Experimental and numerical investigation of the effects of flow and geometric parameters on circular hydraulic jump characteristics

The normal impingement of a liquid jet on a flat surface, the circular hydraulic jump (CHJ) is a classical free-surface flow phenomenon that is of great importance in cooling, coating, and cleaning up of surfaces. Although a lot of research has been conducted, the interactions between flow and geometric parameters and their effects on CHJ behavior are not well studied. The present study aims to experimentally and numerically establish the influence of the following significant parameters on the formation, stability and structure of circular hydraulic jumps: jet Reynolds number (Re), nozzle diameter, drop height, fluid viscosity, and impingement-zone geometry. ANSYS Fluent was used to simulate the dynamics of the transient two-phase flow and free-surface behavior of a custom-built experimental setup using stainless steel (SS304) nozzles of different diameters (2 mm to 12 mm) and variable drop height (up to 150 mm). The model was tested against known experimental and analytical findings and it was found to be in good agreement. The findings showed that the critical Re was about 14,000 between circular and non-circular jump regimes. The drop height was increased up to 40% in jump radius, and the viscosity decreased the jump radius 35%. Modifications of nozzle diameter and impingement zone had relatively small impacts. The research offers an in-depth insight into the hydrodynamics of CHJ formation and a proven numerical model of optimization of jet-based fluid systems in industry.