Fluid triboelectrification, also known as flow electrification, remains an under-explored yet ubiquitous phenomenon with potential applications from material science to planetary evolution. Building upon previous efforts to position water within the triboelectric series, we investigate the charge on individual, millimetric water drops falling through air. Our experiments measured the charge and mass of each drop using a Faraday cup mounted on a mass balance, and connected to an electrometer. For pure water in a glass syringe with a grounded metal tip, we find the charge per drop ($Δq/Δm$) was approximately -5 pC/g to -1 pC/g. This was independent of the release height of the drop, tip diameter and length, tip cleaning preparation, and whether the experiment was shielded with a Faraday cage. Biasing the tip to different voltages allowed for linear control of the drop charge, and the results were consistent with known electrochemical effects, namely the Volta potential expected between most metals and bulk water ($\approx$ -0.5 V). Introducing insulating plastic materials into the experiment (from the syringe body or tip) imparted large amounts of charge on the drops with systematic
Vertical forcing of partially filled tanks can induce parametric sloshing. Under non-isothermal conditions, the resulting mixing can disrupt the thermal stratification between liquid and vapor, leading to enhanced heat and mass transfer and large pressure fluctuations. This work presents an experimental investigation of sloshing-induced heat and mass transfer in a horizontally oriented cylindrical tank under vertical harmonic excitation. This configuration is particularly relevant for cryogenic fuel storage in aircraft and ground transportation, yet its thermodynamic response under parametric sloshing remains largely uncharacterized. The present study provides the first experimental characterization of the sloshing-induced pressure drop and associated heat and mass transfer in this geometry. Decoupled isothermal and non-isothermal experimental campaigns are carried out across multiple fill levels and forcing amplitudes, near resonance of the first longitudinal symmetric mode $(2,0)$, using a hydrofluoroether fluid (3M Novec HFE-7000). To quantify heat and mass transfer, a lumped thermodynamic model is combined with an Augmented-state Extended Kalman Filter (AEKF), enabling real-tim
We investigate the interactions between two drops in a heated environment and analyze the effect of evaporation on bouncing, coalescence and reflexive separation phenomena. A reliable mass transfer model is incorporated in a coupled level-set and volume-of-fluid framework to accurately model the evaporation process and the evolution of drop interfaces during the interactions. The numerical technique is extensively validated against the benchmark problems involving the evaporation of a single drop. We analyze the contour plots of temperature and vapor mass fraction fields for each collision outcome. Our numerical simulations reveal that vapor entrapment during the separation process, with high-velocity vapor manages to escape. Increasing evaporation rates result in slower post-collision drop separation. Furthermore, the differences in kinetic energy and surface energy are analyzed for different Stefan numbers. The coalescence of drops exhibits energy oscillations until dissipation, while the bouncing and reflexive separations lack such oscillations. In the reflexive separation regime, the kinetic energy of the drops becomes zero after detachment.
We use an integral analysis of conservation equations of mass and energy, to determine the drop size and distributions during shock-induced drop break-up. The result is an updated form for the drop size as a function of its final velocity, from a series of work applied to various atomization geometries. Comparisons with experimental data demonstrate the validity and utility of this method. The shock-induced drop size and distributions can be predicted within reasonable accuracy as a function of the drop velocity ratio and fluid properties. The result also illustrates the dynamical process of kinetic energy deficit transferred to the surface tension energy, and the skewing of the drop size distribution due to the non-linear dependence on velocity ratio.
One of the greatest challenges in quantum chromodynamics is understanding the hadronization mechanism, which is also crucial for carrying out precision physics with jet substructure. In this Letter, we combine recent advancements in our understanding of the field theory-based nonperturbative structure of the soft drop jet mass with precise perturbative calculations of its multi-differential variants at next-to-next-to-leading logarithmic (NNLL) accuracy. This enables a systematic study of its hadronization power corrections in a completely model-independent way. We calibrate and test hadronization models and their interplay with parton showers by comparing our universality predictions with various event generators for quark and gluon initiated jets in both lepton-lepton and hadron-hadron collisions. We find that hadronization models perform better for quark jets relative to gluon jets. Our results provide the necessary toolkit for precision studies with the soft drop jet mass motivating future analyses using real world collider data. The nontrivial constraints derived in our framework are useful for improving the modeling of hadronization and its interface with parton showers in ne
In this article, we construct a novel one-dimensional model of drop ejection from a micro-size nozzle due to a short pressure pulse applied to the liquid in the nozzle. The pressure pulse supplies the kinetic energy to the perturbed liquid-bulge squeezed from the nozzle, which then ballistically lengthens forming a ligament. The Plateau-Rayleigh instability forms a neck in the ligament at the nozzle, leading to detachment of the ligament from the nozzle, which then collapses in a drop. This drop formation sequence is typical for drop-on-demand printheads in which the drop is ejected from the nozzle by a short pressure pulse at the needed moment of time when it should reach the substrate. The model calculates the velocity of the droplet, length of the ligament vs. time, and the time when the ligament detaches from the nozzle as a function of the exit radius of the nozzle, the volume of the droplet, the time that the volume of the droplet is squeezed from the nozzle, viscosity, surface tension, and mass density of the liquid drop. The model also calculates a criterion for drop ejection from the nozzle.
The evaporation of a liquid drop of initial diameter (Ddrop) migrating in a tube of diameter (D0) is investigated using the coupled level set and volume of fluid (CLSVOF) method focusing on determining the heat and mass transfer coefficients for a deforming drop. A robust phase change model is developed using an embedded boundary method under a finite difference framework to handle vaporizing flows. The model is extensively validated through simulations of benchmark problems such as arbitrary evaporation of a static drop and reproduction of psychrometric data. The results show that the Sherwood number (Sh) and the Nusselt number (Nu) reach a steady value after an initial transient period for the drop subjected to Hagen-Poiseuille flow. A parametric study is conducted to investigate the effect of drop deformation on the rate of evaporation. It is observed that Stefan flow due to evaporation has a negligible impact on the drop deformation dynamics. We also observed that, for different values of Ddrop/D0, the Sh follows a linear correlation with Re^{1/2}Sc^{1/3}.
We compute the soft-drop jet-mass distribution from $pp$ collisions to NNLL accuracy while including nonperturbative corrections through a field-theory based formalism. Using these calculations, we assess the theoretical uncertainties on an $α_s$ precision measurement due to higher order perturbative effects, nonperturbative corrections, and PDF uncertainty. We identify which soft-drop parameters are well-suited for measuring $α_s$, and find that higher-logarithmic resummation has a qualitatively important effect on the shape of the jet-mass distribution. We find that quark jets and gluon jets have similar sensitivity to $α_s$, and emphasize that experimentally distinguishing quark and gluon jets is not required for an $α_s$ measurement. We conclude that measuring $α_s$ to the 10% level is feasible now, and with improvements in theory a 5% level measurement is possible. Getting down to the 1% level to be competitive with other state-of-the-art measurements will be challenging.
Breaking surface waves generate drops of a broad range of sizes that have a significant influence on regional and global climates, as well as the identification of ship movements. Characterizing these phenomena requires a fundamental understanding of the underlying mechanisms behind drop production. The interscale nature of these mechanisms also influences the development of models that enable cost-effective computation of large-scale waves. Interscale locality implies the universality of small scales and the suitability of generic subgrid-scale (SGS) models, while interscale nonlocality points to the potential dependence of the small scales on larger-scale geometry configurations and the corresponding need for tailored SGS models instead. A recently developed analysis toolkit combining theoretical population balance models, multiphase numerical simulations, and structure-tracking algorithms is used to probe the nature of drop production and its corresponding interscale mass-transfer characteristics above the surface of breaking waves. The results from the application of this toolkit suggest that while drop breakup is a somewhat scale-nonlocal process, its interscale transfer signa
We present measurements of black hole masses and Eddington ratios for a sample of 38 bright (M$_{1450}$ < -24.4 mag) quasars at 5.8 < z < 7.5, derived from VLT/X-shooter near-IR spectroscopy of their broad CIV and MgII emission lines. The black hole masses (on average M$_{BH}$ ~ 4.6 x 10$^9$ M$_{\odot}$) and accretion rates (with Eddington ratios ranging between 0.1 and 1.0) are broadly consistent with that of similarly luminous 0.3 < z < 2.3 quasars, but there is evidence for a mild increase in the median Eddington ratio going towards z > 6. Combined with deep ALMA observations of the [CII] 158 $μ$m line from the quasar host galaxies and VLT/MUSE investigations of the extended Ly$α$ halos, this study provides fundamental clues to models of the formation and growth of the first massive galaxies and black holes. Compared to local scaling relations, z > 5.7 black holes appear to be over-massive with respect to their host galaxies, and their accretion properties do not change with host galaxy morphology. Under the assumption that the kinematics of the T ~ 10$^4$ K gas, traced by the extended Ly$α$ halos, are dominated by the gravitational potential of the dark mat
Small mass uniqueness in the anisotropic atomic liquid drop model for all values of the parameters is obtained and the critical mass conjecture is investigated.
Tests of the universality of free fall and the weak equivalence principle probe the foundations of General Relativity. Evidence of a violation may lead to the discovery of a new force. The best torsion balance experiments have ruled it out to 10^-13. Cold-atom drop tests have reached 10^-7 and promise to do 7 to 10 orders of magnitude better, on the ground or in space. They are limited by the random shot noise, which depends on the number N of atoms in the clouds. As mass-dropping experiments in the non-uniform gravitational field of Earth, they are sensitive to the initial conditions. Random accelerations due to initial condition errors of the clouds are designed to be at the same level as shot noise, so that they can be reduced with the number of drops along with it. This sets the requirements for the initial position and velocity spreads of the clouds with given N. In the STE-QUEST space mission proposal aiming at 2x10^-15 they must be about a factor 8 above Heisenberg's principle limit, and the integration time required to reduce both errors is 3 years, with a mission duration of 5 years. Instead, offset errors at release between different atom clouds are systematic and give ri
'A basic and basically unsolved problem in fluid dynamics is to determine the evolution of rising bubbles and falling drops of one miscible liquid in another' [1]. Here, we address this important literature gap and present the first theory predicting the velocity, volume and composition of such drops at low Reynolds numbers. For the case where the diffusion out of the drop is negligible, we obtain a universal scaling law. For the more general case where diffusion occurs into and out of the drop, the full dynamics is governed by a parameter-free first-order ordinary differential equation, whose closed form solution exists, and only depends on the initial condition. Our analysis depends primarily on 'drop-scale' effective parameters for the diffusivity through the interfacial boundary layer. We validate our results against experimental data for water drops suspended in syrup, corresponding to certain regimes of the mass exchange ratio between water and syrup, and by this explicitly identify the drop-scale parameters of the theory. [1] Joseph, D.D. and Renardy, Y.Y., 2013. Fundamentals of two-fluid dynamics: part II: lubricated transport, drops and miscible liquids (Vol. 4). Springer
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Scientists have uncovered a surprising connection between quantum gravity and an exotic quantum state of matter that could explain why the universe isn’t expanding wildly fast。 The study suggests that the very shape of space-time may protect the cosmological constant from disruptive quantum effects
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Using the Keck Observatory, astronomers measured the spins of dozens of giant planets and brown dwarfs orbiting distant stars。 They found that giant planets can spin faster than much more massive brown dwarfs, challenging simple assumptions about mass and rotation。 The results suggest that magnetic fields and formation processes play a major role i
NASA’s Lucy spacecraft discovered that asteroid Donaldjohanson is a wobbling, peanut-shaped relic born from a violent collision and slowly reshaped by the subtle force of sunlight。 It also carries traces of ancient water, making it an important clue to the solar system’s mysterious past
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