An apparatus to study drop-formed vortex rings

The construction of a novel apparatus to study the formation, evolution and decay of vortex rings created by liquid drops impacting upon a liquid pool is reported. Other phenomena related to drop impact such as the formation of air bubbles due to the collapse of the crater created by the impact can now also be studied in a controlled environment. The experiments are performed in a contaminant-free vapour-saturated environment. Temperature dependent fluid properties are controlled by a cooling/heating water bath circulated around a completely enclosed fluid reservoir. The experiment is fully automated through a computer interface to enhance reproducibility. Data are acquired using precisely timed 35 mm photographs lit by a strobe lamp.