Solutions for inviscid rotating flow over a right circular cylinder of finite height are studied, and comparisons are made to quasi-geostrophic solutions. To study the combined effects of finite topography and the variation of the Coriolis parameter with latitude a steady inviscid model is used. The analytical solution consists of one part which is similar to the quasi-geostrophic solution that is driven by the potential vorticity anomaly over the topography, and another, similar to the solution of potential flow around a cylinder, that is driven by the matching conditions on the edge of the topography. When the characteristic Rossby wave speed is much larger than the background flow velocity, the transport over the topography is enhanced as the streamlines follow lines of constant background potential vorticity. For eastward flow, the Rossby wave drag can be very much larger than that predicted by quasi-geostrophic theory. The combined effects of finite height topography and time-dependence are studied in the inviscid initial value problem on the f-plane using the method of contour dynamics. The method is modified to handle finite topography. When the topography takes up most of the layer depth, a stable oscillation exists with all of the fluid which originates over the topography rotating around the topography. When the Rossby number is order one, a steady trapped vortex solution similar to the one described by Johnson (1978) may be reached.

Experiments are described to study the motion and deformation of a synthetic, liquid-filled capsule that is freely suspended in hyperbolic extensional flow. The capsule is a composite particle consisting of a viscous liquid drop surrounded by a thin polymeric membrane. The method used to fabricate capsules suitable for macroscopic flow experiments is described. The deformation of the capsule is measured as a function of strain rate for an extensional flow generated in a four-roll mill. The data agree well with results from small-deformation theory developed by Barthes-Biesel and co-workers, provided the deformation of the capsule is not too large. Using the theory to correlate the experimental data produces an estimate for the elastic modulus of the membrane that agrees reasonably well with the elastic modulus obtained by an independent technique. However, for sufficiently large strain rates, the membrane exhibits strain hardening and a permanent change in its structure, both of which are reflected in the shape of the capsule.

An experimental study is reported of the motion, deformation, and breakup of a synthetic capsule that is freely suspended in Couette flow. The capsule is a liquid drop surrounded by a thin polymeric membrane. The shape and orientation of the capsule are measured in steady flow and following the start-up of Couette flow. Results are compared with predictions of the small-deformation theory of Barthes-Biesel and co-workers. The data suggest that the capsule membrane is viscoelastic, and comparisons with theory yield values of the membrane elastic modulus and the membrane viscosity. The values of the elastic modulus of the capsule membrane deduced from the flow data are compared with independent measurements for the same capsule.

When the flow-induced deformation becomes sufficiently large, the capsules break. Breakup begins at points on the membrane surface near the principal strain axis of the undisturbed flow. By examining the local deformation within the membrane, it is shown that breakup is correlated with local thinning of the membrane and is initiated at points where the thickness is a minimum.

In this paper we investigate the long-wavelength approximations of the equations governing the motion of an inviscid liquid jet. Using a formal perturbation expansion it will be shown that the one-dimensional equations presented by Lee (1974) are inconsistent. The inconsistency arises from the fact that terms which have been retained in the boundary conditions should have been rejected in view of the approximations made in the momentum equations. With the correct equations a number of anomalies between Lee's model and other models are eliminated. An explicit periodic solution to the nonlinear evolution equations we have derived is presented. However, it turns out that the wavenumbers for which this solution is valid lie outside the range in which the long-wavelength approximations are applicable. In addition we present numerical solutions to the nonlinear equations we have derived. In the unstable regime we find that, as disturbances grow, the characteristic axial lengthscales of the major features are typically of the order of the radius of the jet. This casts some doubt on the validity of the long-wavelength approximations in the study of nonlinear liquid jet dynamics.

Hot-wire anemometry has been used in the intermediate wake (x/d= 10 to 40) of a slightly heated circular cylinder in order to quantify the contribution from the coherent motion to various conventionally averaged quantities, in particular the average momentum and heat fluxes. The overall contribution to the lateral heat flux is always greater than that to the Reynolds shear stress, indicating that the turbulent Kármán vortex street transports heat more effectively than momentum. The difference in these contributions is reflected in the topologies of the velocity and temperature fields. There is significant streamwise evolution of these topologies throughout the intermediate wake. At x/d = 10, the net heat transport associated with the vortical motion occurs in the downstream region of each vortex. At other downstream stations, the net heat transport is equally distributed between the upstream and downstream regions of individual vortices.

The propagation of gravity fronts of high density ratios has been studied experimentally (exchange flow) and by computer simulation. Non-Boussinesq fronts are known to occur in certain safety problems (chemical spills and fires), and we have investigated seven gas combinations giving density ratios from near unity to well over 20. The results are presented in terms of a density parameter ρ* which remains finite both in the weak (ρ* = 0) and the strong (ρ* = 1) limit. The front velocities, measured by means of hot wires, are found to fall on two distinct curves, one for the slower lightgas fronts and one for the faster heavy-gas fronts. Two fractional depths, Φ = ½ (lock exchange) and Φ = ⅙, have been investigated in detail and results for the interesting case Φ → 0 have been obtained by extrapolation. To aid in the extrapolation and for comparison, all experimental (and some intermediate) cases have been simulated by means of a general purpose CFD-code (PHOENICS). Good agreement is found for cases without convergence problems, i.e. for heavy-gas fronts of density ratio less than 5. Further information on frontal shape etc. has been obtained from visualization. The extrapolations to infinite depth indicate a limiting speed for both the heavy- and light-gas fronts close to the values predicted from shallow-layer theory for the analogous dam-break problem.