摘要:

A novel computational procedure for the prediction of incompressible fluid flow using primitive variables is presented. The formulation retains the geometric flexibility of the finite-element method and derives the governing discrete algebraic equations by using a conservation balance applied to discrete control volumes distributed throughout the domain. A novel method of closure, to relate the control volume surface values to the nodal point values, is introduced whereby a local discrete analog to the governing differential equation is formed at the control volume Surfaces. From this discrete equation analog the control surface values are determined in terms of the nodal values that represent the discrete problem unknowns. The manner in which this discrete equation is formed, solved, and used permits resolution of two longstanding problems in computational fluid dynamics, namely accurate convection modeling and preclusion of pressure field decoupling. A new and general boundary condition specification in terms of normal and tangential entities is also introduced.

ISSN:0149-5720    

DOI:10.1080/10407788708913560

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A novel control-volume finite-element method for heat transfer and fluid flow, in which all variables are colocated, is demonstrated and validated by application to a variety of test problems. The test problems are the convective scalar transport of a step profile at various angles to the grid and the fluid flow prediction for the driven cavity problem with Reynolds numbers of 100, 400, and 1000, for inviscid flow across a forward-facing step, and for rigid-body rotation discretized on a rectangular mesh with Reynolds numbers of 28.3 and infinity. The performance of the method is found to be excellent in terms of accuracy, providing excellent agreement with exact and grid-independent results, using only modest mesh discretization. The performance of the rigid-body rotation problem indicates that the scheme is “almost” second-order accurate.

ISSN:0149-5720    

DOI:10.1080/10407788708913561

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The upwind ( donor-cell) methodology has been explored in the framework of control volume-based finite-element methods using triangular elements. The key advantage of the upwind procedure is that it ensures positive discretization coefficients and hence a stable numerical analog that avoids any undershoots/overshoots. However, the upwind procedure does increase the cross-wind diffusion. Four test problems are solved to study the performance of the scheme.

ISSN:0149-5720    

DOI:10.1080/10407788708913562

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A multiple-step pressure correction algorithm, similar in spirit to the PISO algorithm, has been developed for the calculation of viscous flows in nonorthogonal curvilinear coordinates. The resulting pressure correction equations arc solved using a multigrid correction scheme. These developments were pursued because the pressure correction equation is the most time-consuming part of a Navier-Stokes flow calculation and because of the effect of the coupling between the pressure and velocity variables on the convergence rate. The new algorithm does improve the convergence rate for laminar flows or flows calculated on nearly orthogonal meshes. However, for turbulent or reacting flows, or flows computed on highly nonorthogonal meshes, there is little or no improvement in the convergence rate, and the CPU time is generally higher than for a single-step algorithm. A suitable balance between updating the velocity and static pressure variables is important, since a tightly converged pressure field can exaggerate the changes in the velocity field and cause the overall convergence rate to worsen. Although the multigrid scheme does a much better job of solving the pressure correction equation to high accuracy than a single-grid method, this limits the improvement of the overall algorithm that is possible. These results indicate that a multiple-step pressure correction algorithm does not have a decisive advantage over a single-step algorithm for many practical flows.

ISSN:0149-5720    

DOI:10.1080/10407788708913563

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A new transfinite element methodology for nonlinear transient thermal analysis is described. The proposed methodology is a hybrid approach that combines the major advantages of finite-element techniques, classical Bubnov-Galerkin schemes, and transform methods. Fundamental concepts of the methodology, including recent developments for application to nonlinear thermal problems, are described in technical detail. The applicability of the hybrid transfinite element approach to nonlinear transient thermal problems is quite novel. Comparative results of several test problems validate the basic capabilities of the proposed formulations. The hybrid transfinite element approach proposed here provides a computational methodology for nonlinear transient thermal analysis and has the potential for further extension.

ISSN:0149-5720    

DOI:10.1080/10407788708913564

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The thermal development of a hydrodynamically developed turbulent flow in an isothermal-wailed circular tube has been investigated in complementary numerical and experimental studies. The numerical work was based on an algebraic turbulence model used in conjunction with the appropriate conservation laws. In the experiments the naphthalene sublimation technique was used to enable precise modeling of the boundary conditions. Comparisons of numerically and experimentally determined quasi-local Sherwood numbers were made throughout the entire thermal entrance region and into the fully developed region for Reynolds numbers between 5400 and S3,500. The typical agreement between the numerical and experimental results was about three percent, with a maximum deviation of six percent. The predictions of the STAN5 computer code were found to be less accurate than those of the present numerical approach, as were the results predicted by a Graetz-type series solution.

ISSN:0149-5720    

DOI:10.1080/10407788708913565

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

An analysis of the heat transfer during arc welding has been carried out. The study is applicable to pure metals or alloys and to low or high boiling temperature materials and includes the effects of conduction, radiation, evaporation, boiling, and variable properties. Two evaporation models were studied and the results were compared with experimental data for stainless steel. The penetration depth was also calculated for lead, a low boiling temperature material, and the results were compared with previous calculations and with experimental data.

ISSN:0149-5720    

DOI:10.1080/10407788708913566

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0149-5720    

DOI:10.1080/10407788708913567

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0149-5720    

DOI:10.1080/10407788708913568

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

White the number of techniques for numerically approximating steady-state heat transfer problems continues to grow ( e.g., domain methods and variants such us finite differences and finite elements, boundary integral methods, and collocation methods), there still is a need for a procedure that develops exact solutions to simplified domain configurations to provide a family of test problems for use in evaluating the merits of a particular technique. In this paper an analytic solution to a family of mixed boundary value problems of the two-dimensional Laplace equation over the unit square is developed. Associated with this family of solutions is an error bound based on a lemma by Hopf. The mathematical development enables the numerical analyst to test the accuracy of other numerical techniques and evaluate the merits of a particular new development or variant of the base method.

ISSN:0149-5720    

DOI:10.1080/10407788708913569

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor