Numerical Investigation of Polygonal Hydraulic Jump Formation Mechanism and its Flow Structure

This article contains a numerical simulation of polygonal hydraulic jump using the volume-of-fluid (VOF) method. This phenomenon occurs when a circular jet of a high viscous liquid impinges perpendicularly onto a flat surface. In fact, when a liquid jet hits a surface, a circular hydraulic jump appears around the stagnation point. In a fluid with low viscosity (such as water), the shape of this jump is circular and in a high viscosity fluid (e.g., ethylene glycol), a polygonal structure forms. This structure is due to the presence of mechanical waves around the collision area, which is considered in the numerical method. In this paper, the results of the numerical model are validated with available experimental studies for the shape and structure of the generated hydraulic jump and its radius. Finally, based on numerical results, it is observed that a circular hydraulic jump spreads at the beginning, and after its corresponding wave collides with downstream obstacles, a polygonal shape is gradually formed and stabilized. In addition, the streamlines show that the existing of high-speed flows in some points of the solution domain generates corners in the jump shape leading to the formation of a polygonal hydraulic jump.