Supersonic needle-jet generation with single cavitation bubbles

Abstract

Collapsing cavitation bubbles produce intense microscopic flows. Here, in an aqueous environment, we seed single laser-induced bubbles (diameter about one millimeter) in proximity to a solid surface, in a regime that has not been well explored before in order to generate a “needle jet.” The needle jet propagates at supersonic speed through the gas phase toward the solid. It reaches average velocities of more than 850 ms−1 and thus is an order of magnitude faster than the regular jets that have frequently been observed in cavitation bubbles. The dynamics leading to the needle jet formation are studied with high speed imaging at five million frames per second with femtosecond illumination. This highly repeatable, localized flow phenomenon may be exploited for injection purposes or material processing, and it is expected to generate significantly larger water hammer pressures and may also play a role in cavitation erosion and peening.

The Rayleigh prolongation factor at small bubble to wall stand-off distances

“…The flows associated with the kinks can become so dominant for smallest γ that they converge and collide at the axis of symmetry even before the regular jet from the apex passes the respective point on the axis. Then a supersonic needle jet is formed in the direction towards the boundary (Lechner et al 2019(Lechner et al , 2020Reuter & Ohl 2021).…”

“…The significant regime for cavitation material interaction can be considered to be in the range γ < 4, where the long-ranging vortex ring still reaches the boundary (Reuter, Cairós & Mettin 2016), but for smaller stand-offs, the interaction with the boundary tends to be more intense. Recently, for closest distances to a solid boundary (γ <≈ 0.2), a needle jet with an impact velocity of over 900 m s −1 was predicted numerically (Lechner et al 2019) and found experimentally (Reuter & Ohl 2021). This particular small-distance regime is exploited for the production of nanoparticles by laser ablation in liquids in combination with cavitation bubbles (Barcikowski et al 2019).…”

“…Recently, for closest distances to a solid boundary (), a needle jet with an impact velocity of over was predicted numerically (Lechner et al. 2019) and found experimentally (Reuter & Ohl 2021). This particular small-distance regime is exploited for the production of nanoparticles by laser ablation in liquids in combination with cavitation bubbles (Barcikowski et al.…”

Singular jets in compound drop impact

“…These singular dynamics produce very thin and fast geometries evolving in a self-similar way from larger boundaries to the smallest scales, such as for bubble or drop pinch-off [51][52][53][54][55][56][57] and coalescence [58,59] for instance. The formation of singular jets has been observed previously in many configurations, such as the collapse of Faraday waves [44,[60][61][62][63], cavitation bubbles [64][65][66], collapsing cavities [67], drop impact on a solid surface [24,[26][27][28][29][30][31], drop impact on a liquid pool [46-48, 68, 69], solid impact on a pool [70][71][72], and bubble bursting at a free surface [45,69,[73][74][75][76][77][78][79][80][81][82]. However, only few studies have observed such singular jets in interfacial flows with multiple immiscible liquids [18,48,83].…”

Experimental and Analytical Study of under Water Pressure Wave Induced by the Implosion of a Bubble Generated by Focused Laser

“…The conventional submerged shock wave sensors, like crystal and quartz base sensors, have a lower frequency band (some ); therefore, the PVDF sensor is more suitable for impact measurement. In a recent study by Reuter and Ohl [ 37 ], a 5 million frame per second high-speed imaging system with femtosecond illumination technology proved that the collapse of bubble close to a rigid boundary may transform into a micrometer-sized, supersonic needle jet. This needle jet will produce a higher pressure than classic micro-jets.…”