Fluid Drop Research Articles

Breakup of a leaky dielectric drop in a uniform electric field.

Electrohydrodynamic (EHD) breakup phenomena for a leaky dielectric drop suspended in another immiscible viscous dielectric and subjected to a uniform electric field are examined using the leaky dielectric theory and the explicit forcing lattice Boltzmann method, by taking into account full nonlinear inertia effects. The breakup modes are first computed for varied conductivity of the drop fluid, as the viscosity ratio λ (=μ_{in}/μ_{out}) is momentarily set to unity, that is, for the slightly conducting (R=σ_{in}/σ_{out}<10), moderately conducting (10≤R≤20), and highly conducting (R>20) cases. For slightly conducting drops (R=5) only one breakup mode via two symmetrical necks persists for permittivity ratios 0.05<Q=ɛ_{in}/ɛ_{out}<3.0 and electric capillary number Ca_{E}>Ca_{E,critical} (ratio of electric and surface tension forces), despite significant length-scale variation of mother and daughter drops. At higher Q (for increased drop permittivity) two necks move closer to the bulbous midpart of the extended droplet, which helps enlarge two daughter drops. However, in the case of moderately conducting drops (10≤R≤20) the number of necks increased to four for increased Ca_{E}. Accordingly two pairs of symmetrical daughter drops are created because of recurrent fluctuations of the electrical shear stress and centerline momentum flux. For highly conducting cases of R>20, depending on Ca_{E}, three distinctly elongated droplet states are formed prior to breakup, which results in the onset of three different breakup modes, namely, via formations of lobed ends (Ca_{E}≤0.264), pointed ends (Ca_{E}≤0.68), and nonpointed ends (Ca_{E}>0.83). While being consistent with past measurements, here we precisely characterize the associated breakup mechanisms and physics in terms of the interactive electric pressure, electric shear stress, and hydrodynamic pressure plus velocity gradients. Since the EHD drop breakup is a dynamic process, on an elongated slender drop the activated locally distinct driving forces, i.e., electric pressure at the end regions and tangential electric stress in the midsection, effectively lead to neck formations by virtue of the created high centerline velocity gradient. Accordingly, resulting variations of local extension rate and net mass flux toward drop ends or into intermediate bulbous regions facilitate the multiple-mode drop breakup via the inertia effect, whereas the developed negative curvature around a neck encourages capillary breakup. We also explicitly reveal the effect of the viscosity contrast λ, which particularly influences the breakup characteristics over a broader range of conductivity ratios.

Toward a new method for the design of combined sensible/latent thermal-energy storage using non-dimensional analysis

Placing an encapsulated phase-change material (PCM) on top of a packed bed of sensible filler material is an effective way of reducing the drop in the heat-transfer fluid (HTF) outflow temperature during discharging associated with a sensible thermal-energy storage (TES). So far, the literature lacks guidelines for the design of a combined sensible/latent TES. This study aims at developing a new method for the design of combined TES based on non-dimensional analysis. The method will provide a designer with non-dimensional plots, produced from quasi-steady-state results of simulations with a one-dimensional model, that relate performance parameters to geometrical, thermophysical, and operational parameters of the combined TES. In this paper, a simplified version of the method is demonstrated that allows the selection of a metallic PCM and its amount such that a specified drop in the HTF outflow temperature is attained during discharging, assuming a fixed sensible section of natural rocks and air as HTF. The plots show that the drop in the outflow temperature during discharging is minimized by selecting a PCM with a melting temperature equal to 98% of the HTF inflow temperature during charging. The plots also show that the heat of fusion, provided it exceeds a threshold, has a subordinate effect on the drop in the outflow temperature. Finally, the plots show that a smaller heat of fusion can be compensated with a larger height of the latent section. The method is illustrated with a specific example.

Numerical investigation of heat transfer of nanofluid flow through a microchannel with heat sinks and sinusoidal cavities by using novel nozzle structure

In this study, we analyze laminar flow for f-GNP nanofluid flow in different concentrations of solid nanoparticles. The computational domain of flow field and heat transfer is 3D, and for Re = 50, 100, 300, 700, a new rectangular microchannel design with cavity will be analyzed. The main objective of this study is determining the effect of boundary condition of inlet velocity for two structures in rectangular microchannel. Other goals of this study are investigating the effect of concentration of solid nanoparticles and Reynolds number on parameters including Nusselt number, friction factor and pressure drop and heat fluid performance evaluation criterion in different fluid and geometric parameters. The results of this study show that changing the direction of fluid at inlet and exit section has an important effect on flow field and heat transfer. Also, by adding a component to fluid velocity at inlet and exit sections, the value of heat transfer and friction factor will be increased. Using microchannel design with dimple can also create a good mixing for fluid during motion. Due to the solid walls, the momentum depreciation is greater in case (1), and also this affects the core regions of the fluid flow. In the microchannel, because of changes in the velocity components in different directions during the entrance of flow in microchannel, the mixing of the fluid for different regions and the amount of heat absorption increase. The existence of cavities in the flow path causes secondary flow to increase the temperature of the fluid during movement. In the microchannel case (2), due to direct fluid movement path, the velocity gradients are reduced and this prevents better mixing of the fluid and the heat transfer. Therefore, the distribution of temperature between the fluids is reduced and the layers of fluid close to the microchannel floor will experience higher temperature in comparison with other regions.

Sharpshooters, Leafhoppers, Cicadellidae (Insecta: Hemiptera: Auchenorrhyncha: Cicadellidae)

Sharpshooter is a term commonly used to describe a group of leafhoppers in the family Cicadellidae. There have been several explanations for the use of this term. Riley and Howard (1893) first used 'sharpshooter' to describe the feeding damage of the glassy-winged sharpshooter, Homalodisca coagulata (Say), on cotton. This damage was caused by the piercing-sucking mouthparts of H. coagulata that appeared to be caused by a 'minute bullet.' They also reported 'rapid and forcible ejection of minute drops of fluid' as another explanation for the use of this term. The term sharpshooter is also attributed to the hiding behavior of these insects when alarmed. Disturbed sharpshooters will slip quickly behind branches and stems to avoid predators, an action not unlike the behavior of army sharpshooter riflemen who would hide behind the trunks of trees to avoid detection by the opposition as they passed by their position. This document is EENY-334 , one of a series of Featured Creatures from the Entomology and Nematology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published: October 2004.&#x0D; EENY-334/IN611: Sharpshooters, Leafhoppers, Cicadellidae (Insecta: Hemiptera: Auchenorrhyncha: Cicadellidae) (ufl.edu)

ANALISIS FAKTOR KEJADIAN PHLEBITIS DENGAN SIMULASI MODEL FISIS ALAT TERAPI INTRAVENA

Intravenous therapy through long-term infusion is at risk for complications such as phlebitis. The influence of medical factors with a history of hypertension and mechanical factors based on the location of the position of infusion is the main study of the causes of phlebitis.One of the causes of phlebitis is the flow of intravenous fluids which is not proportional to the volume of infusion fluid. Intravenous Therapy Devices with the aim of assessing the physical phenomena modeling experiments intravenous therapy with the theory of fluid mechanics and prove the existence of linkage patient's blood pressure and height of intravenous fluid drop rate. The research method is experimental with the physical modeling of intravenous therapeutic devices. Physical model of intravenous therapy devices using a manometer to measure the pressure tube as diastolic pressure and variation on fluid infusion used was NaCl 0.9% and Glucose 5%. The results of this research was obtained diastolic pressure below 80 mmHg produced a drop rate of fluid infusion is almost constant with a maximum height of a standard intravena pole 1meter, while at an altitude above the altitude variation of normal use by 90 mmHg diastolic pressure with height variations of 1.1 to 1.3 meters yield drop rate a linear of infusion liquid to height variations. So to prevent turbulence of intravenous fluids (the cause of phlebitis) by increasing the location standard for infusion

Review on Recent Development and Application of Dispersive Liquid-Liquid Micro Extraction

Dispersive liquid-liquid micro extraction (DLLME) has become a very popular environmentally benign sample-preparation technique, due to its simplicity, rapidity of operation and low consumption of solvent and reagent. It has attracted much interest from scientist working in separation science and much improvement has been made since its introduction in 2006. It has been combined with different extraction techniques such as floating organic drop, solid-phase extraction, and supercritical fluid extraction. This seminar has focused on the review on development of dispersive liquid micro extraction (DLLME) and its application in different samples, such as water, soil, food and biological material with different analytical techniques. DOI : 10.7176/CMR/11-3-02 Publication date :March 31st 2019

‘Surprise’ lambs 18 months after sterilisation of a teaser ram

The owner of a flock of a phenotypically distinct sheep breed purchased a ‘sterilised’ teaser ram to mark oestrus ewes for mating with purebred rams. Lambing in the subsequent year...

The influence of difference in the surface properties on the axisymmetric vibrations of an oblate drop in an AC field

The forced oscillations of an incompressible fluid drop in the non-uniform electric field are considered. The external electric field acts as an external force that causes motion of the contact line. In order to describe this contact line motion the modified Hocking boundary condition is applied: the velocity of the contact line is proportional to the deviation of the contact angle and the rate of the fast relaxation processes, whose frequency is proportional to twice the frequency of the electric field. The equilibrium drop has the form of a cylinder bounded by axially parallel solid planes. These plates have different surface (wetting etc.) properties. The solution of the problem is represented as a Fourier series in eigenfunctions of the Laplace operator. The resulting system of heterogeneous equations for unknown amplitudes was solved numerically. The amplitude-frequency characteristics and the evolution of the drop shape are plotted for different values of the problem parameters.

Numerical investigation on the efficient mixing of overbridged split-and-recombine micromixer at low Reynolds number

It is promising to design a novel structured micromixer that can be easily processed but also exhibit high mixing efficiency as well as low pressure drop at a wide range of Reynolds numbers. The overbridged structure was introduced into the planner E-shape micromixers for the first time to construct a novel kind of bridge-street structure micromixer, in order to improve the mixing efficiency in the wide range of Reynolds number. We investigated numerically the mixing performance of six overbridged E-shape split-and-recombine micromixers via solving 3D Navier–Stokes equations and adopting species transfer model. It is indicated that at lower Reynolds number the tilted interface in the overbridged channel increases the interfacial area and improves the mass transfer efficiency, while at higher Reynolds number the overbridged channels tend to induce vortices and promote the convective diffusion. The results show that the optimal overbridged micromixer DBEM-3 has excellent mixing efficiency exceeding 95% in the range of Re = 0.5–100. The optimal structure of overbridged micromixer was studied further with different viscosity ratio and power law fluid. In addition, the pressure drop under various Reynolds number was calculated, and the pressure drop of the power law fluid was represented by Euler number to reflect the magnitude of the momentum loss rate. It is illustrated that DBEM-3 has excellent mixing efficiency in wide Reynolds number for three different fluid systems, which has promising applications in the biochemistry analysis or mixing systems.

Numerical simulation of flow in hydro turbines channel to improve its efficiency by using of Lattice Boltzmann Method

The aim of the present work is to study the influence of channel geometry and its assemble gap on the efficiency improvement of hydro turbine. Raising flowing velocity and the control of the pressure drop of the inlet fluid of hydro turbines are the most important hydrodynamic factors for improving their efficiency. To study these and obtain the best hydrodynamic conditions of conducting channels, channels’ simulations in seven different geometrical shapes and four different assemble gabs (1, 1.25, 1.5 and 2 m) using of Lattice Boltzmann Method (LBM) were carried out. The simulation indicates that using a conducting channel which hydro turbine is installed inside can play a significant role in turbine efficiency. In addition, the type of the channel shape and assemble gap have different effects on the flow parameters such as velocity and pressure drop, and consequently can have different effects on hydro turbine efficiency too. Considering the velocity ratio and the pressure drop, it is possible to select the Airfoil-like channel as the most efficient channel. Moreover, according to the illustrations, the stream in this channel is more stable than the other channels. Likewise, one-meter assemble gap was chosen as the most efficient one than the other ones. Therefore, Airfoil-like channel with one-meter assemble gap was considered as the best channel design for increase efficiency in hydro turbine constructions.

Circular Estimate Method (CEM) - a Simple Method to Estimate Caenorhabditis elegans Culture Densities in Liquid Medium

BackgroundNematodes are used in many different fields of science, including environmental and biomedical research. Counting and/or estimating nematode numbers is required during research. Although being one of the most common procedures, this apparently simple task is a time-consuming process, prone to errors and concerns regarding procedure, reliability, and accuracy. When an estimate is necessary, there is a traditional manual counting procedure that in this study it will be called as “drop method” (DM). This popular method that extrapolates an animal count from a small drop of fluid shows a high coefficient of variation. To solve this problem, the present study used the free-living nematode Caenorhabditis elegans to develop a new estimation procedure that was based on a relationship between area and volume of a larger sample.ResultsThe new method showed a low coefficient of variation and a close relationship between estimated and real counts of the total number of nematodes in large C. elegans suspensions. Reactive oxygen concentration was measured as an example of method application and to allow comparison between methods.ConclusionThe proposed method is accurate, facile and reproducible, requiring simple, inexpensive materials that make it an excellent alternative to the DM manual counting procedure. Although the DM is faster, its estimates are not as accurate or as precise as those of the new proposed method.

Drying-induced stresses before solidification in colloidal dispersions: in situ measurements

We first report an original setup that enables continuous measurements of stresses induced by the drying of confined drops of complex fluids. This setup is mainly based on a precision scale working with an electromagnetic force compensation technique that provides accurate measurements of forces, while allowing simultaneously controlled evaporation rates, in situ microscopic observations, and thus quantitative estimates of normal stresses. We then performed an extensive study of the drying of a charged colloidal dispersion using this setup. Stress measurements clearly show the emergence of large tensile stresses during drying, well-before the solidification stage evidenced by the invasion of the porous colloidal material by air. Combined measurements of solid deformation and concentration profiles (particle tracking, Raman micro-spectroscopy) help us to demonstrate that these stresses are due to the formation of a solid at a low volume fraction, which further undergoes drying-induced shear deformations up to the colloid close-packing, as also supported by large deformation poroelastic modeling. Above all, our results highlight the importance of repulsive colloidal interactions in the build-up of mechanical stresses during drying.

Numerical modelling of destruction of a drop of non-Newtonian fluid in a gas flow

The research presents the numerical modeling findings of the secondary breakup of droplets of coal water slurries containing petrochemicals (CWSP) droplet with the filter cake content of 50 % for different Weber number values. The modeling method of the secondary droplet breakup is based on the VOF method for interface resolution, LES model for describing turbulence, and the technology of adapted dynamic grids. This technology enables the grid to be automatically concentrated in the region of large solution gradients during the calculation. The implementation of such a highly detailed grid allowed resolving secondary droplets with the dimensions down to 15 μm. We established the droplet breakup modes depending on the Weber number ranging from 36 to 342. The structure of the stream behind droplets was studied in detail and the numerical method was tested. The results are in good agreement with the results of known experiments.

The Incompressible Navier‐Stokes Equations in Vacuum

AbstractWe are concerned with the existence and uniqueness issue for the inhomogeneous incompressible Navier‐Stokes equations supplemented with H1 initial velocity and only bounded nonnegative density. In contrast to all the previous works on those topics, we do not require regularity or a positive lower bound for the initial density or compatibility conditions for the initial velocity and still obtain unique solutions. Those solutions are global in the two‐dimensional case for general data, and in the three‐dimensional case if the velocity satisfies a suitable scaling‐invariant smallness condition. As a straightforward application, we provide a complete answer to Lions' question in his 1996 book Mathematical Topics in Fluid Mechanics, vol. 1, Incompressible Models, concerning the evolution of a drop of incompressible viscous fluid in the vacuum. © 2018 Wiley Periodicals, Inc.

Numerical Investigation of Coalescing Filtration Process

AbstractCoalescing filtration is a mechanical process which is employed to remove dispersed aerosol particles from a gas stream. This kind of filtration is a depth‐filtration process and is widely used in process industries to remove particulate matter from exhaust gases or in compressed‐air applications to filter oil particles introduced during the compression process. Fibrous filters are often used due to low costs, high capture efficiency and low pressure drop. The droplets are first captured on the fibers, then coalesce, and eventually drain out. The performance of a filter medium is judged based on its capture efficiency and pressure‐drop characteristics. Estimating these parameters without setting up experimental investigations of each filter medium would be beneficial for choosing optimal filters. In the present study, numerical simulations are used to predict the behavior of a fully‐wetting fibrous filter using an Euler‐Euler formulation in ANSYS CFX. Different theoretical models to predict single fibre capture efficiencies are compared and a novel extrapolation scheme to predict the net capture of oil particles is presented. Pressure‐drop studies are carried out to find the pressure drop of a viscous fluid flowing through an array of fibers. A steady‐state multiphase simulation with the influence of gravity is set up, and the physical relevance of the results is examined.

Hydrodynamics singularities associated with a static or moving three-phase contact line

Stationary flows of viscous fluids with a static or moving contact line are considered. Contact line separates three phases: vapor, liquid and solid. No-slip condition on the solid-fluid surface and ordinary conditions with account constant surface tension for the fluid-vapor interface are supposed to be fulfilled. The flows presented in the report are induced by some physical mechanism concentrated in the very small region near the contact line. Such contact line is the origin of the flow and treated as a hydrodynamics singularity. As an example the flow in a two- dimensional viscous fluid drop which rests or steadily moves along a horizontal solid surface is considered. Motions of this type can be observed in experiments if the solid-fluid surface wettability is non-uniform. A sequence of solutions for the velocity field and the free surface shape with the successively increasing applicability region near the static or moving contact lines is obtained. At first stage the solution of the problem is found in the case when the distortion of the free surface of the drop during motion can be neglected. The problem is then reformulated using functions of a complex variable and expanded variables are introduced. In the new variables a more accurate solution of the same problem is found, with a much more narrow inapplicability region near the contact lines. Asymptotic behavior of the flow near the contact lines is discussed.

438. Finding Toxocara Eggs in Park Soil From Montgomery County, Pennsylvania

Background Toxocara canis (dogs) and Toxocara cati (cats) is a parasitic worm commonly called roundworm. Toxocara eggs are spherical to oblong in shape, have a rough/pitted edge, appear brownish in color, and measures 75–90 µm (T. canis) and 65–70 µm (T. cati). This environmental surveillance study was designed to examine Toxocara contamination levels of selected parks in Montgomery County, Pennsylvania for the first time.MethodsSix soil samples (2 cups each) were obtained from six different parks, for a total of 36 samples. Two table spoons of dried/sifted soil were added to a glass, covered with 1/4 cup of a sugar floatation solution, stirred for 30 seconds, and let sit for 1 hour. The supernatant was transferred to a 20 mL plastic tube, capped, and let sit overnight. Three drops of surface fluid were placed on a glass slide and examined at ×400 total magnification. The number of Toxocara eggs from a full grid search of the cover slip area was recorded.ResultsOverall, 35 of 36 samples tested positive for Toxocara eggs. The parks and samples varied in their levels of contamination of Toxocara eggs; smallest samples (0 and 2 eggs) from Sanatoga Park and largest samples from Pottstown Memorial Park [52 eggs – picnic pavilion] and Heather Place Park [56 eggs – tree grove]. The average number of eggs from Sanatoga Park (2.5 eggs [95% CI: 1.0, 4.0]), Gerald Richards Park (4.0 eggs [95% CI: 3.8, 6.2]), and Althouse Arboretum (4.7 eggs [95% CI: 3.3, 6.1]) were significantly lower than Manderach Park (11.7 eggs [95% CI: 9.6, 13.8]). Sanatoga, Gerald Richards, and Heather Place had similar average number of eggs (χ2 = 3.97 < 5.99). Pottstown Memorial Park (18.2 eggs [95% CI: 4.1, 32.1]) and Heather Place Park (18.5 eggs [95% CI: 3.5, 23.5]) had the highest averages; both parks had very similar average number of eggs (χ2 = 0.02 < 3.84).ConclusionThis study demonstrated that Toxocara eggs could be found in every park that was tested. The number of eggs per sampled varied greatly; highest amounts in areas that could contain food droppings (e.g., picnic area) or potential bathrooms for dogs (e.g., tree grove). Some parks were significantly less infected with an average number of Toxocara eggs than other parks.Disclosures All authors: No reported disclosures.

Quantifying the force between mercury and mica across an ionic liquid using white light interferometry

HypothesisUnder axisymmetric conditions, changes in the thickness of the thin film between a fluid drop and a solid revealed by white light interferometry can provide information about the interaction of the bodies. Thus, in principle one can quantify the force between the surfaces using interferometric information of film thickness profile. This is needed to quantify and analyze drop-solid interactions across complex fluids such as an ionic liquid to independently characterize new surface forces. ExperimentsInterferometric fringes were obtained in experiments on the interaction between a mercury drop and mica across a film of room temperature ionic liquid. The data is analyzed using a novel formula giving the total force acting on the drop. The calculations are compared with two other approaches to estimating forces. Qualitative and quantitative differences are discussed. FindingsThis is the first report of forces measured between mercury and mica across an ionic liquid. The system is subjected to different applied electric potentials. In each case a long ranged, exponentially decaying repulsive force is found. At small separations, the system becomes unstable and the surfaces jump into contact. The comparison of force calculation methods demonstrates the superiority of the force approach proposed here.

Measuring Bone Biomarker Alkaline Phosphatase with Wafer-Scale Nanowell Array Electrodes.

Biosensors that can analyze a single drop of biological fluid can overcome limitations such as extraction volume from humans or animals, ethical problems, time, and cost. In this work, we have developed a highly sensitive electrochemical (EC) biosensor based on a nanowell array (NWA) for the detection of alkaline phosphatase (ALP), a serum indicator of bone formation. The size of the electrode is 2 × 1 mm2 and has over 10 million nanowells (400 nm diameter) arranged uniformly on the electrode surface. For detecting ALP, anti-ALP was immobilized and oriented on the NWA surface using a self-assembled monolayer and protein G. EC impedance spectroscopy (EIS) was used to determine the amount of ALP in 10 μL of sample. The impedance was calibrated with ALP concentration. The NWA has a linear dynamic range from 1 pg/mL to 100 ng/mL with a limit of detection (LOD) at 12 pg/mL. We used the sensor to measure the ALP in real mouse serum from 4, 10, and 20 weeks old mice and compared the results to the standard photometric assay. This work demonstrates the potential of EC NWA sensors to analyze a single drop of a real body fluid sample and to be developed for broad applications.

Comparative Investigations on Wettability of Typical Marine, Continental, and Transitional Shales in the Middle Yangtze Platform (China)

Wettability is a physico-chemical rock property that plays a crucial role in the efficient development of shale gas and oil. However, a precise characterization of wettability for shale reservoirs is still a challenging task because of their complex pore structure (with a large proportion of pores in nm scale) and shale composition (variable at μm scale). In this work, we conducted the fluid drop wettability test, air–liquid contact angle measurement, and spontaneous imbibition (SI) with two fluids [deionized (DI) water and n-decane (an oil phase)] to evaluate the wettability of typical organic-rich shales (marine Longmaxi, continental Dongyuemiao, and transitional Dalong and Longtan shales), as influenced by total organic carbon (TOC), thermal maturity, mineral composition, effective porosity, and pore size distribution. Marine Longmaxi shales have strong or moderately strong water-wet properties with measured DI water contact angles of 3.4°–16.5°. In contrast, continental Dongyuemiao and transitional Da...