Guest editorial

Citation

Malan, A.G. and Meyer, J.P. (2008), "Guest editorial", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 18 No. 2. https://doi.org/10.1108/hff.2008.13418baa.001

Guest editorial

Article Type: Guest editorial From: International Journal of Numerical Methods for Heat & Fluid Flow, Volume 18, Issue 2.

The 4th Annual Heat Transfer, Fluid Dynamics and Thermodynamics Conference (HEFAT) took place in Cairo in 2005. The objective of this conference is to bring together researchers engaged in the application of experimental, analytical or computational heat and mass transfer, fluid flow, and thermophysical properties. This special section is composed of a selection of presented papers which are concerned with new and valued developments in the computer-based modelling of heat and fluid-flow problems.

Computational heat transfer and fluid flow is a field which has become invaluable to the engineering fraternity. It is also a field which is rapidly progressing in response to the growing demand from industry to model more complex systems with greater efficiency and accuracy. In this regard, current research trends are moving toward unified solvers and methodologies, particularly where multiphase systems are concerned. This is also the main topic of the special section, of which the first paper is entitled “A unified fractional step method for compressible and incompressible flows, heat transfer and incompressible solid mechanics” by P. Nithiarasu. In this paper, Nithiarasu introduces, for the first time, a single-governing equation set and related solution method which unifies the two historically segregated fields of fluid and solid mechanics. In the process, he gives rise to a new perspective on fluid-structure interaction modelling.

The next article deals with the complex multiphase problem of phase change due to solidification in stirred melts, viz. “Parallel computation of multiscale phenomena in magnetically-stirred solidifying melts” by B.Q. Li. The author models all macro-scale phenomena including the electromagnetic field, melt convection and heat transfer, while in addition simulating micro-scale phenomena such as nucleation and dendrite growth. The required governing equations are discretized and solved with a combined boundary element and finite element method and solved via parallel computation due to the large amount of physics being modelled. The third multiphase-related article similarly deals with phase change, only here the focus is on evaporation, viz. “A numerical model for calculating the vaporization rate of a fuel droplet exposed to a convective turbulent airflow” by M.M. Abou Al-Sood and M. Birouk. In this work, a 3D computational model to predict the vaporization rate of a liquid fuel droplet, which is subjected to turbulent airflow, is developed. This is not only a complex problem from a fluid-flow modelling perspective, but it is at present of considerable importance to both industry and academia. The authors obtain accurate predictions and show for the first time, how both fluid and gas phases may be effectively modelled by using a simple blocked-off technique.

The next multiphase-related paper is entitled “Population balance models for subcooled boiling flows” by M.K.M. Ho, G.H. Yeoh and J.Y. Tu. This paper deals with the modelling of liquid flow which contains entrained gas, by employing two population balance approaches, viz. the MUltiple SIze Group (MUSIG) and average bubble number density transport equation (ABND) methods. The authors enhance the latter method, and find that both approaches may be used to predict the void fraction radial profile, bubble Sauter mean diameter and interfacial area concentration. The ABND model was however found to be less accurate than the other method when considering high-subcooled boiling flows, while offering an economic alternative in terms of computational cost and complexity in other instances.

The final two papers in the special section focus on the combination or unification of numerical discretization aspects of heat transfer and fluid-flow modelling technology. The first is entitled “Application of high-order spatial resolution schemes to the hybrid finite volume/finite element method for radiative transfer in participating media” by P.J. Coelho and D. Aelenei. In this work, the authors propose a hybrid finite volume and finite element methodology where a high-order scheme is employed to discretize the radiation density spatial terms. The paper demonstrates an interaction between spatial and angular discretization errors, and shows that improved accuracy may be realised from high-order approaches in the case where the angular-related error is relatively small. The next and final paper is “A flow network formulation for compressible and incompressible flow” by J.J. Pretorius, A.G. Malan and J.A. Visser. Here, a hybrid method is employed to solve both incompressible and highly compressible flows in pipe networks via a newly proposed single-governing equation set. The methodology is demonstrated to yield results of similar or significantly improved accuracy as compared to that of others, while being successful in modelling both gas and liquid flows.

Arnaud G. Malan and Josua P. Meyer