摘要:

AbstractA coupled finite element model is developed to simulate the metal casting process. We present a new method for capturing the solidification zone and obtaining the corresponding rate of phase change. The latent energy release is predicted by the heat conduction rate and introduced by following the enthalpy‐temperature curve. The influence of mould‐metal contact is considered in calculating the heat flux through the mould‐metal interface. A viscoplastic model is employed to predict the gap opening and evolution of plastification.Four examples are presented to demonstrate certain numerical aspects and the capability of the model for industrial applica

ISSN:0029-5981    

DOI:10.1002/nme.1620300403

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAfter having finished the FE computer run and determined the temperature vector of a heat conducting body the question arises how to present these results in an easily understood way. The only tool to manage this task satisfactorily is the application of graphics. This paper reflects the due historical roots and gives an overlook of the relevant developments. Recently, there have been special advantages concerning finite element results presentations of temperature fields. This concerns the temperature field colouring, which can be considered as an indirect method of contouring, and the direct method of contouring, which means finding and connecting points of equal temperature. In the 3‐D case these features are to be combined with hidden surface or hidden line removal techniques to give easily perceptible pictures. Sometimes, not just the temperatures but the heat fluxes attract the main interest. An adequate method is the drawing of heat flux arrows. This is taken into account, too. With 2‐D problems, the presentations of temperature distributions by mountains is popu

ISSN:0029-5981    

DOI:10.1002/nme.1620300404

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper describes a numerical method of radiant environment analysis in a complicated enclosure containing human bodies and furniture. An arbitrary configuration expressed in a three‐dimensional co‐ordinate system can be treated by this method. A unique space index and another surface index are proposed to specify the geometry of solid body and surface in the enclosure. The Monte Carlo method is used to determine direct interchange areas, which are then transformed into total exchange areas using the zone method. Energy balance equations accounting for thermal radiation, convection, wall conduction and air ventilation are then formulated for each solid surface segment in the enclosure. A human body model with skin temperatures and clothing is also proposed to simulate its heat release and to predict local thermal sensation around the body. As a practical application, this method is applied to the analysis of the radiant environment in a floor‐heated meeting room with eight people seated around a

ISSN:0029-5981    

DOI:10.1002/nme.1620300405

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThis paper describes the use of field and zone modelling techniques in studying the behaviour of LPG tanks when subjected to accidental fire conditions. The field modelling approach is used to determine the free convective flows and heat transfer in both the vapour and the liquid regions, and also the heat transfer through the tank wall. Zone modelling techniques are employed to calculate the fire heat flux and the radiation heat transfer from the vapour wetted wall to the liquid/vapour interface. The model is verified by comparing predicted results with full scale experimental data obtained by the Health and Safety Executive, U.K.1The comparisons indicate that the model can accurately predict the tank pressure and time to first valve opening. The model is used to investigate the effect of fire exposure level on the tank behaviour.

ISSN:0029-5981    

DOI:10.1002/nme.1620300406

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe governing equations and the boundary conditions of steady incompressible magnetohydrodynamic (MHD) problems are adapted to the case of steady MHD flow in simply connected cross sections with arbitrary wall conductance. The problem is then solved numerically by means of the finite element method based on the weighted residual approach, and solutions for industrially relevant Hartmann numbers and non‐symmetric kinetic fields are presente

ISSN:0029-5981    

DOI:10.1002/nme.1620300407

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractSeveral iterative procedures have been used to solve the non‐linear heat diffusion equation taking into account radiation across internal cavities. Quasi‐Newton methods are compared with Picard iteration and Newton‐Raphson methods. Among them, the rank‐one quasi‐Newton update seems to be the most effective, specially in time‐depe

ISSN:0029-5981    

DOI:10.1002/nme.1620300408

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe numerical simulation of conduction heat transfer in arbitrarily‐shaped regions is relevant to many engineering applications including the casting of plastics and metals, cold region problems and latent heat storage. This class of problem offers its particular challenges. The accurate computational simulation of conduction with thermally‐dependent properties requires a solution technique with good conservation properties. The boundary‐fitted co‐ordinates of an arbitrary solution domain typically yield grids which are non‐orthogonal and which, consequently, make energy conservation difficult to model.In the current article, a technique is described to simulate accurately the conduction heat transfer in materials of thermally‐dependent properties in irregular domains. The method combines boundary‐fitted co‐ordinates with the finite volume method, FVM, to produce a numerical technique which will accurately solve this non‐linear conduction problem using a grid which may be highly skewed. This capability is achieved through a unique treatment of the cross‐derivative terms that arise when the heat conduction equation is transformed to a non‐orthogonal grid. The cross‐derivative terms represent the non‐normal components of the heat fluxes into the skewed control volume. The tangent components of the heat fluxes are interpreted in a special way to produce finite difference expressions which accurately model the cross‐derivative partial.The numerical procedure is validated by comparing it against a purely analytical mathematical method. Although the numerical results have been obtained using a highly skewed grid, they exhibit close agreement with the an

ISSN:0029-5981    

DOI:10.1002/nme.1620300409

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn this paper, a generally applicable version of an algorithm, for multidimensional phase change conduction, is presented which bridges the gap between ‘full enthalpy’ and ‘equivalent heat capacity’ methods. In the text the problem is formulated first with reference to the three‐time‐level method for the FE analysis of non‐linear heat conduction. Then the suggested algorithm is utilized as a ‘corrector’ which can be activated for the analysis of isothermal phase change problems. In the corrector step the enthalpy balance is recovered from the standard formulation, and temperatures are post‐calculated by means of the inverse temperature vs. enthalpy function. The algorithm is verified in one‐dimensional situations by comparing the results obtained with available analytical and numerical solutions for boundary conditions of the first kind (temperature) and of the third kind (convection). Finally, as a 2‐D test problem, a solution is presented for inward solidification in a cylinder, using Cartesian co‐ordinates to demonstrate robustness with respect to spac

ISSN:0029-5981    

DOI:10.1002/nme.1620300410

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractApplication of the Alternating Direction Implicit (ADI) method to study solidification problems reveals some drawbacks. At the interface between different‐materials, temperature oscillations may be recorded at the simulation start which eventually may cause instability. The problems originate from the explicit temperature calculation. Shortcomings may be eliminated by substituting the explicit temperature calculation by an implicit one which is carried out on a limited number of adjacent elements. Results of real solidification problems show that the modified method behaves better than the original ADI method. The new procedure, which is formulated in terms of the finite volume method, eliminates the occurrence of physically incorrect temperature calculations and oscillations initially present in the vicinity of the interface between different materials. When applied to the three‐dimensional solidification problem of the sand coated die, simulation results are in good agreement with experimental d

ISSN:0029-5981    

DOI:10.1002/nme.1620300411

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractAlthough it is now well known that first‐order convection schemes suffer from serious inaccuracies attributable to artificial viscosity or numerical diffusion under high‐convection conditions, these methods continue to enjoy widespread popularity for numerical heat‐transfer calculations, apparently owing to a perceived lack of viable high‐accuracy alternatives. But alternatives are available. For example, non‐oscillatory methods used in gasdynamics, including currently popular ‘TVD’ schemes, can be easily adapted to multidimensional incompressible flow and convective transport. This, in itself, would be a major advance for numerical convective heat transfer, for example. But, as this paper shows, second‐order TVD schemes form only a small, overly restrictive, subclass of a much more universal, and extremely simple, non‐oscillatory flux‐limiting strategy which can be applied to convection schemes of arbitrarily high‐order accuracy, while requiring only a simple tridiagonal ADI line‐solver, as used in the majority of general‐purpose iterative codes for incompressible flow and numerical heat transfer. The new universal limiter and associated solution procedures form the so‐called ULTRA‐SHARP alternative for high‐resolution non‐oscillatory multidimensional steady‐st

ISSN:0029-5981    

DOI:10.1002/nme.1620300412

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY