A Phenomenological Study of Polygonal Hydraulic Jumps

Polygonal hydraulic jump is among the subjects widely studied by scientists in recent years. Although this phenomenon was discovered nearly two decades ago, many of the probable reasons behind it remain unknown. Accordingly, the main goal of the present study is to conduct a laboratory-scale phenomenological investigation on polygonal hydraulic jumps. The results indicated that the main cause of polygonal hydraulic jumps is the presence of disturbances and instabilities in flows, systems, or environments. Given the Plateau–Rayleigh instability, in the presence of surface tension and viscosity effects, the disturbances and instabilities create stable circular jumps unstable and then turn them into polygonal jumps. A stable circular jump was created with the elimination of instabilities, and the jump, unlike what observed in previous studies, was stable at a low to high range of Reynolds number. In addition, the behavior of polygonal hydraulic jumps formed in previous studies in the presence of instabilities was investigated. In a constant flow rate, the area inside the jump was equal for all the possible jumps at an error level of less than 10%. Among the polygons with an equal number of sides, which are possibly observed in a particular flow rate, the jump changes into a regular polygon, as the surface tension naturally tends to create the minimum possible surface area for the jump.