摘要:

A computational technique is presented for designing a filter to improve the computational efficiency of a numerical scheme. For an explicit scheme, the integration time step is increased, causing several waves to become unstable. These waves are filtered without disturbing the accuracy of the solution and the accuracy of the remaining waves are controlled. The scheme is applied to the solution of the Euler equations by using the NPARC code.

ISSN:1061-8562    

DOI:10.1080/10618560008940899

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A realizable, objective second-moment turbulence closure, allowing for an entropy characterisation, is analyzed with respect to its convective subset. The distinct characteristic wave system of these equations in non-conservation form is exposed. An approximate solution to Ihe associated one-dimensional Riemann problem is constructed making use of approximate jump conditions obtained by assuming a linear path across shock waves. A numerical integration method based on a new approximate Riemann solver (flux-difference-splitting) is proposed for use in conjunction with either unstructured or structured grids. Test calculations of quasi one-dimensional flow cases demonstrate the feasibility of the current technique even where Euler-based approaches fail.

ISSN:1061-8562    

DOI:10.1080/10618560008940900

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This paper proposes a general algebraic formulation able lo unify all the previous developments in (he frame of subgrid-scale modeling using dynamic mixed models. This formulation can serve as a guide for the design of new multi-parameter SGS models. All usual cases of coupling between momentum and energy (or transport) equation are treated formally, and properties of the associated linear or non-linear system are discussed. It is shown thai all the existing models found in the literature can be grouped into a seven-parameter dynamic model, referred to as the Maximal Complexity Dynamic Model (MCDM) A priori lests on this MCDM are carried out for the subsonic plane channel flow problem, which aim at selecting the most important contributions in multi-parameter dynamic models.

ISSN:1061-8562    

DOI:10.1080/10618560008940901

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The effect of reducing the formal order of accuracy of a finite-difference scheme in order to optimize its high-wavenumber performance, is investigated using the 1-D nonlinear unsteady inviscid Burgers' equation. Both explicit and compact schemes are compared to schemes wilh various levels of optimization. Results are given for the absolute and L2 errors as a function of time. It is found that the benefits of optimization do carry over into nonlinear applications.

ISSN:1061-8562    

DOI:10.1080/10618560008940902

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

This study investigates secondary instabilities of periodic wakes of a circular cylinder with infinitely long span. It has been known that after the wake undergoes a supercritical Hopf bifurcation (the primary instability) that leads to two-dimensional von Kantian vorlex street, the secondary instability occurs sequentially, which results in the onset of three-dimensional flow. Williamson (1996) has reviewed that the periodic wakes over a range of moderate Reynolds number from 140 to 300 are characterized by two critical modes. Mode A and Mode B, which are respectively associated with large-scale and fine-scale structures in span. In order to understand a sequence of bifurcation in transitional wake, in this paper, the stability of periodic Row governed by the linearized Navier-Stokes equations is analyzed by using the Floquet stability theory. By employing the finite elemental discretization with a fine mesh, the numerical results for both simulation and stability analysis have high spatio-resolution. The obtained stability results are in good agreement with experimental data and some relevant numerical results. By means of visualizations of the three-dimensionally critical flow structures. the existence of Mode A and Mode B is verified from the spatial structures in both the two modes.

ISSN:1061-8562    

DOI:10.1080/10618560008940903

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor