Hydraulic slotting has become one of the most common technologies adopted to increase permeability in low permeability in coal field seams. There are many factors affecting the rock breaking effects of water jets, among which the impact force cannot be ignored. To study the influencing effects of contact surface shapes on jet flow patterns and impact force, this study carried out experiments involving water jet impingement planes and boreholes under different pressure conditions. The investigations included numerical simulations under solid boundary based on gas–liquid coupling models and indoor experiments under high-speed camera observations. The results indicated that when the water jets impinged on different contact surfaces, obvious reflection flow occurred, and the axial velocity had changed through three stages during the development process. Moreover, the shapes of the contact surfaces, along with the outlet pressure, were found to have impacts on the angles and velocities of the reflected flow. The relevant empirical formulas were summarized according to this study's simulation results. In addition, the flow patterns and shapes of the contact surfaces were observed to have influencing effects on the impact force. An impact force model was established in this study based on the empirical formula, and the model was verified using both the simulation and experimental results. It was confirmed that the proposed model could provide important references for the optimization of the technical parameters water jet systems, which could provide theoretical support for the further intelligent and efficient transformation of coal mine drilling water jet technology.

水力开槽已成为煤田低渗煤层增渗最常用的技术之一。影响水射流破岩效果的因素很多，其中冲击力不可忽视。为了研究接触面形状对射流流型和冲击力的影响，本研究在不同压力条件下进行了涉及水射流冲击面和钻孔的实验。研究包括基于气液耦合模型的固体边界下的数值模拟和高速相机观测下的室内实验。结果表明，当水射流撞击不同的接触面时，会发生明显的反射流，轴向速度在发展过程中经历了三个阶段的变化。此外，发现接触面的形状以及出口压力对反射流的角度和速度有影响。根据本研究的模拟结果总结出相关经验公式。此外，观察到接触表面的流动模式和形状对冲击力有影响。本研究基于经验公式建立了冲击力模型，并利用仿真和实验结果对模型进行了验证。证实该模型可为水射流系统技术参数优化提供重要参考，