The forces acting on an elastic particle suspended in a shear field, and moving relative to it, are found for the case in which there are small deformations from an initially spherical shape. The deformation is the result of the viscous stresses acting on the particle. Of principal interest is that there is a component of the force perpendicular to the free-stream direction, so that the particle will migrate across the undisturbed streamlines.

This paper presents the analysis and numerical solution for the axisymmetric analogue of the problem considered by Proudman & Johnson (1962) and Robins & Howarth (1972).

The formalism of transport theory is adapted to a general description of bubble populations in a moving fluid. The bubble distribution, as a function of position, velocity, radius and time, satisfies a Boltzmann-type transport equation that is derived and then formally solved by the method of characteristics. In order to apply this new analytical tool to the specific problem of gas bubble transport in the upper ocean, an ocean model and a bubble dynamics model must be chosen. For the purpose of illustration, explicit solutions are written, for distributed sources in a stationary ocean with simple expressions for bubble gas diffusion and drag. Calculated results clarify the relations between observed bubble distributions at sea, proposed bubble source mechanisms and known models of single-bubble dynamics.

The possible coexistence of laminar and turbulent flow in a triangular duct had been a point of controversy among several authors. Since the nature of the flow-laminar or turbulent-has a major influence on the head loss and heattransfer characteristics of the flow, resolution of this controversy is of practical as well as theoretical value.

It is shown that the multiplicative rule of the method of matched asymptotic expansions fails under certain conditions. The velocity distribution in front of an elliptic airfoil is given as an example. The reason for the breakdown is explained by inspecting the usual formal justification of multiplicative composition.

Experimental results are presented for the speed of travel of the spherical vortex at the front of a suddenly switched on, submerged, laminar jet in the Reynolds number range 80 < Re < 500. The results show that the speed of advance of the front is approximately one half of the speed of a fluid element on the axis of the steady jet. The experimental data are well correlated by an approximate model of the jet–vortex interaction in which the vortex is treated as a liquid drop with averaged properties. An auxiliary result is a new correlation for the axial variation of the velocity of a steady jet.

The method of multiple scales is used to derive equations governing the temporal and spatial variation of the amplitudes and phases of in viscid capillary–gravity travelling waves in the case of second-harmonic resonance (Wilton's ripples), but including the effects of: (i) near resonance, (ii) liquid depth, and (iii) pressure perturbations exerted by an external subsonic gas on the liquid–gas interface. The spatial form of the equations shows that, below a critical gas velocity, energy is transferred between the fundamental and its first harmonic in keeping with the energy conservation law. However, the amplitude of the first harmonic decreases with increasing gas velocity. Above the critical gas velocity, the displacement of the gas–liquid interface grows monotonically with distance. It is found that pure amplitude-modulated waves are possible only at perfect resonance. Pure phase-modulated, near-resonant waves are periodic, as the resonance forces a readjustment of the phases to produce perfect resonance. The effectiveness of the resonance in rippling the interface increases as the liquid depth decreases.

The problems of tsunami generation are treated by standard integral-transform and modified stationary-phase methods to yield asymptotic approximations to the surface disturbances. The effects of asymmetry are considered in a one-dimensional ocean. Series representations are used to produce sets of normal-mode oscillations in a two-dimensional ocean, and the magnitudes of the wave front and wave train are discussed in relation to the asymmetry of the generating region.