bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shedding patterns of the near‐wake vortices behind a circular cylinder
Authors: Sa Jong‐Youb , Chang Keun‐Shik 
Published: August 2005

AbstractThe unsteady incompressible Navier‐Stokes equations have been accurately solved for the laminar flow past a circular cylinder in the Reynolds number range 50–200. A direct elliptic solver called the SEVP is used to rapidly advance the streamfunction in time, facilitating the overall convergence to the fully periodic or quasi‐steady state. A new integral‐series method is developed for the far‐field streamfunction condition on a finite two‐dimensional computational domain. The use of fourth‐order Hermitian relations for the convection terms in the conservation‐form vorticity transport equation has also contributed to the good comparison of the present results with the earlier experimental data. The vortex‐shedding patterns visualized by the experimentalist are numerically reproduced here in the given Reynolds number range. Discussions that may be helpful in interpreting the behaviour of the shedding frequency are presented in the main text.
Stabilization of a time integrator for the 3D shallow water equations by smoothing techniques
Authors: de Goede E. D. 
Published: August 2005

AbstractA smoothing technique is applied to improve the stability of a semi‐implicit time integrator for the three‐dimensional shallow water equations. In this method the terms involving the vertical direction are treated implicitly. The stability condition on the time step depends only on the horizontal mesh sizes; therefore in the horizontal‐direction a smoothing operator is added. Owing to the smoothing, the maximally stable time step increases considerably while the accuracy is hardly affected. Moreover, it turns out that the smoothing operator is efficient on vector and parallel computers.
Calculation of laminar recirculating flows using a local non‐staggered grid refinement system
Authors: Coelho P. , Pereira J. C. F. , Carvalho M. G. 
Published: August 2005

AbstractA grid‐embedding technique for the solution of two‐dimensional incompressible flows governed by the Navier‐Stokes equations is presented. A finite volume method with collocated primitive variables is employed to ensure conservation at the interfaces of embedding grids as well as global conservation. The discretized equations are solved simultaneously for the whole domain, providing a strong coupling between regions of different refinement. The formulation presented herein is applicable to uniform or non‐uniform Cartesian meshes. The method was applied to the solution of two scalar transport equations, to cavity flows driven by body and shear forces and to a sudden plane contraction flow. The numerical predictions are compared with the exact solutions when available and with experimental data. The results show that neither the convergence rate nor the stability of the method is affected by the presence of embedded grids. Embedded grids provide a better distribution of grid nodes over the computational domain and consequently the solution accuracy was improved. The grid‐embedding technique proved also that significant savings in computing time could be achieved.
Euler analysis of transonic stator‐rotor interaction using a finite volume method
Authors: Kang In‐Mo , Chang Keun‐Shik 
Published: August 2005

AbstractA generalized finite volume method that can solve the Euler equations for the stator and rotor parts of stage flow in similar formulations is presented. The method consists of a new moving grid finite volume formulation applied to the rotor region and the existing fixed grid finite volume method used in the stator region, with the data transfer made by an interpolation procedure at the sliding surface in between. The accuracy of the method has been demonstrated on a simple cascade flow before the time‐dependent compressor stage flow is fully investigated. The transonic stator‐rotor flow interaction is elucidated within the inviscid and rotational flow limit.
A Helmholtz pressure equation method for the calculation of unsteady incompressibl eviscous flows
Authors: Williams Morgan 
Published: August 2005

AbstractA time‐implicit numerical method for solving unsteady incompressible viscous flow problems is introduced. The method is based on introducing intermediate compressibility into a projection scheme to obtain a Helmholtz equation for a pressure‐type variable. The intermediate compressibility increases the diagonal dominance of the discretized pressure equation so that the Helmholtz pressure equation is relatively easy to solve numerically. The Helmholtz pressure equation provides an iterative method for satisfying the continuity equation for time‐implicit Navier–Stokes algorithms. An iterative scheme is used to simultaneously satisfy, within a given tolerance, the velocity divergence‐free condition and momentum equations at each time step. Collocated primitive variables on a non‐staggered finite difference mesh are used. The method is applied to an unsteady Taylor problem and unsteady laminar flow past a circular cylinder.
Parallel algorithms for panel methods
Authors: David Tim , Blyth Graham 
Published: August 2005

AbstractA parallel algorithm for the solution of potential flow problems using the panel method of Hess and Smith and conjugate and bi‐conjugate gradient techniques is presented. Analysis of the parallelism for the matrix. solvers shows the algorithms to have scalable properties as the problem size grows indefinitely large. Speed‐up and efficiency values are presented along with experimental and theoretical values for the optimum number of processors for maximum speed‐up. It is envisaged that the parallel techniques presented here have applications using other boundary integral methods for solving engineering problems of a more complex nature.
Towards the numerical simulation of the horizontal slug front
Authors: Yacoub N. , Maron D. Moalem , Naot D. 
Published: August 2005

AbstractSteps towards the numerical simulation of the flow behind the slug front in horizontal slug flow performed with a streamfunction‐vorticity representation of the mean flow and an energy dissipation model for the turbulence are discussed. The flow field consists of two vortices, one saddle point and four stagnation regions. Attention is focused on the following boundary conditions: moving wall jet, moving wall, free jet velocity discontinuity and vertical liquid‐gas open surface. A dissipation flux boundary condition is suggested to simulate the interaction of the turbulent eddies with the open surface. A method to assess the necessity to use a transport model equation for the dissipation rather than a geometric specification of a length is suggested. Three different ways to characterize the mixing zone length are proposed.
Hot flow analysis of swirling sudden‐expansion dump combustor
Authors: Chuang Shu‐Hao , Lin Hsun‐Cheng , Tai Fang‐Mei , Sung Hong‐Ming 
Published: August 2005

AbstractHot flow of a sudden‐expansion dump combustor with swirling is analysed by employing an infinite chemical reaction rate. Turbulence properties are closed using one type of algebraic Reynolds stress model and two types of κ–ϵ model. One of the κ–ϵ models includes a swirling effect modification to the ε‐equation. Computations have been performed by the SIMPLE‐C algorithm with a power‐law scheme. The calculated results of the momentum fields and turbulence quantities for swirling flow are compared with the available experimental data. It is shown that the standard κ–ϵ model gives poor prediction of the mean velocity, particularly the tangential velocity. For the hot flow analysis of a sudden‐expansion dump combustor with swirling flow it is suggested that it is necessary to use the modified κ–ϵ model or algebraic Reynolds stress model.
Computation of axisymmetric confined jets in a diffuser
Authors: Zhu J. , Rodi W. 
Published: August 2005

AbstractThe paper reports on a numerical study of turbulent confined jets in a conical duct with a 5° divergence. The flow has a large ratio of jet to ambient velocities at the entrance so that it gives rise to strong recirculation. The calculations are carried out with a general finite volume method designed for calculating incompressible elliptic flows with complex boundaries. Turbulence is simulated by the standard κ–ϵ model. The sensitivity of the solution to numerical discretization errors is examined using three convection schemes, i.e. hybrid central/upwind differencing, QUICK and SOUCUP, on two grids consisting of 68 × 50 and 102 × 82 points respectively. An examination is also made of the influence of inlet boundary conditions on the predicted flow field. The computed results are compared with experimental data for mean axial velocity, turbulent shear stress and turbulent kinetic energy profiles. It is shown that the calculations reproduce the essential features of the flow observed in the experiments.
Simulation of supersonic and hypersonic flows
Authors: Milthorpe J. F. 
Published: August 2005

AbstractA simple convection algorithm for simulation of time‐dependent supersonic and hypersonic flows of a perfect but viscous gas is described. The algorithm is based on conservation and convection of mass, momentum and energy in a grid of rectangular cells. Examples are given for starting flow in a shock tube and oblique shocks generated by a wedge at Mach numbers up to 30·4. Good comparisons are achieved with well‐known perfect gas flows.
Transient finite element method for calculating steady state three‐dimensional free surfaces
Authors: Wambersie O. , Crochet M. J. 
Published: August 2005

AbstractIn order to reduce the cost of large three‐dimensional calculations of steady state free surfaces, we have combined a time‐dependent approach, a decoupling algorithm and a conjugate gradient solver along the lines introduced earlier by Gresho and Chan. The free surface is calculated separately by applying the kinematic condition to a number of faces defined on the undeformed surface. For the pseudo‐time‐marching technique we show that it is economical to adopt different time steps for the free surface calculation and the other fields. The accuracy of the method is tested on the well‐known circular die problem; the method is then used to reveal the effects of inertia and shear thinning on square and rectangular dies.
A least‐squares method for solving the mixed form of the groundwater flow equations
Authors: Bentley L. R. , Pinder G. F. 
Published: August 2005

AbstractThe mixed form of the areal groundwater flow equations is solved with a least‐squares finite element procedure (LESFEM). Hydraulic head and x‐ and y‐directed fluxes are state variables. Physical parameters and state variables are approximated using a bilinear basis. Grid refinements and irregular domain boundaries are implemented on rectangular meshes.Residuals are constructed at collocation points for conservation of mass and Darcy's law. Boundary condition residuals are constructed at discrete points along the boundary. The residuals are weighted, squared and summed. A set of algebraic equations is formed by taking the derivatives of the weighted sum of the squares of the residuals with respect to each unknown parameter in the approximation for the state variable and setting them to zero.Proper choice of a potential scaling parameter and residual weights is essential for the effective application of the algorithm. Test problem results demonstrate that the method is effective for both transient and steady state cases.The LESFEM algorithm generates a C°‐continuous velocity field. The continuous velocity field and the rectangular mesh simplify the implementation of algorithms that require tracking. In addition, rectangular meshes simplify mesh and boundary generation.
A least‐squares finite element method for incompressible Navier‐Stokes problems
Authors: Jiang Bo‐Nan 
Published: August 2005

AbstractA least‐squares finite element method based on the velocity–pressure–vorticity formulation was proposed for solving steady incompressible Navier‐Stokes problems. This method leads to a minimization problem rather than to the saddle point problem of the classic mixed method and can thus accommodate equal‐order interpolations. The method has no parameter to tune. The associated algebraic system is symmetric and positive definite. In order to show the validity of the method for high‐Reynolds‐number problems, this paper provides numerical results for cavity flow at Reynolds number up to 10 000 and backward‐facing step flow at Reynolds number up to 900.
The double von Mises transformation in the study of two‐phase fluid flow over curved boundaries: Theory and analysis
Authors: Barron R. M. , Hamdan M. H. 
Published: August 2005

AbstractA numerical method to handle the flow of a two‐phase fluid over curved boundaries is proposed. The method is based on the double von Mises transformation which is derived in this work and is expected to be applicable to a variety of flow situations while utilizing the finite difference technique. In order to illustrate the numerical implementation of the method, dusty fluid flow through a porous channel possessing curved boundaries and the flow through a semi‐infinite porous layer overlying a curved lower boundary are considered. The flow is assumed to be governed by model equations based on Brinkman's equation and reflecting boundary conditions are employed in the study based on a uniform dust particle distribution. Results indicate that an increase in the permeability results in decreasing the tangential velocity component in regions close to the curved boundary, and increasing the dust parameters decreases this component. The effects of the grid size and the extent of the computational domain are discussed. The results also shed some light on the applicability of the dusty fluid flow model and suggest that the model is best employed when the permeability is high, a conclusion that is consistent with the validity of Brinkman's equation.
A prediction of the pressure field in a plane turbulent jet using an algebraic stress model
Authors: Bergstrom Donald J. 
Published: August 2005

AbstractA numerical prediction is obtained for the mean pressure field in the similarity region of a plane turbulent jet. An algebraic stress model, which introduces non‐isotropic relations for the Reynolds stress components, is used to close the mean momentum equation. The full two‐dimensional form of the transport equations is retained and the resultant equation set solved elliptically. The numerical prediction simulates many of the characteristics of the pressure field measured by experimental studies. However, the overall level of the predicted field is lower than the experimental values. The level obtained for the mean pressure field depends strongly on the prediction for the transverse normal Reynolds stress component 〈u2u2〉. The pressure field is shown to represent a small negative contribution to the net strearnwise momentum balance.
Numerical simulation of fully non‐linear steady free surface flow
Authors: Lalli F. , Campana E. , Bulgarelli U. 
Published: August 2005

AbstractThe fully non‐linear free surface potential flow past a 2D non‐lifting body is computed. The numerical method is based on the simple layer integral formulation; the non‐linear solution is obtained by means of an iterative procedure. Under some hypotheses, viscosity effects at the free surface are considered. All the numerical results obtained have been tested against analytical solutions and experimental results.
Two‐dimensional wave run‐up analysis by selective lumping finite element method
Authors: Okamoto Takashi , Kawahara Mutsuto , Ioki Nobuhiro , Nagaoka Hiroaki 
Published: August 2005

AbstractA new finite element technique for the analysis of wave run‐up is presented in this paper. In this finite element approach, the movement of the shoreline is expressed by that of the nodal points at the wave front, and an auto mesh generation technique is effectively used. The present method is tested by the comparison with the experimental result of a channel with uniform slope, and two numerical examples are reported to show the efficiency of this method. As a final example, the tsunami run‐up caused by the 1983 Nihonkai‐Chubu earthquake is analysed and compared with actual records of the flooded area.
Conservative monotone streamline upwind formulation using simplex elements
Authors: Shemirani F. , Jambunathan K. 
Published: August 2005

AbstractA streamline upwind formulation is presented for the treatment of the advection terms in the general transport equation. The formulation is monotone and conservative and is based on the discontinuous nature of the advection mechanism. The results of there benchmark test cases for the full range of flow Peclet numbers are presented. The new formulation is shown to accurately model the advection phenomenon with significantly smaller numerical diffusion than the existing methods. The results are also free of all spatial oscillations. Considerable savings in computer storage and execution time have been achieved by employing the three‐noded triangular element for which exact integrations exist. The formulation is straightforward and can be readily incorporated into any finite element code using the conventional Galerkin approach.
Die design: An implicit formulation for the inverse problem
Authors: Legat Vincent , Marchal Jean‐Marie 
Published: August 2005

AbstractLet us call a direct extrusion problem (DEP) the problem of finding the shape of the extrudate coming out of a die of prescribed shape. An implicit finite element formulation of the DEP which is geometrically general and for which a Newton‐Raphson technique can be implemented has recently been proposed by Legat and Marchal. However, the problem posed to the die designer is frequently the inverse extrusion problem (IEP), i.e. finding the die shape which produces an extrudate of prescribed shape. This paper presents an extension of our original method for solving the IEP which avoids the ‘trial‐and‐error’ iteration on the die geometry itself.The advantage of the formulation lies in its capability to handle complex geometrics and in its low cost, because the CPU time and memory required to solve the IEP are almost identical to those of the DEP. We present benchmark results for squares and rectangles and new results obtained for geometries involving multiple corners. For an octagonal shape we also consider the case of a power‐law fluid.For all results presented in this paper, surface tension has not been included.
A probabilistic method for field solutions in two‐phase flows
Authors: Zhang J. , Roco M. C. 
Published: August 2005

AbstractSolid‐particle motion and related transport phenomena in two‐phase flow are fluctuating processes in space and time. A deterministic method can describe only partially the intrinsic physics of these processes. In this paper, the fluctuations of the flow parameters are modelled by considering the spatial correlations, and a probabilistic computational method for two‐phase flow is presented. The probabilistic governing equations have been discretized in space using a finite volume method, and then solved by applying the Neumann expansion method. This last method is time efficient, and its convergence can be guaranteed even for large fluctuations. A liquid‐solid particle mixture flow in a circular pipe is taken as an example. Computational results illustrate the merit of the probabilistic approach for the prediction of two‐phase flow phenomena.
An assessment of the finite termination property of the defect correction method
Authors: Shaw G. J. , Crumpton P. I. 
Published: August 2005

AbstractThis paper investigates the use of defect correction procedures for the solution of finite volume approximations to systems of conservation laws. Particular emphasis is laid on the order of accuracy obtained after a fixed finite number of iterations. It is shown that a high order of accuracy may be achieved after only one defect correction iteration, involving two inversions of a stable lower‐order‐accurate operator. However, this result is found to be critically dependent on the consistency of the lower‐order operator, a property which does not always hold for conservative finite volume discretizations. Through numerical experiments, the lack of consistency of these schemes is found to inhibit severely the finite termination property of the defect correction process. Results are presented for linear advection, Poisson's equation, and the Euler equations.
Computer simulation of moist atmospheric convection with finite elements
Authors: Mann Kenneth J. 
Published: August 2005

AbstractA computer simulation is made of cellular convection in a moist atmosphere in an endeavour to obtain a computer model which more closely approximates the observed modes of convection. A finite element Galerkin technique, with Taylor approximation and Crank‐Nicolson, is employed and comparisons are made with the author's earlier finite element models of convection in an absolutely unstable atmosphere and with finite difference models. It is found that the inclusion of the moisture effects alters the structure of a cell to that of a narrow ascending region and a wider descending region with the former of larger velocities than the latter, and also alters the preferred mode of convection by increasing the aspect ratio. This more closely resembles that which is observed in the atmosphere.
A remark on the projection‐3 method
Authors: Shen Jie 
Published: August 2005

AbstractWe show that the continuous (in time) form of the projection‐3 scheme proposed in Reference 2 is not a proper approximation of the unsteady Navier‐Stokes equations. Hence, the projection‐3 scheme and its variants are not appropriate for the numerical computation of the Navier‐Stokes equations.
Solution of the discretized incompressible Navier‐Stokes equations with the GMRES method
Authors: Vuik C. 
Published: August 2005

AbstractWe describe some experiences using interative solution methods of GMRES type to solve the discretized Navier‐Stokes equations. The discretization combined with a pressure correction scheme leads to two different systems of equations: the momentum equations and the pressure equation. It appears that a fast solution method for the pressure equation is obtained by applying the recently proposed GMRESR method, or GMRES combined with a MILU preconditioner. The diagonally scaled momentum equations are solved by GMRES(m), a restarted version of GMRES.
Numerical simulation of vortex shedding past triangular cylinders at high Reynolds number using a k‐ε turbulence model
Authors: Johansson Stefan H. , Davidson Lars , Olsson Erik 
Published: August 2005

AbstractCalculations of unsteady turbulent flow around and behind triangular‐shaped flameholders using a finite volume code with a k‐ε model of turbulence are presented.The flow behind the flameholders is found to be unsteady (a von Kármán vortex street appears) with a well defined Strouhal frequency (predicted Sr=0·27 compared with an experimental value of 0·25). The predicted profiles of velocity and fluctuating kinetic energy agree well with experiments. The periodic motions in the vortex street are shown to be far more important than the turbulent stochastic motions in exchanging momentum in the transversal direction.The pressure‐velocity coupling is handled with the SIMPLEC pressure correction procedure. The discretization in time is fully implicit and 90 times steps are used to resolve one time cycle. It was found that to capture the vortex street it is very important that the grid spacing is sufficiently fine (180 × 100).
Three‐dimensional vortex method for parachutes
Authors: Humi Mayer 
Published: August 2005

AbstractWe describe the implementation of a new 3D vortex algorithm for the computation of the drag and flow field around parachutes. Among its novel features, the algorithm couples large eddy simulation methodology with the vortex method, away from the wall region. Furthermore, boundary conditions for a wall (no‐slip) and compliant boundaries were implemented. The results of several simulations using this algorithm are analysed and discussed. The spectral contents of the vortex method are also considered.