# Take account of some properties that get the blood moving

Fundamentals of Fluid Mechanics. Fifth edition - Introduction to Fluid Mechanics. First edition
December 2, 2005

These are two very different books. Although Fundamentals of Fluid Mechanics has some interesting and unusual examples, such as a consideration of a giraffe's blood pressure, it is very difficult to see how it could be recommended for use as a course book on any current UK engineering degree course because many of its treatments of fundamental aspects of fluid mechanics would have been considered to be at least 30 years out of date even when the first edition was published in 1989.

I shall give four examples of such problems in the early part of the book. There is the treatment of fluid properties in terms of "specific weight"- which is not a fluid property - rather than the density - which is a fluid property, and the specific gravitational force (g) - which is a system property; the treatment of unit systems; the treatment of forces and moments on submerged surfaces in terms of second moments of area; and the treatment of co-ordinate systems that bases the sign of small spatial variations in an unknown, on the basis of assumed knowledge of the eventual solution rather than on the basis of the positive co-ordinate direction and the correct specification of system forces.

An Introduction to Fluid Mechanics is altogether more satisfactory. The use of small sections on the history of the development of the subject is to be commended, as is the use of outputs from commercially available computational fluid dynamics codes to illustrate phenomena. It is, perhaps, unfortunate that more reference is not made in the consideration of the system and the control volume approaches, to the closely similar concepts used in both dynamics (of mechanical systems) and thermodynamics. There is, however, a very useful section on the relationship between the Bernoulli equation and the energy equation.

Equally, it would have been nice if the section on dimensional analysis contained a reference to the relationship between the number of permissible "base dimensions" and the fundamental physical laws governing the phenomenon under investigation. In some problems of celestial fluid mechanics, Einstein's theory of relativity may be applicable so that mass, length and time may not appear together in a list of "base dimensions" and, equally, the gases may not be treatable as a continuum so that some form of the kinetic theory of gases applies and temperature cannot be considered as a "base dimension".

In the sections on the differential analysis of flow, teaching experience suggests that care would need to be taken to ensure that students are not overwhelmed by the relatively rapid introduction of tensor representations of stresses and velocity gradients. It is unlikely that a typical UK engineering degree course would cover more than a limited part of the latter sections.

Robert Cheesewright is research fellow in design and systems engineering, Brunel University.

## Fundamentals of Fluid Mechanics. Fifth edition

Author - Bruce R. Munson, Donald F. Young and Theodore H. Okiishi
Publisher - Wiley
Pages - 770
Price - £38.95
ISBN - 0 471 67582 2