Experimental analysis of high-speed air–water jet flow in an abrasive water jet mixing tube

The paper analyses hydrodynamic characteristics of a high-speed two-phase flow in a mixing tube of a small-diameter. Different parameters including the water jet velocity and the ratio of diameters — the mixing tube to the water jet orifice — are investigated under two conditions of the air flow rates. Two measurements are used: the static pressure distribution along the mixing tube and the visualisation of the high-speed water jet at the tube inlet and its downstream outlet. The visualisation results show that the configuration of air–water jet flow starts annular near the tube inlet and then occupies the whole cross-section of the tube. Moreover, the pressure distribution results indicate the existence of three distinct-flow zones along the tube: an expansion zone with a high negative pressure gradient at the inlet; a practically constant pressure zone where the flow is nearly established in the middle, and an important recompression zone near the tube outlet. The paper demonstrates that the mixture of the air–water jet flow is not homogenous along the tube in the real behaviours. A schematic representation of the flow along the tube was introduced.