Optimal submerged waterjet for gas recovery based on Arbitrary Lagrange‐Euler

Abstract This paper proposes a coupled model of waterjet cutting coal containing gas with the Arbitrary Lagrange‐Euler algorithm assistance. The dynamic evolution of coal damage and the cutting performance under different jet conditions, including jet pattern (submerged/nonsubmerged state), jet velocity, nozzle diameter, and the initial standoff distance, are investigated by tracing the number of failure elements and the stress distribution. Afterward, the gas flow model is built to study interactions of the discharged coal amount and the effective drainage radius at different periods with COMSOL software. The numerical results show the coal cutting performance of nonsubmerged jets is much better than that of submerged jets. Under submerged conditions, the penetration length increases with jet velocity and nozzle diameter, but decreases with the initial standoff distance. Moreover, the effective drainage radius of nonsubmerged waterjet is substantially greater than that of submerged jet. The increasing trend of the effective drainage radius slows down after 3 months with gas flow attenuation. Under the special submerged circumstances, the difference of coal cutting performance caused by the two jet patterns should be fully considered in order to reasonably arrange the spacing of boreholes.