bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetohydrodynamic steady flow computations in three dimensions
Authors: Lee Seungsoo , Dulikravich George S. 
Published: October 2005

AbstractA complete three‐dimensional mathematical model has been developed governing the steady, laminar flow of an incompressible fluid subjected to a magnetic field and including internal heating due to the Joule effect, heat transfer due to conduction, and thermally induced buoyancy forces. The thermally induced buoyancy was accounted for via the Boussinesq approximation. The entire system of eight partial differential equations was solved by integrating intermittently a system of five fluid flow equations and a system of three magnetic field equations and transferring the information through source‐like terms. An explicit Runge‐Kutta time‐stepping algorithm and a finite difference scheme with artificial compressibility were used in the general non‐orthogonal curvilinear boundary‐conforming co‐ordinate system. Comparison of computational results and known analytical solutions in two and three dimensions demonstrates high accuracy and smooth monotone convergence of the iterative algorithm. Results of test cases with thermally induced buoyancy demonstrate the stabilizing effect of the magnetic field on the recirculating flows.
Numerical computation of unsteady incompressible flow in complex geometry using a composite multigrid technique
Authors: Hinatsu M. , Ferziger J. H. 
Published: October 2005

AbstractThis paper presents a composite multigrid method and its application to a geometrically complex flow. The treatment of the interior boundary conditions within a composite multigrid strategy is described in detail for a 1D model equation. For the Navier‐Stokes equations a staggered grid technique is adopted for spatial discretization and a fractional step method is used for the time advance. Lid‐driven cavity flows are used to demonstrate the effectiveness of the method.
Numerical simulation of the reflection of a planar shock wave over a double wedge
Authors: Itoh K. , Takayama K. , Ben‐Dor G. 
Published: October 2005

AbstractA numerical code based on the upwind TVD scheme for simulating the various reflection processes of a planar shock wave over a concave or convex double wedge has been developed. The numerical results were compared with actual experiments and excellent agreement was obtained. The excellent agreement serves also as a validation of the shock‐capturing performance of the numerical scheme.
Time‐dependent solutions of viscous incompressible flows in moving co‐ordinates
Authors: Rosenfeld Moshe , Kwak Dochan 
Published: October 2005

AbstractA time‐accurate solution method for the incompressible Navier‐Stokes equations in generalized moving coordinates is presented. A finite volume discretization method that satisfies the geometric conservation laws for time‐varying computational cells is used. The discrete equations are solved by a fractional step solution procedure. The solution is second‐order‐accurate in space and first‐order‐accurate in time. The pressure and the volume fluxes are chosen as the unknowns to facilitate the formulation of a consistent Poisson equation and thus to obtain a robust Poisson solver with favourable convergence properties. The method is validated by comparing the solutions with other numerical and experimental results. Good agreement is obtained in all cases.
Higher‐order streamfunction‐vorticity formulation of 2D steady‐state Navier‐Stokes equations
Authors: Liao S. J. 
Published: October 2005

AbstractBased on regular boundary element method and a kind of linearity invariance under homotopy, a kind of numerical scheme of 2D steady‐state Navier‐Stokes equation in streamfunction‐vorticity formulation is described. The flow inside a square cavity is used to illustrate this numerical scheme.
α‐GMRES: A new parallelizable iterative solver for large sparse non‐symmetric linear systems arising from CFD
Authors: Xu X. , Qin N. , Richards B. E. 
Published: October 2005

AbstractLinearization of the non‐linear systems arising from fully implicit schemes in computational fluid dynamics often result in a large sparse non‐symmetric linear system. Practical experience shows that these linear systems are ill‐conditioned if a higher than first‐order spatial discretization scheme is used. To solve these linear systems, an efficient multilevel iterative method, the α‐GMRES method, is proposed which incorporates a diagonal preconditioning with a damping factor α so that a balanced fast convergence of the inner GMRES iteration and the outer damping loop can be achieved. With this simple and efficient preconditioning and damping of the matrix, the resulting method can be effectively parallelized. The parallelization maintains the effectiveness of the original scheme due to the algorithm equivalence of the sequential and the parallel versions.
Overlapping grids and multigrid methods for three‐dimensional unsteady flow calculations in IC engines
Authors: Tu J. Y. , Fuchs L. 
Published: October 2005

AbstractA new computational methodology with emphasis on using an overlapping grid technique and a multigrid method has been developed. The main feature of the present overlapping‐grid system is of extended flexibility to deal with three‐dimensional complex multicomponent geometries. The multigrid method is incorporated into this technique to accelerate the convergence of the numerical solution. The current scheme has been applied for computations of the laminar flows in the multicomponent configuration of internal combusion engines. The flow is governed by three‐dimensional, time‐dependent, incompressible Navier‐Stokes equations with the continuity equation. A time‐independent grid system is constructed for the moving boundary, i.e. the moving piston in the engine. This grid system is entirely different from others for the same problem in previous works. The performance of the present method has been validated by comparing the results with those from an equivalent, single‐grid method and those from experiments. In addition, the flexibility and potential of the method has been demonstrated by calculating several cases which would be very difficult to be handled by other schemes.
Application of generalized differential quadrature to solve two‐dimensional incompressible Navier‐Stokes equations
Authors: Shu Chang , Richards Bryan E. 
Published: October 2005

AbstractA global method of generalized differential quadrature is applied to solve the two‐dimensional incompressible Navier‐Stokes equations in the vorticity‐stream‐function formulation. Numerical results for the flow past a circular cylinder were obtained using just a few grid points. A good agreement is found with the experimental data.
Numerical simulation of a low‐emission gas turbine combustor using KIVA‐II
Authors: Yang S. L. , Chen R. , Cline M. C. , Nguyen H. L. , Micklow G. J. 
Published: October 2005

AbstractA numerical study was performed to investigate chemically reactive flows with sprays inside a staged turbine combustor (STC) using a modified version of the KIVA‐II code. This STC consists of a fuel nozzle (FN), a rich‐burn (RB) zone, a converging connecting pipe, a quick‐quench (QQ) zone, a diverging connecting pipe and a lean‐combustion (LC) zone. From the computational viewpoint, it is more efficient to split the STC into two subsystems, called FN/RB zone and QQ/LC zones, and the numerical solutions were obtained separately for each subsystem. This paper addresses the numerical results of the STC which is equipped with an advanced airblast fuel nozzle. The airblast nozzle has two fuel injection passages and four air flow passages. The input conditions used in this study were chosen similar to those encountered in advanced combustion systems. Preliminary results generated illustrate some of the major features of the flow and temperature fields inside the STC. Velocity, temperature and some critical species information inside the FN/RB zone are given. Formation of the co‐ and counter‐rotating bulk flow and the sandwiched‐ring‐shaped temperature field, typical of the confined inclined jet‐in‐cross‐flow, can be seen clearly in the QQ/LC zones. The calculations of the mass‐weighted standard deviation and the pattern factor of temperature revealed that the mixing performance of the STC is very promising. The temperature of the fluid leaving the LC zone is very uniform. Prediction of the NOx emission shows that there is no excessive thermal NOx produced in the QQ/LC zones for the case studied. From the results obtained so far, it appears that the modified KIVA‐II code can be used to guide the low‐emission combustion experiments.
Surface grid generation with a linkage to geometric generation
Authors: Suzuki Masahiro 
Published: October 2005

AbstractThis paper describes a new method to generate surface grids over complex configurations defined by a geometric generation system. The scheme is designed for direct utilization of the surface definition provided by a geometric modeller based on a boundary representation (the so‐called B‐rep modeller). Thus, the conversion of the geometric representation for the surface grid generator is not required. Consequently, this technique eliminates not only laborious tedium in the conversion of data, but also errors in the representation of the surface induced in the process of the conversion.The proposed method is accomplished over several stages. First, the triangulation is performed on the surface of the geometry, on which the area to be grided is laid. Then linear partial differential equations are mapped and solved on these triangular elements. Finally, the surface grid is constructed by searching for the contours inside the solution domain. After the co‐ordinate values of the grid points are obtained by a linear interpolation within each triangular element, these values are mapped onto the surface of the geometry through surface parametric functions provided by the B‐rep modeller.An example of generating surface grid over a car configuration is given to illustrate the capability of the method.
Vectorized poisson solvers for the Navier–Stokes equations
Authors: Armfield S. W. 
Published: October 2005

AbstractThe advent of vector and massively parallel computers offers researchers the possibility of enormous gains in execution time for scientific and engineering programs. From the numerical point of view, such programs are frequently based on the inversion of sparse, diagonally banded matrices. Conventional scalar solvers often perform poorly on vector machines due to short effective vector lengths, and thus appropriate methods must be chosen for use with vector machines. In this paper a number of commonly used solvers are tested for the Navier–Stokes equations, in both scalar and vector form, on two vector architecture machines. A new method is presented which performs well in both vector and scalar form on a range of vector architectures.
Identification of shallow sea models
Authors: ten Brummelhuis P. G. J. , Heemink A. W. , van den Boogaard H. F. P. 
Published: October 2005

AbstractIn this paper we consider a parameter estimation procedure for shallow sea models. The method is formulated as a minimization problem. An adjoint model is used to calculate the gradient of the criterion which is to be minimized. In order to obtain a robust estimation method, the uncertainty of the open boundary conditions can be taken into acoount by allowing random noise inputs to act on the open boundaries. This method avoids the possibility that boundary errors are interpreted by the estimation procedure as parameter fluctuations. We apply the parameter estimation method to identify a shallow sea model of the entire European continental shelf. First, a space‐varying bottom friction coefficient is estimated simultaneously with the depth. The second application is the estimation of the parameterization of the wind stress coefficient as a function of the wind velocity. Finally, an uncertain open boundary condition is included. It is shown that in this case the parameter estimation procedure does become more robust and produces more realistic estimates. Furthermore, an estimate of the open boundary conditions is also obtained.
Non‐symmetric CG‐like schemes and the finite element solution of the advection–dispersion equation
Authors: Peters Alexander 
Published: October 2005

AbstractSeven leading iterative methods for non‐symmetric linear systems (GMRES, BCG, QMR, CGS, Bi‐CGSTAB, TFQMR and CGNR) are compared in the specific context of solving the advection–dispersion equation by a classic approach: The space derivatives are approximated by linear finite elements while an implicit scheme is used to integrate the time derivatives. Convergence formulas that predict the behaviour of the iterative methods as a function of the discretization parameters are developed and validated by experiments. It is shown that all methods converge nicely when the coefficent matrix of the linear system is close to normal and the finite element approximation of the advection–dispersion equation yields accurate results.
Numerical simulation of the head‐on reflection of a regular reflection
Authors: Falcovitz J. , Alfandary G. , Ben‐Dor G. 
Published: October 2005

AbstractThe head‐on collision and subsequent reflection of a Regular Reflection (RR) from the end‐wall of a shock tube has been investigated both experimentally and numerically for two different incident shock wave Mach numbers and two different reflecting wedge angles.The agreement between the double‐exposure holographic interferograms and the numerical simulations which were obtained using a GRP based numerical code, was found to be excellent in the RR region and very good behind the head‐on reflected RR.The overall good agreement between the computed and experimental constant‐density contours (isopycnics) constitutes a validation of the computational method, including the oblique‐wall boundary condition.
Iterative solution techniques for the stokes and Navier‐Stokes equations
Authors: Ramage Alison , Wathen Andrew J. 
Published: October 2005

AbstractThe linear system arising from a Lagrange‐Galerkin mixed finite element approximation of the Navier–Stokes and continuity equations is symmetric indefinite and has the same block structure as a system arising from a mixed finite element discretization of a Stokes problem. This paper considers the iterative solution of such a system, comparing the performance of the one‐level preconditioned conjugate residual method for indefinite matrices with that of a more traditional two‐level pressure correction approach. Asymptotic estimates for the amount of work involved in each method are given together with the results of related numerical experiments.
Control volume finite element solution of confined turbulent swirling flows
Authors: Elkaïm D. , McKenty F. , Reggio M. , Camarero R. 
Published: October 2005

AbstractA control volume finite element method that uses a triangular grid has been applied for solving confined turbulent swirling flows. To treat the velocity‐pressure coupling, the vorticity‐streamfunction formulation has been used. For turbulence effects the k‐ϵ model has been adopted. Consistent with the use of wall functions in the near‐wall regions, a boundary condition for the calculation of the vorticity at computational boundaries is proposed and used effectively. The discretized equations are obtained by making use of an exponential interpolation function. Its use has been beneficial in reducing numerical diffusion. Comparisons of the current predictions with available experimental and numerical data from the literature showed generally fair agreement.
Exact fully 3D Navier–Stokes solutions for benchmarking
Authors: Ethier C. Ross , Steinman D. A. 
Published: October 2005

AbstractUnsteady analytical solutions to the incompressible Navier–Stokes equations are presented. They are fully three‐dimensional vector solutions involving all three Cartesian velocity components, each of which depends non‐trivially on all three co‐ordinate directions. Although unlikely to be physically realized, they are well suited for benchmarking, testing and validation of three‐dimensional incompressible Navier–Stokes solvers. The use of such a solution for benchmarking purposes is described.
TVD algorithms for the solution of the compressible Euler equations on unstructured meshes
Authors: Lyra P. R. M. , Morgan K. , Peraire J. , Peiró J. 
Published: October 2005

AbstractThe Galerkin finite element method is used as the basis for the construction of schemes for the solution of the two‐dimensional compressible Euler equations on unstructured triangular grids. The use of a side‐based data structure readily allows for the construction of a local (structured) stencil and the incorporation of a high‐resolution shock‐capturing method formulated within the TVD concept. The essential features of the finite element side‐based scheme and the ID TVD approach are described and their numerical implementation is discussed. The choice of limiters and the support for their computation are analysed and the solutions of some inviscid flows, obtained by advancing explicitly in time, are presented.
An unstructured grid algorithm for the solution of Maxwell's equations in the time domain
Authors: Morgan K. , Hassan O. , Peraire J. 
Published: October 2005

AbstractThe solution of problems involving the scattering of plane electromagnetic waves by perfectly conducting obstacles is considered. The governing equations are Maxwell's equations, which are expressed in a conservation form. The solution is then obtained by modifying a technique which was applied originally to the solution of the compressible Euler equations on a mesh consisting of an unstructured assembly of linear triangular elements in 3D. The computed solution can be used to determine the radar cross‐section of the scatterer.
Numerical calculation of the viscous flow around a propeller shaft configuration
Authors: Oh Keon‐je , Kang Shin‐hyoung 
Published: October 2005

AbstractA viscous flow simulation method is developed to calculate the flow around a marine propeller configuration and applications to propeller flow under uniform flow conditions are presented. The continuity and Reynolds‐averaged Navier‐Stokes equations are solved in a rotating co‐ordinate system using the finite volume method. The turbulent Reynolds stresses are modelled by the modified k‐ϵ turbulence model to account for swirling flows. The general characteristics of propeller flow can be reasonably predicted in the slipstream of the propeller wake and the results of the circumferentially averaged velocity profiles show good agreement with experimental data. The tip vortex can be captured near the tip of the blade, but the strength of the vortex is weakly predicted in comparison with the measured one. The predictions of the boundary layer on the blade show reasonable agreement with measurements in the turbulent boundary layer region. However, the laminar and transitional boundary layers cannot be represented, because the flow is assumed to be turbulent in the calculation. The thrust and torque coefficients are adequately estimated in comparison with measured data for a wide range of advance coefficients.
Numerical analysis of 2D vortex‐induced oscillations of a circular cylinder
Authors: Wei R. , Sekine A. , Shimura M. 
Published: October 2005

AbstractIn this paper a finite element version of the direct Laplacian method is applied to flows around an oscillating body, using the arbitrary Langrangian‐Eulerian (ALE) formulation for the partial domain around the body. This numerical calculation has been successfully conducted for vortex‐induced, cross‐flow oscillations of a circular cylinder under the same conditions as for Anagnostopoulos and Bearman's experiment (J. Fluids Struct., 6, 39–50 (1992)), in which the Reynolds number ranged between 90 and 150, a regime where the vortex street is fully laminar. The numerical calculation results have been compared with the experimental data in order to check the calculational accuracy.
Biological response to a new composite polymer augmentation device used for cruciate ligament reconstruction
Authors: Dürselen Lutz , Häfner Monika , Ignatius Anita , Kraft Klaus , Hollstein Elke , Pokar Sven , Dauner Martin , Claes Lutz , Friemert Benedikt 
Published: October 2005

AbstractA resorbable composite augmentation cord braided of poly(L‐lactide) and poly(L‐lactide‐co‐glycolide) fibers was designed for the temporary protection of repaired cruciate ligaments. This study examined the biocompatibility of the new device and the influence of augmentation duration on ligament healing in a sheep model. The anterior cruciate ligament (ACL) was cut close to the femoral insertion and reinserted with sutures. The repaired ACLs were augmented with the slowly degrading new composite cord and alternatively with a faster degrading polydioxanone cord (PDS). A tendon graft group (gold standard) served as control. Histological evaluation and biomechanical testing were performed after 6 months. The composite cord showed no signs of degradation, whereas the PDS was intra‐articularly resorbed. Both devices showed only minor foreign body reactions, proving their good biocompatibility. However, 9 of 11 composite cords had ruptured too early because of fatigue at the bone tunnel entrances. All operated knees were less stable than the nonoperated collateral joints. Knees equipped with the composite cord showed the largest anterior instabilities, whereas the PDS‐augmented group exhibited in some cases knee instabilities comparable with that of the tendon group. A positive effect of a longer mechanical protection by a slowly degrading augmentation could not yet be shown. The fatigue strength of the device still needs improvement. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006
Micro‐tensile bond strength of sound and caries‐affected primary tooth dentin measured with original designed jig
Authors: Hosoya Yumiko , Kawada Eiji , Ushigome Toshiaki , Oda Yutaka , Garcia‐Godoy Franklin 
Published: October 2005

AbstractTo measure the micro‐tensile bond strength (MTBS) on sound and caries‐affected primary tooth dentin using an original designed jig that was developed for making symmetric and uniformly‐sized specimens for the micro‐tensile strength testing. The MTBS of dumbbell‐shaped specimens and matchstick‐shaped specimens were measured. Dumbbell‐shaped specimens: The occlusal surfaces of 15 sound primary molars were ground with a water‐cooled air turbine using a diamond bur. The adhesive systems and resin‐based composites were Clearfil SE Bond and Clearfil AP‐X (SE group) and Single Bond and Z250 (SB group). Matchstick‐shaped specimens: Sixteen primary molars (5 sound and 11 carious) were used. The occlusal surfaces of sound teeth were ground with a water‐cooled air turbine using a diamond bur. Infected dentin was determined by a caries detecting dye solution and removed with a round‐shaped steel bur under water‐cooling and with a hand instrument. SE was applied. Data was statistically analyzed using ANOVA and Fisher's PLSD at p < 0.05. The MTBSs (MPa) for the dumbbell‐shaped specimens were 8.9 ± 7.0 in the SE group and 10.3 ± 5.8 in the SB group and that for the matchstick‐shaped specimens were 9.0 ± 6.3 in the sound–SE group and 9.2 ± 5.8 in the carious–SE group. No significant difference was observed among them. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006