Mode-switching in the flow of water into a cup

Mode-switching was investigated when water was poured into a cup. Three modes, i.e., accumulation flow (Mode I), scattering flow (Mode II), and oscillatory flow (Mode III), were regulated by the flow rate. The bifurcation flow rate at Mode I→II was different from that at Mode II→I, i.e., hysteresis in mode-switching was observed. Mode III was observed at Mode I → II. The bifurcation point changed depending on the radius of the water tube, and the water-hollow was an important factor in mode-switching. The mode-switching was reproduced by a numerical calculation including the double-minimum profile of the free energy and the flow rate.