"Drifting cups on a meandering stream" in China

"Drifting cups on a meandering stream" is a game originating from the ancie nt China. It takes advantage of the stopover of the cup at the different po sitions on a meandering stream to choose a person sitting on the bank to pa rticipate the game. In this paper, a model is devised to make the cups move around or stop at some place on the stream as required by the game. A typi cal flow field is abstracted and studied using the PIV technique and the to pological analysis. Some motions of the cup on the stream have been explain ed in the mechanics theory.