Edgerton, using his strobe-flash photography technique. High-speed imaging was pioneered by scientists like Harold E. Since the dynamics of the aforementioned events take place in a few milliseconds, high-speed imaging is required to observe the phenomena. In this case, the jets travelling at speeds of ≈20 m s −1 generate a cavity circumscribed by the droplet volume and the hydrostatic pressure can be neglected.
8,9 In this paper we study for the first time the impact of micrometer-sized jets (≈100 μm) on a self-contained liquid object, namely droplets of ≈2 mm. 2 In contrast, we found just two works discussing the impact of projectiles in the submillimeter range.
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2–7 In these cases, hydrostatic pressure has been found to be a major driver for the collapse and retraction of the cavity made on the liquid pool. 2–7 The projectiles studied in the literature usually have sizes in the range of 1 to 5 mm, an impact speed range of 1 to 10 m s −1, and the pool is usually orders of magnitude larger than the projectile and the created cavity. 1 Since then, research has focused on many topics, including the critical energy necessary for air entrainment into a pool, the collapse of the formed cavity, and the subsequent formation of Worthington jets. 1 Introduction The impact of a solid or liquid object into a deep liquid pool generates a cavity with dynamics first described by Worthington in 1908. Our results increase the knowledge of the jet interaction with materials of well-known physical properties. In addition, we assess how surfactants and viscoelastic effects influence the critical impact velocity.
We contrast the model predictions against experiments, in which we vary the liquid properties of the pendant droplet and find good agreement. We predict the critical traversing velocity (i) from a simple energy balance and (ii) by comparing the Young–Laplace and dynamic pressures in the cavity that is created during the impact. Upon impact, an expanding cavity is created, and, above a critical impact velocity, the jet traverses the entire droplet. Here, we study the impact and traversing of such jets on a pendant liquid droplet. High speed microfluidic jets can be generated by a thermocavitation process: from the evaporation of the liquid inside a microfluidic channel, a rapidly expanding bubble is formed and generates a jet through a flow focusing effect.
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