Theoretical and practical research on micro hydrodynamic nozzles for modulated water jet generation as an innovation to replace continuous water jet in soft materials erosion

•An innovative approach of generating a modulated water jet using a micro hydrodynamic nozzle is discussed.•The nozzle design, quality testing, flow visualisation, flow monitoring and functionality of the manufactured nozzle are presented.•The results of measurement are compared with the flow behaviour of the jet inside the nozzle.•The erosion properties of MWJs are investigated on the soft gelatine material using a developed method of high-speed recording and analysis. This study investigated the functionality of a newly developed micro hydrodynamic nozzle and its ability to generate a modulated water jet (MWJ) used for the erosion of soft materials. The procedure of nozzle design, numerical flow modelling, quality testing and functionality of the nozzle are presented. Well defined modulated jets were observed up to 1.5 MPa of input water pressure with an oscillation frequency of 88 kHz. Erosion characteristics of the modulated jets were investigated on soft gelatine samples. Three basic jet orientations were tested with respect to the eroded samples and to the trajectory of the nozzle movement. The erosion process of the MWJ was monitored using high-speed shadowgraph techniques. Then, the erosion depth was determined by image analysis methods. The test results show that the best erosion effect was obtained using the nozzle with 45° orientation with respect to the traverse direction.