Enhancing and visualising mixing between impacting droplets

Abstract

Droplet impacts onto finite-depth liquid layers can be seen throughout industry and nature, from raindrops impinging onto puddles to pesticide sprays coating plants. We present an integrated high-speed imaging and numerical investigation of droplets impacting perpendicularly onto finite-depth pools and thin films, elucidating the post-impact dynamics and secondary droplet formation in this regime. In particular, we explore the rich behaviour and transitions that arise when varying the pool depth and liquid fluid properties, from inherently 3D-effects including ‘crown collapse’, to variations in the generation of an axisymmetric Worthington jet. The complementary strengths of experiments and numerical simulation are exploited throughout in order to constructively explore the physical mechanisms underpinning the exciting dynamics observed.

Acknowledgements

Supported by NSF/CBET-EPSRC (Grant Nos. EP/W016036/1 and EP/S029966/1); EPSRC (EP/L01615X/1 and EP/S022732/1); Royal Society URF (Grant No. URF\R\180016) & Enhancement Award (Grant No. RGF\EA\181002); UK Fluids Network