Browsing by Author "van der Meer, Devaraj"
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Item Giant Bubble Pinch-Off(Physical Review Letters, 4/21/2006) Bergmann, Raymond; van der Meer, Devaraj; Stijnman, Mark; Sandtke, Marijn; Prosperetti, Andrea; Lohse, DetlefSelf-similarity has been the paradigmatic picture for the pinch-off of a drop. Here we will show through high-speed imaging and boundary integral simulations that the inverse problem, the pinch-off of an air bubble in water, is not self-similar in a strict sense: A disk is quickly pulled through a water surface, leading to a giant, cylindrical void which after collapse creates an upward and a downward jet. Only in the limiting case of large Froude numbers does the purely inertial scaling h(?log h)1/4??1/2 for the neck radius h [J.?M. Gordillo et al., Phys. Rev. Lett. 95, 194501 (2005)] become visible. For any finite Froude number the collapse is slower, and a second length scale, the curvature of the void, comes into play. Both length scales are found to exhibit power-law scaling in time, but with different exponents depending on the Froude number, signaling the nonuniversality of the bubble pinch-off.Item Growing bubbles in a slightly supersaturated liquid solution(Review of Scientific Instruments, 6/26/2013) Enríquez, Oscar R.; Hummelink, Christian; Bruggert, Gert-Wim; Lohse, Detlef; Prosperetti, Andrea; van der Meer, Devaraj; Sun, ChaoWe have designed and constructed an experimental system to study gas bubble growth in slightly supersaturated liquids. This is achieved by working with carbon dioxide dissolved in water, pressurized at a maximum of 1MPa and applying a small pressure drop from saturation conditions. Bubbles grow from hydrophobic cavities etched on silicon wafers, which allows us to control their number and position. Hence, the experiment can be used to investigate the interaction among bubbles growing in close proximity when the main mass transfer mechanism is diffusion and there is a limited availability of the dissolved species.Item Highly focused supersonic microjets(Physical Review X, 7/9/2012) Tagawa, Yoshikuyi; Oudalov, Nikolai; Visser, Claas Willem; Peters, Ivo R.; van der Meer, Devaraj; Sun, Chao; Prosperetti, Andrea; Lohse, DetlefThis paper describes the production of thin, focused microjets with velocities of up to 850 m/s by the rapid vaporization of a small mass of liquid in an open liquid-filled capillary. The vaporization is caused by the absorption of a low-energy laser pulse. A likely explanation of the observed phenomenon is based on the impingement of the shock wave caused by the nearly instantaneous vaporization on the free surface of the liquid. We conduct an experimental study of the dependence of the jet velocity on several parameters and develop a semiempirical relation for its prediction. The coherence of the jets and their high velocity, good reproducibility, and controllability are unique features of the system. A possible application is to development of needle-free drug-injection systems that would be of great importance for health care worldwide.Item Highly focused supersonic microjets: numerical simulations(Journal of Fluid Mechanics, 9/28/2012) Peters, Ivo R.; Tagawa, Yoshikuyi; Oudalov, Nikolai; Sun, Chao; Prosperetti, Andrea; Lohse, Detlef; van der Meer, DevarajBy focusing a laser pulse inside a capillary partially filled with liquid, a vapour bubble is created which emits a pressure wave. This pressure wave travels through the liquid and creates a fast, focused axisymmetric microjet when it is reflected at the meniscus. We numerically investigate the formation of this microjet using axisymmetric boundaryintegral simulations, where we model the pressure wave as a pressure pulse applied on the bubble. We find a good agreement between the simulations and experimental results in terms of the time evolution of the jet and on all parameters that can be compared directly. We present a simple analytical model that accurately predicts the velocity of the jet after the pressure pulse and its maximum velocity.Item Role of Air in Granular Jet Formation(Physical Review Letters, 7/6/2007) Caballero, Gabriel; Bergmann, Raymond; van der Meer, Devaraj; Prosperetti, Andrea; Lohse, DetlefA steel ball impacting on a bed of very loose, fine sand results in a surprisingly vigorous jet which shoots up from the surface of the sand [D. Lohse et al., Phys. Rev. Lett. 93, 198003 (2004)]. When the ambient pressure p is reduced, the jet is found to be less vigorous [R. Royer et al., Nature Phys. 1, 164 (2005)]. In this Letter we show that p also affects the rate of penetration of the ball: Higher pressure increases the rate of penetration, which makes the cavity created by the ball close deeper into the sand bed, where the hydrostatic pressure is stronger, thereby producing a more energetic collapse and jetting. The origin of the deeper penetration under normal ambient pressure is found to lie in the extra sand fluidization caused by the air flow induced by the falling ball.