Whistling kettle at Wray Castle

We took our new whistling kettle to the amazing mock-gothic Wray Castle near Ambleside. I hadn't realised that explaining this type of steam whistle had been such a problem. Here's some new research from Cambridge University http://www.cam.ac.uk/research/news/how-the-kettle-got-its-whistle Basically the whistle is made of two parallel plates of metal with a small hole through the whole thing. The first hole is  a lot narrower than the spout and forces the stream into a jet. This loses some of its compactness as it moves into the space between the plates. When it reaches the second hole, these form into small vortices - like the eddies on the river mentioned two weeks ago - and it is this that gives the whistle. But researchers noted a second mechanism that it like blowing over the top of  an empty bottle.