Investigation of Droplet Behaviour Under the Influence of an Oblique Impinging Jet

Liquid droplets residing on a solid substrate unpin when the external gas-phase flow reaches a critical velocity. Previous studies have focused on a droplet subjected to a steady flow (e.g., Schmucker et al., 2017APS..DFDQ11006W). The present investigation considers droplet behaviour under the influence of a starting slot impinging jet. Single droplets of distilled water are subjected to a two-dimensional slot jet which is accelerated at three different rates, dU_j /dt= 1.2, 2.2 and 4.4 m/s². The tests are performed for water droplets at four different volumes, V = 20, 35, 50, and 65 µL located 2, 4 and 7 slot widths downstream of the impingement point. The results indicate that in the immediate vicinity of the impingement region, the critical velocity shows minor sensitivity to droplet volume and jet ramp rate. However, the influence of these parameters becomes more significant when droplets are located further downstream from the impingement region. The observed trends are related to characteristics of the quasi-steady flow fields assessed with particle image velocimetry.