Formation of downward Marangoni jet after ethanol droplet impact on water surface

When an ethanol droplet is released onto a quiescent water surface, immediately after the collision, the droplet penetrates the water and extends downwards before contracting. During the contraction phase, fresh water rises, forming a ring of ethanol on the water surface. Within this ring, the Marangoni convection occurs, resulting in the generation of downward ethanol jet. We experimentally investigated the conditions required for the generation of the jets. A glass container is filled with 500mL of ion-exchanged water. To visualize the jets, fluorescein dye (uranin) is dissolved in anhydrous ethanol. Ethanol droplets are generated and dropped into the container using a syringe pump connected to an injector with stainless steel pipes. Three types of stainless steel pipes with diameters of d=1.5mm, 2.5mm, and 3.5mm are used. The flow behavior of the ethanol droplets beneath the water surface is captured using a high-speed camera. In this work, we will show the dropping height from the liquid surface can significantly affect the generation of the jets.