LAUSR

Abstract The pulsive jet nozzle, which converts the continuous jet into a pulsive jet, is widely used in downhole well operations, such as drilling and perforation. In this paper, a self-excited oscillation pulsed jet nozzle is proposed basing on the Coanda effect. The effects of nozzle design, inlet flow rate, and target distance on the jet dynamics, such as the pulsive characteristics and impacting performance, were investigated. The transient flow pattern was studied with a high-speed camera, which showed a good agreement with the numerical results. Furthermore, with the increase of the inlet flow, the pulsation amplitude of impacting pressure of the Coanda nozzle increased. Based on the obtained data, the relationship between the pulsive frequency and Reynolds number and that between Strouhal number and Reynolds number was revealed. Under a confining pressure of 30 MPa, a target distance of 70 mm, and an inlet flow rate of 15 m/s, the error between the numerical impacting pressure and the experimental value was 9.7%, which confirmed the numerical approach could be used to predict the transient jet process. The obtained results can guide the design of a self-excited oscillation pulse jet nozzle and its oilfield application.