TRANSIENT THERMAL ANALYSIS OF NATURAL CONVECTION IN POROUS AND PARTIALLY POROUS CAVITIES F. Arpino 1 , G. Cortellessa 1 , and A. Mauro 2 1 Dipartimento di Ingegneria Civile e Meccanica, Universita ` degli Studi di Cassino e del Lazio Meridionale, Cassino, Italy 2 Dipartimento di Ingegneria, Universita ` degli Studi di Napoli ‘‘Parthenope’’, Centro Direzionale di Napoli, Napoli, Italy In this article, the authors numerically investigate dynamic heat transfer related to free convection in porous and partially porous cavities, paying particular attention to the depen- dence of velocity and temperature fields on Rayleigh (Ra) number, porous layer per- meability, and cavity aspect ratio (AR), the ratio between its height and width. Heat and fluid flows inside the cavity are described by using the generalized porous medium model, and the governing equations were numerically solved using the artificial compress- ibility version of the characteristic-based split scheme. The proposed model was first applied to the simulation of heat and fluid flows in a square porous cavity, and an excellent agree- ment was found between the results obtained and the data available in the literature. The analysis was then extended, here for the first time, to transient natural convection in partly porous cavities, with AR equal to 4:1 and 8:1 for different Ra and Darcy (Da) numbers. The mean Nusselt (Nu) number was calculated as a function of cavity geometrical charac- teristics, porous layer permeability, and fluid properties. 1. INTRODUCTION Natural convection in fluid-saturated porous and partially porous cavities is of great interest in many engineering applications. In fact, this phenomenon has moti- vated a large amount of research activity in various engineering fields, including, among others, geothermal energy utilization [1, 2], pollutant dispersion in ground- water, reactant diffusion in porous electrodes [3–6], reactive flows in porous media, gaining the attention of scientists in the fields of applied mathematics and chemical, civil, mechanical, and bioengineering. This wide area of interest has generated a con- siderable number of investigations over the past 50 years, with particular reference to Darcian forced and natural convection fluid flow [7] and to its extensions to non- isothermal buoyancy effects description by invoking the Bousinnesq approximation. Received 29 October 2013; accepted 24 July 2014. Address correspondence to G. Cortellessa, Dipartimento di Ingegneria Civile e Meccanica, Universita ` degli Studi di Cassino e del Lazio Meridionale, Via G. Di Biasio 43, 03043 Cassino, FR, Italy. E-mail: g.cortellessa@unicas.it Color versions of one or more of the figures in the article can be found online at www.tandfonline. com/unht. Numerical Heat Transfer, Part A, 67: 605–631, 2015 Copyright # Taylor & Francis Group, LLC ISSN: 1040-7782 print=1521-0634 online DOI: 10.1080/10407782.2014.949133 605 Downloaded by [Queensland University of Technology] at 01:59 28 January 2015