A “dual-time” method for solving the three-dimensional Euler equations describing the compressible flow about wings undergoing arbitrary motions and deformations is presented. A finite-volume formulation is chosen where the volumes distort as the wing moves or deforms. Independent motion of the inner and outer boundaries of the grid is permitted with a sequence of grids generated using transfinite interpolation.

An implicit real-time discretisation is used, and the equations are integrated in a fictitious pseudo time. This approach allows the real-time step to be chosen on the basis of accuracy rather than stability. It also permits the acceleration techniques commonly used to speed up steady flow calculations to be used when marching in pseudo time, without compromising real-time accuracy. A two-dimensional version of the method has also been developed and results for both two and three-dimensional transonic flows are presented and compared with experimental data where available.

This paper describes the development of a simple theory of the longitudinal static stability of the hang-glider. The classical theory, as developed for the conventional aeroplane, is modified to accommodate the particular features of the hang-glider. When the appropriate assumptions are made, the theory provides simple insight into the controls fixed and controls free stability and control characteristics of the hang-glider. The validity of the theoretical models is successfully demonstrated by application to a typical fifth generation hang-glider wing for which good quality aerodynamic data were available.

The circular cross-sectional Royal Aerospace Establishment (RAE) 2129 S-shaped intake diffusing duct series, shown in Fig. 1, which has an offset of the inlet and exit centerline of 0·3 and 0·45 of the axial length of the duct, was designed at the RAE (Bedford) and tested at British Aerospace Filton, at low forward speeds (freestream Mach no. range from 0 – 0·2 but a range of duct inlet Mach numbers up to choking speeds) in the last two decades to fulfil the objectives of collecting systematic experimental data on engine face pressure recovery, total pressure flow distortion and wall static pressures for computational fluid dynamics validation. Some of the measurements have been presented, as for example, by Willmer, Brown & Goldsmith. The measurements from one version of Model 2129 (the 0·3 length offset S-duct geometry) have been used to compare with calculated results from a number of CFD programs, as for example, by Anderson, Horton and by the AGARD Working Group 13. The series of comparison also highlight the need for measurements other than the engine face total pressure and wall static pressure which have already been made.

The three-dimensional vortex/boundary layer interaction of a type which may occur on a high-lift aerofoil has been studied. The experimental configuration simulates the trailing vortex system generated by two differentially-deflected slats which interact with an otherwise two-dimensional boundary layer developed on the wing surface under a nominal zero pressure gradient. The mean and turbulent flowfields are measured by a triple hot-wire system. The measurements show that the trailing vortex system includes the vortex sheets shed from the slats and the single vortex formed at the discontinuity between them. The single vortex moves sideways and interacts with the boundary layer as it develops downstream. During the interaction with the boundary layer, the low momentum, high turbulent-kinetic energy flow carrying negative longitudinal vorticity is entrained from the boundary layer and rolled into the vortex at the line of lateral convergence on the test surface. Likewise, at the line of lateral divergence, the high momentum, low turbulent kinetic energy flow carried by the vortex impinges on the boundary layer, suppressing the turbulent energy level and the growth of the boundary layer.

The aerodynamic condition corresponding to the optimum sail trim has been long debated; in the present note this aerodynamic aspect of the sails is studied by means of pressure measurements near the sail leading-edge. By analysing the pressure acting on the leading edge zone it can be evidenced that, when the sail is “optimally” trimmed, it is actually in the aerodynamic condition corresponding to the ideal angle of attack.