I decided to do a more in depth post about Alnwick Castle’s Serpent Garden. Laid out in gently curving spirals the Serpent Garden is a series of linked circular chambers walled by trees.
Most of the chambers have a fountain inside them, but these are no ordinary fountains. Designed by William Pye each one harnesses a particular scientific principle to produce a dazzling effect, with plaques written in plain English explaining on a child friendly level how each one works.
We have the Coanda
Where the air flow causes the water to flow along the curved underside of the fountain instead of just dripping straight down.
Which demonstrates roll wave, the patterns caused by surface tension in the water as it flows down a curved surface. You’re invited to walk between the two pillars.
Its hard to tell from this photograph because of the detritus in the pool but this demonstrates both roll wave on the hemisphere and the optical illusion created by reflection that makes it seem like a full sphere. There’s a link to a better image on his website here.
The water level rises and falls in this one. The movement of the water causes more and more of it to spill over the side and, as the water level goes down, the surface goes from being level to a violent wave motion. When its almost empty water is pumped in from the bottom, producing circular-spiraling waves until it fills up again and returns to the mostly level state. The whirlpool in the centre is an air vortex, like that produced in the drain of a sink.
Working through hydrostatic pressure, a pool on higher ground overflows and travels underground to fill up the clear pipes of this fountain. When the level in the pipes reaches that of the pool the water pressure opens another gate, pushing the water out through the jets arranged in a circle around the fountain base. When the pipes have emptied the gate closes and they start to refill.
The water falls in a sheet and flutters at the bottom because of differences in air pressure on either side of it. You can also go down inside it where the acoustics distort your voice in a way that can’t be heard by people standing outside.
The water droplets are sprayed up to the centre of the glass where the surface tension lets them cling as they move further towards the edge.
The surface tension coupled with the direction the water flows in creates a slight dome over the top of the fountain.