Two years ago the Waltons visited Bath – and Bath Uni specifically – in support of my son, who was contemplating an application to the Department of Mechanical Engineering. As well as being wowed by the L, L, L, and indeed the F, F, F (Facilities, come o-on, keep up), a particular one of us was more than mildly diverted by a particular chance-occurrence. Or was it fate?
(By the way, it’s cool to call it ‘Uni’, right?)
Following an encouragingly cosmopolitan, reasonably well-healed crowd into the relevant building, we encountered the usual signage, plus material delivering to the departmental sales-pitch. A formula-something racing car, in the foyer; a video twinkling out sexy-but-profound Things You Should Know But Probably Didn’t, About Bath Engineering and a clutch of posters in a rack, speaking of specific research undertaken in the gaff.
The first of these posters was winking at me alone.
It may not, actually, have been called The Science of Swing but clearly it should have been. It was the story of one particular student’s release into the mysterious world of hooping cherries; some hows and whys of bowling swing – swing measured and experimented-upon in wind-tunnels and stuff. Proper, academic swing. Shockingly, I departed from family duties at that moment.
That project was written by a youthful James Scobie, the same James Scobie who triumphantly wheeled away to the Bath Uni Mech. Eng. staff room, where he still sits: that poster said as much.
Clouseau-like, I eventually discovered that the Dr Scobie was, on the day of our visit, “in the main sports hall, doing the student-welcome effort”. I went, and finding a gap in the worryingly-rehearsed but no doubt sincere questions from young hopefuls, began a conversation about balls. Later, graciously, James sent me his original research and our contact persisted, somewhat.
Two years pass and whilst delivering our newly-enrolled son into his room on the campus, I re-meet Dr Scobie, as arranged, for a further delve into the science and as it transpires, the poetry around the subject. The result is Podcast 4, for the Universe Podcast, which I present below.
It’s a rather magnificent 20-minute ramble through Laminar Flow, Turbulent Flow and dimples, on golf balls. Meaning there is science, but not of the deathly dry variety, I trust.
I strongly recommend it – the Dr is well worth listening to. The bloke who says WAGGA, instead of WACA (I think because he was raw excited and thinking of the GABBA) maybe less so.
I’m adding some thoughts and reflections because they may contribute to the understanding – maybe. Bullet-pointing, because a) speed b) there’s that feeling we bolted through many complex things and my head remains excited. To the extent that I will revisit this and re-claim some form of intelligent conclusion, in time.
- It’s not about the humidity, folks!
- It *may be* partly about the relative stillness that grey/cloudy/humid conditions deliver above the pitch. During ‘classically good bowling conditions’ at (e.g.) Trent Bridge in September, there may be an atmospheric stillness which enables the necessary Fluid Dynamics.
- Conventional Swing is about the difference in two types of air flow… and about new balls and Boundary Layers around them.
- The Duke’s ball swings (conventionally) when skilfully steered, when it’s newish, when the surfaces are in a condition that supports ‘hooping’.
- The Duke’s ball is a ‘fabulous product’ with no unhelpful groove or slot between the four pieces of leather that make up the two hemispheres. The ‘fast’ or polished side can, therefore, be slick and quick – supporting swing.
- The Kookaburra ball has a noticeable groove, which may negatively affect the possibility for swing.
- *Also*, in Australia/India where there is often significant heat, turbulences above the pitch may interrupt or reduce the possibility for swing. James Scobie/Bath Uni conducted an experiment to try to replicate this WACA-esque phenomenon, using a grid to complicate air flow.
- Wind tunnels are not 30 yards long. They are room-sized bits of kit in which the chamber may be the size of a suitcase, or tea-chest. The ball is fixed in position and air propelled across it to reproduce events. But the science is still valid.
- Reverse swing is a function of speed and/or deterioration in ball condition.
- Sandpaper can accelerate or make possible Reverse Swing.
- Sugary spit can artificially maintain or improve the surface condition of the ball – and therefore promote swing.
- Both sandpaper and sugary spit are ver-ry naughty.
Important: lots of chat arising about humidity and a perceived contradiction in the Scobie argument regarding the influence of muggy conditions. To be clear, Dr S conducted experiments where humidity was increased incrementally (and measured) in the wind tunnels. These showed clearly, in his view, that humidity specifically – the presence of water in the air – played no role in the production of swing.
Extracts, here, from a further explanation from Dr Scobie.
’humidity in isolation has no effect…
What we are arguing is than in order to cause the ball to swing you need the asymemetry set up by laminar flow on one side of the ball and turbulent flow on the other. If the environment is not conducive to this then swing will not occur’.
Encouragingly and for me more than slightly wonderfully, it is scientific fact (of a sort) that some of this remains… a mystery.