Constant Liquid Volume Research Articles

Analysis of the interfacial evolution characteristics of hollow droplet impact on a liquid pool

The impact dynamics of a hollow droplet on a liquid pool have significant implications across various industrial applications. This study employs numerical simulations to explore the dynamic evolution of the interface during the impact of a hollow droplet on a liquid pool. The investigation focuses on the effects of varying the hollow ratio Dr and liquid pool depth h* while maintaining a constant volume of liquid within the droplet shell. The findings reveal that both the hollow ratio Dr and pool depth h* critically influence the formation of ejecta + lamella, and vortex rings after the impact of a hollow droplet on a liquid pool. The confinement effect of the pool bottom can influence the evolution of the splashing, while the internal air in the hollow droplet can absorb a part of the impact energy during the collision. Specifically, at shallow pool depths, the interface primarily evolves into ejecta + lamella structures, whereas at greater pool depths, vortex ring formation is predominant. Furthermore, an increase in the hollow ratio leads to a reduction in the critical pool depth hc* at which the transition between these interfacial modes occurs. These findings indicate that, in practical applications involving the impact of hollow droplets on liquid pools, sufficient attention should be given to the pool depth. This enhances our understanding of the bottom pressure, droplet impact, and vortex formation, which is of significant relevance to related industrial technologies.

Charge-controlled swelling gradients at 200-µm resolution in an open-porous polymeric structure for compliance modulation

Plants combine active and passive liquid-mediated mechanisms across broad spatial and temporal scales, inspiring technological developments, in particular involving variable stiffness. Swelling is of particular interest due to the abundance of plant models and applicable (bio)materials, yet existing control by environmental humidity sorption limits its applications. This work combined swellable polymeric structures with electroactive control: we considered an open-porous polymeric laminate that hosted an electrokinetic medium also co-acting as a swelling agent for the same polymer. A constant volume of liquid (an electrolytic solution) was electrokinetically pumped between the symmetrical laminate’s interior and surface layers: as the second moment of inertia increases from the centre to the surface, the pumping of liquid towards the surface decreases the laminate’s bending stiffness, and vice versa. Ion electrosorption on high-specific-surface-area carbon electrodes, deposited in three layers in the laminate by simple additive spraying, facilitated the ion current necessary for the electrokinetic pumping. Flexural rigidity of the 400 µm thick laminate varied by 7% in response to 2-V input, evidencing swelling gradients forming at half-laminate (i.e., 200-µm) resolution. Charge-driven local rearrangement of liquid allows for broader adoption of bioinspired (and biological) porous architectures, where the channels are defined collectively, not individually as in, e.g., soft lithography. Sub-mm resolution and low-voltage control of liquid offer a high level of integration at minimal assembly, positioning active swelling as a promising solution for wearable and bioinspired soft robotic applications.

Mid-infrared spectroscopy of liquids by using a modified button sample holder

A new approach for mid-infrared spectroscopy measurements of liquids is described. Thin layers of liquid samples are analyzed by using a modified button sample holder that incorporates a reservoir. To obtain spectra, buttons containing liquid samples are placed at the infrared beam focus of a praying mantis diffuse reflection optical system. Infrared radiation absorption path lengths can be adjusted by changing the quantity of liquid added to the reservoir. Thin film transflection spectra are similar to those obtained by transmission measurements. Transflection spectra of thicker layer liquids also resemble transmission measurements, but with increased relative intensities for low absorptivity peaks. Unlike transmission measurements, transflection spectra retain overlapping peak profiles for highly absorbing vibration bands due to multiple path length dynamic range effects. For a fixed effective path length (i.e. constant liquid volume), linear calibration plots of absorbance or integrated absorbance versus concentration are obtained. The button sample holder provides a methodology that is complementary to the transmission cell and attenuated total reflection (ATR) techniques for infrared analyses of neat solids and liquids, and is especially useful for characterizing thick samples and high absorptivity bands.

A Microfluidic Hanging-Drop-Based Islet Perifusion System for Studying Glucose-Stimulated Insulin Secretion From Multiple Individual Pancreatic Islets.

Islet perifusion systems can be used to monitor the highly dynamic insulin release of pancreatic islets in glucose-stimulated insulin secretion (GSIS) assays. Here, we present a new generation of the microfluidic hanging-drop-based islet perifusion platform that was developed to study the alterations in insulin secretion dynamics from single pancreatic islet microtissues at high temporal resolution. The platform was completely redesigned to increase experimental throughput and to reduce operational complexity. The experimental throughput was increased fourfold by implementing a network of interconnected hanging drops, which allows for performing GSIS assays with four individual islet microtissues in parallel with a sampling interval of 30 s. We introduced a self-regulating drop-height mechanism that enables continuous flow and maintains a constant liquid volume in the chip, which enables simple and robust operation. Upon glucose stimulation, reproducible biphasic insulin release was simultaneously observed from all islets in the system. The measured insulin concentrations showed low sample-to-sample variation as a consequence of precise liquid handling with stable drop volumes, equal flow rates in the channels, and accurately controlled sampling volumes in all four drops. The presented device will be a valuable tool in islet and diabetes research for studying dynamic insulin secretion from individual pancreatic islets.

High Pressure Vertical Axis Wind Pump

Abstract A novel positive displacement, high pressure, vertical axis wind pump (HP-VAWP) was evaluated for the application of stand-alone high-pressure reverse-osmosis desalination and drip irrigation systems. The direct interface between a vertical axis wind turbine (VAWT) and a positive displacement pump that delivers a constant liquid volume per revolution has never been studied before. Understanding the interaction between turbine and pump efficiencies, where delivery pressure is determined by back-pressure alone, is critical for efficient design. Wind tunnel experiments were conducted on a small-scale two-bladed turbine (0.4 m2 cross-sectional area) that operated on a dynamic stall principle. At these small laboratory scales, the turbine and pump peak efficiencies were relatively low (15% and 28%, respectively); nevertheless, the system produced nearly constant pressures in excess of 1.5 bar for a broad operational range. Moreover, the system exhibited a basic self-priming capability, and the turbine could easily be braked by overloading the pump. A conservative field-scale analysis of an HP-VAWP system indicated that a medium-size turbine (12.5 m2 cross-sectional area) could attain a peak efficiency of 12.9%. Realistic efficiencies greater than 20% are attainable, significantly exceeding the 4%–8% typical peak efficiency of the widely used American multibladed wind pumps. Indeed, our research indicates that an HP-VAWP system is viable and requires further development. The benefits of zero carbon emissions during operation, high relative efficiency, and easy manufacturing and maintenance render the HP-VAWP ideal for stand-alone or off-grid environments.

Coalescence dynamics of a compound drop on a deep liquid pool

The partial coalescence dynamics of a compound drop in a liquid pool is numerically investigated. We study the effect of the ratio of the inner to outer radii$(R_{r})$of the compound drop while maintaining a constant liquid volume in the outer shell of the compound droplet. It is observed that for small values of the radius ratio, the coalescence dynamics is similar to that of a ‘simple’ drop, but the partial coalescence is suppressed for large values of$R_{r}$. Increasing the value of$R_{r}$decreases the distance migrated by the inner bubble in the downward direction inside the pool. The location of the bubble after coalescence is found to play an important role in the pinch-off process of the satellite drop. The influence of the governing dimensionless parameters on the coalescence dynamics has also been investigated.

An automated system for performing continuous viscosity versus temperature measurements of fluids using an Ostwald viscometer

An automated system was developed to measure the viscosity of fluids as a function of temperature using image analysis tracking software. An Ostwald viscometer was placed in a three-wall dewar in which ethylene glycol was circulated using a thermal bath. The system collected continuous measurements during both heating and cooling cycles exhibiting no hysteresis. The use of video tracking analysis software greatly reduced the measurement errors associated with measuring the time required for the meniscus to pass through the markings on the viscometer. The stability of the system was assessed by performing 38 consecutive measurements of water at 42.50 ± 0.05 °C giving an average flow time of 87.7 ± 0.3 s. A device was also implemented to repeatedly deliver a constant volume of liquid of 11.00 ± 0.03 ml leading to an average error in the viscosity of 0.04%. As an application, the system was used to measure the viscosity of two Li-ion battery electrolyte solvents from approximately 10 to 40 °C with results showing excellent agreement with viscosity values calculated using Gering's Advanced Electrolyte Model (AEM).

Normal and oblique impacts between smooth spheres and liquid layers: Liquid bridge and restitution coefficient

Detailed understanding of individual collision mechanics of particles in the presence of liquid is crucial for modeling wet particle flows that are omnipresent in nature and various industries. Our early work (Ma et al., 2013) preliminarily characterized the oblique impacts between rough-surface sphere and liquid layers with wide-ranging impact parameters by means of restitution coefficients. The current paper deepens the early work by performing both normal and oblique impacts between smooth-surface collision bodies, focusing on the collision details such as liquid bridge configuration, liquid layer morphology as well as the restitution coefficients with the aid of improved experimental setup. Different from static liquid bridge or the dynamic bridge with constant liquid volume, the formation and development of impact-induced liquid bridge is greatly influenced by the inertia of surrounding liquid that could be represented by liquid Reynolds number. Moreover, liquid inertia is also found to affect the total kinetic energy reduction of spheres through changing the layer morphology, thus having to be considered during theoretical modeling. Liquid bridge force contributes a lot to the energy reduction of rebounding sphere in the normal direction, while has little effects in the tangential direction. For the oblique impacts of smooth spheres with thin liquid layers, no matter how viscous the liquid is, the tangential restitution coefficients are always maintained at higher values than dry impact for the lubrication effect exerted by liquid. The effect gradually weakens as the layer thickness increases. The lubrication effect is not observed for rough-surface impacts owing to the additional energy reduction caused by the physical interaction between surface asperities. Due to the significant role of layer thickness in the energy dissipation process, the liquid drag force arising during the impacts with considerable thickness has to be considered in the development of theoretical models for restitution coefficients.

Surface acoustic wave based pumping in a microchannel

Pumping and manipulation of liquids in microfluidic channels are important for many mechanical, chemical and biomedical applications. Surface acoustic wave based devices fabricated on high-efficiency piezoelectric substrates have been recently investigated for mixing and separation application within microfluidic channels. In this paper, we introduce a novel integrated surface acoustic wave based pump for liquid delivery and precise manipulation within a microchannel. The device employs a hydrophobic surface coating (Cytop) in the device design to decrease the friction force and increase the bonding. Contrary to previous surface acoustic wave based pumps which were mostly based on the filling and sucking process, we demonstrate long distance media delivery (up to 8 mm) and high pumping velocity increasing the device's application space and mass production potential. Additionally, the device design does not need precise layers of water and glass between substrate and channel, simplifying the design significantly. In this study, we conducted extensive parametric studies to quantify the effects of the liquid volume pumped, microchannel size, input applied power as well as the existence of hydrophobic surface coating on the pumping velocity and pump performance. Our results indicate that the pumping velocity for a constant liquid volume with the same applied input power can be increased by over 130 % (2.31 vs 0.99 mm/min) by employing a hydrophobic surface coating (Cytop) in a thinner microchannel (250 vs 500 µm) design. This device can be used in circulation, dosing, metering and drug delivery applications which necessitates small-scale precise liquid control and delivery.

A quantitative interpretation of recent experimental results on stable carbon isotope fractionation by aerobic CH 4-oxidizing bacteria

A quantitative model of recent laboratory experiments on carbon isotope fractionation by methane-oxidizing bacteria is proposed. The simulated experimental apparatus consists of a bacterial culture with a constant liquid volume, a gas headspace and a methane bubbling mechanism. The relative effects of bacterial growth and transport phenomena that do not depend on cell density are clarified. In all calculations, gas–liquid mass transfer is defined by unconstrained model parameters. Limited mass transfer from the culture into the headspace, rather than the incomplete dissolution of substrate-rich bubbles, seems to have caused an apparent decrease in the measured carbon isotope fractionation. The experimenters attributed this fractionation shift to a growing imbalance among kinetic rates as methane consumption by bacteria increases. Model predictions support this interpretation but also show that changes in carbon isotope fractionation in the course of the experiments cannot be unambiguously correlated with bacterial cell density unless gas–liquid mass transfer parameters are calibrated. Simulations of other laboratory experiments indicate that a reported change in carbon isotope fractionation could, in part at least, be the result of experimental conditions rather than the emergence of a different methane oxidation pathway postulated by the experimenters. A careful evaluation of mass transfer from the liquid culture into the gas headspace is warranted in this type of experiments since isotope fractionation factors are likely to be used in a wide variety of environmental contexts.

Numerical simulation of the filling phase in the polymer injection moulding process with a conservative level set method

Numerical simulations are widely used in polymer processing in order to understand the interaction between the material properties and the process. In the injection moulding process, one of the numerical simulation problems encountered is the tracking of the polymer-air front or interface during the filling stage [1]. In this study, this is achieved by using the classical level set method, which reveals to be conservative. On the contrary, in the case of confined volume of two phases flow, such as an air bubble moving in a constant volume of liquid, the method needs a correction in order to be conservative [2-3]. For a non-Newtonian non-isothermal flow, the simulation involves a coupling between heat transfer, continuity and momentum equations and the rheological material parameters. A finite element method is used to solve this equations set. The results show clearly the expected fountain flow effect. Temperature, velocity, pressure and viscosity fields are calculated and the influence of the thermal contact resistance between the polymer and the mould is presented.

Stability criteria, atomization and non-thermal processes in liquids

Analyzing the first equation in the BBGKY chain of equations for an equilibrium liquid–gas system, we derived the analytical expression for the atom work function from liquid into gas. The coupling between the atom work function from liquid into vacuum and the stability criterion of liquid in limiting points of the first type was shown (using I.Z. Fisher classification). As it turned out, Fisher’s criterion corresponds to the condition of atomization. We have expressed the state equation in terms of the atom work function from liquid into vacuum and performed calculations of the limiting line of stability composed of limiting points of the first type for argon. Our model discovers an interesting effect of the negative atom work function: at a constant volume of liquid, on a temperature rise (also at a fixed temperature and decreasing specific volume of liquid) the atom work function drops and takes a negative value with a modulus that is significantly larger than the atomic thermal energy. We propose a new two-stage mechanism of sonoluminescence based on non-thermal processes in liquid in a state with a negative atom work function. The first stage includes the emission of atoms from the interior of the bubble into gas at hyper-thermal velocities. At the second stage, a collision of emitted flow takes place between the gas atoms along with the implosion of the central part of the bubble. As a result of the impact excitation, ionization and the subsequent recombination, a flash of electromagnetic radiation develops that can be seen in sonoluminescence experiments.

Development of Small Ultrasonic Reactor for On-Site Treatment of Wastewater Including Chlorinated Hydrocarbon

Tetrachloroethylene (PCE) aqueous solution was used as the sample to be decomposed, and the effects of ultrasonic conditions (intensity and frequency) and reactor diameter on the PCE decomposition performance were investigated under a constant volume of liquid. The spatial distribution of PCE concentration in the reactor and the decomposition conversion were measured. The liquid mixing time was measured, and the reaction fields were visualized by using sonochemical luminescence.The spatial distribution of PCE concentration was relatively uniform for 100 and 200 kHz, while the PCE concentration was higher at the lower part of the reactor than at the upper part of the reactor for 500 and 800 kHz. Under the present range of ultrasonic frequency (100–800 kHz), the decomposition conversion increased with decreasing frequency. The reactor diameter was found to have an optimum value for the decomposition performance under the constant liquid volume.

Influence of powder/liquid mixing ratio on the performance of a restorative glass-ionomer dental cement

The influence of powder/liquid mixing regime on the performance of a hand-mixed restorative glass-ionomer cement (GIC) was evaluated in terms of compressive strength, working characteristics and the porosity distribution. Mean compressive fracture strengths, standard deviations and associated Weibull moduli ( m) were determined from series of 20 cylindrical specimens (6 mm height, 4 mm diameter) prepared by hand-mixing the relative proportions of the powder and liquid constituents. Working characteristics were assessed using an oscillating rheometer whilst scanning electron microscopy and image analysis were used to investigate the influence of the mixing regime on pore distribution. For a constant volume of liquid (1 ml) the mean compressive strength decreased from 102.1±23.1 MPa for 7.4 g of powder, to 93.8±22.9, 82.6±18.5 and 55.7±17.2 MPa for 6.66, 5.94 and 3.7 g of powder, respectively. A concomitant increase in both the working and setting times was also observed. GICs manipulated to a powder/liquid mixing consistency below the manufacturers’ recommend ratio, for a constant volume of liquid, resulted in reduced porosity levels in the cement mass and extended working and setting times. Unfortunately, a reduction in the concentration of reinforcing glass particles in the set material below that specified by the manufacturers decreases the cements’ load bearing capacity so that they fail at lower compressive stress levels in the posterior region of the mouth.

Theory of creeping gravity currents of a non-Newtonian liquid.

Recently several experiments on creeping gravity currents have been performed, using highly viscous silicone oils and putties. The interpretation of the experiments relies on the available theoretical results that were obtained by means of the lubrication approximation with the assumption of a Newtonian rheology. Since very viscous fluids are usually non-Newtonian, an extension of the theory to include non-Newtonian effects is needed. We derive the governing equations for unidirectional and axisymmetric creeping gravity currents of a non-Newtonian liquid with a power-law rheology, generalizing the usual lubrication approximation. The equations differ from those for Newtonian liquids, being nonlinear in the spatial derivative of the thickness of the current. Similarity solutions for currents whose volume varies as a power of time are obtained. For the spread of a constant volume of liquid, analytic solutions are found that are in good agreement with experiment. We also derive solutions of the waiting-time type, as well as those describing steady flows from a constant source to a sink. General traveling-wave solutions are given, and analytic formulas for a simple case are derived. A phase plane formalism that allows the systematic derivation of self-similar solutions is introduced. The application of the Boltzmann transform is briefly discussed. All the self-similar solutions obtained here have their counterparts in Newtonian flows, as should be expected because the power-law rheology involves a single-dimensional parameter as the Newtonian constitutive relation. Thus one finds similarity solutions whenever the analogous Newtonian problem is self-similar, but now the spreading relations are rheology-dependent. In most cases this dependence is weak but leads to significant differences easily detected in experiments. The present results may also be of interest for geophysics since the lithosphere deforms according to an average power-law rheology.

Charge accumulation in an oil tank during loading operations

Charge accumulation and relaxation of kerosene have been investigated in a full-sized, 100 kiloliter test rig during pumping operations. Two different experiments were conducted. First, measurements were made as a constant volume of oil was circulated through the tank via a recirculation loop. The first experiment, while not operationally realistic, permitted a simplified test of the charge relaxation model under a constant liquid volume condition. Electrostatic fields was monitored both during and after filling. Second, measurements were made under the realistic condition of fresh oil being pumped into the tank from another reservoir. From both experiments, it is found that volume-averaged charge density decreases as liquid depth increases; furthermore, the highest surface potential occurs for a fill fraction near 50%. The experimental data compare well with the predictions of a model derived under the assumption of uniform volume charge and simple ohmic relaxation.

Depletion Performance of Gas-Condensate Reservoirs

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Introduction This paper reviews basic methods for evaluating the depletion performance of a well producing a gas-condensate fluid. In particular, we discuss initial gas-in-place estimates, inflow-performance relationships, the development and behavior of liquid saturations over both time and drainage area, and the interpretation of pressure-transient tests. Every aspect of these calculations for depletion of a gas-condensate, or any other essentially two-phase system, is implicitly dictated by the interaction between the fluid properties of the initial gas-in-place and the relative permeability properties of the reservoir rock. The simple steady-state theory forms a useful framework for understanding these interactions and often yields practical approximations for some important quantities. This theory and its relationship to commonly available laboratory measurements form the foundation for many of the methods discussed. Fluid Determination, Properties, and Descriptions Classification of a reservoir fluid as a black oil, volatile oil, gas condensate, wet gas, or dry gas is important because application of appropriate engineering practices to predict reserves and rates traditionally requires this knowledge. Fig. 1 is a schematic of a pressure/temperature (p-T) diagram for a multicomponent hydrocarbon mixture of constant composition. The region inside the envelope formed by the bubblepoint curve, critical point (C), and dewpoint curve is where liquid and vapor exist in equilibrium. Lines of constant liquid volume are shown inside this region. Fluids initially at temperature and pressure Positions I through V would be classified as a black oil, volatile oil, gas condensate, wet gas, and dry gas, respectively. Gas condensates are separated from the other fluid types by two characteristics: the condensation of a liquid phase at reservoir conditions during isothermal depletion and the retrograde (revaporization) nature of this condensation. Retrograde behavior of the condensing liquid phase can be seen by tracing the change in liquid volume along the constant-temperature line beginning at Point M in Fig. 1. After crossing the dewpoint line, the volume of liquid increases to approximately 10%at Point N and then begins to decrease with continued reduction in pressure.

Contact Angles in Constrained Wetting

The equilibrium conditions for two-dimensional (cylindrical) solid−liquid−fluid systems are developed, taking into account the possibility of constraints imposed on the motion of the contact lines. The solid surface is assumed to be rigid, insoluble, and nonreactive, but it may be rough or heterogeneous or both. The liquid may be volatile; therefore, the frequently used assumption of constant liquid volume is eliminated. A distinction is made between intrinsic and actual contact angles, and the main conclusion is that they may be different when constraints are imposed on the motion of the contact lines. However, the shape of the liquid−fluid interface is shown to be independent of such constraints.

Dynamic Movement of Hemicysts Reconstructed from Monolayer Cultures of Rat Thyroid Cells in Isologous Serum.

Time-lapse studies using cine-microscopic observation showed that the hemicysts formed in a culture of rat thyroid cells in a high concentration of isologous serum were found to arise by swelling from the monolayer sheet, gradually increase in size, and then rapidly collapse. The hemicyst volume increased linearly. We speculate that each hemicyst epithelium transport a constant volume of liquid into the hemicyst lumen.

On lava dome growth, with application to the 1979 lava extrusion of the soufrière of St. Vincent

Abstract A theoretical analysis is presented for the spread of a viscous liquid flowing under its own hydrostatic pressure on a horizontal surface in order to model lava dome formation. Two situations are considered in detail: the spreading of a constant volume of liquid and the case where the amount of liquid is continually increased. Experiments with silicone liquids show close agreement with theory. The formation of a basaltic andesite lava extrusion in 1979 on the crater floor of the Soufriere of St. Vincent (West Indies) provided the motivation for and an application of the model. The extrusion reached a diameter of 868 m and a height of 133 m over a period of 150 days. Over the first 90 days the growth relationships were consistent with those predicted by theory. Application of the theory to the Soufriere dome suggests an effective viscosity of 2 X 10 12 poise for the basaltic andesite lava. The large effective viscosity calculated for the lava may be attributed to the dominant influence of a high-viscosity skin which forms at the margins of the flow as it cools. After 70 days, the rate of growth of the extrusion markedly decreased because a substantial collar of rubble accumulated at the flow front. Due to this collar the growth of the extrusion ceased after 150 days. From approximately two weeks after the initiation of the extrusion, the discharge rate of lava decreased approximately linearly with increasing dome height. This observation suggests that the lava ascended under a decreasing hydrostatic driving pressure and that extrusion ceased when the lava column reached hydrostatic equilibrium.