摘要:

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 mult

ISSN:0271-2091    

DOI:10.1002/fld.1650100502

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA spectral code has been used to simulate a developing turbulent boundary layer at low Reynolds numberReθ(based on free stream velocity and momentum thickness) between 353 and 576. The starting field was generated by allowing a step change of temperature to diffuse outwards from one wall in a fully developed channel flow. The thermal boundary layer so created was conditionally sampled to convert it into a momentum boundary layer with an irrotational free stream region, a process which is justified by appeal to experiments. This initial field was allowed to develop until the momentum boundary layer thickness δ995had grown to about 1·5 times its original thickness.The results of the simulation have been compared with a wide range of experimental data. The outcome of this comparison is generally very satisfactory; the main trends of the experiments are well reproduced and our simulation supplements and extends the existing sets of experimental data. The simulation also gives pressure statistics which cannot be obtained experimentally. In particular, it gives the contribution of pressure diffusion to the balance equations for the Reynolds stress and indicates the error produced by omitting this te

ISSN:0271-2091    

DOI:10.1002/fld.1650100503

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA method based on backward finite differencing in time and a least‐squares finite element scheme for first‐order systems of partial differential equations in space is applied to the Euler equations for gas dynamics. The scheme minimizes theL2‐norm of the residual within each time step. The method naturally generates numerical dissipation proportional to the time step size. An implicit method employing linear elements has been implemented and proves robust. For high‐order elements, computed solutions based on theL2‐method may have oscillations for calculations at similar time step sizes. To overcome this difficulty, a scheme which minimizes the weightedH1‐norm of the residual is proposed and leads to a successful scheme with high‐degree elements. Finally, a conservative least‐squares finite element method is also developed. Numerical results for two‐dimensional problems are given to demonstrate the shock resolution of the methods and compare dif

ISSN:0271-2091    

DOI:10.1002/fld.1650100504

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

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 orderd/D, the duct‐to‐coil diameter ratio. The effect of these terms is investigated by considering the flow in a 90° bend for larged/D. It is shown that while there may be significant error in the prediction of the local variables for larged/D, the circumference‐averaged quantities are well

ISSN:0271-2091    

DOI:10.1002/fld.1650100505

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

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 efficien

ISSN:0271-2091    

DOI:10.1002/fld.1650100506

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650100507

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650100501

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY