A review is given of some recent research, mainly at low speeds, into the development of dynamic lift. Sudden movement of aerodynamic surfaces can generate dynamic lift due to the transient development of separated flow. These dynamic effects are large and well established for aerofoils. They are considered likely to be small for highly swept wings and negligible for slender wings, but there is little experimental evidence to support this inference. The dynamic lift might be increased if conventional sinusoidal motions can be replaced by appropriate periodic saw-tooth motions.

The control of large-scale flow separations by rapid movements of aerodynamic surfaces requires further investigation to resolve some of the controversial issues raised in the review.

An interactive computer programme, based on linear-elastic laminated plate theory, is used to study the effect of lay-up geometry on first ply failure loads. A maximum allowable strain failure criterion is used and a number of design problems are considered where searches are made for optimum lay-up configurations for typical carbon fibre reinforced plastic properties. The relative weakness of this material in tension across the fibres, is found to have a significant effect on first ply failure loads. An optimisation technique based on principal load directions is introduced and compared with the familiar 0/90/±45 lay-up configuration.

The aerodynamic characteristics of two-dimensional transient aerofoil motions in low-speed flows in a wind tunnel with either closed wall or open (jet) walls, including the effect of a downstream closed wall diffuser, have been investigated. The mathematical formulation for the aerofoil and its unsteady wake is based on linear theory and is solved by a piecewise linear vorticity method; the wall boundaries are represented by distributions of sources. Numerical calculations have been made for various values of tunnel height to chord ratio.

Interference effects on the rate of build up of lift to a steady state following a step change in incidence can be large, especially for open jet tunnels.