bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical simulation of silencers
Authors: Cooke Charlie H. , Fansler Kevin S. 
Published: August 2005

AbstractThe problem of attenuating the noise from weapons firing is studied experimentally and numerically. As a possible method of attenuating the noise significantly, a silencer with no internal baffles is attached to the M242 cannon. The internal pressures inside the muffler are measured. The near‐field overpressures outside the muffler at various polar angles are also measured. A numerical simulation of the flow through the muffler is performed, using Harten's shock‐capturing method to solve the Euler equations of ideal compressible flow. The numerical simulation yields a detailed picture of the flow field as displayed by the pressure and Mach contours. Pressure–time curves at selected locations are obtained and compared with experimental data. There is good agreement, except that the numerical simulation generates more vigorous oscillations.
Quantum phenomena in numerical wave propagation
Authors: Vichnevetsky Robert 
Published: August 2005

AbstractThe analysis of wave propagation in computing domains where hyperbolic equations are approximated with finite differences has revealed surprising analogies between this subject and quantum mechanics. The first part of this paper consists of a review of the corresponding phenomena and of their description with known results from numerical analysis and wave propagation theory. We then introduce a new formalism, containing a finite difference analogue of the classical Schrodinger equation, which describes the ensemble of those phenomena. The validity of the new formalism is verified by its agreement with known theoretical results in numerical wave propagation (it contains in fact many of those results) as well as with new data obtained in numerical experiments with monochromatic waves which display properties similar to those of Schrödinger's wavefunction for the quantum mechanics description of the equivalent experiments with physical particles. While the results of this paper are derived in the context of wave propagation in computing domains, they remain applicable to similar aspects of wave propagation in other (physical) periodic structures.
Low Reynolds number hydrodynamic interaction of a solid particle with a planar wall
Authors: Ascoli E. P. , Dandy D. S. , Leal L. G. 
Published: August 2005

AbstractThe slow viscous flow problem of an arbitrary solid particle in motion near a planar wall is recast into a boundary integral formulation. The present formulation employs the Green function appropriate to the planar wall problem and is developed in sufficient generality to allow calculations for arbitrary particles in any base flow which satisfies Stokes equations and no‐slip on the wall. The resulting integral equations are easily discretized and solved for the particle surface tractions. Calculations are performed for axisymmetric motions of a variety of ellipsǫids near the planar wall. Agreement with existing theory is excellent.
Coupled heat transfer and viscous flow, and magnetic effects in weld pool analysis
Authors: McLay R. , Carey G. F. 
Published: August 2005

AbstractA finite element formulation and analysis is developed to study coupled heat transfer and viscous flow in a weld pool. The thermal effects generate not only buoyancy forces but also a variation in the surface tension which acts to drive the viscous flow in the molten weld pool. A moving phase boundary separates molten and solid material. Numerical experiments reveal the nature of the highly convective flow in the weld pool and the associated thermal profiles. The relative importance of buoyancy, surface tension, phase change, convection, etc. are examined. We also consider the sensitivity of the solution to the finite element mesh and related non‐linear numerical instabilities. Of particular interest is the coupling of the thermal and viscous flow fields for the case when radial flow is inward or outward.
Numerical simulation and hydrodynamic visualization of transient viscous flow around an oscillating aerofoil
Authors: Daube O. , Phuoc L. Ta , Dulieu A. , Coutanceau M. , Ohmi K. , Texier A. 
Published: August 2005

AbstractUnsteady viscous flow around a large‐amplitude and high‐frequency oscillating aerofoil is examined in this paper by numerical simulation and experimental visualization. The numerical method is based on the combination of a fourth‐order Hermitian finite difference scheme for the stream function equation and a classical second‐order scheme to solve the vorticity transport equation. Experiments are carried out by a traditional visualization method using solid tracers suspended in water. The comparison between numerical and experimental results is found to be satisfactory. Time evolutions of the flow structure are presented for Reynolds numbers of 3 × 103 and 104. The influence of the amplitude and frequency of the oscillating motion on the dynamic stall is analysed.
Second‐moment closure and its use in modelling turbulent industrial flows
Authors: Launder B. E. 
Published: August 2005

AbstractSecond‐moment turbulence models focus directly on the transport equations for the Reynolds stresses rather than supposing the stress and strain fields to be directly linked via an eddy viscosity. This elaboration enables the effects of complex strains and force fields on the turbulence structure to be better captured. The paper summarizes the principal modelling strategies adopted for the unknown processes in these equations and presents the forms that have been found most useful in engineering calculations. Methods adopted for overcoming significant problems of numerical instability and lack of convergence compared with eddy‐viscosity‐based schemes are also presented. Applications involving momentum and heat transfer in complex flows are drawn from the advanced technology sectors of the power generation and aircraft industries.
On the application of pseudospectral FFT techniques to non‐periodic problems
Authors: Biringen S. , Kao K. H. 
Published: August 2005

AbstractThe reduction‐to‐periodicity method using the pseudospectral fast Fourier transform (FFT) technique is applied to the solution of non‐periodic problems, including the two‐dimensional incompressible Navier–Stokes equations. The accuracy of the method is explored by calculating the derivatives of given functions, one‐ and two‐dimensional convective‐diffusive problems, and by comparing the relative errors due to the FFT method with a second‐order finite difference (FD) method. Finally, the two‐dimensional Navier–Stokes equations are solved by a fractional step procedure using both the FFT and the FD methods for the driven cavity flow and the backward‐facing step problems. Comparisons of these solutions provide a realistic assessment of the FFT method.
Comment on ‘generalized potential flow theory and direct calculation of velocities applied to the numerical solution of the Navier–Stokes and the Boussinesq equations’
Authors: Abdallah S. , Deutsch S. 
Published: August 2005

AbstractIn a recent paper a generalized potential flow theory and its application to the solution of the Navier–Stokes equation are developed.1 The purpose of this comment is to show that the analysis presented in that paper is in general not correct. We note that the theoretical development of Reference 1 is in fact an extension—although not cited—of some work first done by Hawthorne for steady inviscid flow.2 Hawthorne's solution is correct, and his analysis, which we briefly describe, provides a useful introduction to this note.
Numerical studies of slow viscous rotating flow past a sphere. II
Authors: Raghavarao C. V. , Pramadavalli K. 
Published: August 2005

AbstractThe Navier–Stokes equations, which are the governing equations for a steady, viscous, incompressible fluid rotating about the z‐axis with angular velocity ω, are linearized using the Oseen approximation. Two parameters, namely the Reynolds number Re = Ua/v and Reω = 2ωa2/v (the Reynolds number w.r.t. rotation), enter the linearized equations. These equations are solved by the Peaceman–Rachford ADI method and the resulting algebraic equations are solved by the SOR method. Streamlines are plotted and compared with the Oseen solution for the non‐rotating case. The magnitude of the vorticity vector with increasing θ is also plotted.
Two‐dimensional subcritical and supercritical open channel flow calculation using a time‐marching method
Authors: Soulis Johannes Vassiliou 
Published: August 2005

AbstractA time‐marching method is presented for the calculation of two‐dimensional, high‐speed channel flow, including the usually neglected terms of slope and bottom friction. Time‐marching methods are potentially the most flexible means of calculating flow through geometrically complex channel passages, since they can readily deal with subcritical and supercritical flows. The adopted numerical scheme comes straight from gas flow computations in turbomachines. The flow is assumed to be fully mixed in the vertical direction, so that vertical variations may be neglected. Comparisons with other numerical solutions for various open channel configurations show that the proposed approach is a comparatively accurate, reliable and fast technique. It can be utilized for open channel designs.
Numerical simulation of an impinging jet on a flat plate
Authors: Chuang Shu‐Hao 
Published: August 2005

AbstractTwo‐dimensional normal impinging jet flowfields, with or without an upper plate, were analysed by employing an implicit bidiagonal numerical method developed by Lavante and Thompkins Jr. The Jones–Launder K–ϵ two‐equation turbulent model was employed to study the turbulent effects of the impinging jet flowfield. The upper plate surface pressure, the ground plane pressure and other physical parameters of the momentum flowfield were calculated at various jet exit height and jet inlet Reynolds numbers. These results were compared with those of Beam and Warming's numerical method, Hsiao and Chuang, and others, along with experimental data. The potential core length of the impinging jet without an upper plate is longer than that of the free jet because of the effects of the ground plane, while the potential core length of the impinging jet with an upper plate is shorter than that of the free jet because of the effects of the upper plate. This phenomenon in the present analysis provides a fundamental numerical study of an impinging jet and a basis for further analysis of impinging jet flowfields on a variable angle plate.
Marangoni convection in weld pools with a free surface
Authors: Tsai M. C. , Kou Sindo 
Published: August 2005

AbstractA steady‐state two‐dimensional model of heat transfer and fluid flow was developed to describe Marangoni convection in the weld pool. Both the pool surface and the fusion boundary were calculated. The validity of the model was verified against an asymptotic solution for Marangoni‐convection‐induced free surface geometry. Two different cases were studied, i.e. a negative surface tension temperature coefficient ∂γ/∂T a positive one, and the resultant shapes of the weld pool surface were compared.
Spectral simulations of oscillatory convection at low Prandtl number
Authors: Pulicani J. P. , Del Arco E. Crespo , Randriamampianina A. , Bontoux P. , Peyret R. 
Published: August 2005

AbstractPseudospectral methods are used for the computation of the time‐dependent convective flows which arise in shallow cavities filled with low‐Prandtí‐number liquids when submitted to a horizontal temperature gradient. In similar situations several former numerical results have been shown to disagree about the determination of the threshold of oscillations and about the subsequent supercritical regimes. Two different tau–Chebyshev methods based on the vorticity–streamfunction formulation and using multistep time schemes are considered. Their results are discussed to assess the validity of the solutions. The physical problems concern rectangular cavities which involve either a rigid or a stress‐free top wall and either conducting or insulating horizontal walls. Aside from the prediction of the onset of oscillations, which is discussed in the various situations with respect to the results of linear and non‐linear analyses and to other computational results, the present study exhibits some bifurcation sequences and a hysteresis cycle at moderate Grashof numbers which are associated to the occurrence of multiple solutions.
Fluid flow in curved ducts
Authors: Jayanti S. , Hewitt G. F. , Kightley J. R. 
Published: August 2005

AbstractThe advent of standard algorithms for the numerical solution of partial differential equations has given researchers a new tool for fluid flow calculations. In this paper, single‐phase flow in curved ducts is numerically simulated by imposing a spatially varying centrifugal force on a fluid flowing in a straight tube. The resulting set of partial differential equations is solved using the HARWELL‐FLOW3D computer program. Comparison with other numerical and experimental results shows that this simplified formulation gives accurate results. The model neglects certain geometric terms of the order d/D, the duct‐to‐coil diameter ratio. The effect of these terms is investigated by considering the flow in a 90° bend for large d/D. It is shown that while there may be significant error in the prediction of the local variables for large d/D, the circumference‐averaged quantities are well predicted.
An improved SIP scheme for numerical solutions of transonic streamfunction equations
Authors: Bao‐Guo Wang , Nai‐Xing Chen 
Published: August 2005

AbstractA new improved strongly implicit procedure (SIP) is presented for solving large sets of transonic streamfunction equations with matrix of coefficients [B]. This algorithm has several advantages over those now in use. First, Stone's auxiliary matrix [B′] is non‐symmetric, while in the present scheme the auxiliary matrix [B′] is symmetric and the matrix [B + B′] is positive definite and symmetric when [B] is a symmetric matrix. This ensures the numerical stability of the iterative algorithms. Secondly, for an appropriate choice of iterative parameter ω, the rate of convergence of the new iterative procedure should be faster than the original SIP scheme.Numerical results of the blade‐to‐blade flows are given with the present scheme. It is shown that the algorithm is efficient and robust.
Simulation of planar converging flow of a Leonov viscoelastic fluid
Authors: Tseng Hsieng‐Cheng , Lin Gwo‐Geng 
Published: August 2005

AbstractAn efficient finite element algorithm is presented to simulate the planar converging flow for the viscoelastic fluid of the Leonov model. The governing equation set, composed of the continuity, momentum and constitutive equations for the Leonov fluid flow, is conveniently decoupled and a two‐stage cyclic iteration technique is employed to solve the velocity and elastic strain fields separately. Artificial viscosity terms are imposed on the momentum equations to relax the elastic force and data smoothing is performed on the iterative calculations for velocities to further stabilize the numerical computations. The calculated stresses agree qualitatively with the experimental measurements and other numerically simulated results available in the literature. Computations were successful to moderately high values of Deborah number of about 27·5.
Implicit finite element methods for two‐phase flow in oil reservoirs
Authors: Langtangen Hans Petter 
Published: August 2005

AbstractThe equations governing immiscible, incompressible, two‐phase, porous media flow are discretized by generalized streamline diffusion Petrov–Galerkin methods in space and by implicit differences in time. Systems of non‐linear algebraic equations are solved by Newton–Raphson iteration employing ILU‐preconditioned conjugate‐gradient‐like methods to the non‐symmetric matrix system in each iteration. The resulting solution methods are robust, enable complex grids with irregular nodal orderings and allow capillary effects.Several numerical formulations are tested and compared for one‐, two‐ and three‐dimensional flow cases, with emphasis on problems involving saturation shocks, heterogeneous media and curved boundaries. For reservoirs consisting of multiple rock types with differing capillary pressure properties, it is shown that traditional Bubnov‐Galerkin methods give poor results and the new Petrov–Galerkin formulations are required. Investigations regarding the behaviour of several preconditioned conjugate‐gradient‐like methods in these type of problems are also reported.
Dynamic simulation of the hydrodynamic interaction among immersed particles in Stokes flow
Authors: Ingber Marc S. 
Published: August 2005

AbstractA numerical method for the dynamic simulation of the hydrodynamic interaction among particles in Stokes flow is developed. The method couples the quasi‐static Stokes equations for the fluid with the equilibrium equations for the particles. The boundary element method is used to represent the velocity at a general field point in terms of surface velocities and stresses. However, neither the stresses nor the velocities are assumed to be known on the surface of the particles. Kinematic equations relating the linear and angular velocities at the centroids of the particles to the surface velocities are combined with the discretized boundary element equations and the equilibrium equations to generate a system of linear equations. The associated coefficient matrix is correspondent to the grand resistance matrix which relates the velocities of the particles to a given geometry.
On the numerical solution of the turbulence energy equations for wave and tidal flows
Authors: Davies A. M. , Jones J. E. 
Published: August 2005

AbstractThis paper deals with the numerical solution, using finite difference methods, of the hydrodynamic and turbulence energy equations which describe wind wave and tidally induced flow.Calculations are performed using staggered and non‐staggered finite difference grids in the vertical, with various time discretizations of the production and dissipation terms in the turbulence energy equations. It is shown that the time discretization of these terms can significantly influence the stability of the solution. The effect of time filtering on the numerical stability of the solution is also considered. The form of the mixing length is shown to significantly influence the bed stress in wind wave problems.A no‐slip condition is applied at the sea bed, and the associated high‐shear bottom boundary layer is resolved by transforming the equations onto a logarithmic or log‐linear co‐ordinate system before applying the finite difference scheme.A computationally economic method is developed which remains stable even when a very fine vertical grid (over 200 points) is used with a time step of up to 30 min.
Using a segregated finite element scheme to solve the incompressible Navier‐Stokes equations
Authors: Shaw C. T. 
Published: August 2005

AbstractIn this paper, a segregated finite element scheme for the solution of the incompressible Navier‐Stokes equations is proposed which is simpler in form than previously reported formulations. A pressure correction equation is derived from the momentum and continuity equations, and equal‐order interpolation is used for both the velocity components and pressure. Algorithms such as this have been known to lead to checkerboard pressure oscillations; however, the pressure correction equation of this scheme should not produce these oscillations. The method is applied to several laminar flow situations, and details of the methods used to achieve converged solutions are given.
On the use of the reach‐back characteristics method for calculation of dispersion
Authors: Yang Jinn‐Chuang , Hsu Euan‐Lung 
Published: August 2005

AbstractThe Holly‐Preissmann two‐point finite difference scheme (HP method) has been popularly used for solving the advection equation. The key idea of this scheme is to solve the dependent variable (i.e. the concentration for the pollutant transport problem) by the method of characteristics with the use of cubic interpolation on the spatial axis. The interpolating polynomials of higher order are constructed by use of the dependent variable and its derivatives at two adjacent grid points. In this paper a new interpolating technique is introduced for incorporation with the Holly‐Preissmann two‐point method. The new method is denoted herein as the Holly‐Preissmann reach‐back method (HPRB) and allows the characteristics to project back several time steps beyond the present time level. Through stability analyses it has been observed that the increase of the reach‐back time step numbers for the characteristics indeed reduces the numerical damping and dispersive phenomena. A schematic model has been constructed to demonstrate the merits of this new technique for the calculation of the pure advection and dispersion equations. Numerical experiments and comparisons with analytical solutions which support and demonstrate this new technique are presented.
Vorticity‐streamfunction formulation of unsteady incompressible flow past a cylinder: Sensitivity of the computed flow field to the location of the outflow boundary
Authors: Behr M. , Liou J. , Shih R. , Tezduyar T. E. 
Published: August 2005

AbstractThe influence of the location of the outflow computational boundary on the unsteady incompressible flow past a circular cylinder at Reynolds number 100 is examined. The vorticity‐streamfunction formulation of the Navier‐Stokes equations is used in all computations. Two types of outflow boundary conditions are subjected to a series of tests in which the domain length is gradually reduced. The traction‐free condition performs well in most cases and allows the outflow boundary to be located as close as 6.5 cylinder diameters from the body. The other boundary condition type is not as forgiving, but has the advantage of being simpler to implement and can still provide reasonably accurate solutions. It is also observed that both condition types can influence the flow field strongly and globally when the boundary is brought closer than 2.5 diameters from the body. In such cases the temporal periodicity of the solution is lost.
A hybrid k‐ε turbulence model of recirculating flow
Authors: Chang K. C. , Chen C. S. , Uang C. I. 
Published: August 2005

AbstractThis investigation deals with the modification of streamline curvature effects in the k‐ε turbulence model for the case of recirculating flows. Based upon an idea that the modification of curvature effects in C2 should not be made in regions where the streamline curvature is small, a hybrid k‐ε model extended from the modification originally proposed by Srinivasan and Mongia is developed. A satisfactory agreement of model predictions with experimental data reveals that the hybrid k‐ε model can perform better simulation of recirculating turbulent flows.
A globally well‐posed finite element algorithm for aerodynamics applications
Authors: Iannelli G. S. , Baker A. J. 
Published: August 2005

AbstractA finite element CFD algorithm is developed for Euler and Navier‐Stokes aerodynamic applications. For the linear basis, the resultant approximation is at least second‐order‐accurate in time and space for synergistic use of three procedures: (1) a Taylor weak statement, which provides for derivation of companion conservation law systems with embedded dispersion‐error control mechanisms; (2) a stiffly stable second‐order‐accurate implicit Rosenbrock‐Runge‐Kutta temporal algorithm; and (3) a matrix tensor product factorization that permits efficient numerical linear algebra handling of the terminal large‐matrix statement. Thorough analyses are presented regarding well‐posed boundary conditions for inviscid and viscous flow specifications. Numerical solutions are generated and compared for critical evaluation of quasi‐one‐ and two‐dimensional Euler and Navier‐Stokes benchmark test problems. Of critical importance, essentially non‐oscillatory solutions are uniformly attained for a range of supercritical flow situations with shocks.