This book is the author''s undergraduate dissertation. It attempts to provide a discussion on the results obtained from large-scale parallel numerical simulations of natural convection inside square and rectangular enclosures filled with porous media. The simulations were the outcome of a study which was part of a research project undertaken by the author under the guidance of Prof. Arunn Narasimhan and Prof. Babu Viswanathan at the Heat Transfer and Thermal Power Lab at Indian Institute of Technology Madras in 2009. Despite the specialized nature of the subject, this book serves as a useful resource to learn how the lattice Boltzmann method (LBM) can be implemented on a parallel cluster. It also provides a brief historical overview of the study of flow and heat transfer through porous media.