Dr Paul Hammerton (University of East Anglia) gives a maths colloquium at the School of Mathematics, UEA. The talk is on “Swinging cricket balls – why boundary layer transition is important”. The abstract is below.

This will be a talk in two parts — hopefully with something for everyone in the department. If a flat plate is placed in a high-speed wind tunnel, at some distance downstream of the leading edge the flow in the layer close to the plate can be observed to change in character from laminar flow (smooth flow almost parallel to the surface) to turbulent flow. The point at which transition occurs is quite sensitive to the particular wind-tunnel being used. This is known as the receptivity problem — the point of transition depends not only on the position of the point of neutral stability in the boundary layer, but on free-stream disturbances and how they interact with the surface. In the first part of the talk I will discuss the receptivity process, looking at how the shape and surface of a body can affect the level of receptivity. I will also discuss when transition is important be it drag reduction on plane wings or the importance in sport. The second part will focus more on the mathematical details. I will discuss work in progress, starting during my period of study leave. Looking at receptivity due to the leading edge of the body I will describe how understanding the eigenfunction decomposition of the solution in the boundary is important, and progress made in identifying these solutions.