Once again Steve Mould is putting his prototyping skills to use to work out what goes on inside tricky containers. Here he looks at a “magic” wizard’s cup where — like the assassin’s teapot — cleverly placed holes in the side of the cup can block or allow air’s escape. In the wizard’s cup this lets the wizard refill the cup at will.
He also takes a look at how draining works, using tracer particles and a video editing effect that “echoes” previous frames in a video. For the tracer particles, this algorithm effectively visualizes pathlines in the flow. Areas with faster-moving fluid have longer pathlines that are closer together, whereas slow-moving regions have short pathlines. (Video credit: S. Mould)