Modelling and Applications of Transport Phenomena in Porous Media

These books are written in very different styles. In a sense they are complementary, though many workers comfortable with the content and presentation of one might find the other relatively unattractive. The first is intended ‘to provide a user-friendly introduction to the topic of convection in porous media . . . (employing) only routine classical mathematics , . . as a review and as a tutorial work ’. It adopts familiar constitutive models for transport of mass momentum and energy in homogeneous saturated porous media, and uses them to solve boundary value problems by standard mathematical techniques. The book is tightly written, the applications are precisely defined and the approach, which relies heavily on dimensionless formulations, will be familiar to most engineering scientists. Within the range of topics chosen it is comprehensive, but it tends not to stress the real difficulties of reducing engineering or geomechanical problems to tractable mathematical form. The second is a collection of separately authored chapters of greatly varying length and content, which has the paradoxical advantage of showing that there are different ways of looking at any given process. Much of it is very formal, and is concerned with setting up the basic continuum models (constitutive relations) that others might use. Three relatively specialized examples (two of these from the nuclear industry) are considered, covering boiling and drying. There is little connection between the various chapters. It should be noted that it is volume 5 in a series on Theory and Applications of Transport in Porous Media. I found considerable overlap with parts of volume 4 : the first long chapter by Bear, which occupies nearly half of volume 5 , is to some extent a digest of volume 4. Neither is as balanced a text from the point of view of an engineering scientist as that reviewed earlier (Theory of Fluid Flows through Natural R O C ~ S , by Barenblatt, Entov & Ryzhik, volume 3 of the Kluwer series, see J . Fluid Mech. 223 (1991), p. 663). Though Nield & Bejan stands very well on its own, it is primarily an academic textbook (and a very good one too) ; I hope that it does not sound churlish to argue that the limitations that academics impose upon themselves to maintain elegance and simplicity detract somewhat from the merit of their work as sources for engineers : real problems arise because of the inadequacies of our existing models, and unless this is emphasized there is a danger that engineers trained by academics-will use inappropriate models. In the case of real porous media, the continuum assumption of an isotropic homogeneous undeforming medium with Darcy-like behaviour always has to be carefully examined : if the mathematical modeller does not carry out such an examination and assess the consequences of any departures from the assumption, the chances are that nobody will. To this extent the rather arid and formal development of continuum equations is an important discipline. An understanding of the relevance of averaging processes and of their consequences for averaged continuum equations should always be emphasized in texts for engineers. I can therefore commend chapter 6 by de Marsily 408 pp. DM128.