The one-dimensional theory of steady flow in a thin-walled tube, partially collapsed by a negative transmural pressure difference, is developed in a general way. The mechanics of the flow is closely coupled to the mechanics of the tube. The latter is characterized by a “tube law”: the relationship between cross-sectional area and transmural pressure difference. Features analogous to those in gas dynamics and free-surface flow may manifest themselves: a characteristic wave propagation speed; opposite phenomena at flow speeds, respectively, less than and greater than the wave speed; choking; and shocklike transitions. There are many practical examples of such flows, mainly in physiology and medicine. The one-dimensional, steady analysis includes the effects of friction, lengthwise variations in external pressure, variations in elevation, resting area, wall stiffness, and mechanical properties. The speed index S (ratio of flow speed to wave speed), analogous to the Mach and Froude numbers, appears naturally in the results as a controlling parameter of behavior. Various practical ways of passing continuously from subcritical (S < 1) to supercritical (S > 1)speed are suggested. A preliminary theory of shocklike, dissipative transitions is developed, the results of which depend sensitively on the tube law. Explicit working formulas are developed for several simple types of flow (friction alone; changes in rest area alone; changes in external pressure or elevation alone) for a simple, approximate tube law. Various modes of flow behavior for a flow affected by both friction and gravity are explored.

Self-diffusion coefficients were determined experimentally for lateral dispersion of spherical and disk-like particles in linear shear flow of a slurry at very low Reynolds number. Using a concentric-cylinder Couette apparatus, recurrent observations were made of the lateral position of a particular radioactively labelled particle. The self-diffusion coefficientDwas calculated by means of random-walk theory, using the ergodic hypothesis. Owing to great experimental difficulties, the calculated values ofDare not of high accuracy, but are correct to within a factor of two. In the range 0 < ϕ < 0·2,D/a2ω increases from zero linearly with ϕ up toD/a2ω ≅ 0·02 (where ϕ = volumetric concentration of particles,a= particle radius, ω = mean shear rate of suspending fluid). In the range 0·2 < 0·5, the trend ofD/a2ω is not clear because of experimental scatter, but in this rangeD/a2ω ≅ 0·025 to within a factor of two. Within the experimental accuracy, spheres and disks have the same value ofD/a2ω.

Experimental results on flow-field statistics are presented for turbulent oscillatory flow in a circular pipe for the range of Reynolds numbers Reδ = U0δ/ν (U0 = amplitude of cross-sectional mean velocity, δ = (2ν/ω)½) = Stokes layer thickness) from 550 to 2000 and Stokes parameters Λ = R/δ (R = radius of the pipe) from 5 to 10. Axial and radial velocity components were measured simultaneously using a two-colour laser-Doppler anemometer, providing information on ensemble-averaged velocity profiles as well as various turbulence statistics for different phases during the cycle. In all flows studied, turbulence appeared explosively towards the end of the acceleration phase of the cycle and was sustained throughout the deceleration phase. During the turbulent portion of the cycle, production of turbulence was restricted to the wall region of the pipe and was the result of turbulent bursts. The statistics of the resulting turbulent flow showed a great deal of similarity to results for steady turbulent pipe flows; in particular the three-layer description of the flow consisting of a viscous sublayer, a logarithmic layer (with von Kármán constant = 0.4) and an outer wake could be identified at each phase if the corresponding ensemble-averaged wall-friction velocities were used for normalization. Consideration of similarity laws for these flows reveals that the existence of a logarithmic layer is a dimensional necessity whenever at least two of the scales R, u*/ω and ν/u* are widely separated; with the exact structure of the flow being dependent upon the parameters u*/Rω and u2*/ων. During the initial part of the acceleration phase, production of turbulence as well as turbulent Reynolds stresses were reduced to very low levels and the velocity profiles were in agreement with laminar theory. Nevertheless, the fluctuations retained a small but finite energy. In Part 2 of this paper, the major features observed in these experiments are used as a guideline, in conjunction with direct numerical simulations of the ‘perturbed’ Navier–Stokes equations for oscillatory flow in a channel, to identify the nature of the instability that is most likely to be responsible for transition in this class of flows.

THE appearance of the fifth edition proves that this classic is hard to replace. It is the book which Ls kept for handy reference by the students even after the completion of a course for which Milne-Thomson Ls the required text. The book's success Ls explained by a text which Ls both concise and precise, and by a wealth of examples solved as well as examples posed. Even though some of the vector notation appears old-fashioned and would be advantageously replaced by component notation, no such complaints are possible concerning the contents, which are kept up to date by the author in this new edition.

Besides the well-known earlier methods of rotating-disk calculations such as those developed by Grammel and others, an extensive treatment is given of more recently developed procedures including difference methods and those which involve the division of the disk profile into a number of conical-shaped segments, which are then fitted together. Since the author limits himself mainly to elastic conditions, very little information is given on such important practical subjects as the effects of plastic flow, creep, and fracture. In spite of this limitation, the book nevertheless should be of considerable interest and value to research men and designers.