Simulation of thermal stress effects in submerged continuous water jets on the optimal standoff distance during rock breaking

- The thermal effect on the rock breaking of water jets is researched by a fluid-solid-heat coupling model.
- The effect of thermal stresses is the main reason that the optimal standoff distance of jet erosion exists.
- The effect of thermal stresses in jet erosion is validated by comparison with the former experiments.

Although many hypotheses of rock breaking of water jets have been proposed, effects of thermal stresses on the jet-based rock breaking hasn't been systematically analyzed yet. A fluid-solid coupling analysis module in ANSYS was employed in the article to reveal the effects of thermal stresses on the water-jet rock breaking and prove the existence of the optimal standoff distance. It is found that the trend of the temperature is in accordance with the existence of the optimal standoff distance. The coupling effect of the temperature and pressure fields can enlarge the breaking area of water jets. The effects of thermal stresses on soft rock with the low elastic modulus are minor, and no optimal value exists, with regard to the standoff distance. Nevertheless, as for hard rock such as granite, the optimal standoff distance is about ten times the nozzle diameter and the value will decrease with the increase of jet time. The findings of this research can offer a novel research starting point and method for the effective application of high-pressure water jets to cut metal and rock.

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