Fluid dynamics. A basic course for undergraduated university students. With CD-ROM. (Q2779227)

This is the second (posthumous) edition of Ryhming's texbook after his premature death. His collegues Deville and Drotz decided to republish the book without changing the contents, but adding some recent topics for illustrating in real time the evolution of certain phenomena of flows. In fluid mechanics there are austere treatises, like that of Lamb, Kaufmann, Batchelor and others, and plenty of ``didactical'' books destined for university students. This work is half-way between these two extremes: basic notions of fluid mechanics are accompanied by their complete mathematical description. The book covers classical subjects of the discipline, that is incompressible ideal fluids, viscous incompressible fluids, ideal gases. There is a first introductory chapter containing an overview on the fundamental problems, two chapters in which the balance equations are derived, and three chapters treating perfect, viscous, compressible fluids, respectively.NEWLINENEWLINEThe first chapter is a survey, partly historical and partly technical, of the great problems solved by scientists from Euler to Prandtl, and of the practical applications of these solutions. In little more than twenty pages the author is able to trace a vivid illustration of the discipline. The subsequent three chapters, dedicated to balance equations, are less synthetic. The local forms of these equations are derived here by the engineering procedure of splitting the temporal variations of the fields into a part due to their intrinsic variations and into another accounting for the filtrations across the surface of an arbitrary volume. This method is not incorrect, but the application of Liouville's theorem is more systematic and safer. On the other hand, both chapter are enriched by interesting examples, like the free surface generated by a vortex, a simplified theory of water hammer, the pressure exerted by a jet impinging against a lamina.NEWLINENEWLINENEWLINEChapter 5 (one of the longest) treats potential motions. The reader notes with pleasure that, before proposing particular solutions, the author discusses the correct formulation of boundary value problems and their solution through the method of separation of variables or of distribution of sources. Here there are several original examples, like the flow around a rigid circle generated by a source, and the longitudinal flow in an undulated tube. Chapter 6 (dealing with viscous liquids) is mathematically less accurate, and less inventive in the choice of applications. But the treatment of boundary layers is done with unusual clearity and richness of results. For example, the elegant solutions proposed by Holstein and Bohlen, and by Walz-Thwaites are ignored in other treatises. And the same praise can be extended to the section dedicated to the deduction of equations of turbulent motions. Here, however, the examples are less illustrative since they rely on certain approximations suggested by experiments and not by theory.NEWLINENEWLINENEWLINEThe seventh chapter, dealing with gases, starts with the deduction of the equation of balance of energy with the same technique (and the same reservations) advanced for other balance equations. The chapter can be divided into three sections: heat propagation in a boundary layer, one-dimensional shock waves, potential treatments of the problems. The theory is accompanied by some examples, some of which are useful, but others are too involved.NEWLINENEWLINENEWLINERyhming's book is an excellent contribution to the diffusion of fluid mechanics. It has at least three qualities that are often absent in others works on the field (Lamb's monumental treatise included). The first is that Ryhming offers a balanced treatment of the discipline, giving the right space to each topic according to its mathematical and technical importance. The second is the tasteful choice of examples, simple but capable of catching the essential features of the phenomena. The third is the avoidance of purely numerical procedures which are unfortunately so very popular at present. On the other hand, the book might undergo some minor improvements, like, for example, a unified deduction of balance equations, a reduction in the number of examples collected in the seventh chapter, the addition of a final chapter containing a sketch on recent applications of fluids mechanics to metereology, blood circulation, sea coasts. Hopefully, there will be soon a new improved edition, further enhancing Ryhming's heritage.