摘要:

AbstractA new boundary element procedure is developed for the solution of the streamfunction–vorticity formulation of the Navier–Stokes equations in two dimensions. The differential equations are stated in their transient version and then discretized via finite differences with respect to time. In this discretization, the non‐linear inertial terms are evaluated in a previous time step, thus making the scheme explicit with respect to them. In the resulting discretized equations, fundamental solutions that take into account the coupling between the equations are developed by treating the non‐linear terms as in homogeneities. The resulting boundary integral equations are solved by the regular boundary element method, in which the singular points are placed outside the solution

ISSN:0271-2091    

DOI:10.1002/fld.1650100102

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA theory is presented for unsteady two‐dimensional potential transonic flow in cascades of compressor and turbine blades using a mesh of triangular finite elements. The theory leads to a computer program, FINSUP, which is fast and has moderate storage requirements, so that it can be run on a personal computer. Comparisons with other theories in special cases show that the program is accurate in subsonic flow, and that in supersonic flow, although the wave effects are smeared by the numerical process, the results for overall blade force and moment have acceptable accuracy. The program is useful for engineering assessment of unstalled flutter of actual compressor and turbine blade

ISSN:0271-2091    

DOI:10.1002/fld.1650100103

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe nodal integral method is a relatively new numerical technique that has been used recently to solve both static and dynamic multidimensional problems in heat transfer, fluid flow and neutron transport. The method offers significant advantages in terms of stability, accuracy and efficiency over conventional finite elements when the problem can be adequately modelled in Cartesian co‐ordinates. This method was used to investigate bifurcation phenomena in the Bénard problem for aspect ratios in the range of one to nine. Automatic search techniques were used with a static version to find the first four critical Rayleigh values for a square cavity, to map the first two critical Rayleigh values as a function of aspect ratio, and to examine the solution types. Accuracy enhancement was obtained by factorization and extrapolation. Critical values, obtained by interpolation, were verified dynamically. Aspect ratio crossover and transition values were found for the first two critical Rayleigh numbers, with an accuracy of the order of ±3 per cent. The precision achieved in the results forRa* andRa** as a function of β is usually within 0.1%–0.2% except at high β (i.e. near β=9.0) and at large critical values ofRa(i.e. the first few values ofRa** near β=1). Specific results at β=1.0 areRa*=2584±0.5,Ra**=6807,Ra3* = 19 734 and

ISSN:0271-2091    

DOI:10.1002/fld.1650100104

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe performance of the Galerkin finite element method when applied to time‐dependent convection involving rotation, self‐gravitation and the normal gravity field in a horizontal cylinder is discussed in this paper. The governing equations, the parameters of the problem and our implementation of the numerical schemes are presented. The accuracy, spatial scale of resolution, flexibility and robustness of the resulting code show the element method as a valuable tool for research in this area or in related problems in astrophysical fluid dynamics. The numerical difficulties in large‐amplitude flows are associated with an error‐control scheme for time integration and the ‘short‐time’ wiggles in transient Dirichlet problems. Coarse grids give the correct qualitative picture in most simulations, but the type of solution at short time (and hence grid refinement) presumably resolves the degeneracy in the azimuthal orientation of convection cells in flows driven by self‐gravitation and (perhaps) centrifugal buoyancy. The final state in transient flows is a motionless isothermal fluid. However, residual motions can be nullified only in the limit of zero grid size in flows driven by centrifugal buoyancy (self‐gravitation), while a fairly coarse grid is sufficient for this purpose in normal gra

ISSN:0271-2091    

DOI:10.1002/fld.1650100105

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractBuoyancy‐driven instability of a monocomponent or binary fluid which is completely contained in a vertical circular cylinder is investigated, including the influence of the Soret effect for the binary mixture. The Boussinesq approximation is used, and the resulting linear stability problem is solved using Galerkin's technique. The analysis considers various types of fluid mixtures, ranging from gases to liquid metals, in cylinders with a variety of radius‐to‐height ratios. The flow structure is found to depend strongly on both the cylinder aspect ratio and the magnitude of the Soret effect. Comparisons are made with experiments and other theories, and the predicted stability limits are shown to agree closely with observa

ISSN:0271-2091    

DOI:10.1002/fld.1650100106

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650100107

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650100108

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0271-2091    

DOI:10.1002/fld.1650100109

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY