Study on the influence of contact surface curvature on water jet impingement flow field and initial damage of coal seam

Abstract

Abstract The design of the contact surface has a big impact on how well water jets penetrate coal rock. The influence of water jets on contact surfaces with various curvatures is studied using numerical modeling to elucidate the flow field and coal seam damage characteristics. The water jet impingement flow field region can be separated into three areas: velocity concentration, divergent flow, and wall recirculation. As the jet water pressure rises, the flow field's distribution features become more apparent. Water jet impact morphology and flow field properties on contact surfaces of various curvatures are comparable. The peak velocity ratio of the wall and axis falls first, then increase as the curvature radius ratio (n) of the contact surface increases. Near n = 0.8, the peak velocity ratio of the wall and axis reaches a minimum, indicating that the kinetic energy loss in the process of water jet impact to the contact surface is the greatest. When water jets of various pressures impact the contact surface, the peak velocity drops by two‐thirds before and after impact, and nearly 89% of the kinetic energy is lost in the impact process. The range of the initial damage and failure area in the center of the contact surface and the initial damage and failure area on both sides of the wall caused by water jet impact decreases gradually as n increases. When n = 2, the initial damage and failure region on both sides of the wall has virtually vanished; when n = 0.2. The contact surface's center failure depth induced by water jet impact is the deepest. The initial injury is unaffected by changes in jet water pressure.

Keywords

• damage structure
• flow field characteristics
• initial damage
• interface
• water jet