Air-assisted pure water jet orifice: a preliminary numerical analysis

Water jet cutting has always been a promising technology because of its extreme simplicity and flexibility, even if it often suffers a lack of control on its process parameters, especially if compared to technologies such as laser cutting or electro-discharge machining. Recent studies have showed how the presence of water inside the orifice causes disturbances which systematically affect the jet structure, both during the jet formation and the cutting process. These disturbances can be neglected in industrial applications, but can play a relevant role in case of high-precision water jet machining. The aim of the present work is to investigate on a possible solution to this problem through a modification of the orifice inner geometry, thus allowing the controlled intake of air inside the orifice, with the aim of modifying the air flow field preventing the jet from the previous mentioned disturbances and finally enhancing the process stability. A preliminary analysis is carried out by means of CFD simulations in order to test the proposed solution and its effectiveness. The fluid dynamics aspects of the outflow process are investigated by means of a 3D numerical simulation with Ansys Fluent CFD solver, while considerable experimental efforts are provided in order to validate the numerical model and finally to evaluate the system performances.