Nowak, A.J. and Biaecki, R.A. (2008), "Preface", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 18 No. 3/4.



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Article Type: Preface From: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 18, Issue 3/4.

These two special issues of the International Journal of Numerical Methods for Heat and Fluid Flow comprise selected papers presented during the International Scientific Conference on Numerical Heat Transfer (NHT2005). The conference was organised as the EUROTHERM Seminar 82 and was held on 13-16 September 2005 in Cracow, Poland.

Papers published in these two special issues have been selected to demonstrate, on the one hand, an overview of the conference topics and, on the other hand, to document the most important advances in numerical heat transfer. Each special issue consists of seven papers.

The first special issue opens with a contribution from Yogesh Jaluria entitled “Numerical simulation of complex transport phenomena arising in practical thermal systems.” The author discusses in his paper such problems as non-linear properties of the medium, complicated geometries, conjugate mechanisms, chemical reactions and combined mass transfer, and intricate boundary conditions that are often encountered in important industrial processes. The remaining papers in this issue focus on application of thermal problems in industry and science. Hence, ZalozÏnik et al. is numerically modelling the macrosegregation in direct chill casting. The authors focus their attention on aluminium casting which is an important branch of industry. The third contribution comes from Postek et al. who present the finite element modelling of the squeeze casting process. The mould filling equations and associated thermal energy and thermomechanical equations are discretized using the Galerkin method. The coupling between mould filling and thermal problems is achieved by solving the thermal energy and the Navier-Stokes equations explicitly at the end of each time step. This allows the authors to determine the actual position of the front of the filling material. The next paper by Bulinski et al. discusses the free surface flow and heat transfer in the process of mould filling during the manufacturing of electrical transformers. Considered problems are not only numerically simulated but also experimentally validated. Amberg and Do-Quang concentrate in their paper on the thermocapillary convection and phase change in the welding. They pointed out that in certain materials, the weld pool may not penetrate the material easily, so it is difficult, or even impossible, to weld, while other seemingly quite similar materials may be well suited for welding. Through recent 3D simulations the authors studied how surface active agents affect the flow and thus the welding properties. Wawrzonek et al. show in their contribution a friction heating process of a disk brake in the context of its application in the explosive atmosphere of coal mines. Temperature profiles obtained from computer simulations are then experimentally verified. The last paper in this issue consists of the inverse analysis based on an evolutionary algorithm approach for the identification of the non-linear heat generation rates in living tissues. Such heat generation rate is by Erhart et al. modelled by the bio-heat (Pennes) equation and solved using a new localized meshless method and creating a more robust and computationally efficient algorithm.

The second special issue is generally devoted to radiation (two papers) and heat convection (five papers). In the first paper, Viskanta presents computational methods for radiative heat transfer in combustion systems. In particularly, the author discusses the methods of solution of the radiative transfer equation. These methods allow one to simulate chemically reacting flow and heat transfer in combustion systems. The application of the equation of radiative transfer to state-of-the-art optical tomographic image reconstruction is discussed in the next paper by Klose et al. The authors point out that in the visible to near-infrared wavelength range biological tissue is a highly scattering medium and light propagation is most accurately modelled using their approach. The third paper by Gobin et al. presents an overview of problems dealing with the natural convection in vertical cavities or horizontal layers partially filled with a saturated porous medium. The authors define key problems arising during modelling of the fluid flow together with heat and mass transfer in composite domains. Then various formulations concerning the presence of a porous layer in a vertical enclosure are discussed and solved. An extensive overview of the two-phase flow and heat transfer problems, together with the discussion of their multidimensional mathematical modelling is then given by Podowski. The fifth paper by Ramšak and Škerget presents the application of the boundary element method for modelling of the thermal flows using k-1 turbulence models. The simulation of a turbulent flow over a backward step demonstrates excellent agreement with the finite volume method using the same turbulent model. Analysis of the macroscopic momentum equation in a columnar mushy zone is the subject of the following contribution by Furman´ski et al. In particular, the impact of different forms of this equation on numerically calculated velocity and temperature distribution in the mushy zone is studied for binary alloy solidification with buoyancy-induced thermal convection. The authors conclude eventually that the chosen formulation of the momentum equation mildly affects temporal velocity and temperature fields at longer times of the solidification process. The last paper in this issue deals with the numerical study of turbulent channel flow affected by the strong temperature gradients. Lessani et al. find that the mean velocity profile at the cold side deviates from the classical isothermal logarithmic law of the wall.

We are indebted to all authors for their contributions to these two special issues, for their cooperation and support. We hope that these two issues provide a window on the current interests in numerical heat transfer, while at the same time documenting recent advances in this fascinating research area.

Andrzej J. Nowak and Ryszard A. BiaøeckiInstitute of Thermal Technology, Silesian University of Technology, Gliwice, Poland