摘要:

AbstractThe bifurcation phenomenon whereby multiple‐vortex secondary flow occurs in place of the normal two‐vortex flow in laminar flow in curved ducts has previously been studied numerically by several researchers. However, the various results have been conflicting on many points. The present paper describes a set of numerical experiments conducted to study the effect of numerical accuracy on the solution. The results show that the transition from two‐ to four‐vortex structure depends strongly on the differencing scheme and to a lesser extent on the grid size. The study also shows that as the Reynolds number of the flow increases, a two‐vortex structure is re‐established via a path which involves strongly asymmetric secondary flow patterns. These results are in agreement, at least qualitatively, with recent experimental theoretical and numeri

ISSN:0271-2091    

DOI:10.1002/fld.1650140302

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

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 f

ISSN:0271-2091    

DOI:10.1002/fld.1650140303

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractWe study the behaviour of a conjugate gradient Uzawa‐type method for a stabilized finite element approximation of the Stokes problem. Many variants of the Uzawa algorithm have been described for different finite elements satisfying the well‐known Inf‐Sup condition of Babuška and Brezzi, but it is surprising that developments for unstable ‘low‐order’ discretizations with stabilization procedures are still missing. Our paper is presented in this context for the popular (so‐called) Q1–P0 element.First we show that a simple stabilization technique for this element permits us to retain the property of a convergence factor bounded independently of the discretization mesh size. The second contribution of this work deals with the construction of a less costly preconditioner taking full advantages of the block diagonal structure of the stabilization matrix. Its efficiency is supported by 2D and. 3D n

ISSN:0271-2091    

DOI:10.1002/fld.1650140304

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA theoretical analysis is presented to solve numerically the steady state Navier–Stokes equations, continuity equation and energy equation for a compressible ideal gas flow between two closely spaced, in general nonparallel, infinitely wide plates (siider bearing). The analysis includes the gas inertia effect and covers both non‐choked and choked flows. The results of the present analysis compare very well with both analytical and experimental results of compressible flow in a slider bearing comprised of two parallel and stationary plates. It was found that for choked flow the gas inertia effect is important, while the consideration of the energy equation does not affect the accuracy of the calculated flow substantially. Finally, the stiffness of a slider bearing is presented for different geometrical characteristics of the bear

ISSN:0271-2091    

DOI:10.1002/fld.1650140305

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractIt is common knowledge that flow around bluff bodies exhibits oscillatory behaviour. The aim of the present study is to compute the steady two‐dimensional flow around a square cylinder at different Reynolds numbers and to determine the onset of unsteadiness through a linear stability analysis of the steady flow. Stability of the steady flow to small two‐dimensional perturbations is analysed by computing the evolution of these perturbations. An analysis of various time‐stepping techniques is carried out to select the most appropriate technique for predicting the growth of the perturbations and hence the stability of the flow. The critical Reynolds number is determined from the growth rate of the perturbations. Computations are then made for periodic unsteady flow at a Reynolds number above the critical value. The predicted Strouhal number agrees well with experimental data. Heat transfer from the cylinder is also studied for the unsteady laminar

ISSN:0271-2091    

DOI:10.1002/fld.1650140306

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

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 rectang

ISSN:0271-2091    

DOI:10.1002/fld.1650140307

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

摘要:

AbstractA new method combining the Preissmann four‐point scheme and the Holly–Preissmann reach‐back scheme is introduced to solve the rapidly varied flow problem in an open channel. The Preissmann four‐point scheme is well known for the computation of one‐dimensional unsteady flow. The Holly–Preissmann reach‐back scheme integrates the Holly‐Preissmann two‐point scheme with the concept of reach‐back characteristics, which allows the characteristics to project several time steps beyond the current time level. A spontaneous surge formation case is used to demonstrate and evaluate the applicability of the new method. It has been found that the results from this method are quite compatible with those of Preissmann four‐point scheme. In addition, with the appropriate choice of the number of reach‐back time steps, this new method can always avoid the numerical oscillation which usually exists when one uses the Preissmann four‐point scheme for the condition of Courant

ISSN:0271-2091    

DOI:10.1002/fld.1650140308

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650140309

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650140301

出版商:John Wiley&Sons, Ltd    

年代:1992

数据来源: WILEY