PhysicalHydrodynamics

Abstract

9R46. Physical Hydrodynamics. - E Guyon (Ecole Normale Superieure, Paris, France), J-P Hulin (CNRS Laboratoire Fluides, Automatique et Systemes Thermiques, Univ Paris Sud, Orsay, France), L Petit (Univ de Nice, Sophia Antipolis, France), CD Mitescu (Pomona Col, Claremont CA). Oxford UP, Oxford, UK. 2001. 505 pp. Softcover (Hardcover ISBN: 0-19-851746-7, $100.00). ISBN 0-19-851745-9. $50.00. Reviewed by DF Jankowski (Dept of Mech and Aerospace Eng, Arizona State Univ, PO Box 875506, Tempe AZ 85287-5506).Books and monographs on fluid mechanics that explore new topics and enliven old ones with fresh insights continue to be written. This reality is a natural consequence of the important scientific and engineering opportunities and discoveries that continue to appear within this well-entrenched discipline. For a variety of reasons, these newcomers sometimes have a difficult time breaking into the established patterns for the formal use of such material. According to its preface, Physical Hydrodynamics “was written primarily from the point of view of an experimental physicist;” it is an English edition of a book originally published in 1991 for a “French-speaking physics audience.” The authors mention their attempt to “adapt the style and form [of the book] to one which might prove more comfortable to North American audiences…” They further state that the “text has been extended…to increase the content in applications, and bring it a step closer to an engineering approach.” The expected background for the study of the book is not addressed although the brief foreword by PG DeGennes notes that “this textbook…is not directed towards students who are totally uninitiated.” For these reasons, one approaches the book with some uncertainty about its possible role in an educational system in which engineering students are the primary audience for formal courses in fluid mechanics. Some hints and opinions in this regard will be passed along as this review continues. It is worth noting that many members of the fluid-mechanics community, whether engineers or scientists, would probably argue in favor of more physical arguments and understanding in fluid-mechanics courses. As expected, the book is attractively produced; its figures and photographs are helpful to the reader. The publisher should also be thanked for the existence of a softcover version. It totals nearly 500 pages and is organized into 10 chapters, several with beneficial appendices, and a longer appendix on superfluid helium at its end; incompressible modeling is used throughout. Each chapter has a short, useful abstract. The bibliography is limited in scope, but does include some references to pertinent films and experiments. The lack of any problems for solution by students is a negative factor for possible classroom users, and certain analogies, for example, with electromagnetic field theory, scattered here and there in the book, are likely wasted on most engineering students. While the authors choose not to do so, the book might be divided into several general sections. The first, consisting of Chapters 1 and 2, provides a fairly involved start, very much from the point of view of a physicist; many engineers can reasonably expect to have difficulty with some of this material, for example, the spectroscopy of liquids. Chapters 3, 4, and 5, which introduce kinematics and the local and global governing equations, form a general section on fundamentals. The authors refer to the next four chapters as the “basis of fluid mechanics,” and note that they are structured “in such a way that they can be studied independently and in arbitrary order.” The final chapter briefly explores a natural capstone area. Aspects of turbulence appear in several places, but it is not a mainstream topic of the book. The material of the first two chapters, Physics of fluids and Diffusion of momentum under various flow conditions, fills nearly 90 pages. Both display an interest in the relationships between microscopic characteristics and macroscopic properties. The starting point is the transport of heat and mass by diffusion, which is followed by the increasingly important topic of surface effects, including surface tension. The examples for the latter topic are well chosen. The first chapter ends with 15 pages on the spectroscopy of liquids. Chapter 2 extends the treatment of the transport of (scalar) mass and heat to the diffusive and convective transfer of (vector) momentum; related motivating examples are used as appropriate. The property of viscosity and the coefficient of viscosity are discussed macroscopically and microscopically. An interesting introduction of the Reynolds number (Re) through a comparison of diffusive and convective effects for momentum and a set of similar results for mass and heat transport are provided. The chapter ends with an example-based description of different flow regimes as Re changes; whether it provides motivation or frustration will likely depend on the preparation and talent of the reader, of whom a fair amount is expected. Chapter 3, Kinematics of fluids, starts with the usual kinematic topics, velocity, acceleration, Eulerian and Lagrangian descriptions, and steamlines, streaklines, and pathlines; there are no surprises in this material. The following section on flow visualization is more interesting, as is the material on the deformation in fluids, the local conservation of mass, incompressibility, the stream function, and the measurement of velocity and velocity gradients. The next chapter, Dynamics of fluids: Local equations, continues the treatment of selected fundamentals, moving efficiently from Newton’s equation of viscosity to the Navier-Stokes equations, with a detour to discuss some examples of non-Newtonian behavior. Devotees of continuum mechanics would argue that the symmetry of the stress tensor is a consequence of a basic principle, would probably be more careful in the use of strains versus strain-rates, and might expect a definition for mechanical pressure (pages 132 and 142). Once the Navier-Stokes equations are available, attention turns to the corresponding boundary conditions, and, finally, to the solutions of a series of example flow problems, both standard and non-standard. Experimental results are available for some of these examples, but are not provided. The use of “low velocities” in a discussion related to eliminating certain terms from the Navier-Stokes equations (page 147) is unnecessarily casual. Chapter 5, Conservation laws, focuses on selective treatments of various aspects of the conservation of mass, momentum, and (kinetic) energy. The major ideas are the global (control volume) forms of these equations, and derivations and applications of the Bernoulli equation. A number of largely routine examples that can be found in many undergraduate engineering textbooks occupies the final portion of the chapter. The next chapter, Potential flow, is substantially longer than each of the previous three chapters. Its contents provide a largely historical account of a classical subject. The topics treated are flows generated by selected potential functions, forces on obstacles, surface waves, and the use of complex-variable theory for potential flows. Chapter 7, Vorticity: Dynamics of vortices, is an obvious next step, and connections between these two chapters are noted. The electromagnetic analogue of vorticity is used freely in the discussion. After the concept of circulation, the transport equation for vorticity, and their consequences are studied at length, attention is turned toward a series of examples, systems of vortex lines, vortex sheets, and vortex rings, providing another serious task for the reader. The longest chapter in the book, Flow at Low Reynolds Numbers, appears next. This subject is attractive because small Re is relevant in many situations and because its linear mathematical base allows relatively simple theoretical determinations of flow properties, such as the forces and torques acting on a moving solid body. The flow past a sphere at low Re and related variations are given complete treatments. The chapter closes with fairly detailed discussions of a problem from the so-called lubrication theory, the dynamics of suspensions, and flow in porous media. The initial portion of Chapter 9, Laminar boundary layers, differs in some details from standard engineering sources, but it still focuses on the usual boundary layer on a flat plate and the special characteristics of similarity boundary layers, which, according to the authors, “apply very generally in a wide variety of situations.” Insufficient background for approaching more general applications, such as the boundary layer on an airfoil or an internal boundary layer, is provided. The later portion of the chapter is somewhat more promising, with its discussion related to various aspects of separation followed by a more technical treatment of an interesting series of non-standard topics including mass, thermal, and concentration boundary layers, and laminar wakes. The final chapter is a useful treatment of Hydrodynamic instabilities, an area of fluid mechanics to which physicists have made important contributions. Most attention is devoted to the exploration of the instabilities due to buoyancy, temperature-dependent surface tension, and centrifugal force; differing shear-flow instabilities are treated only briefly. In summary, it can be fairly stated that this book, Physical Hydrodynamics contains many parts of varying size and often subtle insights that individual readers, including experienced teachers, will find appealing, depending upon their needs and purposes. Some of them will probably find their way into graduate or transitional senior-graduate courses. While the book contains too much material to uncover in a typical academic semester, several different courses might be formed from it. Many students would be challenged—this is not a criticism—by its expectations that the reader think and reason both in and outside the framework of mathematical modeling. Finally, in spite of a wish that the announced step toward an engineering approach had been a bit longer, it is reasonable to offer the opinion that this is a book that should find a place in offices and cubicles whose occupants believe in the need for understanding its inventory of concepts from fluid mechanics.