The ionization relaxation and radiative cooling of weakly unsteady shock waves in krypton and xenon is examined. We find that, besides radiation energy loss, the shock-tube boundary layers and shock attenuation strongly influence the radiative-cooling region. Calculations taking these effects into account are in excellent agreement with experimental values of electron densities. The contribution of line radiation to total radiation energy loss is obtained, and amounts to about 54% at temperatures of 10 000 K in krypton. For xenon, first comparisons indicate a similar result.

A thermohaline diffusive interface at large density stability ratios has been studied experimentally. Several interesting characteristics have been found. First, using a transient experiment technique, a transition from boundary-layer to core-regiondominated transport has been observed. Secondly, interface growth can occur through a series of steps owing to a sharp transition to a region with large interface growth rates. Thirdly, hysteresis occurs within the large density stability ratio region. Finally, the property-transport flux ratio increases as an interface switches from boundary- to core-dominated transports.

A linearized potential-flow analysis is presented for predicting the unsteady airloads produced by the vibrations of turbomachinery blades operating at transonic Mach numbers. The unsteady aerodynamic model includes the effects of blade geometry, non-zero mean-pressure variation across the blade row, high-frequency blade motion, and shock motion within the framework of a linearized frequency-domain formulation. The unsteady equations are solved using an implicit least-squares finite-difference approximation which is applicable on arbitrary grids. A numerical solution for the entire unsteady flow field is determined by matching a solution determined on a rectilinear-type cascade mesh, which covers an extended blade-passage region, to a solution determined on a detailed polar-type local mesh, which covers and extends well beyond the supersonic region(s) adjacent to a blade surface. Results are presented for cascades of double-circular-arc and flat-plate blades to demonstrate the unsteady analysis and to partially illustrate the effects of blade geometry, inlet Mach number, blade-vibration frequency and shock motion on unsteady response.

The properties of solitary waves are investigated numerically using a series in sech2 ½x to describe the wave profile. (It is shown that this expansion is complete in the L2 sense.) Seventeen terms in the series are computed. For waves of amplitudes up to half the undisturbed fluid depth, the 17-term partial sum gives profiles and wave-parameter values with at least two-digit accuracy. For waves of larger amplitude, if Padé approximants are used to accelerate convergence, the computed values of the wave parameters are found to agree with the values obtained by Longuet-Higgins & Fenton (1974), but differ from those of Williams (1981), Witting (1981) and Hunter & Vanden-Broeck (1983). Possible explanations of this discrepancy are discussed.

This paper describes the results of experiments conducted on a circular jet simultaneously excited by two different acoustic tones. By varying the phase between two signals at harmonically related frequencies, control can be exercised on the process of harmonic generation – sometimes the process being virtually destroyed. This is shown to be so for both harmonic and subharmonic generation, but the latter is more difficult to control.

The stability of steady isothermal flow of one-dimensional Newtonian fibres is considered. Bifurcation theory yields a stable supercritical Hopf bifurcation, with frequency decreasing for increasing winder speeds near the critical winder speed. A new Chebyshev expansion procedure is used with time-marching to obtain accurate numerical solutions valid far from the critical point. Our numerical solution agrees well with our analytical solution near the critical winder speed, but differs significantly from those of previous numerical models. There is qualitative agreement with a previous isothermal experiment for oscillation amplitude but not for oscillation frequency. These comparisons are discussed.

A new two-parameter integral method is presented which is applicable to unsteady two-dimensional laminar boundary layers whether they are separated or not. The governing equations consist of three moments of the boundary-layer equation, and the assumed velocity profiles are those of unsteady trailing-edge flow and Falkner-Skan flow with slip. The governing equation system being hyperbolic, the spontaneous generation of a singularity associated with unsteady separation is confirmed as the focusing of characteristics. The obtained results of the boundary-layer quantities as well as the generation of separation singularity are in good agreement with those of exact methods (e.g. van Dommelen & Shen 1980) for starting flows of cylinders.