When I look back over the list of those who have given each of the previous 36 Roy Chadwick lectures since their inception in 1956, I observe a number of interesting features. The list includes some of the most illustrious names that have contributed to the pioneering and maturing phases of the design and development of gas-turbine powered flying machines. I was fortunate to have worked for and been in contact with — not to say under the lash of — at least two of them: Sir Stanley Hooker and John Coplin.

The effect of camber on the aerodynamic characteristics of an infinitely thin aerofoil approaching the ground is studied using a numerical model that accounts for the unsteady nature of the flow. The wake is computed as a part of the solution and the image technique is used to account for ground effects. The results indicate that relative deviations of lift and moment coefficients, from corresponding values far from ground, decrease as the camber ratio or angle of attack increases. Moving the location of maximum camber backward has a similar effect. Meanlines of NACA 4-digit series showed smaller deviations compared to NACA 6-digit series meanlines. Increasing camber ratio or moving maximum camber backward causes the wake trajectory to be lower. The steady ground-effect approach is inaccurate and may give erroneous results for plates with high camber ratios at small angles of attack, especially near the ground.

The paper reports the first computational explorations of the flow in the vicinity of riblets with a two-equation turbulence model. For simplicity fully developed flow in a plane channel is considered though the results should be applicable to boundary-layer flow, as the riblets are confined within the (virtually) constantstress near-wall sublayer. The study of idealised L-shaped (or blade) riblets showed larger levels of drag reduction (up to 22%) than have hitherto been reported. When the usual triangular-profile riblets were considered, however, the maximum drag reduction was reduced to about 10%, in line with experiment.

Although the maximum drag reduction is well predicted, there are serious differences from experiment for the values of h+ at which the optimum performance is achieved. Moreover, the computations suggest that at low Re for h+ < 10, drag increases result. These anomalies highlight two distinct and counteracting weaknesses in the model of turbulence: there is an insufficient sensitivity of the equation to three-dimensional straining in the jow-Reynolds-number region while use of an isotropic viscosity model enforces zero secondary circulation in the vicinity of the riblets.

The dynamic stability of blunt cones at angles of attack and high supersonic Mach numbers has been investigated along lines similar to the pointed cone solution derived by the present author. The steady pressure distribution on a blunt cone is complemented with a first and second order azimuth contribution resulting from an angle of. attack displacement. The unsteady perturbation is then superimposed on the steady solution by accounting for the streamline deflection in an oscillating flow. The closed form expressions obtained for the dynamic stability of blunt cones reduce to their pointed cone counterparts once the bluntness parameter is equated to zero. The comparison between the theoretical and measured results is quite encouraging.