摘要:

AbstractA perturbation solution of the fully developed flow through a pipe of circular cross‐section, which rotates uniformly around an axis oriented perpendicularly to its own, is considered. The perturbation parameter is given byR= 2Ωa2/ν in terms of the angular velocity Ω, the pipe radiusaand the kinematic viscosity ν of the fluid. The two coupled non‐linear equations for the axial velocity ω and the streamfunction ϕ of the transverse (secondary) flow lead to an infinite system of linear equations. This system allows first the computation of a given order ϕn,nϕ 1, of the perturbation expansion ϕ = ∑ n= 1∞Rnϕnin terms of ωn‐1, the (n‐1)‐th order of the expansion ω = ∑ n= 0∞Rnωn, and of the lower orders ϕ1,…,ϕn− 1. Then it permits the computation of ωnfrom ω0,…,ωn− 1and ϕ1,…,ϕ;n. The computation starts from the Hagen–Poiseuille flow ω0, i.e. the perturbation is around this flow.The computations are performed analytically by computer, with the REDUCE and MAPLE systems. The essential elements for this are the appropriate co‐ordinates: in the complex co‐ordinates chosen the two‐dimensional harmonic (Laplace, Δ) and biharmonic (Δ2) operators are ideally suited for (symbolic) quadratures. Symmetry considerations as well as analysis of the equations for ωn, ϕnand of the boundary conditions lead to general (polynomial) formulae for these functions, with coeffcients to be determined. Their determination, order by order, implies, in complex co‐ordinates, only (symbolic) differentiation and quadratures. The coefficients themselves are polynomials in the Reynolds numbercof the (unperturbed) Hagen–Poiseuille flow. They are tab

ISSN:0271-2091    

DOI:10.1002/fld.1650110302

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn the application of the finite element method to diffusion and convection‐dispersion equations over a ground‐water domain, the Galerkin technique was used to incorporate Neumann (or second‐type) and Cauchy (or third‐type) boundary conditions. While mass movement through open boundaries isa prioriunknown, these boundaries are usually treated as a zero Neumann condition at some far distance from the domain of interest. Nevertheless, cheaper and better solutions can be obtained if these unknown conditions are adequately incorporated in the weak formulation and in the transient solution schemes (open boundary condition). Theoretical and numerical proofs are given of the equivalences between this approach and a ‘well‐posed’ problem in a semi‐infinite domain with a zero Neumann condition at a boundary placed at infinity. Transport and diffusion equations were applied in one dimension to show the numerical performances and limitations of this procedure for some linear and non‐linear problems. Noa priorilimitations are foreseen in order to find similar solutions in two or three dimensions. Thus the spatial discretization in the proximity of open boundaries could be drastically reduced to the d

ISSN:0271-2091    

DOI:10.1002/fld.1650110303

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe diffusion flame of an afterburner as a function of the air‐fuel ratio is analysed by employing the SIMPLE‐C algorithm and the turbulence κ‐κ model. In the present analysis, better combustion efficiency of an afterburner with a slightly fuel‐lean mixture is shown. The velocity, fuel mass fraction, temperature and combustion efficiency distributions of reacting flow in an afterburner with two V‐gutter flameholders as a function of the air–fuel ratio are also discussed and compared. The calculated results in the present analysis can be applied to the fundamental study of reacting flow in a

ISSN:0271-2091    

DOI:10.1002/fld.1650110304

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractInteractive vortex shedding in the multiply connected domain formed by a pair of circular cylinders is analysed by the FEM–FDM blending technique. The vorticity–streamfunction formulation is used to solve the incompressible Navier–Stokes equations atRe= 100, with the time‐dependent wall streamfunctions determined from the pressure constraint condition and the far‐field streamfunctions from the integral series formula developed earlier by the authors. The standard Galerkin finite element method is used in the relatively small FEM subdomain and the finite difference method based on the general co‐ordinate system in the rest of the flow domain. Symmetric, antisymmetric and asymmetric wake patterns are obtained confirming the earlier experimental findings. The bistable nature of the asymmetric vortex shedding as well as the intermittent drifting from one status to the other between symmetric and antisymmetric wake patterns a

ISSN:0271-2091    

DOI:10.1002/fld.1650110305

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe finite element method is used to analyse convective heat transfer in a porous medium. Convection past a vertical surface embedded in the medium and convection in a confined porous medium enclosure are analysed using the above method. The results are compared with those available in the literature and the agreement is found to be good. The method is applicable for two‐dimensional analysis in a porous body of any arbitrary shape. The restriction of the boundary layer assumption is relaxe

ISSN:0271-2091    

DOI:10.1002/fld.1650110306

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractBy supplementing the pressure space for Taylor–Hood elements, elements that satisfy continuity locally are produced. These elements are shown to satisfy the Babuska–Brezzi compatibility condition by using the patch argument.Two examples are presented, one illustrating the convergence rates and the other illustrating a difficulty with a Taylor–Hood element that is overcome by the element presented

ISSN:0271-2091    

DOI:10.1002/fld.1650110307

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650110308

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650110309

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650110301

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY