Laminar and Turbulent Flow on the way to the head of Hope Gill

 

Near the head of Hope Gill (Clue: think Hopegill Head!) we foud this rock. The flow across it is mostly laminar. You can tell because the water is transparent. But there was a tiny section circled where the flow went turbulent on that top surface. It then goes turbulent off the edge as it speeds up and will increase the Reynold's number. A slight variation on the surface of the stone must be causing that to happen.