Aggressive ability improvement of self-resonating cavitating jets with double-hole nozzle

The aggressive ability of cavitating jets generated by a double-hole nozzle was investigated under an ambient pressure condition to improve the erosion efficiency for potential applications such as underground drilling. The erosion damage was experimentally investigated for a series of pitch–hole ratios to understand the erosion mechanism of the double-hole cavitating jets. The flow characteristics of various erosion patterns were numerically investigated using two-phase computational fluid dynamics (CFD) calculations. The stages of erosion suppression in the pitch–hole ratio range wp ∈ [1.25, 3] and erosion enhancement in wp ∈ [3.5, 6] were observed based on the mass loss Δm across the entire range of standoff distance ratio ls. Two erosion patterns were identified according to the erosion features, designated as A and B, with increasing standoff distance ratio ls. Erosion occurs in multiple scattered regions in pattern A and which appears as two symmetric D-shaped regions in pattern B. In contrast to the single-hole jet, the aggressive ability was significantly improved a wp = 4.5 with higher Δm peaks. Double-hole cavitating jets at the optimum pitch–hole ratio achieve the highest streamwise velocity and the weakest interaction between the two jets. The cavitation clouds in the impinging jets generated by the optimum pitch–hole nozzle primarily collapse in the D-shaped main erosion region, which enhances the erosion damage of the double-hole cavitating jets at the optimum standoff distance ratios.