An experimental study of the particle velocities in abrasive waterjets

An experimental study using particle image velocimetry (PIV) and laser induced fluorescence (LIF) techniques is presented to examine the particle flow characteristics inside the high velocity abrasive waterjet (AWJ) and assess the capability of this measurement technique. Although the particle velocity is found to increase with an increase in water pressure, the velocity of particles on the jet centreline decreases while that at the jet edge increases as the jet flows downstream within 40 mm distance from the nozzle exit considered in this study. It is also shown that particles rotate while moving downstream from the nozzle exit. While these particle flow characteristics may be anticipated from theoretical understanding, it confirms that the capability of this technique is not only able to measure the particle velocities, but also observe the particle trajectory in high velocity flows. The measured particle velocity data are then used to assess the applicability of a previously developed particle velocity model for low water pressures. It is found that the model can equally give adequate predictions of particles velocities in AWJ for relatively low water pressures of within 20 MPa.