Abstract

Improving the efficiency of modern transport aircraft continues to be an active area of research. Although the current design solution has now reached a high level of maturity, there are potential developments afoot that may force engineers to re-think the shape of the wings.

The most significant development is the possible introduction of ‘laminar flow wings’. These have a subtly altered shape to promote a greater extent of ‘laminar flow’ (as opposed to turbulent flow which covers more than 90% of current wings). Laminar flow has a lower skin friction drag and this therefore has the potential to reduce aircraft drag considerably. However, the different shaping of the wing cross-section (the aerofoil) is likely to lead to the increase of another, more obscure, drag component: wave drag.

In this lecture I will begin by re-visiting how lift is generated by aerofoils (hopefully getting rid of some misconceptions) and why, in modern transonic aircraft, this leads to the generation of shock waves – the cause of wave drag.

Finding flow control devices that can alleviate the adverse effects of shock waves on wings has been an actively researched across the world for several decades. Lately, much work has focused on the three-dimensional ‘shock control bump’ which was first tested here in Cambridge more than a decade ago.