摘要:

The finite-element equations for coupled nonlinear heat conduction with phase change and steady current flow in the case where the electric field moves with constant speed are derived. The resulting matrix equations for quasi-static problems are nonsymmetric for the heat conduction part and symmetric for the electric field. The formulation is applied to several classical problems in heat conduction and compared to the more usual transient analysis formulation. It is shown that the quasi-static formulation is many times faster than the equivalent transient analysis. The formulation is then applied to a coupled problem in which the thermal and electrical properties are temperature dependent.

ISSN:0149-5720    

DOI:10.1080/10407788608913527

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The one-dimensional nonlinear inverse heat conduction problem is considered. A new technique for estimating the surface variances of the predicted surface fluxes and temperatures based on an adjoint formulation is presented. The surface variances are related to the measurement variances and to an estimate of the initial condition variances. The only assumption necessary to apply the technique is that of additive measurement errors. Two test cases with three sets of boundary conditions are studied. The surface variance estimates given by the adjoint formulation and direct estimation are shown to be in good agreement.

ISSN:0149-5720    

DOI:10.1080/10407788608913528

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

To improve the numerical stability of nonlinear equation solvers, a partitioned multiply scaled constraint scheme is developed. This scheme enables hierarchical levels of control for nonlinear equation solvers. To complement the procedure, partitioned convergence checks are established along with self-adaptive partitioning schemes. Overall, such procedures greatly enhance the numerical stability of the original solvers. To demonstrate and motivate the development of the scheme, the problem of nonlinear heat conduction is considered. In this context the main emphasis is given to successive substitution-type schemes. To verify the improved numerical characteristics associated with partitioned multiply scaled solvers, results are presented for several benchmark examples.

ISSN:0149-5720    

DOI:10.1080/10407788608913529

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This is a study of the flow driven by the buoyancy effect associated with the non-uniform volumetric absorption of a spatially uniform flux of thermal radiation that impinges on a body of fluid. The nonuniform absorption of radiation is due to the presence of regions of relative turbidity (coloring, suspension of particulates, algae) that alter the optical properties of the fluid. Focusing on the earliest stages of buoyancy-driven flow in the immediate vicinity of a relatively absorptive region, this study shows that the flow acquires a double-counterflow structure and that its effect is to rearrange the fluid so that increasingly warmer layers are positioned closer to the free surface. Analytically, the phenomenon is investigated on the basis of scale analysis and an asymptotic solution that is valid for vanishingly small times or Grashof numbers. Numerical experiments performed in a shallow two-dimensional layer confirm the flow structure and scaling trends anticipated theoretically.

ISSN:0149-5720    

DOI:10.1080/10407788608913530

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The effects of lateral surface mass transfer on the natural convection boundary layer about a vertical plate fin with solution-determined thermal boundary conditions (or fin temperature distributions) in a fluid-saturated porous medium were studied numerically. It was found that the governing parameters far the problem are the convection-conduction parameter Nccand the lateral mass flux parameter fw. The non-similar solutions were obtained by the local nonsimilarity method and were carried out up to the third level of truncation. The effects of mass flux on fin temperature distribution, boundary-layer thickness, local heat transfer coefficient, local heat flux, and total heat transfer rate are presented and discussed.

ISSN:0149-5720    

DOI:10.1080/10407788608913531

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A numerical study has been made of natural convection in a square partitioned enclosure with two offset baffles and perfectly conducting horizontal end walls. The study is made for three different baffle locations and two different conductivities at Rayleigh numbers of 104, 105, and 3.55 × 105. The results clearly demonstrate that baffle position has a significant effect on the heat transfer. As the top baffle is moved toward the cold wall and the bottom baffle toward the hot wall the average Nusselt number value decreases, as does the tendency of the flow to separate behind the baffles. At high Rayleigh numbers the tendency for separation increases and the average Nusselt number value decreases with increasing baffle conductivity. The influence of baffle conductivity on the local Nusselt number distribution increases as the top baffle is moved toward the cold wall and the bottom baffle toward the hot wall. For all baffle locations, the average Nusselt number is smaller than the corresponding value in an enclosure with no baffles.

ISSN:0149-5720    

DOI:10.1080/10407788608913532

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0149-5720    

DOI:10.1080/10407788608913533

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor