bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spurious, zeroth‐order entropy generation along a kinked wall
Authors: van der Maarel Eric , Koren Barry 
Published: November 2005

AbstractNumerical entropy generation is studied in the case of steady, subsonic Euler flow along a kinked solid wall. For a standard upwind finite volume discretization the numerical entropy error, a component of the global discretization error, appears to be zeroth‐order in mesh size. Two possible causes of the zeroth‐order entropy error are studied. First an investigation is made of the local truncation error on a kinked grid. Although this error also appears to be zeroth‐order in the neighbourhood of the kink, it probably does not cause the zeroth‐order entropy error. Next a study is made of the existence of a singularity in the exact solution. Probably, the Euler flow solution is singular at the kink in the wall. The form of this likely singularity is unknown. Therefore the construction of a computational method which uses a priori knowledge about the singularity is not possible. Finally it is shown by numerical experiments that the subsonic Euler flow along a kinked wall still can be computed with vanishing entropy errors by using an appropriate sequence of continuously curved walls which converge to the kinked wall in the limit of zero mesh width.
A numerical study of the turbulent flow around the stern of ship models
Authors: Tzabiras G. D. 
Published: November 2005

AbstractThe present work is concerned with the numerical calculation of the turbulent flow field around the stern of ship models. The finite volume approximation is employed to solve the Reynolds equations in the physical domain using a body‐fitted, locally orthogonal curvilinear co‐ordinate system. The Reynolds stresses are modelled according to the standard k‐ε turbulence model. Various numerical schemes (i.e. hybrid, skew upwind and central differencing) are examined and grid dependence tests have been performed to compare calculated with experimental results. Moreover, a direct solution of the momentum equations within the near‐wall region is tried to avoid the disadvantages of the wall function approach. Comparisons between calculations and measurements are made for two ship models, i.e. the SSPA and HSVA model.
Effect of river discharge on the circulation in the western Bay of Bengal
Authors: Dube S. K. , Sinha P. C. , Rao G. S. , Rao A. D. 
Published: November 2005

AbstractA three‐dimensional numerical model has been applied to study the impact of freshwater discharge from a river on the coastal circulation in the western Bay of Bengal. The basic dynamical framework of the model follows closely that described by Johns et al.1 for the simulation of coastal upwelling off the east coast of India. Using this model, experiments have been performed to investigate the impact of the freshwater discharge at the location of Godavari river along the east coast of India. A comparison of the model results, with and without the inclusion of river discharge, shows that the river discharge into the western Bay of Bengal suppresses the upwelling near the river mouth. Though there are no detailed observations on the flow structure near the mouth of the Godavari river, the computed results are in qualitative agreement with the observations documented by Rao and Jayaraman2 and Rao,3 who have shown that during monsoon period the upwelling off Godavari estuary is suppressed.
Generalization of physical component boundary fitted co‐ordinate (PCBFC) method for the analysis of free‐surface flow
Authors: Takizawa Akihiko , Koshizuka Seiichi , Kondo Shunsuke 
Published: November 2005

AbstractThis paper presents a systematic and theoretically consistent approach for the analysis of free‐surface flow, making use of a number of established ideas such as physical component, boundary‐fitted co‐ordinate (BFC) and Lagrangian front tracking. The approach extends, theoretically as well as numerically, the use of physical component to general non‐orthogonal moving grids and provides a numerically stable BFC method with little labour of free‐surface positioning, grid generation and grid renewal. The approach conserves mass even at the free surface and allows time step of the order of the Coulant number. The main body of the present paper starts with the definition of analytical space and Riemannian geometry intrinsic to the physical component by applying to it the theorems of differential geometry and manifold theory. Then the governing equations of flow and free surface for the physical component are defined in the general 3D form with the notation of the new Riemannian geometry. Numerical procedures and the fully discrete equations are also presented for the benefit of potential users. Finally, several 2D examples demonstrate the basic performance of the present method by showing the computability of complex free‐surface motion.
Buoyancy‐driven instability in a vertical cylinder: Binary fluids with Soret effect. Part II: Weakly non‐linear solutions
Authors: Hardin G. R. , Sani R. L. 
Published: November 2005

AbstractThe buoyancy‐driven instability of a monocomponent or binary fluid that is completely contained in a vertical circular cylinder is investigated, including the influence of the Soret effect for the binary mixture. The Boussinesq approximation is used, and weakly‐non‐linear solutions are generated via Galerkin's technique using an expansion in the eigensolutions of the associated linear stability problem. Various types of fluid mixtures and cylindrical domains are considered. Flow structure and associated heat transfer are computed and experimental observations are cited when possible.
Newton's method for solving heat transfer, fluid flow and interface shapes in a floating molten zone
Authors: Lan C. W. 
Published: November 2005

AbstractNewton's method is applied to the finite volume approximation for the steady state heat transfer, fluid flow and unknown interfaces in a floating molten zone. The streamfunction/vorticity and temperature formulation of the Navier–Stokes and energy equations and their associated boundary conditions are written in generalized curvilinear co‐ordinates and conservative law form with the Boussinesq approximation. During Newton iteration the ILU(0) preconditioned GMRES matrix solver is applied for solving the linear system, where the sparse Jacobian matrix is estimated by finite differences. Nearly quadratic convergence of the method is observed. Sample calculations are reported for sodium nitrate, a high‐Prandtl‐number material (Pr = 9.12). Both natural convection and thermocapillary flow as well as an overall mass balance constraint in the molten zone are considered. The effects of convection and heat input on the flow patterns, zone position and interface shapes are illustrated. After the lens effect due to the molten zone is considered, the calculated flow patterns and interface shapes are compared with the observed ones and are found to be in good agreement.
A partially implicit method for simulating viscous aerofoil flows
Authors: Badcock K. J. 
Published: November 2005

AbstractA partially implicit method for the unsteady compressible Navier‐Stokes equations is developed. The method is based on an explicit treatment of streamwise fluxes and an implicit treatment of normal fluxes. This leads to a linear system which is generated by an efficient finite difference procedure and which is block pentadiagonal. The method is tested on a shock‐induced oscillatory flow over an aerofoil. Parallel implementations of an explicit, fully implicit and partially implicit method are investigated.
A numerical method for accelerating the rate of convergence of the SIMPLE‐like algorithm for flow through a thin filter
Authors: Wen X. , Ingham D. B. 
Published: November 2005

AbstractThe control volume, finite difference method and the k‐ϵ tubulence model are employed in a numerical simulation of the turbulent fluid flow both outside and inside a blunt cylindrical sampler which houses a paper filter in its chamber. The presence of a paper filter, which has a very large resistance, results in a large pressure drop across the filter and this causes difficulties in making the SIMPLE or the SIMPLEC scheme converge. In order to improve the rate of convergence of the SIMPLE‐like algorithm when the resistance of the filter is very large, an average pressure correction formula is proposed. Based on global mass conservation, a line average pressure correction for the paper filter is derived using a modified Darcy law for a porous medium. A combination of this formula and the SIMPLE‐like algorithm can rapidly build up the pressure drop across the filter and hence dramatically improve the rate of convergence of the iterative scheme. Comparisons of the convergence histories and the numerical results for the fluid flow when using SIMPLE and SIMPLEC with the average pressure correction method show that the average pressure correction method for dealing with the paper filter significantly accelerates the rate of convergence of the iterative scheme.
Development of projection and artificial compressibility methodologies using the approximate factorization technique
Authors: Pentaris A. , Nikolados K. , Tsangaris S. 
Published: November 2005

AbstractPredictions for two‐dimensional, steady, incompressible flows under both laminar and turbulent conditions are presented. The standard k‐ϵ turbulence model is used for the turbulent flows. The computational method is based on the approximate factorization technique. The coupled approach is used to link the equations of motion and the turbulence model equations. Mass conservation is enforced by either the pseudocompressibility method or the pressure correction method. Comparison of the two methods shows a superiority of the pressure correction method. Second‐ and fourth‐order artifical dissipation terms are used in order to achieve good convergence and to handle the turbulence model equations efficiently. Several internal and external test cases are investigated, including attached and separated flows.
Finite element calculations and experimental verification of the unsteady potential flow in a centrifugal volute pump
Authors: Badie R. , Jonker J. B. , van den Braembussche R. A. 
Published: November 2005

AbstractIn this paper we present a finite‐element‐based methode for the calculation of the unsteady potential flow in rotor/stator configurations. A numerical algorithm was developed to calculate the two‐dimensional flow through a centrifugal volute pump, taking into account the width variation of the volute in the axial direction and the vortex wakes downstream of the impeller blades by a linearized vortex distribution. The pressure field was obtained from the unsteady Bernoulli equation, with the entire configuration of the pump being included in the calculations. For that purpose the computational domain was split into a region containing the rotor and one containing the stationary parts, each region being treated in a different co‐ordinate system. The corresponding finite element grids qare matched by an interface consisting of connect elements which move with time. The method is applied to a laboratory centrifugal pump set up at the Von Karman Institute for Fluid Dynamics, which made an experimental validation possible. The total head of the pump and the velocity and pressure fields were computed and analysed for various mass flows. The agreement with the experimental data was satisfactory. The deviation was largest at low mass flow, the maximum deviation in the velocity around the impeller being 10 per cent. The overall behaviour of the pump could be well predicted.
Calculation of Reynolds stresses in turbulent supersonic flows
Authors: Ladeinde Foluso , Intile John C. 
Published: November 2005

AbstractThe baseline numerical procedure of interest in this study combines flux vector splitting, flux difference splitting and an explicit treatment of the diffusion terms of the flow equations. The viscous terms are treated explicitly to preserve the wave propagation properties of the Euler fluxes and permit splitting. The experience with this scheme has been limited to laminar or, at best, ‘eddy viscosity’ flows. In this paper the applicability of the scheme is extended to include the calculation of turbulent Reynolds stresses in supersonic flows. The schemes and our implementation are discussed. Both laminar and turbulence subsets of the Reynolds/Favre‐averaged equations are tested, with a discussion of relative performance. The test problem for turbulence consists of a zero‐pressure‐gradient supersonic boundary layer as well as a supersonic boundary layer experiencing the combined effects of adverse pressure gradient, bulk compression and a concave streamline curvature. Excellent agreement with experimental measurements is observed for most of the quantities compared, which suggests that the numerical procedures presented in this paper are potentially very useful.
A finite element simulation of the cross‐effects of viscoelasticity and inertia in an agitated vessel
Authors: Anne‐Archard D. , Boisson H. C. 
Published: November 2005

AbstractNumerical simulation by a finite element method is used to examine the problem of the rotating flow of a viscoelastic fluid in a cylindrical vessel agitated with a paddle impeller. The mathematical model consists of a viscoelastic constitutive equation of Oldroyd B type coupled to the hydrodynamic equations expressed in a rotating frame. This system is solved by using an unsteady approach for velocity, pressure and stress fields. For Reynolds numbers in the range 0.1–10, viscoelastic effects are taken into account up to a Deborah number De of 1.33 and viscoelasticity and inertia cross‐effects are studied. Examining the velocity and stress fields as well as the power consumption, it is found that their evolutions are significantly different for low and moderate inertia. These results confirm the trends of experimental studies and show the specific contribution of elasticity without interference of the pseudoplastic character found in actual fluids.
A comparison of integration and interpolation Eulerian‐Lagrangian methods
Authors: Oliveira Anabela , Baptista António M. 
Published: November 2005

AbstractSelected finite element Eulerian‐Lagrangian methods for the solution of the transport equation are compared systematically in the relatively simple context of 1D, constant coefficient, conservative problems. A combination of formal analysis and numerical experimentation is used to characterize the stability and accuracy that results from alternative treatments of the concentrations at the feet of the characteristic lines. Within the methods analyzed, those that approach such treatment with the perspective of ‘integration’ rather than ‘interpolation’ tend to have superior accuracy. Exact integration leads to unconditional stability and excellent accuracy. Quadrature integration leads only to conditional stability, but newly derived criteria show that stability restrictions are relatively mild and should not preclude the usefulness of quadrature integration methods in a range of practical applications. While conclusions cannot be extended directly to multiple dimensions and complex flows and geometries, results should provide useful insight to the development and behaviour of specific Eulerian‐Lagrangian transport models.
Numerical simulation of axisymmetric unsteady incompressible flow by a vorticity‐velocity method
Authors: Li Yuan , Dexun Fu , Yanwen Ma 
Published: November 2005

AbstractA new numerical method for solving the axisymmetric unsteady incompressible Navier‐Stokes equations using vorticity‐velocity variables and a staggered grid is presented. The solution is advanced in time with an explicit two‐stage Runge‐Kutta method. At each stage a vector Poisson equation for velocity is solved. Some important aspects of staggering of the variable location, divergence‐free correction to the velocity field by means of a suitably chosen scalar potential and numerical treatment of the vorticity boundary condition are examined. The axisymmetric spherical Couette flow between two concentric differentially rotating spheres is computed as an initial value problem. Comparison of the computational results using a staggered grid with those using a non‐staggered grid shows that the staggered grid is superior to the non‐staggered grid. The computed scenario of the transition from zero‐vortex to two‐vortex flow at moderate Reynolds number agrees with that simulated using a pseudospectral method, thus validating the temporal accuracy of our method.
Solutions of magnetohydrodynamic problems based on a conventional computational fluid dynamics code
Authors: Sazhin S. S. , Makhlouf M. , Ishii T. 
Published: November 2005

AbstractIt is pointed out that there exists a hidden analogy between magnetohydrodynamic (MHD) and conventional computational fluid dynamic (CFD) equations. This allows the generalization of any conventional CFD code so that the effects of MHD can be accounted for. This generalization is actually made for the FLUENT CFD code. Although this generalized FLUENT code can easily be adjusted to any MHD environment, it has been specifically designed for metallurgical applications. Predictions of the code are validated against the analytical solutions for the Poiseuille‐Hartmann flow and for the shielding of magnetic field oscillations by a conducting medium (skin effect).
A control‐volume based finite element method for three‐dimensional incompressible turbulent fluid flow, heat transfer, and related phenomena
Authors: Costa V. A. F. , Oliveira L. A. , Figueiredo A. R. 
Published: November 2005

AbstractA control‐volume based finite element method of equal‐order type for three‐dimensional incompressible turbulent fluid flow, heat transfer, and related phenomena is presented. The discretization equations are based mainly on the physics of the phenomena under consideration, more than on mathematical arguments. Special emphasis is devoted to the discretization of the convective terms and the continuity equation, and to the treatment of the boundary conditions imposed by the use of a high Reynolds k‐ϵ, type turbulence model. The pressure‐velocity coupling in the fluid flow calculation is made from a derivative of the original SIMPLER method, without pressure correction. The discretized equations are solved in a sequential, rather than a coupled, form with significant advantage in the required computer time and storage. The method is an extension of a former version proposed by us for two‐dimensional, laminar problems, and is here successfully applied to the following situations: three‐dimensional deflected turbulent jet, and flows in 90° and 45° junctions of ducts with rectangular cross sections. The calculated results are in very good agreement with the experimental and numerical (obtained with the well established finite difference method) data available in the literature.
Assessment of some iterative methods for non‐symmetric linear systems arising in computational fluid dynamics
Authors: Soria Antonio , Ruel François 
Published: November 2005

AbstractVarious tests have been carried out in order to compare the performances of several methods used to solve the non‐symmetric linear systems of equations arising from implicit discretizations of CFD problems, namely the scalar advection‐diffusion equation and the compressible Euler equations. The iterative schemes under consideration belong to three families of algorithms: relaxation (Jacobi and Gauss‐Seidel), gradient and Newton methods. Two gradient methods have been selected: a Krylov subspace iteration method (GMRES) and a non‐symmetric extension of the conjugate gradient method (CGS). Finally, a quasi‐Newton method has also been considered (Broyden). The aim of this paper is to provide indications of which appears to be the most adequate method according to the particular circumstances as well as to discuss the implementation aspects of each scheme.
Multicomponent variance estimation for binary traits in family‐based studies
Authors: Noh M. , Yip B. , Lee Y. , Pawitan Y. 
Published: November 2005

AbstractIn biometrical genetic analyses of binary traits, the use of family data overcomes some limitations of twin studies, particularly in terms of sample size and types of genetic or environmental factors that can be estimated. However, because of computational problems, recent methods in the application of generalized linear mixed models for family data structure have limited the ability to handle large data sets with general covariates. In this paper, we investigate the use of the hierarchical likelihood approach to the analysis of binary traits from family data. In a simulation study, the method is shown to be highly accurate for the estimation of both the variance components and fixed regression parameters, even for small family sizes. For illustration, we analyze a real data set of familial aggregation of preeclampsia, a pregnancy‐induced hypertension. When possible, the analysis is compared with the exact maximum likelihood approach.Genet. Epidemiol.2005. © 2005 Wiley‐Liss, Inc.
His36Pro point‐mutated proteolipid protein retained in the endoplasmic reticulum of oligodendrocytes in the Shaking pup
Authors: Song Jonathan , Goetz Brian D. , Duncan Ian D. 
Published: November 2005

AbstractThe shaking pup (shp) is a canine mutation that affects the myelin protein proteolipid protein (PLP) and its smaller and less abundant isoform, DM20, with proline replacing histidine36, resulting in a severe myelin deficiency in the central nervous system. We present evidence that the mutation leads to disrupted trafficking of the shp PLP/DM20 within oligodendrocytes. Immunohistochemical studies revealed significantly reduced levels of PLP/DM20 and other major myelin components such as myelin basic protein (MBP), myelin associated glycoprotein (MAG), and 2′,3′‐cyclic nucleotide 3′‐phosphodiesterase (CNP) in shp myelin. The distribution of shp PLP/DM20 proteins were altered and mostly retained in perinuclear cytoplasm and proximal processes, which co‐localized with distended rough endoplasmic reticulum (RER) within oligodendrocytes. No abnormal accumulation of MAG, MBP, or CNP in the cell body was found. These results suggest that mutated PLP/DM20 in the shp could be selectively retained in RER, causing disruption of their translocation to the periphery to myelinate axons. © 2005 Wiley‐Liss, Inc.