Dear Editor,
When a fluid and a solid body in it are moving relative to one another, a thin layer of fluid, called the ‘boundary layer’ by fluid mechanics, remains adhered to the surface of the solid. The thickness of the layer depends on the relative velocity of the motion and the natures of the fluid and the solid.
If the boundary layer of air on a swishing cricket bat interacts with the boundary layer of a moving cricket ball, there will be a sound, which will show up on a snickometer as a dispersion of lower frequencies. There will be no infra-red heat radiation to show up on a hot-spot camera.
Only if the moving cricket ball touches the bat will the friction of impact show up as a hot spot. In this case there will be a dispersion of higher frequencies from solid-solid contact of bat and ball, in addition to the lower frequencies of close air boundary layer contact.
The third umpire was therefore not sufficiently trained in the interpretation of the technology to give Kemar Roach not out.
Yours faithfully,
Alfred Bhulai
