin, J.G. Jr.; Gallaher, G.R.
1992-01-01
In this paper, steady-state isotopic transient kinetic analysis (SSITKA) is used to study two model reactions, CO oxidation and CO-NO reactions, on a typical formulation of a three-way auto-catalyst. Under steady-state conditions, abrupt switches in the isotopic composition of CO ( 12 C 16 O/ 13 C 18 O) were carried out to produce isotopic transients in both labeled reactants and products. Along with the determination of the average surface lifetimes and concentrations of reaction intermediates, an analysis of the transient responses along the carbon reaction pathway indicated that the distribution of active sites for the formation of CO 2 was bimodal for both reactions. Furthermore, relatively few surface sites contributed to the overall reaction rate
Summary of research in applied mathematics, numerical analysis, and computer sciences
1986-01-01
The major categories of current ICASE research programs addressed include: numerical methods, with particular emphasis on the development and analysis of basic numerical algorithms; control and parameter identification problems, with emphasis on effective numerical methods; computational problems in engineering and physical sciences, particularly fluid dynamics, acoustics, and structural analysis; and computer systems and software, especially vector and parallel computers.
Numerical solution of High-kappa model of superconductivity
Energy Technology Data Exchange (ETDEWEB)
Karamikhova, R. [Univ. of Texas, Arlington, TX (United States)
1996-12-31
We present formulation and finite element approximations of High-kappa model of superconductivity which is valid in the high {kappa}, high magnetic field setting and accounts for applied magnetic field and current. Major part of this work deals with steady-state and dynamic computational experiments which illustrate our theoretical results numerically. In our experiments we use Galerkin discretization in space along with Backward-Euler and Crank-Nicolson schemes in time. We show that for moderate values of {kappa}, steady states of the model system, computed using the High-kappa model, are virtually identical with results computed using the full Ginzburg-Landau (G-L) equations. We illustrate numerically optimal rates of convergence in space and time for the L{sup 2} and H{sup 1} norms of the error in the High-kappa solution. Finally, our numerical approximations demonstrate some well-known experimentally observed properties of high-temperature superconductors, such as appearance of vortices, effects of increasing the applied magnetic field and the sample size, and the effect of applied constant current.
Stress Analysis of Non-Ferrous Metals Welds by Numerical Simulation
Directory of Open Access Journals (Sweden)
Kravarikova Helena
2017-01-01
Full Text Available Thermal energy welded material unevenly heated and thus supports the creation of tension. During the fusing process welding transient tensions generated in the welded material. Generation of the transient tensions depends on the thermal expansion and fixed permanently welded parts. Tensions are the result of the interaction of material particles. For welded parts and constructions it is necessary to know the size and direction of application of tensions. The emerging tensions can cause local change or a total deformation of welded materials. Deformations and residual stresses impair the performance of a welded construction, reduces the stability of the parts. To reduce or eliminate of action or a screening direction stresses and strains it is necessary to know the mechanism of their emergence. It is now possible to examine the emergence of tensions numerical experiments on any model using numerical simulation using FEM. Results of numerical experiment is the analysis of stress and deformation course. In the plane the tension it divided into normal σ and τ tangential folders. Decomposition stress on components simplifies the stress analysis. The results obtained from numerical analysis are correct to predict the stress distribution and size. The paper presents the results of numerical experiments stress analysis solutions fillet welds using FEM numerical simulation of welding of non-ferrous metals.
Numerical simulation on coolant flow and heat transfer in core
International Nuclear Information System (INIS)
Yao Zhaohui; Wang Xuefang; Shen Mengyu
1997-01-01
To simulate the coolant flow and the heat transfer characteristics of a core, a computer code, THAPMA (Thermal Hydraulic Analysis Porous Medium Analysis) has been developed. In THAPMA code, conservation equations are based on a porous-medium formulation, which uses four parameters, i.e, volume porosity, directional surface porosity, distributed resistance, and distributed heat source (sink), to model the effects of fuel rods and other internal solid structures on flow and heat transfer. Because the scheme and the solution are very important in accuracy and speed of calculation, a new difference scheme (WSUC) has been used in the energy equation, and a modified PISO solution method have been employed to simulate the steady/transient states. The code has been proved reliable and can effectively solve the transient state problem by several numerical tests. According to the design of Qinshan NPP-II, the flow and heat transfer phenomena in reactor core have been numerically simulated. The distributions of the velocity and the temperature can provide a theoretical basis for core design and safety analysis
Sjogreen, Bjoern; Yee, H. C.
2007-01-01
Flows containing steady or nearly steady strong shocks in parts of the flow field, and unsteady turbulence with shocklets on other parts of the flow field are difficult to capture accurately and efficiently employing the same numerical scheme even under the multiblock grid or adaptive grid refinement framework. On one hand, sixth-order or higher shock-capturing methods are appropriate for unsteady turbulence with shocklets. On the other hand, lower order shock-capturing methods are more effective for strong steady shocks in terms of convergence. In order to minimize the shortcomings of low order and high order shock-capturing schemes for the subject flows,a multi- block overlapping grid with different orders of accuracy on different blocks is proposed. Test cases to illustrate the performance of the new solver are included.
Numerical investigation of Dean vortices in a curved pipe
Bernad, S. I.; Totorean, A.; Bosioc, A.; Stanciu, R.; Bernad, E. S.
2013-10-01
This study is devoted to the three-dimensional numerical simulation of developing secondary flows of Newtonian fluid through a curved circular duct. The numerical simulations produced for different Dean numbers show clearly the presence of two steady Dean vortices. Therefore, results confirm that helical flow constitutes an important flow signature in vessels, and its strength as a fluid dynamic index.
Numerical Prediction of Wave Patterns Due to Motion of 3D Bodies by Kelvin-Havelock Sources
Directory of Open Access Journals (Sweden)
Ghassemi Hassan
2016-12-01
Full Text Available This paper discusses the numerical evaluation of the hydrodynamic characteristics of submerged and surface piercing moving bodies. Generally, two main classes of potential methods are used for hydrodynamic characteristic analysis of steady moving bodies which are Rankine and Kelvin-Havelock singularity distribution. In this paper, the Kelvin- Havelock sources are used for simulating the moving bodies and then free surface wave patterns are obtained. Numerical evaluation of potential distribution of a Kelvin-Havelock source is completely presented and discussed. Numerical results are calculated and presented for a 2D cylinder, single source, two parallel moving source, sphere, ellipsoid and standard Wigley hull in different situation that show acceptable agreement with results of other literatures or experiments.
Numerical methods design, analysis, and computer implementation of algorithms
Greenbaum, Anne
2012-01-01
Numerical Methods provides a clear and concise exploration of standard numerical analysis topics, as well as nontraditional ones, including mathematical modeling, Monte Carlo methods, Markov chains, and fractals. Filled with appealing examples that will motivate students, the textbook considers modern application areas, such as information retrieval and animation, and classical topics from physics and engineering. Exercises use MATLAB and promote understanding of computational results. The book gives instructors the flexibility to emphasize different aspects--design, analysis, or computer implementation--of numerical algorithms, depending on the background and interests of students. Designed for upper-division undergraduates in mathematics or computer science classes, the textbook assumes that students have prior knowledge of linear algebra and calculus, although these topics are reviewed in the text. Short discussions of the history of numerical methods are interspersed throughout the chapters. The book a...
Steady squares and hexagons on a subcritical ramp
International Nuclear Information System (INIS)
Hoyle, R.B.
1995-01-01
Steady squares and hexagons on a subcritical ramp are studied, both analytically and numerically, within the framework of the lowest-order amplitude equations. On the subcritical ramp, the external stress or control parameter varies continuously in space from subcritical to supercritical values. At the subcritical end of the ramp, pattern formation is suppressed, and patterns fade away into the conduction solution. It is shown that three-dimensional patterns may change shape on a subcritical ramp. A square pattern becomes a pattern of rolls as it fades, with the roll axes aligned in the direction orthogonal to that in which the control parameter varies. Hexagons in systems with horizontal midplane symmetry become a pattern of rectangles before reaching the conduction solution. There is a suggestion that hexagons in systems which lack this symmetry might fade away through a roll pattern. Numerical simulations are used to illustrate these phenomena
Numerical and experimental analysis on tensile properties of ...
Indian Academy of Sciences (India)
A Shadrach Jeyasekaran
2014-11-17
Nov 17, 2014 ... 4 Department of Electronics and Communication Engineering, Sri Sai ... the findings that the numerical analysis is found to be higher than experimental analysis. .... using ANSYS software has showed that the differences of.
Coupled neutronics and thermal-hydraulics numerical simulations of a Molten Salt Fast Reactor (MSFR)
International Nuclear Information System (INIS)
Laureau, A.; Rubiolo, P.R.; Heuer, D.; Merle-Lucotte, E.; Brovchenko, M.
2013-01-01
Coupled neutronics and thermalhydraulic numerical analyses of a molten salt fast reactor (MSFR) are presented. These preliminary numerical simulations are carried-out using the Monte Carlo code MCNP and the Computation Fluid Dynamic code OpenFOAM. The main objectives of this analysis performed at steady-reactor conditions are to confirm the acceptability of the current neutronic and thermalhydraulic designs of the reactor, to study the effects of the reactor operating conditions on some of the key MSFR design parameters such as the temperature peaking factor. The effects of the precursor's motion on the reactor safety parameters such as the effective fraction of delayed neutrons have been evaluated. (authors)
A method for statistical steady state thermal analysis of reactor cores
International Nuclear Information System (INIS)
Whetton, P.A.
1980-01-01
This paper presents a method for performing a statistical steady state thermal analysis of a reactor core. The technique is only outlined here since detailed thermal equations are dependent on the core geometry. The method has been applied to a pressurised water reactor core and the results are presented for illustration purposes. Random hypothetical cores are generated using the Monte-Carlo method. The technique shows that by splitting the parameters into two types, denoted core-wise and in-core, the Monte Carlo method may be used inexpensively. The idea of using extremal statistics to characterise the low probability events (i.e. the tails of a distribution) is introduced together with a method of forming the final probability distribution. After establishing an acceptable probability of exceeding a thermal design criterion, the final probability distribution may be used to determine the corresponding thermal response value. If statistical and deterministic (i.e. conservative) thermal response values are compared, information on the degree of pessimism in the deterministic method of analysis may be inferred and the restrictive performance limitations imposed by this method relieved. (orig.)
Steady-State-Preserving Simulation of Genetic Regulatory Systems
Directory of Open Access Journals (Sweden)
Ruqiang Zhang
2017-01-01
Full Text Available A novel family of exponential Runge-Kutta (expRK methods are designed incorporating the stable steady-state structure of genetic regulatory systems. A natural and convenient approach to constructing new expRK methods on the base of traditional RK methods is provided. In the numerical integration of the one-gene, two-gene, and p53-mdm2 regulatory systems, the new expRK methods are shown to be more accurate than their prototype RK methods. Moreover, for nonstiff genetic regulatory systems, the expRK methods are more efficient than some traditional exponential RK integrators in the scientific literature.
Characterization of steady streaming for a particle manipulation system.
Amit, Roni; Abadi, Avi; Kosa, Gabor
2016-04-01
Accurate positioning of biological cells or microscopic particle without directly contacting them is a challenging task in biomedical engineering. Various trapping methods for controlling the position of a particle have been suggested. The common driving methods are based on laser and ultrasonic actuation principles. In this work we suggest a design for a hydrodynamic particle manoeuvring system. The system operates using steady streaming in a viscous fluid media induced by high frequency vibration of piezoelectric cantilevers. A particle within the workspace of the system can be trapped and manipulated to a desired position by the fairly unidirectional flow field created by the beams. In this paper, the flow field in the particle manipulation system is characterized numerically and experimentally. We find that the flow field resembles the analytical solutions of a flow field created by an oscillating sphere. Furthermore, we validate numerically the quadratic relation between the steady streaming velocity and the vibration amplitude of the beam. The calibration of the piezoelectric actuator's oscillation amplitudes enables effective positioning of particles with a diameter of 20 um to 1 mm. We find that a 30X0.8X2 mm(3) piezoelectric beam vibrating at its first resonance frequency, 200 Hz, is able to move a particle at a typical flow velocity ranging between 0.05 mm/sec and 0.13 mm/s in 430 cSt Si oil (Re=0.2).
Scale effects on quasi-steady solid rocket internal ballistic behaviour
Energy Technology Data Exchange (ETDEWEB)
Greatrix, D. R. [Department of Aerospace Engineering, Ryerson University, 350 Victoria Street, Toronto, Ontario, M5B2K3 (Canada)
2010-11-15
The ability to predict with some accuracy a given solid rocket motor's performance before undertaking one or several costly experimental test firings is important. On the numerical prediction side, as various component models evolve, their incorporation into an overall internal ballistics simulation program allows for new motor firing simulations to take place, which in turn allows for updated comparisons to experimental firing data. In the present investigation, utilizing an updated simulation program, the focus is on quasi-steady performance analysis and scale effects (influence of motor size). The predicted effects of negative/positive erosive burning and propellant/casing deflection, as tied to motor size, on a reference cylindrical-grain motor's internal ballistics, are included in this evaluation. Propellant deflection has only a minor influence on the reference motor's internal ballistics, regardless of motor size. Erosive burning, on the other hand, is distinctly affected by motor scale. (author)
steady and dynamic states analysis of induction motor: fea approach
African Journals Online (AJOL)
HOD
The flux levels at these loading conditions were also monitored. Key words: Three phase Induction Motor, Steady state and Dynamic Response, Flux Levels, FEA, Loading conditions. 1. INTRODUCTION ..... Boston: Computational Mechanics Publications;. New York: ... for Electrical Engineers, Cambridge University. Press ...
Steady fall of isothermal, resistive-viscous, compressible fluid across magnetic field
Energy Technology Data Exchange (ETDEWEB)
Low, B. C., E-mail: low@ucar.edu [High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80301 (United States); Egan, A. K., E-mail: andrea.egan@colorado.edu [Barnard College, New York, New York 10027, USA and Department of Physics, Colorado University, Boulder, Colorado 80309 (United States)
2014-06-15
This is a basic MHD study of the steady fall of an infinite, vertical slab of isothermal, resistive-viscous, compressible fluid across a dipped magnetic field in uniform gravity. This double-diffusion steady flow in unbounded space poses a nonlinear but numerically tractable, one-dimensional (1D) free-boundary problem, assuming constant coefficients of resistivity and viscosity. The steady flow is determined by a dimensionless number μ{sub 1} proportional to the triple product of the two diffusion coefficients and the square of the linear total mass. For a sufficiently large μ{sub 1}, the Lorentz, viscous, fluid-pressure, and gravitational forces pack and collimate the fluid into a steady flow of a finite width defined by the two zero-pressure free-boundaries of the slab with vacuum. The viscous force is essential in this collimation effect. The study conjectures that in the regime μ{sub 1}→0, the 1D steady state exists only for μ{sub 1}∈Ω, a spectrum of an infinite number of discrete values, including μ{sub 1} = 0 that corresponds to two steady states, the classical zero-resistivity static slab of Kippenhahn and Schlüter [R. Kippenhahn and A. Schlüter, Z. Astrophys. 43, 36 (1957)] and its recent generalization [B. C. Low et al., Astrophys. J. 755, 34 (2012)] to admit an inviscid resistive flow. The pair of zero-pressure boundaries of each of the μ{sub 1}→0 steady-state slabs are located at infinity. Computational evidence suggests that the Ω steady-states are densely distributed around μ{sub 1} = 0, as an accumulation point, but are sparsely separated by open intervals of μ{sub 1}-values for which the slab must be either time-dependent or spatially multi-dimensional. The widths of these intervals are vanishingly small as μ{sub 1}→0. This topological structure of physical states is similar to that described by Landau and Liftshitz [L. D. Landau and E. M. Lifshitz, Fluid Mechanics (Addison-Wesley, Reading, MA, 1959)] to explain the onset
International Nuclear Information System (INIS)
Guidi, Leonardo F.; Marchetti, D.H.U.
2003-01-01
We establish a comparison between Rakib-Sivashinsky and Michelson-Sivashinsky quasilinear parabolic differential equations governing the weak thermal limit of flame front propagating in channels. For the former equation, we give a complete description of all steady solutions and present their local and global stability analysis. For the latter, bi-coalescent and interpolating unstable steady solutions are introduced and shown to be more numerous than the previous known coalescent solutions. These facts are argued to be responsible for the disagreement between the observed dynamics in numerical experiments and the exact (linear) stability analysis and give ingredients to construct quasi-stable solutions describing parabolic steadily propagating flame with centered tip
Steady State Structural Analysis of High Pressure Gas Turbine Blade using Finite Element Analysis
Mazarbhuiya, Hussain Mahamed Sahed Mostafa; Murari Pandey, Krishna
2017-08-01
In gas turbines the major portion of performance dependency lies upon turbine blade design. Turbine blades experience very high centrifugal, axial and tangential force during power generation. While withstanding these forces blades undergo elongation. Different methods have proposed for better enhancement of the mechanical properties of blade to withstand in extreme condition. Present paper describes the stress and elongation for blades having properties of different materials. Steady state structural analysis have performed in the present work for different materials (In 625, In 718, In 738, In 738 LC, MAR M246, Ni-Cr, Ti-alloy, Ti-Al, Ti-T6, U500). Remarkable finding is that the root of the blade is subjected to maximum stress for all blade materials and the blade made of MAR M246 has less stress and deformation among all other blade materials which can be selected as a suitable material for gas turbine blade.
Numerical analysis of the influence of liquid on propagation of a rolling contact fatigue crack
Directory of Open Access Journals (Sweden)
M. Olzak
2017-10-01
Full Text Available Numerical investigations of the propagation of rolling contact fatigue crack filled by the liquid have been conducted. Two models of fluid crack interaction have been considered. In the first model called 䖓hydrostatic� the assumption of incompressible, inviscid and weightless liquid was accepted. It was also assumed that due to the wheel load the trapped liquid could not get outside the crack and its volume remained constant until the rising pressure would open up the crack mouth again. On this assumption the analysis has a steady-state character. In the second model it has been assumed that the crack is filled by the viscous, incompressible fluid and the fluid motion as well as the resulting pressure distribution can be represented by one-dimensional form of the Reynolds equation. The method for solving the problem of the coupled motion of liquid and crack faces has been developed and series of calculation were made. The method has been employed for the predicting of crack deformation in the course of wheel rolling
Numerical calculation of velocity distribution near a vertical flat plate immersed in bubble flow
International Nuclear Information System (INIS)
Matsuura, Akihiro; Nakamura, Hajime; Horihata, Hideyuki; Hiraoka, Setsuro; Aragaki, Tsutomu; Yamada, Ikuho; Isoda, Shinji.
1992-01-01
Liquid and gas velocity distributions for bubble flow near a vertical flat plate were calculated numerically by using the SIMPLER method, where the flow was assumed to be laminar, two-dimensional, and at steady state. The two-fluid flow model was used in the numerical analysis. To calculate the drag force on a small bubble, Stokes' law for a rigid sphere is applicable. The dimensionless velocity distributions which were arranged with characteristic boundary layer thickness and maximum liquid velocity were adjusted with a single line and their forms were similar to that for single-phase wall-jet flow. The average wall shear stress derived from the velocity gradient at the plate wall was strongly affected by bubble diameter but not by inlet liquid velocity. The present dimensionless velocity distributions obtained numerically agreed well with previous experimental results, and the proposed numerical algorithm was validated. (author)
Steady state theta pinch concept for slow formation of FRC
International Nuclear Information System (INIS)
Hirano, K.
1987-05-01
A steady state high beta plasma flow through a channel along the magnetic field increasing downstream can be regarded as a ''steady state theta pinch'', because if we see the plasma riding on the flow we should observe very similar process taking place in a theta pinch. Anticipating to produce an FRC without using very high voltage technics such as the ones required in a conventional theta pinch, we have studied after the analogy a ''steady state reversed field theta pinch'' which is brought about by steady head-on collision of counter plasma streams along the channel as ejected from two identical co-axial plasma sources mounted at the both ends of the apparatus. The ideal Poisson and shock adiabatic flow models are employed for the analysis of the steady colliding process. It is demonstrated that an FRC involving large numbers of particles is produced only by the weak shock mode which is achieved in case energetic plasma flow is decelerated almost to be stagnated through Poisson adiabatic process before the streams are collided. (author)
Zhu, Jun; Shu, Chi-Wang
2017-11-01
A new class of high order weighted essentially non-oscillatory (WENO) schemes (Zhu and Qiu, 2016, [50]) is applied to solve Euler equations with steady state solutions. It is known that the classical WENO schemes (Jiang and Shu, 1996, [23]) might suffer from slight post-shock oscillations. Even though such post-shock oscillations are small enough in magnitude and do not visually affect the essentially non-oscillatory property, they are truly responsible for the residue to hang at a truncation error level instead of converging to machine zero. With the application of this new class of WENO schemes, such slight post-shock oscillations are essentially removed and the residue can settle down to machine zero in steady state simulations. This new class of WENO schemes uses a convex combination of a quartic polynomial with two linear polynomials on unequal size spatial stencils in one dimension and is extended to two dimensions in a dimension-by-dimension fashion. By doing so, such WENO schemes use the same information as the classical WENO schemes in Jiang and Shu (1996) [23] and yield the same formal order of accuracy in smooth regions, yet they could converge to steady state solutions with very tiny residue close to machine zero for our extensive list of test problems including shocks, contact discontinuities, rarefaction waves or their interactions, and with these complex waves passing through the boundaries of the computational domain.
Numerical analysis on the ion species ratios in a steady state hydrogen plasma
International Nuclear Information System (INIS)
Fukumasa, Osamu; Saeki, Setsuo; Osaki, Katashi; Sakiyama, Satoshi; Itatani, Ryohei.
1984-07-01
Ion species ratios in a hydrogen plasma are calculated systematically as a function of plasma parameters, i.e. the electron density, the electron temperature, the pressure of hydrogen gas and the plasma volume. Furthermore, in the present analysis, the recombination factor for hydrogen atoms at the wall surface of a vacuum vessel is treated as another plasma parameter. The most significant point is that ion species ratios depend strongly not only on plasma parameters, but also on the recombination factor. The proton ratio increases with decreasing value of the recombination factor. Primary electrons also play an important role for ion species ratios, and the presence of primary electrons causes the proton ratio to decrease. (author)
Steady State and Transient Analysis of Induction Motor Driving a ...
African Journals Online (AJOL)
The importance of using a digital computer in studying the performance of Induction machine under steady and transient states is presented with computer results which show the transient behaviour of 3-phase machine during balanced and unbalanced conditions. The computer simulation for these operating conditions is ...
Directory of Open Access Journals (Sweden)
Giri Lopamudra
2004-08-01
Full Text Available Abstract Background The phenomenon of switch-like response to graded input signal is the theme involved in various signaling pathways in living systems. Positive feedback loops or double negative feedback loops embedded with nonlinearity exhibit these switch-like bistable responses. Such feedback regulations exist in insulin signaling pathway as well. Methods In the current manuscript, a steady state analysis of the metabolic insulin-signaling pathway is presented. The threshold concentration of insulin required for glucose transporter GLUT4 translocation was studied with variation in system parameters and component concentrations. The dose response curves of GLUT4 translocation at various concentration of insulin obtained by steady state analysis were quantified in-terms of half saturation constant. Results We show that, insulin-stimulated GLUT4 translocation can operate as a bistable switch, which ensures that GLUT4 settles between two discrete, but mutually exclusive stable steady states. The threshold concentration of insulin required for GLUT4 translocation changes with variation in system parameters and component concentrations, thus providing insights into possible pathological conditions. Conclusion A steady state analysis indicates that negative feedback regulation of phosphatase PTP1B by Akt elicits bistability in insulin-stimulated GLUT4 translocation. The threshold concentration of insulin required for GLUT4 translocation and the corresponding bistable response at different system parameters and component concentrations was compared with reported experimental observations on specific defects in regulation of the system.
The steady-state tokamak program
International Nuclear Information System (INIS)
Politzer, D.A.; Nevins, W.M.
1992-01-01
This paper reports on a steady-state tokamak experiment (STE) needed to develop the technology and physics data base required for construction of a steady-state fusion power demonstration reactor in the early 21st century. The STE will provide an integrated facility for the development and demonstration of steady-state and particle handling, low-activation high-heat-flux components and materials, efficient current drive, and continuous plasma performance in steady-state, with reactor-like plasma conditions under severe conditions of heat and particle bombardment of the wall. The STE facility will also be used to develop operation and control scenarios for ITER
Coincidental match of numerical simulation and physics
Pierre, B.; Gudmundsson, J. S.
2010-08-01
Consequences of rapid pressure transients in pipelines range from increased fatigue to leakages and to complete ruptures of pipeline. Therefore, accurate predictions of rapid pressure transients in pipelines using numerical simulations are critical. State of the art modelling of pressure transient in general, and water hammer in particular include unsteady friction in addition to the steady frictional pressure drop, and numerical simulations rely on the method of characteristics. Comparison of rapid pressure transient calculations by the method of characteristics and a selected high resolution finite volume method highlights issues related to modelling of pressure waves and illustrates that matches between numerical simulations and physics are purely coincidental.
Numerical Model and Experimental Analysis of the Thermal Behavior of Electric Radiant Heating Panels
Directory of Open Access Journals (Sweden)
Giovanni Ferrarini
2018-01-01
Full Text Available Electric radiant heating panels are frequently selected during the design phase of residential and industrial heating systems, especially for retrofit of existing buildings, as an alternative to other common heating systems, such as radiators or air conditioners. The possibility of saving living and working space and the ease of installation are the main advantages of electric radiant solutions. This paper investigates the thermal performance of a typical electric radiant panel. A climatic room was equipped with temperature sensors and heat flow meters to perform a steady state experimental analysis. For the dynamic behavior, a mathematical model was created and compared to a thermographic measurement procedure. The results showed for the steady state an efficiency of energy transformation close to one, while in a transient thermal regime the time constant to reach the steady state condition was slightly faster than the typical ones of hydronic systems.
Thermodynamic analysis and numerical modeling of supercritical injection
Banuti, Daniel
2015-01-01
Although liquid propellant rocket engines are operational and have been studied for decades, cryogenic injection at supercritical pressures is still considered essentially not understood. This thesis intends to approach this problem in three steps: by developing a numerical model for real gas thermodynamics, by extending the present thermodynamic view of supercritical injection, and finally by applying these methods to the analysis of injection. A new numerical real gas thermodynamics mode...
Numerical analysis of the Anderson localization
International Nuclear Information System (INIS)
Markos, P.
2006-01-01
The aim of this paper is to demonstrate, by simple numerical simulations, the main transport properties of disordered electron systems. These systems undergo the metal insulator transition when either Fermi energy crosses the mobility edge or the strength of the disorder increases over critical value. We study how disorder affects the energy spectrum and spatial distribution of electronic eigenstates in the diffusive and insulating regime, as well as in the critical region of the metal-insulator transition. Then, we introduce the transfer matrix and conductance, and we discuss how the quantum character of the electron propagation influences the transport properties of disordered samples. In the weakly disordered systems, the weak localization and anti-localization as well as the universal conductance fluctuation are numerically simulated and discussed. The localization in the one dimensional system is described and interpreted as a purely quantum effect. Statistical properties of the conductance in the critical and localized regimes are demonstrated. Special attention is given to the numerical study of the transport properties of the critical regime and to the numerical verification of the single parameter scaling theory of localization. Numerical data for the critical exponent in the orthogonal models in dimension 2 < d ≤ 5 are compared with theoretical predictions. We argue that the discrepancy between the theory and numerical data is due to the absence of the self-averaging of transmission quantities. This complicates the analytical analysis of the disordered systems. Finally, theoretical methods of description of weakly disordered systems are explained and their possible generalization to the localized regime is discussed. Since we concentrate on the one-electron propagation at zero temperature, no effects of electron-electron interaction and incoherent scattering are discussed in the paper (Author)
Numerical experimentation on convective coolant flow in Ghana ...
African Journals Online (AJOL)
Numerical experiments on one dimensional convective coolant flow during steady state operation of the Ghana Research Reactor-1 (GHARR-I) were performed to determine the thermal hydraulic parameters of temperature, density and flow rate. The computational domain was the reactor vessel, including the reactor core.
International Nuclear Information System (INIS)
Ceballos, M.A.; Car, E.J.; Prato, T.A.; Prato, C.A.; Alvarez, L.M.; Godoy, A.R.
1995-01-01
Determination of the dynamic properties of the reactor building of Atucha II NPP is carried out in order to: i) Obtain valuable information for seismic qualification of the plant, and ii) Assess some procedures for testing and analysis that are used in the process of seismic evaluation of existing nuclear facilities founded on Quaternary soil deposits. Both steady state and impulsive dynamic tests were performed but attention is centered here in tile techniques used to determine natural frequencies and modal damping ratios with impulsive tests. Numerical analyses were performed by means of a 3-D model model of the superstructure together with foundation stiffness coefficients derived in a separate paper from steady state vibration tests, and also from analysis with a 2-D F.E. model of the soil layers capable of approximating the 3-D features of the problem. The computed foundation stiffness coefficients are compared both with those obtained from the tests and from an axisymmetric F.E. model; results indicate that foundation stiffness coefficients calculated with F.E. models with soil parameters given by laboratory tests performed on cored samples are significantly lower than those given by the steady state vibration tests. (author)
Numerical treatment of creep crack growth
International Nuclear Information System (INIS)
Kienzler, R.; Hollstein, T.
1990-06-01
To accomplish the safety analysis and to predict the lifetime of high-termpature components with flaws, several concepts have been proposed to correlate creep-crack initiation and growth with fracture mechanics parameters. The concepts of stress-intensity factor K, reference stress σ ref , line integral C * , and others will be discussed. Among them, the C * -integral concept seems to have the widest range of applicability, if large creep zones develop and steady state creep conditions can be assumed. The numerical evaluation of C * by the virtual crack extension method is described. The methods are demonstrated by two- and three-dimensional finite element simulations including creep crack growth. As for ductile fracture experiments, plane stress and plane strain simulations are bounds to the three-dimensional simulations which agree well with corresponding experiments. (orig.)
DEFF Research Database (Denmark)
Brøns, Morten; Voigt, Lars Peter Køllgaard; Sørensen, Jens Nørkær
1998-01-01
Using a combination of bifurcation theory for two-dimensional dynamical systems and numerical simulations, we systematically determine the possible flow topologies of the steady vortex breakdown in axisymmetric flow in a cylindrical container with rotating end-covers. For fixed values...
Transient productivity index for numerical well test simulations
Energy Technology Data Exchange (ETDEWEB)
Blanc, G.; Ding, D.Y.; Ene, A. [Institut Francais du Petrole, Pau (France)] [and others
1997-08-01
The most difficult aspect of numerical simulation of well tests is the treatment of the Bottom Hole Flowing (BHF) Pressure. In full field simulations, this pressure is derived from the Well-block Pressure (WBP) using a numerical productivity index which accounts for the grid size and permeability, and for the well completion. This productivity index is calculated assuming a pseudo-steady state flow regime in the vicinity of the well and is therefore constant during the well production period. Such a pseudo-steady state assumption is no longer valid for the early time of a well test simulation as long as the pressure perturbation has not reached several grid-blocks around the well. This paper offers two different solutions to this problem: (1) The first one is based on the derivation of a Numerical Transient Productivity Index (NTPI) to be applied to Cartesian grids; (2) The second one is based on the use of a Corrected Transmissibility and Accumulation Term (CTAT) in the flow equation. The representation of the pressure behavior given by both solutions is far more accurate than the conventional one as shown by several validation examples which are presented in the following pages.
Steady flow torques in a servo motor operated rotary directional control valve
International Nuclear Information System (INIS)
Wang, He; Gong, Guofang; Zhou, Hongbin; Wang, Wei
2016-01-01
Highlights: • A novel servo motor operated rotary directional control valve is proposed. • Steady flow torque is a crucial issue that affects rotary valve performance. • Steady flow torque is analyzed on the aspects of theory, simulation and experiment. • Change law of the steady flow torque with spool rotation angle is explored. • Effect of pressure drop and flow rate on the steady flow torque is studied. - Abstract: In this paper, a servo motor operated rotary directional control valve is proposed, and a systematic analysis of steady flow torques in this valve is provided by theoretical calculation, CFD simulation and experimental test. In the analysis, spool rotation angle corresponding to the maximum orifice opening is tagged as 0°. Over a complete change cycle of the orifice, the range of spool rotation angle is symmetric about 0°. The results show that the direction of steady flow torques in this valve is always the direction of orifice closing. The steady flow torques serve as resistances to the spool rotation when the orifice opening increases, while impetuses to the spool rotation when the orifice opening decreases. At a certain pressure drop or flow rate, steady flow torques are approximately equal and opposite when at spool rotation angles which are symmetric about 0°. When the spool rotates from 0°, at a certain pressure drop, their values increase first then decrease with the spool rotation and reach their maximum values at an angle corresponding to about 1/2 of the maximum orifice opening, and at a certain flow rate, their values increase with the spool rotation. The steady flow torques in this valve are the sums of those in the meter-in and meter-out valve chambers. At a certain spool rotation angle, steady flow torques in the meter-in and meter-out valve chambers are approximately proportional to the pressure drop and the second power of the flow rate through the orifice. Theoretical calculation and CFD simulation can be validated by
Numerical analysis of systems of ordinary and stochastic differential equations
Artemiev, S S
1997-01-01
This text deals with numerical analysis of systems of both ordinary and stochastic differential equations. It covers numerical solution problems of the Cauchy problem for stiff ordinary differential equations (ODE) systems by Rosenbrock-type methods (RTMs).
Chaotic and steady state behaviour of a nonlinear controlled gyro subjected to harmonic disturbances
International Nuclear Information System (INIS)
Perez Polo, Manuel F.; Perez Molina, Manuel
2007-01-01
Chaotic and steady state motions of a nonlinear controlled gimbals suspension gyro used to stabilize an external body are studied in this paper. The equations of the gyro without nonlinear control are deduced from the Euler-Lagrange equations by using the nutation theory. The equations of the system show that a cyclic variable appears. Its elimination allows us to find an auxiliary nonlinear system from which it is possible to deduce a nonlinear control law in order to obtain a desired equilibrium point. From the analysis of the nonlinear control law it is possible to show that due to both harmonic disturbances in the platform of the gyro and in the body to stabilize, regular and chaotic motions can appear. The chaotic motion is researched by means of chaos maps, bifurcation diagrams, sensitivity to initial conditions, Lyapunov exponents and Fourier spectrum density. The transition from chaotic to steady state motion by eliminating the harmonic disturbances from the modification of the initial nonlinear control law is also researched. Next, the paper shows how to use the chaotic motion in order to obtain small input signals so that the desired equilibrium state of the gyro can be reached. The developed methodology and its compared performance are evaluated through analytical methods and numerical simulations
Chaotic and steady state behaviour of a nonlinear controlled gyro subjected to harmonic disturbances
Energy Technology Data Exchange (ETDEWEB)
Perez Polo, Manuel F. [Department of Fisica, Ingenieria de Sistemas y Teoria de la Senal, Universidad de Alicante, Escuela Politecnica Superior, Campus de San Vicente, 03071 Alicante (Spain)]. E-mail: manolo@dfists.ua.es; Perez Molina, Manuel [Facultad de Ciencias Matematicas, Universidad Nacional de Educacion a Distancia, UNED, C/Boyero 12-1A, Alicante 03007 (Spain)]. E-mail: ma_perez_m@hotmail.com
2007-07-15
Chaotic and steady state motions of a nonlinear controlled gimbals suspension gyro used to stabilize an external body are studied in this paper. The equations of the gyro without nonlinear control are deduced from the Euler-Lagrange equations by using the nutation theory. The equations of the system show that a cyclic variable appears. Its elimination allows us to find an auxiliary nonlinear system from which it is possible to deduce a nonlinear control law in order to obtain a desired equilibrium point. From the analysis of the nonlinear control law it is possible to show that due to both harmonic disturbances in the platform of the gyro and in the body to stabilize, regular and chaotic motions can appear. The chaotic motion is researched by means of chaos maps, bifurcation diagrams, sensitivity to initial conditions, Lyapunov exponents and Fourier spectrum density. The transition from chaotic to steady state motion by eliminating the harmonic disturbances from the modification of the initial nonlinear control law is also researched. Next, the paper shows how to use the chaotic motion in order to obtain small input signals so that the desired equilibrium state of the gyro can be reached. The developed methodology and its compared performance are evaluated through analytical methods and numerical simulations.
steady state and transient analysis of induction motor driving a pump
African Journals Online (AJOL)
Dr Obe
The importance of using a digital computer in studying the performance of Induction machine under steady .... transformation to that given in equation (7) .... Drive. IEEE Transactions on Industry ... Machinery" McGraw-Hill Book company, New.
Odelouca Dam Construction: Numerical Analysis
Brito, A.; Maranha, J. R.; Caldeira, L.
2012-01-01
Odelouca dam is an embankment dam, with 76 m height, recently constructed in the south of Portugal. It is zoned with a core consisting of colluvial and residual schist soil and with soil-rockfill mixtures making up the shells (weathered schist with a significant fraction of coarse sized particles). This paper presents a numerical analysis of Odelouca Dam`s construction. The material con-stants of the soil model used are determined from a comprehensive testing programme carried out in the C...
Hagsäter, S M; Jensen, T Glasdam; Bruus, H; Kutter, J P
2007-10-01
We show that full-image micro-PIV analysis in combination with images of transient particle motion is a powerful tool for experimental studies of acoustic radiation forces and acoustic streaming in microfluidic chambers under piezo-actuation in the MHz range. The measured steady-state motion of both large 5 microm and small 1 microm particles can be understood in terms of the acoustic eigenmodes or standing ultra-sound waves in the given experimental microsystems. This interpretation is supported by numerical solutions of the corresponding acoustic wave equation.
Development of a steady thermal-hydraulic analysis code for the China Advanced Research Reactor
Institute of Scientific and Technical Information of China (English)
TIAN Wenxi; QIU Suizheng; GUO Yun; SU Guanghui; JIA Dounan; LIU Tiancai; ZHANG Jianwei
2007-01-01
A multi-channel model steady-state thermalhydraulic analysis code was developed for the China Advanced Research Reactor (CARR). By simulating the whole reactor core, the detailed mass flow distribution in the core was obtained. The result shows that structure size plays the most important role in mass flow distribution, and the influence of core power could be neglected under singlephase flow. The temperature field of the fuel element under unsymmetrical cooling condition was also obtained, which is necessary for further study such as stress analysis, etc. Of the fuel element. At the same time, considering the hot channel effect including engineering factor and nuclear factor, calculation of the mean and hot channel was carried out and it is proved that all thermal-hydraulic parameters satisfy the "Safety design regulation of CARR".
DEFF Research Database (Denmark)
Brøns, Morten; Voigt, Lars Peter Kølgaard; Sørensen, Jens Nørkær
1999-01-01
Using a combination of bifurcation theory for two-dimensional dynamical systems and numerical simulations, we systematically determine the possible flow topologies of the steady vortex breakdown in axisymmetric flow in a cylindrical container with rotating end-covers. For fixed values of the ratio...
Ferrofluids: Modeling, numerical analysis, and scientific computation
Tomas, Ignacio
This dissertation presents some developments in the Numerical Analysis of Partial Differential Equations (PDEs) describing the behavior of ferrofluids. The most widely accepted PDE model for ferrofluids is the Micropolar model proposed by R.E. Rosensweig. The Micropolar Navier-Stokes Equations (MNSE) is a subsystem of PDEs within the Rosensweig model. Being a simplified version of the much bigger system of PDEs proposed by Rosensweig, the MNSE are a natural starting point of this thesis. The MNSE couple linear velocity u, angular velocity w, and pressure p. We propose and analyze a first-order semi-implicit fully-discrete scheme for the MNSE, which decouples the computation of the linear and angular velocities, is unconditionally stable and delivers optimal convergence rates under assumptions analogous to those used for the Navier-Stokes equations. Moving onto the much more complex Rosensweig's model, we provide a definition (approximation) for the effective magnetizing field h, and explain the assumptions behind this definition. Unlike previous definitions available in the literature, this new definition is able to accommodate the effect of external magnetic fields. Using this definition we setup the system of PDEs coupling linear velocity u, pressure p, angular velocity w, magnetization m, and magnetic potential ϕ We show that this system is energy-stable and devise a numerical scheme that mimics the same stability property. We prove that solutions of the numerical scheme always exist and, under certain simplifying assumptions, that the discrete solutions converge. A notable outcome of the analysis of the numerical scheme for the Rosensweig's model is the choice of finite element spaces that allow the construction of an energy-stable scheme. Finally, with the lessons learned from Rosensweig's model, we develop a diffuse-interface model describing the behavior of two-phase ferrofluid flows and present an energy-stable numerical scheme for this model. For a
Numerical Limit Analysis of Precast Concrete Structures
DEFF Research Database (Denmark)
Herfelt, Morten Andersen; Poulsen, Peter Noe; Hoang, Linh Cao
2016-01-01
; the framework is based on the theory of rigid-plasticity, and the resulting mathematical optimisation problem can be solved efficiently using modern algorithms. This paper gives a brief introduction to convex optimisation and numerical limit analysis. The mathematical formulation of lower bound load...
Numerical analysis of thermoluminescence glow curves
International Nuclear Information System (INIS)
Gomez Ros, J. M.; Delgado, A.
1989-01-01
This report presents a method for the numerical analysis of complex thermoluminescence glow curves resolving the individual glow peak components. The method employs first order kinetics analytical expressions and is based In a Marquart-Levenberg minimization procedure. A simplified version of this method for thermoluminescence dosimetry (TLD) is also described and specifically developed to operate whit Lithium Fluoride TLD-100. (Author). 36 refs
International Nuclear Information System (INIS)
Boulaich, Y.; Nacir, B.; El Bardouni, T.; Zoubair, M.; El Bakkari, B.; Merroun, O.; El Younoussi, C.; Htet, A.; Boukhal, H.; Chakir, E.
2011-01-01
Research highlights: → The COOLOD/N2 and PARET/ANL codes were used for a steady-state thermal-hydraulic and safety analysis of the 2 MW TRIGA MARK II reactor located at the Nuclear Studies Center of Maamora (CENM), Morocco. → The main objective of this study is to ensure the safety margins of different safety related parameters by steady-state calculations at full power level (2 MW). → The most important conclusion is that all obtained values of DNBR, fuel center and surface temperature, cladding surface temperature and coolant temperature across the hottest channel are largely far to compromise safety of the reactor. - Abstract: The COOLOD/N2 and PARET/ANL codes were used for a steady-state thermal-hydraulic and safety analysis of the 2 MW TRIGA MARK II reactor located at the Nuclear Studies Center of Maamora (CENM), Morocco. In order to validate our PARET/ANL and COOLOD-N2 models, the fuel center temperature as function of core power was calculated and compared with the corresponding experimental values. The comparison indicates that the calculated values are in satisfactory agreement with the measurement. The main objective of this study is to ensure the safety margins of different safety related parameters by steady-state calculations at full power level (2 MW). Therefore, we have calculated the departure from nucleate boiling ratio (DNBR), fuel center and surface temperature, cladding surface temperature and coolant temperature profiles across the hottest channel. The most important conclusion is that all obtained values are largely far to compromise safety of the reactor.
Present status of numerical analysis on transient two-phase flow
International Nuclear Information System (INIS)
Akimoto, Masayuki; Hirano, Masashi; Nariai, Hideki.
1987-01-01
The Special Committee for Numerical Analysis of Thermal Flow has recently been established under the Japan Atomic Energy Association. Here, some methods currently used for numerical analysis of transient two-phase flow are described citing some information given in the first report of the above-mentioned committee. Many analytical models for transient two-phase flow have been proposed, each of which is designed to describe a flow by using differential equations associated with conservation of mass, momentum and energy in a continuous two-phase flow system together with constructive equations that represent transportation of mass, momentum and energy though a gas-liquid interface or between a liquid flow and the channel wall. The author has developed an analysis code, called MINCS, that serves for systematic examination of conservation equation and constructive equations for two-phase flow models. A one-dimensional, non-equilibrium two-liquid flow model that is used as the basic model for the code is described. Actual procedures for numerical analysis is shown and some problems concerning transient two-phase analysis are described. (Nogami, K.)
Directory of Open Access Journals (Sweden)
D. Pumo
2008-02-01
Full Text Available The probabilistic description of soil moisture dynamics is a relatively new topic in hydrology. The most common ecohydrological models start from a stochastic differential equation describing the soil water balance, where the unknown quantity, the soil moisture, depends both on spaces and time. Most of the solutions existing in literature are obtained in a probabilistic framework and under steady-state condition; even if this last condition allows the analytical handling of the problem, it has considerably simplified the same problem by subtracting generalities from it.
The steady-state hypothesis, appears perfectly applicable in arid and semiarid climatic areas like those of African's or middle American's savannas, but it seems to be no more valid in areas with Mediterranean climate, where, notoriously, the wet season foregoes the growing season, recharging water into the soil. This moisture stored at the beginning of the growing season (known as soil moisture initial condition has a great importance, especially for deep-rooted vegetation, by enabling survival in absence of rainfalls during the growing season and, however, keeping the water stress low during the first period of the same season.
The aim of this paper is to analyze the soil moisture dynamics using a simple non-steady numerical ecohydrological model. The numerical model here proposed is able to reproduce soil moisture probability density function, obtained analytically in previous studies for different climates and soils in steady-state conditions; consequently it can be used to compute both the soil moisture time-profile and the vegetation static water stress time-profile in non-steady conditions.
Here the differences between the steady-analytical and the non-steady numerical probability density functions are analyzed, showing how the proposed numerical model is able to capture the effects of winter recharge on the soil moisture. The dynamic
A method of piecewise-smooth numerical branching
Czech Academy of Sciences Publication Activity Database
Ligurský, Tomáš; Renard, Y.
2017-01-01
Roč. 97, č. 7 (2017), s. 815-827 ISSN 1521-4001 R&D Projects: GA MŠk LQ1602 Institutional support: RVO:68145535 Keywords : numerical branching * piecewise smooth * steady-state problem * contact problem * Coulomb friction Subject RIV: BA - General Mathematics OBOR OECD: Applied mathematics http://onlinelibrary.wiley.com/doi/10.1002/zamm.201600219/epdf
Numerical Research on Effects of Splitter Blades to the Influence of Pump as Turbine
Directory of Open Access Journals (Sweden)
Yang Sun-Sheng
2012-01-01
Full Text Available Centrifugal pumps can be operated in reverse as small hydropower recovery turbines and are cheaper than bespoke turbines due to their ease of manufacture. Splitter blades technique is one of the techniques used in flow field optimization and performance enhancement of rotating machinery. To understand the effects of splitter blades to the steady and unsteady influence of PAT, numerical research was performed. 3D Navier-Stokes solver CFX was used in the performance prediction and analysis of PAT’s performance. Results show that splitter blades have a positive impact on PAT’s performance. With the increase of splitter blades, its required pressure head is dropped and its efficiency is increased. Unsteady pressure field analysis and comparison show that the unsteady pressure field within PAT is improved when splitter blades are added to impeller flow passage. To verify the accuracy of numerical prediction methods, an open PAT test rig was built at Jiangsu University. The PAT was manufactured and tested. Comparison between experimental and numerical results shows that the discrepancy between numerical and experimental results is acceptable. CFD can be used in the performance prediction and optimization of PAT.
Numerical Analysis of Deflections of Multi-Layered Beams
Biliński, Tadeusz; Socha, Tomasz
2015-03-01
The paper concerns the rheological bending problem of wooden beams reinforced with embedded composite bars. A theoretical model of the behaviour of a multi-layered beam is presented. The component materials of this beam are described with equations for the linear viscoelastic five-parameter rheological model. Two numerical analysis methods for the long-term response of wood structures are presented. The first method has been developed with SCILAB software. The second one has been developed with the finite element calculation software ABAQUS and user subroutine UMAT. Laboratory investigations were conducted on sample beams of natural dimensions in order to validate the proposed theoretical model and verify numerical simulations. Good agreement between experimental measurements and numerical results is observed.
The Markov process admits a consistent steady-state thermodynamic formalism
Peng, Liangrong; Zhu, Yi; Hong, Liu
2018-01-01
The search for a unified formulation for describing various non-equilibrium processes is a central task of modern non-equilibrium thermodynamics. In this paper, a novel steady-state thermodynamic formalism was established for general Markov processes described by the Chapman-Kolmogorov equation. Furthermore, corresponding formalisms of steady-state thermodynamics for the master equation and Fokker-Planck equation could be rigorously derived in mathematics. To be concrete, we proved that (1) in the limit of continuous time, the steady-state thermodynamic formalism for the Chapman-Kolmogorov equation fully agrees with that for the master equation; (2) a similar one-to-one correspondence could be established rigorously between the master equation and Fokker-Planck equation in the limit of large system size; (3) when a Markov process is restrained to one-step jump, the steady-state thermodynamic formalism for the Fokker-Planck equation with discrete state variables also goes to that for master equations, as the discretization step gets smaller and smaller. Our analysis indicated that general Markov processes admit a unified and self-consistent non-equilibrium steady-state thermodynamic formalism, regardless of underlying detailed models.
Computational issues of solving the 1D steady gradually varied flow equation
Directory of Open Access Journals (Sweden)
Artichowicz Wojciech
2014-09-01
Full Text Available In this paper a problem of multiple solutions of steady gradually varied flow equation in the form of the ordinary differential energy equation is discussed from the viewpoint of its numerical solution. Using the Lipschitz theorem dealing with the uniqueness of solution of an initial value problem for the ordinary differential equation it was shown that the steady gradually varied flow equation can have more than one solution. This fact implies that the nonlinear algebraic equation approximating the ordinary differential energy equation, which additionally coincides with the wellknown standard step method usually applied for computing of the flow profile, can have variable number of roots. Consequently, more than one alternative solution corresponding to the same initial condition can be provided. Using this property it is possible to compute the water flow profile passing through the critical stage.
Numerical Studies of a Fluidic Diverter for Flow Control
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.
Numerical investigation of the recruitment process in open marine population models
International Nuclear Information System (INIS)
Angulo, O; López-Marcos, J C; López-Marcos, M A; Martínez-Rodríguez, J
2011-01-01
The changes in the dynamics, produced by the recruitment process in an open marine population model, are investigated from a numerical point of view. The numerical method considered, based on the representation of the solution along the characteristic lines, approximates properly the steady states of the model, and is used to analyze the asymptotic behavior of the solutions of the model
Dadashzadeh, N.; Duzgun, H. S. B.; Yesiloglu-Gultekin, N.
2017-08-01
While advanced numerical techniques in slope stability analysis are successfully used in deterministic studies, they have so far found limited use in probabilistic analyses due to their high computation cost. The first-order reliability method (FORM) is one of the most efficient probabilistic techniques to perform probabilistic stability analysis by considering the associated uncertainties in the analysis parameters. However, it is not possible to directly use FORM in numerical slope stability evaluations as it requires definition of a limit state performance function. In this study, an integrated methodology for probabilistic numerical modeling of rock slope stability is proposed. The methodology is based on response surface method, where FORM is used to develop an explicit performance function from the results of numerical simulations. The implementation of the proposed methodology is performed by considering a large potential rock wedge in Sumela Monastery, Turkey. The accuracy of the developed performance function to truly represent the limit state surface is evaluated by monitoring the slope behavior. The calculated probability of failure is compared with Monte Carlo simulation (MCS) method. The proposed methodology is found to be 72% more efficient than MCS, while the accuracy is decreased with an error of 24%.
Lepeytre, Fanny; Lavoie, Pierre-Luc; Troyanov, Stéphan; Madore, François; Agharazii, Mohsen; Goupil, Rémi
2018-03-01
Whether the cardiovascular risk attributed to elevated uric acid levels may be explained by changes in central and peripheral pulsatile and/or steady blood pressure (BP) components remains controversial. In a cross-sectional analysis of normotensive and untreated hypertensive participants of the CARTaGENE populational cohort, we examined the relationship between uric acid, and both pulsatile and steady components of peripheral and central BP, using sex-stratified linear regressions. Of the 20 004 participants, 10 161 individuals without antihypertensive or uric acid-lowering drugs had valid pulse wave analysis and serum uric acid levels. In multivariate analysis, pulsatile components of BP were not associated with uric acid levels, whereas steady components [mean BP (MBP), peripheral and central DBP] were all associated with higher levels of uric acid levels in women and men (all P uric acid levels but not for MBP-adjusted cSBP. Peripheral and cSBP, which are aggregate measures of pulsatile and steady BP, were also associated with uric acid levels in women (β = 0.063 and 0.072, respectively, both P uric acid levels. Serum uric acid levels appear to be associated with both central and peripheral steady but not pulsatile BP, regardless of sex.
Pereira, Félix Monteiro; Oliveira, Samuel Conceição
2016-11-01
In this article, the occurrence of dead core in catalytic particles containing immobilized enzymes is analyzed for the Michaelis-Menten kinetics. An assessment of numerical methods is performed to solve the boundary value problem generated by the mathematical modeling of diffusion and reaction processes under steady state and isothermal conditions. Two classes of numerical methods were employed: shooting and collocation. The shooting method used the ode function from Scilab software. The collocation methods included: that implemented by the bvode function of Scilab, the orthogonal collocation, and the orthogonal collocation on finite elements. The methods were validated for simplified forms of the Michaelis-Menten equation (zero-order and first-order kinetics), for which analytical solutions are available. Among the methods covered in this article, the orthogonal collocation on finite elements proved to be the most robust and efficient method to solve the boundary value problem concerning Michaelis-Menten kinetics. For this enzyme kinetics, it was found that the dead core can occur when verified certain conditions of diffusion-reaction within the catalytic particle. The application of the concepts and methods presented in this study will allow for a more generalized analysis and more accurate designs of heterogeneous enzymatic reactors.
Description of a stable scheme for steady-state coupled Monte Carlo–thermal–hydraulic calculations
International Nuclear Information System (INIS)
Dufek, Jan; Eduard Hoogenboom, J.
2014-01-01
Highlights: • A stable coupling scheme for steady-state MC–TH calculations is described. • The coupling scheme is based on the stochastic approximation method. • The neutron flux (or power) distribution is relaxed using a variable step-size. - Abstract: We provide a detailed description of a numerically stable and efficient coupling scheme for steady-state Monte Carlo neutronic calculations with thermal–hydraulic feedback. While we have previously derived and published the stochastic approximation based method for coupling the Monte Carlo criticality and thermal–hydraulic calculations, its possible implementation has not been described in a step-by-step manner. As the simple description of the coupling scheme was repeatedly requested from us, we have decided to make it available via this note
Active ideal sedimentation: exact two-dimensional steady states.
Hermann, Sophie; Schmidt, Matthias
2018-02-28
We consider an ideal gas of active Brownian particles that undergo self-propelled motion and both translational and rotational diffusion under the influence of gravity. We solve analytically the corresponding Smoluchowski equation in two space dimensions for steady states. The resulting one-body density is given as a series, where each term is a product of an orientation-dependent Mathieu function and a height-dependent exponential. A lower hard wall is implemented as a no-flux boundary condition. Numerical evaluation of the suitably truncated analytical solution shows the formation of two different spatial regimes upon increasing Peclet number. These regimes differ in their mean particle orientation and in their variation of the orientation-averaged density with height.
Numerical Analysis of Deflections of Multi-Layered Beams
Directory of Open Access Journals (Sweden)
Biliński Tadeusz
2015-03-01
Full Text Available The paper concerns the rheological bending problem of wooden beams reinforced with embedded composite bars. A theoretical model of the behaviour of a multi-layered beam is presented. The component materials of this beam are described with equations for the linear viscoelastic five-parameter rheological model. Two numerical analysis methods for the long-term response of wood structures are presented. The first method has been developed with SCILAB software. The second one has been developed with the finite element calculation software ABAQUS and user subroutine UMAT. Laboratory investigations were conducted on sample beams of natural dimensions in order to validate the proposed theoretical model and verify numerical simulations. Good agreement between experimental measurements and numerical results is observed.
International Nuclear Information System (INIS)
Yoshida, Taiki
2016-01-01
There are continuum and discontinuum analyses in the evaluation of seismic stability of surrounding slope in nuclear power plant facility. However, we cannot rationally evaluate such seismic stability due to excessive conservative margin of the results by each analysis. If we can simulate the behavior from small to large deformation by hybridizing them, we can contribute not only to the rationalization of the slope stability evaluation but also the enhancement of evaluation precision in the numerical analysis. In this review, the previous numerical analyses and application cases of them in earthquake geotechnical engineering were classified into three categories, that is, continuum analysis, discontinuum one and the hybridizing process to identify their research themes. The present review has revealed that the research themes are the standardization of condition for conversion, construction of the technique to determine parameters related to conversion and the reasonable physical property set of DEM(Distinct Element Method) after conversion. Our future work will be development of a numerical analysis code hybridizing continuum and discontinuum analyses based on the identified research themes. (author)
computational study of Couette flow between parallel plates for steady and unsteady cases
International Nuclear Information System (INIS)
Rihan, Y.
2008-01-01
Couette flow between parallel plates is a classical problem that has important applications in various industrial processing. In this investigation an analytical solution was obtained to predict the steady and unsteady Couette flow between parallel plates. One of the plates was stationary and the other plate moved with constant velocity. The governing partial differential equations were solved numerically using Crank-Nicolson implicit method to represent the flow behavior of the fluid
Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow
International Nuclear Information System (INIS)
Yu Tsvelodub, O
2016-01-01
The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. Weakly nonlinear steady-state traveling solutions of the equation with wave numbers in a vicinity of neutral wave numbers are constructed analytically. The nature of the wave branching from the undisturbed solution is investigated. Steady-state traveling solutions, whose wave numbers within the instability area are far from neutral wave numbers, are found numerically. (paper)
Analysis of steady-state ductile crack growth
DEFF Research Database (Denmark)
Niordson, Christian
1999-01-01
The fracture strength under quasi-static steady-state crack growth in an elastic-plastic material joined by a laser weld is analyzed. Laser welding gives high mismatch between the yield stress within the weld and the yield stress in the base material. This is due to the fast termic cycle, which...... the finite element mesh remains fixed relative to the tip of the growing crack. Fracture is modelled using two different local crack growth criteria. One is a crack opening displacement criterion, while the other is a model in which a cohesive zone is imposed in front of the crack tip along the fracture zone....... Both models predict that in general a thinner laser weld gives higher interface strength. Furthermore, both fracture criteria show, that the preferred path of the crack is close outside the weld material; a phenomenon also observed in experiments....
Morphological instability during steady electrodeposition at overlimiting currents
DEFF Research Database (Denmark)
Nielsen, Christoffer Peder; Bruus, Henrik
2015-01-01
We present a linear stability analysis of a planar metal electrode during steady electrodeposition. We extend the previous work of Sundstrom and Bark by accounting for the extended space-charge density, which develops at the cathode once the applied voltage exceeds a few thermal voltages...
Natural equilibria in steady-state neutron diffusion with temperature feedback
International Nuclear Information System (INIS)
Pounders, J. M.; Ingram, R.
2013-01-01
The critical diffusion equation with feedback is investigated within the context of steady-state multiphysics. It is proposed that for critical configurations there is no need to include the multiplication factor k in the formulation of the diffusion equation. This is notable because exclusion of k from the coupled system of equations precludes the mathematically tenuous notion of a nonlinear eigenvalue problem. On the other hand, it is shown that if the factor k is retained in the diffusion equation, as is currently common practice, then the resulting problem is equivalent to the constrained minimization of a functional representing the critical equilibrium of neutron and temperature distributions. The unconstrained solution corresponding to k = 1 represents the natural equilibrium of a critical system at steady-state. Computational methods for solving the constrained problem (with k) are briefly reviewed from the literature and a method for the unconstrained problem (without k) is outlined. A numerical example is studied to examine the effects of the constraint in the nonlinear system. (authors)
Adaptively locating unknown steady states: Formalism and basin of attraction
International Nuclear Information System (INIS)
Wu, Yu; Lin, Wei
2011-01-01
The adaptive technique, which includes both dynamical estimators and coupling gains, has been recently verified to be practical for locating the unknown steady states numerically. This Letter, in the light of the center manifold theory for dynamical systems and the matrix spectrum principle, establishes an analytical formalism of this adaptive technique and reveals a connection between this technique and the original adaptive controller which includes only the dynamical estimator. More interestingly, in study of the well-known Lorenz system, the selections of the estimator parameters and initial values are found to be crucial to the successful application of the adaptive technique. Some Milnor-like basins of attraction with fractal structures are found quantitatively. All the results obtained in the Letter can be further extended to more general dynamical systems of higher dimensions. -- Highlights: → Establishing a new and rigorous formalism for the adaptive stabilization technique. → Showing a close connection between the adaptive technique and the original controller. → Providing feasible algorithms for simultaneous stabilization of multiple steady states. → Finding Milnor-like basins of attraction with fractal structures in adaptive control.
Numerical analysis for prediction of fatigue crack opening level
International Nuclear Information System (INIS)
Choi, Hyeon Chang
2004-01-01
Finite Element Analysis (FEA) is the most popular numerical method to simulate plasticity-induced fatigue crack closure and can predict fatigue crack closure behavior. Finite element analysis under plane stress state using 4-node isoparametric elements is performed to investigate the detailed closure behavior of fatigue cracks and the numerical results are compared with experimental results. The mesh of constant size elements on the crack surface can not correctly predict the opening level for fatigue crack as shown in the previous works. The crack opening behavior for the size mesh with a linear change shows almost flat stress level after a crack tip has passed by the monotonic plastic zone. The prediction of crack opening level presents a good agreement with published experimental data regardless of stress ratios, which are using the mesh of the elements that are in proportion to the reversed plastic zone size considering the opening stress intensity factors. Numerical interpolation results of finite element analysis can precisely predict the crack opening level. This method shows a good agreement with the experimental data regardless of the stress ratios and kinds of materials
Java technology for implementing efficient numerical analysis in intranet
International Nuclear Information System (INIS)
Song, Hee Yong; Ko, Sung Ho
2001-01-01
This paper introduces some useful Java technologies for utilizing the internet in numerical analysis, and suggests one architecture performing efficient numerical analysis in the intranet by using them. The present work has verified it's possibility by implementing some parts of this architecture with two easy examples. One is based on Servlet-Applet communication, JDBC and swing. The other is adding multi-threads, file transfer and Java remote method invocation to the former. Through this work it has been intended to make the base for the later advanced and practical research that will include efficiency estimates of this architecture and deal with advanced load balancing
Steady State Dynamic Operating Behavior of Universal Motor
Directory of Open Access Journals (Sweden)
Muhammad Khan Burdi
2015-01-01
Full Text Available A detailed investigation of the universal motor is developed and used for various dynamic steady state and transient operating conditions of loads. In the investigation, output torque, motor speed, input current, input/output power and efficiency are computed, compared and analyzed for different loads. While this paper discusses the steady-state behavior of the universal motor, another companion paper, ?Transient dynamic behavior of universal motor?, will discuss its transient behavior in detail. A non-linear generalized electric machine model of the motor is considered for the analysis. This study was essential to investigate effect of output load on input current, power, speed and efficiency of the motor during operations. Previously such investigation is not known
Numerical analysis of rapid drawdown: Applications in real cases
Directory of Open Access Journals (Sweden)
Eduardo E. Alonso
2016-07-01
Full Text Available In this study, rapid drawdown scenarios were analyzed by means of numerical examples as well as modeling of real cases with in situ measurements. The aim of the study was to evaluate different approaches available for calculating pore water pressure distributions during and after a drawdown. To do that, a single slope subjected to a drawdown was first analyzed under different calculation alternatives, and numerical results were discussed. Simple methods, such as undrained analysis and pure flow analysis, implicitly assuming a rigid soil skeleton, lead to significant errors in pore water pressure distributions when compared with coupled flow-deformation analysis. A similar analysis was performed for the upstream slope of the Glen Shira Dam, Scotland, and numerical results were compared with field measurements during a controlled drawdown. Field records indicate that classical undrained calculations are conservative but unrealistic. Then, a recent case of a major landslide triggered by a rapid drawdown in a reservoir was interpreted. A key aspect of the case was the correct characterization of permeability of a representative soil profile. This was achieved by combining laboratory test results and a back analysis of pore water pressure time records during a period of reservoir water level fluctuations. The results highlight the difficulty of predicting whether the pore water pressure is overestimated or underestimated when using simplified approaches, and it is concluded that predicting the pore water pressure distribution in a slope after a rapid drawdown requires a coupled flow-deformation analysis in saturated and unsaturated porous media.
Numerical analysis of modified Central Solenoid insert design
Energy Technology Data Exchange (ETDEWEB)
Khodak, Andrei, E-mail: akhodak@pppl.gov [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Martovetsky, Nicolai; Smirnov, Aleksandre [Oak Ridge National Laboratory, Oak Ridge, TN (United States); Titus, Peter [Princeton Plasma Physics Laboratory, Princeton, NJ (United States)
2015-10-15
Highlights: • Modified design of coil for testing ITER superconducting cable is presented. • Numerical analysis allowed design verification. • Three-dimensional current sharing temperature distributions are obtained from the results. - Abstract: The United States ITER Project Office (USIPO) is responsible for fabrication of the Central Solenoid (CS) for ITER project. The ITER machine is currently under construction by seven parties in Cadarache, France. The CS Insert (CSI) project should provide a verification of the conductor performance in relevant conditions of temperature, field, currents and mechanical strain. The US IPO designed the CSI that will be tested at the Central Solenoid Model Coil (CSMC) Test Facility at JAEA, Naka. To validate the modified design three-dimensional numerical simulations were performed using coupled solver for simultaneous structural, thermal and electromagnetic analysis. Thermal and electromagnetic simulations supported structural calculations providing necessary loads and strains. According to current analysis design of the modified coil satisfies ITER magnet structural design criteria for the following conditions: (1) room temperature, no current, (2) temperature 4 K, no current, (3) temperature 4 K, current 60 kA direct charge, and (4) temperature 4 K, current 60 kA reverse charge. Fatigue life assessment analysis is performed for the alternating conditions of: temperature 4 K, no current, and temperature 4 K, current 45 kA direct charge. Results of fatigue analysis show that parts of the coil assembly can be qualified for up to 1 million cycles. Distributions of the Current Sharing Temperature (TCS) in the superconductor were obtained from numerical results using parameterization of the critical surface in the form similar to that proposed for ITER. Special ADPL scripts were developed for ANSYS allowing one-dimensional representation of TCS along the cable, as well as three-dimensional fields of TCS in superconductor
Coupled-Double-Quantum-Dot Environmental Information Engines: A Numerical Analysis
Tanabe, Katsuaki
2016-06-01
We conduct numerical simulations for an autonomous information engine comprising a set of coupled double quantum dots using a simple model. The steady-state entropy production rate in each component, heat and electron transfer rates are calculated via the probability distribution of the four electronic states from the master transition-rate equations. We define an information-engine efficiency based on the entropy change of the reservoir, implicating power generators that employ the environmental order as a new energy resource. We acquire device-design principles, toward the realization of corresponding practical energy converters, including that (1) higher energy levels of the detector-side reservoir than those of the detector dot provide significantly higher work production rates by faster states' circulation, (2) the efficiency is strongly dependent on the relative temperatures of the detector and system sides and becomes high in a particular Coulomb-interaction strength region between the quantum dots, and (3) the efficiency depends little on the system dot's energy level relative to its reservoir but largely on the antisymmetric relative amplitudes of the electronic tunneling rates.
Einstein's steady-state theory: an abandoned model of the cosmos
O'Raifeartaigh, Cormac; McCann, Brendan; Nahm, Werner; Mitton, Simon
2014-09-01
We present a translation and analysis of an unpublished manuscript by Albert Einstein in which he attempted to construct a `steady-state' model of the universe. The manuscript, which appears to have been written in early 1931, demonstrates that Einstein once explored a cosmic model in which the mean density of matter in an expanding universe is maintained constant by the continuous formation of matter from empty space. This model is very different to previously known Einsteinian models of the cosmos (both static and dynamic) but anticipates the later steady-state cosmology of Hoyle, Bondi and Gold in some ways. We find that Einstein's steady-state model contains a fundamental flaw and suggest that it was abandoned for this reason. We also suggest that he declined to explore a more sophisticated version because he found such theories rather contrived. The manuscript is of historical interest because it reveals that Einstein debated between steady-state and evolving models of the cosmos decades before a similar debate took place in the cosmological community.
Numerical and RAPD Analysis of Eight Cowpea Genotypes from ...
African Journals Online (AJOL)
Hence, numerical tools such as single linkage cluster analysis (SLCA) and principal component analysis (PCA) have been used to determine the extent of variability. This study was conducted to determine the performance, character contribution as well as variation pattern in eight cowpea genotypes collected in Nigeria.
Steady and transient states of a two-phase counter current flow
International Nuclear Information System (INIS)
Siebert, S.
1984-06-01
The aim of this work is to estimate the efficiency of the counter current exchange between a heavy dispersed phase and a continous light phase in a pulse perforated plate column. From an experimental point, hydraulic measurements (retention ratio, droplet size) and residence time measurements (radioactive tracers). The model will be so applied to the calculation of retention ratios in steady conditions then of tracer concentrations in transient conditions. From a numerical point of view a fixed point type iteration then a method Runge Kutta are then adapted [fr
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...
Energy Technology Data Exchange (ETDEWEB)
Tipireddy, R.; Stinis, P.; Tartakovsky, A. M.
2017-12-01
We present a novel approach for solving steady-state stochastic partial differential equations (PDEs) with high-dimensional random parameter space. The proposed approach combines spatial domain decomposition with basis adaptation for each subdomain. The basis adaptation is used to address the curse of dimensionality by constructing an accurate low-dimensional representation of the stochastic PDE solution (probability density function and/or its leading statistical moments) in each subdomain. Restricting the basis adaptation to a specific subdomain affords finding a locally accurate solution. Then, the solutions from all of the subdomains are stitched together to provide a global solution. We support our construction with numerical experiments for a steady-state diffusion equation with a random spatially dependent coefficient. Our results show that highly accurate global solutions can be obtained with significantly reduced computational costs.
Steady state flow analysis of two-phase natural circulation in multiple parallel channel loop
International Nuclear Information System (INIS)
Bhusare, V.H.; Bagul, R.K.; Joshi, J.B.; Nayak, A.K.; Kannan, Umasankari; Pilkhwal, D.S.; Vijayan, P.K.
2016-01-01
Highlights: • Liquid circulation velocity increases with increasing superficial gas velocity. • Total two-phase pressure drop decreases with increasing superficial gas velocity. • Channels with larger driving force have maximum circulation velocities. • Good agreement between experimental and model predictions. - Abstract: In this work, steady state flow analysis has been carried out experimentally in order to estimate the liquid circulation velocities and two-phase pressure drop in air–water multichannel circulating loop. Experiments were performed in 15 channel circulating loop. Single phase and two-phase pressure drops in the channels have been measured experimentally and have been compared with theoretical model of Joshi et al. (1990). Experimental measurements show good agreement with model.
Kostoglou, M.; Karapantsios, T. D.; Buffone, C.; Glushchuk, A.; Iorio, C.
2016-10-01
The present work attempts to model the case of combined gravitational and capillary motion of condensate for an axisymmetric fin under steady and transient fin operation conditions. The focus here is to examine the structure of the mathematical problem and to develop suitable numerical techniques rather than yield information on the macroscopic condensate flow rate and fin efficiency. The problem is formulated starting from general conditions and is simplified step by step by introducing corresponding assumptions. The particular fin shape of a paraboloid from revolution is chosen and the equations are properly non-dimensionalized. A vast reduction of the number of problem parameters is achieved in this way. The cases of isothermal fin, steady state operation and dynamic operation are treated separately using specialized numerical solution techniques developed for each case in order to improve computational efficiency and accuracy. Typical results of fin temperature and condensate film thickness are presented and discussed.
Energy Technology Data Exchange (ETDEWEB)
Kim, Jhin Wung; Bae, Dae Suk; Kang, Chul Hyung; Choi, Jong Won [Korea Atomic Energy Research Institute, Taejeon (Korea)
2002-02-01
The objective of the present study is to understand the long term (500 years) thermo-hydro-mechanical interaction behavior of the 500 m depth underground radwaste repository in the saturated, discontinuous granitic rock mass using a steady state flow algorithm. The numerical model includes a saturated granitic rock mass with joints around the repository and a 45 .deg. C fault passing through the tunnel roof-wall intersection, and a canister with PWR spent fuels surrounded by the compacted bentonite and mixed-bentonite. Barton-Bandis joint constitutive model from the UDEC code is used for the joints. For the hydraulic analysis, a steady state flow algorithm is used for the groundwater flow through the rock joints. For the thermal analysis, heat transfer is modeled as isotropic conduction and heat decays exponentially with time. The results show that the variations of the hydraulic aperture, hydraulic conductivity, normal stress, normal displacements, and shear displacements of the joints are high in the vicinity of the repository and stay fairly constant on the region away from the repository. 14 refs., 15 figs., 11 tabs. (Author)
The steady part of the secular variation of the Earth's magnetic field
Bloxham, Jeremy
1992-01-01
The secular variation of the Earth's magnetic field results from the effects of magnetic induction in the fluid outer core and from the effects of magnetic diffusion in the core and the mantle. Adequate observations to map the magnetic field at the core-mantle boundary extend back over three centuries, providing a model of the secular variation at the core-mantle boundary. Here we consider how best to analyze this time-dependent part of the field. To calculate steady core flow over long time periods, we introduce an adaptation of our earlier method of calculating the flow in order to achieve greater numerical stability. We perform this procedure for the periods 1840-1990 and 1690-1840 and find that well over 90 percent of the variance of the time-dependent field can be explained by simple steady core flow. The core flows obtained for the two intervals are broadly similar to each other and to flows determined over much shorter recent intervals.
The analysis of the annular fuel performance in steady state condition by using AFPAC code
International Nuclear Information System (INIS)
He Xiaojun; Ji Songtao; Zhang Yingchao
2012-01-01
The fuel performance code AFPAC v1.0 is used to analyze annular fuel's behavior under steady state conditions, including neutronics, thermal hydraulic, rod deformation, fission gas release and rod internal pressure. The calculation results show that: 1) Annular fuel has a good steady irradiation performance at 150% power level as current LWRs' with burnup up to 50 GWd/t, and all parameters, such as temperature, rod internal pressure and rod deformation, are meet the rod design criteria for current fuel of PWRs: 2) Compared to the solid fuel under the same irradiation condition. annular fuel has lower temperature, smaller deformation, lower fission gas release and lower pressure at EOL. From the point of view of steady irradiation performance, the safety of reactors can significantly improved by u sing the annular fuel. (authors)
Sensitivity analysis of numerical results of one- and two-dimensional advection-diffusion problems
International Nuclear Information System (INIS)
Motoyama, Yasunori; Tanaka, Nobuatsu
2005-01-01
Numerical simulation has been playing an increasingly important role in the fields of science and engineering. However, every numerical result contains errors such as modeling, truncation, and computing errors, and the magnitude of the errors that are quantitatively contained in the results is unknown. This situation causes a large design margin in designing by analyses and prevents further cost reduction by optimizing design. To overcome this situation, we developed a new method to numerically analyze the quantitative error of a numerical solution by using the sensitivity analysis method and modified equation approach. If a reference case of typical parameters is calculated once by this method, then no additional calculation is required to estimate the results of other numerical parameters such as those of parameters with higher resolutions. Furthermore, we can predict the exact solution from the sensitivity analysis results and can quantitatively evaluate the error of numerical solutions. Since the method incorporates the features of the conventional sensitivity analysis method, it can evaluate the effect of the modeling error as well as the truncation error. In this study, we confirm the effectiveness of the method through some numerical benchmark problems of one- and two-dimensional advection-diffusion problems. (author)
Maharani, S.; Suprapto, E.
2018-03-01
Critical thinking is very important in Mathematics; it can make student more understanding mathematics concept. Critical thinking is also needed in numerical analysis. The Numerical analysis's book is not yet including critical thinking in them. This research aims to develop group investigation-based book on numerical analysis to increase critical thinking student’s ability, to know the quality of the group investigation-based book on numerical analysis is valid, practical, and effective. The research method is Research and Development (R&D) with the subject are 30 student college department of Mathematics education at Universitas PGRI Madiun. The development model used is 4-D modified to 3-D until the stage development. The type of data used is descriptive qualitative data. Instruments used are sheets of validation, test, and questionnaire. Development results indicate that group investigation-based book on numerical analysis in the category of valid a value 84.25%. Students response to the books very positive, so group investigation-based book on numerical analysis category practical, i.e., 86.00%. The use of group investigation-based book on numerical analysis has been meeting the completeness criteria classical learning that is 84.32 %. Based on research result of this study concluded that group investigation-based book on numerical analysis is feasible because it meets the criteria valid, practical, and effective. So, the book can be used by every mathematics academician. The next research can be observed that book based group investigation in other subjects.
Directory of Open Access Journals (Sweden)
Joonkoo Park
2018-04-01
Full Text Available While recent studies in adults have demonstrated the existence of a neural mechanism for a visual sense of number, little is known about its development and whether such a mechanism exists at young ages. In the current study, I introduce a novel steady-state visual evoked potential (SSVEP technique to objectively quantify early visual cortical sensitivity to numerical and non-numerical magnitudes of a dot array. I then examine this neural sensitivity to numerical magnitude in children between three and ten years of age and in college students. Children overall exhibit strong SSVEP sensitivity to numerical magnitude in the right occipital sites with negligible SSVEP sensitivity to non-numerical magnitudes, the pattern similar to what is observed in adults. However, a closer examination of age differences reveals that this selective neural sensitivity to numerical magnitude, which is close to absent in three-year-olds, increases steadily as a function of age, while there is virtually no neural sensitivity to other non-numerical magnitudes across these ages. These results demonstrate the emergence of a neural mechanism underlying direct perception of numerosity across early and middle childhood and provide a potential neural mechanistic explanation for the development of humans’ primitive, non-verbal ability to comprehend number. Keywords: Numerosity, Steady-state visual evoked potential, Child development, Visual cortex, Approximate number system
Frozen reaction fronts in steady flows: A burning-invariant-manifold perspective
Mahoney, John R.; Li, John; Boyer, Carleen; Solomon, Tom; Mitchell, Kevin A.
2015-12-01
The dynamics of fronts, such as chemical reaction fronts, propagating in two-dimensional fluid flows can be remarkably rich and varied. For time-invariant flows, the front dynamics may simplify, settling in to a steady state in which the reacted domain is static, and the front appears "frozen." Our central result is that these frozen fronts in the two-dimensional fluid are composed of segments of burning invariant manifolds, invariant manifolds of front-element dynamics in x y θ space, where θ is the front orientation. Burning invariant manifolds (BIMs) have been identified previously as important local barriers to front propagation in fluid flows. The relevance of BIMs for frozen fronts rests in their ability, under appropriate conditions, to form global barriers, separating reacted domains from nonreacted domains for all time. The second main result of this paper is an understanding of bifurcations that lead from a nonfrozen state to a frozen state, as well as bifurcations that change the topological structure of the frozen front. Although the primary results of this study apply to general fluid flows, our analysis focuses on a chain of vortices in a channel flow with an imposed wind. For this system, we present both experimental and numerical studies that support the theoretical analysis developed here.
Numerical modelling of random walk one-dimensional diffusion
International Nuclear Information System (INIS)
Vamos, C.; Suciu, N.; Peculea, M.
1996-01-01
The evolution of a particle which moves on a discrete one-dimensional lattice, according to a random walk low, approximates better the diffusion process smaller the steps of the spatial lattice and time are. For a sufficiently large assembly of particles one can assume that their relative frequency at lattice knots approximates the distribution function of the diffusion process. This assumption has been tested by simulating on computer two analytical solutions of the diffusion equation: the Brownian motion and the steady state linear distribution. To evaluate quantitatively the similarity between the numerical and analytical solutions we have used a norm given by the absolute value of the difference of the two solutions. Also, a diffusion coefficient at any lattice knots and moment of time has been calculated, by using the numerical solution both from the diffusion equation and the particle flux given by Fick's low. The difference between diffusion coefficient of analytical solution and the spatial lattice mean coefficient of numerical solution constitutes another quantitative indication of the similarity of the two solutions. The results obtained show that the approximation depends first on the number of particles at each knot of the spatial lattice. In conclusion, the random walk is a microscopic process of the molecular dynamics type which permits simulations precision of the diffusion processes with given precision. The numerical method presented in this work may be useful both in the analysis of real experiments and for theoretical studies
Steady, three-dimensional, internally heated convection
International Nuclear Information System (INIS)
Schubert, G.; Glatzmaier, G.A.; Travis, B.
1993-01-01
Numerical calculations have been carried out of steady, symmetric, three-dimensional modes of convection in internally heated, infinite Prandtl number, Boussinesq fluids at a Rayleigh number of 1.4x10 4 in a spherical shell with inner/outer radius of 0.55 and in a 3x3x1 rectangular box. Multiple patterns of convection occur in both geometries. In the Cartesian geometry the patterns are dominated by cylindrical cold downflows and a broad hot upwelling. In the spherical geometry the patterns consist of cylindrical cold downwellings centered either at the vertices of a tetrahedron or the centers of the faces of a cube. The cold downflow cylinders are immersed in a background of upwelling within which there are cylindrical hot concentrations (plumes) and hot halos around the downflows. The forced hot upflow return plumes of internally heated spherical convection are fundamentally different from the buoyancy-driven plumes of heated from below convection
Numerical equilibrium analysis for structured consumer resource models
de Roos, A.M.; Diekmann, O.; Getto, P.; Kirkilionis, M.A.
2010-01-01
In this paper, we present methods for a numerical equilibrium and stability analysis for models of a size structured population competing for an unstructured re- source. We concentrate on cases where two model parameters are free, and thus existence boundaries for equilibria and stability boundaries
Numerical equilibrium analysis for structured consumer resource models
de Roos, A.M.; Diekmann, O.; Getto, P.; Kirkilionis, M.A.
2010-01-01
In this paper, we present methods for a numerical equilibrium and stability analysis for models of a size structured population competing for an unstructured resource. We concentrate on cases where two model parameters are free, and thus existence boundaries for equilibria and stability boundaries
Steady States in SIRS Epidemical Model of Mobile Individuals
International Nuclear Information System (INIS)
Zhang Duanming; He Minhua; Yu Xiaoling; Pan Guijun; Sun Hongzhang; Su Xiangying; Sun Fan; Yin Yanping; Li Rui; Liu Dan
2006-01-01
We consider an epidemical model within socially interacting mobile individuals to study the behaviors of steady states of epidemic propagation in 2D networks. Using mean-field approximation and large scale simulations, we recover the usual epidemic behavior with critical thresholds δ c and p c below which infectious disease dies out. For the population density δ far above δ c , it is found that there is linear relationship between contact rate λ and the population density δ in the main. At the same time, the result obtained from mean-field approximation is compared with our numerical result, and it is found that these two results are similar by and large but not completely the same.
Steady States in SIRS Epidemical Model of Mobile Individuals
Institute of Scientific and Technical Information of China (English)
ZHANG Duan-Ming; LIU Dan; HE Min-Hua; YU Xiao-Ling; PAN Gui-Jun; SUN Hong-Zhang; SU Xiang-Ying; SUN Fan; YIN Yan-Ping; LI Rui
2006-01-01
We consider an epidemical model within socially interacting mobile individuals to study the behaviors of steady statesof epidemic propagation in 2D networks. Using mean-field approximation and large scale simulations, we recover the usual epidemic behavior with critical thresholds δc and pc below which infectious disease dies out. For the population density δ far above δc, it is found that there is linear relationship between contact rate λ and the population density δ in the main. At the same time, the result obtained from mean-field approximation is compared with our numerical result, and it is found that these two results are similar by and large but not completely the same.
Crittenden, P. E.; Balachandar, S.
2018-03-01
The radial one-dimensional Euler equations are often rewritten in what is known as the geometric source form. The differential operator is identical to the Cartesian case, but source terms result. Since the theory and numerical methods for the Cartesian case are well-developed, they are often applied without modification to cylindrical and spherical geometries. However, numerical conservation is lost. In this article, AUSM^+ -up is applied to a numerically conservative (discrete) form of the Euler equations labeled the geometric form, a nearly conservative variation termed the geometric flux form, and the geometric source form. The resulting numerical methods are compared analytically and numerically through three types of test problems: subsonic, smooth, steady-state solutions, Sedov's similarity solution for point or line-source explosions, and shock tube problems. Numerical conservation is analyzed for all three forms in both spherical and cylindrical coordinates. All three forms result in constant enthalpy for steady flows. The spatial truncation errors have essentially the same order of convergence, but the rate constants are superior for the geometric and geometric flux forms for the steady-state solutions. Only the geometric form produces the correct shock location for Sedov's solution, and a direct connection between the errors in the shock locations and energy conservation is found. The shock tube problems are evaluated with respect to feature location using an approximation with a very fine discretization as the benchmark. Extensions to second order appropriate for cylindrical and spherical coordinates are also presented and analyzed numerically. Conclusions are drawn, and recommendations are made. A derivation of the steady-state solution is given in the Appendix.
Bifurcation Behavior Analysis in a Predator-Prey Model
Directory of Open Access Journals (Sweden)
Nan Wang
2016-01-01
Full Text Available A predator-prey model is studied mathematically and numerically. The aim is to explore how some key factors influence dynamic evolutionary mechanism of steady conversion and bifurcation behavior in predator-prey model. The theoretical works have been pursuing the investigation of the existence and stability of the equilibria, as well as the occurrence of bifurcation behaviors (transcritical bifurcation, saddle-node bifurcation, and Hopf bifurcation, which can deduce a standard parameter controlled relationship and in turn provide a theoretical basis for the numerical simulation. Numerical analysis ensures reliability of the theoretical results and illustrates that three stable equilibria will arise simultaneously in the model. It testifies the existence of Bogdanov-Takens bifurcation, too. It should also be stressed that the dynamic evolutionary mechanism of steady conversion and bifurcation behavior mainly depend on a specific key parameter. In a word, all these results are expected to be of use in the study of the dynamic complexity of ecosystems.
Steady state magnetic field configurations for the earth's magnetotail
International Nuclear Information System (INIS)
Hau, L.N.; Wolf, R.A.; Voigt, G.H.; Wu, C.C.
1989-01-01
The authors present a two-dimensional, force-balanced magnetic field model in which flux tubes have constant pVγ throughout an extended region of the nightside plasma sheet, between approximately 36 R E geocentric distance and the region of the inner edge of the plasma sheet. They have thus demonstrated the theoretical existence of a steady state magnetic field configuration that is force-balanced and also consistent with slow, lossless, adiabatic, earthward convection within the limit of the ideal MHD (isotropic pressure, perfect conductivity). The numerical solution was constructed for a two-dimensional magnetosphere with a rectangular magnetopause and nonflaring tail. The primary characteristics of the steady state convection solution are (1) a pressure maximum just tailward of the inner edge of the plasma sheet and (2) a deep, broad minimum in equatorial magnetic field strength B ze , also just tailward of the inner edge. The results are consistent with Erickson's (1985) convection time sequences, which exhibited analogous pressure peaks and B ze minima. Observations do not indicate the existence of a B ze minimum, on the average. They suggest that the configurations with such deep minima in B ze may be tearing-mode unstable, thus leading to substorm onset in the inner plasma sheet
International Nuclear Information System (INIS)
Bosser, M.; Vagner, J.
1987-01-01
The fatigue behavior of a bolted assembly can be analysed, either by fatigue tests, or by computing the stress variations and using a fatigue curve. This paper presents the fatigue analysis of a stud-bolt and stud-flange of a steam generator manway carried out with the two methods. The experimental analysis is performed for various levels of load, according to the recommandations of the ASME code section III appendix II. The numerical analysis of the stresses is based on the results of a finite element analysis performed with the program SYSTUS. The maximum stresses are obtained in the first bolt threads. In using these stresses, the allowable number of cycles for each level of loading analysed, is obtained from fatigue curves, as defined in appendix I section III of the ASME code. The analysis underlines that, for each level of load the purely numerical approach is highly conservative, compared to the experimental approach. (orig.)
Data system design considerations for a pseudo-steady-state device
International Nuclear Information System (INIS)
Wing, W.R.
1981-01-01
The Advanced Toroidal Facility is being designed to run in a steady state. This places stringent requirements on a data system, since it must provide steady-state support that is equivalent to the support users are accustomed to from pulsed experiments; i.e., enough capacity to reduce diagnostic data for live presentation. Parameters such as density, position, and temperature must be presented live (i.e., within 0.1 s). Quantities such as plasma shape or internal structure should be available with a minimum of delay. The traditional solution to providing such capabilities is to use distributed processing to off-load data acquisition from the analysis computers. However, this suffers in a real-time environment because of the necessity of moving large quantities of data from acquisition to analysis. We expect to solve the problem by using a pipelined design that will acquire data directly into shared memory, where any one of four CPU's (VAX 11/780's) can proceed with analysis
Experimental and Numerical analysis of Metallic Bellow for Acoustic Performance
Panchwadkar, Amit A.; Awasare, Pradeep J., Dr.; Ingle, Ravidra B., Dr.
2017-08-01
Noise will concern about the work environment of industry. Machinery environment has overall noise which interrupts communication between the workers. This problem of miscommunication and health hazard will make sense to go for noise attenuation. Modification in machine setup may affect the performance of it. Instead of that, Helmholtz resonator principle will be a better option for noise reduction along the transmission path. Resonator has design variables which gives resonating frequency will help us to confirm the frequency range. This paper deals with metallic bellow which behaves like inertial mass under incident sound wave. Sound wave energy is affected by hard boundary condition of resonator and bellow. Metallic bellow is used in combination with resonator to find out Transmission loss (TL). Microphone attachment with FFT analyzer will give the frequency range for numerical analysis. Numerical analysis of bellow and resonator is carried out to summarize the acoustic behavior of bellow. Bellow can be numerically analyzed to check noise attenuation for centrifugal blower. An impedance tube measurement technique is performed to validate the numerical results for assembly. Dimensional and shape modification can be done to get the acoustic performance of bellow.
Burn-up dependent steady-state thermal hydraulic analysis of Pakistan research reactor-1
Directory of Open Access Journals (Sweden)
Muhammad Atta
2011-01-01
Full Text Available The burn-up dependent steady-state thermal hydraulic analysis of Pakistan research reactor-1, reference operating core, has been carried out utilizing standard computer codes WIMS/D4, CITATION, and RELAP5/MOD3.4. Reactor codes WIMS/D4 and CITATION have been used for the calculations of neutronic parameters including peaking factors and power profiles at different burn-up considering a xenon free core and also the equilibrium xenon values. RELAP5/MOD3.4 code was utilized for the determination of peak fuel centerline, clad and coolant temperatures to ensure the safety of the reactor throughout the cycle. The calculations reveal that the reactor is safe and no nucleate boiling will commence at any part of the core throughout the cycle and that the safety margin increases with burnup as peaking factors decrease.
International Nuclear Information System (INIS)
Castagnoli, G.
1991-01-01
This paper reports that current conceptions of quantum mechanical computers inherit from conventional digital machines two apparently interacting features, machine imperfection and temporal development of the computational process. On account of machine imperfection, the process would become ideally reversible only in the limiting case of zero speed. Therefore the process is irreversible in practice and cannot be considered to be a fundamental quantum one. By giving up classical features and using a linear, reversible and non-sequential representation of the computational process - not realizable in classical machines - the process can be identified with the mathematical form of a quantum steady state. This form of steady quantum computation would seem to have an important bearing on the notion of cognition
Energy Technology Data Exchange (ETDEWEB)
Castagnoli, G. (Dipt. di Informatica, Sistemistica, Telematica, Univ. di Genova, Viale Causa 13, 16145 Genova (IT))
1991-08-10
This paper reports that current conceptions of quantum mechanical computers inherit from conventional digital machines two apparently interacting features, machine imperfection and temporal development of the computational process. On account of machine imperfection, the process would become ideally reversible only in the limiting case of zero speed. Therefore the process is irreversible in practice and cannot be considered to be a fundamental quantum one. By giving up classical features and using a linear, reversible and non-sequential representation of the computational process - not realizable in classical machines - the process can be identified with the mathematical form of a quantum steady state. This form of steady quantum computation would seem to have an important bearing on the notion of cognition.
Analysis of the steady-state operation of vacuum systems for fusion machines
International Nuclear Information System (INIS)
Roose, T.R.; Hoffman, M.A.; Carlson, G.A.
1975-01-01
A computer code named GASBAL was written to calculate the steady-state vacuum system performance of multi-chamber mirror machines as well as rather complex conventional multichamber vacuum systems. Application of the code, with some modifications, to the quasi-steady tokamak operating period should also be possible. Basically, GASBAL analyzes free molecular gas flow in a system consisting of a central chamber (the plasma chamber) connected by conductances to an arbitrary number of one- or two-chamber peripheral tanks. Each of the peripheral tanks may have vacuum pumping capability (pumping speed), sources of cold gas, and sources of energetic atoms. The central chamber may have actual vacuum pumping capability, as well as a plasma capable of ionizing injected atoms and impinging gas molecules and ''pumping'' them to a peripheral chamber. The GASBAL code was used in the preliminary design of a large mirror machine experiment--LLL's MX
Thermal response of a pin-type fusion reactor blanket during steady and transient reactor operation
International Nuclear Information System (INIS)
Grotz, S.; Ghoniem, N.M.
1986-02-01
The thermal analysis of the blanket examines both the steady-state and transient reactor operations. The steady-state analysis covers full power and fractional power operation whereas the transient analysis examines the effects of power ramps and blanket preheat. The blanket configuration chosen for this study is a helium cooled solid breeder design. We first discuss the full power, steady-state temperature fields in the first wall, beryllium rods, and breeder rods. Next we examine the effects of fractional power on coolant flow and temperature field distributions. This includes power plateaus of 10%, 20%, 50%, 80%, and 100% of full power. Also examined are the restrictions on the rates of power ramping between plateaus. Finally we discuss the power and time requirements for pre-heating the primary from cold iron conditions up to startup temperature (250 0 C)
PAREX, a numerical code in the service of La Hague plant operations
Energy Technology Data Exchange (ETDEWEB)
Bisson, J.; Huron, P.; Huel, C. [AREVA NC, La Hague Plant, Technical Direction, 50444, Beaumont-Hague (France); Dinh, B. [CEA, Centre de Marcoule, Nuclear Energy Division, Radiochemistry and Process Department, F-30207, Bagnols-sur-Ceze (France)
2016-07-01
The PAREX code developed by the CEA is able to simulate the PUREX process in steady or transient state. From an operator point of view, this numerical code for simulation of liquid-liquid extraction operations is an outstanding tool as an aid for plant operation through process flow sheet optimization, troubleshooting and safety analysis calculations. This paper focuses on two examples. The first concerns the evaluation of the available operating margin of the extraction zone of the first purification cycle flowsheet. The second example concerns a uranium-plutonium splitting operation where the code was used to explain a shift of plutonium concentration in the solvent outlet. (authors)
On the optimization of a steady-state bootstrap-reactor
International Nuclear Information System (INIS)
Polevoy, A.R.; Martynov, A.A.; Medvedev, S.Yu.
1993-01-01
A commercial fusion tokamak-reactor may be economically acceptable only for low recirculating power fraction r 0 ≡ P CD /P α BS ≡I BS /I > 0.9 to sustain the steady-state operation mode for high plasma densities > 1.5 10 20 m -3 , fulfilled the divertor conditions. This paper presents the approximate expressions for the optimal set of reactor parameters for r BS /I∼1, based on the self-consistent plasma simulations by 1.5D ASTRA code. The linear MHD stability analysis for ideal n=1 kink and ballooning modes has been carried out to determine the conditions of stabilization for bootstrap steady state tokamak reactor BSSTR configurations. (author) 10 refs., 1 tab
Pseudo Steady-State Free Precession for MR-Fingerprinting.
Assländer, Jakob; Glaser, Steffen J; Hennig, Jürgen
2017-03-01
This article discusses the signal behavior in the case the flip angle in steady-state free precession sequences is continuously varied as suggested for MR-fingerprinting sequences. Flip angle variations prevent the establishment of a steady state and introduce instabilities regarding to magnetic field inhomogeneities and intravoxel dephasing. We show how a pseudo steady state can be achieved, which restores the spin echo nature of steady-state free precession. Based on geometrical considerations, relationships between the flip angle, repetition and echo time are derived that suffice to the establishment of a pseudo steady state. The theory is tested with Bloch simulations as well as phantom and in vivo experiments. A typical steady-state free precession passband can be restored with the proposed conditions. The stability of the pseudo steady state is demonstrated by comparing the evolution of the signal of a single isochromat to one resulting from a spin ensemble. As confirmed by experiments, magnetization in a pseudo steady state can be described with fewer degrees of freedom compared to the original fingerprinting and the pseudo steady state results in more reliable parameter maps. The proposed conditions restore the spin-echo-like signal behavior typical for steady-state free precession in fingerprinting sequences, making this approach more robust to B 0 variations. Magn Reson Med 77:1151-1161, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.
Numerical analysis and nuclear standard code application to thermal fatigue
International Nuclear Information System (INIS)
Merola, M.
1992-01-01
The present work describes the Joint Research Centre Ispra contribution to the IAEA benchmark exercise 'Lifetime Behaviour of the First Wall of Fusion Machines'. The results of the numerical analysis of the reference thermal fatigue experiment are presented. Then a discussion on the numerical analysis of thermal stress is tackled, pointing out its particular aspects in view of their influence on the stress field evaluation. As far as the design-allowable number of cycles are concerned the American nuclear code ASME and the French code RCC-MR are applied and the reasons for the different results obtained are investigated. As regards a realistic fatigue lifetime evaluation, the main problems to be solved are brought out. This work, is intended as a preliminary basis for a discussion focusing on the main characteristics of the thermal fatigue problem from both a numerical and a lifetime assessment point of view. In fact the present margin of discretion left to the analyst may cause undue discrepancies in the results obtained. A sensitivity analysis of the main parameters involved is desirable and more precise design procedures should be stated
Enhancing the ABAQUS Thermomechanics Code to Simulate Steady and Transient Fuel Rod Behavior
International Nuclear Information System (INIS)
Williamson, R.L.; Knoll, D.A.
2009-01-01
A powerful multidimensional fuels performance capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth, gap heat transfer, and gap/plenum gas behavior during irradiation. The various modeling capabilities are demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multi-pellet fuel rod, during both steady and transient operation. Computational results demonstrate the importance of a multidimensional fully-coupled thermomechanics treatment. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermo-mechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths.
Combined Steady-State and Dynamic Heat Exchanger Experiment
Luyben, William L.; Tuzla, Kemal; Bader, Paul N.
2009-01-01
This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…
Engelbrecht, Nicolaas; Chiuta, Steven; Bessarabov, Dmitri G.
2018-05-01
The experimental evaluation of an autothermal microchannel reactor for H2 production from NH3 decomposition is described. The reactor design incorporates an autothermal approach, with added NH3 oxidation, for coupled heat supply to the endothermic decomposition reaction. An alternating catalytic plate arrangement is used to accomplish this thermal coupling in a cocurrent flow strategy. Detailed analysis of the transient operating regime associated with reactor start-up and steady-state results is presented. The effects of operating parameters on reactor performance are investigated, specifically, the NH3 decomposition flow rate, NH3 oxidation flow rate, and fuel-oxygen equivalence ratio. Overall, the reactor exhibits rapid response time during start-up; within 60 min, H2 production is approximately 95% of steady-state values. The recommended operating point for steady-state H2 production corresponds to an NH3 decomposition flow rate of 6 NL min-1, NH3 oxidation flow rate of 4 NL min-1, and fuel-oxygen equivalence ratio of 1.4. Under these flows, NH3 conversion of 99.8% and H2 equivalent fuel cell power output of 0.71 kWe is achieved. The reactor shows good heat utilization with a thermal efficiency of 75.9%. An efficient autothermal reactor design is therefore demonstrated, which may be upscaled to a multi-kW H2 production system for commercial implementation.
Analysis of control rod behavior based on numerical simulation
International Nuclear Information System (INIS)
Ha, D. G.; Park, J. K.; Park, N. G.; Suh, J. M.; Jeon, K. L.
2010-01-01
The main function of a control rod is to control core reactivity change during operation associated with changes in power, coolant temperature, and dissolved boron concentration by the insertion and withdrawal of control rods from the fuel assemblies. In a scram, the control rod assemblies are released from the CRDMs (Control Rod Drive Mechanisms) and, due to gravity, drop rapidly into the fuel assemblies. The control rod insertion time during a scram must be within the time limits established by the overall core safety analysis. To assure the control rod operational functions, the guide thimbles shall not obstruct the insertion and withdrawal of the control rods or cause any damage to the fuel assembly. When fuel assembly bow occurs, it can affect both the operating performance and the core safety. In this study, the drag forces of the control rod are estimated by a numerical simulation to evaluate the guide tube bow effect on control rod withdrawal. The contact condition effects are also considered. A full scale 3D model is developed for the evaluation, and ANSYS - commercial numerical analysis code - is used for this numerical simulation. (authors)
Effects of Energy Beverage Consumption on Pistol Aiming Steadiness in Law Enforcement Officers.
Monaghan, Taylor P; Jacobson, Bert H; Sellers, John H; Estrada, Carlos A
2017-09-01
Monaghan, TP, Jacobson, BH, Sellers, JH, and Estrada, CA. Effects of energy beverage consumption on pistol aiming steadiness in law enforcement officers. J Strength Cond Res 31(9): 2557-2561, 2017-The popularity of energy drinks (EDs)/shots (ESs) has grown steadily over the years resulting in billions of dollars of sales annually. Energy drink marketing focuses on the improved performance and alertness and a reduction in fatigue. Although caffeine comprises one of the ingredients, it is not fully known how the combination of the many remaining active ingredients affects physical performance. The purpose of this study was to investigate the effect of a commercially available ES on pistol aiming steadiness. Subjects (N = 10) consisted of accredited police officers in the Midwest. A randomized, blinded, crossover design was used to evaluate the pistol aiming steadiness after the consumption of an ES or placebo. Pistol aiming steadiness was measured using a hole/stylus steadiness tester and laser attached to a training pistol before and 30 minutes after ES or placebo consumption. Analysis revealed that the ES significantly (p ≤ 0.05) impaired pistol steadiness, whereas the placebo yielded no significant difference in aiming steadiness. Based on these results, it was concluded that the consumption of an ES could compromise aiming accuracy and shot placement, thereby jeopardizing the health and welfare of law enforcement personnel.
Multimode optical fibers: steady state mode exciter.
Ikeda, M; Sugimura, A; Ikegami, T
1976-09-01
The steady state mode power distribution of the multimode graded index fiber was measured. A simple and effective steady state mode exciter was fabricated by an etching technique. Its insertion loss was 0.5 dB for an injection laser. Deviation in transmission characteristics of multimode graded index fibers can be avoided by using the steady state mode exciter.
Development and validation of a free-piston engine generator numerical model
International Nuclear Information System (INIS)
Jia, Boru; Zuo, Zhengxing; Tian, Guohong; Feng, Huihua; Roskilly, A.P.
2015-01-01
Highlights: • Detailed numerical model of free-piston engine generator is presented. • Sub models for both starting process and steady operation are derived. • Simulation results show good agreement with prototype test data. • Engine performance with different starting motor force and varied loads are simulated. • The efficiency of the prototype is estimated to be 31.5% at a power output of 4 kW under full load. - Abstract: This paper focuses on the numerical modelling of a spark ignited free-piston engine generator and the model validation with test results. Detailed sub-models for both starting process and steady operation were derived. The compression and expansion processes were not regarded as ideal gas isentropic processes; both heat transfer and air leakage were taken into consideration. The simulation results show good agreement with the prototype test data for both the starting process and steady operation. During the starting process, the difference of the in-cylinder gas pressure can be controlled within 1 bar for every running cycle. For the steady operation process, the difference was less than 5% and the areas enclosed on the pressure–volume diagram were similar, indicating that the power produced by the engine and the engine efficiency could be predicted by this model. Based on this model, the starting process with different starting motor forces and the combustion process with various throttle openings were simulated. The engine performance during stable operation at 100% engine load was predicted, and the efficiency of the prototype was estimated to be 31.5% at power output of 4 kW
Czech Academy of Sciences Publication Activity Database
Ač, Alexander; Malenovský, Z.; Olejníčková, Julie; Gallé, A.; Rascher, U.; Mohammed, G.
2015-01-01
Roč. 168, oct (2015), s. 420-436 ISSN 0034-4257 R&D Projects: GA MŠk(CZ) LO1415 Institutional support: RVO:67179843 Keywords : steady-state chlorophyll fluorescence * passive sun-induced fluorescence * active laser-induced fluorescence * photosynthesis * stress * water * temperature * nitrogen * random-effects meta-analysis * FLEX satellite mission Subject RIV: EH - Ecology, Behaviour Impact factor: 5.881, year: 2015
Ho, Pang-Yen; Chuang, Guo-Syong; Chao, An-Chong; Li, Hsing-Ya
2005-05-01
The capacity of complex biochemical reaction networks (consisting of 11 coupled non-linear ordinary differential equations) to show multiple steady states, was investigated. The system involved esterification of ethanol and oleic acid by lipase in an isothermal continuous stirred tank reactor (CSTR). The Deficiency One Algorithm and the Subnetwork Analysis were applied to determine the steady state multiplicity. A set of rate constants and two corresponding steady states are computed. The phenomena of bistability, hysteresis and bifurcation are discussed. Moreover, the capacity of steady state multiplicity is extended to the family of the studied reaction networks.
Energy Technology Data Exchange (ETDEWEB)
Hansen, C., E-mail: hansec@uw.edu [PSI-Center, University of Washington, Seattle, Washington 98195 (United States); Columbia University, New York, New York 10027 (United States); Marklin, G. [PSI-Center, University of Washington, Seattle, Washington 98195 (United States); Victor, B. [HIT-SI Group, University of Washington, Seattle, Washington 98195 (United States); Akcay, C. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Jarboe, T. [HIT-SI Group, University of Washington, Seattle, Washington 98195 (United States); PSI-Center, University of Washington, Seattle, Washington 98195 (United States)
2015-04-15
We present simulations of inductive helicity injection in the Helicity Injected Torus with Steady Inductive helicity injection (HIT-SI) device that treats the entire plasma volume in a single dynamic MHD model. A new fully 3D numerical tool, the PSI-center TETrahedral mesh code, was developed that provides the geometric flexibility required for this investigation. Implementation of a zero-β Hall MHD model using PSI-TET will be presented including formulation of a new self-consistent magnetic boundary condition for the wall of the HIT-SI device. Results from simulations of HIT-SI are presented focusing on injector dynamics that are investigated numerically for the first time. Asymmetries in the plasma loading between the two helicity injectors and progression of field reversal in each injector are observed. Analysis indicates cross-coupling between injectors through confinement volume structures. Injector impedance is found to scale with toroidal current at fixed density, consistent with experimental observation. Comparison to experimental data with an injector drive frequency of 14.5 kHz shows good agreement with magnetic diagnostics. Global mode structures from Bi-Orthogonal decomposition agree well with experimental data for the first four modes.
Numerical Limit Analysis of Reinforced Concrete Structures
DEFF Research Database (Denmark)
Larsen, Kasper Paaske
For more than half a century, limit state analysis based on the extremum principles have been used to assess the load bearing capacity of reinforced concrete structures. Extensi- ve research within the field has lead to several techniques for performing such analysis manually. While these manual...... methods provide engineers with valuable tools for limit sta- te analysis, their application becomes difficult with increased structural complexity. The main challenge is to solve the optimization problem posed by the extremum principles. This thesis is a study of how numerical methods can be used to solve...... limit state analysis problems. The work focuses on determination of the load bearing capacity of reinforced concrete structures by employing the lower bound theorem and a finite element method using equilibrium elements is developed. The recent year’s development within the field of convex optimization...
International Nuclear Information System (INIS)
Uchibori, Akihiro; Ohshima, Hiroyuki
2008-01-01
A numerical analysis method for melting/solidification phenomena has been developed to evaluate a feasibility of several candidate techniques in the nuclear fuel cycle. Our method is based on the eXtended Finite Element Method (X-FEM) which has been used for moving boundary problems. Key technique of the X-FEM is to incorporate signed distance function into finite element interpolation to represent a discontinuous gradient of the temperature at a moving solid-liquid interface. Construction of the finite element equation, the technique of quadrature and the method to solve the equation are reported here. The numerical solutions of the one-dimensional Stefan problem, solidification in a two-dimensional square corner and melting of pure gallium are compared to the exact solutions or to the experimental data. Through these analyses, validity of the newly developed numerical analysis method has been demonstrated. (author)
NUMERICAL THERMAL ANALYSIS OF A CAR BRAKING SYSTEM
Directory of Open Access Journals (Sweden)
Patryk Różyło
2017-06-01
Full Text Available The study involved performing a numerical thermal analysis of selected components in a car braking system. The primary goal of the study was to determine the regions which are the most susceptible to variations in temperature, and to determine the degree of thermal impact upon them. The analysis was performed using the Abaqus environment. The examined components of the braking system were made of materials reflecting the mechanical properties of the real subassemblies. The FEM analysis enabled determination of the distribution of temperature in the system with respect to the properties of the investigated materials and applied boundary conditions.
Cardiff, M.; Bakhos, T.; Kitanidis, P. K.; Barrash, W.
2013-09-01
Periodic pumping tests, in which a fluid is extracted during half a period, then reinjected, have been used historically to estimate effective aquifer properties. In this work, we suggest a modified approach to periodic pumping test analysis in which one uses several periodic pumping signals of different frequencies as stimulation, and responses are analyzed through inverse modeling using a "steady-periodic" model formulation. We refer to this strategy as multifrequency oscillatory hydraulic imaging. Oscillating pumping tests have several advantages that have been noted, including no net water extraction during testing and robust signal measurement through signal processing. Through numerical experiments, we demonstrate additional distinct advantages that multifrequency stimulations have, including: (1) drastically reduced computational cost through use of a steady-periodic numerical model and (2) full utilization of the aquifer heterogeneity information provided by responses at different frequencies. We first perform fully transient numerical modeling for heterogeneous aquifers and show that equivalent results are obtained using a faster steady-periodic heterogeneous numerical model of the wave phasor. The sensitivities of observed signal response to aquifer heterogeneities are derived using an adjoint state-based approach, which shows that different frequency stimulations provide complementary information. Finally, we present an example 2-D application in which sinusoidal signals at multiple frequencies are used as a data source and are inverted to obtain estimates of aquifer heterogeneity. These analyses show the different heterogeneity information that can be obtained from different stimulation frequencies, and that data from several sinusoidal pumping tests can be rapidly inverted using the steady-periodic framework.
The behaviour of impurities in a steady-state DT gas-blanket reactor
International Nuclear Information System (INIS)
Markvoort, J.A.
1975-11-01
A four-fluid model of a cylindrical steady-state DT gas-blanket reactor is analysed. The four fluids are electrons, deuterium-tritium, helium and a high -Z impurity. The behaviour of the plasma is described by the multifluid MHD-equations which are numerically solved with the aid of a Runge Kutta method. Whether impurities tend to concentrate on the axis is found to depend on how, in the collision term, the Nernst effect is taken into account. In order to show the influence of the Nernst terms arising from electron-ion collisions and the Nernst terms due to ion-ion collisions separately, the thermal force is dealt with in two ways. In model A, only the contribution from electron-ion collisions was considered. The computer calculations show that the impurities have their maximum concentration on the axis. A theoretical analysis explains this result. In model B, which is more realistic, these ion-ion collisions are included. The computer calculations as well as the theoretical analysis show that the influence of the thermoforce due to ion-ion collisions on the density profiles dominates over the force due to electron collisions, and lead to a minimum in the impurity density on the axis. As in model A, the analytical analysis yields relationships between the various density profiles and the temperature profile
Methods of computing steady-state voltage stability margins of power systems
Chow, Joe Hong; Ghiocel, Scott Gordon
2018-03-20
In steady-state voltage stability analysis, as load increases toward a maximum, conventional Newton-Raphson power flow Jacobian matrix becomes increasingly ill-conditioned so power flow fails to converge before reaching maximum loading. A method to directly eliminate this singularity reformulates the power flow problem by introducing an AQ bus with specified bus angle and reactive power consumption of a load bus. For steady-state voltage stability analysis, the angle separation between the swing bus and AQ bus can be varied to control power transfer to the load, rather than specifying the load power itself. For an AQ bus, the power flow formulation is only made up of a reactive power equation, thus reducing the size of the Jacobian matrix by one. This reduced Jacobian matrix is nonsingular at the critical voltage point, eliminating a major difficulty in voltage stability analysis for power system operations.
Application of numerical analysis methods to thermoluminescence dosimetry
International Nuclear Information System (INIS)
Gomez Ros, J. M.; Delgado, A.
1989-01-01
This report presents the application of numerical methods to thermoluminescence dosimetry (TLD), showing the advantages obtained over conventional evaluation systems. Different configurations of the analysis method are presented to operate in specific dosimetric applications of TLD, such as environmental monitoring and mailed dosimetry systems for quality assurance in radiotherapy facilities. (Author) 10 refs
Interactive Numerical and Symbolic Analysis: A New Paradigm for Teaching Electronics
Directory of Open Access Journals (Sweden)
Jean-Claude Thomassian
2008-09-01
Full Text Available Analog Insydes, Mathematica’s symbolic circuit analysis toolbox, uses modern algorithms of expression simplification depending on comparisons with a numerical reference solution of the circuit under investigation. Some insight is offered on how the complexity of an expression barrier is overcome followed by two classical examples, a BJT emitter follower and a MOSFET common-gate amplifier stage to illustrate the proposed method at work. A concluding section discusses that time spent teaching introductory electronics by computer-aided circuit analysis, interactive numerical and symbolic, is a worthwhile investment.
Solutions manual to accompany An introduction to numerical methods and analysis
Epperson, James F
2014-01-01
A solutions manual to accompany An Introduction to Numerical Methods and Analysis, Second Edition An Introduction to Numerical Methods and Analysis, Second Edition reflects the latest trends in the field, includes new material and revised exercises, and offers a unique emphasis on applications. The author clearly explains how to both construct and evaluate approximations for accuracy and performance, which are key skills in a variety of fields. A wide range of higher-level methods and solutions, including new topics such as the roots of polynomials, sp
Mathematical, physical and numerical principles essential for models of turbulent mixing
Energy Technology Data Exchange (ETDEWEB)
Sharp, David Howland [Los Alamos National Laboratory; Lim, Hyunkyung [STONY BROOK UNIV; Yu, Yan [STONY BROOK UNIV; Glimm, James G [STONY BROOK UNIV
2009-01-01
We propose mathematical, physical and numerical principles which are important for the modeling of turbulent mixing, especially the classical and well studied Rayleigh-Taylor and Richtmyer-Meshkov instabilities which involve acceleration driven mixing of a fluid discontinuity layer, by a steady accerleration or an impulsive force.
Numerical Investigations of Unsteady Flow in a Centrifugal Pump with a Vaned Diffuser
Directory of Open Access Journals (Sweden)
Olivier Petit
2013-01-01
Full Text Available Computational fluid dynamics (CFD analyses were made to study the unsteady three-dimensional turbulence in the ERCOFTAC centrifugal pump test case. The simulations were carried out using the OpenFOAM Open Source CFD software. The test case consists of an unshrouded centrifugal impeller with seven blades and a radial vaned diffuser with 12 vanes. A large number of measurements are available in the radial gap between the impeller and the diffuse, making this case ideal for validating numerical methods. Results of steady and unsteady calculations of the flow in the pump are compared with the experimental ones, and four different turbulent models are analyzed. The steady simulation uses the frozen rotor concept, while the unsteady simulation uses a fully resolved sliding grid approach. The comparisons show that the unsteady numerical results accurately predict the unsteadiness of the flow, demonstrating the validity and applicability of that methodology for unsteady incompressible turbomachinery flow computations. The steady approach is less accurate, with an unphysical advection of the impeller wakes, but accurate enough for a crude approximation. The different turbulence models predict the flow at the same level of accuracy, with slightly different results.
International Nuclear Information System (INIS)
Pryor, R.J.; Maloney, K.J.
1990-10-01
This document contains the steady-state and loss-of-pumping accident analysis of the representative design for the Savannah River heavy water new production reactor. A description of the reactor system and computer input model, the results of the steady-state analysis, and the results of four loss-of-pumping accident calculations are presented. 5 refs., 37 figs., 4 tabs
International Nuclear Information System (INIS)
Ferri, M. G.; D'Auria, F.; Forasassi, G.; Giot, M.
2000-01-01
BR2 is a material test reactor sited in the Belgian Nuclear Research Centre in Mol. The main research programs carried out in BR2 are related to the safety of nuclear reactor structural materials and fuels, in normal and accidental conditions, plant lifetime evaluation and ageing of components. In this framework, a computer program that allows the performance of detailed, steady state analysis of several kinds of in-pile sections with an axisymmetrical geometry has been developed. Furthermore, comparing its results with those of the well known, extensively used, Relap5/Mod 3.2 code on a test problem has validated this program. This was performed in three steps: 1. modalisation development of a subsystem of a typical in-pile section. 2. steady state analysis and comparison with the above-mentioned program. 3. transient simulation of the same system; the considered transient consists of a loss of coolant flow. (author)
Grandinetti, Lucio; Purnama, Anton
2015-01-01
Presenting the latest findings in the field of numerical analysis and optimization, this volume balances pure research with practical applications of the subject. Accompanied by detailed tables, figures, and examinations of useful software tools, this volume will equip the reader to perform detailed and layered analysis of complex datasets. Many real-world complex problems can be formulated as optimization tasks. Such problems can be characterized as large scale, unconstrained, constrained, non-convex, non-differentiable, and discontinuous, and therefore require adequate computational methods, algorithms, and software tools. These same tools are often employed by researchers working in current IT hot topics such as big data, optimization and other complex numerical algorithms on the cloud, devising special techniques for supercomputing systems. The list of topics covered include, but are not limited to: numerical analysis, numerical optimization, numerical linear algebra, numerical differential equations, opt...
Comparison of scale analysis and numerical simulation for saturated zone convective mixing processes
International Nuclear Information System (INIS)
Oldenburg, C.M.
1998-01-01
Scale analysis can be used to predict a variety of quantities arising from natural systems where processes are described by partial differential equations. For example, scale analysis can be applied to estimate the effectiveness of convective missing on the dilution of contaminants in groundwater. Scale analysis involves substituting simple quotients for partial derivatives and identifying and equating the dominant terms in an order-of-magnitude sense. For free convection due to sidewall heating of saturated porous media, scale analysis shows that vertical convective velocity in the thermal boundary layer region is proportional to the Rayleigh number, horizontal convective velocity is proportional to the square root of the Rayleigh number, and thermal boundary layer thickness is proportional to the inverse square root of the Rayleigh number. These scale analysis estimates are corroborated by numerical simulations of an idealized system. A scale analysis estimate of mixing time for a tracer mixing by hydrodynamic dispersion in a convection cell also agrees well with numerical simulation for two different Rayleigh numbers. Scale analysis for the heating-from-below scenario produces estimates of maximum velocity one-half as large as the sidewall case. At small values of the Rayleigh number, this estimate is confirmed by numerical simulation. For larger Rayleigh numbers, simulation results suggest maximum velocities are similar to the sidewall heating scenario. In general, agreement between scale analysis estimates and numerical simulation results serves to validate the method of scale analysis. Application is to radioactive repositories
Numerical analysis of a polysilicon-based resistive memory device
Berco, Dan; Chand, Umesh
2018-01-01
This study investigates a conductive bridge resistive memory device based on a Cu top electrode, 10-nm polysilicon resistive switching layer and a TiN bottom electrode, by numerical analysis for $$10^{3}$$103 programming and erase simulation cycles
International Nuclear Information System (INIS)
Wang, Xiaoliang; Lei, Bo; Bi, Haiquan; Yu, Tao
2017-01-01
Highlights: • A simplified method for evaluating thermal performance of UTC is developed. • Experiments, numerical simulations, dimensional analysis and data fitting are used. • The correlation of absorber plate temperature for UTC is established. • The empirical correlation of heat exchange effectiveness for UTC is proposed. - Abstract: Due to the advantages of low investment and high energy efficiency, unglazed transpired solar collectors (UTC) have been widely used for heating in buildings. However, it is difficult for designers to quickly evaluate the thermal performance of UTC based on the conventional methods such as experiments and numerical simulations. Therefore, a simple and fast method to determine the thermal performance of UTC is indispensable. The objective of this work is to provide a simplified calculation method to easily evaluate the thermal performance of UTC under steady state. Different parameters are considered in the simplified method, including pitch, perforation diameter, solar radiation, solar absorptivity, approach velocity, ambient air temperature, absorber plate temperature, and so on. Based on existing design parameters and operating conditions, correlations for the absorber plate temperature and the heat exchange effectiveness are developed using dimensional analysis and data fitting, respectively. Results show that the proposed simplified method has a high accuracy and can be employed to evaluate the collector efficiency, the heat exchange effectiveness and the air temperature rise. The proposed method in this paper is beneficial to directly determine design parameters and operating status for UTC.
On the calculation of steady-state loss probabilities in the GI/G/2/0 queue
Directory of Open Access Journals (Sweden)
Igor N. Kovalenko
1994-01-01
Full Text Available This paper considers methods for calculating the steady-state loss probability in the GI/G/2/0 queue. A previous study analyzed this queue in discrete time and this led to an efficient, numerical approximation scheme for continuous-time systems. The primary aim of the present work is to provide an alternative approach by analyzing the GI/ME/2/0 queue; i.e., assuming that the service time can be represented by a matrix-exponential distribution. An efficient computational scheme based on this method is developed and some numerical examples are studied. Some comparisons are made with the discrete-time approach, and the two methods are seen to be complementary.
Dissipative dark matter halos: The steady state solution
Foot, R.
2018-02-01
Dissipative dark matter, where dark matter particle properties closely resemble familiar baryonic matter, is considered. Mirror dark matter, which arises from an isomorphic hidden sector, is a specific and theoretically constrained scenario. Other possibilities include models with more generic hidden sectors that contain massless dark photons [unbroken U (1 ) gauge interactions]. Such dark matter not only features dissipative cooling processes but also is assumed to have nontrivial heating sourced by ordinary supernovae (facilitated by the kinetic mixing interaction). The dynamics of dissipative dark matter halos around rotationally supported galaxies, influenced by heating as well as cooling processes, can be modeled by fluid equations. For a sufficiently isolated galaxy with a stable star formation rate, the dissipative dark matter halos are expected to evolve to a steady state configuration which is in hydrostatic equilibrium and where heating and cooling rates locally balance. Here, we take into account the major cooling and heating processes, and numerically solve for the steady state solution under the assumptions of spherical symmetry, negligible dark magnetic fields, and that supernova sourced energy is transported to the halo via dark radiation. For the parameters considered, and assumptions made, we were unable to find a physically realistic solution for the constrained case of mirror dark matter halos. Halo cooling generally exceeds heating at realistic halo mass densities. This problem can be rectified in more generic dissipative dark matter models, and we discuss a specific example in some detail.
Elucidation of self-induced sloshing occurrence mechanism using numerical analysis
International Nuclear Information System (INIS)
Saeki, Soichi; Madarame, Haruki; Okamoto, Koji; Tanaka, Nobukazu.
1995-01-01
In liquid metal-cooled fast breeder reactors, there is free liquid surface in a reactor vessel and others, and by reducing the size of the reactor vessel and others, it is necessary to increase the flow velocity of liquid sodium coolant. In the free liquid surface in which fast circulating flow exists, undesirable phenomena like waving and bubble catching are feared. The self-induced sloshing taken up in this study is one of these phenomena. Since the actual machine has complex three-dimensional structure, in order to forecast the occurrence of sloshing, it is necessary to elucidate the mechanism of vibration occurrence. The mechanism of occurrence of self-induced sloshing due to horizontal and vertical plane jets has been explained a number of times so far. In this study, by applying the model of the occurrence mechanism of Fukaya to horizontal plane jet, the self-induced sloshing due to horizontal plane jet was simulated by numerical analysis. Based on the results, it was attempted to examine the vibration energy supplied to sloshing in a whole flow field and the dependence of sloshing region on water depth and flow velocity. The numerical simulation, the analysis of the occurrence mechanism by using the numerical analysis code and the results are reported. (K.I.)
Chin, Jeffrey C.; Csank, Jeffrey T.; Haller, William J.; Seidel, Jonathan A.
2016-01-01
This document outlines methodologies designed to improve the interface between the Numerical Propulsion System Simulation framework and various control and dynamic analyses developed in the Matlab and Simulink environment. Although NPSS is most commonly used for steady-state modeling, this paper is intended to supplement the relatively sparse documentation on it's transient analysis functionality. Matlab has become an extremely popular engineering environment, and better methodologies are necessary to develop tools that leverage the benefits of these disparate frameworks. Transient analysis is not a new feature of the Numerical Propulsion System Simulation (NPSS), but transient considerations are becoming more pertinent as multidisciplinary trade-offs begin to play a larger role in advanced engine designs. This paper serves to supplement the relatively sparse documentation on transient modeling and cover the budding convergence between NPSS and Matlab based modeling toolsets. The following sections explore various design patterns to rapidly develop transient models. Each approach starts with a base model built with NPSS, and assumes the reader already has a basic understanding of how to construct a steady-state model. The second half of the paper focuses on further enhancements required to subsequently interface NPSS with Matlab codes. The first method being the simplest and most straightforward but performance constrained, and the last being the most abstract. These methods aren't mutually exclusive and the specific implementation details could vary greatly based on the designer's discretion. Basic recommendations are provided to organize model logic in a format most easily amenable to integration with existing Matlab control toolsets.
Numerical and experimental study on the steady cone-jet mode of electro-centrifugal spinning
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.
International Nuclear Information System (INIS)
Yu, Shengzhi; Wang, Jianjun; Yan, Ming; Yan, Changqi; Cao, Xiaxin
2017-01-01
Highlights: • The phasic difference between flow rate and frictional pressure drop is negligible. • Effect mechanism of rolling motion on flow behaviors of NC is interpreted. • The startup model is proposed and verified. • Steady-state correlations are feasible to predict transient resistance. • The in-house code can simulate instantaneous flow behaviors of NC correctly. - Abstract: Effects of rolling motion on flow characteristics in a natural circulation system were investigated experimentally and numerically. The numerical results from validated code were mainly used to provide detailed information for the discussion and analysis of experimental results. The results indicate that under rolling motion condition, the phasic difference between flow rate and frictional pressure drop of narrow rectangular channel is negligible. Angular acceleration is the eigenvalue for the effects of rolling motion on flow rate under single-phase natural circulation condition. When angular acceleration is approximately equal, even though either the angle or the period of rolling motion is different, peak, trough and time-averaged values of flow rate are approximately equal. Under rolling motion and single-phase natural circulation conditions, the phenomenon that dimensionless time-averaged mass flow rate is smaller than that under steady state condition is controlled by the nonlinear relationship between mass flow rate and the resistance of loop. The factor also causes the result that the absolute difference of dimensionless flow rate between peak and steady state is smaller than that between trough and steady state. The startup model which is proposed in present paper can be used to predict the flow characteristics of single-phase natural circulation system at startup stage of rolling motion favorably. The self-developed code can simulate instantaneous flow characteristics of single-phase natural circulation system under rolling motion and steady state conditions
Energy Technology Data Exchange (ETDEWEB)
Brasil, Cristiana S.; Valle, Ramon M.; Cortez, Marcio F.B.; Ferreira, Andre G. [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Dept. de Engenharia Mecanica]. E-mail: tite@demec.ufmg.br; ramon@demec.ufmg.br; fonteboa@demec.ufmg.br; ferreira@demec.ufmg.br
2000-07-01
This paper presents a theoretical analysis of the turbulent natural convection in a solar chimney operating in steady flow, with prescribed conditions of temperature in the ground. The solar radiation heats the air under the cover, which flows to the tower without artificial pumping. The hot air produced may be used to dry several agricultural products. The numerical analysis of the natural convection in this kind of dryer has fundamental importance on the design and building of this device. The mathematical model includes the conservation laws for mass, momentum and thermal energy and the transport equations for the turbulence model variables (k and e ). The k- e model of turbulence with wall functions was used. A computational code using the Finite Volume Method in Generalized Coordinates was developed to solve the system of equations that describes thermal and hydro dynamically the flow. The velocity and temperature fields are shown to the flow in the solar chimney. With geometrical alterations on the device, one can obtain a detailed description of the flow, which allow the guideline for a suitable configuration to build an experimental prototype. (author)
Fully anisotropic goal-oriented mesh adaptation for 3D steady Euler equations
Loseille, A.; Dervieux, A.; Alauzet, F.
2010-04-01
This paper studies the coupling between anisotropic mesh adaptation and goal-oriented error estimate. The former is very well suited to the control of the interpolation error. It is generally interpreted as a local geometric error estimate. On the contrary, the latter is preferred when studying approximation errors for PDEs. It generally involves non local error contributions. Consequently, a full and strong coupling between both is hard to achieve due to this apparent incompatibility. This paper shows how to achieve this coupling in three steps. First, a new a priori error estimate is proved in a formal framework adapted to goal-oriented mesh adaptation for output functionals. This estimate is based on a careful analysis of the contributions of the implicit error and of the interpolation error. Second, the error estimate is applied to the set of steady compressible Euler equations which are solved by a stabilized Galerkin finite element discretization. A goal-oriented error estimation is derived. It involves the interpolation error of the Euler fluxes weighted by the gradient of the adjoint state associated with the observed functional. Third, rewritten in the continuous mesh framework, the previous estimate is minimized on the set of continuous meshes thanks to a calculus of variations. The optimal continuous mesh is then derived analytically. Thus, it can be used as a metric tensor field to drive the mesh adaptation. From a numerical point of view, this method is completely automatic, intrinsically anisotropic, and does not depend on any a priori choice of variables to perform the adaptation. 3D examples of steady flows around supersonic and transsonic jets are presented to validate the current approach and to demonstrate its efficiency.
ULTRA-SHARP nonoscillatory convection schemes for high-speed steady multidimensional flow
Leonard, B. P.; Mokhtari, Simin
1990-01-01
For convection-dominated flows, classical second-order methods are notoriously oscillatory and often unstable. For this reason, many computational fluid dynamicists have adopted various forms of (inherently stable) first-order upwinding over the past few decades. Although it is now well known that first-order convection schemes suffer from serious inaccuracies attributable to artificial viscosity or numerical diffusion under high convection conditions, these methods continue to enjoy widespread popularity for numerical heat transfer calculations, apparently due to a perceived lack of viable high accuracy alternatives. But alternatives are available. For example, nonoscillatory methods used in gasdynamics, including currently popular TVD schemes, can be easily adapted to multidimensional incompressible flow and convective transport. This, in itself, would be a major advance for numerical convective heat transfer, for example. But, as is shown, second-order TVD schemes form only a small, overly restrictive, subclass of a much more universal, and extremely simple, nonoscillatory flux-limiting strategy which can be applied to convection schemes of arbitrarily high order accuracy, while requiring only a simple tridiagonal ADI line-solver, as used in the majority of general purpose iterative codes for incompressible flow and numerical heat transfer. The new universal limiter and associated solution procedures form the so-called ULTRA-SHARP alternative for high resolution nonoscillatory multidimensional steady state high speed convective modelling.
Directory of Open Access Journals (Sweden)
O.I. Pechonik
2006-03-01
Full Text Available Formation of conditions of transition to steady development of the credit organizations assumes presence of scientific toolkit which should have methodological character and represent a set of scientific receptions, methods and principles of research to which definition given clause is devoted. The executed research has shown, that the logic and the scheme of the scientific analysis of processes of maintenance with bank service of economic system of region and formation of conditions of steady development of regional bank system should: to be based on statistical methods with use of system of national accounts in addition with the SWOT-analysis of bank system; formation of conditions of transition to steady development to be spent in a complex and comprehensively; management of process of transition to steady development of bank system should be carried out at active state participation within the limits of creation socially focused according to plan-market economy. At the given approach formation of conditions of transition of regional bank system on steady development, in our opinion, becomes possible.
Numerical equilibrium analysis for structured consumer resource models.
de Roos, A M; Diekmann, O; Getto, P; Kirkilionis, M A
2010-02-01
In this paper, we present methods for a numerical equilibrium and stability analysis for models of a size structured population competing for an unstructured resource. We concentrate on cases where two model parameters are free, and thus existence boundaries for equilibria and stability boundaries can be defined in the (two-parameter) plane. We numerically trace these implicitly defined curves using alternatingly tangent prediction and Newton correction. Evaluation of the maps defining the curves involves integration over individual size and individual survival probability (and their derivatives) as functions of individual age. Such ingredients are often defined as solutions of ODE, i.e., in general only implicitly. In our case, the right-hand sides of these ODE feature discontinuities that are caused by an abrupt change of behavior at the size where juveniles are assumed to turn adult. So, we combine the numerical solution of these ODE with curve tracing methods. We have implemented the algorithms for "Daphnia consuming algae" models in C-code. The results obtained by way of this implementation are shown in the form of graphs.
Numerical analysis of a heat-generating, truncated conical porous bed in a fluid-filled enclosure
International Nuclear Information System (INIS)
Chakravarty, Aranyak; Datta, Priyankan; Ghosh, Koushik; Sen, Swarnendu; Mukhopadhyay, Achintya
2016-01-01
Analysis of natural convection in enclosures containing heat generating porous medium has important applications related to geothermal, chemical, thermal and nuclear energy such as in-vessel cooling of debris beds in nuclear reactors, cooling of coal stockpiles etc. The objective of the present numerical study is to characterise the pattern of fluid flow and energy transfer during steady laminar natural convective flow in a cylindrical enclosure with a centrally placed heat generating porous bed. Flow through porous region is modelled using Darcy–Brinkmann–Forchheimer model and local thermal equilibrium is assumed for the porous region. Analysis is carried out for a wide range of Rayleigh number (Ra), Darcy number (Da) and thermal conductivity ratio, as well as for different bed geometries. It is observed that in addition to Ra and Da, the bed geometry also plays a very important role in determining flow field and temperature distribution within the enclosure. Interestingly, a significant change is observed in energy transfer mode from the porous bed corresponding to specific values of bed permeability and bed heat generation rate. This is characterised in terms of Ra and Da. Further, it is observed that this change in energy transfer mode is highly dependent on Ra. - Highlights: • Natural convection is analysed in an enclosure with a heat generating porous bed. • Effect of dimensionless parameters as well as bed geometry has been investigated. • Energy transfer mechanism from porous bed changes with dimensionless parameters. • Bed geometry significantly affects fluid flow and energy transfer in the enclosure.
Sensitivity of a numerical wave model on wind re-analysis datasets
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.
Shiraishi, Emi; Maeda, Kazuhiro; Kurata, Hiroyuki
2009-02-01
Numerical simulation of differential equation systems plays a major role in the understanding of how metabolic network models generate particular cellular functions. On the other hand, the classical and technical problems for stiff differential equations still remain to be solved, while many elegant algorithms have been presented. To relax the stiffness problem, we propose new practical methods: the gradual update of differential-algebraic equations based on gradual application of the steady-state approximation to stiff differential equations, and the gradual update of the initial values in differential-algebraic equations. These empirical methods show a high efficiency for simulating the steady-state solutions for the stiff differential equations that existing solvers alone cannot solve. They are effective in extending the applicability of dynamic simulation to biochemical network models.
Heterogeneous agent model and numerical analysis of learning
Czech Academy of Sciences Publication Activity Database
Vošvrda, Miloslav; Vácha, Lukáš
2002-01-01
Roč. 9, č. 17 (2002), s. 15-22 ISSN 1212-074X R&D Projects: GA ČR GA402/01/0034; GA ČR GA402/01/0539; GA AV ČR IAA7075202 Institutional research plan: CEZ:AV0Z1075907 Keywords : efficient markets hypothesis * technical trading rules * numerical analysis of learning Subject RIV: AH - Economics
Polyhedral meshing in numerical analysis of conjugate heat transfer
Sosnowski, Marcin; Krzywanski, Jaroslaw; Grabowska, Karolina; Gnatowska, Renata
2018-06-01
Computational methods have been widely applied in conjugate heat transfer analysis. The very first and crucial step in such research is the meshing process which consists in dividing the analysed geometry into numerous small control volumes (cells). In Computational Fluid Dynamics (CFD) applications it is desirable to use the hexahedral cells as the resulting mesh is characterized by low numerical diffusion. Unfortunately generating such mesh can be a very time-consuming task and in case of complicated geometry - it may not be possible to generate cells of good quality. Therefore tetrahedral cells have been implemented into commercial pre-processors. Their advantage is the ease of its generation even in case of very complex geometry. On the other hand tetrahedrons cannot be stretched excessively without decreasing the mesh quality factor, so significantly larger number of cells has to be used in comparison to hexahedral mesh in order to achieve a reasonable accuracy. Moreover the numerical diffusion of tetrahedral elements is significantly higher. Therefore the polyhedral cells are proposed within the paper in order to combine the advantages of hexahedrons (low numerical diffusion resulting in accurate solution) and tetrahedrons (rapid semi-automatic generation) as well as to overcome the disadvantages of both the above mentioned mesh types. The major benefit of polyhedral mesh is that each individual cell has many neighbours, so gradients can be well approximated. Polyhedrons are also less sensitive to stretching than tetrahedrons which results in better mesh quality leading to improved numerical stability of the model. In addition, numerical diffusion is reduced due to mass exchange over numerous faces. This leads to a more accurate solution achieved with a lower cell count. Therefore detailed comparison of numerical modelling results concerning conjugate heat transfer using tetrahedral and polyhedral meshes is presented in the paper.
ANTEO: An optimised PC computer code for the steady state thermal hydraulic analysis of rod bundles
International Nuclear Information System (INIS)
Cevolani, S.
1996-07-01
The paper deals with the description of a Personal Computer oriented subchannel code, devoted to the steady state thermal hydraulic analysis of nuclear reactor fuel bundles. The development of a such code was made possible by two facts: first, the increase the computing power of the desk machines; secondly, the fact several years of experience into operate subchannels codes have shown how to simplify many of the physical models without a sensible loss of accuracy. For sake of validation, the developed code was compared with a traditional subchannel code, the COBRA one. The results of the comparison show a very good agreement between the two codes
Analysis of Spatiotemporal Dynamic and Bifurcation in a Wetland Ecosystem
Directory of Open Access Journals (Sweden)
Yi Wang
2015-01-01
Full Text Available A wetland ecosystem is studied theoretically and numerically to reveal the rules of dynamics which can be quite accurate to better describe the observed spatial regularity of tussock vegetation. Mathematical theoretical works mainly investigate the stability of constant steady states, the existence of nonconstant steady states, and bifurcation, which can deduce a standard parameter control relation and in return can provide a theoretical basis for the numerical simulation. Numerical analysis indicates that the theoretical works are correct and the wetland ecosystem can show rich dynamical behaviors not only regular spatial patterns. Our results further deepen and expand the study of dynamics in the wetland ecosystem. In addition, it is successful to display tussock formation in the wetland ecosystem may have important consequences for aquatic community structure, especially for species interactions and biodiversity. All these results are expected to be useful in the study of the dynamic complexity of wetland ecosystems.
Karamanis, N.; Palfreyman, D.; Arcoumanis, C.; Martinez-Botas, R. F.
2006-07-01
experiment performance and LDV measurements. With the steady inlet boundary condition, a high level of accuracy was achieved when compared to the experimental performance and velocity field. The velocity along the leading edge showed the same discrepancy as the single passage analysis that is with the radial and axial component from mid span to the blade tip. At the trailing edge features identified in the experimental data are identified in the numerical results; the velocity field appears more 'diffused' across the plane as per the experimental data than from the single passage analysis. With the pulsating inlet boundary, the predicted velocity traces in the volute and close to the turbine lead and trailing edge show excellent agreement in both form (against time) and magnitude.
Directory of Open Access Journals (Sweden)
Fei Fan
2017-08-01
Full Text Available Rigid-lid approximation is usually used to replace the free surface in scour simulation. The influence of the rigid lid assumption on the prediction precision of scour hole in steady flow is studied in this paper. Firstly, a local scour model was constructed based on the open sources Computational Fluid Dynamics (CFD model OpenFOAM, where both the bed load and suspended load were considered. In the present model, the bed shear stress was calculated by the Newton shear stress formula, instead of the traditional calculation method with the assumption that the flow velocity in vertical direction complies with a logarithmic distribution. The Volume of Fluid (VOF method was used to capture the free surface and a moving-mesh method was used to track the change of bed surface. Then, several experiments were chosen to validate the model, and the modeling results fitted well with the measured data. Lastly, the effect of the rigid lid assumption on surface elevation, bed shear stress and the profile of the scour hole in steady flow are studied. The result shows that the surface elevation suffers a drop above the pipeline, and the difference of surface elevation between the upstream and downstream increases with decreasing dimensionless depth. Compared with the free surface condition, the bed shear stress and scour hole depth computed with the rigid lid approximation were underestimated.
Numerical simulation of flow fields and particle trajectories
DEFF Research Database (Denmark)
Mayer, Stefan
2000-01-01
. The time-dependent flow is approximated with a continuous sequence of steady state creeping flow fields, where metachronously beating ciliary bands are modelled by linear combinations of singularity solutions to the Stokes equations. Generally, the computed flow fields can be divided into an unsteady......A model describing the ciliary driven flow and motion of suspended particles in downstream suspension feeders is developed. The quasi-steady Stokes equations for creeping flow are solved numerically in an unbounded fluid domain around cylindrical bodies using a boundary integral formulation...... in the simulated unsteady ciliary driven flow. A fraction of particles appear to follow trajectories, that resemble experimentally observed particle capture events in the downstream feeding system of the polycheate Sabella penicillus, indicating that particles can be captured by ciliary systems without mechanical...
Diffusion-driven steady states of the Z-pinch
International Nuclear Information System (INIS)
Lehnert, B.
1988-01-01
Steady states of a Z-pinch where no electric field is imposed along the pinch axis by external means are investigated. In this case, diffusion-driven states become possible when imposed volume sources of particles and heat drive a radial diffusion velocity that, in its turn, generates the electric plasma current. The particle sources can be from pellet injection or a neutral gas blanket, and the heat sources provided by thermonuclear reactions or auxiliary heating. The present analysis and associated kinetic considerations indicate that steady diffusion-driven operation should become possible for certain classes of plasma profiles, without running into singularity problems at the pinch axis. Such operation leads to higher axial currents in a Z-pinch without an axial magnetic field than in a tokamaklike case under similar plasma conditions. The technical difficulty in realizing a volume distribution of particle sinks introduces certain constraints on the plasma and current profiles. This fact has to be taken into account in a stability analysis. Neoclassical or anomalous diffusion will increase the diffusion velocity of the plasma but is not expected to affect the main physical features of the present results
Numerical Limit Analysis of Precast Concrete Structures
DEFF Research Database (Denmark)
Herfelt, Morten Andersen
Precast concrete elements are widely used in the construction industry as they provide a number of advantages over the conventional in-situ cast concrete structures. Joints cast on the construction site are needed to connect the precast elements, which poses several challenges. Moreover, the curr...... problems are solved efficiently using state-of-the-art solvers. It is concluded that the framework and developed joint models have the potential to enable efficient design of precast concrete structures in the near future......., the current practice is to design the joints as the weakest part of the structure, which makes analysis of the ultimate limit state behaviour by general purpose software difficult and inaccurate. Manual methods of analysis based on limit analysis have been used for several decades. The methods provide...... of the ultimate limit state behaviour. This thesis introduces a framework based on finite element limit analysis, a numerical method based on the same extremum principles as the manual limit analysis. The framework allows for efficient analysis and design in a rigorous manner by use of mathematical optimisation...
Ratto, Luca; Satta, Francesca; Tanda, Giovanni
2018-06-01
This paper presents an experimental and numerical investigation of heat transfer in the endwall region of a large scale turbine cascade. The steady-state liquid crystal technique has been used to obtain the map of the heat transfer coefficient for a constant heat flux boundary condition. In the presence of two- and three-dimensional flows with significant spatial variations of the heat transfer coefficient, tangential heat conduction could lead to error in the heat transfer coefficient determination, since local heat fluxes at the wall-to-fluid interface tend to differ from point to point and surface temperatures to be smoothed out, thus making the uniform-heat-flux boundary condition difficult to be perfectly achieved. For this reason, numerical simulations of flow and heat transfer in the cascade including the effect of tangential heat conduction inside the endwall have been performed. The major objective of numerical simulations was to investigate the influence of wall heat conduction on the convective heat transfer coefficient determined during a nominal iso-flux heat transfer experiment and to interpret possible differences between numerical and experimental heat transfer results. Results were presented and discussed in terms of local Nusselt number and a convenient wall heat flux function for two values of the Reynolds number (270,000 and 960,000).
Electrokinetic Particle Transport in Micro-Nanofluidics Direct Numerical Simulation Analysis
Qian, Shizhi
2012-01-01
Numerous applications of micro-/nanofluidics are related to particle transport in micro-/nanoscale channels, and electrokinetics has proved to be one of the most promising tools to manipulate particles in micro/nanofluidics. Therefore, a comprehensive understanding of electrokinetic particle transport in micro-/nanoscale channels is crucial to the development of micro/nano-fluidic devices. Electrokinetic Particle Transport in Micro-/Nanofluidics: Direct Numerical Simulation Analysis provides a fundamental understanding of electrokinetic particle transport in micro-/nanofluidics involving elect
Steady-State Creep of Asphalt Concrete
Directory of Open Access Journals (Sweden)
Alibai Iskakbayev
2017-02-01
Full Text Available This paper reports the experimental investigation of the steady-state creep process for fine-grained asphalt concrete at a temperature of 20 ± 2 °С and under stress from 0.055 to 0.311 MPa under direct tension and was found to occur at a constant rate. The experimental results also determined the start, the end point, and the duration of the steady-state creep process. The dependence of these factors, in addition to the steady-state creep rate and viscosity of the asphalt concrete on stress is satisfactorily described by a power function. Furthermore, it showed that stress has a great impact on the specific characteristics of asphalt concrete: stress variation by one order causes their variation by 3–4.5 orders. The described relations are formulated for the steady-state of asphalt concrete in a complex stressed condition. The dependence is determined between stress intensity and strain rate intensity.
Maneuverability of Ships with small Draught in Steady Wind
Directory of Open Access Journals (Sweden)
Daeng Paroka
2016-04-01
Full Text Available Wind force and moment may force a ship to drastically decrease its speed and use a large drift angle as well as a large rudder angle in order to maintain its course. Shipswith a small draught might have more risk in maneuvering to its point of view compared with a ship with a larger draught. This paper discusses maneuverability of a ship with a small draught in steady wind. The effect of wind on ship speed, drift angle, and rudder angle are investigated in a steady state condition. Five different ratios of wind velocity to ship speed from 1.0 to 20.0 are used in the simulation. The variation in wind direction is examined from 0°to 180°. Results of the numerical simulation show that thewind has a significant effect on the reduction in ship speed with a wind direction less than 100°. The drift angle increases due to increasing wind velocity in the same wind direction. Wind direction also has a significant effect on the drift angle especially when the wind direction is less than 140°. The same phenomenon was found for the rudder angle. The necessary rudder angle is greater than the maximum rudder angle of the ship when the wind direction is 60°with a wind velocity to ship speed ratio of 20 or more.
Quasi-Steady Evolution of Hillslopes in Layered Landscapes: An Analytic Approach
Glade, R. C.; Anderson, R. S.
2018-01-01
Landscapes developed in layered sedimentary or igneous rocks are common on Earth, as well as on other planets. Features such as hogbacks, exposed dikes, escarpments, and mesas exhibit resistant rock layers adjoining more erodible rock in tilted, vertical, or horizontal orientations. Hillslopes developed in the erodible rock are typically characterized by steep, linear-to-concave slopes or "ramps" mantled with material derived from the resistant layers, often in the form of large blocks. Previous work on hogbacks has shown that feedbacks between weathering and transport of the blocks and underlying soft rock can create relief over time and lead to the development of concave-up slope profiles in the absence of rilling processes. Here we employ an analytic approach, informed by numerical modeling and field data, to describe the quasi-steady state behavior of such rocky hillslopes for the full spectrum of resistant layer dip angles. We begin with a simple geometric analysis that relates structural dip to erosion rates. We then explore the mechanisms by which our numerical model of hogback evolution self-organizes to meet these geometric expectations, including adjustment of soil depth, erosion rates, and block velocities along the ramp. Analytical solutions relate easily measurable field quantities such as ramp length, slope, block size, and resistant layer dip angle to local incision rate, block velocity, and block weathering rate. These equations provide a framework for exploring the evolution of layered landscapes and pinpoint the processes for which we require a more thorough understanding to predict their evolution over time.
Directory of Open Access Journals (Sweden)
Yu.L. Sayenko
2016-05-01
Full Text Available Purpose. Perform numerical analysis of the distribution of the factual contributions of line sources of distortion in the voltage distortion at the point of common coupling, based on the principles of superposition and exclusions. Methodology. Numerical analysis was performed on the results of the simulation steady state operation of power supply system of seven electricity consumers. Results. Mathematical model for determining the factual contribution of line sources of distortion in the voltage distortion at the point of common coupling, based on the principles of superposition and exclusions, are equivalent. To assess the degree of participation of each source of distortion in the voltage distortion at the point of common coupling and distribution of financial compensation to the injured party by all sources of distortion developed a one-dimensional criteria based on the scalar product of vectors. Not accounting group sources of distortion, which belong to the subject of the energy market, to determine their total factual contribution as the residual of the factual contribution between all sources of distortion. Originality. Simulation mode power supply system was carried out in the phase components space, taking into account the distributed characteristics of distortion sources. Practical value. The results of research can be used to develop methods and tools for distributed measurement and analytical systems assessment of the power quality.
International Nuclear Information System (INIS)
Baptista Filho, Benedito Dias
1979-01-01
A numerical model has been developed to calculate the flow, pressure and temperature distribution of steady-state |for the tube and shell-side fluids in a shell-and-U-tubes heat exchanger with segmental baffles. It was based on the Subchannel Analysis Method- The model, checked with experimental results from one heat exchanger, predicted with good accuracy outlet temperatures for both fluids. The method, implemented ' in a computer program of low cost and easy application, can be used in the design and performance evaluation of commercial units.(author)
A simple analysis of the stable field profile in the supercritical TEA
DEFF Research Database (Denmark)
Jeppesen, Palle; Jeppsson, B.
1973-01-01
An analytical investigation supported by numerical calculations has been performed of the stable field profile in a supercritical diffusion-stabilized n-GaAs transferred electron amplifier (TEA) with ohmic contacts. In the numerical analysis, the field profile is determined by solving the steady......}{2}} (n_{0}L)^{frac{1}{2}}. Those results contribute to the understanding of the highn_{0}L-product switch and the stability of the supercritical TEA....
Numerical study on air turbines with enhanced techniques for OWC wave energy conversion
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.
Numerical analysis of the influence of circuit arrangement on a fin-and-tube condenser performance
Directory of Open Access Journals (Sweden)
Cesare Maria Joppolo
2015-09-01
Full Text Available In the present paper a model for the steady-state simulation of fin-and-tube condenser is developed. The model is based on a finite volume approach that divides each tube into small elemental volumes where mass, momentum and energy conservation equations are solved using the effectiveness-NTU method and with appropriate correlations for void fraction, friction factor and heat transfer coefficient calculation. The model is validated against experimental data on two small condensers finding that the calculated heat transfer rate and refrigerant-side pressure drop agree within ±5% and ±21% respectively to the experimental values. The model is then used to numerically analyse the impact of different circuit arrangements on the condenser heat transfer rate, refrigerant-side pressure drop and refrigerant charge.
Contributions to mathematical analysis and to numerical approximation in plasma physics
International Nuclear Information System (INIS)
Besse, N.
2009-01-01
The author's scientific works deal with numerical analysis and the simulation of the partial differential equations that intervene in the transport of charged particles and in plasma physics. In the chapters 2 and 3, a reduction of the Vlasov equation is presented, this method is based on the Liouville geometric invariants and it leads to a mathematical model named water-bag model that can be coupled with various equations of the electromagnetic field: the Poisson equation, the quasi-neutral equation or Maxwell equations. In the chapter 3 this reduction method is applied to the Vlasov gyro-kinetic equation to form the gyro-water-bag model. The mathematical analysis of this model produces interesting analytical results such as: threshold instabilities, instability growth rate, transport coefficient and non-linear turbulence mechanisms. Simulations have been performed to study turbulence in magnetized plasmas. In these plasmas occurred numerous instabilities due to the presence of high density and temperature gradients. These instabilities generate turbulence that deteriorates plasma confinement conditions required for thermonuclear fusion. The numerical calculation of turbulent thermal diffusivities is important since confinement time is determined by these transport coefficients. The chapter 4 gathers mathematical analysis issues like convergence or prior knowledge of errors concerning several high-order numerical methods used to solve Vlasov-Poisson or Vlasov-Einstein equation systems as well as the induction equation of an idealistic MHD system. The chapter 5 presents original numerical methods to solve several non-linear Vlasov equations such as Vlasov-Poisswell, Vlasov-Darwin, Vlasov-Maxwell and Vlasov-gyrokinetic that are involved either in inertial fusion or in magnetic confinement fusion
Energy Technology Data Exchange (ETDEWEB)
Hurtado, F. J.; Kaiser, A. S.; Zamora, B.; Lucas, M.; Viedma, A.
2008-07-01
A thermodynamic analysis for solar chimney power plant has been carried out by numerical simulation. A numerical model has been developed using the general purpose code Fluent to study heat transfer and convective flow within the chimney power plant. The {kappa}-{epsilon} turbulence model has been employed. A heat transfer, mass flow and power production numerical analysis has been carried out on different hours during the day, assuming steady state conditions. The numeric values obtained are 10% different from experimental measures. Once model has been validated, a numeric study about flow within power plant, heat transfer and mass flow has been carry out, and the non-dimensional parameters obtained have been compared with studies about free convection. (Author)
State of the art in numerical simulation of high head Francis turbines
Directory of Open Access Journals (Sweden)
Trivedi Chirag
2016-01-01
Full Text Available The Francis-99 test case consists in a high head Francis turbine model, which geometry together with meshes and detailed experimental measurements is freely available at www.francis-99.org. Three workshops were initially planned to exchange experience on numerical investigations of the test case concerning steady state operating conditions, transient operating conditions and fluid structure analysis. The first workshop was held in Trondheim, Norway in December 2014. Some results of the 14 contributions are presented. They are concerned with the influence of the near wall space discretization and turbulence modelling in order to capture hydraulic efficiency, torque, pressure and velocity with a good uncertainty at three operating conditions.
On the generation of steady currents in a plasma cylinder using RF waves
International Nuclear Information System (INIS)
Hugrass, W.N.
1980-10-01
The generation of a steady current in a resistive plasma cylinder by means of a travelling wave magnetic field has been studied using the resistive MHD equations. The nonlinear initial-boundary value problem has been solved using a semi-Lagrangian two dimensional algorithm. The numerical code has been used to simulate the Synchromak experiment of Nagoya University. Hollow d.c. current profiles, similar to the experimental data, have been obtained. A simple analytical argument, of a more general nature, shows that classical resistive diffusion cannot lead to a more uniform current distribution
International Nuclear Information System (INIS)
Sirvydas, A.; Poskas, R.
2006-01-01
We present the results on numerical investigation of the local opposing mixed convection heat transfer in a vertical flat channel with symmetrical heating at low Reynolds numbers. Numerical two-dimensional simulation was performed for the same channel and for the same conditions as in the experiment using the FLUENT 6.1 code. The unsteady flow investigations were performed in airflow for the experimental conditions at the Reynolds number 2130 and Grashof number 6.2* 10 8 . Quasi-steady flow investigations were performed for two Reynolds numbers (2130 and 4310) and the Grashof number up to 3.1*10 9 in order to simulate the buoyancy effect on the flow structure. In both steady and quasi-steady modelling cases the results demonstrated that under the high buoyancy effect the chequerwise local circular flow took place near the heated walls. This made velocity profiles asymmetrical and caused pulsations of the wall temperature. Wall temperature had a pulsatory character, however, the resulting averaged values correlated rather well with experimental data for steady and quasi-steady cases for Re in = 2130. For Re in = 4310, the resulting averaged values for x/d e ≤25 correlated rather well with experimental data. When x/d e > 25, the difference between the experimental and the calculated wall temperature was increasing, increasing, possibly due to a steady flow and heat transfer modelling. (author)
Pre-steady-state Kinetics for Hydrolysis of Insoluble Cellulose by Cellobiohydrolase Cel7A
DEFF Research Database (Denmark)
Cruys-Bagger, Nicolaj; Olsen, Jens Elmerdahl; Præstgaard, Eigil
2012-01-01
The transient kinetic behavior of enzyme reactions prior to the establishment of steady state is a major source of mechanistic information, yet this approach has not been utilized for cellulases acting on their natural substrate, insoluble cellulose. Here, we elucidate the pre-steady-state regime...... for the exo-acting cellulase Cel7A using amperometric biosensors and an explicit model for processive hydrolysis of cellulose. This analysis allows the identification of a pseudo-steady-state period and quantification of a processivity number as well as rate constants for the formation of a threaded enzyme...... to unveil fundamental reasons for the distinctive variability in hydrolytic activity found in different cellulase-substrate systems....
Assessment of Available Numerical Tools for Dynamic Mooring Analysis
DEFF Research Database (Denmark)
Thomsen, Jonas Bjerg; Eskilsson, Claes; Ferri, Francesco
This report covers a preliminary assessment of available numerical tools to be used in upcoming full dynamic analysis of the mooring systems assessed in the project _Mooring Solutions for Large Wave Energy Converters_. The assessments tends to cover potential candidate software and subsequently c...
MARS input data for steady-state calculation of ATLAS
International Nuclear Information System (INIS)
Park, Hyun Sik; Euh, D. J.; Choi, K. Y.; Kwon, T. S.; Jeong, J. J.; Baek, W. P.
2004-12-01
An integral effect test loop for Pressurized Water Reactors (PWRs), the ATLAS (Advanced Thermal-hydraulic Test Loop for Accident Simulation), is under construction by Thermal-Hydraulics Safety Research Division in Korea Atomic Energy Research Institute (KAERI). This report includes calculation sheets of the input for the best-estimate system analysis code, the MARS code, based on the ongoing design features of ATLAS. The ATLAS facility has been designed to have the length scale of 1/2 and area scale of 1/144 compared with the reference plant, APR1400. The contents of this report are divided into three parts: (1) core and reactor vessel, (2) steam generator and steam line, and (3) primary piping, pressurizer and reactor coolant pump. The steady-state analysis for the ATLAS facility will be performed based on these calculation sheets, and its results will be applied to the detailed design of ATLAS. Additionally, the calculation results will contribute to getting optimum test conditions and preliminary operational test conditions for the steady-state and transient experiments
Numerical analysis on pool boiling using user defined function
Energy Technology Data Exchange (ETDEWEB)
Ryu, Sung Uk; Jeon, Byong Guk; Kim, Seok; Euh, Dong-Jin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)
2015-10-15
PAFS (passive auxiliary feedwater system) adopted in the APR+ (Advanced Power Reactor Plus) of Korea is one such application. When PAFS is activated with an actuation signal, steam from the steam generator passes through heat exchanger tubes submerged in a water tank of the PAFS. Outside these heat exchanger tubes, nucleate boiling phenomena appears. In the present work, a numerical study is reported on three-dimensional transient state pool boiling of water having an immersed heat source. The velocity vector fields during the decrease in the water level are numerically investigated in a pool, and the accuracy of the results is checked by comparing the experimental results conducted using the PIV techniques by Kim et al. These numerical results can be used as basic research data for an analysis and prediction of the natural circulation phenomena in the cooling tank of the passive safety system in a nuclear power plant.
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.
Extracting Steady State Components from Synchrophasor Data Using Kalman Filters
Directory of Open Access Journals (Sweden)
Farhan Mahmood
2016-04-01
Full Text Available Data from phasor measurement units (PMUs may be exploited to provide steady state information to the applications which require it. As PMU measurements may contain errors and missing data, the paper presents the application of a Kalman Filter technique for real-time data processing. PMU data captures the power system’s response at different time-scales, which are generated by different types of power system events; the presented Kalman Filter methods have been applied to extract the steady state components of PMU measurements that can be fed to steady state applications. Two KF-based methods have been proposed, i.e., a windowing-based KF method and “the modified KF”. Both methods are capable of reducing noise, compensating for missing data and filtering outliers from input PMU signals. A comparison of proposed methods has been carried out using the PMU data generated from a hardware-in-the-loop (HIL experimental setup. In addition, a performance analysis of the proposed methods is performed using an evaluation metric.
An Adsorption Equilibria Model for Steady State Analysis
Ismail, Azhar Bin
2016-02-29
The investigation of adsorption isotherms is a prime factor in the ongoing development of adsorption cycles for a spectrum of advanced, thermally-driven engineering applications, including refrigeration, natural gas storage, and desalination processes. In this work, a novel semi-empirical mathematical model has been derived that significantly enhances the prediction of the steady state uptake in adsorbent surfaces. This model, a combination of classical Langmuir and a novel modern adsorption isotherm equation, allows for a higher degree of regression of both energetically homogenous and heterogeneous adsorbent surfaces compared to several isolated classical and modern isotherm models, and has the ability to regress isotherms for all six types under the IUPAC classification. Using a unified thermodynamic framework, a single asymmetrical energy distribution function (EDF) has also been proposed that directly relates the mathematical model to the adsorption isotherm types. This fits well with the statistical rate theory approach and offers mechanistic insights into adsorption isotherms.
Numeric computation and statistical data analysis on the Java platform
Chekanov, Sergei V
2016-01-01
Numerical computation, knowledge discovery and statistical data analysis integrated with powerful 2D and 3D graphics for visualization are the key topics of this book. The Python code examples powered by the Java platform can easily be transformed to other programming languages, such as Java, Groovy, Ruby and BeanShell. This book equips the reader with a computational platform which, unlike other statistical programs, is not limited by a single programming language. The author focuses on practical programming aspects and covers a broad range of topics, from basic introduction to the Python language on the Java platform (Jython), to descriptive statistics, symbolic calculations, neural networks, non-linear regression analysis and many other data-mining topics. He discusses how to find regularities in real-world data, how to classify data, and how to process data for knowledge discoveries. The code snippets are so short that they easily fit into single pages. Numeric Computation and Statistical Data Analysis ...
Application of symplectic integrator to numerical fluid analysis
International Nuclear Information System (INIS)
Tanaka, Nobuatsu
2000-01-01
This paper focuses on application of the symplectic integrator to numerical fluid analysis. For the purpose, we introduce Hamiltonian particle dynamics to simulate fluid behavior. The method is based on both the Hamiltonian formulation of a system and the particle methods, and is therefore called Hamiltonian Particle Dynamics (HPD). In this paper, an example of HPD applications, namely the behavior of incompressible inviscid fluid, is solved. In order to improve accuracy of HPD with respect to space, CIVA, which is a highly accurate interpolation method, is combined, but the combined method is subject to problems in that the invariants of the system are not conserved in a long-time computation. For solving the problems, symplectic time integrators are introduced and the effectiveness is confirmed by numerical analyses. (author)
International Nuclear Information System (INIS)
Zhong Yun; Zhang Jige; Wang Dezhong; Shi Jianzhong
2010-01-01
The Computational Fluid Dynamics (CFD) method is employed to simulate numerically the steady flow and transient flow under variable openings of the nuclear safety grade 2 single-seat pneumatic diaphragm control valve, which is a sleeve valve. The steady simulations under rated condition tells that there is a large amount of vortex in the valve seat necking and around the valve cone, which leads to a much greater flow impact on the head of the valve cone and uneven pressure distribution on spool face. More consideration should be taken on the characteristics of the valve cone accordingly, when designing a valve of this kind. Then the transient flow under 100% and 40% openings is simulated numerically on the basis of steady simulations. The pulsation of the pressure magnitude at the points with large vorticity, in the valve seat necking and around the valve cone, is monitored. The main pulsation frequencies differ from the low natural frequencies of the model, which means that it is safe from leading to structural resonance. (authors)
Four generations versus left-right symmetry. A comparative numerical analysis
International Nuclear Information System (INIS)
Heidsieck, Tillmann J.
2012-01-01
In this work, we present a comparative numerical analysis of the Standard Model (SM) with a sequential fourth generation (SM4) and the left-right symmetric Standard model (LRM). We focus on the constraints induced by flavour violating ΔF=2 processes in the K and B system while the results of studies of collider bounds and electroweak precision tests are taken into account as external inputs. In contrast to many previous studies of both models considered in this work, we do make not any ad-hoc assumptions on the structure of the relevant mixing matrices. Therefore, we employ powerful Monte Carlo methods in order to approximate the viable parameter space of the models. In preparation of our numerical analysis, we present all relevant formulae and review the different numerical methods used in this work. In order to better understand the patterns of new effects in ΔF=2 processes, we perform a fit including all relevant ΔF=2 constraints in the context of the Standard Model. The result of this fit is then used in a general discussion on new effects in ΔF=2 processes in the context of generic extensions of the Standard Model. Our numerical analysis of the SM4 and the LRM demonstrates that in both models the existing anomalies in Δ=2 processes can easily be resolved. We transparently show how the different observables are connected to each other by their dependence on combinations of mixing parameters. In our analysis of rare decays in the SM4, we establish patterns of flavour violation that could in principle be used to disprove this model on the basis of ΔF=1 processes alone. In the LRM, we discuss the importance of the contributions originating from the exchange of heavy, flavour changing, neutral Higgs bosons as well as the inability of the LRM to entirely solve the V ub problem.
Four generations versus left-right symmetry. A comparative numerical analysis
Energy Technology Data Exchange (ETDEWEB)
Heidsieck, Tillmann J.
2012-06-18
In this work, we present a comparative numerical analysis of the Standard Model (SM) with a sequential fourth generation (SM4) and the left-right symmetric Standard model (LRM). We focus on the constraints induced by flavour violating {Delta}F=2 processes in the K and B system while the results of studies of collider bounds and electroweak precision tests are taken into account as external inputs. In contrast to many previous studies of both models considered in this work, we do make not any ad-hoc assumptions on the structure of the relevant mixing matrices. Therefore, we employ powerful Monte Carlo methods in order to approximate the viable parameter space of the models. In preparation of our numerical analysis, we present all relevant formulae and review the different numerical methods used in this work. In order to better understand the patterns of new effects in {Delta}F=2 processes, we perform a fit including all relevant {Delta}F=2 constraints in the context of the Standard Model. The result of this fit is then used in a general discussion on new effects in {Delta}F=2 processes in the context of generic extensions of the Standard Model. Our numerical analysis of the SM4 and the LRM demonstrates that in both models the existing anomalies in {Delta}=2 processes can easily be resolved. We transparently show how the different observables are connected to each other by their dependence on combinations of mixing parameters. In our analysis of rare decays in the SM4, we establish patterns of flavour violation that could in principle be used to disprove this model on the basis of {Delta}F=1 processes alone. In the LRM, we discuss the importance of the contributions originating from the exchange of heavy, flavour changing, neutral Higgs bosons as well as the inability of the LRM to entirely solve the V{sub ub} problem.
Morris, Paul D; Silva Soto, Daniel Alejandro; Feher, Jeroen F A; Rafiroiu, Dan; Lungu, Angela; Varma, Susheel; Lawford, Patricia V; Hose, D Rodney; Gunn, Julian P
2017-08-01
Fractional flow reserve (FFR)-guided percutaneous intervention is superior to standard assessment but remains underused. The authors have developed a novel "pseudotransient" analysis protocol for computing virtual fractional flow reserve (vFFR) based upon angiographic images and steady-state computational fluid dynamics. This protocol generates vFFR results in 189 s (cf >24 h for transient analysis) using a desktop PC, with <1% error relative to that of full-transient computational fluid dynamics analysis. Sensitivity analysis demonstrated that physiological lesion significance was influenced less by coronary or lesion anatomy (33%) and more by microvascular physiology (59%). If coronary microvascular resistance can be estimated, vFFR can be accurately computed in less time than it takes to make invasive measurements.
Directory of Open Access Journals (Sweden)
Ozren Bukovac
2016-01-01
Full Text Available Compared to the other marine engines for ship propulsion, turbocharged two-stroke low speed diesel engines have advantages due to their high efficiency and reliability. Modern low speed ”intelligent” marine diesel engines have a flexibility in its operation due to the variable fuel injection strategy and management of the exhaust valve drive. This paper carried out verified zerodimensional numerical simulations which have been used for MLP (Multilayer Perceptron neural network predictions of marine two-stroke low speed diesel engine steady state performances. The developed MLP neural network was used for marine engine optimized operation control. The paper presents an example of achieving lowest specific fuel consumption and for minimization of the cylinder process highest temperature for reducing NOx emission. Also, the developed neural network was used to achieve optimal exhaust gases heat flow for utilization. The obtained data maps give insight into the optimal working areas of simulated marine diesel engine, depending on the selected start of the fuel injection (SOI and the time of the exhaust valve opening (EVO.
International Nuclear Information System (INIS)
Li, V.C.L.; Harrison, S.; Oosthuizen, P.; Peppley, B.
2004-01-01
'Full text:' A numerical study of the performance of an isooctane catalytic autothermal reformer for a fuel cell automobile has been undertaken. The prototype reformer considered in this study, which is a tubular reformer with three annular sections, was designed and built at the Royal Military College of Canada (RMC). The flow within the reformer was assumed to be steady. The different chemical reactions, along with the reaction rate constants, that take place over the autothermal reforming catalyst (a ceria-based platinum catalyst), were obtained through the analysis and regression of the experimental results from the literature. By neglecting the radial gradients in the concentrations and the velocities of the various species in the flow and in the temperature of the reformer, a one-dimensional numerical model, based on the molar flow rate differential equations and energy equation, was developed to simulate the composition and temperature profiles along the length of the catalyst bed. The results obtained from the numerical model were verified against published results. Numerical results were obtained for a range of total inlet flow rates, different inlet temperatures of the fuel mixture and different oxygen concentrations in feed air at the inlet of the reformer. (author)
Energy Technology Data Exchange (ETDEWEB)
Kim, Sook Kwan; Park, Seong Gyu; Han, Sang Koo [ACT Co., Daejeon (Korea, Republic of)
2016-10-15
As a part of supporting LPSD (Low Power and Shutdown) PSA (Probabilistic Safety Assessment) of Hanul NPP units 1 and 2, numerical analysis for a loss of RHRS (Residual Heat Removal system) during midloop operation was performed using RELAP5/MOD3.3 code. The one of main purpose of thermal hydraulic analysis for PSA work is to estimate times allowable for operation actions in each accident. A loss of RHRS during mid-loop operation may cause more significant results than during RCS full condition due to reduced RCS inventory. In order to perform this kind of analysis, it is particularly important to establish a steady state of mid-loop operational initial condition. Mid-loop operation corresponds to POS(Plant Operational State) 5 and 11 in the category of LPSD PSA at Hanul NPP units 1 and 2. RELAP5/MOD3.3 code was used to predict behaviors of RCS and fuels for the case of loss of RHRS during mid-loop operation at Hanul NPP units 1 and 2. The initial state of mid-loop operational condition was established by proper control of charging and letdown flow. Considering existing similar analysis results for this kind of accident, it can be concluded that RELAP5 code well predicts reasonably the behavior of RCS for loss of RHRS during mid-loop operation in Hanul NPP units 1 and 2. Thus the method developed in the analysis can be applied reasonably to support LPSD PSA.
Energy Technology Data Exchange (ETDEWEB)
Marcum, W.R., E-mail: marcumw@engr.orst.ed [Oregon State University, Department of Nuclear Engineering and Radiation Health Physics, 116 Radiation Center, Corvallis, OR 97330 (United States); Woods, B.G.; Reese, S.R. [Oregon State University, Department of Nuclear Engineering and Radiation Health Physics, 116 Radiation Center, Corvallis, OR 97330 (United States)
2010-01-15
In September of 2008 Oregon State University (OSU) completed its core conversion analysis as part of the Reduced Enrichment for Research and Test Reactors (RERTR) Program. Experimental bulk coolant temperatures were collected in various locations throughout the Oregon State TRIGA Reactor (OSTR) core in order to supplement the validity of the numerical thermal hydraulic results produced in RELAP5-3D Version 2.4.2. Axial bulk coolant temperature distributions were collected by acquiring discrete thermocouple measurements in individual subchannel locations during steady state operation at 1.0 MW{sub th}. The experimental axial temperature distribution collected was compared to one-channel, two-channel, and eight-channel RELAP5-3D models and found to match within 11.94%, 11.69%, and 8.78%, respectively, on average. Comparisons to similar studies were made based on a dimensional analysis of fluid body forces in the discrete core locations, indicating that the chosen approach produces conservative results for use in the OSTR safety analysis.
Interfacing a General Purpose Fluid Network Flow Program with the SINDA/G Thermal Analysis Program
Schallhorn, Paul; Popok, Daniel
1999-01-01
A general purpose, one dimensional fluid flow code is currently being interfaced with the thermal analysis program Systems Improved Numerical Differencing Analyzer/Gaski (SINDA/G). The flow code, Generalized Fluid System Simulation Program (GFSSP), is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development is conducted in multiple phases. This paper describes the first phase of the interface which allows for steady and quasi-steady (unsteady solid, steady fluid) conjugate heat transfer modeling.
Efficient numerical method for district heating system hydraulics
International Nuclear Information System (INIS)
Stevanovic, Vladimir D.; Prica, Sanja; Maslovaric, Blazenka; Zivkovic, Branislav; Nikodijevic, Srdjan
2007-01-01
An efficient method for numerical simulation and analyses of the steady state hydraulics of complex pipeline networks is presented. It is based on the loop model of the network and the method of square roots for solving the system of linear equations. The procedure is presented in the comprehensive mathematical form that could be straightforwardly programmed into a computer code. An application of the method to energy efficiency analyses of a real complex district heating system is demonstrated. The obtained results show a potential for electricity savings in pumps operation. It is shown that the method is considerably more effective than the standard Hardy Cross method still widely used in engineering practice. Because of the ease of implementation and high efficiency, the method presented in this paper is recommended for hydraulic steady state calculations of complex networks
A mathematical and numerical analysis of the Maxwell-Stefan diffusion equations
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...
'Memory' and sustention of microdischarges in a steady-state DBD: volume plasma or surface charge?
International Nuclear Information System (INIS)
Akishev, Yuri; Aponin, Gregory; Balakirev, Anton; Grushin, Mikhail; Karalnik, Vladimir; Petryakov, Alexander; Trushkin, Nikolay
2011-01-01
The results of a numerical study on the spatio-temporal behavior of transient microdischarges (MDs) in a steady-state dielectric barrier discharge (DBD) excited by a sinusoidal voltage are presented. MDs have a spatial 'memory'-every subsequent MD appears at exactly the same location occupied by the MD at the preceding half-period (HP). In the majority of cases each MD appears at its location only once during every HP. For such a case, the memory effect is not attributed to the residual surface charge deposited by the preceding MD but determined by the residual MD plasma column shunting the gap right up to the beginning of the next HP. In contrast to good memory in space, each individual MD has a large scatter with time in its appearance within every HP, i.e. there is no 'memory' concerning the phase of an applied voltage. This MD jittering within the period is attributed to the stochastic nature of partial surface breakdowns around the bases of the MD plasma column. Numerical calculations show that surface breakdown provides an MD current splash at every HP. Hence, in the steady-state DBD, the volume plasma is responsible for the existence of MD spatial 'memory' (i.e. where the MD appears), and the deposited surface charge is responsible for MD jittering in time (i.e. when the MD appears).
BR2 reactor core steady state transient modeling
International Nuclear Information System (INIS)
Makarenko, A.; Petrova, T.
2000-01-01
A coupled neutronics/hydraulics/heat-conduction model of the BR2 reactor core is under development at SCK-CEN. The neutron transport phenomenon has been implemented as steady state and time dependent nodal diffusion. The non-linear heat conduction equation in-side fuel elements is solved with a time dependent finite element method. To allow coupling between functional modules and to simulate subcooled regimes, a simple single-phase hydraulics has been introduced, while the two-phase hydraulics is under development. Multiple tests, general benchmark cases as well as calculation/experiment comparisons demonstrated a good accuracy of both neutronic and thermal hydraulic models, numerical reliability and full code portability. A refinement methodology has been developed and tested for better neutronic representation in hexagonal geometry. Much effort is still needed to complete the development of an extended cross section library with kinetic data and two-phase flow representation. (author)
Steady-State Performance of Kalman Filter for DPLL
Institute of Scientific and Technical Information of China (English)
QIAN Yi; CUI Xiaowei; LU Mingquan; FENG Zhenming
2009-01-01
For certain system models, the structure of the Kalman filter is equivalent to a second-order vari-able gain digital phase-locked loop (DPLL). To apply the knowledge of DPLLs to the design of Kalman filters, this paper studies the steady-state performance of Kalman filters for these system models. The results show that the steady-state Kalman gain has the same form as the DPLL gain. An approximate simple form for the steady-state Kalman gain is used to derive an expression for the equivalent loop bandwidth of the Kalman filter as a function of the process and observation noise variances. These results can be used to analyze the steady-state performance of a Kalman filter with DPLL theory or to design a Kalman filter model with the same steady-state performance as a given DPLL.
A numerical method for a transient two-fluid model
International Nuclear Information System (INIS)
Le Coq, G.; Libmann, M.
1978-01-01
The transient boiling two-phase flow is studied. In nuclear reactors, the driving conditions for the transient boiling are a pump power decay or/and an increase in heating power. The physical model adopted for the two-phase flow is the two fluid model with the assumption that the vapor remains at saturation. The numerical method for solving the thermohydraulics problems is a shooting method, this method is highly implicit. A particular problem exists at the boiling and condensation front. A computer code using this numerical method allow the calculation of a transient boiling initiated by a steady state for a PWR or for a LMFBR
Modeling and numerical simulations of the influenced Sznajd model
Karan, Farshad Salimi Naneh; Srinivasan, Aravinda Ramakrishnan; Chakraborty, Subhadeep
2017-08-01
This paper investigates the effects of independent nonconformists or influencers on the behavioral dynamic of a population of agents interacting with each other based on the Sznajd model. The system is modeled on a complete graph using the master equation. The acquired equation has been numerically solved. Accuracy of the mathematical model and its corresponding assumptions have been validated by numerical simulations. Regions of initial magnetization have been found from where the system converges to one of two unique steady-state PDFs, depending on the distribution of influencers. The scaling property and entropy of the stationary system in presence of varying level of influence have been presented and discussed.
Practical steady-state enzyme kinetics.
Lorsch, Jon R
2014-01-01
Enzymes are key components of most biological processes. Characterization of enzymes is therefore frequently required during the study of biological systems. Steady-state kinetics provides a simple and rapid means of assessing the substrate specificity of an enzyme. When combined with site-directed mutagenesis (see Site-Directed Mutagenesis), it can be used to probe the roles of particular amino acids in the enzyme in substrate recognition and catalysis. Effects of interaction partners and posttranslational modifications can also be assessed using steady-state kinetics. This overview explains the general principles of steady-state enzyme kinetics experiments in a practical, rather than theoretical, way. Any biochemistry textbook will have a section on the theory of Michaelis-Menten kinetics, including derivations of the relevant equations. No specific enzymatic assay is described here, although a method for monitoring product formation or substrate consumption over time (an assay) is required to perform the experiments described. © 2014 Elsevier Inc. All rights reserved.
SALT [System Analysis Language Translater]: A steady state and dynamic systems code
International Nuclear Information System (INIS)
Berry, G.; Geyer, H.
1983-01-01
SALT (System Analysis Language Translater) is a lumped parameter approach to system analysis which is totally modular. The modules are all precompiled and only the main program, which is generated by SALT, needs to be compiled for each unique system configuration. This is a departure from other lumped parameter codes where all models are written by MACROS and then compiled for each unique configuration, usually after all of the models are lumped together and sorted to eliminate undetermined variables. The SALT code contains a robust and sophisticated steady-sate finder (non-linear equation solver), optimization capability and enhanced GEAR integration scheme which makes use of sparsity and algebraic constraints. The SALT systems code has been used for various technologies. The code was originally developed for open-cycle magnetohydrodynamic (MHD) systems. It was easily extended to liquid metal MHD systems by simply adding the appropriate models and property libraries. Similarly, the model and property libraries were expanded to handle fuel cell systems, flue gas desulfurization systems, combined cycle gasification systems, fluidized bed combustion systems, ocean thermal energy conversion systems, geothermal systems, nuclear systems, and conventional coal-fired power plants. Obviously, the SALT systems code is extremely flexible to be able to handle all of these diverse systems. At present, the dynamic option has only been used for LMFBR nuclear power plants and geothermal power plants. However, it can easily be extended to other systems and can be used for analyzing control problems. 12 refs
Measurement of the Operating Parameters and Numerical Analysis of the Mechanical Subsystem
Directory of Open Access Journals (Sweden)
Božek Pavol
2014-08-01
Full Text Available Submission is focused on completing the information system about quality, operation, automatic testing and new evaluating method of vehicle subsystem. Numeric analysis is carried out on the base of automatic collection and systematic recording of commercial car operation. Proposed new information system about operation and trial process allows verification according to the proposed method. Critical components verified in laboratory conditions are detected by numeric analysis of reliability. Quality level increasing not only for final product, but also related automatic test laboratory for cars is the result of respecting these principles.
Measurement of the Operating Parameters and Numerical Analysis of the Mechanical Subsystem
Božek, Pavol; Turygin, Yuri
2014-08-01
Submission is focused on completing the information system about quality, operation, automatic testing and new evaluating method of vehicle subsystem. Numeric analysis is carried out on the base of automatic collection and systematic recording of commercial car operation. Proposed new information system about operation and trial process allows verification according to the proposed method. Critical components verified in laboratory conditions are detected by numeric analysis of reliability. Quality level increasing not only for final product, but also related automatic test laboratory for cars is the result of respecting these principles.
Numerical simulations of the radio-frequency-driven toroidal current in tokamaks
International Nuclear Information System (INIS)
Peysson, Y.; Decker, J.
2014-01-01
Radio-frequency (rf) waves are a powerful tool for improving the performance and stability of tokamak plasmas through heating and current drive mechanisms, allowing current density profile control and steady-state operation. From first principles, and taking advantage from the ordering between the various time and space scales, fast and powerful numerical tools have been developed to calculate the rf-driven current. The current drive problem in tokamaks is first introduced with the purpose of maintaining a steady-state self-organized toroidal magnetohydrodynamic equilibrium, such that a minimal amount of the fusion power has to be recycled to control the plasma current. The strict criterion that characterizes a steady-state discharge is derived from the response of the tokamak, considered as a transformer, and of the plasma, when an external source of current is applied. The calculation of a rf-driven source of current requires solving self-consistently a set of equations describing the dynamics of wave fields and charged particles in an inhomogeneous magnetized plasma. The range of applicability of these equations is discussed, as well as numerical methods developed to solve them, such as the ray-tracing code C3PO and the three-dimensional linearized relativistic bounce-averaged electron Fokker-Planck solver LUKE. Simulations of current drive by lower-hybrid waves are presented to illustrate the applications of our numerical tools. Current drive modeling includes the effect of electron density fluctuations at the plasma edge, and the case of electron cyclotron waves used for stabilization of the 3/2 neoclassical tearing modes in ITER is studied in detail. Finally, ongoing developments, including cross effects between momentum and configuration spaces, aiming at improving current drive calculations are discussed. (authors)
Investigating Convergence Patterns for Numerical Methods Using Data Analysis
Gordon, Sheldon P.
2013-01-01
The article investigates the patterns that arise in the convergence of numerical methods, particularly those in the errors involved in successive iterations, using data analysis and curve fitting methods. In particular, the results obtained are used to convey a deeper level of understanding of the concepts of linear, quadratic, and cubic…
International Nuclear Information System (INIS)
Di Maio, P.A.; Paradiso, D.; Dell’Orco, G.; Pitcher, C.S.; Kalish, M.
2011-01-01
Highlights: ► UPP TS hydraulic behaviour has been investigated under steady state and D and D transient conditions. ► A thermal–hydraulic system code has been adopted and a UPP TS model has been set-up and validated against results of steady state CFD analyses. ► The TS steady state hydraulic characteristic functions have been derived for two coolant flow paths showing that right plate inlet one is the most promising. ► Draining simulations indicate that the 4 MPa injection pressure is high enough to drain almost completely the circuit in a reasonable time (∼6 s). ► Results indicate that right plate inlet flow path allows the TS complete draining, eliminating the need for the drying procedure. - Abstract: The ITER diagnostic Upper Port Plug (UPP) is a water-cooled stainless steel structure aimed to integrate within vacuum vessel the plasma diagnostic systems, shielding them from neutron and photon irradiation. Due to the very intense heat loads expected, a proper cooling circuit has been designed to ensure an adequate UPP cooling with an acceptable thermal rise and an unduly high pumping power and to perform its draining and drying procedure by injection of pressurized nitrogen. A theoretical research activity has been launched at the Department of Nuclear Engineering of the University of Palermo aiming to investigate the hydraulic behaviour of the UPP Trapezoid Section cooling circuit under steady state conditions and during its draining and drying transient procedure. The research activity has been performed following a theoretical–computational approach and adopting the RELAP5 thermal–hydraulic system code. The Trapezoid Section cooling circuit characteristic functions have been derived under steady state conditions at various coolant temperatures for both the coolant flow paths at the present under consideration for this circuit. The distributions of coolant mass flow rates along the channels of the cooling circuit have been calculated too
Understanding void fraction in steady state and dynamic environments
International Nuclear Information System (INIS)
Chexal, B.; Maulbetsch, J.; Harrison, J.; Petersen, C.; Jensen, P.; Horowitz, J.
1997-01-01
Understanding void fraction behavior in steady-state and dynamic environments is important to accurately predict the thermal-hydraulic behavior of two-phase or two-component systems. The Chexal-Lellouche (C-L) void fraction mode described herein covers the full range of pressures, flows, void fractions, and fluid types (steam-water, air-water, and refrigerants). A drift flux model formulation is used which covers the complete range of concurrent and countercurrent flows. The (1996) model revises the earlier C-L void fraction correlation, improves the capability of the model in countercurrent flow based on the incorporation of additional data, and improves the characteristics of the correlation that are important in transient programs. The model has been qualified with data from a number of steady state two-phase and two-component tests, and has been incorporated into the transient analysis code RELAP5 and RETRAN-3D and evaluated with a variety of transient and steady state tests. A 'plug-in' module for the void fraction correlation has been developed and implemented in RELAP5 and RETRAN-3D. The module is available as source code for inclusion into other thermal-hydraulic programs and can be used in any program that utilizes the same interface variables
Numerical bifurcation analysis of conformal formulations of the Einstein constraints
International Nuclear Information System (INIS)
Holst, M.; Kungurtsev, V.
2011-01-01
The Einstein constraint equations have been the subject of study for more than 50 years. The introduction of the conformal method in the 1970s as a parametrization of initial data for the Einstein equations led to increased interest in the development of a complete solution theory for the constraints, with the theory for constant mean curvature (CMC) spatial slices and closed manifolds completely developed by 1995. The first general non-CMC existence result was establish by Holst et al. in 2008, with extensions to rough data by Holst et al. in 2009, and to vacuum spacetimes by Maxwell in 2009. The non-CMC theory remains mostly open; moreover, recent work of Maxwell on specific symmetry models sheds light on fundamental nonuniqueness problems with the conformal method as a parametrization in non-CMC settings. In parallel with these mathematical developments, computational physicists have uncovered surprising behavior in numerical solutions to the extended conformal thin sandwich formulation of the Einstein constraints. In particular, numerical evidence suggests the existence of multiple solutions with a quadratic fold, and a recent analysis of a simplified model supports this conclusion. In this article, we examine this apparent bifurcation phenomena in a methodical way, using modern techniques in bifurcation theory and in numerical homotopy methods. We first review the evidence for the presence of bifurcation in the Hamiltonian constraint in the time-symmetric case. We give a brief introduction to the mathematical framework for analyzing bifurcation phenomena, and then develop the main ideas behind the construction of numerical homotopy, or path-following, methods in the analysis of bifurcation phenomena. We then apply the continuation software package AUTO to this problem, and verify the presence of the fold with homotopy-based numerical methods. We discuss these results and their physical significance, which lead to some interesting remaining questions to
HEATHYD, Steady-State Thermal Hydraulic Analysis of Low-Enriched U Fuel Reactor
International Nuclear Information System (INIS)
NABBI, R.
1989-01-01
1 - Description of program or function: HEATHYD is a code for the steady-state heat transfer calculation of research nuclear reactors with forced convection. It models heat transfer and coolant flow for assemblies of parallel fuel plates of MTR type with any axial power distribution. The thermodynamic model accounts for single phase cooling and sub- cooled boiling condition using the transition criterion of Bergeles-Rosenow. In addition to the calculation of the channel flow velocities and coolant pressure drops, HEATHYD calculates axial distribution of the coolant and clad-surface temperatures. Safety margins to the critical heat flux as a result of burnout condition or flow instability are determined. 2 - Method of solution: Applying the finite difference method, HEATHYD solves the equations of heat conduction and heat transfer to the coolant. For the physical properties of the coolant as a function of the coolant temperature polynomials of degree 6 are used. Depending on the coolant condition, different correlations for the heat transfer coefficient can be applied. The analysis of the critical cooling conditions resulting in burnout or flow instability, is performed according to the correlations developed by Mirshak/ Labuntsov and Forgan/Whittle
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)
Directory of Open Access Journals (Sweden)
Franklin D. Rincón
2015-04-01
Full Text Available This paper introduces a novel steady-state identification (SSI method based on the auto-regressive model with exogenous inputs (ARX. This method allows the SSI with reduced tuning by analyzing the identifiability properties of the system. In particular, the singularity of the model matrices is used as an index for steady-state determination. In this contribution, the novel SSI method is compared to other available techniques, namely the F-like test, wavelet transform and a polynomial-based approach. These methods are implemented for SSI of three different case studies. In the first case, a simulated dataset is used for calibrating the output-based SSI methods. The second case corresponds to a literature nonlinear continuous stirred-tank reactor (CSTR example running at different steady states in which the ARX-based approach is tuned with the available input-output data. Finally, an industrial case with real data of a depropanizer column from PETROBRAS S.A. considering different pieces of equipment is analyzed. The results for a reflux drum case indicate that the wavelet and the F-like test can satisfactorily detect the steady-state periods after careful tuning and when respecting their hypothesis, i.e., smooth data for the wavelet method and the presence of variance in the data for the F-like test. Through a heat exchanger case with different measurement frequencies, we demonstrate the advantages of using the ARX-based method over the other techniques, which include the aspect of online implementation.
DEFF Research Database (Denmark)
Gorji, Mofid; Mirgolbabaei, Hessam; Barari, Amin
2010-01-01
In this paper a two-dimensional numerical simulation of a steady incompressible and turbulent model has been carried out to study the effects of vortex generators in a compact heat exchanger in a curvilinear coordinate system. The mesh which is applied in this study is boundary fitted and has been...
Steady and unsteady calculations on thermal striping phenomena in triple-parallel jet
Energy Technology Data Exchange (ETDEWEB)
Yu, Y.Q., E-mail: yyu@anl.gov [Nuclear Engineering Division, Argonne National Laboratory, Lemont, IL 60439 (United States); Merzari, E.; Thomas, J.W. [Nuclear Engineering Division, Argonne National Laboratory, Lemont, IL 60439 (United States); Obabko, A. [Mathematics and Computer Science Division, Argonne National Laboratory, Lemont, IL 60439 (United States); Aithal, S.M. [Computing, Environment and Life Sciences Directorate, Argonne National Laboratory, Lemont, IL 60439 (United States)
2017-02-15
Highlights: • Both steady (RANS) and unsteady (URANS, LES) methods were applied to study thermal striping. • The unsteady results exhibited reasonably good agreement with experimental results. • The parametric studies on the effects of mesh density and boundary conditions on the accuracy of the overall solutions were also conducted. - Abstract: The phenomenon of thermal striping is encountered in liquid metal cooled fast reactors (LMFR), in which temperature fluctuation due to convective mixing between hot and cold fluids can lead to a possibility of crack initiation and propagation in the structure due to high cycle thermal fatigue. Using sodium experiments of parallel triple jets configuration performed by Japan Atomic Energy Agency (JAEA) as benchmark, numerical simulations were carried out to evaluate the temperature fluctuation characteristics in fluid and the transfer characteristics of temperature fluctuation from fluid to structure, which is important to assess the potential thermal fatigue damage. In this study, both steady (RANS) and unsteady (URANS, LES) methods were applied to predict the temperature fluctuations of thermal striping. The parametric studies on the effects of mesh density and boundary conditions on the accuracy of the overall solutions were also conducted. The velocity, temperature and temperature fluctuation intensity distribution were compared with the experimental data. As expected, steady calculation has limited success in predicting the thermal–hydraulic characteristics of the thermal striping, highlighting the limitations of the RANS approach in unsteady heat transfer simulations. The unsteady results exhibited reasonably good agreement with experimental results for temperature fluctuation intensity, as well as the average temperature and velocity components at the measurement locations.
Steady and unsteady calculations on thermal striping phenomena in triple-parallel jet
International Nuclear Information System (INIS)
Yu, Y.Q.; Merzari, E.; Thomas, J.W.; Obabko, A.; Aithal, S.M.
2017-01-01
Highlights: • Both steady (RANS) and unsteady (URANS, LES) methods were applied to study thermal striping. • The unsteady results exhibited reasonably good agreement with experimental results. • The parametric studies on the effects of mesh density and boundary conditions on the accuracy of the overall solutions were also conducted. - Abstract: The phenomenon of thermal striping is encountered in liquid metal cooled fast reactors (LMFR), in which temperature fluctuation due to convective mixing between hot and cold fluids can lead to a possibility of crack initiation and propagation in the structure due to high cycle thermal fatigue. Using sodium experiments of parallel triple jets configuration performed by Japan Atomic Energy Agency (JAEA) as benchmark, numerical simulations were carried out to evaluate the temperature fluctuation characteristics in fluid and the transfer characteristics of temperature fluctuation from fluid to structure, which is important to assess the potential thermal fatigue damage. In this study, both steady (RANS) and unsteady (URANS, LES) methods were applied to predict the temperature fluctuations of thermal striping. The parametric studies on the effects of mesh density and boundary conditions on the accuracy of the overall solutions were also conducted. The velocity, temperature and temperature fluctuation intensity distribution were compared with the experimental data. As expected, steady calculation has limited success in predicting the thermal–hydraulic characteristics of the thermal striping, highlighting the limitations of the RANS approach in unsteady heat transfer simulations. The unsteady results exhibited reasonably good agreement with experimental results for temperature fluctuation intensity, as well as the average temperature and velocity components at the measurement locations.
International Nuclear Information System (INIS)
Sollogoub, Pierre
2001-01-01
Numerical analyses are needed in different steps of the overall design process. Complex models or non-linear reactor core behaviour are important for qualification and/or comparison of results obtained. Adequate models and test should be defined. Fuel assembly, fuel row, and the complete core should be tested for seismic effects causing LOCA and flow-induced vibrations (FIV)
Effect of steady deflections on the aeroelastic stability of a turbine blade
DEFF Research Database (Denmark)
Kallesøe, Bjarne Skovmose
2011-01-01
This paper deals with effects of geometric non-linearities on the aeroelastic stability of a steady-state defl ected blade. Today, wind turbine blades are long and slender structures that can have a considerable steady-state defl ection which affects the dynamic behaviour of the blade. The fl...... apwise blade defl ection causes the edgewise blade motion to couple to torsional blade motion and thereby to the aerodynamics through the angle of attack. The analysis shows that in the worst case for this particular blade, the edgewise damping can be decreased by half. Copyright © 2010 John Wiley & Sons......, Ltd....
Experimental and numerical investigation of the acoustic response of multi-slit Bunsen burners
Kornilov, V.N.; Rook, R.; Thije Boonkkamp, ten J.H.M.; Goey, de L.P.H.
2009-01-01
Experimental and numerical techniques to characterize the response of premixed methane-air flames to acoustic waves are discussed and applied to a multi-slit Bunsen burner. The steady flame shape, flame front kinematics and flow field of acoustically exited flames, as well as the flame transfer
Efficient multigrid computation of steady hypersonic flows
Koren, B.; Hemker, P.W.; Murthy, T.K.S.
1991-01-01
In steady hypersonic flow computations, Newton iteration as a local relaxation procedure and nonlinear multigrid iteration as an acceleration procedure may both easily fail. In the present chapter, same remedies are presented for overcoming these problems. The equations considered are the steady,
New Tore Supra steady state operating scenario
International Nuclear Information System (INIS)
Martin, G.; Parlange, F.; van Houtte, D.; Wijnands, T.
1995-01-01
This document deals with plasma control in steady state conditions. A new plasma control systems enabling feedback control of global plasma equilibrium parameters has been developed. It also enables to operate plasma discharge in steady state regime. (TEC). 4 refs., 5 figs
Analysis by numerical simulations of non-linear phenomenons in vertical pump rotor dynamic
International Nuclear Information System (INIS)
Bediou, J.; Pasqualini, G.
1992-01-01
Controlling dynamical behavior of main coolant pumps shaftlines is an interesting subject for the user and the constructor. The first is mainly concerned by the interpretation of on field observed behavior, monitoring, reliability and preventive maintenance of his machines. The second must in addition manage with sometimes contradictory requirements related to mechanical design and performances optimization (shaft diameter reduction, clearance,...). The use of numerical modeling is now a classical technique for simple analysis (rough prediction of critical speeds for instance) but is still limited, in particular for vertical shaftline especially when equipped with hydrodynamic bearings, due to the complexity of encountered phenomenons in that type of machine. The vertical position of the shaftline seems to be the origin of non linear dynamical behavior, the analysis of which, as presented in the following discussion, requires specific modelization of fluid film, particularly for hydrodynamic bearings. The low static load generally no longer allows use of stiffness and damping coefficients classically calculated by linearizing fluid film equations near a stable static equilibrium position. For the analysis of such machines, specific numerical models have been developed at Electricite de France in a package for general rotordynamics analysis. Numerical models are briefly described. Then an example is precisely presented and discussed to illustrate some considered phenomenons and their consequences on machine behavior. In this example, the authors interpret the observed behavior by using numerical models, and demonstrate the advantage of such analysis for better understanding of vertical pumps rotordynamic
Compact tokamak reactors part 2 (numerical results)
International Nuclear Information System (INIS)
Wiley, J.C.; Wootton, A.J.; Ross, D.W.
1996-01-01
The authors describe a numerical optimization scheme for fusion reactors. The particular application described is to find the smallest copper coil spherical tokamak, although the numerical scheme is sufficiently general to allow many other problems to be solved. The solution to the steady state energy balance is found by first selecting the fixed variables. The range of all remaining variables is then selected, except for the temperature. Within the specified ranges, the temperature which satisfies the power balance is then found. Tests are applied to determine that remaining constraints are satisfied, and the acceptable results then stored. Results are presented for a range of auxiliary current drive efficiencies and different scaling relationships; for the range of variables chosen the machine encompassing volume increases or remains approximately unchanged as the aspect ratio is reduced
Steady flow instability in an annulus with deflectors at rotational vibration
Energy Technology Data Exchange (ETDEWEB)
Kozlov, Nikolai V [Lab. Vibrational Hydromechanics, Perm State-Humanitarian Pedagogical University 24 Sibirskaya av., 614990 Perm (Russian Federation); Pareau, Dominique; Stambouli, Moncef [Lab. Chemical Engineering, CentraleSupélec-Université Paris Saclay, Grande Voie des Vignes, 92295 Châtenay-Malabry (France); Ivantsov, Andrey, E-mail: kozlov.n@icmm.ru [Lab. Computational Hydrodynamics Institute of Continuous Media Mechanics UB RAS1 Acad. Korolev st., 614013 Perm (Russian Federation)
2016-12-15
Experimental study and direct numerical simulation of the dynamics of an isothermal low-viscosity fluid are done in a coaxial gap of a cylindrical container making rotational vibrations relative to its axis. On the inner surface of the outer wall of the container, semicircular deflectors are regularly situated, playing the role of flow activators. As a result of vibrations, the activators oscillate tangentially. In the simulation, a 2D configuration is considered, excluding the end-wall effects. In the experiment, a container with a large aspect ratio is used. Steady streaming is generated in the viscous boundary layers on the activators. On each of the latter, beyond the viscous domain, a symmetric vortices pair is formed. The steady streaming in the annulus has an azimuthal periodicity. With an increase in the vibration intensity, a competition between the vortices occurs, as a result of which one of the vortices (let us call it even) approaches the activator and the other one (odd) rolls away and couples with the vortices from the neighbouring pairs. Streamlines of the odd vortices close on each other, forming a cog-wheel shaped flow that encircles the inner wall. Comparison of the experiment and the simulation reveals an agreement at moderate vibration intensity. (paper)
On the generation of steady currents in a plasma cylinder using m=0 radio-frequency waves
International Nuclear Information System (INIS)
Hugrass, W.N.
1981-01-01
The generation of a steady current in a resistive plasma cylinder by means of a travelling-wave magnetic field has been studied by using the resistive MHD equations. The non-linear initial-boundary value problem has been solved numerically. Hollow DC current profiles, similar to the experimental data obtained by other workers, have been found. A simple analytical argument, of a more general nature, shows that classical resistive diffusion cannot lead to a more uniform current distribution. (author)
International Nuclear Information System (INIS)
Igna Junior, A.D.
1984-01-01
The relevant parameters of two steady-state models of a plasma column, in fusion regime, were analyzed for an ideal Tokamak. The neo-classical transport theory was considered in the banana regime and in the Pfirsch-Schlueter regime. The first model proposes a correction in the numerical coefficients of the transport equations. In the other one, a poloidal current from Pfirsch-Schlueter classical diffusion is considered aiming to satisfy the pressure balance. (M.C.K.) [pt
DEFF Research Database (Denmark)
Kwok, Kawai; Jørgensen, Peter Stanley; Frandsen, Henrik Lund
2015-01-01
This paper investigates the effective steady-state creep response of porous Ni–YSZ composites used in solid oxide fuel cell applications by numerical homogenization based on three-dimensional microstructural reconstructions and steadystate creep properties of the constituent phases. The Ni phase...... is found to carry insignificant stress in the composite and has a negligible role in the effective creep behavior. Thus, when determining effective creep, porous Ni–YSZ composites can be regarded as porous YSZ in which the Ni phase is counted as additional porosity. The stress exponents of porous YSZ...... are the same as that of dense YSZ, but the effective creep rate increases by a factor of 8–10 due to porosity. The relationship of creep rate and volume fraction of YSZ computed by numerical homogenization is underestimated by most existing analytical models. The Ramakrishnan–Arunchalam creep model provides...
Basin stability measure of different steady states in coupled oscillators
Rakshit, Sarbendu; Bera, Bidesh K.; Majhi, Soumen; Hens, Chittaranjan; Ghosh, Dibakar
2017-04-01
In this report, we investigate the stabilization of saddle fixed points in coupled oscillators where individual oscillators exhibit the saddle fixed points. The coupled oscillators may have two structurally different types of suppressed states, namely amplitude death and oscillation death. The stabilization of saddle equilibrium point refers to the amplitude death state where oscillations are ceased and all the oscillators converge to the single stable steady state via inverse pitchfork bifurcation. Due to multistability features of oscillation death states, linear stability theory fails to analyze the stability of such states analytically, so we quantify all the states by basin stability measurement which is an universal nonlocal nonlinear concept and it interplays with the volume of basins of attractions. We also observe multi-clustered oscillation death states in a random network and measure them using basin stability framework. To explore such phenomena we choose a network of coupled Duffing-Holmes and Lorenz oscillators which are interacting through mean-field coupling. We investigate how basin stability for different steady states depends on mean-field density and coupling strength. We also analytically derive stability conditions for different steady states and confirm by rigorous bifurcation analysis.
Pu recycling in a full Th-MOX PWR core. Part I: Steady state analysis
International Nuclear Information System (INIS)
Fridman, E.; Kliem, S.
2011-01-01
Research highlights: → Detailed 3D 100% Th-MOX PWR core design is developed. → Pu incineration increased by a factor of 2 as compared to a full MOX PWR core. → The core controllability under steady state conditions is demonstrated. - Abstract: Current practice of Pu recycling in existing Light Water Reactors (LWRs) in the form of U-Pu mixed oxide fuel (MOX) is not efficient due to continuous Pu production from U-238. The use of Th-Pu mixed oxide (TOX) fuel will considerably improve Pu consumption rates because virtually no new Pu is generated from thorium. In this study, the feasibility of Pu recycling in a typical pressurized water reactor (PWR) fully loaded with TOX fuel is investigated. Detailed 3-dimensional 100% TOX and 100% MOX PWR core designs are developed. The full MOX core is considered for comparison purposes. The design stages included determination of Pu loading required to achieve 18-month fuel cycle assuming three-batch fuel management scheme, selection of poison materials, development of the core loading pattern, optimization of burnable poison loadings, evaluation of critical boron concentration requirements, estimation of reactivity coefficients, core kinetic parameters, and shutdown margin. The performance of the MOX and TOX cores under steady-state condition and during selected reactivity initiated accidents (RIAs) is compared with that of the actual uranium oxide (UOX) PWR core. Part I of this paper describes the full TOX and MOX PWR core designs and reports the results of steady state analysis. The TOX core requires a slightly higher initial Pu loading than the MOX core to achieve the target fuel cycle length. However, the TOX core exhibits superior Pu incineration capabilities. The significantly degraded worth of control materials in Pu cores is partially addressed by the use of enriched soluble boron and B 4 C as a control rod absorbing material. Wet annular burnable absorber (WABA) rods are used to flatten radial power distribution
CFD analysis of bubble microlayer and growth in subcooled flow boiling
Energy Technology Data Exchange (ETDEWEB)
Owoeye, Eyitayo James, E-mail: msgenius10@ufl.edu; Schubring, DuWanye, E-mail: dlschubring@ufl.edu
2016-08-01
Highlights: • A new LES-microlayer model is introduced. • Analogous to the unresolved SGS in LES, analysis of bubble microlayer was performed. • The thickness of bubble microlayer was computed at both steady and transient states. • The macroscale two-phase behavior was captured with VOF coupled with AMR. • Numerical validations were performed for both the micro- and macro-region analyses. - Abstract: A numerical study of single bubble growth in turbulent subcooled flow boiling was carried out. The macro- and micro-regions of the bubble were analyzed by introducing a LES-microlayer model. Analogous to the unresolved sub-grid scale (SGS) in LES, a microlayer analysis was performed to capture the unresolved thermal scales for the micro-region heat transfer by deriving equations for the microlayer thickness at steady and transient states. The phase change at the macro-region was based on Volume-of-Fluid (VOF) interface tracking method coupled with adaptive mesh refinement (AMR). Large Eddy Simulation (LES) was used to model the turbulence characteristics. The numerical model was validated with multiple experimental data from the open literature. This study includes parametric variations that cover the operating conditions of boiling water reactor (BWR) and pressurized water reactor (PWR). The numerical model was used to study the microlayer thickness, growth rate, dynamics, and distortion of the bubble.
A mathematical model and numerical solution of interface problems for steady state heat conduction
Directory of Open Access Journals (Sweden)
Z. Muradoglu Seyidmamedov
2006-01-01
(isolation Ωδ tends to zero. For each case, the local truncation errors of the used conservative finite difference scheme are estimated on the nonuniform grid. A fast direct solver has been applied for the interface problems with piecewise constant but discontinuous coefficient k=k(x. The presented numerical results illustrate high accuracy and show applicability of the given approach.
Measurement of non-steady-state free fatty acid turnover
International Nuclear Information System (INIS)
Jensen, M.D.; Heiling, V.; Miles, J.M.
1990-01-01
The accuracy of non-steady-state equations for measuring changes in free fatty acid rate of appearance (Ra) is unknown. In the present study, endogenous lipolysis (traced with [ 14 C]-linoleate) was pharmacologically suppressed in six conscious mongrel dogs. A computer-responsive infusion pump was then used to deliver an intravenous oleic acid emulsion in both constant and linear gradient infusion modes. Both non-steady-state equations with various effective volumes of distribution (V) and steady-state equations were used to measure oleate Ra [( 14 C]oleate). Endogenous lipolysis did not change during the experiment. When oleate Ra increased in a linear gradient fashion, only non-steady-state equations with a large (150 ml/kg) V resulted in erroneous values (9% overestimate, P less than 0.05). In contrast, when oleate Ra decreased in a similar fashion, steady-state and standard non-steady-state equations (V = plasma volume = 50 ml/kg) overestimated total oleate Ra (18 and 7%, P less than 0.001 and P less than 0.05, respectively). Overall, non-steady-state equations with an effective V of 90 ml/kg (1.8 x plasma volume) allowed the most accurate estimates of oleate Ra
Radhakrishnan, Krishnan
1994-01-01
LSENS, the Lewis General Chemical Kinetics and Sensitivity Analysis Code, has been developed for solving complex, homogeneous, gas-phase chemical kinetics problems and contains sensitivity analysis for a variety of problems, including nonisothermal situations. This report is part 1 of a series of three reference publications that describe LENS, provide a detailed guide to its usage, and present many example problems. Part 1 derives the governing equations and describes the numerical solution procedures for the types of problems that can be solved. The accuracy and efficiency of LSENS are examined by means of various test problems, and comparisons with other methods and codes are presented. LSENS is a flexible, convenient, accurate, and efficient solver for chemical reaction problems such as static system; steady, one-dimensional, inviscid flow; reaction behind incident shock wave, including boundary layer correction; and perfectly stirred (highly backmixed) reactor. In addition, the chemical equilibrium state can be computed for the following assigned states: temperature and pressure, enthalpy and pressure, temperature and volume, and internal energy and volume. For static problems the code computes the sensitivity coefficients of the dependent variables and their temporal derivatives with respect to the initial values of the dependent variables and/or the three rate coefficient parameters of the chemical reactions.
Asymptotic analysis of the structure of a steady planar detonation: Review and extension
Directory of Open Access Journals (Sweden)
Bush W. B.
1999-01-01
Full Text Available The structure of a steady planar Chapman–Jouguet detonation, which is supported by a direct first-order one-step irreversible exothermic unimolecular reaction, subject to Arrhenius kinetics, is examined. Solutions are studied, by means of a limit-process-expansion analysis, valid for Λ , proportional to the ratio of the reaction rate to the flow rate, going to zero, and for β , proportional to the ratio of the activation temperature to the maximum flow temperature, going to infinity, with the product Λ β 1 / 2 going to zero. The results, essentially in agreement with the Zeldovich–von Neumann–Doring model, show that the detonation consists of (1 a three-region upstream shock-like zone, wherein convection and diffusion dominate; (2 an exponentially thicker five-region downstream deflagration-like zone, wherein convection and reaction dominate; and (3 a transition zone, intermediate to the upstream and downstream zones, wherein convection, diffusion, and reaction are of the same order of magnitude. It is in this transition zone that the ideal Neumann state is most closely approached.
Development of a numerical model for vehicle-bridge interaction analysis of railway bridges
Kim, Hee Ju; Cho, Eun Sang; Ham, Jun Su; Park, Ki Tae; Kim, Tae Heon
2016-04-01
In the field of civil engineering, analyzing dynamic response was main concern for a long time. These analysis methods can be divided into moving load analysis method and moving mass analysis method, and formulating each an equation of motion has recently been studied after dividing vehicles and bridges. In this study, the numerical method is presented, which can consider the various train types and can solve the equations of motion for a vehicle-bridge interaction analysis by non-iteration procedure through formulating the coupled equations for motion. Also, 3 dimensional accurate numerical models was developed by KTX-vehicle in order to analyze dynamic response characteristics. The equations of motion for the conventional trains are derived, and the numerical models of the conventional trains are idealized by a set of linear springs and dashpots with 18 degrees of freedom. The bridge models are simplified by the 3 dimensional space frame element which is based on the Euler-Bernoulli theory. The rail irregularities of vertical and lateral directions are generated by PSD functions of the Federal Railroad Administration (FRA).
International Nuclear Information System (INIS)
Thingna, Juzar; Zhou, Hangbo; Wang, Jian-Sheng
2014-01-01
We present a general theory to calculate the steady-state heat and electronic currents for nonlinear systems using a perturbative expansion in the system-bath coupling. We explicitly demonstrate that using the truncated Dyson-series leads to divergences in the steady-state limit, thus making it impossible to be used for actual applications. In order to resolve the divergences, we propose a unique choice of initial condition for the reduced density matrix, which removes the divergences at each order. Our approach not only allows us to use the truncated Dyson-series, with a reasonable choice of initial condition, but also gives the expected result that the steady-state solutions should be independent of initial preparations. Using our improved Dyson series we evaluate the heat and electronic currents up to fourth-order in system-bath coupling, a considerable improvement over the standard quantum master equation techniques. We then numerically corroborate our theory for archetypal settings of linear systems using the exact nonequilibrium Green's function approach. Finally, to demonstrate the advantage of our approach, we deal with the nonlinear spin-boson model to evaluate heat current up to fourth-order and find signatures of cotunnelling process
LikelihoodLib - Fitting, Function Maximization, and Numerical Analysis
Smirnov, I B
2001-01-01
A new class library is designed for function maximization, minimization, solution of equations and for other problems related to mathematical analysis of multi-parameter functions by numerical iterative methods. When we search the maximum or another special point of a function, we may change and fit all parameters simultaneously, sequentially, recursively, or by any combination of these methods. The discussion is focused on the first the most complicated method, although the others are also supported by the library. For this method we apply: control of precision by interval computations; the calculation of derivatives either by differential arithmetic, or by the method of finite differences with the step lengths which provide suppression of the influence of numerical noise; possible synchronization of the subjective function calls with minimization of the number of iterations; competitive application of various methods for step calculation, and converging to the solution by many trajectories.
Steady state neutral beam injector
International Nuclear Information System (INIS)
Mattoo, S.K.; Bandyopadhyay, M.; Baruah, U.K.; Bisai, N.; Chakbraborty, A.K.; Chakrapani, Ch.; Jana, M.R.; Bajpai, M.; Jaykumar, P.K.; Patel, D.; Patel, G.; Patel, P.J.; Prahlad, V.; Rao, N.V.M.; Rotti, C.; Singh, N.P.; Sridhar, B.
2000-01-01
Learning from operational reliability of neutral beam injectors in particular and various heating schemes including RF in general on TFTR, JET, JT-60, it has become clear that neutral beam injectors may find a greater role assigned to them for maintaining the plasma in steady state devices under construction. Many technological solutions, integrated in the present day generation of injectors have given rise to capability of producing multimegawatt power at many tens of kV. They have already operated for integrated time >10 5 S without deterioration in the performance. However, a new generation of injectors for steady state devices have to address to some basic issues. They stem from material erosion under particle bombardment, heat transfer > 10 MW/m 2 , frequent regeneration of cryopanels, inertial power supplies, data acquisition and control of large volume of data. Some of these engineering issues have been addressed to in the proposed neutral beam injector for SST-1 at our institute; the remaining shall have to wait for the inputs of the database generated from the actual experience with steady state injectors. (author)
Numerical Analysis of Multiscale Computations
Engquist, Björn; Tsai, Yen-Hsi R
2012-01-01
This book is a snapshot of current research in multiscale modeling, computations and applications. It covers fundamental mathematical theory, numerical algorithms as well as practical computational advice for analysing single and multiphysics models containing a variety of scales in time and space. Complex fluids, porous media flow and oscillatory dynamical systems are treated in some extra depth, as well as tools like analytical and numerical homogenization, and fast multipole method.
Minimal gain marching schemes: searching for unstable steady-states with unsteady solvers
de S. Teixeira, Renan; S. de B. Alves, Leonardo
2017-12-01
Reference solutions are important in several applications. They are used as base states in linear stability analyses as well as initial conditions and reference states for sponge zones in numerical simulations, just to name a few examples. Their accuracy is also paramount in both fields, leading to more reliable analyses and efficient simulations, respectively. Hence, steady-states usually make the best reference solutions. Unfortunately, standard marching schemes utilized for accurate unsteady simulations almost never reach steady-states of unstable flows. Steady governing equations could be solved instead, by employing Newton-type methods often coupled with continuation techniques. However, such iterative approaches do require large computational resources and very good initial guesses to converge. These difficulties motivated the development of a technique known as selective frequency damping (SFD) (Åkervik et al. in Phys Fluids 18(6):068102, 2006). It adds a source term to the unsteady governing equations that filters out the unstable frequencies, allowing a steady-state to be reached. This approach does not require a good initial condition and works well for self-excited flows, where a single nonzero excitation frequency is selected by either absolute or global instability mechanisms. On the other hand, it seems unable to damp stationary disturbances. Furthermore, flows with a broad unstable frequency spectrum might require the use of multiple filters, which delays convergence significantly. Both scenarios appear in convectively, absolutely or globally unstable flows. An alternative approach is proposed in the present paper. It modifies the coefficients of a marching scheme in such a way that makes the absolute value of its linear gain smaller than one within the required unstable frequency spectra, allowing the respective disturbance amplitudes to decay given enough time. These ideas are applied here to implicit multi-step schemes. A few chosen test cases
Finite element analysis of nonlinear creeping flows
International Nuclear Information System (INIS)
Loula, A.F.D.; Guerreiro, J.N.C.
1988-12-01
Steady-state creep problems with monotone constitutive laws are studied. Finite element approximations are constructed based on mixed Petrov-Galerkin formulations for constrained problems. Stability, convergence and a priori error estimates are proved for equal-order discontinuous stress and continuous velocity interpolations. Numerical results are presented confirming the rates of convergence predicted in the analysis and the good performance of this formulation. (author) [pt
Tester Detects Steady-Short Or Intermittent-Open Circuits
Anderson, Bobby L.
1990-01-01
Momentary open circuits or steady short circuits trigger buzzer. Simple, portable, lightweight testing circuit sounds long-duration alarm when it detects steady short circuit or momentary open circuit in coaxial cable or other two-conductor transmission line. Tester sensitive to discontinuities lasting 10 microseconds or longer. Used extensively for detecting intermittent open shorts in accelerometer and extensometer cables. Also used as ordinary buzzer-type continuity checker to detect steady short or open circuits.
Hydrodynamics of stratified epithelium: Steady state and linearized dynamics
Yeh, Wei-Ting; Chen, Hsuan-Yi
2016-05-01
A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.
On the One-Dimensional Steady and Unsteady Porous Flow Equation
DEFF Research Database (Denmark)
Andersen, O. H.; Burcharth, H. F.
1995-01-01
Porous flow in coarse granular media is discussed theoretically with special concern given to the variation of the flow resistance with the porosity. For steady state flow, the Navier-Stokes equation is applied as a basis for the derivations. A turbulent flow equation is suggested. Alternative...... derivations based on dimensional analysis and a pipe analogy, respectively, are discussed. For non-steady state flow, the derivations are based on a cylinder/sphere analogy leading to a virtual mass coefficient. For the fully turbulent flow regime, existing experimental data values of the quadratic flow...... resistance coefficients are presented. Moreover, a simple formula for estimation of the turbulent flow coefficient is given. Virtual mass coefficients based on existing data are presented, however, no definite conclusions can be given due to the scarce data available....
3-D steady analysis of flow in CRDM sewerage system
International Nuclear Information System (INIS)
Sun Yan; Liang Tiebo; Chen Zhihui; Zhao Jing; Zhang Yulong
2014-01-01
In order to obtain the flow state during sewer condition in Reactor and CRDM Sewerage system (RSE), this paper analyzes the 3-D steady flow in RSE by using Computational Fluid Dynamics (CFD) method. In the premise that the pressure drop of the RSE is known, the mass flow rate, the velocity and the type of flow in the system is obtained with the inverse method, which is proposed and validated to be applicable in the paper. The result shows that in the sewerage conditions, the type of flow in the RSE is turbulence flow, which is helpful to sewer drain. The study results give an reference for the design of RSE. (authors)
Steady turbulent flow in curved rectangular channels
De Vriend, H.J.
1979-01-01
After the study of fully developed and developing steady laminar flow in curved channels of shallow rectangular wet cross-section (see earlier reports in this series), steady turbulent flow in such channels is investigated as a next step towards a mathematical model of the flow in shallow river
Numerical Modeling and Analysis of Transient Electromagnetic Wave Propagation and Scattering
National Research Council Canada - National Science Library
Petropoulos, Peter
2000-01-01
.... We are continuing with analysis and numerical comparisons with exact ABC's in ABC's instead of the simpler Dirichlet boundary condition to terminate the sponge layers in the time-domain is desirable...
Numerical Diffusion Effect in Dynamic Simulation of Thermohydraulic Systems
International Nuclear Information System (INIS)
Zanocco, Pablo; Gimenez, Marcelo; Delmastro, Dario
2003-01-01
In this work, the behavior of the explicit - up-wind method is studied in two phase natural convection circuit, near the instabilities boundaries.The effect of the numerical diffusion of the scheme upon the system stability is evaluated by means of linearization by small perturbations.The results are compared with a non-diffusive method, in the frequency domain, that solves analytically the linearized equations around a steady state condition.Moreover, a conservation equation transport model using the method of characteristics is implemented and studied.This method is compared with the explicit - up-wind scheme and it is found that it significantly reduces numerical diffusion in the equations solution. Several advantages are visualized for particular cases
Light diffusion in N-layered turbid media: steady-state domain.
Liemert, André; Kienle, Alwin
2010-01-01
We deal with light diffusion in N-layered turbid media. The steady-state diffusion equation is solved for N-layered turbid media having a finite or an infinitely thick N'th layer. Different refractive indices are considered in the layers. The Fourier transform formalism is applied to derive analytical solutions of the fluence rate in Fourier space. The inverse Fourier transform is calculated using four different methods to test their performance and accuracy. Further, to avoid numerical errors, approximate formulas in Fourier space are derived. Fast solutions for calculation of the spatially resolved reflectance and transmittance from the N-layered turbid media ( approximately 10 ms) with small relative differences (<10(-7)) are found. Additionally, the solutions of the diffusion equation are compared to Monte Carlo simulations for turbid media having up to 20 layers.
The stably stratified internal boundary layer for steady and diurnally varying offshore flow
Garratt, J. R.
1987-03-01
A two-dimensional numerical mesoscale model is used to investigate the internal structure and growth of the stably stratified internal boundary layer (IBL) beneath warm, continental air flowing over a cooler sea. Two situations are studied — steady-state and diurnally varying offshore flow. In the steady-state case, vertical profiles of mean quantities and eddy diffusion coefficients ( K) within the IBL show small, but significant, changes with increasing distance from the coast. The top of the IBL is well defined, with large vertical gradients within the layer and a maximum in the coast-normal wind component near the top. Well away from the coast, turbulence, identified by non-zero K, decreases to insignificant levels near the top of the IBL; the IBL itself is characterised by a critical value of the layer-flux Richardson number equal to 0.18. The overall behaviour of the mean profiles is similar to that found in the horizontally homogeneous stable boundary layer over land. A simple physical model is used to relate the depth of the layer h to several relevant physical parameters viz., x, the distance from the coast and U, the large-scale wind (both normal to the coastline) and gδθ/θ, Δθ being the temperature difference between continental mixed-layer air and sea surface, θ is the mean potential temperature and g is the acceleration due to gravity. Excellent agreement with the numerical results is found, with h = 0.014 x 1/2 U ( gδθ/θ)-1/2. In the diurnally varying case, the mean profiles within the IBL show only small differences from the steady-state case, although diurnal variations, particularly in the wind maximum, are evident within a few hundred kilometres of the coast. A mesoscale circulation normal to the coast, and superimposed upon the mean offshore flow, develops seawards of the coastline with maximum vertical velocities about sunset, of depth about 2 km and horizontal scale ≈ 500 km. The circulation is related to the advection, and
International Nuclear Information System (INIS)
Williamson, R.L.
2011-01-01
Highlights: → The ABAQUS thermomechanics code is enhanced to enable simulation of nuclear fuel behavior. → Comparisons are made between discrete and smeared fuel pellet analysis. → Multidimensional and multipellet analysis is important for accurate prediction of PCMI. → Fully coupled thermomechanics results in very smooth prediction of fuel-clad gap closure. → A smeared-pellet approximation results in significant underprediction of clad radial displacements and plastic strain. - Abstract: A powerful multidimensional fuels performance analysis capability, applicable to both steady and transient fuel behavior, is developed based on enhancements to the commercially available ABAQUS general-purpose thermomechanics code. Enhanced capabilities are described, including: UO 2 temperature and burnup dependent thermal properties, solid and gaseous fission product swelling, fuel densification, fission gas release, cladding thermal and irradiation creep, cladding irradiation growth, gap heat transfer, and gap/plenum gas behavior during irradiation. This new capability is demonstrated using a 2D axisymmetric analysis of the upper section of a simplified multipellet fuel rod, during both steady and transient operation. Comparisons are made between discrete and smeared-pellet simulations. Computational results demonstrate the importance of a multidimensional, multipellet, fully-coupled thermomechanical approach. Interestingly, many of the inherent deficiencies in existing fuel performance codes (e.g., 1D thermomechanics, loose thermomechanical coupling, separate steady and transient analysis, cumbersome pre- and post-processing) are, in fact, ABAQUS strengths.
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
The non-steady state oceanic CO2 signal: its importance, magnitude and a novel way to detect it
Directory of Open Access Journals (Sweden)
B. I. McNeil
2013-04-01
Full Text Available The role of the ocean has been pivotal in modulating rising atmospheric CO2 levels since the industrial revolution, sequestering nearly half of all fossil-fuel derived CO2 emissions. Net oceanic uptake of CO2 has roughly doubled between the 1960s (~1 Pg C yr−1 and 2000s (~2 Pg C yr−1, with expectations that it will continue to absorb even more CO2 with rising future atmospheric CO2 levels. However, recent CO2 observational analyses along with numerous model predictions suggest the rate of oceanic CO2 uptake is already slowing, largely as a result of a natural decadal-scale outgassing signal. This recent CO2 outgassing signal represents a significant shift in our understanding of the oceans role in modulating atmospheric CO2. Current tracer-based estimates for the ocean storage of anthropogenic CO2 assume the ocean circulation and biology is in steady state, thereby missing the new and potentially important "non-steady state" CO2 outgassing signal. By combining data-based techniques that assume the ocean is in a steady state, with techniques that constrain the net oceanic CO2 uptake signal, we show how to extract the non-steady state CO2 signal from observations. Over the entire industrial era, the non-steady state CO2 outgassing signal (~13 ± 10 Pg C is estimated to represent about 9% of the total net CO2 inventory change (~142 Pg C. However, between 1989 and 2007, the non-steady state CO2 outgassing signal (~6.3 Pg C has likely increased to be ~18% of net oceanic CO2 storage over that period (~36 Pg C. The present uncertainty of our data-based techniques for oceanic CO2 uptake limit our capacity to quantify the non-steady state CO2 signal, however with more data and better certainty estimates across a range of diverse methods, this important and growing CO2 signal could be better constrained in the future.
Numerically and experimentally analysis of creep
International Nuclear Information System (INIS)
Fontanive, J.A.
1982-11-01
The problems of creep in concrete are analyzed experimentally and numerically, comparing with classical methods and suggesting a numerical procedure for the solution of these problems. Firstly, fundamentals of viscoelasticity and its application to concrete behaviour representation are presented. Then the theories of Dischinger and Arutyunyan are studied, and a computing numerical solutions are compared in several examples. Finally, experiences on creep and relaxation are described, and its result are analyzed. Some coments on possible future developments are included. (Author) [pt
An implicit steady-state initialization package for the RELAP5 computer code
International Nuclear Information System (INIS)
Paulsen, M.P.; Peterson, C.E.; Odar, F.
1995-08-01
A direct steady-state initialization (DSSI) method has been developed and implemented in the RELAP5 hydrodynamic analysis program. It provides a means for users to specify a small set of initial conditions which are then propagated through the remainder of the system. The DSSI scheme utilizes the steady-state form of the RELAP5 balance equations for nonequilibrium two-phase flow. It also employs the RELAP5 component models and constitutive model packages for wall-to-phase and interphase momentum and heat exchange. A fully implicit solution of the linearized hydrodynamic equations is implemented. An implicit coupling scheme is used to augment the standard steady-state heat conduction solution for steam generator use. It solves the primary-side tube region energy equations, heat conduction equations, wall heat flux boundary conditions, and overall energy balance equation as a coupled system of equations and improves convergence. The DSSI method for initializing RELAP5 problems to steady-state conditions has been compared with the transient solution scheme using a suite of test problems including; adiabatic single-phase liquid and vapor flow through channels with and without healing and area changes; a heated two-phase test bundle representative of BWR core conditions; and a single-loop PWR model
Numerical analysis of the big bounce in loop quantum cosmology
International Nuclear Information System (INIS)
Laguna, Pablo
2007-01-01
Loop quantum cosmology (LQC) homogeneous models with a massless scalar field show that the big-bang singularity can be replaced by a big quantum bounce. To gain further insight on the nature of this bounce, we study the semidiscrete loop quantum gravity Hamiltonian constraint equation from the point of view of numerical analysis. For illustration purposes, we establish a numerical analogy between the quantum bounces and reflections in finite difference discretizations of wave equations triggered by the use of nonuniform grids or, equivalently, reflections found when solving numerically wave equations with varying coefficients. We show that the bounce is closely related to the method for the temporal update of the system and demonstrate that explicit time-updates in general yield bounces. Finally, we present an example of an implicit time-update devoid of bounces and show back-in-time, deterministic evolutions that reach and partially jump over the big-bang singularity
A numerical technique for reactor subchannel analysis
International Nuclear Information System (INIS)
Fath, Hassan E.S.
1983-01-01
A numerical technique is developed for the solution of the transient boundary layer equations with a moving liquid-vapour interface boundary. The technique uses the finite difference method with the velocity components defined over an Eulerian mesh. A system of interface massless markers is defined where the markers move with the flow field according to a simple kinematic relation between the interface geometry and the fluid velocity. Different applications of nuclear engineering interest are reported with some available results. The present technique is capable of predicting the interface profile near the wall which is important in the reactor subchannel analysis
Wind turbine blades: A study of prototypes in a steady regime - Unsteady considerations
Leblanc, R.; Goethals, R.; de Saint Louvent, B.
1981-11-01
The results of comparisons of numerical models with experimental results for the performance of prototype wind turbines in steady flows are presented, along with preliminary results on behavior in unsteady flows. The numerical models are based on previous schemes devised for propellers, with modifications for small perturbations, significant radial velocity effects from the wake, and the fact that the speed is induced. Two computational methods are currently used, one a method of short blades, the other the Prandtl lifting line theory. Trials have been run in the T4 wind tunnel using a 3 m horizontal axis machine and a 2.5 m Darrieus. Attention is given to modeling the structural dynamics and turbulent flow structures encountered by wind turbines. Experimental results relating windspeed, angle of attack, and output are presented. Optimization studies have indicated that wind farms will require a 6-7 blade diameter unit spacing to maintain satisfactory group output efficiencies.
Numerical Analysis of Flood modeling of upper Citarum River under Extreme Flood Condition
Siregar, R. I.
2018-02-01
This paper focuses on how to approach the numerical method and computation to analyse flood parameters. Water level and flood discharge are the flood parameters solved by numerical methods approach. Numerical method performed on this paper for unsteady flow conditions have strengths and weaknesses, among others easily applied to the following cases in which the boundary irregular flow. The study area is in upper Citarum Watershed, Bandung, West Java. This paper uses computation approach with Force2 programming and HEC-RAS to solve the flow problem in upper Citarum River, to investigate and forecast extreme flood condition. Numerical analysis based on extreme flood events that have occurred in the upper Citarum watershed. The result of water level parameter modeling and extreme flood discharge compared with measurement data to analyse validation. The inundation area about flood that happened in 2010 is about 75.26 square kilometres. Comparing two-method show that the FEM analysis with Force2 programs has the best approach to validation data with Nash Index is 0.84 and HEC-RAS that is 0.76 for water level. For discharge data Nash Index obtained the result analysis use Force2 is 0.80 and with use HEC-RAS is 0.79.
Numerical Analysis Of The Resistance To Pullout Test Of Clinched Assemblies Of Thin Metal Sheets
International Nuclear Information System (INIS)
Jomaa, Moez; Billardon, Rene
2007-01-01
This paper presents the finite element analysis of the resistance of a clinch point to pullout test -that follows the numerical analysis of the forming process of the point-. The simulations have been validated by comparison with experimental evidences. The influence on the numerical predictions of various computation and process parameters have been evaluated
International Nuclear Information System (INIS)
Minato, Akihiko; Nagoyoshi, Takuji; Nakamura, Akira; Fujii, Yuzo; Aya, Izuo; Yamane, Kenji
2004-01-01
Subcooled water injection into steam flow in piping systems may generate a water column containing a large steam slug. The steam slug collapses due to rapid condensation and interfaces on both sides collides with each other. Water hammer takes place and sharp pressure pulse propagates through the pipe. The purpose of this study is to show capability of the present numerical simulation method for predictions of pressure transient and loads on a piping system following steam slug collapse. A three-dimensional computer code for transient gas-liquid two-phase flow was applied to simulate an experiment of steam-condensation-induced water hammer with a horizontal polycarbonate pipe. The code was based on the extended two-fluid model, which treated interface motion using the VOF (Volume of Fluid) technique. The Godunov scheme of highly compressible single-phase flow was modified for application to the Riemann problem solution of gas-liquid mixture. Analysis of local steam slug collapse resulted in comparable peak pressure and pulse width of pressure transients with the observation. The calculation of pressure pulse propagation and impact load on piping system showed the quasi-steady pressure load was imposed especially on elbow at 1/10 of water hammer peak pressure. (author)
Directory of Open Access Journals (Sweden)
Hee-Jeong Kwak
2015-01-01
Full Text Available Many studies have investigated the accuracy of the numerical parameters in the application of the quasi steady-state calculation method. The aim of this study is to derive the reference numerical parameters of the ISO 13790 monthly method by reflecting the surface-to-volume (S/V ratio and the characteristics of the structures. The calculation process was established, and the parameters necessary to derive the reference numerical parameters were calculated based on the input data prepared for the established calculation processes. The reference numerical parameters were then derived through regression analyses of the calculated parameters and the time constant. The parameters obtained from an apartment building and the parameters of the international standard were both applied to the Passive House Planning Package (PHPP and EnergyPlus programs, and the results were analyzed in order to evaluate the validity of the results. The analysis revealed that the calculation results based on the parameters derived from this study yielded lower error rates than those based on the default parameters in ISO 13790. However, the differences were shown to be negligible in the case of high heat capacity.
Steady electric fields and currents elementary electromagnetic theory
Chirgwin, B H; Kilmister, C W
2013-01-01
Steady Electric Fields and Currents, Volume 1 is an introductory text to electromagnetism and potential theory. This book starts with the fields associated with stationary charges and unravels the stationary condition to allow consideration of the flow of steady currents in closed circuits. The opening chapter discusses the experimental results that require mathematical explanation and discussion, particularly those referring to phenomena that question the validity of the simple Newtonian concepts of space and time. The subsequent chapters consider steady-state fields, electrostatics, dielectr
Dynamics and Control of Underwater Gliders I: Steady Motions
Mahmoudian, N.; Geisbert, J.; Woolsey, C.
2007-01-01
This paper describes analysis of steady motions for underwater gliders, a type of highly efficient underwater vehicle which uses gravity for propulsion. Underwater gliders are winged underwater vehicles which locomote by modulating their buoyancy and their attitude. Several such vehicles have been developed and have proven their worth as efficient long-distance, long-duration ocean sampling platforms. To date, the primary emphasis in underwater glider development has been on locomotive effici...
Diagnosis methods based on noise analysis at Cernavoda NPP, Romania
International Nuclear Information System (INIS)
Banica, Constantin; Dobrea, Dumitru
1999-01-01
This paper describes a recent noise analysis of the neutronic signals provided by in-core flux detectors (ICFD) and ion chambers (IC). This analysis is part of on-going program developed for Unit 1 of the Cernavoda NPP, Romania, with the following main objectives: - prediction of detector failures based on pattern recognition; - determination of fast excursions from steady states; - detection of abnormal mechanical vibrations in the reactor core. The introduction presents briefly the reactor, the location of ICFD's and IC's. The second section presents the data acquisition systems and their capabilities. The paper continues with a brief presentation of the numerical methods used for analysis (section 3). The most significant results can be found in section 4, while section 5 concludes about useful information that can be obtained from the neutronic signals at high power steady-state operation. (authors)
International Nuclear Information System (INIS)
Wu, T.; Cowan, C.L.; Lauer, A.; Schwiegk, H.J.
1982-03-01
The ASTERIX modular code package was developed at KFA Laboratory-Juelich for the steady state and xenon transient analysis of a pebble bed high temperature reactor. The code package was implemented on the Stanford Linear Accelerator Center Computer in August, 1980, and a user's manual for the current version of the code, identified as ASTERIX-2, was prepared as a cooperative effort by KFA Laboratory and GE-ARSD. The material in the manual includes the requirements for accessing the program, a description of the major subroutines, a listing of the input options, and a listing of the input data for a sample problem. The material is provided in sufficient detail for the user to carry out a wide range of analysis from steady state operations to the xenon induced power transients in which the local xenon, temperature, buckling and control feedback effects have been incorporated in the problem solution. (orig.)
Introduction to numerical analysis
Hildebrand, F B
1987-01-01
Well-known, respected introduction, updated to integrate concepts and procedures associated with computers. Computation, approximation, interpolation, numerical differentiation and integration, smoothing of data, other topics in lucid presentation. Includes 150 additional problems in this edition. Bibliography.
Multiple solutions of steady-state Poisson–Nernst–Planck equations with steric effects
International Nuclear Information System (INIS)
Lin, Tai-Chia; Eisenberg, Bob
2015-01-01
Experiments measuring currents through single protein channels show unstable currents. Channels switch between ‘open’ or ‘closed’ states in a spontaneous stochastic process called gating. Currents are either (nearly) zero or at a definite level, characteristic of each type of protein, independent of time, once the channel is open. The steady state Poisson–Nernst–Planck equations with steric effects (PNP-steric equations) describe steady current through the open channel quite well, in a wide variety of conditions. Here we study the existence of multiple solutions of steady state PNP-steric equations to see if they themselves, without modification or augmentation, can describe two levels of current. We prove that there are two steady state solutions of PNP-steric equations for (a) three types of ion species (two types of cations and one type of anion) with a positive constant permanent charge, and (b) four types of ion species (two types of cations and their counter-ions) with a constant permanent charge but no sign condition. The excess currents (due to steric effects) associated with these two steady state solutions are derived and expressed as two distinct formulas. Our results indicate that PNP-steric equations may become a useful model to study spontaneous gating of ion channels. Spontaneous gating is thought to involve small structural changes in the channel protein that perhaps produce large changes in the profiles of free energy that determine ion flow. Gating is known to be modulated by external structures. Both can be included in future extensions of our present analysis. (paper)
Implicit unified gas-kinetic scheme for steady state solutions in all flow regimes
Zhu, Yajun; Zhong, Chengwen; Xu, Kun
2016-06-01
This paper presents an implicit unified gas-kinetic scheme (UGKS) for non-equilibrium steady state flow computation. The UGKS is a direct modeling method for flow simulation in all regimes with the updates of both macroscopic flow variables and microscopic gas distribution function. By solving the macroscopic equations implicitly, a predicted equilibrium state can be obtained first through iterations. With the newly predicted equilibrium state, the evolution equation of the gas distribution function and the corresponding collision term can be discretized in a fully implicit way for fast convergence through iterations as well. The lower-upper symmetric Gauss-Seidel (LU-SGS) factorization method is implemented to solve both macroscopic and microscopic equations, which improves the efficiency of the scheme. Since the UGKS is a direct modeling method and its physical solution depends on the mesh resolution and the local time step, a physical time step needs to be fixed before using an implicit iterative technique with a pseudo-time marching step. Therefore, the physical time step in the current implicit scheme is determined by the same way as that in the explicit UGKS for capturing the physical solution in all flow regimes, but the convergence to a steady state speeds up through the adoption of a numerical time step with large CFL number. Many numerical test cases in different flow regimes from low speed to hypersonic ones, such as the Couette flow, cavity flow, and the flow passing over a cylinder, are computed to validate the current implicit method. The overall efficiency of the implicit UGKS can be improved by one or two orders of magnitude in comparison with the explicit one.
Numerical analysis of hydrodynamic journal bearings lubricated with ferrofluid
Montazeri, H.
2008-01-01
The current work focuses on studying the hydrodynamic characteristics of flow in journal bearings lubricated with ferrofluid. The bearing has an infinite length and operates under incompressible laminar flow and steady conditions. Assuming linear behaviour for the magnetic material of the
An analysis of 3D particle path integration algorithms
International Nuclear Information System (INIS)
Darmofal, D.L.; Haimes, R.
1996-01-01
Several techniques for the numerical integration of particle paths in steady and unsteady vector (velocity) fields are analyzed. Most of the analysis applies to unsteady vector fields, however, some results apply to steady vector field integration. Multistep, multistage, and some hybrid schemes are considered. It is shown that due to initialization errors, many unsteady particle path integration schemes are limited to third-order accuracy in time. Multistage schemes require at least three times more internal data storage than multistep schemes of equal order. However, for timesteps within the stability bounds, multistage schemes are generally more accurate. A linearized analysis shows that the stability of these integration algorithms are determined by the eigenvalues of the local velocity tensor. Thus, the accuracy and stability of the methods are interpreted with concepts typically used in critical point theory. This paper shows how integration schemes can lead to erroneous classification of critical points when the timestep is finite and fixed. For steady velocity fields, we demonstrate that timesteps outside of the relative stability region can lead to similar integration errors. From this analysis, guidelines for accurate timestep sizing are suggested for both steady and unsteady flows. In particular, using simulation data for the unsteady flow around a tapered cylinder, we show that accurate particle path integration requires timesteps which are at most on the order of the physical timescale of the flow
Controlling Unknown Saddle Type Steady States of Dynamical Systems with Latency in the Feedback Loop
DEFF Research Database (Denmark)
Tamasevicius, Arunas; Bumeliene, Skaidra; Tamaseviciute, Elena
2009-01-01
We suggest an adaptive control technique for stabilizing saddle type unstable steady states of dynamical systems. The controller is composed of an unstable and a stable high-pass filters operating in parallel. The mathematical model is considered analytically and numerically. The conjoint...... controller is sufficiently robust to time latencies in the feedback loop. In addition, it is not sensitive to the damping parameters of the system and is relatively fast. Experiments have been performed using a simplified version of the electronic Young-Silva circuit imitating behavior of the Duffing...
WRAP: a water reactor analysis package
International Nuclear Information System (INIS)
Anderson, M.M.
1977-06-01
The modular computational system known as the Water Reactor Analysis Package (WRAP) has been developed at the Savannah River Laboratory. WRAP is essentially a reprogrammed version of the RELAP4 computer code with an extensively restructured input format, a dynamic dimensioning capability and additional computational capabilities such as an automatic steady-state option for pressurized water reactors and an automatic restart capability with provision for renodalization. The report describes the capabilities of WRAP at its current stage of development. The addition of new capabilities (e.g., a BWR steady-state capability), the inclusion of improved models (e.g., models in RELAP4/M0D8) and the development of improved numerical techniques to reduce execution time are being planned at this time
International Nuclear Information System (INIS)
Sarwar, J.; Georgakis, G.; Kouloulias, K.; Kakosimos, K.E.
2015-01-01
Highlights: • Experimental results on thermal analysis of a solar cavity for variable apertures. • Development of an optical model for energy transfer from light source to the cavity. • Development of a coupled ray tracing and heat transfer model for the cavity. • Validation of both the models with experimental measurements. • Use of the models to study new cases like the efficiency of the variable apertures. - Abstract: In this paper, experimental and numerical work have been undertaken to investigate the steady state temperatures throughout the day of a cylindrical solar receiver when using fixed and variable size apertures. A high flux solar simulator, consisting of a 7 kW xenon short arc lamp, is employed as a light source. The sunlight intensity variations at early morning (06:30), morning (07:15) and noon (12:00) time of a reference day are imitated by changing the input current to the lamp. Experiments have been performed with different aperture diameters across selected irradiance levels to imitate sunlight variations. An optical model is developed to simulate incident flux distribution and the output is compared with the experimental measurements for validation. A finite volume algorithm is developed, based on a coupled Monte Carlo heat transfer model, to calculate the steady state temperatures in the receiver. Experimental and numerical temperatures are compared and an excellent agreement with an average temperature difference of ±0.2%, is observed. The optimum aperture size varies with the change in irradiance intensity and therefore the time of day. Simulations for a 30 kW light source show that the daily steady state temperature differential for fixed apertures of 8–10 cm is 170–190 K. Variable apertures reduce power consumption by half when compared to fixed apertures. Variable apertures maintain steady state temperatures of 1000 K, 1100 K and 1200 K by consuming 26.8 kW day, 33.2 kW day and 26.9 kW day, respectively
Stationary Distribution and Thermodynamic Relation in Nonequilibrium Steady States
Komatsu, Teruhisa S.; Nakagawa, Naoko; Sasa, Shin-ichi; Tasaki, Hal; Ito, Nobuyasu
2010-01-01
We describe our recent attempts toward statistical mechanics and thermodynamics for nonequilibrium steady states (NESS) realized, e.g., in a heat conducting system. Our first result is a simple expression of the probability distribution (of microscopic states) of a NESS. Our second result is a natural extension of the thermodynamic Clausius relation and a definition of an accompanying entropy in NESS. This entropy coincides with the normalization constant appearing in the above mentioned microscopic expression of NESS, and has an expression similar to the Shannon entropy (with a further symmetrization). The NESS entropy proposed here is a clearly defined measurable quantity even in a system with a large degrees of freedom. We numerically measure the NESS entropy in hardsphere fluid systems with a heat current, by observing energy exchange between the system and the heat baths when the temperatures of the baths are changed according to specified protocols.
Cherkesov, L. V.; Shul'ga, T. Ya.
2018-01-01
The effect of seawater movement through the Kerch Strait for extreme deviations in the level and speed of currents in the Sea of Azov caused by the action of climate wind fields has been studied using the Princeton ocean model (POM), a general three-dimensional nonlinear model of ocean circulation. Formation of the water flow through the strait is caused by the long-term action of the same type of atmospheric processes. The features of the water dynamics under conditions of changing intensity and active wind direction have been studied. Numerical experiments were carried out for two versions of model Sea of Azov basins: closed (without the Kerch Strait) and with a fluid boundary located in the Black Sea. The simulation results have shown that allowance for the strait leads to a significant change in the velocities of steady currents and level deviations at wind speeds greater than 5 m/s. The most significant effect on the parameters of steady-state movements is exerted by the speed of the wind that generates them; allowance for water exchange through the strait is less important. Analysis of the directions of atmospheric circulation has revealed that the response generated by the movement of water through the strait is most pronounced when a southeast wind is acting.
Numeral-Incorporating Roots in Numeral Systems: A Comparative Analysis of Two Sign Languages
Fuentes, Mariana; Massone, Maria Ignacia; Fernandez-Viader, Maria del Pilar; Makotrinsky, Alejandro; Pulgarin, Francisca
2010-01-01
Numeral-incorporating roots in the numeral systems of Argentine Sign Language (LSA) and Catalan Sign Language (LSC), as well as the main features of the number systems of both languages, are described and compared. Informants discussed the use of numerals and roots in both languages (in most cases in natural contexts). Ten informants took part in…
International Nuclear Information System (INIS)
Kim, Kyung-O; Jeong, Hae Sun; Jo, Daeseong
2017-01-01
Highlights: • Employing the Radial Point Interpolation Method (RPIM) in numerical analysis of multi-group neutron-diffusion equation. • Establishing mathematical formation of modified multi-group neutron-diffusion equation by RPIM. • Performing the numerical analysis for 2D critical problem. - Abstract: A mesh-free method is introduced to overcome the drawbacks (e.g., mesh generation and connectivity definition between the meshes) of mesh-based (nodal) methods such as the finite-element method and finite-difference method. In particular, the Point Interpolation Method (PIM) using a radial basis function is employed in the numerical analysis for the multi-group neutron-diffusion equation. The benchmark calculations are performed for the 2D homogeneous and heterogeneous problems, and the Multiquadrics (MQ) and Gaussian (EXP) functions are employed to analyze the effect of the radial basis function on the numerical solution. Additionally, the effect of the dimensionless shape parameter in those functions on the calculation accuracy is evaluated. According to the results, the radial PIM (RPIM) can provide a highly accurate solution for the multiplication eigenvalue and the neutron flux distribution, and the numerical solution with the MQ radial basis function exhibits the stable accuracy with respect to the reference solutions compared with the other solution. The dimensionless shape parameter directly affects the calculation accuracy and computing time. Values between 1.87 and 3.0 for the benchmark problems considered in this study lead to the most accurate solution. The difference between the analytical and numerical results for the neutron flux is significantly increased in the edge of the problem geometry, even though the maximum difference is lower than 4%. This phenomenon seems to arise from the derivative boundary condition at (x,0) and (0,y) positions, and it may be necessary to introduce additional strategy (e.g., the method using fictitious points and
On numerical solution of Burgers' equation by homotopy analysis method
International Nuclear Information System (INIS)
Inc, Mustafa
2008-01-01
In this Letter, we present the Homotopy Analysis Method (shortly HAM) for obtaining the numerical solution of the one-dimensional nonlinear Burgers' equation. The initial approximation can be freely chosen with possible unknown constants which can be determined by imposing the boundary and initial conditions. Convergence of the solution and effects for the method is discussed. The comparison of the HAM results with the Homotopy Perturbation Method (HPM) and the results of [E.N. Aksan, Appl. Math. Comput. 174 (2006) 884; S. Kutluay, A. Esen, Int. J. Comput. Math. 81 (2004) 1433; S. Abbasbandy, M.T. Darvishi, Appl. Math. Comput. 163 (2005) 1265] are made. The results reveal that HAM is very simple and effective. The HAM contains the auxiliary parameter h, which provides us with a simple way to adjust and control the convergence region of solution series. The numerical solutions are compared with the known analytical and some numerical solutions
Numerical modeling techniques for flood analysis
Anees, Mohd Talha; Abdullah, K.; Nawawi, M. N. M.; Ab Rahman, Nik Norulaini Nik; Piah, Abd. Rahni Mt.; Zakaria, Nor Azazi; Syakir, M. I.; Mohd. Omar, A. K.
2016-12-01
Topographic and climatic changes are the main causes of abrupt flooding in tropical areas. It is the need to find out exact causes and effects of these changes. Numerical modeling techniques plays a vital role for such studies due to their use of hydrological parameters which are strongly linked with topographic changes. In this review, some of the widely used models utilizing hydrological and river modeling parameters and their estimation in data sparse region are discussed. Shortcomings of 1D and 2D numerical models and the possible improvements over these models through 3D modeling are also discussed. It is found that the HEC-RAS and FLO 2D model are best in terms of economical and accurate flood analysis for river and floodplain modeling respectively. Limitations of FLO 2D in floodplain modeling mainly such as floodplain elevation differences and its vertical roughness in grids were found which can be improve through 3D model. Therefore, 3D model was found to be more suitable than 1D and 2D models in terms of vertical accuracy in grid cells. It was also found that 3D models for open channel flows already developed recently but not for floodplain. Hence, it was suggested that a 3D model for floodplain should be developed by considering all hydrological and high resolution topographic parameter's models, discussed in this review, to enhance the findings of causes and effects of flooding.
Analysis of steady-state creep of Fe-Mo alloys from the viewpoint of recovery
International Nuclear Information System (INIS)
Maruyama, K.; Karashima, S.; Oikawa, H.
1979-01-01
A theoretical equation to d evaluate the steady-state creep-rates, d epsilon/dtsub(s), based on a recovery creep model is derived: epsilonsub(s)/dt proportional to r/sigma 2 sub(a) x lambda 2 , where r is the recovery rate, which can be determined from results of stress-reduction tests, deltasub(a) the applied stress, and lambda the dislocation link-length. Two cases of recovery are considered, i.e., recovery of dislocation networks at sub-boundaries and that of three-dimensional networks within subgrains. The high-temperature steady-state creep of Fe-Mo solid solutions, creep characteristics of which have been reported to be well rationalized as viscous glide creep, is analyzed using this equation. It is shown that stress dependence of d epsilon/dtsub(s) is well explained from the viewpoint of recovery, in which the activation and the annihilation of dislocations at sub-boundaries are considered to take place. (orig.) [de
Numerical modeling assistance system in finite element analysis for the structure of an assembly
International Nuclear Information System (INIS)
Nakajima, Norihiro; Nishida, Akemi; Kawakami, Yoshiaki; Suzuki, Yoshio; Sawa, Kazuhiro; Iigaki, Kazuhiko
2015-01-01
The objective of structural analysis and seismic response analysis are well recognized and utilized as one of sophisticated analysis tools for design objects in the nuclear engineering. The way to design nuclear facilities is always in compromising with many index, such as costs, performance, robustness and so on, but the most important issues is the safety. It is true the structural analysis and seismic response analysis plays an important role to insure the safety, since it is well known that Japan is always facing to the earthquake. In this paper, a numerical analysis's controlling and managing system is implemented on a supercomputer, which controls the modelling process and data treating for structural robustness, although a numerical analysis's manager only controls a structural analysis by finite element method. The modeling process is described by the list of function ID and its procedures in a data base. The analytical modeling manager executes the process by order of the lists for simulation procedures. The manager controls the intention of an analysis by changing the analytical process one to another. Modeling process was experimentally found that may subject to the intention of designing index. The numerical experiments were carried out with static analyses and dynamic analyses. The results of its experiment introduce reasonable discussion to understand the accuracy of simulation. In the numerical experiments, K, supercomputer is utilized by using parallel computing resource with the controlling and managing system. The structural analysis and seismic response analysis are done by the FIEST, finite element analysis for the structure of an assembly, which carries out the simulation by gathering components. As components are attached to one another to build an assembly, and, therefore, the interactions between the components due to differences in material properties and their connection conditions considerably affect the behavior of an assembly. FIESTA is