(400b) Dynamics of a Compound Droplet in a Vertical Channel Under Pulsatile Flow

Compound droplet in pulsatile flow find diverse applications, including precise drug delivery in biomedical engineering, efficient mixing in microfluidic devices, controlled cell manipulation in biotechnology, and advanced material synthesis in material science and industrial processes. Their dynamic behaviour under pulsatile flow conditions enables tailored solutions for a wide range of applications, spanning from healthcare to manufacturing industries. In this regard, a comprehensive study of compound droplet behaviour under pulsatile flow condition is performed through numerical simulations. An Inhouse solver based on Level Set Method was developed in 2D vertical domain. The compound droplet was then simulated considering multiple influencing factors including Strouhal number (St), Reynolds number (Re), Weber number (We), ratio of core to outer fluid density (ρ_core), shell to outer fluid density (ρ_shell) and viscosities (µ_core and µ_shell) respectively.

One of the key findings is the influence of Strouhal number on the dynamics of the compound droplet. Strouhal number indicates the ratio of viscous time scale to the time scale due to oscillatory pressure gradient. At a Strouhal number, St = 0.05, the oscillatory component dominates viscous effects and the amplitude of oscillations in the droplet velocity (Vs) is much higher compared to that at St = 10 (Fig 1 (a)) . Further, Fig 1(b) represents the droplet position as a function of St at t = 30. This reveals a faster droplet motion at St = 0.05 compared to that at 10.

Overall, these comprehensive insights provide valuable understanding for optimizing compound droplet-based systems in diverse applications. The compound droplet dynamics under pulsatile flow in vertical channel with detailed parametric studies have been performed for the first time through this work.