摘要:

The finite-difference methods of Lax, Lax-Wendroff (two-step), and the donor celt type, and the finite-element method using a Galerkin procedure with B-splines as approximating functions are compared with the method of characteristics for the solution of waterhammer transients as typified by valve closure problems. From the point of view of accuracy, the two-step Lax-Wendroff method and the method of characteristics are comparable and produce the best results. The Lax method fares worst. The donor cell type and the Galerkin procedure with quadratic B-sptine basis as approximating functions display roughly the same accuracy. From the comparison presented, it appears that Galerkin technique offers no substantial advantage over the other finite-difference methods except that of ease in handling boundary conditions as compared with finite-difference methods.

ISSN:0149-5720    

DOI:10.1080/10407787908913397

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A numerical method is presented for calculating the symmetric wakes of two-dimensional bodies for incompressible laminar and turbulent flows. The appropriate thin shear layer equations are solved by using Keller's two-point finite-difference method. To account for the inner shear layer generated by the change of boundary conditions from no slip on the body to smooth flow on the axis of symmetry, a double-structured numerical scheme is used at the trailing edge. The Reynolds shear stress term is modeled by a modified version of the algebraic eddy viscosity approach of Cebeci and Smith. A comparison of centerline velocities for laminar wake flows with zero pressure gradient indicates excellent agreement with those given by Goldstein. In addition, several laminar temperature profiles past a flat plate are computed for several Prandtl numbers. Similar calculations for turbulent wake flows also indicate excellent agreement with the experimental data of Chevray and Kovasznay and show that the centerline velocities as well as the velocity profiles across the layer can be computed satisfactorily with the present method. Finally, a set of wake calculations is presented for flows with pressure gradient.

ISSN:0149-5720    

DOI:10.1080/10407787908913398

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

The equations of transient heat conduction are developed for a generalized curvilinear coordinate system in Euclidean space. The equation is then specialized for the case of two-dimensional heat flow. The equations are applicable not only to planar problems but also to problems for thin surfaces. A compact finite-difference formulation for surface heat flow is given that permits variable mesh spacing, variable thickness, properties that vary spatially and with temperature, nonlinear boundary conditions, and volumetric heat generation. Example problems in nonorthogonal planar coordinates are given along with a problem for a thin curved surface.

ISSN:0149-5720    

DOI:10.1080/10407787908913399

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

A simple finite-element algorithm is derived for the solution of the one-dimensional advection-diffuaon transport equation. Local interpolation functional are obtained for each subdomain, or element, by using linear basis functions. The integral form of the finite-element algorithm is evaluated by using hypermatrices and a natural coordinate system. Assemblage over two adjacent elements gives the tridiagonal recursion relation for chapeau functions. By time-splitting either a two-or a three-dimensional equation into a series of one-dimensional equations and by using the basic one-dimensional finite-element algorithm, multidimensional problems can be solved with little additional programming complexity or storage.

ISSN:0149-5720    

DOI:10.1080/10407787908913400

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Use of the finite-element method (FEM) for the computation of transient thermal problems can lead to the anomalous result that, even in the absence of local sources of heat, temperatures near suddenly cooled boundaries show an initial increase. A spectral analysis of the FEM and finite-difference method (FDM) reveals that this anomaly is caused by overestimation of the eigenvalues. The FDM, since it represents a lower bound to these eigenvalues, does not exhibit this behavior.

ISSN:0149-5720    

DOI:10.1080/10407787908913401

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Calculations of velocity and temperature distributions in rooms with ventilation arrangements are reported. The method involves the solution, in finite-difference form, of two-dimensional equations for the conservation of mass, momentum, energy, turbulence energy, and dissipation rate, with algebraic expressions for the turbulent viscosity and heat diffusivity. The results are shown to be in reasonable agreement with available experimental data and the method is then applied to provide additional information useful for design purposes.

ISSN:0149-5720    

DOI:10.1080/10407787908913402

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor

摘要:

Numerical solutions have been carried out to determine the temperature distribution along the exposed surface of a convectively cooled wall whose rear side is heated by a periodic array of groove-embedded heating elements. The accuracy of the numerical procedure was verified by using it to solve a related problem in which the heating occurs at discrete surface patches and then comparing those results with an exact solution. The numerical results for the exposed-surface temperature distributions corresponding to groove and patch heating were compared, and remarkably close agreement was found to prevail. This finding suggests that the computationally convenient exact solution for patch heating can be employed to obtain results for groove heating. The parameters which affect the uniformity of the temperature distribution on the convectively active surface were identified, and their quantitative influence was explored.

ISSN:0149-5720    

DOI:10.1080/10407787908913403

出版商:Taylor & Francis Group    

年代:1979

数据来源: Taylor